A switchable virtual reality (VR), augmented reality (AR), and mixed reality (MR) system is proposed using digital optical cloaking. Optical cloaking allows completely opaque VR devices to be cloaked," switching to AR or MR while providing correct three-dimensional (3D) parallax and perspective of the real world, without the need for transparent optics. On the other hand, 3D capture and display devices with non-zero thicknesses, require optical cloaking to properly display captured reality. A simplified stereoscopic system with two cameras and existing VR systems can be an approximation for limited VR, AR, or MR. To provide true 3D visual effects, multiple input cameras, a 3D display, and a simple linear calculation amounting to cloaking can be used. Since the display size requirements for VR, AR, and MR are usually small, with increasing computing power and pixel densities, the framework presented here can provide a widely deployable VR, AR, MR design.

The recent advances in light-The recent advances in light-field acquisition and display systems bring closer the day when they become commercially available and accessible to wide audiences for numerous use cases. Their usefulness and potential benefits have already been disseminated in the field and they started emerging in both industry and entertainment applications. The long-term goal of the scientific community and future manufacturers is to research and develop fully immersive, yet seamless and efficient systems that can achieve the ultimate visual experience. However, certain paths leading to such goals are blocked by technological and physical limitations, and also significant challenges that have to be coped with. Although some issues that rise regarding the development of capture and display systems may actually be nearly impossible to overcome, the potential for light-field applications is indeed immense, thus worth the vast scientific effort. In this paper, we systematically analyze and present the current and future relevant limitations and challenges regarding the research and development of light-field systems. As current limitations are primarily application-specific, both challenges and potentials are approached from the angle of end-user applications. The paper separately highlights the use case scenarios for industry and entertainment, and for everyday commercial usage. Currently existing light-field systems are assessed and introduced from a technical perspective and also with regards to usability, and potential future systems are described based on state-of-art technologies and research focuses. Aspects of practical usage, such as scalability and price, are thoroughly detailed for both light-field capture and visualization.

To design a concave grating for a hyperspectral imaging (HSI) system, it is critical to achieve flat field focusing in both the horizontal and vertical directions on the image sensor. We have developed a generalized automation aberration reduction procedure (ARP) that can be applied in any cases of a concave grating spectrometer. The concave grating, which has a free-form profile with blaze grating pitch and variable line spacing [3], is fabricated using five-axis CNC machine with nanometer machining precision for hyperspectral imaging. In order to evaluate the performance, an optical system is designed and setup to measure the focused spot size, spectral resolution and diffraction efficiency.

Image reconstruction in nuclear medicine produces valuable volumetric data of vital markers in living bodies. Visual scene reconstruction methods, that aim to recreate a scene from camera images, are also continuously improved by the recent advancements of light-fields and camera systems. The parallels of the two fields are increasingly noticeable as we now have the computing power and methods to take into account transparent materials and ray trace the scattering and other effects of lights for visual scene reconstruction. In this paper, we aim to highlight and analyze the similarities and potential synergies of the two methods.

We have proposed an analytical 2D model [1] of a thickness gradient function for thin film deposition of a LVF for order sorting of a diffraction grating using an evaporation chamber. The LVF was fabricated and its thickness profile was measured using a probe-type surface analyzer. This study proposes an innovative method for overcoming the low production rates currently associated with LVF fabrication.

Within the 25% - 75% thickness range, the profile distribution exhibits a high degree of linearity, with R² are greater than or equal to 0.9914 for both the cases. The LVF zone width appears to be a linear function of the mask height h, with R² are greater than or equal to 0.9982 for all the cases. This indicates that the thickness gradient function is a more accurate model for obtaining the thickness profile of an LVF than any other modeling mentioned in previous published results. This study demonstrates that the developed theoretical 2D model can be used to predict accurately the thin film profile of an LVF.

The effective zone width of the LVF is defined as a thickness range of 25% - 75%, which appears to have high degree of linearity as a function of the mask height, h (mask-to-substrate gap). Thus, these results also confirms that the linear variable area increases as the mask-to-substrate gap increases. Thin film layer structures are constructed to demonstrate the efficacy of the proposed LVF design concept. Transmission spectrum result (wavebands 400nm to 1000nm) for varying mask heights at different positions shows maximum number of wavebands with transmittance (>99.9%). Comparison of both the theoretical and the evaporating results matches satisfactorily.

Researchers from the U.S. Army, along with university scientists, are implementing efforts to develop a hyperspectral/broadband and/or ultraviolet (UV) sensing technology for target discrimination. The Army’s primary goal is to advance the development of fast reliable broadband optics techniques that can quickly identify and ascertain an indication of the geometric shape/compositional structure of various materials encountered on the battlefield. Samples of a variety of cement-based, metal, and composite materials are assembled and investigated to determine each sample’s spectra optical reflectance and absorption properties after being exposed to varying optical wavelengths. The optical wavelengths are generated from deuterium, halogen, and white light sources. The light intensity ratios are used to create data points which allowed for the identification of unique characteristics of each sample material. Broadband visible and near infrared (NIR) sources (deuterium and halogen) are reflected off the samples and the spectrometric reflections were captured. Several light intensity ratios are used and compared to distinguish the samples and error bars are created. While the initial results indicated that the halogen source may be used to distinguish most of the sample materials (and perhaps stand-alone versions of the other wavelength sources may not be sufficient), combinations of wavelengths/laser diodes with broadband light sources were used to determine if the identification/characteristics of each sample could be achieved. Results outlined in this paper include the current progress made toward the development of broadband optics sensing methodologies and instrumentation for identifying and discriminating the geometric configurations/formations of various battlefield materials.

The overall chip size is less than half of a SD card. The spectral resolution is 3~5 nm for the whole spectral range of 350~1100 nm. The first order diffraction efficiency reaches over 70% at the blaze wavelength, which is at 550 nm. The signal-to-noise ratio of the SpectroChip system is 1000:1 with 50 ms integration time. The stray light is about 0.04%. A total solution is ready to be incorporated into any smart phone, wearable devices, and handheld device systems. With the incorporation of our SpectroChip sensors, hundreds to thousands items related to personal healthcare can be added to the worldwide health analysis cloud platform.

Graded index (GRIN) optics offer potential for both weight savings and increased performance but have until recently been limited to visible and NIR bands (wavelengths shorter than about 0.9 µm). NRL has developed glass-based IR-GRIN lenses compatible with SWIR-LWIR wavebands. Recent designs show the potential for significant SWaP reduction benefits and improved performance using IR-GRIN lens elements in dual-band, MWIR-LWIR sensors. The SWaP and performance advantages of IR-GRIN lenses in platform-relevant dual-band imagers will be presented.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) Spokane Mining Research Division (SMRD) are evaluating the comparative performances of ground convergence monitoring methods currently utilized in underground mining. A portion of this research is exploring applications of photogrammetry for periodic visual assessment of slow-converging ground. This paper describes the photogrammetric systems evaluated, including their components and methodology. These systems include light-weight equipment easily carried by a single individual traversing rough terrain in underground mine environments. This study demonstrates how photogrammetric methods may complement or replace existing underground convergence monitoring techniques on the basis of time and personnel requirements, equipment cost and robustness, and overall data quality. This research supplements previous studies into photogrammetric and laser scanning methods, and enhances understanding of how digital technology may be utilized to maximize safety in underground excavations. NIOSH SMRD is committed to improving workforce health and safety through innovative research and applications of technology.

In interferometry based metrology systems, the sample’s topography is extracted from the interference phase which is determined by a combination of both the topography of the sample and its reflectance\transmission phase governed by the sample‘s structure and material composition. Since the two contributions cannot be distinguished, variations of the samples surface (surface variability) can be falsely interpreted as topography changes and undermine the reliability of interferometric measurement. For this reason, knowledge of the sample’s structure\composition is required to eliminate its effect on the interference phase, which is rarely available a priori. Spectroscopic ellipsometry is a well-known metrology technique for the determination of the optical and thus structural properties of multilayered samples with high accuracy through a measurement of some ellipsometric parameters. These parameters are extracted for each pixel in the sample by a combination of sequential measurements taken with a variation in the orientation of a polarizer or a compensator, or most commonly a rotating analyzer\compensator. Thus the acquisition time and throughput are limited in addition to the constraint of stationary sample during data acquisition (rotation) for noise and errors reduction. These techniques are not suitable for high throughput oriented production lines and dynamic samples where the sample is in constant motion. We present a novel fast spectroscopic ellipsometry system enabling the parallel acquisition of all necessary data enabling high speed and accurate sample characterization. This parallel spectroscopic ellipsometer is integrated with our dynamic focusing probe, allowing high-speed and surface variability immune interferometry based axial position tracking.

In recent years we investigated optical inspection methods for quality control of printed matter. Special imaging processes like reflected shadow imaging in the specular reflex, scanning through focal planes using switched delay elements and narrowing the depth of field by using central stops, and also cross polarization photography were used to separate printed layers from semi-macroscopical structures or textures of glossy surfaces and vice versa. These methods are interesting not only for printed matter, but for several kinds of more or less 2-1/2-D surfaces, like textured metal sheets, lacquered surfaces or laminated material. A similar problem arises in the automated inspection of natural roof tiles, especially from clay slate with fine mica like lamella structure, which is usually the preferred material due to cleavage and easy machining. The typical inspection process involves visual and acoustic checks for possible disintegration of the lamella structure throughout the tile, but it does not necessarily quantify the integrity of the lamellae near surface. Further, the orientation and quality of the breaking edges of the lamellae determines the water flow conditions on the roof and the resistance against frost damages, which is to be considered in the finishing process when the tile is cut from the blank and again when installing the tile. While traditionally the slate production involves manual and visual inspection in every step, an automated inspection method for pre-selection and orientation of blanks as well as documented and certified onsite inspection are desirable. The present paper is dedicated to the development of a robust and rugged imaging system, which emphasizes the slate structure in orthogonal view an allows the discrimination of elevated edges from color variations and the extraction of the edge orientation in both longitudinal and transversal directions. In the paper we discuss our current investigations, the system concept and application examples and present some illustrative measurement results.

Optical fiber technology is the driving force behind the ever-increasing data transport and internet usage in today’s connected society. The tight alignment tolerance required when connecting single-mode telecom fibers become even more tight when multiple fiber connectors are being used in the optical link. To alleviate this, we expand the mode field of the fiber and use 3D nanoprinting to print taper structures that can relax alignment tolerances in physical contact expanded beam connectors. We present the design and fabrication of a linear taper which expands the fundamental mode of a single-mode telecom fiber adiabatically with a factor of 3. The taper itself was fabricated on top of a cleaved fiber facet with the two-photon polymerization-based 3D nanoprinting technique, which allows fabrication of high aspect-ratio structures with submicrometer resolution. A proof-of-concept demonstrator was built to measure the obtained misalignment tolerance relaxation. Experimental results for lateral misalignment show excellent agreement with simulated values, but the beam expansion with an air-cladding taper also induces an excess loss of about 0.22 dB compared to a standard physical contact connection without beam expansion. This shows the compromise that has to be made between insertion loss and misalignment tolerance relaxation. The use of additive manufacturing techniques in fiber beam expansion applications makes it possible to fabricate taper structures with full 3D design freedom.

Color uniformity is an important performance metric for many solid-state lighting systems, particularly those systems that use multiple light-emitting diodes (LEDs) to produce the desired illumination distribution. Once the optical design is done, however, it is important to understand how the color uniformity changes when LEDs from within a single color-bin are mixed. Can the design tolerate any LED within the color-bin? Are the inter-bin color variations noticeable in the beam distribution? Are they noticeable when looking back at the luminaire? This paper looks at this question using an exterior automotive stop lamp. The statistical variation of color uniformity is analyzed using assumed interbin statistical variation for the color of the LEDs.

With the emerging availability of commercial LED based illumination systems, new families of standard specifications evolved. The special properties of LED compared to conventional thermal light sources lead to several new aspects in various fields of standardization and metrology, such as colour fidelity, luminance, problems of coherence and temporal power modulation, connected partially with problems found in laser technology. On one hand, fidelity standards had to be redefined, on the other hand, standards connected with occupational safety and health had to be adapted. Compliance with these standards is ensured by metrology methods and devices, which are subject to standard specifications, too. In the paper, we discuss the conformity of the metrology methods and devices proposed with the standard specification itself; flexibilities in the standard specifications leading to obvious gaps between the metrology and the technical definitions are addressed. Further on, technical simplifications made in the standard specifications are discussed under biological aspects. Finally, in continuation of our investigations on special temporal perception effects, as published in recent years, we discuss some results from spectral analysis in low frequency spectral domain.

We present an optical system and method to measure the photo-response non-uniformity (PRNU) of CMOS image sensors at different illumination conditions. By using a tunable monochromatic light source with the collimated beam output, the wavelength and incident angle of the light input can be arbitrarily selected. We demonstrate that such a spectrally and angularly resolved measurement provides valuable information on the correlation between the image noise, the crosstalk, and the layer structure. We discuss the measurement results of the PRNU for a CMOS RGB image sensor at wavelengths of 550 nm and 650 nm at incidence angles of 0 and 30 degrees. The PRNU of each color channel shows a different dependence on the incidence angle, which can be explained based on the layer structure and the crosstalk behavior. We conclude that the investigation on the correlation between the PRNU and the crosstalk can be very useful to evaluate and improve the design and construction of the image sensors for better image quality.

Commercial ray-tracing programs can optimize system parameters for a given optical architecture (e.g., radii, thickness, and spacing of lenses); however, design of the underlying system architecture (e.g., number of lenses, their type, and their order in the optical train) remains an expensive trial-and-error approach driven by prior experience and human intuition. Work on automating the architecture design process has had some success but the problem remains open. We compare the efficacy of novel methods for encoding the design of optical systems on a simple imaging objective.

The results of optical design of non-standard objectives for biological light microscopes are presented. Considered objectives, which use water immersion, including. Also, quartz fluorite plan monochromate objectives for the fluorescence use.

Sensor surface or division plate of optoelectronic imaging system can retroreflect incident beams energy strongly. This so-called cat eye effect is useful for engineering application, such as range finding. However, it is hazardous for the hidden photoelectric equipment be detected by a laser active device based on cat eye effect. In this paper, we propose a new scheme of geometrical optics imaging system to change the beam incident angle on the detector surface. Thus, the reflected beam energy could pass through a completely different route and be blocked by the lens aperture, so it cannot be reflected back to the active detection device. The aim of anti-detection for the lens design is achieved by usage of prism and phase corrector. A prism plays a role of bending beam direction of propagation to deviate from the optic axis and maintaining the direction of image surface simultaneously. The cemented achromatic prism used herein is to correct the chromatic aberration induced by the prism. And we also adopt a fixed phase corrector to compensate the large amount of oblique astigmatism following a prism in nonparallel beams. A final anti-detection optical imaging lens is shown as example. We offer the detailed design and simulation results, which shows that this kind of optics system can reduce the cat eye reflected signal substantially and maintain acceptable imaging performance.

Effects of aperture size on the performance of CMOS image sensor with pixel aperture for depth extraction are investigated. In general, the aperture size is related to the depth resolution and the sensitivity of the CMOS image sensor. As the aperture size decreases, the depth resolution is improved and the sensitivity decreases. To optimize the aperture size, optical simulation using the finite-difference time-domain method was implemented. The optical simulation was performed with various aperture sizes from 0.3 μm to 1.1 μm and the optical power with the incidence angle as a function of the aperture size was evaluated. Based on the optical simulation results, the CMOS image sensor was designed and fabricated using 0.11 μm CMOS image sensor process. The effects of aperture size are investigated by comparison of the simulation and the measurement results.