Laser displays commonly utilize spatial light modulators (SLM) as imaging devices, but the contrast ratio is limited by uniform illumination and the diffraction properties of SLM, which hinder the realization of high dynamic range (HDR) within a single frame. We investigate the fundamental diffraction properties of a phase light modulator (PLM) using the blazed grating model, explore its capability to steer beams, and evaluate its uniformity as a light field modulator. By employing PLM to modulate various light field distributions and conducting contrast ratio tests in laser display systems, we examine the illumination characteristics of PLM. We specifically select a representative light field distribution to assess the contrast ratio and analyze how altering the light field distribution through PLM affects it. Our findings reveal that reducing the proportion of individual spot size relative to the entire image area enhances the contrast ratio when there is a single spot area present in the modulated light field; conversely, increasing their number decreases the contrast ratio when multiple spots are present in the modulated image. By integrating PLM with a digital micromirror device (DMD), we have validated the feasibility of manipulating light field illumination in display systems, resulting in a remarkable improvement of over 300 times in contrast ratio and achieving HDR of projected images. Through utilization of the central light spot image to confirm its smaller proportion within the entire image, we can enhance the contrast ratio by more than 100 times and peak brightness by over 70 times. These findings demonstrate the viability of employing this approach to achieve HDR in laser displays.
KEYWORDS: Diffraction, High dynamic range imaging, Blazed gratings, Modulation, Digital micromirror devices, Micromirrors, Light sources and illumination
Texas Instruments has developed a Phase Light Modulator (PLM) based on Digital Light Processing (DLP) System, which alters the distribution of the light field. This paper explores the fundamental diffraction properties of PLM using the blazed grating model, investigates its capability to steer beams and tests its uniformity as a light field modulator. We selected a typical light field distribution to test the contrast ratio and examined how changing the light field distribution through PLM affects contrast ratio. When there is a single spot area exists in the modulated light field, decreasing the proportion of the individual spot to the entire image area, increases the contrast ratio; When there are multiple spots in the modulated image, increasing their number, decreases the contrast ratio. The feasibility of arbitrarily manipulating light field illumination for display system applications is verified by combining PLM with Digital Micromirror Device (DMD), leading to improved contrast ratios and better realization of High Dynamic Range (HDR) in projected images.
Texas Instruments has developed a phase light modulator (PLM) based on Micro-Electromechanical System (MEMS). This modulator offers several excellent advantages, including high refresh rate, compact optical path, and high optical efficiency, making it well-suited for applications in laser displays. In this paper, we divide the PLM into three regions and illuminate them with corresponding color laser light. The diffracted image is eventually reproduced and superimposed at the image plane in order to obtain a colorful display. We measured the display indicators such as inherent resolution, coincidence error, contrast ratio, uniformity, optical efficiency and diffraction efficiency of this methodology. The advantages of this methodology lie in its compact optical path and excellent optical efficiency. This work enhances the development of single PLM for color laser display applications in field sequence, including holography and volume display.
Display technology is the main source for humans to obtain information and entertainment. Increased display screen size is a trend, whether on mobile phone or television, and projection display has become increasingly popular in achieving large screen displays. Previous projection display systems have used a traditional light bulb which cannot be modulated, so the power of the display device is constant and the contrast of the display device can only be improved by controlling the size of the aperture in the light path. With the appearance of solid-state light sources, i.e., lasers, the luminance of the light source can be modulated according to the image content so that the power of the light source can be reduced and the dynamic contrast can be improved simultaneously. A method to modulate the power of the laser light source on a frame-to-frame basis in response to the input image data is shown. An ultrahigh contrast is achieved with the laser display. A dynamic contrast of greater than 100,000:1 can be achieved, and the average power consumption of the laser TV can be reduced by about 20% with typical video source material.
Scattering is the fundamental issue in the field of underwater optics, meanwhile polarization state is also a key feature in underwater laser communications, laser imaging, and underwater quantum optical communication. Aiming at this problem, a software package Geant4 is applied in the simulation, furthermore, an algorithm based on the basic Henyey-Greenstein phase functions and typical polarization Monte Carlo model is proposed, the algorithm is used to simulate the polarization state when the laser is propagating underwater at different concentrations of water or transmission length. At the same time, the experiment is tested in a sink whose length is 10m and the polarization state detector is a laser power meter with accuracy up to 10nW. In this paper, the change of polarization state is expressed by the depolarization ratio. The result of numerical simulation and experimental show the variation of polarization state with concentration and distance respectively, the simulation result of Geant4 is more ideal, due to different kinds of external factors the experimental results are roughly, however, the overall change trend of the two is consistent.
Aiming at being carried on various underwater vehicles for the detection of plankton, a miniaturized in-situ digital inline holographic system named OUC-HoloCam200 is designed and developed. Although the structure of OUC-HoloCam200 is simple and compact, the system performance is still excellent. Tests have been carried out and the result shows that the optical resolution of OUC-HoloCam200 is 8.77 μm, the depth of field is up to 30 cm, the field of view is 8.44×6.75 mm2 , which means theoretically with each exposure, about 300 mL of seawater can be investigated. OUC-HoloCam200 have been deployed in the nearshore area of the South China Sea and have worked continuously over 48 hours, after holographic reproduction and image processing the data is able to show the trends of changing in number and species of plankton over time in the same location.
A focused laser light sheet was used to illuminate the capillary tube filled with liquid and fringe patterns can be seen.
The fringe patterns can be formed by rays directly passing through the capillary tube or reflected one time or two times
by the walls of the capillary tube then transmitted again. The fringe patterns formed by transmission light lie before the
capillary tube and can be bell-shaped, steep bell-shaped, or almost parallel, which strongly depend on the position of the
capillary tube. The bell shaped pattern can be qualitatively explained by the addition of diffraction of multi-slits and is
relative to the aberration of the cylindrical lens. This pattern is also relative to the refractive index of liquid containing in
the capillary tube. The fringe patterns caused by reflected light lie before or after the capillary tube, which will influence
the contrast of the bell shaped fringe pattern formed by transmitted light.
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