• Journal of the Korean Society for Precision Engineering
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• v.4 no.2
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• pp.36-46
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• 1987

An optical technique using laser for non-contact measurement of surface roughness and form accuracy of ground surfaces is presented. It is found that, when a ground surface is illuminated by a beam of laser light, the roughness height and slope distribution has significant influence on the pattern of reflection and it maintains an unique Gaussian distribution relationship with the surface roughness. The principle idea of the optical measurement system is therefore monitor the radiation, and then calibrate it in process against surface roughness by means of necessary digital data processing. On the other hand, measuring the form accuracy of a ground surface is accomplished by using a triangular method, which is based on observing the movement of an image of a spot of light projected onto the surface. The image is focused, through a series of lenses for magnification, on a photodetector array lf line configur- ation. Then the relative movement of image and consequently the form accuracy of the surface can be obtained through appropriate calibration procedures. Experimental test showed that the optical roughness measurement technique suggested in this work is very efficient for most industrial applications being capable of monitoring the roughness heights ranging 0.1 to 0.6 .$\mu$m CLA values. And form accuracy can be measured in process with a resolution of 10 .$\mu$m.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.373-380
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• 1993

A five mirror system with a reduction magnification(M=+1/5) is designed for DUV optical lithography. Initially, numerical solutions of all zero 3rd order aberrations and zero 5th order spherical aberration are obtained for the spherical mirror system. Next, by the optimization method, the aspherization is carried out to the two spherical mirrors to obtain a system that has as less residual aberrations, higher NA and improved MTF as possible. We have finally obtained the system of which NA is 0.45 and the resolution is about 500 cycles/mm at the 50% MTF value criterion and the depth of focus of $1.0{\mu}m$ for the nearly incoherent illumination$({\sigma}=1.0)$ and the wavelength of 0.248 m(KrF excimer laser line).

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.4
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• pp.39-44
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• 2009

Purpose: To design a mini optical system photographing the iris, which is used in the iridology. Methods: We designed a mini optical system photographing the iris by using the Sigma 2000 design program. Results: We designed a mini optical system photographing the iris, which is suitable in the CCD using a micro actuator for auto-focusing, of which characteristics have the TCL of 30 mm, a magnification of -0.65, about 8.0 mm distance from the 1st lens to the last lens, the max barrel diameter of 11 mm, and about 1 mm of the effective stop diameter. Also the resolution line width of this system is characterised by 92 lps/mm at the 30% MTF value criterion. Conclusions: By designing an optical system of which characteristics have the TCL of 30 mm, about 8.0 mm distance from the 1st lens to the last lens, the max barrel diameter of 11 mm, and the resolution line width of $5.4{\mu}m$ at the 30% MTF value criterion, we could miniaturize the iris photographing optical system.

• Korean Journal of Optics and Photonics
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• v.23 no.5
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• pp.189-196
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• 2012

A floating optical system is a system that moves more than 2 groups to focus at the camera lens. At the camera optics, the floating system that is mainly used is an optical system such as a macro lens which changes magnification very much. When the floating system is assembled and fabricated in the factory, there are differences between the image plane of the sensor and the focal plane of the infinity or macro state. Therefore, in a considerable proportion of cases, the focus adjustment to minimize the difference of BWD(Back Working Distance) is carried out in the process of manufacturing. In this paper, in order to decide the movement of each group in a floating system, we evaluated the rotation angle of CAM for the focus adjustment. We know that the maximum magnification of macro state is corrected by this numerical method for the focus adjustment, too. We investigated the limit of CAM rotation angle of the system by using statistical analysis for CAM rotation angle, which uses the focus adjustment of the floating system with symmetric error factors.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.356-363
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• 1994

By Gaussian optics, a zoom eyepiece is analyzed, which has the diameter of exit pupil 0.5 em, eyerelief 1 em, and angular magnification $M_a=7~15$. The initial design is based on this analysis. Telescope objective which was previously designed has focal length($(f_u')$ 21.0 em, and its clear aperture is 6.2 em. Zoom telescope has half field angle $\beta=1.5^{\circ}$ at the entrance pupil and at exit pupil it is $\beta'=1.5^{\circ}\times(7~15)=10.5^{\circ}~22.5^{\circ}$. Zoom eyepiece consists of three groups, of which each one satisfies the Seidel 3,d order aplanatization. Final design is obtained by optimization for the finite ray aberration, and the zoom eyepiece is assessed on the basis of the resolution of eyes.f eyes.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.388-394
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• 2014

In this paper, we propose a three-dimensional (3D) image correlator by use of computational integral imaging reconstruction based on the modified convolution property of periodic functions (CPPF) for recognition of partially occluded objects. In the proposed correlator, elemental images of the reference and target objects are picked up by a lenslet array, and subsequently are transformed to a sub-image array which contains different perspectives according to the viewing direction. The modified version of the CPPF is applied to the sub-images. This enables us to produce the plane sub-image arrays without the magnification and superimposition processes used in the conventional methods. With the modified CPPF and the sub-image arrays, we reconstruct the reference and target plane sub-image arrays according to the reconstruction plane. 3D object recognition is performed through cross-correlations between the reference and the target plane sub-image arrays. To show the feasibility of the proposed method, some preliminary experiments on the target objects are carried out and the results are presented. Experimental results reveal that the use of plane sub-image arrays enables us to improve the correlation performance, compared to the conventional method using the computational integral imaging reconstruction algorithm.

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.1-8
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• 1993

A design of four-mirror optical system with reduction magnification 5X for deep UV ($\lambda$=248 nm of KrF excimer laser) submicron lithography is presented. Initially by using the paraxial quantities, the domain of solution for $t=d_1+d_2+d_3$<0 (d;: distance between the mirror $c_i$ and $c_{i+1}$ is found for the system which is free from the four off-axial Seidel first order aberrations that are coma, astigmatism, field curvature, and distortion. The solution with $d_5$=2.95 (normalized with respect to $c_i$= -1) is choosen and the aspherization is carried out to the spherical mirror surfaces ($c_3$ and $c_4$ in order to reduce the axial and residual off-axial higher order aberrations. The numerical aperture of the final system is as large as 0.4, which gives Rayleigh resolution of 0.38 $\mu\textrm{m}$.

• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.141-146
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• 2000

Mie particles such as polystylene latex spheres with $3~5{\mu}m$ diameters are easily trapped and freely moved toward an arbitrary position by using the low power He-Ne laser beam focussed by the objective lens with the magnification of 40 X or 100 X. By using this technology, we can successfully arrange Mie particles in the form of the capital letter A. As a result, we can confirm the possibility of the optical tweezer that can readily trap and freely move the Mie particles. icles.

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.12-15
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• 1990

Holospeckle interferometry, the combined technique of holographic interferometry and speckle photography, was applied to the measurement of 3-D contact deformation created by an indentor. This new tech$.$ nique makes possible to measure both in-plane and out-of-plane displacements from one photographic plate. In this study, the optical system based on image holography was set up. In order to enhance the size and the contrast of the speckle, a proper magnification and a low reference beam ratio was used as compared with the conventional holographic interferometry technique. This system shows the magnified and clear holographic interference fringe as well as Young's fringe patterns.tterns.

• Current Optics and Photonics
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• v.6 no.6
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• pp.598-607
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• 2022

In this paper, a simple nondestructive technology is used to investigate unstained biological blood cells in three dimensions (3D). The technology employs a reflective phase-only spatial light modulator (SLM) for displaying the phase hologram of the object being tested, and a Fourier lens for its reconstruction. The phase hologram is generated via superposing a digital random phase on the 2D image of the object. The phase hologram is then displayed by the SLM with 256 grayscale levels, and reconstructed by a Fourier lens to present the object in 3D. Since noise is the main problem in this method, the windowed Fourier filtering (WFF) method is applied to suppress the noise of the reconstructed object. The quality of the reconstructed object is refined and the noise level suppressed by approximately 40%. The technique is applied to objects: the National Institute of Standards (NIS) logo, and a film of unstained peripheral blood. Experimental results show that the proposed technique can be used for rapid investigation of unstained biological blood cells in 3D for disease diagnosis. Moreover, it can be used for viewing unstained white blood cells, which is still challenging with an optical microscope, even at large magnification.