• Proceedings of the KSME Conference
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• 2003.04a
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• pp.992-997
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• 2003

Aspherical lens design method named ray reverse tracing method is introduced. Differently from the traditional design method, the ray reverse tracing method traces the shape and location of a real object by use of its virtual image. From the result, it was convinced that spherical aberration free aspherical lens could be designed by use of the ray reverse tracing method. Furthermore, it could reduce the degree of dependence of optical characteristics on designer's ability, because deformation terms and optimization can be eliminated, which has been performed in conventional lens design process.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.191-198
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• 2003

In this study, aberration free aspherical lens design method named ray reverse tracing method is introduced. Differently from the traditional design method, the ray reverse tracing method traces the shape and location of a real object by use of its virtual image. From the result, especially spherical aberration free aspherical lens could be designed by use of the ray reverse tracing method. Furthermore, it could reduce the degree of dependence of optical characteristics on designer's ability, because deformation terms and optimization can be eliminated, which has been performed in conventional lens design process.

• Korean Journal of Optics and Photonics
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• v.26 no.6
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• pp.299-305
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• 2015

Using Snell's Law without approximation, we analyzed focal points for parallel rays incident upon the cornea of a human eye. To calculate a ray's incident angle versus incident height for focusing on the same point, we used the ray reverse tracing method. We derived the theoretical conditions for an aspherical lens to remove the spherical aberration caused by a human eye. In this research, we held the rear surface of the lens to be spherical, for simple calculation, and calculated the lens curvature of the front surface to design an aspherical surface.

• Korean Journal of Optics and Photonics
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• v.18 no.3
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• pp.179-184
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• 2007

In order to extract more accurate skin parameters, this study was focused on the improvement of the efficiency of a previous inverse fitting algorithm based on genetic algorithms. The algorithm provides the best fitting result of the diffusion approximation model to a VRS (visual reflectance spectroscopy) curve of skin. Simplex and wavelength selection methods were applied to the previous algorithm. Nine skin parameters were inversely extracted from the modeling studies. The revised inverse fitting algorithm was determined to produce an 83% reduction of computation time and a 0.64% reduction of sum of square error, compared to the previous algorithm. In conclusion, we confirmed that the new algorithm provides faster and more accurate solutions for the diffusion approximation model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.52-55
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• 2002

In this research, the modification method of spherical aberration, and aspherical lens shape design method were investigated. Spherical aberration affects lens's performance directly. Many studies have attempted to remove spherical aberration with a lot of methods in order to reduce the bad effect of spherical aberration. The approach to lens shape design was base on the ray tracing method. From the result, it was confirmed that ray reverse-tracing method was convenient to remove spherical aberration, and could be used very effectively and usefully for aberration-free aspherical lens design.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.5_6
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• pp.228-237
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• 2007

displacement mapping enables us to add realistic details to polygonal meshes without changing geometry. We present a real-time artifacts-free inverse displacement mapping method. In each pixel, we construct a ray and trace the ray through the displacement map to find an intersection. To skip empty regions safely, we traverse the image pyramid of displacement map in top-down order. Furthermore, when the displacement map is enlarged, intersection with bilinear interpolated displacement map can be found. When the displacement map is at distance, our method supports mipmap-like prefiltering to enhance image quality and speed. Experimental results show that our method can produce correct images even at grazing view angles. Rendering speed of a test scene is over hundreds of frames per second and the influence of resolution of displacement map to rendering speed is little. Our method is simple enough to be added to existing virtual reality systems easily.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.26-32
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• 2007

Design methods of LED optic system includes point source assumption and imaginary focus approaches. However, these methods make significant error if the position of LED approachs that of optic system. This paper suggests a new design approach that LED is equally divided, light distribution of each division is predicted and confirmed through reverse tracing of light wave, and then each divided segment is separately designed, Using new design method, two kinds of example optic system were designed and light distribution and efficiency of the systems were evaluated.

• The Journal of Natural Sciences
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• v.16 no.1
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• pp.31-37
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• 2005

We have developed an algorithm to determine the position from the image points in a lensmeter with 6-sided prism lens. The positions of the image points which are formed by six prisms depends on the decenter position of a test lens and can be calculated by skew ray tracing. The optical characteristics of the lens meter was analyzed using the Code V program and the positions of the image points was expressed as a function of the decenter position of the test lens. By minimizing the expectation error, we can determine the decenter position position of a test lens from the image positions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.179-187
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• 2010

The use of high frequency band, broad band and MIMO antenna is expected in the next generation mobile communication system. By the rapid increase of demand for wireless communications and the explosive increase of the mobile communication services, researches for optimization of next-generation mobile communication system are required. In the existing MIMO channel models, propagation-environments are commonly classified into urban, suburban, rural area, etc. However such approaches can have drawbacks in that many different morphologies may exist even in the urban area, for example. In this paper, we introduced path morphology concept, and proposed the method of morphology classification considering the building height, density, etc. Delay spread(DS), angular spread(AS) of AoD and AoA analyzed for each environment using the ray tracing technique. Based on the analysis, a MIMO channel model appropriate in domestic environment was suggested.