Shin-Hwan Kim

Image-Forming Principle of Integral Photography

In this paper, viewing zone-forming geometry of multiview imaging systems and lens image forming principle is applied to prove that the depth sensing mechanism of integral photography (IP) is both parallaxes. The proof is based on the fact that making the cell size of each elemental image the same as a microlens pitch does not change the geometry, because there are no changes in the field-of-view of each microlens. The total number of different view images perceived in the viewing zone of IP, and the compositions of the images and condition of increasing the number are also identified.

Automatic image segmentation for concealed object detection using the expectation-maximization algorithm

We address an image segmentation method to detect concealed objects captured by passive millimeter wave (MMW) imaging. Passive MMW imaging can create interpretable imagery on the objects concealed under clothing, which gives the great advantage to the security system. In this paper, we propose the multi-level expectation maximization (EM) method to separate the concealed objects from the other area in the image. We apply the EM method to obtain a Gaussian mixture model (GMM) of the acquired image. In the experiments, we evaluate the performance by the average probability of error. We will show that the consecutive EM processes separates the object area more accurately than the conventional EM method.

Pulsed laser holographic video

The use of a pulse laser as the source light for a holographic video system allows to eliminate the polygon mirror or scanners in the system. At the same time, a single long aperture AOM is replaced by 6 small aperture AOMs aligned in a line. The effective aperture length of the 6 AOM combination is 6 times of that of the individual AOM. the CGH data is divided in 6 equal part s and fed into the corresponding AOM simultaneously. This new AOM structure permits to use a personal computer for data feeding.

Three-dimensional imaging system based on a light-emitting diode array

A two-dimensional light-emitting diode array is used to replace the viewing-zone-forming optics in-multiview full-parallax three-dimensional image display systems. Since the array is not working merely as the viewing-zone-forming optics but also as the backlight panel for the liquid-crystal display (LCD) panel, it allows constructing three-dimensional imaging systems having the same structure as the current LCD display. The designed system displays images with good depth sense.

Image Registration and Fusion between Passive Millimeter Wave Images and Visual Images

Passive millimeter wave imaging has the capability of detecting concealed objects under clothing. Also, passive millimeter imaging can obtain interpretable images under low visibility conditions like rain, fog, smoke, and dust. However, the image quality is often degraded due to low spatial resolution, low signal level, and low temperature resolution. This paper addresses image registration and fusion between passive millimeter images and visual images. The goal of this study is to combine and visualize two different types of information together: human subjects identity and concealed objects. The image registration process is composed of body boundary detection and an affine transform maximizing cross-correlation coefficients of two edge images. The image fusion process comprises three stages: discrete wavelet transform for image decomposition, a fusion rule for merging the coefficients, and the inverse transform for image synthesis. In the experiments, various types of metallic and non-metallic objects such as a knife, gel or liquid type beauty aids and a phone are detected by passive millimeter wave imaging. The registration and fusion process can visualize the meaningful information from two different types of sensors.

Concealed object detection using passive millimeter wave imaging

This paper addresses concealed object detection by passive millimeter wave (MMW) imaging. Passive MMW imaging penetrates into clothing to capture metal and man-made objects. In this paper, we propose a multi-level expectation maximization (EM) method to separate the concealed object from the body area. The performance is evaluated by the average probability of error. We will show that the proposed EM processes segments the object area more accurately than the conventional EM method.

Three-Dimensional Object Reconstruction and Recognition Using Computational Integral Imaging and Statistical Pattern Analysis

In this paper, we discuss computational reconstruction and statistical pattern classification using integral imaging. Three-dimensional object information is numerically reconstructed at arbitrary depth-levels by averaging the corresponding pixels. The longitudinal distance and object boundary are estimated where the standard deviation of the intensity is minimized. Fisher linear discriminant analysis combined with principal component analysis is adopted for the classification of out-of-plane rotated objects. The Fisher linear discriminant analysis maximizes the class-discrimination while the principal component analysis minimizes the error between the original and the restored images. The presented method provides promising results for the distortion-tolerant pattern classification.

Image fusion of visual and millimeter wave images for concealed object detection

This paper addresses passive millimeter wave imaging (PMMW) and image fusion for concealed object detection. The PMMW imaging system forms images by means of passive detection of millimeter wave radiation. The PMMW imaging has the capability of detecting concealed metal and dielectric objects under clothing. An image fusion method is developed using the discrete wavelet transform (DWT) and a fusion rule. We adopt the symlets (symmetrical wavelets) for the multi-resolution analysis (MRA). The minimum scheme is applied to the approximation and the weighted-average scheme to the detail coefficients. The experimental and simulation results show the presented technique can detect the concealed object and fuse it with a visual image.

Stereo images in millimeter-wave regime

A focal plane detector array in a millimeter wave imaging system can be used to acquire multiview images in millimeter wave band. Two focal plane detectors which are distanced 8mm are used to obtain a stereoscopic image pair of a scene. The pair reveals a good depth sense though its resolution is very low and enables to estimate distances of objects in the scene with a reasonable accuracy. Keywords: millimeter wave imaging system, parabolic antenna, stereoscopic image pair, focal plane detector array, depth sense, object distance.

Viewing Zones in PLS Based Multiview 3-D Imaging Systems

In 3D imaging systems, with a point light source (PLC) array as a backlight illumination and viewing zone forming, the finite size of the light-emitting surface of each PLC in the array and mismatch between the array period and pixel cell pitch limits the region of individual view image to a small portion of the viewing zone cross section (VZCS). The portion becomes smaller as the size approaches that of a pixel for an individual view image in the pixel cell, and/or the fractional size of the pixel becomes smaller. As a consequence, the VZCS becomes filled with viewing regions for mixed images of two adjacent view images. Hence, the effective number of different images which can be viewed at VZCS could be increased around two times that of the total different view images displayed on the display panel.