• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.121-129
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• 2014

This study was carried out to develop an efficient plant growth system that can be controlled by altering the wavelength and illumination using a LED module. If it is possible to develop a system that can be controlled in this manner, utilizing different characteristics in the meaningful wavelength band depending on the growth time or type of plant, the plant growth conditions can be optimized. In order to this, red, green, blue and white LEDs are arrayed in a rectangle, consisting of LED modules which can be combined with each other. Consequently, the array can be used to select the optimal light conditions with monochromatic red, green, blue and white LEDs, or mixed LEDs, for plant growth. Experiments on the characteristics of the wavelengths to evaluate the efficiency of the plant growth system were performed. The usefulness of the system was demonstrated through a cultivation test involving several special plants.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.216-219
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• 2005

In precision length measurements using optical interferometry based on homodyne or heterodyne principles, it is crucial to have frequency-stabilized monochromatic light sources. To the end, we investigate the possibility of utilizing the optical comb constituted by ultrashort femtosecond pulse lasers generated from a gain medium of titanium-doped aluminium oxide $(Ti:Al_2O_3)$. The optical comb is stabilized by locking to the caesium atomic clock, which allows all the modes of the comb to maintain an extremely high level of frequency stabilization to precision of one part in $10^{16}$. Then, high precision length measurements are realized by extracting a single or group of particularly wanted optical frequency components or by adopting a third-party light source locked to the comb. Required measurement system setup will be presented in detail along with experimental results.

• Korean Journal of Optics and Photonics
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• v.9 no.1
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• pp.5-8
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• 1998

In calculating the light propagation in inhomogeneous uniaxial materials by using a conventional $4{\times}4$ matrix method, Fabry-Perot effect is caused by inherent multiple internal reflections at interfaces for monochromatic light source. In this paper we propose an apodization method by which we can eliminate in negligible time the interference fringe in the $4{\times}4$ matrix optics. For a cell with k abrupt interfaces, the new apodization method can be implemented simply by, at maximum, (k+1) addtional $4{\times}4$ matrix multiplications in calculating the complete transfer matrix of the cell.

• Current Optics and Photonics
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• v.6 no.1
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• pp.44-50
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• 2022

An off-axis zone plate is able to focus on a single order while neglecting the zeroth order in a visible imaging system. This allows one to enhance the contrast quality in diffractive images, which is the major advantage of this type of zone plate. However, most previous reflection zone plates are used in focusing X-rays with a small grazing incident angle and are intricately designed with the use of a local grating period. In this study, we suggest the design of an off-axis elliptical zone plate (EZP) that is used to focus a monochromatic light beam with separation between the first and unfocused orders under a large grazing incident angle of 45°. An assumption using the total grating period, which depends on the average and constant grating period, is proposed to calculate the desired distance between the first and zeroth order and to simplify the construction of a novel model off-center EZP. Four diffractive optical elements (DOEs) with different parameters were subsequently fabricated by direct laser lithography and then verified using a performance evaluation system to compare the results from the assumption with the experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.569-572
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• 2005

Technological feasibility of using recently-available femtosecond ultra short pulse lasers for advanced precision length metrology is investigated with emphasis on absolute distance measurements with $10{\mu}m$ ??resolution over extensive ranges. The idea of using femtosecond lasers for the measurement of absolute distances is based on the fact that a short pulse train is a mode-locked combination of discrete monochromatic light components spanning a wide spectral bandwidth. The synthetic wavelength is created from the repetition frequency, $f_r$ of the femtosecond laser and for more precise resolution, higher-order harmonics of the repetition frequency may be selected as the synthetic wavelength by using appropriate electronic filters.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.281-284
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• 1995

A molecular photodiode was fabricated with hetero-Langmuir-Blodgett (LB) film consisting of an electron accepter(A) and sensitizer. N-Allyl-N-[3-propylamido-N\",N\"-야(n-octadecyl)]-4,4-bipyridum Dibromide and 7,8-dimethyl-10-dodecyl isoalloxan-zine were used as A and S units, respectively. By aligning hefter-LB film of A/S units on ITO glass with an aluminium thin film, a molecular photodiode with the structure of Metal/Insulator/Metal(MIM) was constructed. Due to excitation by irradiation with a 460nm monochromatic light source, the photo-induced unidirectional flow of electrons in the MIM device could be achieved and was detected as photocurrents. The direction of energy flow was in accordance with the energy level profile across the LB films. The photo switching function was achieved and the rectifying characteristics was obserbed in the molecular devise.

• Journal of the Korean Chemical Society
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• v.22 no.6
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• pp.417-422
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• 1978

Rather than undergo photooxygenation, the Z-configuration benzalpyrrolinones (Z-2, Z-4) photoisomerized to the E-configuration isomers under direct or sensitized irradiation. Rose bengal sensitized photochemical stereoisomerzation of benzalpyrrolinones (Z-2, Z-4 and E-2) with monochromatic light (at 557 nm, excitation of rose bengal only) showed that the triplet of benzalpyrrolinones was involved in the photoisomerization, since oxygen inhibited the photoisomerization.

• Journal of Engineering Education Research
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• v.16 no.2
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• pp.24-30
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• 2013

This paper deals with the measurement theory and technique of linear expansion coefficient for solid material using Michelson interferometer. The Michelson interferometer produces interference fringes by splitting a beam of monochromatic light so that one beam strikes a fixed mirror and the other a movable mirror. When the reflected beams are brought back together, an interference pattern results. Precise distance measurements until a quarter of wave length can be made with the Michelson interferometer by moving the mirror and counting the interference fringes which move by a photo diode. This paper represents the application of Michelson interferometer for measuring infinitesimal length system and shows the measurement method of linear expansion coefficients for various materials like copper, aluminum and iron. the results are good agreement with theoretical value within margin of error for each materials.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.67-68
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• 2007

The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards specialty and general illumination applications. Because drive circuit of illumination LED has an effect on efficiency and life, research about the drive circuit following LED characteristic is needed. This paper proposed a implementation of the stand-alone LED lighting system using battery from photovoltaic power generation.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.157-161
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• 1996

A simple laser Doppler velocimeter(LDV) using a $CO_2$ laser with its self-mixing effect has been developed. We measured the laser power which was modulated by Doppler frequency, when monochromatic laser light was focused to a moving target. The Doppler-shifted frequency was controlled by changing rotating speed of the turntable or the cosine of the angle between the direction of the laser beam and that of the rotating velocity.