Proceedings Volume 8557

Optical Design and Testing V

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Proceedings Volume 8557

Optical Design and Testing V

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Volume Details

Date Published: 10 December 2012
Contents: 10 Sessions, 78 Papers, 0 Presentations
Conference: Photonics Asia 2012
Volume Number: 8557

Table of Contents

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Table of Contents

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  • Front Matter: Volume 8557
  • Liquid Optics and Micro-Optics -
  • New Testing Technologies
  • Holographic 3D Display and 3D Modeling
  • Laser Beam Propagation -
  • Analysis and Simulation Methods
  • Novel Optical System Design
  • Advanced Sensing and Measurement
  • Advances in Space Optics
  • Poster Session
Front Matter: Volume 8557
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Front Matter: Volume 8557
This PDF file contains the front matter associated with SPIE Proceedings Volume 8557, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
Liquid Optics and Micro-Optics -
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Wafer-level micro-optics: trends in manufacturing, testing, packaging and applications
Reinhard Voelkel, Li Gong, Juergen Rieck, et al.
Micro-optics is an indispensable key enabling technology (KET) for many products and applications today. Probably the most prestigious examples are the diffractive light shaping elements used in high-end DUV lithography steppers. Highly efficient refractive and diffractive micro-optical elements are used for precise beam and pupil shaping. Micro-optics had a major impact on the reduction of aberrations and diffraction effects in projection lithography, allowing a resolution enhancement from 250 nm to 45 nm within the last decade. Micro-optics also plays a decisive role in medical devices (endoscopes, ophthalmology), in all laser-based devices and fiber communication networks (supercomputer, ROADM), bringing high-speed internet to our homes (FTTH). Even our modern smart phones contain a variety of micro-optical elements. For example, LED flashlight shaping elements, the secondary camera, and ambient light and proximity sensors. Wherever light is involved, micro-optics offers the chance to further miniaturize a device, to improve its performance, or to reduce manufacturing and packaging costs. Wafer-scale micro-optics fabrication is based on technology established by semiconductor industry. Thousands of components are fabricated in parallel on a wafer. We report on the state of the art in wafer-based manufacturing, testing, packaging and present examples and applications for micro-optical components and systems.
Developing interface localized liquid dielectrophoresis for optical applications
Glen McHale, Carl V. Brown, Michael I. Newton, et al.
Electrowetting charges the solid-liquid interface to change the contact area of a droplet of a conducting liquid. It is a powerful technique used to create variable focus liquid lenses, electronic paper and other devices, but it depends upon ions within the liquid. Liquid dielectrophoresis (L-DEP) is a bulk force acting on the dipoles throughout a dielectric liquid and is not normally considered to be a localized effect acting at the interface between the liquid and a solid or other fluid. In this work, we show theoretically how non-uniform electric fields generated by interdigitated electrodes can effectively convert L-DEP into an interface localized form. We show that for droplets of sufficient thickness, the change in the cosine of the contact angle is proportional to the square of the applied voltage and so obeys a similar equation to that for electrowetting – this we call dielectrowetting. However, a major difference to electrowetting is that the strength of the effect is controlled by the electrode spacing and the liquid permittivity rather than the properties of an insulator in a sandwich structure. Experimentally, we show that that this dielectrowetting equation accurately describes the contact angle of a droplet of oil viewed across parallel interdigitated electrodes. Importantly, the induced spreading can be complete, such that contact angle saturation does not occur. We then show that for thin films, L-DEP can shape the liquid-air interface creating a spatially periodic wrinkle and that such a wrinkle can be used to create a voltage programmable phase diffraction grating.
Optical modulation of polarization state based on an etched single mode fiber with azo-polymer overlay
Weiwei Qiu, Xiujie Tian, Qijin Zhang, et al.
A large modulation range of polarization state at 1550nm is achieved by using an etched single mode fiber (SMF) with azo-polymer overlay. With irradiation of polarized light, the photo-reorientation of azo-polymer occurs, causing the birefringence in the fiber. This optically induced birefringence results in the change of polarization state which is continuously recorded on the Poincare sphere, finally makes the state of polarization (SOP) tunable by the irradiation of 365nm polarized light. In our experiment the SOP changes from-handed elliptical polarization to left-handed elliptical polarization and the ellipticity varies from 16.2° to 55.6° during the irradiation. The trajectory of the SOP can also be recovered to the initial polarization state when irradiated by unpolarized light. The experimental results show that the modulation is not only in large range, but also dynamic, reversible.
New Testing Technologies
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Experimental techniques for aberration retrieval with through-focus intensity images
S. F. Pereira, A. Wiegmann, N. Kumar, et al.
Measurement techniques to determine the aberration of an optical system, by obtaining through-focus intensity images that are produced when the object is a point source at infinity, are shown. The analysis of the aberrations is made using the extended version of the Nijboer-Zernike diffraction theory. This theory provides a semi analytical solution of the Debye diffraction integral and thus a direct relation between the intensity distribution of the field at the focal region and the exit pupil of the optical system.
Wave-front aberrations analysis by Zernike polynomials based on the annular sub-aperture stitching system
Lei Duan, Mei Hui, Jiayuan Deng, et al.
Annular sub-aperture stitching method was developed for testing large-aperture aspheric surfaces without using of any compensating element for measurement. It is necessary to correct measurement of aspheric optical aberrations and create mathematical description to describe wave-front aberrations. Zernike polynomials are suitable to describe wave aberration functions and data fitting of experimental measurements for the annular sub-aperture stitching system. This paper uses Zernike polynomials to describe the wave-front aberrations of full wave-front and reconstructed wave-front by annular sub-aperture stitching algorithm. At the same time, the imaging quality of the aspheric optical element can be contrasted. The stitching result shows good agreement with the full aperture result.
Test of diffractive optical element for DUV lithography system using visible laser
Zhonghua Hu, Jing Zhu, Baoxi Yang, et al.
Diffractive optical element (DOE) is used for off-axis illumination extensively in DUV lithographic system. A method for testing the optical performance of DOE using a visible laser is proposed to simplify the test process. In principle, the optical performance of DOE with a visible laser is analyzed with scalar diffraction theory and numerically simulated using MATLAB program. Compared with the DUV condition, the diffractive pattern distribution is enlarged proportionally with a zero-order spike under the visible laser condition. In experiments, the DOE is tested under He-Ne laser. Its far field diffractive pattern is compared and analyzed with the result tested under the working wavelength of 193.368nm. The shape, the opening angle, the azimuth angle and the pole balance coincide with the values tested in DUV condition. The usefulness of method is verified.
High-speed zonal wavefront sensing
High speed wavefront sensing is important in real time profile analysis, analysis of fluid dynamics, ophthalmology and so on. Conventional Shack-Hartmann wavefront sensor uses an array of tiny lenses and a digital camera to record the focal spot array. Thus the frame rate of the sensor depends on the camera. In this paper we present a zonal wavefront sensor where the array of lenses is replaced by an array of gratings followed by a focusing lens. The gratings can be configured to generate just one array of focal spots. This reduction in row of the focal spot array leads to increase in the frame rate of the proposed wavefront sensor.
Holographic 3D Display and 3D Modeling
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3D holographic display with enlarged image using a concave reflecting mirror
We propose a method to enlarge the 3D image in holographic display using a concave reflecting mirror based on the optical reversibility theorem. The holograms are computed using the look-up table (LUT) method, and the common data of the 3D objects are compressed to reduce the memory usage of LUT. Optical experiments are performed and the results show that 3D image can be magnified without any distortion in a shortened image distance, and the memory usage of LUT is reduced. Keywords: computer holography; holographic display; magnification of 3D image size; distortion of the image; compensation of the distortion.
Recent progress on digital holography for 3D display
The hologram is known as the ultimate 3D display because it has all three-dimensional information and the reconstructed image of the hologram provides the natural spatial effect. It has been demonstrated that the laser hologram or the photographical hologram can record and display a 3D image as real as the object is existing there. There have been many researches to realize such realistic 3D images with digital holograms. However, required pixel number for the practical 3D digital hologram is much higher than that for 2D images. Therefore, fast generation of computer-generated hologram (CGH) is quite important. This paper reviews recent progress on CGH, mainly done by the author's group. In addition, output methods such as holographic fringe printers and holographic video displays are also reviewed.
Parallel phase-shifting digital holography system using a high-speed camera
Yasuhiro Awatsuji, Takashi Kakue, Tatsuki Tahara, et al.
A technique of single-shot phase-shifting interferometry called as parallel phase-shifting digital holography is described. This technique records multiple holograms required for phase-shifting digital holography using space-division multiplexing technique. The authors constructed a system based on the parallel phase-shifting digital holography consisting of a Mach–Zehnder interferometer and a high-speed polarization imaging camera. High-speed motion pictures of three-dimensional image and phase image of dynamically moving objects at the rate up to180,000 and 262,500 frames per second were achieved, respectively, for the 128 × 128-pixel images.
Three-dimensional display based on phase modulation
Three-dimensional (3D) display based on phase modulation is presented. The phase distribution to reconstruct 3D objects is obtained by digital holography for real objects and by numerical propagation from computer graphics data for virtual objects. Experimental demonstration using a phase mode spatial light modulator (SLM) with 1,080 x 1,920 pixels is presented. We also presented a method for achieving wide viewing angle using single SLM.
Laser Beam Propagation -
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The behavior of branch points in laser propagation through atmosphere
Xiao-lu Ge, Cheng-yu Fan, Xiao-xing Feng, et al.
Numerical experiments are carried out about the temporal and spatial variation of branch points by four-dimension code of laser propagating in atmosphere. The theory of branch-point detection and phase reconstruction is introduced. The act of branch points' creating and annihilating is emulated when the light wave propagating in atmosphere. The evolvement of branch points in some propagating range with time is emulated, too. The behavior of branch points in the distorted optical field is simulated when the main laser and beacon laser propagate in the atmosphere with opposite direction at the same time. The work could provide a reference for further study of laser propagation through atmosphere and adaptive optics system.
Implementation of controlling the divergence angle utilizing liquid crystal optical phased array
The characteristics of Gaussian beam and the transition function of lens are analyzed in this paper. Based on the principle of liquid crystal optical phased array (LC-OPA) technology, an implementation of controlling the divergence angle of the laser beam is proposed. Through simulation, the transformation graph in which the divergence angle varies with the modulation depth is obtained, and the discretization error is also counted. Experiment have been done to verify the feasibility of this method. This method is convenient and can obtain various value of the angle without changing the structure of the device.
Analysis and Simulation Methods
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Simulation analysis of space remote sensing image quality degradation induced by satellite platform vibration
Feng Yang, Xiaofang Zhang, Yu Huang, et al.
Satellite platform vibration causes the image quality to be degraded, it is necessary to study its influence on image quality. The forms of Satellite platform vibration consist of linear vibration, sinusoidal vibration and random vibration. Based on Matlab & Zemax, the simulation system has been developed for simulating impact caused by satellite platform vibration on image quality. Dynamic Data Exchange is used for the communication between Matlab and Zemax. The data of sinusoidal vibration are produced by sinusoidal curve with specific amplitude and frequency. The data of random vibration are obtained by combining sinusoidal signals with 10Hz, 100Hz and 200Hz’s frequency, 100, 12, 1.9’s amplitude and white noise with zero mean value. Satellite platform vibration data which produced by Matlab are added to the optical system, and its point spread function can be obtained by Zemax. Blurred image can be gained by making the convolution of PSF and the original image. The definition of the original image and the blurred image are evaluated by using average gradient values of image gray. The impact caused by the sine and random vibration of six DOFs on the image quality are respectively simulated. The simulation result reveal that the decenter of X-, Y-, Z- direction and the tilt of Z-direction have a little effect on image quality, while the tilt of X-, Y- direction make image quality seriously degraded. Thus, it can be concluded that correcting the error of satellite platform vibration by FSM is a viable and effective way.
New approach to cost-based tolerancing
The purpose of the tolerancing is the higher yield and the lower cost. This optimization problem seems complicated, if the tolerance parameters are considered to be independent variables. But this optimization problem becomes very simple, if the approximated variances and averages of performance criteria are considered to be independent variables. The procedure will be explained through a practical tolerance problem.
Realization method of full-field point spread function
Point spread function (PSF) defines the intensity of the diffraction image formed by the optical system for a point source. The PSF of an optical system varies with the field of the point source and such variance generally cannot be neglected. This paper proposes a realization method of full-field PSF—incorporating field dependence into the PSF matrix. Two practical optical systems with distinct degree of aberrations are chosen and the PSF using the method proposed with that obtained by direct integration are compared. The result and analysis suggest this method can obtain the PSF in any desired field at a fast speed and with relatively high accuracy.
Thermal control design of a multi-channel scanning imagery radiometer
Shichen Jiang, Bingting Hu, Tao Xu, et al.
The multi channel scanning imagery radiometer is one of the main payloads of a geostationary earth orbit satellite , which can observe multi spectrum from the earth. The radiometer will endure complicated heat flux environment in orbit, and effective thermal design for the instrument is required in order to ensure high quality scanning image. Based on characteristics of the heat flux in geostationary earth orbit and the unique structure of the radiometer, thermal design characteristic was analyzed, and detailed thermal control design was developed based on numerical analysis. The numerical results verified the validity of thermal control design.
Description and implementation studies on field dependent wavefront aberration
Zernike polynomials have been widely used to fit lens surface figure error and the wavefront aberration of optical systems, for its orthogonality in the unit circle and its corresponding relationships with optical aberrations1. Because the current extensively used Zernike polynomials are just functions of the aperture, without consideration of the field factor, it can only represent single field wavefront aberration. This is incomplete for the description of the wavefront aberration, especially for lithographic lens with a large field and high imaging quality2. Thus, considering the field factor in the description of wavefront aberration becomes very necessary. This paper presents a convenient and practical method to describe the full field wavefront aberration. A rotationally symmetric optical system has been taken as an example, in the scope of normalized full field, taking the Chebyshev zero points as nodes, and applying the Chebyshev polynomials to the fitting of Zernike coefficients of different fields. Meanwhile, the influence of the degree of Chebyshev polynomials and the number of fitting nodes on the fitting accuracy is taken into account. The results show that the fitting method used in this paper is of high accuracy, and this fitting method is very significant for the analysis of full field wavefront aberration.
Novel Optical System Design
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Study on optical image stabilizing method based on the technique of deformable mirror
This paper developed the optical image stabilizing (OIS) scheme for an off-axis three-mirror anastigmat. The surface profile of the deformable mirror was designed to correct the image blurring and degradation when there is the relative motion between the imaging optical axis and the object, which is incurred by the movement of the system carrier. In this paper, we proposed a method based on matrix analysis to evaluate deformable mirror parameters and studied on the calculation method of the points on of the deformable mirror to correct the image plane tilt and improve the image performance. Finally, we can achieve OIS quickly and accurately.
Ultra-wide to mid-wide angle 3X zoom and focus adjustable lens design for industrial video endoscope
Optical zoom lens design for industrial video endoscope faces tremendous challenges in stringent compactness requirement in both diameter and rigid length dimensions, as well as harsh environmental requirements such as high working temperature. Industrial video endoscope with optical zoom capability is increasingly demanded by market yet nowadays no such product has been commercialized. Once it succeeds, it will provide huge benefits to customers in improvement of remote visual inspection work quality and productivity. A 3X continuous optical zoom lens design with short focal length is presented in this paper. It is capable to change Field of View from ultra-wide angle as 120degrees to mid-wide angle as 40degrees. Focus distance change is from infinity to as close as 5mm. The whole lens train has a maximum diameter of 3.0mm, and overall length of 8.7mm, which makes it practical to be integrated into a 6mm industrial video endoscope. Image quality in terms of contrast and resolution exceeds today’s existing commercial 6mm industrial video endoscopes. The design has also considered cost and product ruggedness requests.
Designing an all-reflective, long focus and large field of view optical system with freeform surface
Qingfeng Wang, Dewen Cheng, YongTian Wang, et al.
All-reflective optical system has been widely used in the deep space detection applications. We studied the application of freeform surface in all-reflective, off-axis optical systems, which have long effective focal length and large field of view, were designed. The freeform surface was employed to achieve better performance, while reduce the system size and weight. The starting point of the design was calculated by using the geometrical optics and properties of conic. After that we optimized the starting point using the strategy of successive approximation optimization method to reduce the design difficulty. Based on the theory of aberration, the best position of freeform surface in the off-axis system was analyzed. At last, two four-mirror optical systems with long EFL and large field of view were designed, the effective focal length are 1.95m and 4.5m, respectively; the field of view for both systems are 3°. The modulation transfer function is close to diffraction limit.
Optical system design for a short-wave infrared imaging spectrometer
A short-wave infrared (SWIR) imaging spectrometer with all reflective elements was designed, covering the spectral range 1000-2500nm with a spectral resolution of 10nm. The imaging spectrometer is composed of an off-axis three-mirror anastigmatic (TMA) telescope and an Offner spectral imaging system with convex grating. The design result shows that the system has compact structure, light weight, wide field of view, small smile and keystone, excellent image quality and practical feasibility. The design method is simple and easy-operating.
Advances in optical design and optimization of miniature zoom optics with liquid lens element
An optical design of 2X optical miniature zoom lens with liquid lens elements and optimization method: discrete lens groups shifts (DLGS) has been presented in this research. Two liquid elements are applied to minimize the overall length of zoom optics. Moreover, a compensative optimization method with assistance of Genetic Algorism is introduced in this research with a new concept of DLGS, which not only solve the complicated problem of liquid optics itself but also improve the performance of optics. Genetic algorithms (GA) written in CODE V plays the role at finding out the appropriate parameters such as curvatures, thicknesses, glass materials and etc. Besides, one table with great lens groups shifts by GA would be created to move the lens groups on the optimal positions of different zooms. As a result, the DLGS optimization method associated with the GA optimization improve the zoom lens performance averagely 40% better than traditional ones.
Advanced Sensing and Measurement
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The measurement of optical reflector with complex surface using nano-CMM
Zhichao Wu, Tong Guo, Jinping Chen, et al.
Among variety of methods to measure complex surfaces, coordinate measurement is widely used in reverse engineering and measuring complex topography. In this paper, a coordinate measuring system based on 3D tactile probe is introduced. This system can measure complex surface with resolution of 1nm, measuring range of 25mm×25mm×5mm. The component of the measuring system, the principle and advantages of the probe are also introduced as the major part. We used the nano-CMM to test an optical reflector with sine curve surface. The fluctuation of the topography is about 5 micrometers. The result is compared with the data of AFM and the source of deviation is analyzed in the conclusions.
Wave-front coded optical readout for the MEMS-based uncooled infrared imaging system
In the space limited infrared imaging system based MEMS, the adjustment of optical readout part is inconvenient. This paper proposed a method of wave-front coding to extend the depth of focus/field of the optical readout system, to solve the problem above, and to reduce the demanding for precision in processing and assemblage of the optical readout system itself as well. The wave-front coded imaging system consists of optical coding and digital decoding. By adding a CPM (Cubic Phase Mask) on the pupil plane, it becomes non-sensitive to defocussing within an extended range. The system has similar PSFs and almost equally blurred intermediate images can be obtained. Sharp images are supposed to be acquired based on image restoration algorithms, with the same PSF as a decoding core.We studied the conventional optical imaging system, which had the same optical performance with the wave-front coding one for comparing. Analogue imaging experiments were carried out. And one PSF was used as a simple direct inverse filter, for imaging restoration. Relatively sharp restored images were obtained. Comparatively, the analogue defocussing images of the conventional system were badly destroyed. Using the decrease of the MTF as a standard, we found the depth of focus/field of the wave-front coding system had been extended significantly.
Measurement of the mirror reflective spectrum of typical roughness surface in the ultraviolet band
Lu Bai, Zhen-sen Wu, Yan-hui Li
Reflective light of a surface contains many features of a surface. It is usually used as a powerful tool for process in situ or ex suit monitoring because of its non contact and non destructive nature. Scatter measurements of some typical samples in the UV band are performed by using an ellipsometry WVASE 32 made by J. A. Woolam Co. Inc. The mirror-direction reflective measurement results of different sample obtained by ellipsometer are compared. And these kinds of researches about measuring and analyzing of typical roughness samples in the ultraviolet band have significant meanings in a lot of related fields.
Advances in Space Optics
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Optical design of multispectral sensor using off-axis three-mirror reflective optics
Tianjin Tang
The Paper describes the designing of the multi-spectral sensor optical system using off-axis three-mirror reflective optics which is particularly suitable for wide-field, wide spectral range, multi-spectral and high resolution sensor imaging optics. The off-axis three-mirror reflective optics provides an obstruction free field of view and high spatial resolution over the wide-field, the relay optics is used to adjust the multiplication factors for infrareds. The optical system concludes three-mirror optics with large relative aperture and infrared relay optics, the dichroic mirror and filters subdivide the wide spectral range into nine bands, each corresponds to respective field. The working wavelength ranges from visible to medium wave band. The paper also analyses the selection of dichroic schemes. The MTF of each branch at respective fields which are all near the diffractive limit are also given. The MTF of the camera is also forecasted at the end of the paper.
Design of a four mirror optical system with wide field of view
Aman Wei, Jun Chang, Lifei Zhang, et al.
A method based on Seidel aberration theory to design a four mirror optical system with wide field of view was mentioned in this paper. In this method, Seidel aberration theory was studied, and the technical parameters of the system were got from the demands, then the technical parameters, such as the diameter of entrance pupil and the field of view were substituted into the Seidel aberration equations. Then we solved the equations with additional limit, and got the initial parameters of system, for example the radius of curvature of each mirror. The example in this article was a design of a four mirror system with a field of view of 15°and F number of 5. This example showed that the method based on Seidel aberration theory to design a four mirror optical system with wide field of view is effective and feasible.
The effects of piston error on image quality of synthetical aperture optical imaging system
The relationship between image quality and piston errors of synthetical aperture optical imaging system has been studied. An active segmented cophasing imaging system and its Zemax simulation model were set up. Diversity piston errors were introduced and the corresponding MTF were calculated with the Zemax simulation model. Simulation experiments have been carried out with the cophasing imaging system, and the results are coincident with the simulated results. The results show that image quality changes with the increase of the piston error periodically if the piston error is smaller than the coherent length of the light source, and the image quality becomes the worst if the piston error is an odd multiple of π.
Poster Session
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Design of all reflective zoom optical system of wide field of view with 3 mirrors
Lifei Zhang, Jun Chang, Aman Wei, et al.
All reflective zoom optical systems have advantages of no color aberration and lightweight which have a wide application prospects in space optical system. All reflective zoom optical systems, which have been designed, all use telephoto construction. And these systems have disadvantages of big obscuration and small field of view. So in order to satisfy of requests the wide spectrum and field of view of space optical system, this paper design a novel all reflective zoom optical system which uses anti-telephoto construction with 3 mirrors. Firstly, using the zoom theory of differential, the initial configuration with 2 zoom ratio was obtained. Then simulating and optimizing the system with Zemax that is software of the optical design, we get a novel all reflective zoom optical system. It has a smaller obscuration and bigger field of view than traditional reflective zoom optical system. At last, the image qualities of this system was evaluated and concluded. And the image qualities of this novel all reflective zoom system is well and the construction of the optical system is reasonable. It can be applied in space optical system.
Design of an optical system in an ultra-short throw projector using the aspheric surfaces
Xuemin Cheng, Yong Wang, Qun Hao
The ultra-short throw projector with interactive function has been popular these days. To perform interactively, a pen is equipped, e.g., containing an infrared LED. To detect the movements of the pen, another optical system is needed. The optical systems used in these projectors need to achieve special performance qualities, especially a small distance between the projector and the screen while maintaining high optical performance and a large field of view (FOV). In this paper, an optical system to detect the movements of the pen is designed. We begin the design procedure with an existing optical system whose FOV is relatively small. To expand the FOV, an element is added to the existing system using the Wassermann-Wolf method for a pair of conjugate foci. Then a table of coordinates of points is gotten and fitted into two aspheric surfaces. CODE V is further used to optimize the performance of optical system. Manufacturing method of the optical system are taken into account as well.The f/number of the optical system is 1.1, the value of MTF (modulation transfer function) is more than 0.6 at 100 cycles/mm, FOV is 69°, object distance is 300 mm, and the maximum distortion is less than 4%.
Prototype design of an all-reflective non-coaxial optical zooming system for space camera application without moving elements based on deformable mirror
Hui Zhao, Xuewu Fan, Gangyi Zou, et al.
Based on optical zooming used to capture images with variable resolution and field of view (FOV), an all-reflective non-coaxial optical zooming system without moving elements is designed for space camera application. In this prototype design, a deformable mirror (DM) whose curvature radius can be changed is introduced. By carefully selecting the optical power of conventional reflective mirrors surrounding the DM, the overall focal length of the imaging system can be greatly changed with slight variation of curvature radius of DM. The focal length of the system can be changed from 48mm to 192mm and the system performance is approaching diffraction-limited with diverse criteria and the maximum stoke of DM is still within its physical limits at the same time. The experimental results prove the effectiveness of DM based optical zooming and will provide a new routine for new type of space camera design in the future.
The design of a stepper motor control-based high-precision varifocal imaging optical system
Bai Xiang
This study, while introducing the theories and makeup of conventional cam varifocal system, indicates the two faults stemming from their inherent mechanism and potentiometer-based focal-length measurement: 1) inability to stop optic axis vibration and 2) considerable error in real-time output of focal-length value. As a result, a stepper motor, instead of cam mechanism, was employed to control mirrors of variofocus and mirrors of compensation in moving accurately along straight-ling rails so that continuous focal-length variation and surface image positioning were accomplished; a linear encoder was substituted for potentiometer in realizing real-time output of focal-length value and also in closed-loop control of stepper motor. Compared with the cam mechanism, this system provides 90% less vibration and 80% more positioning precision, thereby basically solving the problems of the cam system and enabling the high-precision angular measurement.
Infrared dual-band telephoto design used in joint transform correlator
Da Mu, Jianing Dong, Chunyun Xu, et al.
On the basis of optical correlation detection, photoelectric hybrid joint transform correlator(JTC) is widely used in military, aviation and intelligentization, etc. It has the advantages of great flexibility and high precision of recognition. However, the optical system which is in front of joint transform correlator(JTC) is applied to receive the infrared radiation of the target. It also has a certain influence on JTC’s detecting precision and tracking ability. Dual band infrared imaging system can receive different wave band of infrared radiation. Therefore, the image quality of optical system plays an important role in the joint transform correlator(JTC). According to the requirements of the joint transform correlator (JTC), the processes of optical design including the allocation of parameters and the selection of initial structure are presented. The infrared dual band coaxial telephoto system is designed for target detection. The system which is composed of four lenses can image in both 3μm~5μm and 8μm~12μm wavebands. The focal length is 200 mm and the relative aperture is 1:3. The system has the characteristics of small volume and compact structure. The optical system image quality is evaluated with ZEMAX optical design software. The results have shown that MTFs of the system are 0.62 and 0.35 for both wavebands respectively at 17lp/mm of spatial frequency which are closed to the diffraction limited curve. The relative aperture, field of view, and focal length are same for both spectral regions. The system meets the requirements of technical specification and improves the ability of JTC in target tracking and recognition.
Design of cooled athermalized infrared telephoto lens
Yu Zhang, Ji-Yang Shang, Yue Xu, et al.
With the development of the technology of infrared, infrared optical system has been widely used in many fields, especially in tank target detection and recognition. The difficulty and key in the designing of LWIR optical systems for working under temperature range of -60°C~80°C is athermalization. In this paper, the infrared telephoto lens is designed which is composed of four pieces of lenses. The working temperature range is -60°C~80°C. In order to balance the chromatic aberration and thermal aberration, two aspherical surfaces are used in this cooled athermalized infrared optical system. The effective focal length is 100mm and the F-number is 2.The full field of view is 7.0°. The curve of MTF is close to diffractionlimit curve. Within the working temperature, the value of MTF at 17cy/mm is always large than 0.4. The result shows that the infrared optical system achieved better athermal performances at the working temperature range.
Compact optical imaging system for star tracker with long focal length and perfect thermal adaptability
Yiqun Ji, Rongbao Shi, Hucheng He, et al.
A star tracker optical imaging system is designed for Polaris detection. System parameters determination and its configuration chosen method are given. Based on Macsutov-Cassegrain configuration, the system is designed imagery tele-centric. It works at 0.6μm~1.1μm waveband and the view field is 0.5 degree. The tube length of the system is 80mm, which is only 8 percent of its focal length. Its MTF reaches diffraction limit and the spot diagrams are quit near a circle. About 80% of the energy is encircled in a CCD pixel. And the distortion is less than 1%. Moreover, it has a perfect thermal adaptability from -40℃ to 60℃.
Optimization design and error analysis of photoelectric autocollimator
Lei Gao, Bixi Yan, Mingjun Hu, et al.
A photoelectric autocollimator employing an area Charge Coupled Device (CCD) as its target receiver, which is specially used in numerical stage calibration is optimized, and the various error factors are analyzed. By using the ZEMAX software, the image qualities are optimized to ensure the spherical and coma aberrations of the collimating system are less than 0.27mm and 0.035mm respectively; the Root Mean Square (RMS) radius is close to 6.45 microns, which is identified with the resolution of the CCD, and the Modulation Transfer Function (MTF) is greater than 0.3 in the full field of view, 0.5 in the centre field at the corresponding frequency. The errors origin mainly from fabrication and alignment, which are all about 0.4" . The error synthesis shows that the instrument can meet the demands of the design accuracy, which is also consistent with the experiment.
Design of a front objective in a monocular zoom video microscope
Wenzhe Liao, Zexin Xiao, Gang Chen
Nowadays, the monocular zoom video microscope is one of the most widely used detection equipment at mainstream position in the electronics industry. The front objective of this kind of microscope is conducive to the development of its magnification. At present, the mainly similar products design out by non-coaxial system, whose optical axis between front objective and objective is uncoaxial, this method with the aid of the front objective in the Stereo microscope. However, the front objective is using coaxial system in monocular zoom microscope actually. So, Tailor-made a front objective of zoom microscope is imperative. At first, we point out this unique design idea form the special imaging relationship between front objective and objective in zoom microscope .And then we choose the position of entrance pupil、numerical aperture and the layout. At last we enumerated examples which zoom the magnification in, and analyze the design methods of the similarities and differences.
Design of reflective active zoom systems with four mirrors
Benlan Shen, Jun Chang, Jiao Ouyang, et al.
The traditional zoom systems usually change the spaces between optical components to realize the variable focal lengths. Based on active optics, a new type of reflective active zoom system with four mirrors is proposed, which is different from the traditional zoom system by changing the spaces between optical components1. The new zoom system consists of an afocal front group with three mirrors, and the fourth mirror used for focusing. The relation among the four mirrors is determined by the Pezval condition. The secondary and third are deformable mirrors, contributing to the transition among different focal lengths by the curvature radius variation controlled by the voltage, with the constraints limiting its’ changing rules. According to the designed system characteristics and the practical requirements, based on 3rd-order aberration theory, a set of Seidel aberration coefficient functions are established, with the constraint limitations. Then the initial construction parameters of the optical system can be achieved. The new active zoom system with four mirrors can realize that the zoom rario is 3, the focal lengths vary from 100mm to 300mm, and the field angle of view range is 0.22° ~3.6°, and the wide working band is from the visible to the infrared. At the same time, because of the control flexibility, the active optical zoom system has the potential to be widely applied in remote sensing, life medical and other fields.
Cyclops opening-up fiber for real-time fluorescence sensing
Yi Yang, Guanjun Wang, Jian Cui
Compared with traditional fluorescence-based microstructured fibre sensors using filled structure, the opening-up microstructured fibres have shown many advantages for real-time sensing. The design and theoretical study about Cyclops opening-up microstructured fibre is present in this paper. In Cyclops fibre, a large asymmetry hole is placed in fibre cladding. A tri-hole design is adopted for fibre core to enlarge the evanescent field interactions with measured material. This structure is compatible with the traditional stack-draw processing. To make the opening-up structure, chemical etching (with acid) or polishing machining could be used for the asymmetry hole. The opening depth and shape of large asymmetry hole is important for real-time sensing response in Cyclops opening-up fibre. The relationship between marching depth in cladding and fluid concentration distribution at different time in evanescent field near fibre core is analyzed numerically based on incompressible Navier-Stokes equations and finite element method (FEM). The results show that the concentration distribution in evanescent field adjacent to fibre core can reach the true value out of cladding below ten seconds by design cladding structure appropriately. The field distribution of fundamental mode and some cladding mode of Cyclops fibre without tri-hole core and with different tri-hole are presented in this paper too. Cyclops fibre show good characters in these aspects compared with wagon wheel (WW) opening-up fibre. In order to evaluate the performance of sensing based on Cyclops opening-up fibres we adopted the modal power fraction (PF) within the sensing region and the effective modal area (Aeff) and the fluorescence capture fraction (FCF). The results show the Cyclops opening-up fibre is a competitive candidate for real-time fluorescence sensing.
Design of the second parallel optical path of the telescope photoelectronic imaging system
Xingyu Gao, Gang Chen, Daoyin Yu, et al.
A second parallel CCD (CMOS) imaging system for an telescope objective with the fixed D/f' is proposed in detail. As a direct imaging system that the CCD target surface coincides with the imaging surface of the telescope objective, it shows the outstanding performance of more than doubled resolution compared with the ordinary telescope objective under the same D/f'. Based on the discussions about the second parallel optical path telescope system, three design examples are compared and analyzed. The relation between the optical properties of image field and the optical elements of the second parallel path is clarified, which provides an operable method for readers. This practice has proved the outstanding performance of the new telescope objective photoelectronic imaging system which indicates potential applications in broad scientific and industrial prospects.
Radiation distribution measurement for forest plant canopies tracing
Xuefen Wan, Jian Cui, Yi Yang, et al.
Plant canopies structures are important biophysical parameters required in many ecological and climate models. To obtain precise canopies characteristic, the radiation distribution in forest gap should be tracing. In this paper, a radiation transmission measuring method with gyroscope correction for forest gap radiation distribution measurement is present. And a Zigbee wireless network is imbedded for communicating between portable full-trace radiation detector and host computer. Using the solar beam as a probe, the measuring nodes collect radiation distribution in forest gap. Because the constant pace of operator in forest and other outdoor occasion is hard to validate, radiation distribution curves suffer some error. We present a Forest radiation distribution meter with Gyro correction for TRAC measuring. In this meter, A Gyroscope records transect route data and provide speed correction for canopy gaps curve in tracing route. A Microchip PIC16F877 MCU is employed for radiation data collection. The collected data is sent to central station by Zigbee wireless network or CF376 in-line USB flash drives/SD card. Solar radiation spike data and other environment parameters (Temperature and Humidity) are sampled simultaneously. So the gap removal processes suffer less error. A portable node provides full-trace radiation distribution. Host computer can get potential relationship in tracing-line LAI and FPAR and compute them in long-term. A portable full-trace radiation detector and host computer is tested. The experimental results show our design could be a competitive candidate for radiation distribution measurement for forest plant canopies tracing.
off-axis three-mirror zoom system perturbation analysis
Jiao Ouyang, Jun Chang, Lifei Zhang, et al.
Reflective zoom system is widely used in the design of large size, wide spectral, high resolution system due to its great superiority in compacting size, system weight, aperture size, free chromatic aberration and thermo-stability. But for coaxial system, its disadvantage of obstruction renders the FOV (field of view) and light utilization rate unsatisfactory. Thus, to make the secondary and tertiary mirror off-axial is a good choice for optical designers. However, there are two problems in the alignment of off-axis zoom optical system. First, the Seidel aberration theory is not applicable for a system without rotational symmetry. Second, it is hard to control the misalignment status when zoomed. To solve this problem, the vector aberration theory is selected to analyze the off-axis three-mirror zoom system. When small perturbation is applied to the system, coincident with the alignment in reality, the residual aberration varies along with the movement of secondary and tertiary mirror. As the result, aberration character of misalignment three-mirror zoom system is provided, which offers guidance for misalignment determination and makes sure of the normal operation of the zoom system. This paper makes description of our experiment on an off-axis three-mirror zoom system and furnishes the figure of sensitivity in different zoom position. The conclusion may provide a reference to the vector aberration theory study on off-axis three-mirror zoom system and computer aided alignment.
Design and modeling of a new CO2 laser heater for thin film deposition applications
In this paper, we report on designing a new raster-scanned CO2 laser heater for homogeneous heating of the disk-shaped substrates. This new design aims at concentrating the laser energy near the substrate peripheral edge, which mostly tends to remain cooler than the inner parts during the heating process. A comprehensive heat diffusion model has been developed to predict the temperature and its homogeneity on the substrate depositioning face. This new kind of laser heater can favorably be used in preparation of nanostructured thin films where the shape and size of the embedded nanoparticles depend on the maintained temperature during the depositioning time interval. This heater can also be used for CO2 laser conditioning of the prepared thin films to enhance their damage threshold for high power laser applications.
Temperature effect on ultraviolet differential absorption cross section of SO2
Weijia Jin, Haiming Zheng, Haiping Li, et al.
When the technique of differential optical absorption spectroscopy (DOAS) is applied to the pollutant monitoring, the differential absorption characteristics of pollution gases will change greatly owing to the flue gas is often with high temperature. This will bring the influence on the detection results. This article mainly aims at the temperature effects for SO2 differential absorption cross section by recordings the absorption spectra. The results show that the differential absorption property changes dramatically with temperature. The differential absorption peaks in the region of 280.0-320.0nm decrease with the increase of temperature while the valleys will increase. So the entire differential absorption cross section decreases with the increase of temperature, but no wavelength drift and differential absorption structure change appear with temperature. By measuring the differential absorption cross section of a few peaks at different temperature, it is found that the reduction regularity at different wavelength is varied. The variation at 286.7nm, 293.9nm and 304.0nm with temperature is in a manner of cubic polynomial, while the variation at 300.0nm presents a nearly linear decline. When the temperature rises from 300K to 450K, the relative change of the differential absorption cross section at 286.7nm is 77.1%, while it can reach 84.0% at 300.0nm.
Research on the key parameters influencing the anti-vibration capability of time-frequency-domain interferometer
Fanghua Zhang, Qun Hao, Yao Hu, et al.
This paper introduces a time-and-frequency-domain (TFD) anti-noise phase-shifting interferometry, and designs an experimental system to test the anti-vibration ability of this method. In the system, a plane mirror is measured under the external vibrations simulated by the standard mirror propelled by PZT. During the measurement, each of the key parameters is assigned different values. By analyzing the testing results, the law of the parameters’ influence on system anti-vibration capability can be obtained. According to the law, the optimization parameters can be determined so that the system has the maximum anti- vibration capability.
Optical design of solar blind ultraviolet warning system
Quanyong Li, Chunyun Xu, Jianing Dong
Ultraviolet warning technology is one of the important methods for missile warning. “Solar blind region” provides a very effective way to detect the target for missile approaching alarm. In order to find the target by detecting the ultraviolet radiation of missile efflux plasma, ultraviolet optical system design of large field of view and large relative aperture is the key for the technology of ultraviolet detection. From the academic point of view, the structure parameters are determined for 2048×2048 ultraviolet CCD detector according to the requirements of ultraviolet warning system. The refractive ultraviolet warning optical system is designed for 0.24μm ~0.28μm wave band with ZEMAX optical design software. The focal length is 41mm, the field of view is 46°and the relative aperture is 1:3.5. In order to ensure the detected energy, aspherical and binary surface are adopted to reduce the aberration and spot size of the system. Within the 0.8 field of view RMS of spot diagram is less than 13μm. It is smaller than the pixel size 13.5μm of ultraviolet CCD. The energy concentration is more than 80%. This optical system has long focal length and large relative aperture that meet the energy requirements of warning system. Large field of view can satisfy the range of searching targets. The spot diagram RMS of each field of view is so small that can meet the requirement of image quality. In addition, the system is composed of six lenses. The structure of it is simple, the volume is small and the application is very convenient.
A new type of wide spectral coverage echelle spectrometer design for ICP-AES
Shaojie Chen, Yuguo Tang, X. Bayanheshig, et al.
The inductively coupled plasma atomic emission spectrometry (ICP-AES) has always attracted great interest and is widely used for routine elemental analysis. While one drawback of this technique is the fact that conventional Czerny- Turner spectrographs in combination with CCD cameras are very limited either in terms of spectral resolution or in terms of simultaneously detectable spectral range. A cross-dispersion system with echelle grating and prism has therefore been developed, and the spectral image is directed by large area charge coupled device (CCD). This configuration meets the needs of atomic emission spectroscopy well, since it has many benefits including high resolving power, spectral coverage, high sensitivity, and high optical throughput. While, because the limitation of the development of detectors, it is difficult to complete wide spectral coverage measurement. Due to the improvements in optical design, this system can detect the wide spectral coverage from 180nm to 900nm simply by rotating the prism, and these two ranges are 180nm- 260nm and 210nm-900nm, with a high resolution 0.009nm@200nm. The detection of different elements only needs to choose appropriate wavelength coverage, thus lots of elements can be analyzed within quite short time. The novel optical design of this instrument is presented in this paper and its merits are discussed. The optical spectral resolution and the precision of wavelength calibration are found to be satisfactory and within design goals. Experiments show that the ICPAES with echelle spectrometer is available to detect multiple elements within a short time correctly, and the wavelength precision is better than 0.01nm.
Designing adapted to fabricating of holographic silver gratings
Amir Asgari, Naser Partovi Shabestari, Hooshang Araghi, et al.
A few holographic silver gratings with maximum diffraction efficiency in the 700-1100nm wavelength range were designed. They can be attractive for stretching and compressing pulse in CPA (chirped pulse amplification) technique. KPP1206 photoresist was used to model the final pattern on photoresist thin film. This paper was devoted to consider super Gaussian gratings. Therefore, approximately identical exposure energy density intervals were used for optimizing grating profile. Accordingly, the Genetic Algorithm (GA) was employed by Grating Solver software to optimize groove spacing, groove depth and groove shape of the grating for TM polarized light in the 1st order (littrow mount).Also, Dependency of diffraction efficiency (DE) to depth and duty cycle of super Gaussian silver gratings in 1064nm was shown.
Fiber ring depolarizer with one degree of freedom
Tao Liu, Qingyang Yu, Chunhua Wang, et al.
A one-degree of freedom (DOF) tunable single fiber ring depolarizer is proposed by setting the bend-induced birefringence in the fiber ring specially to behave as a half-wave plate (HWP) and with the optimal coupling ratio of the coupler. Depolarization can be realized by just rotating the fiber ring. The methods of making and testing the HWPperformance of the fiber ring are analyzed and discussed. A 12-meter long fiber ring depolarizer is demonstrated to depolarize a Fabry-Perot (FP) laser with 10-meter coherent length. Degree of polarization (DOP) of 1.5% can be reached by rotating the whole set of fiber ring. Moreover, if a polarizer ahead of the fiber ring is inserted, a full scale one degree of freedom tunable depolarizer can be realized.
Based on the method of subaperture splicing detection on spherical
Weirui Zhao, Zhengnan Liang, Guangyu Pan
This thesis studies the stitching interferometry of large aperture optical aspheric surface. Analyzing the data of the adjacent two sub apertures overlap by using SIFT algorithm, we obtained the stitching parameters between the sub-aperture and the overall surface information of the inspected mirror. We wrote the interference graph solution phase program, Zernike fitting program, stitching test program, and completed the principle experiment. We have given the compare results of stitching and full caliber testing, the RMS deviation of the two kinds of method is less than 2nm.
Smile effect detection for dispersive hypersepctral imager based on the doped reflectance panel
Jiankang Zhou, Xiaoli Liu, Yiqun Ji, et al.
Hyperspectral imager is now widely used in many regions, such as resource development, environmental monitoring and so on. The reliability of spectral data is based on the instrument calibration. The smile, wavelengths at the center pixels of imaging spectrometer detector array are different from the marginal pixels, is a main factor in the spectral calibration because it can deteriorate the spectral data accuracy. When the spectral resolution is high, little smile can result in obvious signal deviation near weak atmospheric absorption peak. The traditional method of detecting smile is monochromator wavelength scanning which is time consuming and complex and can not be used in the field or at the flying platform. We present a new smile detection method based on the holmium oxide panel which has the rich of absorbed spectral features. The higher spectral resolution spectrometer and the under-test imaging spectrometer acquired the optical signal from the Spectralon panel and the holmium oxide panel respectively. The wavelength absorption peak positions of column pixels are determined by curve fitting method which includes spectral response function sequence model and spectral resampling. The iteration strategy and Pearson coefficient together are used to confirm the correlation between the measured and modeled spectral curve. The present smile detection method is posed on our designed imaging spectrometer and the result shows that it can satisfy precise smile detection requirement of high spectral resolution imaging spectrometer.
A practical approach for measurement of IR optical system transmissivity
Yi Jian, Zhaoxin Pan, Shiyong Wang, et al.
Transmissivity is a crucial parameter for an optical system, especially for an infrared imaging system, which is commonly used for detecting and tracking dim target. NETD (Noise Equivalent Temperature Difference) is an important indicator for quality of an infrared FPA system, and it is always related with the transmissivity of its optical system, which is dealing with energy transmission of the system. So it is necessary to measure the transmissivity when optical system is fabricated. However it is usually not easily available, when the structure of IR optics is complex in particular. In this article, a new reliable method for measuring the transmissivity of optical system for cooled infrared detector is introduced. The principle of measurement is based on Etendue conservation and luminance (radiance) conservation when light travels through an ideal optical element. We put a Lambertian blackbody source attached at the cold stop of IR detector of under testing system, and get the grey-scale value of axis point of detector. Afterwards we put on the optical system for the detection and calibrate the optical path for imaging system. Then we put the Lambertian blackbody source at the position of entrance pupil of optical system, and get the grey-scale value of axis point of detector again. With proper calculation with these two grey-scale value, we could get transmissivity of this optical system. A ray tracing simulation is made to show the result for supporting correctness of this approach. A high-aperture Lambertian blackbody source is required for the embodiment of this measurement.
Design and optimization of chopper based on Labview
Guo Li, Xiaolei Wang, Lichun Feng, et al.
Chopper is widely used in optical system to produce a series of optical pulses which has particular shape and frequency. This paper presents a way to make a simple chopper based on Labview. Labview and NI DAQ are widely available in universities. So with this method chopper system can be easily constructed for temporary use. NI DAQ uses counter tools to detect the frequency of modulated laser and produce several feedback signal to drive the location and rotate speed of modulation plate, which leads to the change of modulation frequency and duty. This paper can provide a reference for experiment work in optics and other natural science.
Evaluation of parallel phase-shifting digital holography by photon-counting method
Lin Miao, Kouichi Nitta, Osamu Matoba, et al.
Minimum optical energy required for parallel four-step phase-shifting digital holography is evaluated numerically by using photon-counting method. One of the attractive features of parallel phase-shifting digital holography is the instantaneous recording of fast 3D events where only the complex amplitude distribution of an object wave is obtained. The reconstruction is executed by numerical wave propagation such as angular spectrum propagation or Fresnel propagation. Numerical results indicate that required optical energy of an input image with 512 × 512 pixels is about 11 pJ. Under the criteria used in the evaluation, the required optical energy is independent of the image size.
The effect of temperature characteristic of Faraday rotator to passively demodulated all optical fiber current transformers
In order to move signal detecting point to the most sensitive position and improve the immunity of the system at the same time, the scheme named passively demodulated all optical fiber current transformer (AOFCT) inserts a Faraday rotator of 22.5° rotation angle between fiber λ/4retarder and leading fiber. To improve the performance of this type of all fiber current transformer, after considering the temperature features of a large proportion of Faraday crystals, the effect of the Faraday rotator’s temperature properties on temperature stability of the passively demodulated AOFCTs are theoretically analyzed and numerically calculated. The results show that the errors induced by the Faraday rotators are beyond the requested values in the International Standard IEC 60044-8:2002 of International Electrotechnical Commission (IEC) and the State Standard of P.R.China GB/T 20840.8-2007. Finally, to solve this problem, some possible solutions are suggested.
Research on the real-time calibration of the varifocal photoelectric imaging system
A real-time system for optical axis of the varifocal photoelectric reconnaissance and tracking system is designed in this paper. Two images are acquired by the DSP processing system before and after zooming the focal length, and the varifocal and shifting coefficients are calculated real-timely through extracting the feature points and affine transform, etc, while the rotation coefficient equals to zero basically. The shifting parameter can be used to calibrate the optical axis, and its calibration precision is less than one pixel. The system can reduce the requirement of mechanical processing technology and mechanical tolerance greatly in the production procedure of the photoelectric reconnaissance and tracking system with a long focal length, and can make the system easer to implement.
Accuracy analysis of surface figure fitting based on opto-mechanical-thermal technology
The influence of errors on the optical system’s image quality was theoretically investigated using error theory. The accuracy of surface figure fitting was researched. In this paper, we analyzed many sections that may cause error based on thermal analysis and mechanical analysis. We used error analysis to consider the accuracy of surface figure fitting. We took account of the error of ABAQUS modeling, initial error, error of surface figure fitting, error of MATLAB and the error of ZEMAX. We at last gained the total error, and analyzed which is the dominant error. The main result can be used to assess and correct the error of opto-mechanical-thermal, and provide support for Quadratic optimization design.
Multi-limit unsymmetrical MLIBD image restoration algorithm
Yang Yang, Yiping Cheng, Zai-wang Chen, et al.
A novel multi-limit unsymmetrical iterative blind deconvolution(MLIBD) algorithm was presented to enhance the performance of adaptive optics image restoration.The algorithm enhances the reliability of iterative blind deconvolution by introducing the bandwidth limit into the frequency domain of point spread(PSF),and adopts the PSF dynamic support region estimation to improve the convergence speed.The unsymmetrical factor is automatically computed to advance its adaptivity.Image deconvolution comparing experiments between Richardson-Lucy IBD and MLIBD were done,and the result indicates that the iteration number is reduced by 22.4% and the peak signal-to-noise ratio is improved by 10.18dB with MLIBD method. The performance of MLIBD algorithm is outstanding in the images restoration the FK5-857 adaptive optics and the double-star adaptive optics.
Polarization characteristics of a linearly polarized laser beam after hollow light pipe in projectors
PengFei Zhao, Shengtao Zhang, Yanhong Wang, et al.
In this work, a multilayered dielectric film and metallic film are used as reflecting surface to fabricate light pipe. Linearly polarized laser beam with wave length of 532nm enters into the light pipe. After multi-reflection process, laser beam come out from the light pipe. We have found that the polarization state of linearly polarized incident light after reflection are different for the light pipe coated with metal and multilayered dielectric film. We also found a distributed polarization characteristic in the output optical field. The polarization degree has been simulated by using ZEMAX software. Laser speckle contrast from a glass diffuser is measured to exam the simulated result.
A novel optical beam deflection detection system based on aspheric lens for high-speed atomic force microscope
Jianyong Zhao, Guangyi Shang, Weitao Gong, et al.
The optical lever detection method has been widely used to detect the cantilever deflection in atomic force microscope (AFM) due to its simple mechanism and high sensitivity. The deflection detection of very small cantilever is a key and difficult issue in the development of a high-speed AFM. In this paper, a specially designed optical beam deflection detection system based on an aspheric lens is presented. The aspheric lens is fixed on an adjustable metal tube above the cantilever to focus the laser beam with a small spot. Two laser line beamsplitter cubes are installed symmetrically and oppositely over the aspheric lens with separately mounting a diode laser and a position sensitive detector (PSD) on two translation stages at the same height. The collimated laser beam is reflected down by one cube and focused by the aspheric lens at an off-centered position. The focused beam is then incident upon the cantilever and reflected back onto the opposite off-centered position. Change in the reflection angle caused by the cantilever deflection results in a parallel shift of the outgoing laser beam after the aspheric lens. The laser beam is finally reflected onto the PSD by the other cube. Experimental results show that the laser beam can be focused with a spot of less than 16 μm in diameter. With above system, the deflection detection of the small cantilever can be realized, which meets the requirement for the use in a high-speed AFM.
Parameters affecting pattern fidelity and line edge roughness under diffraction effects in optical maskless lithography using a digital micromirror device
In optical maskless lithography in concern, a digital micromirror device plays the role of a digital mask. Due to the spatial/temporal configuration of micromirror arrays/response or the specification of illumination/projection optics, the irradiance may be influenced by diffraction effects. In present study, an investigation of various optical maskless lithography models based on binary micromirror reflections is performed in consideration of the diffraction effect. To evaluate lithographic parameters dissolved in the lithography models, parametric studies are performed focusing on pattern fidelity and line edge roughness. To reduce corner rounding phenomena due to an image size and further to a reflection criterion, the auxiliary corner reflection adjusting feature (ACRAF) analogous to conventional serif are employed and the effectiveness of ACRAFs is analyzed. The potential of utilizing the adjusted parameters for enhancing pattern fidelity and line edge roughness under diffraction effects is demonstrated through simulations and experiments.
Wavefront fitting with Zernike polynomials based on total variation regularization method
The wavefront function can be achieved by fitting the optical surfaces date using Zernike polynomials because of the corresponding relation between Zernike polynomials and Seidel aberrations. In this paper, the reason of the stable solution cannot be achieved when proceed to fit wavefront by least square, Gram-Schmidt orthogonalization and Householder transformation is deduced in theory. The Zernike coefficients fitting method based total variation (TV) regularization is presented to resolve the instability of numerical solution because of there are errors in phase values obtained by optimization algorithm in Least Square, Gram-Schmidt orthogonalization and Householder transformation. The solving model of Zernike coefficients is developed, and the regularization term is introduced in solving model, then the L-curve method is applied to determine the regularization parameter and the modified steepest descent method is applied to solve Zernike coefficients. The simulation experiment shows that the proposed algorithm can be achieve the stable fitting coefficients with the error on fitting data.
Error and compensation of non-polarization splitting prism (NPBS) in single frequency laser interferometer
Zhaoji Liu, Jun Yang
An online compensation method of non-polarization splitting prism(NPBS) error in single frequency laser interferometer is presented in the paper. We study the effect of incident conditions to polarization characteristics of NPBS, establish online performance detecting system to study the effect of polarization error of NPBS in single frequency laser interferometer, realize the online compensation of NPBS additional phase shift by adding a half-wave plate to optical path, which improves contrast ratio of interference signal and restrains nonlinear errors of single frequency laser interferometer. The method proposed in our paper has an obvious advantage compared with the method of adjusting a quarter-wave plate to compensate additional phase shift of NPBS. The results indicate that the method can effectively compensate polarization error of NPBS, improve the quality of interference signal and raise measurement resolution of interferometer. Therefore, the method can be widely used in many fields such as the investigation and preparation of nanometer high-precision laser interferometer.
Design and theoretical investigation of nanograting for XUV outcoupler
Ying-Ying Yang, Wei Sun, Ling Zhang, et al.
We have theoretically investigated and optimized a nano-periodical highly-efficient blazed grating, which is used as an outcoupler for extreme-ultraviolet (XUV) radiation. The rigorous coupled-wave analysis (RCWA) with S matrix method is employed to optimize the parameters of the grating. The grating is designed to be etched on top layers of IR reflector, performs as a highly-reflective mirror for IR light and highly-efficient outcoulper for XUV. The diffraction efficiency of -1 order of this XUV outcoupler is greater than 20% in the range near 60 nm, which allows high resolution spectroscopy of the 1s-2s transition in He+ at around 60 nm with extreme precision. The theoretical calculations are verified by the experimental results.
De-coherence characteristic of laser light caused by Mie scattering
Yanhong Wang, Pengfei Zhao, Shengtao Zhang, et al.
An optical system model has been built up for evaluating de-coherence performance of Mie scattering by using ZEMAX software. The optical system consists of a linearly polarized laser source of the wavelength 0.6328 micrometer, the interferometer configuration with a double-arm beam path, the light pipe with the particles solution of variable parameters including the refractive index, the particle size and the particle concentration, and the detectors. Seven types of particles with different refractive index have been used as scattering medium. The de-coherence performance and the light energy loss have been calculated for solutions with different particle concentration and dimension. The calculated results indicate that the de-coherence performance can be improved by increasing the particle concentration in solution and the particle size. The improvement of the performance is more notable as the particle refractive index becomes higher. The dependence of the light energy loss caused by Mie scattering on the refractive index and size of the particle, and the particle concentration in solution is obtained.
Research on design of a cubic conjugate phase mask having the capability of controlling the bandwidth of wave-front coding system
Hui Zhao, Yingcai Li
In this paper, an extended cubic phase mask used to realize wave-front coding technique is derived in frequency domain. Then by splitting and re-combining the terms of the phase function, a new mask containing two conjugate cubic terms is generated and can be physically realized by shifting and superposing two cubic phase mask having relative displacement with respect to the center of the pupil plane. Simulation results indicate that this phase mask has the capability of changing the system effective bandwidth while maintaining the defocus invariance characteristic. The work reported can be extended to other phase masks and could be considered to be complementary to the existing researches.
Aberration retrieval for annular pupils using parametric model of point spread function
In this paper, we propose an aberration retrieval method for annular pupils using proposed parametric model of point spread function (PSF). With this model, the diffraction integral for annular pupils is expressed with Bessel-series representation and annular Zernike coefficients. Conjugate gradient algorithm is used to retrieve aberration coefficients of annular pupil from the corresponding spot intensity images. The iterative calculations of objective function and its gradient function are required for this algorithm. These calculations are accelerated by using the parametric model’s analytical expression instead of Fourier transforms. Numerical simulation and experiment are performed to validate this aberration retrieval method.
Analysis on the effect of extinction ratio in birefringent measurement by phase-stepping method
The theoretical and experimental analysis on the effects of extinction ratios of linear polarizer and analyzer in the measurement of birefringent retardance by a five-step phase-shifting method based on the plane polariscope is presented. Stokes vector and Mueller matrix are the tools used to perform this theoretical analysis. The theoretical analysis show that the coefficients of extinction ratios of linear polarizer and analyzer in plane polariscopic configuration can be eliminated by phase shifting and will not introduce errors with our proposed five-step method. A mica quarter waveplate with previously given phase retardation is tested and evaluated. The experimental comparison has been made between the calcite Glan-Thompson based system with extremely high extinction ratios and plastic Polaroid film based system with relatively lower extinction ratios. The experimental results show that there is no significant difference between the measured values from these two systems, which agrees well with the conclusion of theoretical analysis. Also, good experimental accuracy and repeatability are achieved as well by the proposed five-step phase-shifting method.
Research on surface deformation of lens fastened by adhesive under gravity load and aberration analysis
Shaohua Guan, Tianmeng Ma, Quanzhong Wei
In the design and production of optical instruments, various kinds of adhesive are used to mount optical element instead of screws, platens and other fixed parts. But in the assembly of high-accuracy lens and large-aperture lens, the effect of gravity and the curing stress of adhesive cannot be ignored, as a result, research on surface deformation of lens by this effect is necessary. In order to shorten design cycle and reduce costs, this paper designed a simulation analysis about lens structure fastened by adhesive (RTV adhesive), which made use of finite element software (Ansys). The analysis result indicated that the deformation was within the limit of permission, and several methods of correcting various aberrations were given. These results can be guideline in the practical work in the assembly of lens. Besides, further research on this item is suggested being launched in the future.
Stray light analysis of a space patrol
Li Lin, Huiyi Chen
The stray light of a space patrol is analyzed in this paper. The space patrol is used to observe the Earth in space. In the paper the definitions of stray lights in the optical system are introduced and the stray lights are classified based on their sources. After the analyzing the serious harm situations of the stray lights in the optical system is presented. Software Tracepro is used in analysis of stray light. The model of the space patrol is established in the software and stray light simulation and analysis of the space patrol are presented based on the evaluation criterion of maximum irradiance value. Three different situations are discussed. First, sunlight directly irradiates onto the sensitive surface of the detector; second, sunlight enters the system by the reflections of the space patrol’s body; and finally sunlight reflecting from the moon’s surface irradiates onto the sensitive surface of detector by the reflection of the space patrol’s body. In each situation, we respectively calculate different elevation angles in ranges between 15°~45° by the ray tracing method in the solar azimuth of 0° and 30°. Transmission paths of stray lights are obtained by ray tracing data in different circumstances and the important surfaces of the system are found out. Finally, some corresponding stray light suppression measures which can help to reduce harm of stray light are proposed.
Analysis and protection of stray light for the space camera at geosynchronous orbit
Xiaorui Jin, Li Lin
Stray light is the general term for all non-normal transmission of light in the optical system. The influence of stray light is different according to optical system’s structure. Large area array camera at geosynchronous orbit is facing more serious influence of stray light, especially for the small incident angle of sunlight on the system. It is in dire need of a detailed analysis of stray light of the basic shape of the optical system .In the paper, the influence on the camera used in space from stray light and the necessity to eliminate stray light are presented. The definition of the stray light coefficient and PST(point source transmittance) is briefed. In Tracepro, analysis of the impact of sunlight incident was made at different angles on the space camera, in the case of stray light factor for the quantitative evaluation. The design principle of the inside and outside hood is presented for the R-C (Ritchey Chretien) optical system. On this basis, in order to reduce stray light interference for the space camera, the primary and secondary mirror’s hoods were designed. Finally, when the incidence angle of sunlight is more than 3° incidence on the space camera, the coefficient of stray light is less than 2%. It meets the engineering requirements.
Analysis of thermal shock strength and quality factor with infrared optical domes
Youtang Gao, Shuo Liu, Yuan Xu, et al.
The development of infrared optical materials is always closely related to the research and exploration of material science. The infrared optical domes bears shock and produces stress when the infrared optical domes mounted on the missile moving at a high speed is shocked by high temperature. According to principle of energy balance in fracture mechanics proposed by D.P.H. Hasselman, the author analyzed the crack extension and derived the relationship between Infrared optical materials window model and thermal shock quality factor. Meanwhile, strong or weak of thermal shock for different samples whether they are thin or thick are compared through the operation of queuing algorithm. The conclusion is the internal surface of the domes isn’t heated when the window model is the thermal shock quality factor of thick sample and the heating time is between heating time constant and diffusion time constant. On the other hand, the internal surface of the domes is being heated when the window model is the thermal shock quality factor of thin sample and the heating time is between the two time constants. The most optical domes parts in practice is belong the thin model. For the thin model, reducing the thickness of optical parts can improve their thermal shock ability but mechanical impact stress factor should be considered comprehensively to design optical parts.
Fluid mechanics principle about manufacture technology of micro lens generated on needing positions
Jian Wu, Yang Yang, Kuanxin Yu, et al.
In this paper a new technology of optic micro lens generated on needing positions is proposed. It is formed directly on positions where the mocro-lens is mounted. The technique is easy, quick and cheap. It has application prospects in astronavigation, military affairs, biology, chemistry and civil affair. In this paper fluid mechanics principle about the optic micro lens generated on needing positions is researched. A surface equation set of optic glue drip, which spreads on horizontal plane under surface tention, is given. The equation set reflect relations between coordinates of the surface curve. A numerical calculation method of the equation set is proposed. Some shape curves and curvature radius curves for different character parameters of the glu drip are given. Influences on shape of the micro lens through mixing nanometer quartz powder in the glue drip and milling the glass are discussed.
The distortion analysis and correction of two-dimensional scanning system in laser differential confocal microscopy
Chao Gao, Dali Liu, Weiqian Zhao
Laser differential confocal microscopy (DCM) is widely applied to many fields as an important analysis and measurement approach for its high-resolution imaging capability and unique section imaging capability. Differential confocal microscopy needs a scanning system to achieve the imaging due to its zero-field imaging property. So twodimension vibrating mirror scanning system with fast-speed positioning and high response frequency is wildly used for fast speed scanning system. . However, the two-dimension vibrating mirror scanning system may bring the distortion to the image. Therefore, a mathematic model of the distortion for two-dimension vibrating mirror scanning system is built in this paper. And an inverse function method for correction is put forward and the corresponding theory simulation has been done using MatLab. The proposed method can be operated easily and understood easily, and can be applied to large-scale calculation correction, which can provide an effective way to correct the distortion of two-dimension vibrating mirror scanning system.
Planar alignment sensor based on Rayleigh interference in two wavelengths
Yao Hu
Precise alignment of planar optical element is common in industry or scientific research. In this paper, a planar alignment sensor based on Rayleigh interference in two wavelengths is proposed. Monochromatic probing lasers in two wavelengths point normally to the two mirror-reflection planes, and the reflective beams carrying alignment information are focused by a lens to form Rayleigh interference patterns at the focal plane. Four-quadrant detectors pick up the patterns and output angular and coplanar adjustment signals according to the rotational-symmetry and axial-symmetry of the pattern. Preliminary experiment demonstrated the feasibility of the method.
Design and experimental research on miniature fiber-optic displacement sensor
Fei Gao, Jun Yang
A detecting method based on Fizeau interferometer for fiber-optic displacement sensing is presented to detect highprecision displacement in nanometer scale. On the basis of optical interferometry and common-path Fizeau interferometer, micro displacement can be detected by accurately measuring the distance changes between the surfaces of fiber-optic collimator and measuring mirror. Its characteristics are as follows: with common-path interferometer, dependence of energy transmitting fiber to ambient temperature is eliminated, then the effect of ambient temperature variation to the system is reduced; with the method of phase generated carrier modulation/demodulation instead of electric-control phase modulator, the optical path is formed with all-fiber components to improve the application flexibility in the system; by micro fiber-optic collimator with diameter of 1mm, the overall dimension of the displacement sensor is greatly reduced, which makes the use of the sensor more flexible. In the paper, the structure and parameters of miniature all-fiber common-path fiber-optic displacement sensor is studied, the experimental platform for high-precision displacement calibration is established, and a series of performance tests are completed. Experimental results show: with the working distance of 0-14mm, the measuring resolution of the miniature fiber-optic displacement sensor can reach 20nm, and the measuring dynamic range can get 116.9dB, which indicate that the miniature fiber-optic displacement sensor has superior performances with high resolution, high precision and large dynamic range.