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The dynamic zone-plate interferometer (DZPI) has the ability to measure aspherical surfaces without any special optical elements such as a computer generated hologram or a standard surface. This paper discusses systematic errors of the DZPI caused by the inaccuracy of optical system parameters such as the focal length of the zone plate, the distance between the zone-plate and the mirror under test, and the wavelengths of the source. The accuracy of the measurement is estimated.

In a fringe scanning interferometer, if the digitized intensity data do not change sinusoidally due to, for example, nonlinearity of the detector or to the fringe shape itself, systematic errors will occur in determining the phases in an interferogram. Unless this nonlinearity is compensated for, the three-bucket or four-bucket method will be unable to determine the phases accurately. This problem is discussed and some examples are shown of the necessary number of sampling steps to reduce under-sampling errors.

Recently, medical endoscopes with CCD camera devices have been developed and aroused great interest because of a larger number of picture elements than conventional endoscopes with optical fiber bundles. One type of image acquisition system is such that color images are sequentially taken with red (R), green (G) and blue (B) illuminations. This type has the merit of a good spatial resolution but constructed images are sometimes blurred or color shifted because of a rapid object motion while recording three primary color images. Since three primary color images have strong correlation, this problem can be solved by a compensation method using phase correlation l). This paper shows an advanced technique named the color deviation method which is much simpler than the previous method.

Reflected light with a grazing angle from a gear tooth surface is put into a hologram recording a standard surface. Deviation of reconstructed wavefront from the standard one gives a surface error, and is detected by a simple photodetector with a small pinhole and by the fringe scanning technique.

This paper proposes some advanced data acquisition methods for quantitative single photon emission CT. One example of such methods is the odd number angular sampling method over 360 degrees for a widely distributed object, and the other is fine angular sampling of 180 degrees for a nonsymmetrically localized small object in an attenuation cross section. The image quality, such as the spatial resolution and the signal-to-noise ratio, becomes better than that reconstructed from conventional conjugate projection data. The reconstruction technique used in computer simulation is the iterative correction matrix method, but other techniques are also applicable. Comparison between the weighted back projection method and the correction matrix method is also presented.

A multiplex hologram (cylindrical holographic stereogram) was successfully made from three-dimensional (3D) surface reconstruction CT images of a child with plagiocephaly. This method appears to be suitable as one of the projectional aids of 3D surface reconstruction CT images that are proving useful in plastic and reconstructive surgery. The principle of the method is described. Also discussed is the possibility of developing a computer-aided hologram synthesizing system that could be used for images obtained with U-arm X-ray equipment (by either cinefilm, or videotape, or digital subtraction angiography) or by CT as well as MR. For practical use, it is necessary for the hologram to be synthesized in a short time. One of the key problems in developing such a machine is the need for an incoherent-to-coherent image converter.

The reconstruction of electric current distribution in a human brain from measured magnetic fields has been studied by many researchers. Most of these studies model the human head as a sphere casing filled with a homogeneous conductive medium in which only one electric current dipole exists. In case of complex current distribution, however, single dipole model is a poor match, and thus the current distribution should be modeled as multiple current dipoles.

This paper proposes a dynamic zone plate interferometer (DZPI), which has a possibility of measuring aspherical surfaces without the need of either a standard surface or of a computer generated holograms (CGH). The accuracy of surface error measurments can be improved by using a fringe analysis method up to about λ/100. An experimantal result is also presented.

A hybrid real -time correlation system of aerial stereo photographsR. T. Hong*, J. Tsujiuchi, N. Ohyama and T. HondaImaging Science and Engineering Laboratory, Tokyo Institute of Technology4259 Nagatsuta, Midori -ku, Yokohama, 227, JapanAbstractA digital- optical hybrid system composed of a computer and a coherent optical filteringsystem is successfully applied to perform a real -time correlation of aerial stereo photo-graphs. A LCLV ( Liquid Crystal Light Valve ) as an incoherent -to- coherent convertor and athermoplastic photoconductor material for holographic recording of MSF ( Matched Spatial Fil-ter ) are used, and a sharp correlation peak with a good SNR is obtained.IntroductionIn contour mapping of aerial stereo photogrammetry, a pair of stereo aerial photographsis taken at two view points Otand O separated by the base line B as shown in Fig.l. The re-lative variation of the coordinates of the same object in the stereo pair photographs ( theparallax ) is used to determine the height of the object. Fig.l refers to the simple andideal case of vertical photographs, in which the camera axes are parallel with each otherand perpendicular to the reference plane. The height He and Hdof two objects C and D with re-spect to the reference plane are obtained by

Despite evidences from human vision research (1) that spatial and color characteristics of images are strongly related, the use of color for recognition purposes has received little attention. However,in the framework of the development of increasingly versatile machine vision systems, the introduction of the color feature seems to be a rather natural step. A color approach is obviously not always possible and justified and therefore we are interested in cases where color images are at hand and where recognition accuracy is more important than processing speed. In this work we extend the concepts introduced earlier (2) andpropose to find an optimal generalized color plane in which to carry out the correlation operation. The optimality is defined in terms of the maximization of the peak-to-deviation ratio in the correlation plane. As an application we consider the retrieval of the mucosal surface structure from stereo pairs taken through an endoscope.

Multiplrex Holograms are printed by using a liquid-crystal television receiver as a spatial light modulator instead of silver-halide movie film. Reconstructed 3-D images of wire-frame model can be observed with high contrast. But, some noise which is caused by LCTV is also observed.

A holographic stereogram synthesized from a series of ordinary photographs is very convenient to make a hologram of an object whose hologram is very difficult or impossible to take in conventional techniques. The most popular one is a cylindrical holographic stereogram with white light reconstruction known as multiplex hologram. Reconstructed images from the multiplex hologram seem very attractive to display 3D images because they are very bright and of wide viewing angle to be observed by many people at the same time. This technique is capable of displaying medical X-ray images in 3D, and offers many advantages to medical doctors.

Color CCD endoscopes with sequential three color illuminations have the advantage of a high spatial resolution but are sensitive to object motion. A digital method for the restoration of color-shifted images is proposed.© (1987) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We propose to combine the properties of color image correlation with the flexibility of synthetic discriminant filters to generate filters capable of solving various color pattern recognition problems. We show that in addition to being color sensitive, the resulting complex composite filters yield an improvement in recognition accuracy with respect to conventional intensity filters.

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.

The introduction of information systems in the medical field has made it possible to accumulate a large amount of health care examination data. Analysis of such data could yield valuable new knowledge about health and disease. In this paper, we propose a method for the analysis of large amounts of medical and health care data, especially images or signals. The proposed method treats data in a multidimensional space without any pre-processing, and the data is classified into groups according to the criterion. The criterion used in this paper is to maximize likelihood calculated from the probability density, which is given by the Parzen estimation method. The result of classification is expressed by a binary tree structure as a hierarchy of clusters. We applied this method to computer-generated data and practical electrocardiogram data, and the results showed its validity.

Objective assessment of gastrointestinal mucosal color is extremely important in the endoscopic diagnosis of digestive tract disease. In this paper, we propose a method to clarify the spectral characteristics of gastric and colon cancer. A large number of spectral reflectance data of mucous membrane are measured by the endoscopic spectroscopy system (ESS) in the National Cancer Center Hospital East, Kashiwa, Japan and the Department of Internal Medicine, Self-Defense Force Center Hospital, Tokyo, Japan. We assume that early cancer appears primarily in the spectral data of short wavelength, because it is usually present in a superficial cell where short wavelength light is scattered more strongly than long wavelength light. To identify the features in the short wavelength components, the spectral reflectance was divided by the reflectance of a long wavelength. We investigated the possibility of distinguishing early cancer from normal spectral data through statistical analysis, employing the projection axis as the mean difference between them. Early cancer and normal spectral data were projected on the projection axis, and the Student’s T-test was applied to evaluate the mean of the distribution between these data.

The wavefront reconstruction of hologram and holographic stereogram are analyzed to compare their imaging properties, and 'phase added stereogram' (PAS) is proposed as a technique for the calculation of computer generated hologram (CGH). Applying PAS, computer graphics techniques, for example, surface shading and hidden surface removal are easily applied in CGH generation process. The amount of computation is reduced compared with actual hologram calculation, and the quality of reconstructed image is superior to that of holographic stereogram. The theoretical expression of PAS is presented, and experimental results are also demonstrated.

The next generation PET scanner named JPET-D4 has been developed at the National Institute of Radiological Sciences (NIRS) in Japan. The JPET-D4 has 4 layers DOI detectors and its data size becomes huge to handling. Then at first stage, we plan to apply the reconstruction techniques after the histogramming of list-mode data because it is easy to implement and effective to decrease computational cost The conventional histogramming technique is inapplicable to 4 layers DOI detectors, so we proposed the new histogramming method which is suitable for the multi-layer DOI detector. In this method, DOI-PET list-mode data is transformed into sinogram with an accurate system model of the crystal block. In this paper, we implemented this method with a full three dimensional system model. And we also applied the method to experimental data with prototype system for the JPET-D4 scanner. Experimental results show that the proposed method keeping the advantage of DOI information, and the image quality of the JPET-D4 is superior to a conventional NonDOI PET scanner.

In this paper we propose a method for unsupervised image segmentation, which is suitable for finding the features contained in medical images. The method is based on the hierarchical clustering method in multi-dimensional pattern vector space. We consider to change the size of pattern vectors adaptively to explore useful image features which can be used in medical diagnosis. We have tested our method on the simulation image, which is generated by the Markov Random Field (MRF) model, and the real medical images, photomicrographs of colon tumor, and its effectiveness is confirmed.

In order to reduce the risk of theft or leakage of personal information captured by biometric sensing, we have proposed novel biometric sensing techniques in which biometric image can be captured using optical encryption methods. These methods, called encrypted sensing, are based on double random phase encoding (DRPE) and compressed sensing (CS). Encrypted sensing based on DEPR is implemented through digital holography (DH). On the other hand, encrypted sensing system based on CS is composed of digital micromirror device for random intensity modulation and single pixel camera. Through experiments using fingerprint images and finger vein images, we confirm that biometric images can be obtained as they are encrypted, and they can be restored correctly from the encrypted images.

A new method to detect interval changes from a pair of images is presented, especially when the precise image registration is not available. We extend a well-known image histogram to multi-dimensions with some modifications and make use of it to elucidate differences between the images. The framework herein introduced is based on a comparison of the images in their multi-dimensional histogram space rather than in a spatial domain. Due to its flexibility, this approach is preferred as an alternative image comparison technique. The performance of the method is confirmed on simulated and real medical images and compared with the results from related conventional counterparts.

An electrical-optical hybrid processor for the high-speed calculation of surface images from three-dimensional voxel data is proposed. The image rotation and two-dimensional interpolation which requires enormous calculation time i n digital computers are optically realized by this processor. Hybrid three-dimensional simulator can produce not only the surface image lxt the semi-transparent image by using the graylevels ofthe original three-dimensional information. Experimental results are demonstrated. 1.

A digital diffuser designed for the efficient recording of Fourier holography is applied to the exposure of full-parallax holographic stereograms. From experimental results we confirm that the gray-level characteristic is greatly improved with the digital diffuser. High-resolution three-dimensional imagery is obtained with suppression of speckle noise. The limitation of the resolution is also described.

Temporal series of personal images may provide us valuable information regarding progression of a disease over time. A new method, which is based on a pattern histogram approach and time series analysis, is presented to detect long-term interval changes. Highly correlated and increasing pattern characteristics are considered as real interval changes, while background and noisy patterns exhibit more chaotic variations over time. The method has been tested on a sequence of chest radiographs using corresponding regions of interest, which include an increasing number of small opacities. The experimental results show that the method is promising and can be used in clinical applications over time. A key aspect of the proposed method is its independence of feature locations; therefore, it does not require any image registration technique to extract feature characteristics of the interval changes.

The single photon emission computed tomography (SPECT) imaging system has shift-variant characteristics due to non-uniform attenuation of gamma-ray, collimator design, scattered photons, etc. In order to provide quantitatively accurate SPECT images, these characteristics should be compensated in the reconstruction. This paper presents a new method to correct the shift-variant characteristics, which is based on a continuous-discrete mapping model and filtered backprojection (FBP) method, in which the projection data are assumed to be acquired by narrow ray sum beams in the FBP method and the assumed data set is expressed as a linear combination of the actual projection data. Narrow ray sum beams are approximated by a weighted sum of the original sensitivity functions. Thus, at the reconstruction the projection data are first modified using an approximation and the FBP method is then applied to the corrected projection data and a SPECT image is reconstructed. We further propose a technique that requires the inversion of smaller matrices than the conventional algebraic method; the amount of calculation and memory space become smaller and the stability of the calculation is greatly improved as well. The results of the numerical simulations are also demonstrated.

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.

Measurement of the rate constant parameters of the tracer /sup 18/F-FDG, used with positron emission tomography (PET) to determine the local cerebral metabolic rate of glucose (LCMRGlc), can provide a clear understanding of the physiological processes in the human brain. At present, the methods that are widely used to obtain LCMRGlc, such as nonlinear least squares (NLS), first require the reconstruction of a time sequence of images. The reconstruction of these images requires a large amount of computation, especially in 3D-PET, and the nonlinear based methods also require a large amount of computation. Here, the authors propose a fast parametric image reconstruction method for /sup 18/F-FDG dynamic PET studies. In their method a deconvolving process is first employed on the time sequential projection data to remove the effect of the measured plasma time activity. The deconvolved terms are integrated over three different time intervals and the parameters for determining LCMRGlc can be obtained analytically. The authors' method requires only three reconstructing processes and reduces the computational demand to estimate LCMRGlc. The algorithm performance is evaluated using a digital phantom and a clinical data set and the results show that the proposed method produces images with the same or better quality as the images form the NLS method, with much less computation compared to the NLS method.

The encryption method based on double random phase encoding makes it possible to use the fingerprints as cipher key. Applying this technique, we develop a file encryption software which can use fingerprint as cipher key.

Since the ways of symbolizing images are various, image retrieval methods need to use not only the keywords themselves, but also the related keywords. Because of the relevance among the keywords that can differ for each user, the retrieval method should take the individualities into account. In order to consider the individual differences, this paper proposes a new image retrieval method based on the probabilistic inference model. In the proposed method, the history of the retrieval process is used to estimate the degree of relevance among the keywords. Experimental results show the effectiveness of the proposed method. An opto-electronic implementation of the proposed retrieval system is also presented to realize a rapid retrieval.

An effective method for an automated detection of long-term interval changes from a sequence of time-varying medical images is presented. We combine the pattern histogram method with an autoregressive model and novel classification algorithm to distinguish real abnormality variations from chaotic behaviors of background patterns without using an image registration technique. We conducted an experiment using 16 personal chest radiographs of pneumoconiosis acquired at the time span of 33 years. It is confirmed that the proposed method is able to detect suspicious regions and it is advantageous to conventional image comparison techniques particularly when the precise image registration is not available prior to subtraction.

An advanced coded imaging system is described, and some results of phantom experiments are presented. The advanced method uses a pair of coherent codes (+ 1 and -1 codes) and has many advantages compared with conventional ones. One of the greatest advantages is that there are no sidelobes in the focal plane and only a few in other planes. Therefore, when an object can be regarded as two-dimensional, it is perfectly reconstructed with high detecting efficiency, and this is successfully simulated by a thyroid phantom with 99mTc. Moreover, this system has an ability to reconstruct tomograms, which is also shown by using ring phantoms piled on one another with some cold spots in their shells. From these experimental results it may be concluded that the new system is useful for practical applications, for example, to nuclear medicine.

Color CCD endoscopes with sequential three-color illuminations have the advantage of high spatial resolution but are sensitive to object motion. A digital method is proposed for the restoration of images color-shifted by the object motion. The method makes use of phase-only matching followed by a resampling operation to compensate for a space-variant shift between different primary color images. Restored images are suitable for further image processing such as color emphasis and structure enhancement.

Simulated annealing, a Monte Carlo-like algorithm, is applied to three-dimensional blood vessel reconstruction based on digital subtraction angiography. Since imaging systems often employ an insufficient number of projections, adequate reconstruction from observed data is not possible. It is shown that even in such cases objects can be sufficiently reconstructed by simulated annealing, which makes use of constraints based on a priori knowledge. This method is successfully demonstrated with a fundamental computer simulation.