Hyug-Gyo Rhee

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The autofocusing is one of the important parts in the automated vision inspection or measurement using optical microscopes. Moreover, laser micromachining or laser lithography requires a high speed and precision autofocusing. In this paper, we propose and realize an autofocusing system using two cylindrical lenses, which is the enhanced version of the(More)
Freeform optics have emerged as promising components in diverse applications due to the potential for superior optical performance. There are many research fields in the area ranging from fabrication to measurement, with metrology being one of the most challenging tasks. In this paper, we describe a new variant of lateral shearing interferometer with a(More)
We present a point-diffraction interferometer that has been specially devised to perform absolute distance measurements in three dimensions. It is composed of two main parts: One is a target that moves in three dimensions, and the other is a stationary two-dimensional array of photodetectors. The target is made of point-diffraction sources that emit two(More)
We present experimental results on the output power stabilization of an Ar(+) laser for a direct laser writing system (LWS). Instability of the laser output power in the LWS cause resolution fluctuations of being fabricated diffractive optical elements or computer-generated holograms. For the purpose of reducing the power fluctuations, we have constituted a(More)
We propose a new method based on direct laser lithography to fabricate reference chromium patterns on a silicon wafer. Our method is able to fabricate a maximum 360-mm-diameter pattern with 651-nm-position uncertainty. The minimum pattern size is about 0.8 microm (linewidth value) and the maximum available height of the pattern is slightly over 400 nm.
We report a new dual band compact oblique photography camera (LC11) that is the first to benefit from the incorporation of telecentricity. LC11 has a common front end F/6.6 telescope with 280 mm in aperture that forms its electro-optical (EO, F/7.5) and MWIR (F/5.6) modules. The design allows a substantial reduction in volume and weight due to i) the(More)
A lateral shearing interferometer has an advantage over previous wavefront measuring interferometers since it requires no reference. Therefore the lateral shearing interferometer can be a powerful solution to measure a freeform surface. It, however, has some issues to be resolved before it can be implemented. One of them is the orthogonality problem between(More)
We propose a new laser lithographic technique with enhanced resolution. A calcite wave plate is introduced in our system to separate an input lithographic beam into two orthogonally polarized beams. After going through an imaging lens, these two beams meet again on the focal point, and generate a small interferogram that sharpens the shape of the focused(More)
We describe a method of absolute xyz-coordinates measurement based on the two-point diffraction interferometer. In this paper we use a new optimization algorithm to the interferometer. Experimental results show that the systematic error of the interferometer is less than 1 mum (peak-to- valley value) within a 60 mm by 60 mm by 20 mm working volume. To(More)
Discrepancies between phase-shifting and white-light interferometry have been observed in step-height and surface roughness measurements. The discrepancies have a strong relation to the roughness average parameter of the surface. The skewing effect, which mainly occurs in the vicinity of peaks, valleys, and edges of the sample, causes this problem in(More)