Simple method for volumetric thickness measurement using a color camera.

A simple volumetric thickness measurement method for in-line high-speed inspection is proposed. With a color camera alone, spectrally resolved reflectance in a spatial domain is obtained: a Bayer filter spectrally resolves the reflected signal, and a CMOS sensor acquires three multi-spectral reflectances from RGB data at a single shot. To determine an accurate thickness, a modified reflectance is derived to convert a conventional spectral reflectance throughout a wavelength domain into an adequate form in an RGB domain by considering the characteristics of wide-band multi-spectral acquisition. The proposed method is validated by the measurement of a uniformly deposited SiO2 film and a tapered SiNx film.

High-speed computer-generated hologram based on resource optimization for block-based parallel processing: publisher's note.

This publisher's note corrects the author affiliations in Appl. Opt.57, 3511 (2018)APOPAI0003-693510.1364/AO.57.003511.

High-speed computer-generated hologram based on resource optimization for block-based parallel processing.

A huge amount of computation is required to generate a hologram using a computer. In order to speed up the computer-generated-hologram (CGH) operation, we use a parallel programming technique using a general purpose graphic processing unit (GPGPU). In this paper, we propose three techniques to improve CGH performance in the condition using GPU. The first is to remove the memory bottleneck by allocating shared memory and a dedicated thread for this process, and the second is to optimize the block allocation within the GPU using a hologram pixel-based method. The third is to increase the computation time by minimizing the idle region by using multiple threads of host processor and device. When these three techniques were implemented in the GTX 1080Ti GPU, it took 25.05 ms to generate the HD digital hologram with 10 K object points, and compared to the previous research, the performance improvement was at least 1.56 times up to 216.71 times.

ASIC chipset design to generate block-based complex holographic video.

In this paper, we propose a new hardware architecture implemented as a very large scaled integrated circuit by using an application-specific integrated circuit technology, where block-based calculations are used to generate holograms. The proposed hardware is structured to produce a part of a hologram in the block units in parallel. A block of a hologram is calculated using an object point, and then the calculation is repeated for all object points to obtain intermediate results that are accumulated to produce the final block of a hologram. This structure can be used to produce holograms of various sizes in real time with optimized memory access. The proposed hardware was implemented using the Hynix 0.18 µm CMOS technology of Magna Chip, Inc., and it has about 448 K gate counts and a silicon size of 3.592 mm×3.592 mm. It can generate complex holograms and operate in a stable manner at a clock frequency of 200 MHz.

Scalable hologram video coding for adaptive transmitting service.

This paper discusses processing techniques for an adaptive digital holographic video service in various reconstruction environments, and proposes two new scalable coding schemes. The proposed schemes are constructed according to the hologram generation or acquisition schemes: hologram-based resolution-scalable coding (HRS) and light source-based signal-to-noise ratio scalable coding (LSS). HRS is applied for holograms that are already acquired or generated, while LSS is applied to the light sources before generating digital holograms. In the LSS scheme, the light source information is lossless coded because it is too important to lose, while the HRS scheme adopts a lossy coding method. In an experiment, we provide eight stages of an HRS scheme whose data compression ratios range from 1:1 to 100:1 for each layered data. For LSS, four layers and 16 layers of scalable coding schemes are provided. We experimentally show that the proposed techniques make it possible to service a digital hologram video adaptively to the various displays with different resolutions, computation capabilities of the receiver side, or bandwidths of the network.

Hardware architecture of high-performance digital hologram generator on the basis of a pixel-by-pixel calculation scheme.

In this paper we propose a hardware architecture for high-speed computer-generated hologram generation that significantly reduces the number of memory access times to avoid the bottleneck in the memory access operation. For this, we use three main schemes. The first is pixel-by-pixel calculation, rather than light source-by-source calculation. The second is a parallel calculation scheme extracted by modifying the previous recursive calculation scheme. The last scheme is a fully pipelined calculation scheme and exactly structured timing scheduling, achieved by adjusting the hardware. The proposed hardware is structured to calculate a row of a computer-generated hologram in parallel and each hologram pixel in a row is calculated independently. It consists of and input interface, an initial parameter calculator, hologram pixel calculators, a line buffer, and a memory controller. The implemented hardware to calculate a row of a 1920×1080 computer-generated hologram in parallel uses 168,960 lookup tables, 153,944 registers, and 19,212 digital signal processing blocks in an Altera field programmable gate array environment. It can stably operate at 198 MHz. Because of three schemes, external memory bandwidth is reduced to approximately 1/20,000 of the previous ones at the same calculation speed.