Multicriteria optimality for iterative encoding of computer-generated holograms

We introduce a process for optically reconstructing full-color holographic images recorded by optical scanning holography. A complex RGB-color hologram was recorded and converted into a binary hologram using a direct binary search (DBS) algorithm. The generated binary hologram was then optically reconstructed using a spatial light modulator. The discrepancies between the reconstructed object sizes and colors due to chromatic aberration were corrected by adjusting the reconstruction parameters in the DBS algorithm. To the best of our knowledge, this represents the first optical reconstruction of a full-color hologram recorded by optical scanning holography.

This paper presents a video halftoning for electronic papers. Based on the direct binary search (DBS) algorithm, the video frames are halftoned in order. The proposed approach tends to minimize the flickers on the stationary regions by referring to the previous frame and processing the pixels in pseudo random ordering. The main feature of the proposed approach is that the frame can be gotten with an acceptable result in one iteration. The experimental results show the proposed approach significantly improves the video quality compared with the error diffusion based and the original DBS.

The reconstructed image of the size-invariant visual cryptography (VC) is inevitably accompanied by the loss of secret image information and the degradation of perceptual quality. Here, the halftone technique comes to the forefront since it can realistically simulate the grayscale image from a discrete binary image. Thus, by combining VC sharing with grayscale image halftone technique, this paper proposes a size-invariant VC scheme for grayscale image underpinned by the efficient direct binary search (EDBS) algorithm, in which the multi-pixel encryption VC sharing is adopted into the EDBS halftone process. Through local optimizations and global iterations, the optimal reconstructed image is obtained. To further enhance the contrast of the reconstructed image with limited computational power, the image information is probabilistically extracted according to the inverse mapping in the codebook. It is theoretically proved that the proposed scheme is as secure as the traditional VC, while its effectiveness is validated through experiments and comparative analyses.

Computer-generated holograms (CGH’s) synthesized by the iterative direct-binary-search (DBS) algorithm yield lower reconstruction error and higher diffraction efficiency than do CGH’s designed by conventional methods, but the DBS algorithm is computationally intensive. A fast algorithm for DBS is developed that recursively computes the error measure to be minimized. For complex amplitude-based error, the required computation for an L-point CGH is reduced by a factor of (L/log2L)1/2. The fast intensity-based algorithm is substantially more complicated, and modifications are considered in order to make the algorithm more efficient. An acceleration technique that attempts to increase the rate of convergence of the DBS algorithm is also investigated.

A region based random multi-pixel search algorithm to improve the binary hologram reconstruction quality

Spatial Light Modulators currently available lack of resolution to display large hologram, it is then necessary to find some technique to broaden the size of the reconstructed image. For example, time multiplexing can be use to tile several elementary holograms via a high speed scanning system. However, the best compromise to exploit the bandwidth of the SLM is to use binary data, holograms acquired from real objects must therefore be converted from gray scale to a binary format. The Direct Binary Search algorithm (DBS) is a method that has been developed to generate binary holograms, but the resulting holograms can reconstruct the objects only in a 2D plane. We propose to adapt the DBS algorithm to reconstruct holograms instead of directly reconstructing the image, our proposed method preserve therefore 3D information.

Look-up table (LUT) halftoning is an efficient way to construct halftone images and approximately simulate the dot distribution of the learned halftone image set. In this paper, a general mechanism named multiple look-up table (MLUT) halftoning is proposed to generate the halftones of direct binary search (DBS), whereas the high efficient characteristic of the LUT is still preserved. In the MLUT, the standard deviation is adopted as an important feature to classify various tables. In addition, the proposed quick standard deviation evaluation is employed to yield an extremely low computational complexity in calculating the standard deviation. In the parameter optimization, the autocorrelation is adopted because it can fully characterize the periodicity of dot distribution. Experimental results demonstrate that the dot distribution generated by the proposed method approximates to that of the DBS, which enables the proposed scheme as a very competitive candidate in the copying and printing industry.

Dot diffusion is an efficient approach which utilizes concepts of block-wise and parallel-oriented processing to generate halftones. However, the block-wise nature of processing reduces image quality much more significantly as compared to error diffusion. In this work, four types of filters with various sizes are employed in co-optimization procedures with class matrices of size 8 n 8 and 16 x 16 to improve the image quality. The optimal diffused weighting and area are determined through simulations. Many well-known halftoning methods, some of which includes direct binary search (DBS), error diffusion, ordered dithering, and prior dot diffusion methods, are also included for comparisons. Experimental results show that the proposed dot diffusion achieved quality close to some forms of error diffusion, and additionally, superior to the well-known Jarvis and Stucki error diffusion and Mese's dot diffusion. Moreover, the inherent parallel processing advantage of dot diffusion is preserved, allowing us to reap higher executing efficiency than both DBS and error diffusion.

The motivation behind this paper is to encode a secret picture SI into n shares of halftone pictures in VC scheme. In this paper it proposes a strategy for encoding a shading picture into n significant halftone shares utilizing the scheme of halftone visual cryptography secret pixels encrypted into shares acquaint commotion with the halftone pictures, the perceptual mistakes between the halftone shares and the continuous-tone pictures are minimized as for a human visual framework (HVS) demonstrate. The secret picture can be effectively decoded without demonstrating any impedance with the share pictures. The security of our strategy is ensured by the properties of VC. The proposed technique can encoded the secret pixels into the shares using the method of direct binary search (DBS) halftoning strategy for color pictures. The mistake between the halftone shares and the continous-tone pictures are minimized as for a human visual framework (HVS) show The recreation comes about portray that our proposed technique can enhance altogether the halftone picture quality for the encoded offers of grayscale pictures and colors pictures also utilizing the strategy for DBS to enhance the nature of halftone picture and revealed secret picture.

This work employs the well known weighted least squares method to optimization to produce halftone images using improved K-means clustering theory. Our algorithm applies to both a printer model and a model for the human visual system (HVS). In this algorithm, the improved K-means clustering method is used to segment an image several regions. In the halftone process, each clustering uses the weighted least-squares model-based(WLSMB) algorithm by use of direct binary search iterative method to obtain halftone image. Analysis and simulation results show that the proposed algorithm produces better gray-scale halftone image quality when we increase the number of clustering with a certain range and outperforms least-squares model-based algorithm in the PSNR (Peak Signal Noise Ratio), WSNR (Weighted Signal Noise Ratio) criteria.

Direct binary search is used to optimize spatially dithered distributions of transparent and opaque pixels for beam shaping, improving the performance of spatial gain precompensation for laser systems, and wavefront metrology by optical differentiation.

In this paper, a halftoning-based watermarking method is presented. This method enables high pixel-depth watermark embedding, while maintaining high image quality. This technique is capable of embedding watermarks with pixel depths up to 3 bits without causing prominent degradation to the image quality. To achieve high image quality, the parallel oriented high-efficient direct binary search (DBS) halftoning is selected to be integrated with the proposed orientation modulation (OM) method. The OM method utilizes different halftone texture orientations to carry different watermark data. In the decoder, the least-mean-square-trained filters are applied for feature extraction from watermarked images in the frequency domain, and the naïve Bayes classifier is used to analyze the extracted features and ultimately to decode the watermark data. Experimental results show that the DBS-based OM encoding method maintains a high degree of image quality and realizes the processing efficiency and robustness to be adapted in printing applications.

This work presents binary hologram generation from images of a real object acquired from a Kinect sensor. Since hologram calculation from a point-cloud or polygon model presents a heavy computational burden, we adopted a depth-layer approach to generate the holograms. This method enables us to obtain holographic data of large scenes quickly. Our investigations focus on the performance of different methods, iterative and noniterative, to convert complex holograms into binary format. Comparisons were performed to examine the reconstruction of the binary holograms at different depths. We also propose to modify the direct binary search algorithm to take into account several reference image planes. Then, deep scenes featuring multiple planes of interest can be reconstructed with better efficiency.

An optimal design approach based on the mosaic-like structure concept for NRD guide devices is proposed in this paper. In order to achieve efficient design with high transmission efficiency, and minimum computational effort, we employ recently proposed two-dimensional full-vectorial finite element method (2D-FVFEM) for numerical simulations. Non-linear direct binary search algorithm is implemented as an optimization problem to obtain the optimal NRD guide device at operating frequency 60GHz. In order to prove the significance of the proposed optimization approach we designed an NRD 90°-bend guide and it achieves more than 99% transmission efficiency. The analysis of numerical results by 2D-FVFEM are also verified by 3D-FVFEM.

Print misregistration, or color misregistration, is a common occurrence in printing where different CMYK ink colors do not all line up when the respective colors are placed, resulting in unwanted print artifacts such as blurring, colors shifting, and gaps between the color channels where they are supposed to be stacked. To mitigate this issue, we developed a method called Halftone Accounting for Misregistration (HAM), where we leverage the framework of color halftoning using multistage, multipass, clustered direct binary search algorithm (MS-MP-CLU-DBS) with a modified cost function to generate a screen that minimizes the appearance of misregistration. The result is a halftone screen design that is more robust to variations due to misregistration, which minimizes the above-mentioned unwanted print artifacts.