Based on Landau-de Gennes theory, the stability of split-core configuration confined in nematic liquid crystal droplets with submicron scale under homeotropic anchoring boundary condition is investigated. Results show that there are radial and ring structures under the strong anchoring boundary condition and single constant approximation. According to the difference of the radius, the two structures will become stable respectively, i.e., the ring structure is stable when the radius is larger, and the radial structure is stable when the radius is smaller. Under the condition of elastic anisotropy, a stable ring structure and a metastable split-core structure will appear. Furthermore, the results show that if the effect of k24 on the internal structure of the droplet is considered, when the boundary anchoring condition is changed from strong anchoring to weak anchoring (take anchoring strength w=10-4J/m2 as an example) and under the single constant approximation, it is found that there would be three structures, i.e., radial structure, ring structure and uniform state structure, and the radial structure is stable state, in addition, the stability among structures is not affected by the effect of k24; under the condition of elastic anisotropy, the radial structure is transformed into the split-core structure. And it is still metastable when the effect of k24 is not considered; if the effect of k24 is considered, the split-core structure can be stable when the size and elastic anisotropy are within a certain range. In our simulation, it is found that the effect of k24 can make the split-core structure become stable for the first time.

With the continuous development of liquid crystal display, the demand for high-performance liquid crystal display is more and more urgent. Many researchers had also carried out a series of researches on improving the performance of liquid crystal display. The color performance, which can be indicated by Gamma shift and color shift, is an important aspect of LCD performance. This paper summarizes the color performance of the conventional three LCD modes, and mainly introduces the improved methods of in-plane switching and vertical aligned LCD modes. It has an important significance to the researchers and designer of LCD. For different display modes, there are corresponding methods to improve the color performance, but each method has its own inherent flaws, it requires users to choose.

As an artificial light source, the laser has the advantages of good monochromaticity, strong directivity, strong coherence, high brightness, and high energy density. Therefore, it has been widely used in laser display, laser lighting and other fields. Since the semiconductor laser was invented, it has occupied a large part of the laser market because of its rapid development, multiple results and wide application. It can be used not only as an information carrier but also as an energy carrier. With the in-depth development of semiconductor lasers and changes in market demand, the research on the synthesis of white light sources through semiconductor lasers has become a hot spot. The emergence of semiconductor laser white light source has not only expanded new areas of laser applications but also laid the foundation for the birth of many new technologies. This article mainly introduces how the semiconductor laser white light source is produced and the difficulties in the production process. Then, it summarizes the research progress of synthetic semiconductor laser white light source at home and abroad in recent years, and analyzes its application limitations and development shortcomings. Finally, we look forward to whether the semiconductor white laser light source can be stably output in the complex underwater environment.

A terahertz phase modulator based on twisted nematic liquid crystal is designed, and the influences of twist angles of 30°, 45°, and 90° on the phase modulation characteristics are analyzed using Jones matrix simulation. The results show that a smaller twist angle leads to the higher phase retardation and larger light utilization efficiency. In addition, with the increase of the voltage at the same frequency, the transmittance increases and the phase retardation decreases. When LC1825 liquid crystal with a twist angle of 30° is injected into a liquid crystal cell with a thickness of 250 μm, the transmission-based terahertz phase modulator is built. The phase retardation of 126° is obtained at a frequency of 1.2 THz. In order to maximize the phase modulation, a reflection-based terahertz phase modulator is also structured, which has similar structural parameters as the transmission-based terahertz phase modulator. As a result, the phase retardation reaches 270° at 1.2 THz, which is much larger than the transmission-based one due to the double effective optical length.

A design theory was demonstrated to design diffraction optical waveguides in wave-vector space. Systematic simulations were performed to investigate relationships among wavelength, grating period, clocking angle, waveguide substrate refractive index, dispersion to field of view and related parameters. Simulation results showed that light sources with broad bandwidth showed little effect on the design results because of the acceptable result of the edge wavelength FOV cutting. The dispersion of waveguide substrate showed negligible effect on diffraction optical waveguides. It is easy to manufacture to choose 40-270-140 clock-angle in design because of the suitable dimensions and positions of grating areas. The results in this work provide positive guides to design diffraction optical waveguides.

A kind of exposure method of dislocation and superposition was studied, which was based on a type of positive photoresist produced by T company. It can realize the effect of gray scale exposure by the method and finally a wedge-shaped bevel microstructure with specific angle was obtained. The absorption coefficient of a photoresist can be changed after irradiated by ultraviolet light. According to the Lambert-Beer law, the bevel structure can be equivalent into step structure, and then the critical exposure energy for the photoresist to react and the absorption coefficients of the photoresist can be calculated, which was irradiated by UV before and after, as well as the exposure energy for the dislocation and superposition method. Experimental results show that the critical exposure energy for the photoresist to react is 8 mJ, and the absorption coefficient α of the photoresist for ultraviolet light is 1.14, which will reduce for 20% after irradiated by ultraviolet light. With irradiating by the energy calculated, the photoresist can form the wedge bevel structure with taper angle of 32°. A specific wedge bevel structure by the dislocation and superposition exposure method can be prepared and the energy can be calculated according to the taper angle of bevel structure.

The 4 mask process of TFT substrate can improve production capacity, but it also brings the problemsin product quality. For example, the 4 mask process can generate white dot defects. The causes of white dots is explored through DC experiment. The mechanism of white dots is studied by illumination experiment and high temperature experiment, and the white dots defects are improved by process adjustment. The mechanism of white dots defects is that the conductivity of active layer is different due to SW effect, resulting in different feedthrough voltage (ΔVp), and the difference of optimal Vcom leads to white dots defects. With the gate and drain electrode signal coupling capacitance Cgs becaming smaller (i.e. the smaller active tail width), the white dots gradually decrease until they disappear. With the pixel storage capacitor Cst becoming larger, the insulation layer thickness (PVX) is reduced from 600 nm to 400 nm, and the degree of white dots defects can be reduced by 1 level. After the process adjustment, the width of active tail is reduced to 1.2 μm, which can solve the white dots problem caused by 4 mask process. This work provides effective solutions and references for the improvement of product quality and benefits as well as subsequent product development.

In the TFT manufacturing process, the exposure process directly affects the quality of the final pattern of the film. In order to analyze and solve the exposure Mura problem, it is necessary to investigate and study the lighting phenomenon of the panel and manufacturing process. Firstly, the cause of failure was investigated by scanning electron microscope analysis, shift exposure experiment, and data analysis. At the same time, with the help of the open source software GIMP and Fiji perform image processing to obtain panel gray data, the Mura degree was quantitavely evaluated. Then, the ratio of exposure Mura was decreased from above 10% to below 1% through adjusting the illumination uniformity of exposure equipment and controlling the optimal production path, effectively improving the panel display quality. Finally, the formation mechanism of exposure Mura was further elaborated based on ExpertLCD optical simulation data and capacitive coupling effect analysis. It is found that pixel CD should be controlled within a certain range and good uniformity. If the pixel CD is too small or too large, the exposure Mura will be easier to appear. Meanwhile. The CD of each conductive layer also needs to ensure good uniformity to reduce the effect of coupling capacitance on the display.

Low temperature polycrystalline silicon and oxide (LTPO) thin-film transistor (TFT) backplane technology combines the advantages of both low temperature polycrystalline silicon and oxide semiconductor TFTs. It has received extensive attention from both industry and academia since it is promising for development of advanced displays with low power consumption, high performance and functional integration. This paper systematically summarizes and analyzes the research progress of technologies and applications related to LTPO and highlights the technical challenges. Firstly, the integration methods of LTPO backplanes for liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays are discussed respectively. Then the challenges of device structures and processing methods for LTPO integration are further discussed. Meanwhile, the advantages of LTPO technology for designing pixel circuits to be compatible with both low and high frame rate driving are analyzed, as well as the internal compensation technologies. The impacts of TFT device stability and compensation methods for ultra-low frame rate (i.e. 1 Hz) driving are also included. Finally, the content of this paper is summarized, and the prospective trend of future LTPO technology is outlined.

The wide/narrow viewing angle switchable thin film transistor liquid crystal display has the problem of moire pattern, which is caused by the continuous change of the phase between the pulse width modulation signal of backlight and the driving signal applied to the display panel under the narrow viewing angle mode. This paper presents a feasible solution. Since root cause of the moire pattern is identified as the signal interference, our solution is to synchronize the signals so as to minimize the phase difference. The experimental results show that, by synchronizing the display panel’s start vertically signal and backlight module’ pulse width modulation signal, the moire pattern could be significantly suppressed. Under a pulse width modulation signal with 1 kHz, 49.8% duty cycle, the value of the flicker in the center area of the moire is from 68.5% to 72.3% under 64 gray scale measured by using the display color analyzer CA-310, and then becomes stable at 69.9%. Based on this scheme, the actual observation of moire is not noticeable, thus it can give users good viewing experience under narrow viewing angle mode.

In order to cope with the complexity and change of the airborne environment, airborne display is required to have high performances in weight, luminance, resolution, and heat dissipation. Micro-LED technology has problems such as low internal quantum efficiency of red LED and green LED, low heat transfer efficiency of the device, and difficulty in solving the driving scheme. Therefore, the technological maturity of Micro-LED is not yet able to meet the needs of airborne display for main displays and micro displays. However, Micro-LED has the incomparable advantages over LCD and OLED, such as high luminance, high resolution, and high pixel density, and is expected to be used in application scenarios such as head-up displays and main displays in airborne environments. This article reviews the research progress of Micro-LED, puts forward the technical problems of Micro-LED urgently to be solved, and discusses the possible solutions to related technical problems and the application prospects of Micro-LED on airborne. In short, Micro-LED's light weight, high luminance, high resolution and other characteristics are sufficient to meet the high requirements of airborne displays in terms of weight, luminance, and resolution. Theoretically, due to the excellent display characteristics of Micro-LED, Micro-LED display technology will become a new display technology with great advantages for airborne display.

At the beginning of the 21st century, commercial display has gradually developed into an independent industry. In order to improve the visual effects presented by wide color gamut full-color Mini-LED commercial display, to solve the problems of the poor color reproduction effect, large color difference and high price of the current Mini-LED splicing screen, a color gamut mapping method applied to Mini-LED commercial display is proposed. This method is based on the display characteristic file of Mini-LED, and the color gamut is mapped by the method of look-up table and tetrahedral difference. Then, according to the difference between the reduction effect and expression ability of different color features between Mini-LED splicing screens, the lookup table is optimized, and the balance of the mapping accuracy, mapping time and resource consumption is improved. The experimental results show that the maximum brightness loss of Mini-LED display after color gamut mapping is about 35%, and the uniformity of pixel intensity decreased from 8.2% to 4.9%, the color difference is reduced from 2.2ΔE to 1.3ΔE, which proves that this method has a good correction effect for the full-color Mini-LED commercial display in pixel intensity uniformity, chromatic aberration and other aspects, meanwhile the effect under visual observation is also improved to a certain extent.

Aiming at the problem of a large number of invalid points in the depth image obtained by the time-of-flight camera, a depth image restoration method based on the color image contour is proposed. This method first determines the variance of the neighborhood through the value of the pixel in the neighborhood of the invalid point and the Gaussian function, and calculates the filling order of all invalid points based on the number and variance of the valid point in the neighborhood of the invalid point, and completes the priority evaluation of the filling process. The contour of the target object in the color image is projected into the depth image, combined with the projection contour and the Euclidean distance function to realize the filling of invalid points. The experimental results show that compared with other commonly used denoising algorithms, the algorithm in this paper can effectively fill invalid points on the premise of protecting the edge of the target object. The signal-to-noise ratio index is improved by 2-14 dB for different target objects.

In order to solve the problems of halo phenomenon and image noise enhancement when the traditional multi-scale Retinex algorithm enhances the details of infrared images, an infrared image detail enhancement algorithm based on improved mult-iscale Retinex is proposed. Firstly, an improved guided filter is used instead of the Gaussian filter to accurately estimate the incident component of the infrared image and calculate its reflection component to reduce the noise in the image and improve the halo phenomenon. Secondly, an adaptive grayscale stretching process is performed on the incident component, and a smoother non-linear curve is used to correct the reflected component, so as to achieve the purpose of better enhancing the overall brightness and contrast of the infrared image. The experimental results show that compared with other corresponding algorithms, the information entropy, peak signal-to-noise ratio, average gradient, and standard deviation have been improved. At the same time, the infrared enhanced image obtained by this algorithm has higher contrast and clearer details. The human eyes have better visual effects.

The traditional remote sensing image segmentation method is inefficient and the segmentation fineness is not enough in complex scenes. The UNET model is well-known for its good segmentation effect, but it does not perform well for the smaller objects contained in the image and the edge segmentation of larger objects. In order to solve this problem, a method combining UNET structure with FPN structure is proposed in this paper to improve the ability of UNET model to integrate multi-scale information. At the same time, the BLR loss function which can better capture the edge of the target edge is used to improve the segmentation effect of UNET model on the target boundary. The experimental results show that the method used in this paper effectively improves the accuracy of semantic segmentation and alleviates the problem of poor edge segmentation of small-scale targets and large-scale targets. The target edge segmentation can be more accurate to achieve better segmentation results.

Aiming at the problems of complex background and small traffic sign target in large view traffic scene, an improved Faster R-CNN detection network algorithm is proposed. Firstly, the deep residual network ResNet50 is used as the backbone network to extract the features of traffic signs. Secondly, the strategy of using reasonable scale sliding window on two different level feature maps is designed to generate the target proposal region to enhance the detection ability of multi-scale traffic signs. Finally, the attention mechanism module is introduced into the residual block to strengthen the key information of the image and suppress the image background information. The validity of the algorithm is verified on the Chinese traffic sign dataset, with an average detection accuracy of 98.52% and a detection rate of 0.042 s per image. The detection effect of the improved algorithm is obviously better than the original Faster R-CNN detection method, and is more suitable for traffic sign detection in complex scenes, with strong robustness.