最新刊期
期 6 ， 2021
- 摘要：This paper proposed a single-exposure photoalignment method based on a spatial light modulator, which could realize arbitrary pattern design. The polarization direction of the output light can be controlled on the pixel level, and then different local liquid crystal (LC) orientations are generated. Hence, Pancharatnam-Berry (PB) phase LC devices with arbitrary LC distribution patterns, can be fabricated using our method. Such a non-interference single-exposure method is simple and efficient, and is less sensitive to the influence of environmental interference. Based on this approach, we fabricated a variety of PB phase LC devices: gratings, lenses, holograms and q-plates using two photoalignment materials. Our PB phase LC devices can achieve high diffraction efficiency with continuous phase distribution. Based on the PB devices we also designed a head-up display and a head-mounted display system for augmented reality applications.关键词：liquid crystal devices;photoalignment;spatial light modulator;geometric phase;Pancharatnam-Berry phase
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发布时间：2021-05-28 - 摘要：Modern telecommunication networks use wavelength division multiplexing (WDM) technology to increase the transmission capacity of the fibres. Wavelength selective switches (WSSs) based on the liquid crystal on silicon (LCOS) technology enable network operators to route the signals on the wavelength basis, which significantly reduce the operational expenses (OpEx). This paper reviews the development of LCOS-based WSSs and its role in reconfigurable all-optical telecommunication networks. The key performance parameters for the WSSs and LCOS devices are explained in great details, with an aim to promote the research and development of this field.关键词：liquid crystal on silicon;wavelength selective switch;all-optical networks;ROADM
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发布时间：2021-05-28 - 摘要：Holographic display technology can record and reconstruct the wavefront information of the original objects completely, which is considered as the ultimate goal of 3D display. Holographic reconstruction with large viewing angle is one of the key technologies in holographic display. In this paper, several technologies of holographic display with wide viewing angle have been introduced and the technical routes have been discussed by analyzing the principle of the holographic display based on the liquid crystal spatial light modulator. The realization principles, merits and demerits of these existing methods have been analyzed. With the reduction of size of the pixel pitch of liquid crystal spatial light modulators, the improvement of the refresh rate, and the combination of new devices and materials, the wide-viewing-angle holographic display will have new development.关键词：holographic display;3D display;spatial light modulator
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发布时间：2021-05-28 - 摘要：Computer-generated holography has shown the ability of diffractive calculation and digital encoding for optical wavefronts. The optical wavefronts can be reconstructed through the coherent illuminating onto computer-generated holograms. But the spatial bandwidth product of computer-generated holography is still limited by existing digital modulating elements, resulting in a degraded optical reconstruction with excessive noises introduced by amplitude encoding or phase encoding. Complex-modulated holography encodes the complex-amplitude wavefronts with existing optical elements and avoids the discarding of amplitude or phase. It possesses the advantages of high calculating efficiency, high spatial bandwidth product and high reconstructing accuracy. The double-phase decomposition is a promising complex-modulating method with high theoretical maturity and optical reliability, making it highly desired and of great value in the future three-dimensional holographic display. This paper reviews the principle and recent progress of complex-modulated holographic display, especially the recent researches based on the double-phase complex modulation using liquid crystal spatial light modulators.关键词：complex modulation;computer-generated holography;Liquid crystal spatial light modulator
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发布时间：2021-05-28 - 摘要：Taking advantages of both the progress in optics, electronics and computer science and the innovation of new algorithms, computer-generated holography has had a rapid development in recent decades. Because of the fact that current available liquid-crystal spatial light modulators have a superior capability and a higher diffraction efficiency in modulating the phase component of wavefront, the optimization of phase-only hologram is a hot topic in this field. This article reviews the development of computing holography and the algorithms of computer-generated-phase-only hologram categorized by the iterative method, the non-iterative method and other method. The traditional methods can meet the different requirements of computation loads and reconstruction quality, while the advanced methods like deep learning and Wirtinger flow bring new ideas into the optimization problem of phase-only hologram. All this progress contributes to the realization of real-time holographic display with high quality and large field of view. In the future, more focus will be placed on the optimization algorithm for curved phase-only hologram generated by three-dimensional object.关键词：computer-generated hologram;phase-only hologram;iterative algorithm;non-iterative algorithm
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发布时间：2021-05-28 - 摘要：As a basic micro-optics element, microlens has widespread applications in many fields, whereas the common fabrication methods for microlens compounded from transparent and brittle materials always have a low efficiency and high requirement for environment. Liquid crystal spatial light modulation (SLM) as a light modulation instrument, can realize multi-focus or structured light fields easily, and has important potential application values in optical communication or microfabrication based on ultrafast laser. Herein, a fabrication method is introduced for microlens, which combines the advantages of femtosecond (Fs) laser microfabrication and wetting etch. The key factors influencing the morphology of microlens are analyzed systematically. By introduction of the spatial light field modulation in the femtosecond laser micro/nano fabrication, the number as well as the position of focused spots can be finely controlled, which not only greatly enhances the fabrication efficiency of microlens arrays out of transparent and brittle materials, but also makes it possible to adjust the morphology of femtosecond laser ablation modification dynamically during processing. The application of spatial light field modulation in micro-photonic integrated chip fabrication is well demonstrated.关键词：femtosecond laser;wet etching;spatial light modulation;microlens
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发布时间：2021-05-28 - 摘要：The dynamic optical tweezers based on asymmetric vortex beam is proposed. The separation and polymerization of yeast cells are realized by dynamic regulation of vortex beam based on computational holography, the manipulation characteristics of asymmetric dynamic vortex beam on yeast cells is investigated. Finally, the optical trap stiffness of this optical tweezers system to manipulate yeast cells is calculated. The statistical average value of the optical trap stiffness is 0.098 5 pN/μm when the laser output energy is 230 mW.关键词：optical tweezers;asymmetric vortex beam;computational holography;spatial light modulation;optical trap stiffness
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发布时间：2021-05-28 - 摘要：Airy beam has the characteristics of non-diffraction, self-healing and self-acceleration, which has attracted much attention in the fields of optical manipulation, nonlinear optics and optical imaging. This paper introduces the method of generating and controlling Airy beam by using 4f system constructed by a spatial light modulator. By adjusting the self-bending propagation point spread function of the Airy beam, the Airy beam three-dimensional reconstruction microscope is cesigned and realized, and the imaging performance of the microscope is stuilied. Using a 40×/0.75 NA objective lens, the lateral resolution is about 0.5 μm, and the axial resolution is about 1.5 μm, and 3D non-scanning two-color imaging of kidney tubules is realized in mouse kidney cells with 10 μm depth.关键词：Airy beam;3D imaging;optical microscopy technology
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发布时间：2021-05-28 - 摘要：Phase-only spatial light modulator (SLM) modulates the phase of the light quantitatively. Due to the limited manufacture process, the SLM need to be calibrated. The LUT describes the input grayscale and output phase, which represents the modulation. This article introduces the self-referenced calibration method for the SLM. The reference beam is generated from the grating zone. The measured beam carries the modulated phase on the measured zone. The interferograms are made by the self-reference beam. Using the fringes analysis method and digital holography technique, the global and spatial phase modulation of the SLM are measured for calibration. The self-referenced calibration method is compact and easy to align. On-site phase calibration can be carried out with a beam splitter and imaging sensor.关键词：spatial light modulator;phase modulation;phase calibration;self-referenced method;interference method
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发布时间：2021-05-28
Liquid Crystal Spatial Light Modulator and Its Applications
- 摘要：A dynamic bistable stochastic resonance algorithm is proposed to solve the problem of non-uniform low illumination image enhancement. Based on the bistable stochastic resonance model, the noise energy in the image is transferred to the low illumination area, which can effectively enhance the brightness of the low illumination image. In the research process, the iterative threshold of low-illumination pixel is set to avoid the excessive enhancement in high-luminance areas, which can ensure the image has better visual perception. Perceived Quality Assessment (PQA) and Luminance Order Error(LOE) are used as the evaluation index of image quality. Through comparative experiments, it is found that the PQA value of the designed algorithm is closest to 10, which enhances the image quality best, while the LOE value is between 67 and 204, and the image nature is the best.关键词：stochastic resonance;image enhancement;low illuminance images
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发布时间：2021-05-28 - 摘要：In order to improve the user experience, near-eye display devices should be lightweight and have high resolution and high refresh rate, which is difficult for traditional video compression solutions. To solve this problem, this paper applies the motion estimation to bit-plane compression, and maps just noticeable difference to the bit-plane to guide the matching criterion of motion estimation. At the same time, starting from the application scenarios of digitally driven microdisplays in the field of virtual reality, the search range of motion estimation is adapted according to the refresh rate. Finally, combining the relationship between the critical frequency of the human eye and the bit plane, a matching threshold is set to further eliminate redundancy. This paper presents a video compression scheme based on bit-plane motion estimation, designs a digitally driven microdisplay controller and builds a system verification design. Experimental results show that the average compression ratio of this scheme is 9.328 8, the compression efficiency is high. The average peak signal-to-noise ratio of the decoded picture is 22.810 3 dB, and the structural similarity is 0.946 6. It can be seen that the mapping of the distortion to the bit plane is effective, and the picture quality and rendering effect are good, in line with the intuitive experience of the human eye.关键词：near-eye display;microdisplay;motion estimation;just noticeable difference
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发布时间：2021-05-28 - 摘要：A smart home system is designed which can realize the functions of face recognition, automatic door opening, indoor CO concentration detection, indoor illumination detection, automatic control lighting, indoor temperature detection, indoor security detection and other functions. The purpose is to let people get safe and practical living environment at home. Through the establishment of WiFi communication, the mobile phone control door opening is realized. This design adopts the OpenMV camera based on STM32F765 chip as the main identification instrument. The linear back projection algorithm is used to calculate the collected face data and the calculation results are compared with the face database to realize the automatic door opening function. When the system is running continuously, the data collected by the external equipment such as CO gas sensor, temperature sensor, optical sensor, infrared sensor and photoelectric sensor are processed to complete the corresponding detection and processing functions. Finally, the whole system is checked by the hardware model. The experimental results show that the system runs smoothly and all the function indexes have been achieved. A more reliable smart home system is obtained.关键词：internet of things;home automation;face recognition;sensor
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发布时间：2021-05-28 - 摘要：In order to satisfy the demand for the domestic high-resolution infrared imaging technology in the field of border and coastal defence monitoring, a technical solution about infrared imaging and enhanced display based on GST817VM1E is proposed in this paper.Hardware platform is designed based on SOPC. Nios is used as the system controller working with the programmable unit to achieve the non-uniformity correction of uncooled infrared detector and infrared image such as two-point correction, blind element compensation, image subtraction background, autofocus and adaptive image enhancement, etc. The system supports the output of different formats and resolutions infrared video images such as PAL, Cameralink, DVI, etc. Experiments show that this solution can generate 14-bit gray level of 800×600 resolution infrared image, and the image frame rate can reach 60 frame/s, which satisfies the requirements of the border and coastal defence monitoring.关键词：infrared thermal imaging;border and coastal defence;SOPC;cameralink
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发布时间：2021-05-28 - 摘要：Simultaneous location and mapping (SLAM) is a key technology for autonomous driving vehicles and robots to realize autonomous movement. The lidar currently used in SLAM technology presents a series of issues, including high cost, low spatial resolution of laser point clouds, and difficulty in obtaining accurate semantic information. In contrast, cameras can effectively avoid the above problems, but more complex algorithms are required in depth prediction and mapping. In recent years, with the progress in computing hardware, the continuous expansion of data sets, as well as the introduction of new computer vision algorithms, the accuracy and efficiency of visual depth prediction and mapping algorithms have been significantly improved. This article summarizes the existing methods of visual depth prediction and point cloud mapping and classifies the methodology based on data collection approach and algorithm design, then analyzes the application scenarios and prospect of visual depth estimation and point cloud mapping.关键词：monocular depth detection;binocular depth detection;deep learning;point cloud mapping
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发布时间：2021-05-28
Image Processing
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