Nagaaki Ohyama

Bio: Nagaaki Ohyama is an academic researcher from Tokyo Institute of Technology. The author has contributed to research in topics: Color image & Image processing. The author has an hindex of 32, co-authored 258 publications receiving 4480 citations. Previous affiliations of Nagaaki Ohyama include National Institute of Information and Communications Technology.

Multiprimary color display using a holographic optical element

Abstract: In order to reproduce the natural color of object on color display devices, such as CRT and LCD (liquid crystal display), the saturation of the reproduced color is limited by the gamut of the display device. This paper presents a method to increase the color gamut by using more than three primary colors generated by a holographic optical element (HOE). The light diffracted by HOE is used to generate multiprimary colors, and the color image with extended color gamut is displayed by LCD device. Both transmission- and reflection-type systems suitable for projection displays are proposed, and the capability of increasing the gamut is discussed. The experimental result using transmission-type HOE is also demonstrated.

Image pickup system for reproducing image data using sensitivity function

Abstract: In a sensitivity function measuring unit, a CMD for picking up a beam from a light source is arranged through a photographic lens and a liquid crystal lens. A preamplifier, an A/D converter, a subtractor, a sensitivity function memory, a compressor, and R, G, and B sensitivity function memories are sequentially connected to the CMD through a switching circuit. An image reproducing unit for reproducing an original image using a sensitivity function calculated by the sensitivity function measuring unit is connected to a calculator for calculating a reproduced image, a frame memory for storing an image signal picked up by the CMD, and calculators for calculating sensitivity functions stored in the sensitivity function memories. The image reproducing unit is also connected to a display unit.

Color correction of pathological images for different staining-condition slides

Abstract: The color of hematoxylin & eosin (H&E) stained tissue image varies with the staining conditions and with the characteristics of the microscope and imaging devices. This color variation affects the diagnostic examination. This paper proposes a color correction method for images of pathological slides prepared under inappropriate staining-condition. In the proposed method, the spectral transmittance obtained by a multispectral digital camera is utilized to estimate the amount of dye for each pixel. Subsequently the amount of dye is adjusted based on the chemical kinetic equation by digital process, so that the dye amount distribution would be equivalent to that of the reference slide, which is prepared under ideal staining conditions. Through the experiments using the H&E stained slides of liver tissue, the color was almost successfully corrected by the proposed method.

A method for the unified representation of multispectral images with different number of bands

Abstract: We propose a simple but useful method to represent multispectral images captured by multispectral cameras (MSC) with different numbers of bands. When considering accurate color reproduction under an arbitrary illuminant, it is necessary to represent them in a common space with sufficient accuracy of spectral information, estimated from each multispectral image. The principal component analysis (PCA) is useful to reduce the high dimension of the spectral information. However, PCA-based methods may cause both large differences in dynamic range between coefficients of the basis functions derived from the PCA and negative pixel values, therefore, it is not easy to handle or edit coefficient images. To solve the problem, we propose the idea of a virtual multispectral camera (VMSC) that transforms real multispectral images into virtual multispectral images. We design the sensitivities of the VMSC properly, and our unified representation can avoid some disadvantages of conventional PCA-based methods. We experimentally demonstrate the color reproduction accuracy of our method by comparing it with the PCA-based methods, and we show an example of a virtual multispectral image transformed by our method.

Natural color reproduction system for telemedicine and its application to digital camera

Abstract: For a reliable diagnosis via visual telecommunication systems, it is very important to reproduce patient images with correct color. But it is not certain by conventional color imaging systems especially when the illumination of observing site is different from that of the image capturing site. We present a natural color reproduction system for telemedicine. In this system, the color of a patient under observing illumination is calculated from multispectral image. For accurate color reproduction, the spectral reflectance is calculated using principal components of human skin in the process. The color image is displayed on a calibrated display device. In the experiment, it is confirmed that the system realizes good accuracy in the color reproduction of human skin from 10 band multispectral image. And for simplification of the system we also adapted this process to commercial digital RGB camera.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Intelligent electronic appliance system and method

Abstract: An intelligent electronic appliance preferably includes a user interface, data input and/or output port, and an intelligent processor. A preferred embodiment comprises a set top box for interacting with broadband media streams, with an adaptive user interface, content-based media processing and/or media metadata processing, and telecommunications integration. An adaptive user interface models the user, by observation, feedback, and/or explicit input, and presents a user interface and/or executes functions based on the user model. A content-based media processing system analyzes media content, for example audio and video, to understand the content, for example to generate content-descriptive metadata. A media metadata processing system operates on locally or remotely generated metadata to process the media in accordance with the metadata, which may be, for example, an electronic program guide, MPEG 7 data, and/or automatically generated format. A set top box preferably includes digital trick play effects, and incorporated digital rights management features.

Ergonomic man-machine interface incorporating adaptive pattern recognition based control system

Abstract: An adaptive interface for a programmable system, for predicting a desired user function, based on user history, as well as machine internal status and context. The apparatus receives an input from the user and other data. A predicted input is presented for confirmation by the user, and the predictive mechanism is updated based on this feedback. Also provided is a pattern recognition system for a multimedia device, wherein a user input is matched to a video stream on a conceptual basis, allowing inexact programming of a multimedia device. The system analyzes a data stream for correspondence with a data pattern for processing and storage. The data stream is subjected to adaptive pattern recognition to extract features of interest to provide a highly compressed representation which may be efficiently processed to determine correspondence. Applications of the interface and system include a VCR, medical device, vehicle control system, audio device, environmental control system, securities trading terminal, and smart house. The system optionally includes an actuator for effecting the environment of operation, allowing closed-loop feedback operation and automated learning.

Image indexing using color correlograms

Abstract: We define a new image feature called the color correlogram and use it for image indexing and comparison. This feature distills the spatial correlation of colors, and is both effective and inexpensive for content-based image retrieval. The correlogram robustly tolerates large changes in appearance and shape caused by changes in viewing positions, camera zooms, etc. Experimental evidence suggests that this new feature outperforms not only the traditional color histogram method but also the recently proposed histogram refinement methods for image indexing/retrieval.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Abstract: A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.