Biomedical subjects

Byoungho Lee

Publications and source records attributed to Byoungho Lee.

8 recordsLinked to original sources

PubMed2003

Electrically controllable in-line-type polarizer using polymer-dispersed liquid-crystal spliced optical fibers.

The polarization-dependent transmission of light through an electrically controllable in-line-type polarizer that is made from polymer-dispersed liquid-crystal spliced optical fibers is discussed experimentally and theoretically. This in-line-type optical splicing method has the advantage of low transmission loss when it is applied in optical fiber communication systems. An anomalous diffraction approach is used to compute the scattering cross section of polymer-dispersed liquid-crystal droplets. The experimental results are supported by a theoretical analysis. This device can be employed in electrically controllable in-line-type polarizers and has the potential to yield electrically controllable polarization-dependent loss compensators.

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PubMed2003

Enhanced three-dimensional integral imaging system by use of double display devices.

We propose an enhanced three-dimensional (3D) integral imaging system using multiple display devices. Experimental results with double devices prove the improvement in the image depth for a given image quality. We present experiments on an enhanced 3D integral imaging system using double display devices, in which two 3D subimages that cover different depth ranges are separately generated in each device, and then they are combined with a beam splitter to reconstruct the whole 3D image with an enhanced depth of view. In a similar manner, the double-device system can also be used to obtain a wider viewing angle by combining two images with different viewing angle ranges. We discuss the possibility of 3D integral imaging systems using multiple display devices as extensions of the system with double display devices.

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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.

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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.

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PubMed2002

Theoretical analysis for three-dimensional integral imaging systems with double devices.

By adoption of double-device systems, integral imaging can be enhanced in image depth, viewing angle, or image size. Theoretical analyses are done for the double-image-plane integral imaging systems. Both ray optics analysis and wave optics analysis confirm that the double-device integral imaging systems can pick up and display images at two separate image planes. The analysis results are also valuable in the understanding of the conventional integral imaging systems for image positions off the central depth plane.

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PubMed2002

Frequency-hopping optical orthogonal codes with arbitrary time-blank patterns.

We investigate a general scheme of frequency-hopping optical orthogonal codes with a specified distance between adjacent frequency symbols and propose a novel code that allows time blanks between adjacent frequency symbols in code sequences. A time blank represents the absence of frequency symbols in code sequences and makes no interference with frequency components. The insertion of time-blank patterns can provide ample scope to generate much more code sequences than the conventional codes lacking in time-blank patterns, and we show this by constructing an algorithm to generate the proposed code. The performance analysis demonstrates that its performance is superior to that of the conventional codes in terms of the bit error rate. We also derive the upper bound on the proposed code set.

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PubMed2002

Effect of a random pattern through a multimode-fiber bundle on angular and spatial selectivity in volume holograms: experiments and theory.

We demonstrate a multimode-fiber bundle reference scheme in a photorefractive volume hologram and discuss its angular/spatial selectivity both experimentally and theoretically. We measure the angular/spatial selectivity, changing distances between the photorefractive crystal and the output facet of the multimode-fiber bundle. The distance variation leads to a beam-size change in the reference beam, however, the object-beam size was fixed in all cases. The dependence of the angular/spatial selectivity for random-pattern (RP) referencing on a hologram dimension was examined and the characteristics compared with those derived from Gaussian referencing. Experimental results show that the RP referencing makes little contribution to the enhancement in angular selectivity, even though it leads to a considerable enhancement in spatial selectivity. The angular selectivity is mainly dependent on the dimension of a volume hologram, even with RP referencing. It is also noteworthy that the use of an RP beam can cause some high-frequency noise in the angular-multiplexing regime, which should be avoided in a hologram memory system. Nonetheless, the spatial selectivity of the RP referencing shows nearly no dependence on hologram dimension, and is mainly dependent on the transversal speckle size of the random-pattern beam. These characteristics can also be verified by the numerical results presented here, which are in good agreement with the experimental results.

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PubMed2002

Characteristics of short-period blazed fiber Bragg gratings for use as macro-bending sensors.

The characteristics of short-period blazed fiber Bragg gratings for use as macro-bending sensors are discussed. This sensor is able to detect macro bending with the transmitted power variation of the first side mode in the blazed fiber Bragg grating. Since an incident ray experiences different variations of tilt angles with respect to bending direction, the blazed fiber Bragg grating has different coupling efficiencies of the first side mode, which can be reduced considerably in the case of twisted blazed fiber Bragg gratings.

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