Acceleration and expansion of a photorealistic computer-generated hologram using backward ray tracing and multiple off-axis wavefront recording plane methods.

Holograms can reconstruct the light wave field of three-dimensional objects. However, the computer-generated hologram (CGH) requires much calculating time. Here we proposed a CGH generation algorithm based on backward ray tracing and multiple off-axis wavefront recording planes (MO-WRP) to generate photorealistic CGH with a large reconstruction image. In this method, multiple WRPs were placed parallelly between the virtual object and the hologram plane. Virtual rays were emitted from the pixel of WRPs and intersect with the object. The complex amplitude of WRPs is then determined by illumination module, such as Phong reflection module. The CGH was generated by the shifted Angular Spectrum Propagation (ASP) from WRPs to the hologram plane. Experimental results demonstrate the effectiveness of this method, and the CGH generation rate is 37.3 frames per second (1 WRP) and 9.8 frames per second (2×2 WRPs).

Image quality enhancement and computation acceleration of 3D holographic display using a symmetrical 3D GS algorithm.

The 3D Gerchberg-Saxton (GS) algorithm can be used to compute a computer-generated hologram (CGH) to produce a 3D holographic display. But, using the 3D GS method, there exists a serious distortion in reconstructions of binary input images. We have eliminated the distortion and improved the image quality of the reconstructions by a maximum of 486%, using a symmetrical 3D GS algorithm that is developed based on a traditional 3D GS algorithm. In addition, the hologram computation speed has been accelerated by 9.28 times, which is significant for real-time holographic displays.

Brightness Prediction of Large Color Gamut Laser Display Devices.

A brightness-perceived color appearance model tailored for large gamut display devices, exemplified by laser displays, was investigated. Psychophysical experiments on the brightness matching of 30 color stimuli with achromatic white light were conducted by 16 observers. The analysis compares the performance of a number of existing color appearance models and equivalent luminance models in predicting brightness. None of the models performed acceptably due to a severe underestimation of the Helmholtz-Kohlrausch (H-K) effect. A modified model of perceived brightness based on CAM16, taking into account the H-K effect, is proposed. Evaluated by psychophysical experiments, the proposed model exhibits a superior performance compared to the preceding models, especially within the extensive color gamut range stipulated by BT.2020. The results help to optimize the design of laser displays with a wide color gamut and high perceived brightness.

High Refractive Index Monomers for Improving the Holographic Recording Performance of Two-Stage Photopolymers.

Photopolymers hold great promise for the preparation of transparent volume holographic gratings (VHG), which are core optical elements in many application fields. To improve the holographic recording property of a two-stage photopolymer, four new (meth)acrylate monomers (CTA, CTMA, CTBA, CTBMA) with high refractive indices (1.59-1.63) are designed and synthesized in this study. Using them as one writing monomer, a series of photopolymer samples with different formulations and thicknesses are fabricated for holographic recording. Among them, a formulation containing 9 wt % CTMA shows the best performance. Using it as a recording medium, a VHG with high resolution and diffraction efficiency is constructed. Its refractive index modulation reaches 0.046. Moreover, its total transmittance within 400-800 nm achieves 96.62% after photobleaching. The results indicate that the CTMA-based formulation has great application potential in developing high-performance transparent VHG.