This PDF file contains the front matter associated with SPIE Proceedings Volume 10742, including the Title Page, Copyright information, Table of Contents,Author and Conference Committee lists

Harris designed and manufactured a 1.5 meter diameter Corning ULE mirror assembly that is 1/3 scale of a 4 meter monolithic mirror design for NASA’s Advanced Mirror Technology Development program in order to mature the lightweight mirror technology needed for a large space qualified UVOIR mirror so that a viable mission can be considered for the 2020 Decadal review. This mirror assembly was examined using X-rays computer tomography for cross sectional views to detect any manufacturing defects. The mirror assembly was tested for thermal stability at room temperature down to 240 degrees Kelvin, followed with modal test in order to correlate to FEM models.

The Advanced Mirror Technology Development (AMTD) project is in Phase 2 of a multiyear effort initiated in Fiscal Year 2012 to mature toward the next technology readiness level critical technologies required to enable 4-m-or-larger monolithic or segmented ultraviolet, optical, and infrared (UVOIR) space telescope primarymirror assemblies for general astrophysics and ultra-high-contrast observations of exoplanets. As part of AMTD II, a free-free modal test was performed of a light weighted slumped 1.5 m mirror made of Corning Ultra Low Expansion (ULE^®) material. The test article and support structure were suspended via bungee to simulate a free-free environment. Modes were excited by roaming an instrumented modal test hammer and responses were measured. Predicted and measured frequencies are presented as well as Modal Assurance Criteria (MAC) results to compare the mode shapes. The finite element mirror model used for pre-test predictions and posttest comparisons was provided by the mirror vendor, Harris Corporation. The mirror FEM included deformations of the ribs that were a result of the slumping process. Modal test frequencies matched predictions within the 5% target with the exception of one mode and that pair differed by 5.2%. Of the seven modes measured and predicted, four had MAC values meeting the target of ≥ 0.90, one was just under and two were notably below the target.

Cordierite ceramics have excellent physical properties such as a high elastic modulus, low bulk density, high thermal conductivity and low coefficient of thermal expansion (CTE). These features make cordierite ceramics attractive materials for ultra-lightweight and thermally-stable components used in changing thermal environments. Thus, cordierite ceramics have been widely used in ground-based precision systems, but have not yet been applied to space missions. Their resistance against the space environment must first be demonstrated in order to apply these materials to space missions. One of the main issues in the space environment is the deterioration of materials induced by space radiation. The electrons and protons trapped around Earth and having energies of several MeV to tens of MeV cause ionization inside materials. Long-term radiation exposure may induce changes in physical properties, leading to degraded performance. This study evaluated two cordierite ceramics and a SiAlON ceramic for the changes in key physical properties (i.e. Young’s modulus, CTE) induced by radiation as compared with traditional low CTE glass materials. The irradiation test conditions of 10 MeV energy and 2.5×10¹⁶ /cm² total fluence were set by assuming the worst-case condition for operation on geostationary orbit (GEO) over a 20-year period. The total fluence was irradiated in several divided doses, and the changes in physical properties were evaluated relative to increases in irradiation dose. As a characteristic result, the cordierite ceramics showed virtually no changes in terms of Young’s modulus and CTE, while all the compared glass materials gradually showed an increase in CTE in line with increases in irradiation dose. This result indicates that the cordierite ceramics have superior radiation resistance in terms of the stability of physical properties as compared to the low CTE glass materials.

Cordierite ceramics have excellent physical properties such as high elastic modulus, low bulk density, low coefficient of thermal expansion (CTE) and excellent long-term stability. Due to these excellent features, cordierite ceramics have been widely used as highly stable structural components in precision metrology fields or semiconductor manufacturing systems. And given their excellent radiation resistance and pore-less surface that can be mirror-finished, cordierite ceramics should also be excellent as optical materials for ultra-lightweight and thermally stable space optics. However, such an application as optical material requires not only superior material physical properties but also excellent machinability for optical polishing. In light of the few examples of applying cordierite ceramics to optical mirrors, there are few reports on the polishing characteristics of cordierite ceramics. Therefore, this study examined the polishing characteristics of cordierite ceramics in order to clarify the polishing conditions suitable for cordierite ceramics used for space optical applications. The polishing processes were evaluated in terms of removal rate, figure accuracy and surface roughness by changing the polishing parameters. Using the best combination of polishing parameters, we achieved a high figure accuracy of less than λ/20 RMS (λ = 633 nm) and high-quality surface roughness of less than 1 nm RMS within a commercially reasonable polishing time.

We present a systematic study investigating yttria dopant concentrations effects on crystal phase compositions of zirconium dioxide (ZrO₂) and the respective bulk optical properties. (ZrO2), a traditional structural ceramic possesses excellent mechanical properties, while simultaneously possessing a wide band gap (5-7eV). This combination of properties opens the door for designs and fabrication of transparent structural ceramics. We use Current-Assisted Pressure Activated Densification (CAPAD), to achieve high heating rates, and comparatively short hold-times, which leads to ceramics with very fine grain sizes. This affords the opportunity to investigate, the effects of yttria dopant concentration on the resultant microstructure (grain size, phases and phase ratios).

As a high refractive index material, silicon is widely used for infrared thin-film coatings. However, the absorption of silicon films is relatively high, especially in the near infrared region with wavelengths less than 1.8µm. In this paper, we investigated the effect of post-deposition annealing on the microstructure and optical properties of silicon films. Silicon films were deposited by electron beam evaporation and then annealed in air within the temperature range from 200 to 600 °C. The films were characterized by X-ray diffraction(XRD), Raman spectroscopy, electronic-spin resonance(ESR), and optical transmittance measurement, respectively. The optical constants of the films were obtained by the simulation of transmission spectra. It was found that all the silicon films maintained amorphous in microstructure, but, with the increase of temperature, the amorphous network order was improved on both short-range and medium-range scales. When samples being annealed at 400°C, the defect density decreased to the minimum, about one fifth of the as-deposited samples. Meanwhile, extinction coefficient also fell to the minimum, and then increased by rising the annealing temperature further. These results showed that post-deposition annealing could reduce optical absorption of silicon films remarkably in the near infrared region, so as to improve the optical performance of the silicon films.

We have developed a SWIR (Short Wavelength Infrared) optical system for surveillance. The focal length of the optical system was 300 mm for a 640x512 pixel detector. The spatial resolution of the optical system has been designed less than 0.05 mrad. We have measured the spatial resolution to verify the optical performance. Also, we have observed a 2- cycle target at 3 km distance when the visibility was 1.7 km in the field test. We have proved to be able to get the image of a target by using our optical system with a SWIR detector in 1.5 times longer distance than the visibility range.

China has started to develop its geostationary meteorological satellites and associated ground application systems since the 1980s. In the past 20 years, 6 FY-2 satellites were launched and put into application. About 10 years ago, China had planned to develop a new generation geostationary satellite, and the first one, named FY-4A, was launched on December 11, 2016. The Advanced Radiation Imager, one of the observing instruments onboard FY-4A meteorological satellite, has 14 optical channels with the spectral range cover from 0.45µm to 13.8µm. Five kinds of optical coating components, including high reflectance mirrors, dichroic beam splitters, lens, optical windows and bandpass filters, are used to construct the complex optical system. Metal and dielectric thin film materials are selected to design and fabricate these optical coatings. The spectrum measurement, reliability tests and simulated space environment tests are carried out, respectively. The images received by ground station indicate that optical coatings are competent to the application of Advanced Radiation Imager.

A novel method of projecting a reference axis in space for use in optical assembly of centered elements such as assembly in a barrel or in cementing multi-element lenses is presented. An axicon grating, a set of concentric, uniformly spaced circles, when illuminated with a point source of light creates a line of bright spots surrounded by concentric rings in both transmission through, and reflection from, the grating. This axis is easily interrogated with an autostigmatic microscope to gauge the distance a center of curvature, or other lens conjugate, lies from the axis created by the grating.

Optical devices are extremely important since they play a critical role in optical recording and display. Single point diamond turning is one of the most common methods to create plastic optics. Diamond turning of plastics is influenced by a wide variety of factors such as the glass transition temperature of the polymer, other material properties and operator controlled cutting conditions. Since diamond is one of the hardest materials in nature and polymers are relatively soft, little tool wear is expected. But the optics industry claims that tool wear is a major problem. Most of the optical industry uses Poly (methyl methacrylate) (PMMA) and Polycarbonate (PC) for creating optics. The objective of this research is to optimize machining parameters (such as feed, depth of cut, cutting speed and rake angle) to produce optical surface quality (RMS Surface finish < 10 nm) while minimizing tool wear for the two materials. A wide range of experiments were performed on the two materials by varying machining parameters and measuring worn tools using the Electron Beam Induced Deposition (EBID) technique in the Scanning Electron Microscope (SEM). In the experimental conditions used, PMMA was found to have better surface finish than PC when machined with a zero-rake angle diamond tool. Polycarbonate was found to wear the tool more than PMMA under similar cutting conditions. It was also found that Polycarbonate is more sensitive to chip management and chip geometry than PMMA. Detailed effects of all machining parameters for the two materials were studied.

Ductile mode grinding is a finishing process usually being applied to generate molds in brittle materials (e.g. tungsten carbide) to be used for precision glass molding (PGM). To that aim, ultra-precision machineries (UPM) are applied controlling depth of cut not to exceed a critical value, h_cu,crit (e.g. 160 nm for tungsten carbide).

Recent process analyses of the ductile mode grinding process of brittle materials have demonstrated that the critical indentation depth h_cu,crit, that determines the transition from brittle mode to ductile mode removal, can significantly be shifted to higher values by adjusting process parameters such as the type of coolant and its pH value: e.g. for tungsten carbide up to 1600 nm and for BK7 glass up to 350 nm depth. This paper reports on a feasibility study to extend the process window of ductile mode material removal. Applying optimized ductile process parameter sets, enabling values of the critical depth of cut larger than 1 micron, single point diamond turning (SPDT) of binderless tungsten carbide molds has been successfully tested applying UPM machineries.

Experimental data will be presented demonstrating that by controlling and adjusting ductile process parameters only, it is possible to extend its process window into regimes that are today not yet machinable: binderless tungsten carbide molds for precision glass molding have been processed in a ductile removal mode by SPDT generating surface roughness levels of less than 2 nm rms.

An analysis of the adjustment of the critical process parameters will be presented together with a detailed description of the First Light experiments towards SPDT of binderless tungsten carbide molds.

Ductile mode grinding is usually applied for finishing of e.g. tungsten carbide molds used for precision glass molding (PGM) by controlling depth of cut on feed controlled machines.

Bifano et all. demonstrated the possibility to apply this mechanism while machining hard and brittle materials by the use of ultra-precision machines (UPM). Based on experimental investigations a formula for the transition from brittle to ductile cutting mechanism, also known as the critical depth of cut hcu,crit, relating the material specific properties Young’s-Modulus E, material hardness H and fracture toughness KC was developed and is widely used for setting up UPM machines ever since.

However, the influence of cutting conditions, like tool or process characteristics, are neglected leading to discrepancies of the value of hcu,crit between the prediction and the actual machining results of up to 200%. Furthermore, previous investigations have shown that hcu,crit strongly depends on coolant fluid characteristics as well as on the compressive stress applied into the cutting zone by the use of tools with e.g. negative rank angles.

In this paper, we report on a ductile grinding process analysis applying the “three wagons method”, a recently developed method for process optimization in optics fabrication. Following that trail, critical process parameters have been identified determining the process window of feed controlled ductile grinding applied on State-of-the-Art UPM machineries. The influences of the critical process parameters on the critical depth of cut hcu,crit have been tested experimentally using an ultra-precise SPDT machine.

Among others, four critical process parameters could be identified determining the transition between brittle and ductile mode grinding: the critical depth of cut depends substantially on (a) the type of coolant used, (b) the pH value of the coolant, (c) the tool tip radius of the applied diamond and (d) whether ultrasonic assistance (US) is being switched on or off. Depending on the applied set of process parameters and for the experimental data collected, maximum ductile mode material removal rates could be achieved with hcu,crit, max = 1600 nm.

That way, a new formula was developed, which allows the prediction of the critical depth of cut depending on critical process parameters, a.o. tool parameters and cutting fluid characteristics, while machining binderless nanocrystalline tungsten carbide molds. This formula was set up based on fundamental ruling test results and is one step towards extending Bifanos formula taking the influences of critical process parameters into account.

Precision glass molding is an established replicative manufacturing technology for mass production of glass optics. However, compared with injection molding of polymer optics, the production costs are still high, mainly due to longer cycle time. Two scale-up strategies of glass optic production can be applied to reduce the production costs per lens, namely multi-cavity molding and wafer scale molding. However, the efficiency of these two scaling strategies depends on a variety of factors. It is complicated to determine which scaling strategy should be used for the serial mass production of glass optics. In this study, the two scaling strategies will be introduced at both the technical and the economic level respectively. At the technical level, the molding environment, manufacturing accuracy, suitable lens geometries, and the technology readiness level of two scaling strategies will be compared. On the economic level, the productivity and production costs will be analyzed in detail. The goal is to develop a guideline for industry partners, which can be applied to determine the optimal scaling strategy. Furthermore, the concept of digitalized glass optics production, which is established by Fraunhofer IPT, may offer more potential to the scaling of glass optics compared with conventional optics production.

This research is focused on the link between manufacturing parameters and the resulting mid-spatial frequency error in the manufacturing process of precision optics. This second publication focuses on the parameters and the simulation of the grinding step. The Goal is to understand and avoid the appearance of the mid-spatial frequency error and to develop a simulation which can predict the resulting mid-spatial frequency error from a manufacturing process.

Grinding processes are usually set up experimentally, product-specifically and iteratively. The selected parameters are often based on empirical values, whereby the user can set very different parameters and achieve similar results.

In 2017, the so called “grinding process validation approach” (gPVA) was introduced to determine suitable parameter windows. The method allows the definition of parameter windows for grinding tools and materials. Parameter adjustments for optimum results are possible due to the experimentally determined dependence on specific chip volume and tool pressure.

The system was originally developed to describe brittle grinding processes on standard grinding machines. Tests on an ultra-precision lathe provide process parameter data on ductile mode machining of tungsten carbide using UPM machines. This paper reports on gPVA being applied to transfer the ductile machining process from UPM machineries to a standard CNC grinding machine.

Fluid jet polishing (FJP) is a versatile method used for polishing small and complex components. The unstable removal function which is caused by the pulsation of turbulent jet is one of the main limitations for FJP. In this paper, this problem is addressed by a novel shear thickening FJP method. The shear thickening fluid (STF) is employed for preparing the polishing slurry instead of conventional Newtonian fluid. The principle of shear thickening FJP is present based on analyzing the behavior of STF under the special shear rate distribution. Then the influence of the shear thickening behavior on the material removal rate and the surface roughness of UBK7 components is investigated. The performance of the shear thickening FJP is verified detail by experiments. It is found that the shear thickening behavior would be beneficial to the surface accuracy of workpiece, owing to its ability of reducing the turbulence intensity in the boundary layers of fluid jet. Compared with normal FJP, the surface roughness of polished parts could be improved more than 40% in shear thickening FJP, while maintaining the material removal rate.

As aircraft design advances, the requirements on the aerodynamics of such aircraft become much more stringent. The use of conformal windows on such aircraft enables better aerodynamics by eliminating the need for protruding sensor packages, thereby reducing the aerodynamic drag across the airframe. However, manufacturing conformal windows to optical specifications is difficult due to the extreme freeform shapes required for these aerodynamic design forms. Optimax has developed a robotic form correction platform designed specifically to manufacture extreme freeform optical surfaces over large areas.

This presentation will outline the manufacturing process by which a 330 mm square conformal window was created with 123 mm of sag, 98 mm departure from a best fit sphere, and a nominal 23 mm thickness. The surface specification was given as <0.5 μm RMS surface irregularity over the clear aperture. Fiducials were designed into the part to ensure accurate form generation and measurement.

Both sides were generated and the fiducials created using a commercial 5-axis ultrasonic grinding machine. The initial fiducials were determined to be inadequate and resulted in excessive and unrepeatable tilt in subsequent measurements of the generated surfaces, new fiducials were created, resulting in tilt less than the measurement uncertainty of the CMM used for the metrology. After generation, a custom robotic form correction platform based off of an industrial 6 degree of freedom robotic arm was used to polish both surfaces.

Ductile grinding offers several advantages over conventional approaches with grinding and polishing. Ductile grinding is usually carried out on Ultra-Precision-Machines (UPM), e.g. for the production of press molds. However, the machining volumes for ductile processes are limited and UPM are usually not suitable for high volume removal by brittle machining. Therefore, the pre-machining often takes place on conventional CNC grinding machines.

In this paper, we publish first results on ductile machining of tungsten carbide dies on a standard CNC grinding machine.

This approach enables the pre-machining and finishing of tungsten carbide dies in one machine, in one clamping with the same tool.

In order to find out the law how the nozzle height influences the removal function in FJP, a mathematical model of the nozzle-rotating removal function is proposed and its correctness has been verified by experiment. Moreover, another model which is able to predict the surfaces processed by different removal functions is established in this paper. The calculation results show the profile of nozzle-rotating removal functions change from W-shaped to single peak Gaussian shaped as the nozzle height increases. Besides, when the removal functions are Gaussian shaped, the best surface roughness is obtained when the removal function is the widest and shallowest one. Which has theoretical significance for the optimization of the process parameters in actual processing.

The slurry of fluid jet polishing mainly consists of deionized water and abrasives. Material removal is mostly regarded as plastic removal by the strike of the abrasives on the workpiece surface. Since jet pressure is relatively low, which result in a low material removal rate and bring a limitation of applying to this processing method. To improve the material removal rate of glass (Fused Silica, UBK7, K9, etc.), alkaline slurry was used to enhance chemical effects during polishing. Firstly, the material removal of conventional neutral slurry (pH≈7) and the new alkaline slurry (pH≈10, 11, 12, 13) were compared and the results showed that alkaline slurry brought an obvious increase in material removal rate. Then, four kinds of slurry of different alkalinity (pH≈10, 11, 12, 13) were used in polishing experiments to make clear the influence of alkaline intensity on the material removal rate. It was found that a larger material removal rate would be obtained with a higher pH slurry. Finally, the surface roughness which were made by slurry with different alkalinity were also compared, the results reached as that slurry with higher pH could bring lower surface roughness. It could be drawn from this study that enhance the chemical effects in fluid jet polishing could be an effective way to enlarge the material removal rate and improve the processing performance.

Successful fabrication of optics across multiple vendors and countries requires simple communication techniques. Drawing standards have been used across the optics industry in the United States since the 1960s with the implementation of MIL-STD-34 and subsequently ASME/ANSI Y14.18M. Though both standards are now inactive, designers and fabricators continue to use either these standards or modified versions of these standards. Concurrently, much of the international community has moved towards implementing ISO 10110 since the late 1990’s. As standards development efforts continue for optics and photonics in ISO/TC 172 to improve global standardization, understanding how to read and interpret these standards, and notably the optical drawing standard ISO 10110, is critical. This paper discusses how to interpret a single drawing across traditionally-used standards within the United States. Deconstructing the basics of the three standards mentioned allows designers and fabricators to communicate in a single language. Understanding the history and development of optical standards and how they relate can help ease the transition to a single international standard for optical engineers and fabricators within the United States.

Precision glass molding is a viable process for the cost-effective volume production of freeform optics. Process development is complex, requiring iterative trials of mold manufacture and metrology, glass mold prototyping, metrology and functional testing. This paper describes the first iteration in the development of a process for an Alvarez lens for visible light. The challenges of this optic are extremely tight band-RMS tolerances on a freeform shape over a maximum clear aperture of 45 mm, a 16:1 aspect ratio and a freeform departure of 329 micrometers. A freeform glass mold for an Alvarez lens was manufactured by coordinated-axis diamond turning in a mold substrate using a custom tool error correction method. The results of prototype precision glass molding are also reported. Mold surfaces and molded optical surfaces are analyzed with scanning white light interferometry. A surface roughness of approximately 3 nm RMS is obtained for both the mold substrate and the glass optic with high-fidelity reproduction of micro-surface structure in the glass. These measurements also identify challenging areas, particularly the presence of mid-spatial frequency errors on the optic originating from the machine thermal control system. The form of the molds was also measured with a profilometer; however, the mold surface does not agree with the expected prescription with an overall deviation in form of approximately 10 μm. The machining process is expected to have sub-micrometer error and the sources of this discrepancy are still being determined. Metrology of the glass optics is currently in progress.

Fraunhofer IPT has developed an innovative software concept for a digitalized glass optics production by means of precision glass molding and the belonging process chain. Thus, production data is used comprehensively and can be exploited conveniently for process development, production ramp-up and serial production. One striking innovation is the possibility to run part-specific simulation leading to a “Digital Twin” of every lens produced. The benefit for business is to enable advanced process developments, acceleration of production ramp-up and improved productivity in serial production. The concept is briefly introduced in conjunction with the current development state. Three possible use-cases for digitalized optics production are given and the paper concludes with further development steps necessary to implement the concept.

Chemical-mechanical polishing (CMP) of optical glasses is widespread and forms the basis for many high-precision polishing processes. The pads, slurries and glass materials used in polishing have many different properties. The effects of these properties on the process results are often unknown. The right choice and combination is therefore often a challenge.

By means of a plan processing of N-BK7 and SF56 samples by a plan-polishing process, the influence on the process results, material removal rate (MRR), micro roughness and cleanliness caused by slurry and polishing pad is shown. It turns out that the type of polish pad has the biggest impact on the results. The easy-to-process material N-BK7 shows only little influence by the type of slurry used. The more challenging SF56, however, shows significant effects, especially in the area of the resulting micro roughness and the appearance of surface damages like orange peel. Especially the use of Auerpol® PZ500 shows clear advantages here.

For a selection of three out of nine polishing pads, the effect of density variation of the slurry was also investigated. Lower particle concentrations lead to lower material removal rates. This applies to both materials. The more sensitive SF56 shows a reduction in micro roughness by the use of a less dense slurry.

The correct selection of the polishing pad has a positive effect on the material removal rate and/or the micro roughness in all tested materials. An adaptation of the type and concentration of the slurry is especially important for more sensitive materials and in combination with the right polishing pad.

In view of the development towards special materials and small lot sizes, the targeted and correct selection of polishing slurries and pads becomes more and more important. The information required for this purpose on the behavior of the pads and slurries available on the market must therefore first be determined in a targeted manner and clearly presented.

Transverse translation-diverse phase retrieval (TTDPR), a ptychographic wavefront-sensing technique, is a viable method for optical surface metrology due to its relatively simple hardware requirements, flexibility, and high demonstrated accuracy in other fields. In TTDPR, a subaperture illumination pattern is scanned across an optic under test, and the reflected intensity is gathered on an array detector near focus. A nonlinear optimization algorithm is used to reconstruct the wavefront aberration at the test surface, from which we can solve for surface error, using intensity patterns from multiple scan positions. TTDPR is an advantageous method for aspheric and freeform metrology, because measurements can be performed without null optics. We report on a sensitivity analysis of TTDPR using simulations of a freeform concave mirror measurement. Simulations were performed to test TTDPR algorithmic performance as a function of various parameters, including detector SNR and position uncertainty of the illumination.

The point diffraction interferometer (PDI), emerging spherical wave used as the reference wave, is one of potential wavefront testing tools with very high accurate. However, it is not feasible in the in situ measurement of the surface error in the polishing process. For the test mirror with low reflectivity, the poor fringe contrast would be formed. It could increase the phase noise, which can’t be removed during phase retrieval, thus limiting the measurement accuracy. Therefore, the polarization point diffraction interferometry (PPDI) with even aspheric quarter-wave plate (EAQWP) is proposed for high-precision testing of the high-NA spherical mirror. The EAQWP is employed in the PPDI to transform the polarization states of the test and reference beams, then a good fringe contrast can be realized by adjusting the relative intensities of two interfering waves. Compared with the common quarter-wave plate (QWP), the substrate configuration of designed even aspheric surface reduces significantly the introduced wavefront distortion for large-NA measurement, at the same time, allows to use the same position and orientation of the EAQWP for testing mirrors with different NAs, which facilitates the system alignment in practical optical shop testing. Most importantly, the corresponding pose errors are corrected by computer-aided alignment with a difference restoration model. The viability of the new method and system are verified with an experiment for testing a spherical mirror with 0.04 reflectivity and 0.5 NA, and with a ZYGO interferometer match.

A new calibration method is proposed to separate the profile error caused by the sphericity of the scanning stylus in 3- dimensional contact profilometry. To reduce uncertainty in surface profile measurements, compensation of the stylus sphericity has become a critical issue. In optical flat testing, the three-flat method, which can separate the reference error from the measured deviations, is well known. Although there are also several methods of calibration of the stylus sphericity in contact profilometry, to extract the error precisely remains a challenge. Here we consider a new algorithm for this that uses four measurements including new combinations of the two styluses. The algorism yields four deviation data of the sum of the object profile and the stylus sphericity. With this method, we can extract the surface profile, while keeping the stylus error minimum.

Nowadays the strict quality criteria for modern optical products lead to the use of the point contact processes for grinding and polishing. This art of manufacturing is especially sensitive to the occurring of the mid spatial frequency structures, which influence negative the optical properties of the lenses. Mid spatial frequency errors are too small to be eliminated as a form error, and too big to be polished away. The manufacturing chain consists of numerous steps. Finally, different mid spatial frequency errors commingle together and it is a difficult task to assign them to the proper process step. In the article we discuss the possibilities to analyze surfaces direct after grinding.

Deflectometry is a metrology method able to measure large surface slope ranges that can achieve surface reconstruction accuracy similar to interferometry, making it ideal for freeform metrology. While it is a non-null method, deflectometry previously required a precise model of the unit under test to accurately reconstruct the surface. However, there are times when no such model exists, such as during the grinding phase of an optic. We developed a model-free iterative data processing technique which provides improved deflectometry surface reconstruction of optics when the correct surface model is unknown. The new method iteratively reconstructs the optical surface, leading to a reduction in error in the final reconstructed surface. Software simulations measuring the theoretical performance limitations of the model-free processing technique as well as a real-world test characterizing actual performance were performed. The method was implemented in a deflectometry system and a highly freeform surface was measured and reconstructed using both the iterative technique and a traditional non-iterative technique. The results were compared to a commercial interferometric measurement of the optic. The reconstructed surface departure from interferometric results was reduced from 44.39 μm RMS with traditional non-iterative deflectometry down to 5.20 μm RMS with the model-free technique reported.

One of the most used methods to measure the quality of optical surfaces by light transmission is the de ectometry. To implement this technique, an arbitrary ray selector is used to choose some incident rays. Measuring the intersection of the rays refracted by the surface, in a posterior detection plane perpendicular to the optical axis, the normal at the surface under test, it is determined. Whith measurement points, the shape of the surface is determined by their integration. The process is simple if the incident rays are chosen in a called null configuration, since it is expected that all refracted rays will strike a predetermined ordered array in the detection plane. To numerical calculation we using an ideal surface on this test. In order to full measuare of the surface on simulation, we used vector form of exact ray tracing. To carry out the necessary numerical simulations for a null screen, we considering a point light source and the selector placed in arbitrary position between the point source lens of the test. Some numerical simulations are shown and are compared with experimental results.

The primary mirror (M1) of Thirty Meter Telescope (TMT) consists of 492 segments of which, 86 are ground and polished by India-TMT. These segments are off-axis and aspheric in nature and one of the effective methods to polish such segments is through Stressed Mirror Polishing (SMP). During SMP, consistent in-situ metrology of the surface is needed to achieve the required profile. A 2D Profilometer (2DP) will be used by India-TMT for the low frequency profile metrology. The 2DP is a contact-approach metrology, consisting of probes positioned in a spiral pattern, measuring the sag of segment surface. Initial section of this paper deals with the sensitivity and tolerance analysis of the 2DP. This is followed by the study on position and rotational errors of the 2DP as a whole. Simulation of these analysis is carried out initially on a sphere and then on different segments of the TMT, in order to study the induced measurement errors.

A new data processing method based on orthonormal rectangular gradient polynomials is introduced in this work. This methodology is capable of effectively reconstructing surfaces or wavefronts with data obtained from deflectometry systems, especially during fabrication and metrology of high resolution and freeform surfaces. First, we derived a complete and computationally efficient vector polynomial set, called G polynomials. These polynomials are obtained from gradients of Chebyshev polynomials of the first kind – a basis set with many qualities that are useful for modal fitting. In our approach both the scalar and vector polynomials, that are defined and manipulated easily, have a straightforward relationship due to which the polynomial coefficients of both sets are the same. This makes conversion between the two sets highly convenient. Another powerful attribute of this technique is the ability to quickly generate a very large number of polynomial terms, with high numerical efficiency. Since tens of thousands of polynomials can be generated, mid-to-high spatial frequencies of surfaces can be reconstructed from high-resolution metrology data. We will establish the strengths of our approach with examples involving simulations as well as real metrology data from the Daniel K. Inouye Solar Telescope (DKIST) primary mirror.

Virtual reality and augmented reality devices require increasingly demanding optical components. Head mounted displays for VR systems often use molded Fresnel lenses, which can be affordably mass produced, maintain low weight, and still achieve high optical performance. Here, we describe an optical system designed for a wide field-of-view, consumer VR headset. Custom tooling was fabricated via diamond turning in order to injection mold the acrylic lenses. Each optical channel is composed of two lenses. The lenses have a spherical-convex surface and an aspheric-convex Fresnel on a spherical-concave surface; the radii of the spherical surfaces differ between the two lenses. Each lens pair relays the image from a compatible smartphone to the eye. To assess the quality of the lenses, the surface finish and surface profiles were measured using a white light interferometer and a contact profilometer, respectively. The lenses were assembled into a custom headset, and their performance was demonstrated via commercial VR software.

The present work shows the characterization of a transmissive spatial light modulator (SLM) trademark CRL-Opto and model XGA2L11. This modulator will be used as a variable retarder to generate different polarization states which are produced when the different gray levels from 0 to 250 are displayed in the SLM. So, it is important to determine its response and linear range of work, these parameters were determined experimentally. For this, the SLM was tested with four different wavelengths: red (633 nm), orange (612 nm), violet (405 nm), and green (550 nm). For doing this, the SLM was placed between two linear polarizers aligned first in parallel and then in perpendicular form. The gray levels were varying uniformly from 0 to 250 with increments of 10 in gray levels, and the gray levels were displayed over all the pixels of the SLM. The different intensities for each gray level were measured with a Thorlabs detector model PM100A. Finally, we show the results obtained for each wavelength where we found out that the best linear response was for the green laser with a wavelength of 550 nm.

Surface defects evaluation system (SDES) works on the principle of microscopic scattering dark-field imaging (MS-DFI) and takes the criterion board as reference for calibration. Unfortunately, for criterion board with rectangular section scribed lines, image width of narrow lines doesn’t follow the linear law, making it confusing to get real width. Besides, other criterion board except with rectangular section scribed lines in a flat plane is difficult to fabricate, which limits measurement accuracy and extensive use of SDES. In this paper, a 3D simulation model is established to simulate scatter light distribution induced by surface defects. The interactions between the incident light and surface defects in near field is calculated with the help of Finite-Difference Time-Domain (FDTD) method, a kind of Maxwell’s solver. Skills as rotation and incoherent summation are applied to obtain results under illumination of unpolarized, broad-spectrum natural light sources in uniform annular layout. Finally, near to far field projections based on vector diffraction theory is carried out to get scatter light intensity distribution in far field. The data is also post-processed by scripts to describe imaging process simplified by a lens system so that it can be compared to experiment images. The 3D simulation model reveals MS-DFI process theoretically and may help to interpret image width of surface defects. The establishment of the 3D imaging model is an attempt to overcome the limits of the criterion board and is expected to provide reference for calibration for wider applications of SDES.

The Scanning Long-wave Optical Test System (SLOTS) is a slope measuring deflectometry system that provides accurate measurements on ground surfaces. As it uses a thermal source, we can measure an optic during the grinding phase which allows us to correct figure errors when material removal is much faster. We have made improvements in SLOTS, such as the step-and-stare method, the ceramic rod, and the Gaussian fitting processing software, so that this system supports higher accuracy and resolution. As a result, SLOTS is an optical testing system that covers a huge portion of the fabrication process from the grinding to the figuring. It is a complementary solution for other metrology systems such as the laser tracker, SCOTS, and null interferometry. SLOTS can reduce the manufacturing time by producing ground aspheres that have low errors of the surface figure when polishing begins.

IR sensors continue to be a powerful tool for a broad range of sensing applications including night vision, surveillance and other mission functions. Sensors are often exposed to challenging scenarios such as targeting under extreme conditions including detection under extremely high temperature and speed, such as in hypersonic applications. Thermal protection is vital for sensor performance under unfavorable conditions. Transparent ceramic is one of the window materials used against thermal impact due to its excellent optical transmission, transparency, and durability under extreme conditions. In this paper, we focus on investigating the behavior of Aluminum Oxynitride (AlON) optical ceramics at high temperatures. AlON has been reported to have transparency and transmission over 80% from the UV all the way to the mid-wave IR cutting off around 5μm. A 25.4mm × 25.4mm × 6mm square and 1.5mm × 1.5mm × 10.16mm AlON samples were heated up to ~907K. A 50W CO₂ laser was used as a heating source for the material under test (MUT). Significant thermal distribution was measured using a long-wave IR thermal camera to observe the MUT surface. In addition, heating results show that there was severe thermal stress in the MUT. We are currently optimizing the optical beam dimensions and projection shape towards a sample in order to minimize the stress and heat towards 1273K. Finally, we validated our experimental results with thermo-optic simulations and modeling.

This paper introduces a spherical optical surface defects evaluation system (SSDES) based on the dark-field microscopic scattering imaging (DFMSI) method. The specially designed annular illuminant with variable aperture angles ensures the condition of DFMSI for spherical optical components with variable surface shapes and radii of curvature. On account of the small imaging field of view (FOV) of the SSDES relative to the large spherical optical component under test, the scanning path for subaperture images is planned along longitudes and latitudes of the spherical surface to detect the whole surface. Besides, for avoiding the misplaced subaperture images stitching due to the decenter error, a centering system is utilized to perform the alignment of the optical axis of the spherical optics in relation to the reference axis before capturing subaperture images. Then we propose a defect evaluation method, primarily involving the threedimensional (3D) image reconstruction and global coordinate transformation, the projective stitching of 3D subaperture images, and the quantitative evaluation of defects, to process the captured spherical subaperture images. Experiments results are shown in good accordance with the OLYMPUS microscope for the relative error within 5%, and validate the SSDES to the micrometer resolution.

Off-axis reflective optics, due to its no chromatic, no obscuration, small size, compact structure, easy to achieve wide field of view(FOV), high-quality imaging and other features, are widely concerned. In this paper, the conformal ellipsoidal dome of MgF₂ material is used to allay the air resistance and reduce the aerodynamic heating effect of the missile head. The compact off-axis four-mirror is used to realize a conformal optical system of the seeker with medium wave infrared(MWIR)，which the working waveband is 3~5μm, F number is 2, FOV is ±1 degree and the focal length is 55mm. The optics achieve 100% cold aperture efficiency and the MTF value of each field at 17lp/mm is greater than 0.7. It has a working distance of 17.4mm and a sapphire window 14.7mm apart from the focal plane, leaving plenty of room for the refrigerant detector. This system can also meet the high accuracy positioning with imaging quality requirements and ensure light design of the seeker.

Recently there is growing interest to impart individuality and create comfort in premises by wall painting. Proceeding from such the need, we are designing an amateur portable projection device that will allow drawing an image of any complexity on the walls to any person, even if he has absolutely no experience in this matter. The features of the developed device in comparison with the existing projection systems are as follows: 1) a small size (a high degree of compactness); 2) the ease-to-use device; 3) a low cost of the device. Such a compact and relatively inexpensive projection-illumination device will occupy one of the important niches in the design field. In the article several known variants of the structural schemes of the projection device are considered. We propose our own solutions to the functional problem, based on the terms of the technical assignment. Also, the choice of the radiation source is explained and an approximate overall calculation of the lighting part is made with subsequent conclusions. The research of the developed amateur portable projection device application in various types of premises and at various illuminations is carried out. In addition, in the article a possibility of modeling and calculating the illumination of the transparent object by using of various CAE software is considered.

Effective optics drawings clearly communicate requirements. Increases in the globalization of the optical community have forced the United States to consider transitioning to a single worldwide standard. These changes are reflected in both the optical engineering and fabrication community in learning how to understand a complex standard. The knowledge regarding the nuances of past standards and how they relate to the ISO standard is helpful. The basics of the ISO standard appear complex but are partially. built on past optical drawing standards within the United States. Careful study of both US and ISO optical drawing standards is required for a clear and deep understanding of the standards. Individual company based optical drawing standards may seem independent in form from drawing standards, but they are also variations of past US standards. These changes are reflected by moving from standards such as MIL-STD-34, where notes dominate the print, to more modern standards, such as ISO 10110, where all necessary information is left in an internationally friendly coded notation. Working between these two different approaches, a translational method has been developed to assist engineers in this shift. Converting from a notational-based drawing to a coded notation may seem difficult at first but will ease the communication between all parties involved in designing, fabricating, and testing and optical component or assembly.

In this work, we compare two techniques to make point-diffraction interferometers (PDI): microlithography and the mercury drop method to know with which of these the best results can be obtained. For the comparison, we used the wavefront generated by a commercial reference surface of λ/20 analyzing the interference pattern generated by the PDIs, we obtained information from the wavefront generated by the pinhole. Several PDIs were created and analyzed to have a statistical error information of both techniques.

The analysis of polarization evolution in a tunable fiber laser in a ring configuration is presented, an interferometer was used to tune the laser and was manufactured with thin-core fiber (Thin-Core Fiber, TCF). The interferometer was achieved by splicing a segment of thin-core fiber (Thin-Core Fiber, TCF) between two segments of single-mode fiber SMF-28 (Single-Mode Fiber). Single and double and triple line emissions were obtained by means of the angular micrometric deflection in the TCFMI (Thin-Core Fiber Modal Interferometer) interferometer section, as well as depending on the position of the polarization controller plates (PC1 and PC2). Also, a uniform tuning was achieved, depending on the polarization state of the pumping source and the position of the plates of the second polarization controller (PC2), which started at 1534.70265 nm and moved to the left side to 1531.65142 nm and the evolution of the polarization state in this tuning range was observed. A tuning range of 1527.01738 to 1553.66363 nm was also achieved by means of the angular micrometric deflection in the TCFMI interferometer section.

In this work we calculate the effect caused by roughness on the light reflected by an optical surface like a mirror, the numerical calculation is carry out within the Rayleigh approximation. We focus our study in the comparison of the results obtained numerically using different roughness parameters and calculate its effect on the aberrations of the wavefront, which without the effect of the roughness is considered a ideal surface.

We investigated the definition for circular off-axis aspheric mirrors (COAMs). The clear opening of the COAM obtained by projecting a circular aperture on the aspheric surface does not form a plane but a curved surface. To avoid ambiguity due to the non-planar opening, we propose to use a plane to cut the aspheric surface to obtain a COAM. The COAM has three characteristics: 1) an elliptical opening; 2) the major axis of the opening lies on the meridional plane containing the original optical axis of the aspheric surface, and the minor axis lies on the sagittal plane perpendicular to the meridian plane; and 3) it is not deepest at the center of the ellipse. The third characteristic suggests two methods for defining the COAM using a plane: 1) with the center of the elliptical opening as a reference and 2) with the deepest point of the mirror as a reference. All the formulas required to obtain the desired COAM using the two methods are presented.

Precision glass molding, PGM, enables an optics fabrication with a high level of stability and large batch sizes while keeping cost at low levels. This technology is relying on the generation of highly accurate mold surfaces made of brittle materials, e.g. tungsten carbide or silicon carbide. These mold materials are often finished by ductile mode material removal applying ultra-precision machineries (UPM) eventually generating low levels of surface roughness of a few nanometers root mean squared. While the process of ductile mode grinding is usually controlled by keeping tool indentation depths below a so called critical depth of cut hcu,crit, there is no method for predicting or optimizing the level of surface roughness being generated.

In this paper, we report on a process analysis of ductile mode grinding analyzing the influences of critical process parameters on the level of surface roughness being generated for tungsten carbide and BK7 glass. To that aim, the “three wagons method”, a recently developed method for process optimization in optics fabrication was applied. That way, critical process parameters were identified determining the eventual level of surface roughness within the ductile process window of UPM machining. Experiments have been carried out proving that the level of surface roughness generated strongly depends a.o. on the type of coolant used, the pH value of the coolant and the cutting depth h (with 0 < h < _hcu,crit).

Based on the experimental data collected, a formula was developed enabling the prediction of the level of surface roughness eventually being generated by ductile grinding applying UPM machineries. Applying this formula, an optimized set of critical process parameter values has been determined predicting a minimum level of surface roughness on tungsten carbide (CTN01L) by ductile mode material removal of < 1 nm rms; subsequently, this parameter set has been applied experimentally generating Ra = 0.83 nm, a value usually obtained by fresh feed polishing. The developed formula enables a better predictability of level of surface roughness within the process window of ductile mode grinding and is currently being extended to other materials.

According to our studies of polarization-sensitive materials based on azochromophores and polymers in recent years, a factor significantly influencing their photoanisotropic properties has been revealed. The degree of molecular integration of the material components (light-absorbing centers and polymer matrix) is in direct connection with the level of achievable birefringence in media obtained on their basis. This paper considers the results of a study of the integration of polarization-sensitive materials by means of molecular electrostatic forces. Experimental data of the photoanisotropic behavior of optical media based on advisedly designed organic chromophore salts with the participation of almost all alkali metals are shown. Lithium (Li⁺), sodium (Na⁺), potassium (K⁺), cesium (Cs⁺) and hydrogen (H⁺) are used as cations for these polarized light-receiver organic salts, and as an anion, on the other hand, is a residue of functional monoazo dye. The obtained light-absorbing organic salts are doped into the hydrophilic polymer matrix having good lyophilic compatibility. To study the induction of photoanisotropy in the obtained photosensitive materials, we investigate the effect of actinic polarized light on them with wavelengths of 445 nm and 532 nm and variation of reading wavelengths (at 532 nm and 635 nm) depending on the spectral characteristics of the test samples. Optimum parameters of exposure for each composition are determined experimentally. The kinetic curves of the induction of photoanisotropy in the new comparing polarization-sensitive media are shown as light-induced effective photoanisotropy for the various illumination conditions.

In the present study, zinc molybdenum tellurite glasses with the molar composition of (1−x)TeO₂−yMoO₃−xZnO and (1−x)TeO₂−yMoO₃−xZnO, where x = 10, 20, and 30 mol%, and y = 10 and 20 mol%, were prepared by a high temperature melt quenching technique and studied their thermal, thermo-mechanical and mechanical properties. From the thermal analysis, it was found that the glass transition (T_g), crystallization (T_x) and stability parameters slightly increased with increase in ZnO content in both series of glasses. Thermal expansion coefficient decreases from 16.56 to 14.67×10^-6/K as the ZnO content increases from 10 to 30 mol%. Knoop hardness slightly decreases from 307 to 290 kgf/mm2 with increase in ZnO content from 10 to 30 mol% for 10 mol% of MoO3 content, whereas it increases for 20 mol% of MoO₃. Based on the results, it concludes that the number of bridging oxygens and network compactness of tellurite matrix increased with increase in ZnO content varied from 10 to 30 mol%.

Large mirrors with lightweight structure, such as those used in the telescope system of astronomy or spaceborne applications, are susceptible to stress caused by fabrication process. Furthermore, both the residual stress and subsurface damage are critical for the lightweight tooling of glass materials.

In order to figure out the stress distribution on glass substrate, the photoelastic method has been applied to not only the astronomical optics but also the industrial optics of semiconductor equipment. However, there are several influence factors in photoelasticity measurement, including the structure of mirror, fabrication process, and metrology technique. The above factors may affect to the retardation result of photoelasticity measurement and cause the error of stress calculation. Therefore, it is important to clarify the retardation difference contribution to the corresponding influence factors.

In this study, we attempted to use photoelastic instrument to investigate the relationship between the photoelastic effect and stress of several kinds of lightweight mirrors. There are three different lightweight mirrors were adapted to the photoelasticity measurement, including: (1) GSO 12” Mirror with 12 inches diameter made by fused silica, (2) Primary Mirror (M1-B) of Formosat-5 with 450 mm diameter made by ZERODUR^® , (3) Primary Mirror (M1) of Mircrosat with 380 mm diameter made by CLEARCERAM^®-Z. The experimental results depict some obvious retardation differences caused by the certain influence factors and the details will be discussed below.