RESUMO
In this paper, we propose a convolutional symmetric compressed look-up-table (CSC-LUT) method to accelerate computer-generated hologram (CGH) computation based on the Fresnel diffraction theory and LUT. The proposed method can achieve one-time high-quality fast generation of color holograms by utilizing dynamic convolution operation, which is divided three processes. Firstly, the pre-calculated data of maximum horizontal modulation factor is compressed in 1D array by coordinate symmetry. Then, the test object is resampled to satisfy convolutional translation invariance. Finally, the dynamic convolution operation is used to simplify CGH computation process rather than the point-by-point computation. Numerical simulation and optical experimental results show that our proposed method can achieve faster computation speed, higher reconstruction quality and wider application compared to conventional SC-LUT method. The further optimization method for parallel acceleration on the GPU framework can achieve real-time (>24fps) color holographic display corresponding to three perspectives of a 3D scene.
RESUMO
The spatial frequency of the reconstructed image of planar computer-generated hologram(CGH) is limited by the sampling interval and the lack of thickness. To break through this limitation of planar CGH, we propose a new computer-generated volume hologram(CGVH) for full-color dynamic holographic three-dimensional(3D) display, and an iteration-free layered CGVH generation method. The proposed CGVH is equivalent to a volume hologram sampled discretely in three directions. The generation method employs the layered angular spectral diffraction to calculate the light field in the layered CGVH, and then encodes it into a CGVH. Numerical simulation results show that the CGVH can accurately reconstruct full-color 3D objects, where better imaging quality, more concentrated diffraction energy, denser reconstructed spatial frequency information, and larger viewing angle are achieved. The proposed CGVH is expected to be applied to realize dynamic modulation, wavelength multiplexing, and angle multiplexing in various optical fields in the future.
RESUMO
We propose a holographic display system for complex amplitude modulation (CAM) using a phase-only spatial light modulator (SLM) and two polarization gratings (PG). The two sub-holograms of the complex-amplitude computed generated hologram (CGH) are loaded in different regions of SLM. Two diffractive components couple in space after longitudinal migration from the double PGs, and finally interfered through the line polarizer. The influence of the system error on the reconstructed image quality is analyzed, which provides a theoretical assessment for adding pre-compensation to CGH to compensate the system error. Moreover, on the base of the proposed system, a large depth of field and enlarged display area display is realized and the real-time display can be achieved because of the analytical complex-amplitude computed generated hologram. The optical experimental results show that the proposed system has high energy efficiency, and can provide high-quality holographic display with a large depth of field and enlarged display area.
RESUMO
In this Letter, we introduce a computer-generated hologram (CGH) optimization method to enhance the depth cue based on complex amplitude modulation (CAM). An iterative algorithm is designed to generate the optimized random phase (ORAP) according to the size of the target image and the bandwidth limitation condition. The ORAP with limited bandwidth is used as the initial phase of the target image and the hologram is encoded based on the analytical formula. Our proposal can maintain the advantages of CAM and achieve holographic three-dimensional (3D) display with an enhanced depth cue. It is expected that the proposed method could be widely used in holographic field in the future.
RESUMO
One of the biggest challenges for large size three-dimensional (3D) holographic display based on the computer-generated hologram (CGH) is the trade-off between computation time and reconstruction quality, which has limited real-time synthesis of high-quality holographic image. In this paper, we propose a superpixel-based sub-hologram (SBS) method to reduce the computation time without sacrificing the quality of the reconstructed image. The superpixel-based sub-hologram method divides the target scene into a collection of superpixels. The superpixels are composed of adjacent object points. The region of the superpixel-based sub-hologram corresponding to each superpixel is determined by an approximation method. Since the size and the complexity of the diffraction regions are reduced, the hologram generation time is decreased significantly. The computation time has found to be reduced by 94.89% compared with the conventional sub-hologram method. It is shown that the proposed method implemented on the graphics processing unit (GPU) framework can achieve real-time (> 24 fps) color three-dimensional holographic display with a display size of 155.52 mm × 276.48 mm.
RESUMO
In this Letter, we introduce a multiplexing encoding method with a bandwidth constraint strategy to realize a color dynamic holographic display based on complex amplitude modulation (CAM). The method first uses the angular spectrum method (ASM) with a bandwidth constraint strategy to calculate the diffracted wavefronts of red, green, and blue channels. Then the diffracted wavefronts of three channels are synthesized into a color-multiplexed hologram (CMH) based on the double-phase method after they interfere with off-axis reference lights. The color 3D objects can be reconstructed when the combination of red, green, and blue lights is used to illuminate the double-phase CMH, and a 4f system with a slit filter is introduced to extract the desired spectrums. Numerical simulations and optical experiments are performed to verify the effectiveness of the proposed method and the results show that it can achieve a color holographic display with high quality. Our proposal is simple and fast, and the display system is compact. It is expected that our proposed method could in future be widely used in the holographic field.
RESUMO
Holographic three-dimensional display is an important display technique because it can provide all depth information of a real or virtual scene without any special eyewear. In recent years, with the development of computer and optoelectronic technology, computer-generated holograms have attracted extensive attention and developed as the most promising method to realize holographic display. However, some bottlenecks still restrict the development of computer-generated holograms, such as heavy computation burden, low image quality, and the complicated system of color holographic display. To overcome these problems, numerous algorithms have been investigated with the aim of color dynamic holographic three-dimensional display. In this review, we will explain the essence of various computer-generated hologram algorithms and provide some insights for future research.
RESUMO
Nowadays, curved computer-generated holograms are widely applied to increase the field of view. However, heavy computational load restricts the development of curved computer-generated holograms. In this paper, we propose a two-step acceleration calculation method to generate curved holograms by using the intermediate plane, which is placed between the object and a curved computer-generated hologram. The first step is the calculation of the intermediate plane by an improved accurate highly compressed lookup-table method. In the second step, we execute diffraction calculation from the intermediate plane to obtain a curved computer-generated hologram. Numerical simulations and optical experiments are performed to demonstrate that the proposed method is an efficient method for reducing calculation time. Additionally, the increase of field of view using a curved hologram is also numerically demonstrated. It is expected that our method can be combined with a curved display screen to realize three-dimensional holographic displays in the future.
RESUMO
In this paper, we propose a method to implement a speckleless color dynamic three-dimensional holographic display by modulating amplitude and phase distribution simultaneously. Computer-generated holograms are calculated with an initial uniform phase, and the speckle noise of reconstructed images is suppressed effectively. We perform both numerical simulations and optical experiments to demonstrate the effectiveness of the proposed method. The numerical simulations show that the proposed method can achieve speckleless reconstruction and the optical experiments provide a good color dynamic display effect. It is expected that the proposed method could be widely applied to realize high-quality color dynamic holographic displays in the future.
RESUMO
We present an erratum to our recent work [Appl. Opt.60, 7844-7848 (2021)APOPAI0003-693510.1364/AO.433422] that corrects errors in Eqs. (5) and (8). All the simulations and experiments in the original paper were performed using the correct equations, and therefore, the corrections do not affect the results and conclusions of the original paper.
RESUMO
A curved hologram can increase the view angle in a holographic display. The huge data processing and curved computer-generated hologram (CCGH) computation time is still a challenge for real-time display. Here, we propose two fast methods to accelerate the computation. The first one is a diffraction compensation (DC) method where the diffraction calculation is from the wave-front recording plane (WRP) to a CCGH. The other is an approximate compensation (AC) method that adds a phase difference distribution to the WRP to obtain the CCGH. Numerical simulations and optical experiments are performed, which demonstrate that the two methods are feasible and the computation time is dramatically reduced. The AC method can further reduce time significantly compared with the DC method. And the image quality for proposed methods is similar. It is expected that these fast methods can be combined with curved display screen and flexible display materials in the future.
RESUMO
In this paper, we propose a fast calculation method using look-up table and wavefront-recording plane. Wavefront-recording plane method consists of two steps: the first step is the calculation of a wavefront-recording plane which is placed between the object and the hologram. In the second step, we obtain the hologram by executing diffraction calculation from the wavefront-recording plane to the hologram plane. The first step of the previous wavefront-recording plane method is time consuming. In order to obtain further acceleration to the first step, we propose high compressed look-up table method based on wavefront-recording plane. We perform numerical simulations and optical experiments to verify the proposed method. Numerical simulation results show that the calculation time reduces dramatically in comparison with previous wavefront-recording plane method and the memory usage is very small. The optical experimental results are in accord with the numerical simulation results. It is expected that proposed method can greatly reduce the computational complexity and could be widely applied in the holographic field in the future.
RESUMO
Heavy computational complexity and imprecise reconstruction of objects are crucial problems in computer-generated holograms. In this paper, we propose a non-uniform sampling based on novel compressed look up table method to generate holograms. The method consists of two steps: in the first step, the non-uniform basic modulation factors are precalculated and stored in look-up-table. Secondly, fringe patterns for other points are obtained by simply shifting and multiplying the pre-calculated non-uniform basic modulation factors, and the final computer-generated hologram is obtained by adding them all together. The proposed method eliminates the redundant information properly and modulates the reconstructed images precisely. Numerical simulation results show proposed method reduces the memory usage, speeds up computation time and the quality of reconstructed images do not degrade evidently compared with uniform sampling method. Optical experiments results are in good agreement with numerical simulation results. The proposed method is simple, effective and could be applied in the holographic field in the future.
RESUMO
In this paper, we propose an accurate high-compressed look-up-table method that uses less memory to generate the hologram. In precomputation, we separate the longitudinal modulation factors and only calculate the basic horizontal and vertical factors. Therefore, we obtain other horizontal and vertical modulation factors of object points by simply shifting the basic horizontal and vertical modulation factors while computing holograms. We perform numerical simulations and optical experiments to verify the proposed method. Numerical simulation results show that the proposed method has the least memory usage, the fastest computation time and no distortion. The optical experimental results are in accord with the numerical simulation results. The proposed method is simple and effective to calculate computer-generated holograms for color dynamic holographic display with high speed, less memory usage and high accuracy that could be applied in the holographic field in the future.
RESUMO
A curved multiplexing method based on the curved computer-generated hologram (CCGH) is proposed theoretically and demonstrated experimentally to increase field of view (FOV) and spatial bandwidth. Point source method is used to calculate the CCGH. Curved multiplexing method can be used to reconstruct different 3D objects at the same position by bending a composed hologram which is synthesized of several CCGHs with different central angles. Numerical simulations and optical experiments demonstrate that the method is feasible. It could have a good prospect by combining with the curved display screen and flexible display materials.
RESUMO
In order to suppress the speckle noise on a holographic display, we propose two design methods to initialize the phase to generate a computer hologram illuminating with partially coherent light. We introduce an initial phase of the image in consideration of the relationship of gray value among adjacent pixels when generating the computer hologram. After simulations, we compare these two methods and conclude that one is better than the other in terms of running speed or quality of the reconstructed image. Finally, we perform experiments to verify the theory. It is expected that these methods can greatly enhance the quality of reconstructed images and could be widely applied in the holographic field in the future.
