Calculation Method Of Computer-generated Hologram Research Articles

Improving image quality of a phase-added stereogram using deep learning

The disadvantages of computer-generated holograms (CGHs) using the direct integral method are the high computational requirements with increased object points and hologram size. This can be addressed by a phase-added stereogram (PAS), a fast calculation method for CGHs. PAS divides the hologram into small blocks and calculates the point-spread functions (PSFs) of the object points in the Fourier domain of each block. The PSF can be approximated using sparse spectra, which accelerate calculations. However, this approximation degrades the image quality. In this study, we improved the image quality of the PAS using deep learning while maintaining high computational speed.

Simple and effective calculation method for computer-generated hologram based on non-uniform sampling using look-up-table.

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.

Fast calculation method for computer-generated holograms using saccade suppression by lowering the resolution based on Fresnel zone plate reduction

Fast calculation method for computer-generated holograms using saccade suppression by lowering the resolution based on Fresnel zone plate reduction

Fast calculation method for computer-generated holograms using saccade suppression by lowering the resolution based on Fresnel zone plate reduction

Fast calculation method for computer-generated holograms using saccade suppression by lowering the resolution based on Fresnel zone plate reduction

Fast calculation method of computer-generated hologram using a depth camera with point cloud gridding

We propose a fast calculation method for a computer-generated hologram (CGH) of real objects that uses a point cloud gridding method. The depth information of the scene is acquired using a depth camera and the point cloud model is reconstructed virtually. Because each point of the point cloud is distributed precisely to the exact coordinates of each layer, each point of the point cloud can be classified into grids according to its depth. A diffraction calculation is performed on the grids using a fast Fourier transform (FFT) to obtain a CGH. The computational complexity is reduced dramatically in comparison with conventional methods. The feasibility of the proposed method was confirmed by numerical and optical experiments.

Calculation of computer-generated hologram (CGH) from 3D object of arbitrary size and viewing angle

We propose a method to calculate computer-generated hologram (CGH) from 3D object of arbitrary size and viewing angle. The spectrum relation between a 3D voxel object and the CGH wavefront is established. The CGH is generated via diffraction calculation from 3D voxel object based on the development of a scaled Fresnel diffraction algorithm. This CGH calculation method overcomes the limitations on sampling imposed by conventional Fourier transform based algorithm. The calculation and reconstruction of 3D object with arbitrary size and viewing angle is achieved. Both of simulation and optical experiments proves the validation of the proposed method.

Depth compensating calculation method of computer-generated holograms using symmetry and similarity of zone plates

Computer-generated hologram (CGH) is a promising 3D display technology while it is challenged by heavy computation load and vast memory requirement. To solve these problems, a depth compensating CGH calculation method based on symmetry and similarity of zone plates is proposed and implemented on graphics processing unit (GPU). An improved LUT method is put forward to compute the distances between object points and hologram pixels in the XY direction. The concept of depth compensating factor is defined and used for calculating the holograms of points with different depth positions instead of layer-based methods. The proposed method is suitable for arbitrary sampling objects with lower memory usage and higher computational efficiency compared to other CGH methods. The effectiveness of the proposed method is validated by numerical and optical experiments.

Hidden surface removal of computer-generated holograms for arbitrary diffraction directions

A fast calculation method for computer-generated holograms for hidden surface removal is proposed. In this method, a three-dimensional object is considered as a set of point light sources emitting light rays. To achieve the hidden surface removal, only appropriate light rays are selected according to their geometrical position, which are then converted into a Fourier spectrum of the wavefront. After the Fourier spectrum on the spherical surface is obtained, diffraction in arbitrary directions is calculated. Numerical simulation of a series of diffracted wavefronts onto arbitrary observation planes has been demonstrated to verify the effectiveness of our proposal.

Calculation method of CGH for Binocular Eyepiece-Type Electro Holography

We had researched about eyepiece-type electro holography to display 3-D images of larger objects at wider angle. We had enlarged visual field considering depth of object with Fourier optical system using two lenses. In this paper, we extend our system for binocular. In the binocular system, we use two different holograms for each eye. The 3-D image for left eye should be observed like the real object observed using left eye and the same for right eye. So, we propose a method of calculation of computer-generated hologram (CGH) transforming the coordinate system of the model data to make two holograms for binocular eyepiece-type electro holography. The coordinate system of original model data is called the world coordinate system. The left and the right coordinate system are transformed from the world coordinate system. We also propose the method for correcting the installation error that occurs when placing the electronic and optical devices. The installation error is calculated and the model data is corrected using the distance between measured position and setup position of the reconstructed image Optical reconstruction experiments were carried out to verify the proposed method.

Calculation method for computer-generated holograms considering various reflectance distributions based on microfacets with various surface roughnesses

Computer-generated holograms are generated by three-dimensional technology, and they can be used to reconstruct natural and virtual objects by simulating light waves based on holography. This research was an improvement on previous work that took into consideration reflectance distributions from the various roughnesses of objects. The previous work generated roughness by using a simple model, so that only simple roughness was generated. The proposed method generated more complex roughness than that in the previous work, and the influence of roughness on the reflectance distributions was investigated. Computer simulations, which were compared with the reflectance distributions from the various roughnesses, were carried out. Moreover, computational and optical reconstructions were carried out as examples of reconstructions. As a result of the experiments, we confirmed that the various roughnesses actually influenced the reflectance distributions.

Calculation method for computer-generated holograms with cylindrical basic object light by using a graphics processing unit

It takes an enormous amount of time to calculate a computer-generated hologram (CGH). A fast calculation method for a CGH using precalculated object light has been proposed in which the light waves of an arbitrary object are calculated using transform calculations of the precalculated object light. However, this method requires a huge amount of memory. This paper proposes the use of a method that uses a cylindrical basic object light to reduce the memory requirement. Furthermore, it is accelerated by using a graphics processing unit (GPU). Experimental results show that the calculation speed on a GPU is about 65 times faster than that on a CPU.