• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.451-455
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• 2009

We present a numerical procedure that compensates for tilt phase aberration in in-line digital holography by computing the period of interference patterns in the reconstructed phase image. This method enables the reconstruction of correct and accurate phase information, even if strong tilt aberrations exist. Example applications of tilt aberration compensation are shown for a tilted plate, a micro-lens array, and a thin film transistor. This method is convenient because it uses only one hologram and no hardware to minimize the tilt aberration.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.399-400
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• 1996

LAMOST is a special reflecting Schmidt telescope. Both the refleting Schmidt plate $M_A$ and the spherical primary mitrror $M_B$ are segmened mirrors. These two cofocus but not co-phase. The diffraction of the optical system is decided by the shape overlapping of $M_A$ and $M_B$. This paper describes the diffraction caculating results with different declination and different field angle. The diffraction influence to the image quality is acceptable in the error buget of optical system. It also proves that the size seletion of the sub-mirror is reasonable.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.349-355
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• 1994

Superrsolution of an optical imaging system, which resolves $\epsilon_O$ (half width of the square top amplitude impulse function) less than the Rayleigh's resolution limit $\epsilon_R$, is theoretically treated by using the diffraction theory, and an experimental system is proposed. Initially superresolution is stated as an inverse problem, and an integral equation is derived as a function of parameter $\beta$, which is positive. The integration is numerically carried out for the given aperture and those given values of $\beta$, which is 1, 5, 10, 15, and 20. 1/2$\times$FWHM's of the amplitude impulse functions are meassured for the cases of diffrent value of {J and in the case of $\beta=5$, the half-width already approaches to $\epsilon_O=0.1$,urn, which is, in the case of the present work, one fifth of the Rayleigh's resolution limit. It is found both the pupil function and the phase of the Huygens wave are to be modified, and theories of the pupil function modulation plate and the phase modulation hologram plate are also presented. The result obtained may be useful in ultrafine optical lithography.graphy.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.38-44
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• 2000

In this paper, we have been fabricated λ/2 phase plates lot an optical pick-up using a blue violet laser diode by employing proton exchange and wet etching in LiNbO$_{3}$. Their functions and fabrication processes are described in detail. It is established the optimal fabrication conditions through the experimental results. The device characteristics are measured by the Mach-zender interferometer which is composed of the optical components and 632.8nm He-Ne laser. The measured phase error was ＋5$^{\circ}$~ -6$^{\circ}$(within 3%). This phase plate could be applied an useful device to improve the resolution and the stability of the optical pick-up which has a blue violet laser diode as an optical source.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.132-141
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• 1996

The pixelated phase grating has been studied as a kind of diffraction gratings splitting and input beam into multiple spots. It consists of regular size cells which produce phase delays, and each cell provokes the phase delay up to sixteen levels. We have compared and analyzed the characteristics of multi-level phase gratings, laying streess on efficiency and resulted pattern. Experimental resutls obtained form fabricated grating have been presented, and the real-time method using a liquid-crystal spatial light modulator has been demonstrated through experiments. Gratings making meams with specific intensities have been designed and optical images have been generated by them. In order to specific intensities have been designed and optical images have been genrated by them. In order to decide the phase delay of each cell, optimization conditon consists of diffraction efficiency and target values. One period of phase gratings fabricated with surface relief was less than 256${\mu}m{\times}256{\mu}m$ and size of each cell was 1${\mu}m{\times}1{\mu}m$ surface relief grating has been made by coating photoresist on the glass plate, writing information pattern by Ar laser and developing it. in the experiment for real-tiem processing liquid-crystal display of epson video projector has been used.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.1
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• pp.1-7
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• 2022

In this study, dissolution and melting phenomenon of the Al₂Cu was studied for the high-strength Al-Si-Cu aluminum alloy in automobile component. The Solution heat treatment was performed at 480℃ and 510℃ for 4hours. Microstructure analysis of the specimen was performed using the optical micrograph and scanning electron microscope for qualitative and quantitative analysis of various phases, the chemical composition of secondary phases was achieved by energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). As a result of the electron probe micro analysis, a plate like Al₂Cu phase was observed, and eutectic Si phase was observed of a coarsen plate shape. At a temperature of 510, necking phenomenon occurs in a specific part of plate like Al₂Cu, and it is segmented and dissolved in the Al matrix. When the temperature of the alloy exceeds the melting point of Al₂Cu, incipient melting occurs at the grain boundary of undissolved Cu particles

• Current Optics and Photonics
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• v.1 no.2
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• pp.107-112
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• 2017

An adaptive optics system can be simulated or analyzed to predict its closed-loop performance. However, this type of prediction based on various assumptions can occasionally produce outcomes which are far from actual experience. Thus, every adaptive optics system is desired to be tested in a closed loop on an optical test bench before its application to a telescope. In the close-loop test bench, we need an atmospheric simulator that simulates atmospheric disturbances, mostly in phase, in terms of spatial and temporal behavior. We report the development of an atmospheric turbulence simulator consisting of two point sources, a commercially available deformable mirror with a $12{\times}12$ actuator array, and two random phase plates. The simulator generates an atmospherically distorted single or binary star with varying stellar magnitudes and angular separations. We conduct a simulation of a binary star by optically combining two point sources mounted on independent precision stages. The light intensity of each source (an LED with a pin hole) is adjustable to the corresponding stellar magnitude, while its angular separation is precisely adjusted by moving the corresponding stage. First, the atmospheric phase disturbance at a single instance, i.e., a phase screen, is generated via a computer simulation based on the thin-layer Kolmogorov atmospheric model and its temporal evolution is predicted based on the frozen flow hypothesis. The deformable mirror is then continuously best-fitted to the time-sequenced phase screens based on the least square method. Similarly, we also implement another simulation by rotating two random phase plates which were manufactured to have atmospheric-disturbance-like residual aberrations. This later method is limited in its ability to simulate atmospheric disturbances, but it is easy and inexpensive to implement. With these two methods, individually or in unison, we can simulate typical atmospheric disturbances observed at the Bohyun Observatory in South Korea, which corresponds to an area from 7 to 15 cm with regard to the Fried parameter at a telescope pupil plane of 500 nm.

• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.87-91
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• 2003

In this paper, a rotation invariant fingerprint identification system is implemented using the circular harmonic filter and phase only correlator. We extracted the phase component from input fingerprint image and correlate it with the circular harmonic filter of the reference fingerprint image by POC. The input image is obtained using a prism operating in the internal full reflection mode. Then the input image is transformed to two dimensional Fourier spectrum in optical way and the phase component is extracted using a digital system from the spectrum. Because composed of the optical system and digital algorithm, the proposed system has the advantages of the two technologies such as realtime parallel processing property of the optics and the flexibility of the digital system.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.52.2-52.2
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• 2010

107P/(4015) Wilson-Harrington is one of possible candidates of the dormant or inactive comet nuclei. It was discovered on a photographic plate exposed with the 48-inch Schmidt at Palomar Observatory on 1949 November 19 UT, displaying the faint extended cometary tail. No comet activity has not been after 1949 apparition. Here we present the optical observations of 107P/(4015) Wilson - Harrington during 2009/2010 apparition taken in search of low-level comet activity. Our photometric and spectroscopic data were collected 28 - 86 days after the perihelion passage on 2009 October 22 in a wide range of solar phase angle of 39-68 degree. A disk-integrated phase function was constructed, giving a geometric albedo of 0.055+/-0.012, phase integral of q=0.34, and Bond albedo of A_B=0.019. The photometric property shows profile similar to low albedo asteroids and comet nuclei. Any emission lines were found in our spectrum, giving a flat reflectance similar to low albedo asteroids. Although we could not find any evidence for the comet activity in our photometric and spectroscopic data, we found an upper limit of the fractional active area of 0.001%. We derived the upper limit of the optical depth of the dust trail and tail 7x10^{-10}. We conclude that 107P/(4015)Wilson-Harrington became completely dormant or inactive in 2009/2010 return.

• Korean Journal of Optics and Photonics
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• v.25 no.1
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• pp.29-37
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• 2014

We have studied and demonstrated general, systematic error-correction methods for a dual rotating quarter-wave plate ellipsometer. To estimate and correct 5 systematic error sources (three offset angles and two unexpected retarder phase delays), we used 11 of the 25 Fourier components of the ellipsometry signal obtained in the absence of an optical sample. Using these 11 Fourier components, we can determine the errors from the 5 sources with nonlinear optimization methods. We found systematic errors ${\epsilon}_3$, ${\epsilon}_4$, ${\epsilon}_5$) are more sensitive to the inverted Mueller matrix than retarder phase delay errors (${\epsilon}_1$, ${\epsilon}_2$) because of their small condition numbers. To correct these systematic errors we have found that error of any variety must be less than 0.05 rad. Finally, we can use the magnitudes of these errors to correct the Mueller matrix of optical components. From our experimental ellipsometry signals, we can measure phase delay and the rotational angular position of its fast axis for a half-wave plate.