Biomedical subjects

Heejin Choi

Publications and source records attributed to Heejin Choi.

8 recordsLinked to original sources

PubMed2006

Convertible two-dimensional-three-dimensional display using an LED array based on modified integral imaging.

We propose a two-dimensional (2D) to three-dimensional (3D) convertible display technique using a light-emitting diode (LED) array based on the principle of modified integral imaging. This system can be electrically converted between 3D and 2D modes by using different combinations of LEDs in the LED array without any mechanical movement. The LED array, which is controlled electrically, is used for backlight, and a lens array is used for making a point light source array with higher density. We explain the principle of operation and present experimental results.

Journal Article↗

PubMed2006

Depth-enhanced three-dimensional integral imaging by use of multilayered display devices.

Integral imaging is one of the promising three-dimensional display techniques and has many advantages. However, one disadvantage of integral imaging is the limited image depth. The image can be displayed only around the central depth plane. We propose a depth-enhanced integral imaging using multilayered display devices. We locate transparent display devices that use liquid crystal in parallel to each other and incorporate them into an integral imaging system. As a result, the proposed method has multiple central depth planes and permits the limitation of expressible depth to be overcome. The principle of the proposed method is explained, and some experimental results are presented.

Journal Article↗

PubMed2006

Predominance of the group A killer Ig-like receptor haplotypes in Korean patients with T1D.

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease in which pancreatic beta cells are selectively destroyed. Although autoimmune diseases are driven by inappropriate adaptive immunity, innate immunity may play a role in the development of T1D. To study the potential involvement of innate immunity in the pathogenesis of autoimmune disease, we investigated associations of the genes for 14 different killer Ig-like receptors (KIRs), the well-characterized receptors in natural killer cells, with Korean T1D patients. Genetic association analyses revealed that some of the KIR genes were associated with T1D. KIR2DL5 and 2DS2 genes were present at significantly low frequency in Korean T1D patients (P < 10(-4)). We did not detect any influence of ligand distribution on KIR association. With the haplotype assignments, 53% of the KIR haplotypes in the control are of type A. Compared with the control (P < 10(-3)) and autoantibody-negative patients (P < 10(-2)), the group A haplotype predominates in Korean patients with T1D. The KIR gene is associated with T1D and distribution differences between T1D and controls were not influenced by the HLA genes (DR-DQ-A-C). T1D, at least in Koreans, is associated with KIR genes, especially in the group A KIR haplotypes. There is a close relationship between innate and adaptive immunity.

Adolescent↗

PubMed2005

Improved analysis on the viewing angle of integral imaging.

There have already been several analyses about the viewing angle of integral imaging (InIm). However, they can be applied only under the assumption that the original image is merely a single point source and are not suitable for application to an actual condition. We propose an improved analysis based on the actual InIm image, not on a single point source. It is possible to analyze and predict the viewing angle of an InIm system with good accuracy with the new analytic method because almost all the parameters of the InIm system such as the size and focal length of the lens array, image distance, the size and resolution of the image, and the location of the observers are included in this analysis.

Algorithms↗

PubMed2005

Wide-viewing-angle integral three-dimensional imaging system by curving a screen and a lens array.

A wide-viewing-angle integral three-dimensional imaging system made by curving a screen and a lens array is described. A flexible screen and a curved lens array are incorporated into an integral imaging system in place of a conventional flat display panel and a flat lens array. One can effectively eliminate flipped images by adopting barriers. As a result, the implemented system permits the limitation of viewing angle to be overcome and the viewing angle to be expanded remarkably. Using the proposed method, we were able to achieve a viewing angle of 33 degrees (one side) for real integral imaging and 40 degrees (one side) for virtual integral imaging, which is four times wider than that of the currently used conventional techniques. The principle of the implemented system is explained, and some experimental results are presented.

Journal Article↗

PubMed2004

Depth extraction by use of a rectangular lens array and one-dimensional elemental image modification.

Stereo matching, a technique for acquiring depth information from many planar images obtained by several cameras, was developed several decades ago. Recently a novel depth-extraction technique that uses a lens array instead of several cameras has attracted much attention because of the advantages offered by its compact system configuration. We present a novel depth-extraction method that uses a lens array consisting of vertically long rectangular lens elements. The proposed method rearranges the horizontal positions of the pixels from the collection of perspective images while it leaves the vertical positions of the pixels unchanged. To these rearranged images we apply a correlation-based multibaseline stereo algorithm in properly modified form. The main feature of the proposed method is the inverse dependency of the disparity in depth between horizontal and vertical directions. This inverse dependency permits the extraction of exact depth from extremely periodically patterned object scenes and reduces quantization error in the depth extraction.

Journal Article↗

PubMed2003

Wide-viewing integral three-dimensional imaging by use of orthogonal polarization switching.

A wide-viewing integral three-dimesional (3D) imaging system that adopts orthogonal polarization switching is proposed and demonstrated. In our scheme,the polarizing sheet attached to the lens array and the orthogonal polarization switching of the elemental image array perform elemental lens switching. The experimental results document that the viewing angle becomes remarkably wider than that of the conventional method. The distinguishing feature of our system is that it requires no mechanical moving part. In addition, because a commercially available polarization shutter screen is used for electrical switching, it is easy to implement this as a practical system. We believe that the proposed method facilitates the practical use of this wide-viewing integral 3D imaging system.

Journal Article↗

PubMed2002

Viewing-angle-enhanced integral imaging by elemental image resizing and elemental lens switching.

Integral imaging (II) is one of the promising techniques in the field of autostereoscopic three-dimensional display. Despite of its many advantages, the narrow viewing angle has been a drawback. We propose a technique that enhances the viewing angle of II by resizing the elemental images taken by the pickup process and switching the elemental lenses in the display process. We explain the principle of the proposed technique, analyze the effect on the resolution of the integrated image, and show the experimental results.

Journal Article↗