This PDF file contains the front matter associated with SPIE Proceedings Volume 12063, including the Title Page, Copyright information, and Table of Contents

With the development of augmented reality technology, the pilot helmet also employs this technology, i.e. Helmet Mounted Display. According to the augmented reality design requirements of a type of aircraft Helmet Mounted Display, the Helmet Mounted Display optical system is designed. The software correction method for the aberration of the optical system was studied with the help of the optical software CODEV tool, and the circuit was designed to realize the aberration correction of the Helmet Mounted Display optical system. The results meet the design requirements for the aberration of the optical system.

Illumination non-uniformity caused by the multiple total internal reflection has become an important factor restricting the development of grating- based AR devices. Most of the current solutions can effectively modulate the distribution of diffraction efficiency (DE) of different diffraction orders by adjusting the groove parameters of the diffraction grating, so as to optimize the exit pupil uniformity of the diffraction grating waveguide. In this paper, an out-coupling grating with variable duty cycle is fabricated by a new way to improve the performance of diffraction grating waveguides. The ashing process is chosen to modulate the duty cycle, which can chemically react with the photoresist without damaging the grating substrate. Based on the relationship between the ashing time and the shrinking rate of the duty cycle, the grating coupler can be fabricated to meet the optimized results. The diffraction efficiency of the gratings is tested. The results show that the method we proposed is reliable and effective to produce continuously variable duty cycle gratings. The diffraction efficiency of the grating is gradually improved along the direction of exit pupil expansion, which is beneficial to the display device to achieve more uniform output brightness.

Micro mirror array waveguide technology is a kind of transmission display technology based on the principle of reflection of light, which has the ability of color display with large pupil, and has a wide application prospect in the field of AR display. In order to ensure the transmittance of the exterior light, the reflectivity of the micro mirror array cannot be very high, so the micro mirror array waveguide system is a low optical efficiency system. In this case, the stray light is very sensitive to the influence of the system, so the suppression of stray light inside and outside the system is an important part of the design of micro mirror array waveguide system. In this paper, a typical micro mirror array waveguide is taken as the analysis object, and the optical path of internal stray light and external stray light is analyzed respectively, and the simulation is carried out by using TracePro software. According to the simulation results of stray light optical path, the methods to suppress all kinds of stray light are proposed, which can eliminate most of the stray light, and provide a reference for the design optimization of micro mirror array waveguide.

In this paper, a laser-assisted light-emitting diode (LED) car high-beam headlight for modern cars is proposed. The headlight employs the LED light as the main light source of the car high-beam headlights. Under certain circumstances, the auxiliary main light source of the laser light source is added. Laser light sources are widely used in the field of automotive lighting owing to their high energy efficiency, small size, and good directionality. However, in terms of its application in headlights, the laser itself has limitations, such as a narrow line width and instability. In addition, all laser high beams are afflicted by the problems of laser light sources, and their optical design complexity has increased significantly. Therefore, this study used the total internal reflection of the light cone to promote the uniform distribution of the LEDs. Moreover, the collimating lens is used for laser spot convergence, and the laser light source is positioned at the laser spot to coincide with the LED spot center. Finally, the aspheric lens is incorporated into the light distribution design of the headlight. This optical design ensures driving safety and leverages the advantages of a laser light source to enhance the vehicle high-beam lighting effect, while improving the optical system design and reducing its complexity.

A novel gas pressure sensor based on Fabry-Perot interferometer is proposed and experimentally demonstrated. The sensor is fabricated by splicing the single-mode fiber onto a short length quartz capillary and coating a Polyimide film on the end-face of the quartz capillary. The total length of the sensor head is less than 60μm, compact structure which can be used flexibly in limited space and harsh environment. The experimental results show that the proposed sensor can detect the environment gas pressure by demodulating the wavelength drift of the reflection spectrum of the sensor. The maximum gas pressure sensitivity is 5.357nm/MPa, the linearity is 98.48% and the gas pressure measurement range is 0~0.3MPa. The sensor has the temperature sensitivity at low temperature, and it is insensitive to high temperature. Thus, the temperature cross-sensitivity can be ignored under the high-temperature conditions. The proposed sensor shows some advantages of compact size, high sensitivity, fast response time and low temperature cross-sensitivity, and it has a certain practical application value in industrial production and daily life.

With the development of holography and nanomanufacturing technology, metasurfaces are playing an increasingly important role in the field of holography. We designed a silicon cylindrical structure based on the Huygens metasurface. By exciting the Mie electric dipole and magnetic dipole resonance of the silicon cylindrical structure, a high transmission efficiency of 84% can be achieved at a wavelength of 633 nm, and a full phase coverage of 0-2π can be obtained by adjusting the radius of the silicon cylindrical. We used the angular spectrum algorithm to obtain the phase distribution relationship between the object image and the metasurface, and designed the arrangement of the silicon cylinder metasurface. The simulation obtained a high-fidelity hologram, and the structure has a high transmission efficiency around the 633 nm spectrum. This method can realize metasurface holography with high transmission efficiency, and it can be applied in holographic imaging.

Stitched surfaces have the advantages of high degrees of freedom and flexibility, which can improve the performance of imaging optical system while reducing volume and weight. In this paper, a new type of surface, called annularly stitched aspheric surface (ASAS), is demonstrated. Firstly, the definition of ASAS is given, and it meets the C1 continuity condition. Then, a high-precision conversion method from traditional aspherical surface to ASAS is proposed to establish the initial system with this novel surface. The optimization strategy and implementation method are explained. Special constraints that are needed when optimize the system with ASAS is also mentioned. Finally, the ASAS is applied to the design and an ultra-short throw (UST) ratio projector objective lens is optimized. The total length of the optimized system is only 155mm, the maximum distortion value is only 1.36%, and MTF value of full field of view at 66lp/mm is higher than 0.3. The result shows that this new surface type can increase the degrees of freedom and flexibility to optical system, verifying the feasibility of ASAS.

With the development of augmented reality technology in the future, its application environment is bound to be complex and diverse, and for some extreme weather scenarios, it is very important to solve the existing problems of optical transmission display system.In addition, solving the above problems is more conducive to improving the user's perception ability of scene information in the environment with low visibility. Therefore, by analyzing the problems existing in the augmented reality display system in extreme weather, this paper proposes a set of augmented reality display system for electric navigation. First, calibrate human eyes, tracking cameras and augmented reality display devices. Aiming at the distortion problem in the display process, a four-dimensional light field calibration theory was established to reduce the display error. The camera is used to obtain the scene information, and the 3D point cloud is obtained. By denoising the 3D point cloud, the instance segmentation algorithm is used to obtain the segmentation result of the scene target. Finally, the virtual image is displayed in the scene to display the navigation information in the power operation. The system can provide clear scene information for power operators in extreme weather conditions, effectively improving work efficiency and safety.

In this paper, a two-dimensional diffractive optical waveguide with exit pupil expansion (EPE) is designed. By adding an extended grating between the in-coupling grating and the out-coupling grating, the optical path is redirected so that the exit pupil expansion can be realized in both horizontal and vertical directions, and then the pupil box can be enlarged. The projection collimation optical system is designed, which has the characteristics of small volume and compact structure. Combined with rigorous coupled wave analysis (RCWA), non-sequential ray tracing is used to optimize the grating region to achieve high image brightness uniformity. The results show that the designed EPE diffractive waveguide can achieve a large exit pupil range of 14mm×12mm, the diagonal field of view of the waveguide is 30°, the exit pupil distance is 20mm, and the image brightness in the exit pupil area is uniform.

PIV (Particle Image Velocimetry) plays an important role in the technology of flow field display and measurement. The traditional 2D PIV technique is well-developed, though limited by the performance of the system hardware, like lasers and cameras, its sampling rate is quite low. The time-resolved PIV works at KHz, which however is not quite fit for large test area or high spatial resolution due to the low laser energy per pulse and the low pixel resolution of cameras. In fact, it is not easy to make out a PIV system with high pixel resolution and high sampling rate at the same time. But people are still work on this research field. Here in, a four-pulse PIV system for achieving high resolution particle images at extremely short time intervals is proposed, which is arranged with a four-pulse laser, two double exposure CCD cameras and DG645 synchronizer. The laser emits a series of four laser sheets with a time interval from 400 ns to any long, the laser energy is 500 mJ per sheet, pulse width is 8 ns and the wavelength is 532 nm. The cameras and laser are exactly synchronized by DG645 to get four time-resolved particle images. In this paper, the four-pulse PIV system is optimized by the liquid crystal optical shutter that controls the light transmittance by an externally applied drive voltage. Besides, the system is applied in supersonic flows to measure the shock train flow structure. The time-resolved particle images with high spatial resolution (2K×2K@10ns, time interval=3 μs) are quite important for the study of unsteadiness and evident oscillation of the shock train, which corresponds to intensive shockwave/boundary layer interaction.

The human eye is more capable of color discrimination in a wide color gamut display. W. A. Thornton hypothesized that they may also enhance color discrimination for color-deficient observers. Compared with normal color vision observers (NCO), anomalous trichromats (AT) have color loss due to difference in cone sensitivity. The large color gamut display system provides a promising solution for solving this problem. We propose a new geometric method to compute the color stereo of AT based on different display color gamuts. The proposed method is fast and efficient to improve color perception for different types of AT.

Virtual studio is a new type of studio technology. People make movies in the virtual digital studio, and after the post-processing system calculates and synthesizes the background, it can produce the same effect as the traditional studio and the real scene. At present, the digital virtual studio basically adopts low spacing LED large screen, which displays real-time images. The image output of real-time engine is combined with camera tracking, and the reasonable lighting and actor position are matched to generate the final image and video completely in the lens.One of the reasons is that the color, CCT (Correlated Color Temperature), CRI (Color Render Index) and other characteristic parameters of some virtual backgrounds are not consistent with the real scene, that is, the spectrum curve of the image is not consistent with the real scene. This paper studies the spectrum curve of the simulation scene, through the actual measurement of the spectral curve data of different real scenes, and according to the real scene spectrum curve to design the algorithm of digital image and video, establish the relevant spectral characteristic spectrum model, do the corresponding digital image processing for the image and video of the virtual background, adjust the relevant CCT, chromaticity, illuminance, and so on Color rendering index and other parameters make the image displayed on the LED screen closer to the real scene and improve the production level of film and television.

Compared with the traditional panel display, the head-mounted display (HMD) is a new technology. When using an HMD, it occupies a significant portion of the eyes’ natural field of view (FOV). Thus, it is necessary to ensure the imaging quality of an HMD, which requires accurate measurement and evaluation. Based on the measurement of panel display, this paper proposes a kind of luminance and chromaticity measuring equipment for HMD by combining an optical fiber spectrometer with a translation platform. The equipment measures various parameters such as brightness, chromaticity, contrast, color gamut, eyebox, etc. To prove the validity of the equipment, several HMDs with different luminance are used for multiple measurements. The final results show that the brightness stability of the equipment reaches 2%, and the chromaticity stability reaches 0.002, which fully meets the measurement requirements of HMD. This equipment has certain reference value for HMD production and testing.

In the field of augmented reality (AR), geometric waveguide has become one of the effective solutions of near-eye display due to their thinness and high transmittance. To obtain clearer viewing experiences, the causes of the stray light are analyzed and solved. The improper tilt angle and the difference in parallelism of the partially reflective mirrors array (PRMA)units may cause stray light or overlapping ghost images, and the refractive indices of the glue and the glass also plays an important role as the appearance of several opposite ghost images. The results show that by adjusting the tilt angle of the PRMA, the stray light within the major area of the eye box can be eliminated. Then a 1.8 mm thick waveguide with stray light of less than 1% is designed. The refractive index of the glass is 1.502 and that of the matched glue is 1.500. The FOV of the designed system is 40°, the size of eye box is 10 mm × 10 mm, and the eye relief is 20 mm. The distribution of the stray light on the observed virtual image is simulated. Finally, a proof-of-concept prototype with eliminated stray light is fabricated and demonstrated.

Color holographic display has been a research hot in many years, since it has huge applications in the holographic display field. In this paper, we employ a laser direct write lithography system, that has the feature of high-resolution drawing and high-speed drawing, to make the color computational holograms with different pixel numbers and pixel pitches. Based on the method of spatial division, the optical experimental system is built, and the diffractive optical elements (DOEs) are fabricated by laser direct writing lithography technology to realize the color holographic display. The experimental results verify the feasibility of this method.

The Micro LED display technology overcomes various shortcomings of the widely used display, and achieves high brightness, high resolution, long lifetime and low power consumption at the same time. In order to control the product quality of Micro LED display, manufacturers generally use chromaticity and brightness measuring instruments to measure the luminous characteristics of sub-pixels. Traditional single-point spectroradiometric colorimeter has low measurement efficiency, and the imaging colorimeter based on tristimulus filters needs chromaticity correction. Compared with them, the spectroscopic imaging colorimeter proposed in this paper characterizes both high speed and accuracy due to concurrent imaging and dispersion. To develop a spectroscopic imaging colorimeter which can meet the performance requirements, this paper analyzed the uncertainty of the sub-pixel chromaticity and brightness measurement of Micro LED display screen, and designed several key specifications based on this. In addition, through the establishment of an analytical model, the variation of the input radiation source subjected to various uncertainty components during the process from radiometric calibration to target measurement are simulated, and to predict the chromaticity and brightness uncertainty under the designed specifications. The results show that for blue, green, red LED light sources and standard illuminant A, under the designed specifications, the uncertainty of chromaticity measurement is about 0.001, and the uncertainty of relative brightness is about 3% and 1%, respectively.

The minimum resolution is one of the most important characteristics of human vision, during the flight of the aircraft, the pilot uses the head-up display(HUD) to observe and distinguish the information of the external scenery. Analyzing the impact of different transmittance HUD combiner under different environment brightness on the external resolution has important instruction and application value for aviation safety. The experiment uses the UASF1951 target plate and the transmittance of HUD combiners under two different environmental brightness. Record the minimum resolution angle and the difference between the two conditions. The result shows that, under the same brightness, the lower the contrast, the weaker the human eye can recognize; the minimum resolvability of the human eye is affected by contrast: when the brightness is lower, the lower the brightness, the higher the minimum contrast requirement for human eye to recognize objects. When the brightness is higher, the minimum contrast requirement for human eye to recognize objects does not change much with brightness, and after the brightness is increased to a certain range, the minimum contrast required by the human eye to recognize the object is almost unchanged. It can be seen that the resolution of the human eye is simultaneously affected by environmental brightness and contrast, and the experimental results basically conform to the Adrian’s Visual Acuity Model.

The Head-up Display is a kind of airborne collimation display system, the parallax will directly affect the collimation accuracy, in order to ensure the pilot to obtain accurate collimation data, the image source must be placed at the best image plane in the assembly process, to get the minimum collimation error. The traditional alignment process is to adjust the position of the image source repeatedly until finding the minimum value of parallax by the method of "swinging head" . This paper analyzes the mathematical relationship between the position of the image source and the parallax of the head-up display optical system, and presents a method for determining the optimal image plane, which can provide support for the alignment of high precision optical systems, it can effectively improve the assembly precision and assembly efficiency, and has high value of popularization and application.

Optical waveguide display technology is an important branch in the field of augmented reality display. Because optical waveguide has the exit pupil expansion function, it can greatly reduce the exit pupil size of relay optical system and realize light and miniaturization design, so it is widely used in head mounted display. In this paper, the imaging principle of optical waveguide optical system is analyzed, the internal light propagation law is studied, an optical waveguide configuration design based on two-dimensional expansion mode is proposed to realize two-dimensional expansion in both horizontal and vertical directions, and a miniaturized relay optical system is designed to reduce the size of the entrance pupil from 5mm × 3mm extended to 23mm × 20mm, the display system of large exit pupil is realized, and the continuity of exit pupil is verified by simulation calculation. This configuration can be used in the field of head mounted display system.

As an important evaluation specification of the helmet mounted display, binocular alignment directly affects the imaging quality of the helmet mounted display, such as the imaging distance and the imaging clarity, and then has a vital impact on the combat effectiveness of the pilot and the aircraft. The traditional detection method relies on the human eye to align the collimator for subjective interpretation, the results are often uncertain because different people have different feelings. This paper proposes an automatic measurement method of binocular alignment based on a single digital camera. This method combines the binocular images of the helmet mounted display into the same optical path by placing a turning prism at the binocular exit pupil position of the helmet mounted display, thereby achieving the purpose of synchronously collecting binocular images by using a single digital camera. Digital image processing technology realizes automatic calculation of binocular alignment indicators, which greatly improves the measurement accuracy and the measurement efficiency. This method uses a turning prism to merge the binocular images of the helmet mounted display into one optical path. The camera can collect binocular images without moving during the measurement process, so it can avoid the straightness error caused by the use of a translation stage, and finally an objective, accurate and fast measurement of binocular alignment specification is obtained. At last, this article discusses the measurement principle of the method in detail, explains the optical-mechanical structure of the binocular alignment measurement equipment in detail, and analyzes the measurement accuracy. Finally, several binocular alignment test results are compared. The test results show that this method has obvious advantages in the measurement accuracy and the measurement efficiency. It can meet the needs of fast, accurate and objective measurement of the binocular alignment of the helmet mounted display, and has the value of a wide range of applications.

Virtual image distance (VID) is a key parameter in augmented reality (AR) or virtual reality (VR) systems and has a great influence on product performance and user experience. Therefore, it is very necessary to measure the VID accurately and efficiently. In this paper, we develop a VID measurement system which needs no mechanical scanning in the measurement process. The VID can be measured in a short period of time based on one single image generated by the AR/VR system. An image-telecentric lens is designed which is used to capture the virtual image. A diaphragm with two pinholes is placed at the entrance pupil plane of the imaging lens. When the imaging lens is not focused on the virtual image, the captured image contains two copies of the virtual image with a certain interval which is proportional to the VID in units of diopters. By calculating the interval, we can obtain the VID. A simulation is performed in LightTools to verify the effectiveness of the measurement system, and the result indicates that the measurement error is 5 mm when the virtual image is at 3 m.

As one of display devices, HUD is mostly used for vehicle navigation display. Now the table-HUD for vision protection is proposed. Through a variety of statistical analysis methods, the influence of different display devices, different types of experiments, different experiment sequences and different objective conditions of the subjects has been studied on the experimental results. It's necessary to evaluate the visual perception and visual comfort of the subjects through subjective and objective evaluation methods. In this paper, three groups of experiments are designed, which are video viewing group, character comparison group and visual task group. The statistical analysis tool SPSS was used to process the experimental data, and the experimental results showed that visual fatigue of different display devices increased with the increase of time. Results also showed that table-HUD was less likely to cause visual fatigue than other display terminals. Experiment sequence and the period of the experiment don't have significant influence on the visual perception and visual comfort of the subjects. Compared with the inter-group experiment and the intra-group experiment, in different groups of experiments, the visual fatigue of subjects in character comparison group was the highest, followed by video viewing group.