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For this research, we have developed key technologies for a 1.5 µm pixel pitch spatial light modulator (SLM) using Ge2Sb2Te5 (GST) phase change material. To uniformly modulate each pixel, we designed a lateral pixel structure in which a heating current flows through a bottom indium tin oxide layer. To check hologram reconstruction both after multilevel fabrication processes and before implementing full source and driver circuits, we fabricated an 8K×2K hologram on the topology by changing the GST film's phase using laser irradiation. To overcome the limitation of SLM size, we tested a physical tiling structure and found that flatness of tiled SLMs was the most important factor in the realization of holographic displays.

A passive range-finding technique utilizing moiré images of Ronchi-like gratings with bilateral asymmetry, specifically fork gratings, is explored. Fork gratings are used as opposed to Ronchi gratings due to their asymmetry in the spatial and frequency domains, which enable the resolution of certain ambiguities in analysis that would otherwise be present. The two patterns which are convolved to produce the moiré image are the fork grating and the nailbed pattern of the pixelated detector. A fork grating of known size and spatial frequency is imaged with a detector of a fixed pixel pitch. Multiple analysis techniques are applied in frequency space, which lead to both relative and absolute measures of distance.

We performed electroholography of real scenes using an RGB-D camera. With the image (RGB) and depth (D) data of 1,920 $\times$× 1,080 pixels and 512 $\times$× 424 pixels, respectively, acquired using an RGB-D camera, we reconstructed a three-dimensional image based on a point-cloud model to generate the hologram. For reconstruction of the hologram, we used a liquid crystal display with a resolution of 1,920 $\times$× 1,080 pixels at a pixel pitch of ${8.0}\,{\mu\textrm{m}}$8.0μm as a spatial light modulator. The amount of information for input data acquired by RGB-D camera becomes large with respect to the spatial light modulator, affecting the image quality of the reconstructed image. In addition, real-time reconstruction becomes difficult. In this study, we reduced the amount of information for input data by downsampling the three-dimensional image data obtained using the RGB-D camera in a lattice pattern and evaluated the reconstructed image from the hologram.

Virtual reality-head mounted displays require a display with high resolution over 2000 ppi, super-fast response time and high contrast ratio for realizing super image quality at near-eyes. Several liquid crystal devices utilizing fringe-field switching (FFS) mode, having response times less than of half of conventional FFS mode, were proposed for this purpose. However, its contrast ratio is still less than 2000:1 because of intrinsic electro-optic characteristics of homogenous alignment mode and also realizing high resolution like 2000 ppi has some difficulty because twist deformation of liquid crystals can easily affect liquid crystal orientation near pixels. In this paper, we propose a vertically aligned liquid crystal device in which bend deformation occurs in a confined area by an oblique electric field, exhibiting 4 times faster decay response time than that of conventional FFS mode, higher contrast ratio over 5000:1, and pixel pitch less than 4 μm. The proposed liquid crystal device has a strong potential to be the main display for high-resolution virtual reality over 2000 ppi.

Highly efficient transmission-type beam deflectors that have high angular resolution have been widely used for various applications. Continuously tunable beam deflectors have also been needed for many purposes. An indium-tin-oxide (ITO), widely used for transparent electrodes, was placed on the upper and lower glass substrate. The ITO layer on the lower substrate was patterned by the contact mask aligner for relatively wide input and output pad compared to main grating ITO patterns in the active area. These input and output pads on the lower substrate are connected to each driving integrated circuit (IC), which has 360 channels for continuous control. A small pixel pitch of grating patterns of 6 μm (the electrode width is 3 μm with a 3 μm spacing) was developed, and the maximum diffraction angle is calculated and measured at 2.541° with a wavelength of 532 nm. A minimal cell gap of 2.5 μm was applied for the full 2π phase modulation by using a high-birefringence liquid crystal. A driving module for continuous beam steering is also developed and applied to the beam deflector system. A diffraction efficiency of about 50.9% is observed at an angle of diffraction about 2.541°.

We present an ultracompact infrared cryogenic camera integrated inside a standard Sofradir's detector dewar cooler assembly (DDCA) whose field of view is equal to 120°. The multichannel optical architecture produces four nonredundant images on a single SCORPIO detector with a pixel pitch of 15 μm. This ultraminiaturized optical system brings a very low additional optical and mechanical mass to be cooled in the DDCA: the cool-down time is comparable to an equivalent DDCA without an imagery function. Limiting the number of channels is necessary to keep the highest number of resolved points in the final image. However, optical tolerances lead to irregular shifts between the channels. This paper discusses the limits of multichannel architectures. With an image-processing algorithm, the four images produced by the camera are combined to process a single full-resolution image with an equivalent sampling pitch equal to 7.5 μm. Experimental measurements on the modulation transfer function and noise equivalent temperature difference show that this camera achieves good optical performance.

Single-photon avalanche photodiode (SPAD) image sensors offer time-gated photon counting, at high binary frame rates of >100 kFPS and with no readout noise. This makes them well-suited to a range of scientific applications, including microscopy, sensing and quantum optics. However, due to the complex electronics required, the fill factor tends to be significantly lower (< 10%) than that of EMCCD and sCMOS cameras (>90%), whilst the pixel size is typically larger, impacting the sensitivity and practicalities of the SPAD devices. This paper presents the first characterisation of a cylindrical-shaped microlens array applied to a small, 8 micron, pixel SPAD imager. The enhanced fill factor, ≈50% for collimated light, is the highest reported value amongst SPAD sensors with comparable resolution and pixel pitch. We demonstrate the impact of the increased sensitivity in single-molecule localisation microscopy, obtaining a resolution of below 40nm, the best reported figure for a SPAD sensor.

We report a new technique for building a wide-angle, lightweight, thin-form-factor, cost-effective, easy-to-manufacture near-eye head-mounted display (HMD) for virtual reality applications. Our approach adopts an aperture mask containing an array of pinholes and a screen as a source of imagery. We demonstrate proof-of-concept HMD prototypes with a binocular field of view (FOV) of 70°×45°, or total diagonal FOV of 83°. This FOV should increase with increasing display panel size. The optical angular resolution supported in our prototype can go down to 1.4-2.1 arcmin by adopting a display with 20-30 μm pixel pitch.

This paper proposes two moiré reduction methods for coarse integral volumetric displays composed of multilayer display panels. The quality of the image presented by the conventional multilayer integral imaging stays relatively low because of the moiré pattern, which appears due to the layering structure of display panels with limited pixel aperture. The authors propose two methods to solve this problem. The first method is to add another layer of convex lens array with short focal length on the front side of the layered display panels. The second method is to enlarge the pixel pitch of the back-layer panel while fixing that of the front-layer panel.

We present Terahertz (THz) imaging with a 1D multichannel time-domain spectroscopy (TDS) system which operates with a photoconductive array of 15 detection channels excited by a 1030 nm femtosecond fiber laser. The emitter and detector are photoconductive antennas based on InGaAs/InAlAs multi-layer heterostructures (MLHS). We characterized the THz optics and the resolution of the system. The performance is demonstrated by the multichannel imaging of two samples. A simultaneous measurement of 15 THz pulses with a pixel pitch of 1 mm increases the measurement speed of the TDS system by factor 15.

This paper explores practical design considerations for selecting Q for an electro-optical earth imaging system, where Q is defined as (λ FN) / pixel pitch. Analytical methods are used to show that, under imaging conditions with high SNR, increasing Q with fixed aperture cannot lead to degradation of image quality regardless of the angular smear rate of the system. The potential for degradation of image quality under low SNR is bounded by an increase of the detector noise scaling as Q. An imaging test bed is used to collect representative imagery for various Q configurations. The test bed includes real world errors such as image smear and haze. The value of Q is varied by changing the focal length of the imaging system. Imagery is presented over a broad range of parameters.

Current division-of-focal-plane polarization imaging sensors can perceive intensity and polarization in real time with high spatial resolution, but are oblivious to spectral information. We present the design of such a sensor, which is also spectrally selective in the visible regime. We describe its extensive spectral and polarimetric characterization. The sensor has a pixel pitch of 5 µm and an imaging array of 168 by 256 elements. Each element comprises spectrally sensitive vertically stacked photodetectors integrated with a 140 nm pitch nanowire linear polarizer. The sensor has a maximum measured SNR of 45 dB, extinction ratio of ~3.5, QE of 12%, and linearity error of 1% in the green channel. We present sample spectral-polarization images.

Novel integral floating three-dimensional (3D) display methods are proposed for implementing an augmented reality (AR) system. The 3D display for AR requires a long-range focus depth and a see-though property. A system that adopts a concave lens instead of a convex lens is proposed for realizing the integral floating system with a long working distance using a reduced pixel pitch of the elemental image. An investigation that reveals that the location of the central depth plane is restricted by the pixel pitch of the display device is presented. An optical see-through system using a convex half mirror is also proposed for providing 3D images with a proper accommodation response. The concepts of the proposed methods are explained and the validity of system is proved by the experimental results.

In this paper, we propose an approach, new to our knowledge, to effectively generate and reconstruct the resolution-enhanced computer-generated hologram (CGH) of three-dimensional (3-D) objects with a significantly reduced in memory size novel look-up table (N-LUT) by taking into account a relationship between the pixel pitch and reconstruction distance of the hologram pattern. In the proposed method, a CGH pattern composed of shifted versions of the principal fringe patterns (PFPs) with a short pixel pitch can be reconstructed just by using the CGH generated with a much longer pixel pitch by controlling the hologram reconstruction distance. Accordingly, the corresponding N-LUT memory size required for resolution-enhanced hologram patterns can be significantly reduced in the proposed method. To confirm the feasibility of the proposed method, experiments are carried out and the results are discussed.

A color image was taken with a CMOS image sensor without any infrared cut-off filter, using red, green and blue metal/dielectric filters arranged in Bayer pattern with 1.75 µm pixel pitch. The three colors were obtained by a thickness variation of only two layers in the 7-layer stack, with a technological process including four photolithography levels. The thickness of the filter stack was only half of the traditional color resists, potentially enabling a reduction of optical crosstalk for smaller pixels. Both color errors and signal to noise ratio derived from optimized spectral responses are expected to be similar to color resists associated with infrared filter.

Imagery from microgrid polarimeters is obtained by using a mosaic of pixel-wise micropolarizers on a focal plane array (FPA). Each distinct polarization image is obtained by subsampling the full FPA image. Thus, the effective pixel pitch for each polarization channel is increased and the sampling frequency is decreased. As a result, aliasing artifacts from such undersampling can corrupt the true polarization content of the scene. Here we present the first multi-channel multi-frame super-resolution (SR) algorithms designed specifically for the problem of image restoration in microgrid polarization imagers. These SR algorithms can be used to address aliasing and other degradations, without sacrificing field of view or compromising optical resolution with an anti-aliasing filter. The new SR methods are designed to exploit correlation between the polarimetric channels. One of the new SR algorithms uses a form of regularized least squares and has an iterative solution. The other is based on the faster adaptive Wiener filter SR method. We demonstrate that the new multi-channel SR algorithms are capable of providing significant enhancement of polarimetric imagery and that they outperform their independent channel counterparts.

We propose a microoptical approach to ultra-compact optics for real-time vision systems that are inspired by the compound eyes of insects. The demonstrated module achieves approx. VGA resolution with a total track length of 1.4 mm which is about two times shorter than comparable single-aperture optics on images sensors of the same pixel pitch. The partial images that are separately recorded in different optical channels are stitched together to form a final image of the whole field of view by means of image processing. A software correction is applied to each partial image so that the final image is made free of distortion. The microlens arrays are realized by state of the art microoptical fabrication techniques on wafer-level which are suitable for a potential application in high volume e.g. for consumer electronic products.

A bench-top physical model eye that closely replicates both anatomical and optical properties of an average human eye was designed and constructed. The cornea was sourced from a flouro-polymer with refractive index (RI) of 1.376 and crystalline lenses were made of Boston RGP polymers, EO and Equalens II, with an equivalent RI of 1.429 and 1.423 respectively. These materials served to make crystalline lens components of different age groups and accommodative states. De-Ionized water, with RI of 1.334 represented both aqueous and vitreous humor. The complementary metal-oxide sensor of a PixelLink digital camera with a resolution of 5MP and a 2.2 microm pixel pitch, hosted on a motor-base, served as the 'acting' retina. The translation and rotary functions of the motor-base facilitated the simulation of different states of ametropia and assessment of peripheral visual function, respectively. We validated one of its configurations to suit normal viewing conditions and results from the on and off-axis optical quality measurements are presented. As a demonstration of potential practical uses, several corrective soft contact lenses were placed on the model eye and their optical performance evaluated.

A frameless hologram display module employing a modified resolution redistribution system is proposed in this paper. The frameless display modules can be aligned two-dimensionally to realize a large display screen. The modified resolution redistribution system consists of a one-lens imaging system, a screen lens, and a multiple illumination system. The prototype module was constructed using a spatial light modulator with a resolution of 1,980 x 1,080, and a pixel pitch of 8.0 microm. The horizontal resolution was increased four times and the magnification of the imaging system was 2.88. The horizontal resolution was increased to 7,920 and the horizontal pixel pitch was reduced to 5.8 microm. The screen size of the module was 2.0 inches and the horizontal viewing angle was 6.3 degrees.

The ability to retrieve the complex-valued, generalized pupil function of an imaging system from undersampled measurements of the defocused system point spread function (PSF) is examined through numerical simulations. The ability to do so degrades as the detector pixel pitch increases when using a fixed number of PSF measurements. Two strategies for obtaining better results with undersampled data are demonstrated using additional PSF measurements with (i) random shifts due to system pointing fluctuations and (ii) intermediate amounts of defocus.

In order to increase the image size and the viewing zone angle of a hologram, a high-speed spatial light modulator (SLM) is imaged as a vertically long image by an anamorphic imaging system, and this image is scanned horizontally by a galvano scanner. The reduction in horizontal pixel pitch of the SLM provides a wide viewing zone angle. The increased image height and horizontal scanning increased the image size. We demonstrated the generation of a hologram having a 15 degrees horizontal viewing zone angle and an image size of 3.4 inches with a frame rate of 60 Hz using a digital micromirror device with a frame rate of 13.333 kHz as a high-speed SLM.

An algorithm designed for digital color holography is presented. It is based on a filter bank allowing full object reconstruction with a pixel pitch being invariant along each wavelength. Its application to high-resolution simultaneous two-wavelength metrology is described.

We demonstrate an integrated evanescent-field multimode Mach-Zehnder interferometric chemical-biological sensor, fabricated on silicon, with sensitivity of parts per 109 achieved by modal pattern tracking and analysis. This sensor is fully compatible with the fabrication constraints of the silicon-complementary-metal-oxide-semiconductor (Si-CMOS) process. Furthermore, using the separately measured ellipsometric response together with the mass uptake of agent by the polymer sensing layer, we validate sensor performance via simulation and measure an absolute index sensitivity of 2.5×10−6. We then extend this to a fully integrated chemical-biological sensor by considering the fundamental noise performance of CMOS detectors. We find that relatively short

We developed an electroholography unit, which consists of a special-purpose computational chip for holography and a reflective liquid-crystal display (LCD) panel, for a three-dimensional (3D) display. The special-purpose chip can compute a computer-generated hologram of 800x600 grids in size from a 3D object consisting of approximately 400 points in approximately 0.15 seconds. The pixel pitch and resolution of the LCD panel are 12 mum and 800x600 grids, respectively. We implemented the special purpose chip and LCD panel on a printed circuit board of approximately 28cmx13cm in size. After the calculation, the computer-generated hologram produced by the special-purpose chip is displayed on the LCD panel. When we illuminate a reference light to the LCD panel, we can observe a 3D animation of approximately 3cmx3cmx3cm in size. In the present paper, we report the electroholographic display unit together with a simple 3D display system.

We propose a scalable high-resolution autostereoscopic display that uses integral videography (IV) and a seamless multiprojection system. IV is an animated extension of integral photography (IP). Although IP and IV are ideal ways to display three-dimensional images, their spatial viewing resolution needs improvement; the pixel pitch of the display and the lens pitch are the main factors affecting IV image quality. We improved the quality by increasing the number and density of the pixels. Using multiple projectors, we create a scalable high-resolution image and project it onto a small screen using long-focal-length projection optics. To generate seamless IV images, we developed an image calibration method for geometric correction and color modulation. We also fabricated a lens array especially for the display device. Experiments were conducted with nine XGA projectors and nine PCs for parallel image rendering and displaying. A total of 2868 x 2150 pixels were displayed on a 241 mm x 181 mm (302.4 dots/in.) rear-projection screen. The lens pitch was 1.016 mm, corresponding to 12 pixels of the projected image. Measurement of the geometric accuracy of the reproduced IV images demonstrated that the spatial resolution of the display system matched that of the theoretical analysis.

A color-reconstruction method for electroholography is proposed in which three colored reference lights, namely, red, green, and blue light-emitting diodes, simultaneously illuminate one hologram plane. Three colored light-emitting diodes are placed at the apexes of a small right-angled triangle. Inasmuch as there is a small gap between consecutive light axes, three colored diffraction lights can be piled up at the place where a three-dimensional image is focused. In our experiment we used a high-resolution liquid-crystal display panel as a spatial light modulator with a pixel pitch of 10 microm and a resolution of 1400 x 1050. The system clearly reconstructed a colored moving image including a mixture of colors, for example, cyan, yellow, magenta, and white.

We present a real-time optical system to enhance defects in periodic patterns by use of nonlinear spatial filtering by real-time holography. A straight and equispaced grating written in a bacteriorhodopsin film is read by the Fourier transform of a periodic pattern to be inspected. Because the diffraction efficiency of the grating depends on the intensity of the reading beam, only the defect component can be selectively diffracted and imaged. This system is applicable even to moving objects. We present experimental results that show enhancement of defects as small as 10 microm in a photomask with a pixel pitch of 150 microm used for a liquid-crystal display.

A coherent processing system for obtaining complex addition of two or more patterns in real time is described. In this system, a sinusoidal diffraction grating is used in the spatial-frequency plane. The input patterns to be added are displayed symmetrically about the optical axis in the object plane. The complex amplitude addition appears in th zero-order location in the output plane. Complex amplitude subtraction may be obtained by adding a 180° phase plate behind one of the input patterns. Displacing the sinusoidal diffraction grating by half a line pitch is also shown to change the performance of the system from addition to subtraction for two input functions, without the need for a phase plate. Experimental verification of the performance is presented. Analysis of the system for two input patterns is first given, then extended to the complex addition of multiple inputs.