• 제어로봇시스템학회논문지
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• 제9권7호
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• pp.507-514
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• 2003

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. Recently the shape measurement using interferometric principle is found to be a successful methodology among other visual or optical technologies. Especially, the measuring method using wavelength scanning interferometer(WSI) has a great advantage in comparison with other conventional jnterferometric methods in that the absolute distance from the reference surface can be directly obtained from the amount of jnterferometric phase change. However, the measurement methods using WSI proposed by other researchers have low measurement resolution so far because they can't measure fractional phase change. To avoid this shortcoming we propose a new algorithm in this paper, which can obtain a small amount of even fractional phase change by sinusoidal function fitting. To evaluate the effectiveness of the proposed sinusoidal function fitting algorithm, a series of measuring experiments are conducted for discontinuously shaped specimens which have various height. The proposed algorithm shows much more enhanced measurement resolution than other existing conventional algorithms such as zero crossing algorithm and Fourier transform algorithm.

• Bulletin of the Korean Chemical Society
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• 제28권11호
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• pp.2083-2088
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• 2007

Biosensor based on rugate PSi interferometer for the detection of avidin has been described. Rugate PSi fabricated by applying a computer-generated pseudo-sinusoidal current waveform has been prepared for the application as a label-free biosensor based on porous silicon interferometer. The fabrication, optical characterization, and surface derivatization of a rugate PSi has been described. The method to fabricate biotinderivatized rugate PSi has been investigated. The surface and cross sectional morphology of rugate PSi are obtained with SEM. FT-IR spectroscopy is used to characterize the oxidation and functionalization reaction of rugate PSi sample. Binding of the avidin into the biotin-derivatized rugate PSi induces a change in refractive index. A red-shift of reflectivity by 18 nm in the reflectivity spectrum is observed, when the biotin-modified rugate PSi was exposed to a flow of avidin.

• 한국광학회지
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• 제14권2호
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• pp.116-121
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• 2003

매개하향변환과정에서 발생한 광자쌍과 Hong-Ou-Mandel 간섭계를 이용한 4차 간섭실험에서 비고전적인 간섭효과를 관측하였다. 편광방향이 서로 수직인 두 광의 4차 간섭에서 간섭무늬의 선명도가 고전적인 한계인 50%를 넘는 최대 85%의 간섭무늬를 관측하였다. 또한 두 빔의 세기 비율이 증가할수록 간섭무늬의 선명도가 감소하는 고전적인 간섭현상과 달리 두 광의 세기 비율이 1:10인 경우에도 83%의 선명도를 갖는 간섭효과를 측정하였다.

• 조명전기설비학회논문지
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• 제29권8호
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• pp.76-82
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• 2015

A hybrid fiber-optic sensor system which combines fiber Bragg grating sensors and a Michelson interferometer has been constructed and evaluated for condition monitoring of large scale wind turbines. In order to measure multiple stresses applied to wind turbines such as strain, temperature and vibration, the system uses single broadband light source. It addresses both types of sensors, which simplifies the optical setup and enhances the cost-effectiveness of condition monitoring system. An athermal-packaged FBG is used to supply quasi-coherent light, of which coherence length is about 3.28mm, for the Michelson interferometer demodulation. Experimental results demonstrated that the proposed fiber-optic sensor system was capable of measuring strain and temperature with measurement accuracy of 1pm. Also 500~2000Hz vibration signals were successfully analyzed by applying FFT signal processing to interference signals.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.78-87
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• 2016

Red blood cells (RBCs) are customarily adhered to a bio-functionalised substrate to make them stationary in interferometric phase-imaging modalities. This can make them susceptible to receive alterations in innate morphology due to their own weight. Optical tweezers (OTs) often driven by Gaussian profile of a laser beam is an alternative modality to overcome contact-induced perturbation but at the same time a steeply focused laser beam might cause photo-damage. In order to address both the photo-damage and substrate adherence induced perturbations, we were motivated to stabilize the RBC in OTs by utilizing a laser beam of ‘arbitrary intensity profile’ generated by a source having cavity imperfections per se. Thus the immobilized RBC was investigated for phase-imaging with sinusoidal interferograms generated by a compact and robust Michelson interferometer which was designed from a cubic beam splitter having one surface coated with reflective material and another adjacent coplanar surface aligned against a mirror. Reflected interferograms from bilayers membrane of a trapped RBC were recorded and analyzed. Our phase-imaging set-up is limited to work in reflection configuration only because of the availability of an upright microscope. Due to RBC’s membrane being poorly reflective for visible wavelengths, quantitative information in the signal is weak and therefore, the quality of experimental results is limited in comparison to results obtained in transmission mode by various holographic techniques reported elsewhere.

• 전자공학회논문지
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• 제49권10호
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• pp.128-134
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• 2012

전계 측정시스템에서 센서 감지부로 $1.3{\mu}m$ 파장대역에서 동작하는 비대칭 구조의 집적광학 Mach-Zehnder 광변조기를 구현하였다. BPM 전산모사를 통해서 소자의 동작 특성을 검증하였고, $LiNbO_3$에 Ti 확산방법으로 구현된 채널 광도파로에 평판형 안테나가 부착된 집중 전극구조 배열하여 전계 센서를 제작하였다. 500 KHz, 5 MHz 각각의 주파수에서 측정 가능한 최소 전계는 1.02 V/m, 6.91 V/m로 평가 되었으며, 이에 대응되는 각 주파수에서 ~35 dB, ~10 dB의 다이나믹 범위가 측정되었다.

• 정보통신설비학회논문지
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• 제3권2호
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• pp.51-60
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• 2004

A광섬유 용융인장방법에 의해서 100GHz 채널간격을 갖는 DWDM용 8채널 광다중화기를 제작하였다. 8채널 광다중화기는 전광섬유형 Mach Zehnder 간섭계(MZI)를 3단으로 다단 연결하여 제작되었으며, 광다중화기 채널별 출력파장의 삽입손실을 균일하게 하기 위하여 파장에 대한 삽입손실변화가 적은 파장무의존형 커플러(WFC)를 이용하여 전광섬유형 MZI를 제작하였다. 광다중화기를 구성하는 광섬유형 MZI를 제작함에 있어서 경로차에 따른 출력 파장간격의 변화를 시뮬레이션을 통하여 알아보았고 다단연결에 의한 광다중화기 구현방법을 논의하였다. 전용 제작 장치를 이용하여, 전광섬유형 MZI를 제작하였으며, 미세한 파장을 저절하기 위해서, $CO_2$ 레이저를 이용하였다. 제작된 8채널 광다중화기는 평균 삽입 손실 2.1dB, 5.5dB에서의 통과대역폭이 0.8nm 이며, 25dB의 채널 Crosstalk를 갖는 특성을 얻을 수 있었고, 편광의존손실은 0.06dB 였다.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.592-603
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• 2015

In this paper, an optical implementation of a novel asymmetrical cryptosystem combined with D-H secret key sharing and triple DES is proposed. The proposed optical cryptosystem is realized by performing free-space interconnected optical logic operations such as AND, OR and XOR which are implemented in Mach-Zehnder type interferometer architecture. The advantage of the proposed optical architecture provides dual outputs simultaneously, and the encryption optical setup can be used as decryption optical setup only by changing the inputs of SLMs. The proposed cryptosystem can provide higher security strength than the conventional electronic algorithm, because the proposed method uses 2-D array data, which can increase the key length surprisingly and uses 3DES algorithm, which protects against “meet in the middle” attacks. Another advantage of the proposed asymmetrical cryptosystem is that it is free to change the user’s two private random numbers in generating the public keys at any time. Numerical simulation and performance analysis verify that the proposed asymmetric cryptosystem is effective and robust against attacks for the asymmetrical cipher system.

• Journal of the Optical Society of Korea
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• 제10권3호
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• pp.118-123
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• 2006

We present an optical security method for binary data information by using 4-step phase-shifting digital holography and we analyze tolerance error for the decrypted data. 4-step phase-shifting digital holograms are acquired by moving the PZT mirror with equidistant phase steps of ${\pi}/2$ in the Mach-Zender type interferometer. The digital hologram in this method is a Fourier transform hologram and is quantized with 256 gray level. The decryption performance of the binary data information is analyzed. One of the most important errors is the quantization error in detecting the hologram intensity on CCD. The greater the number of quantization error pixels and the variation of gray level increase, the more the number of error bits increases for decryption. Computer experiments show the results for encryption and decryption with the proposed method and show the graph to analyze the tolerance of the quantization error in the system.

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.74-81
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• 1999

The integrated chip of optical micro-encoder was fabricated and the feasibility as displacement measurement device was confirmed. The geometry of micro-encoder was designed to utilize the optical interference effect on the second order of diffracted beams. The hybrid-type micro-encoder consisted with light emitting diode, photodiode, polyimide wave-guide and micro-lens provides stable micro-encoding results for high speed displacements. The measurement shows the resolution of displacement of 1.00 +/- 0.02 ${\mu}m$ for the grating with scale pitch of 2.0${\mu}m$.