• 한국생산제조학회지
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• 제8권4호
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• pp.130-135
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• 1999

The main scale of linear encoder greatly effects on the precision of displacement measurement. Especially when needing the long range measurement the length of main scale should be increased accordingly. In this paper we propose a linear encoder that uses laser interference pattern as main scale for long range measurement. The linear encoder is similar to Michelson interferometer excepting that the reference mirror is tilted so as to obtain interference fringe pattern and a grating panel is attached on a quadratic photo diodes. Four kinds of grating having phase difference of 0. $\pi$/4, $\pi$/2, 3$\pi$/4 are arranged on the panel. The experimental results show that signals of quadratic photo diode A, B, {{{{ {-}atop {A } }}}} and {{{{ {- } atop {B } }}}} are cosine wavelike and successive signals have phase difference of $\pi$/4 each other. So the proposed method can achieve improved measurement resolution.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.977-980
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• 1998

A real-time holography system using LCD with CCD camera is proposed. In this system, the rainbow hologram is used since it can be reconstructed by white light source. And to record on CCD camera, a kind of in-line holography method is used to widen the width of the fringe pattern. The interference fringe pattern by proposed system is detected with CCD camera and transferred to the LCD A 3-dimensional image is reconstructed when a white light source illuminates the LCD. So it can represent 3 dimensional moving images at real-time. In this paper, to confirm the usefulness of the proposed method, the reconstructed image by holographic film is compared to the same reconstruct image by LCD. In the recording of the interferenced processing, the optimal ratio of the reference and object beam intenstiy is also investigated.

• 대한기계학회논문집A
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• 제20권2호
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• pp.564-574
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• 1996

This paper describes as Electronic Speckle Pattern Interferometry system which has been designed for measuring vibration patterns and quantitative measurement of vibration amplitude fields by using the time average method on a object. Visbility of fringe patterns is more improved by using the phase stepping and frame average method to reduce speckle and electric noise. And a bias vibration is introduced into the reference beam to shift the $\frac{2}{0}$ fringes so that fringe shift algorithms can be used to determine vibration amplitude. The experimental results are compared to those of the FFT analyzer and the FEM model analysis.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.264-271
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• 2011

In this paper we examine and compare the computational speeds of three-dimensional (3D) object recognition by use of digital holography based on central unit processing (CPU) and graphic processing unit (GPU) computing. The holographic fringe pattern of a 3D object is obtained using an in-line interferometry setup. The Fourier matched filters are applied to the complex image reconstructed from the holographic fringe pattern using a GPU chip for real-time 3D object recognition. It is shown that the computational speed of the 3D object recognition using GPU computing is significantly faster than that of the CPU computing. To the best of our knowledge, this is the first report on comparisons of the calculation time of the 3D object recognition based on the digital holography with CPU vs GPU computing.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.170-175
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• 1999

Noncontact measuring methodology of 3-dimensional profile using CCD camera are very attractive because of it's high measuring speed and its's high sensitivity. Especially, when projecting a grid pattern over the object the captured image have 3 dimensional information of the object. Projection moire extract 3-D information with another grid pattern in front of CCD camera. However phase measuring profilometry(PMP) obtain similar results without additional grid pattern. In this paper, new method for grid pattern generation system by polygonal mirror and Laser Diode. This system is applied the projection moire and the PMP.

• 한국전기전자재료학회논문지
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• 제18권8호
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• pp.720-723
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• 2005

We studied the quantitativity of the image sticking which is occured by the resicual DC in the fringe-electric field switching (FFS) mode. Actually, in the FFS mode driven by the strong fringe electric field, the asymmetric residual DC was formed in the bottom substrate. It made the impurity ion stick to the alignment layer such as polyimde layer. Thus, the differnece of the luminance existes after the stress check pattern is applied to the panel so that we can see the image sticking. This image sticking decreases as the residual DC value between specific patterns decreases. Therefore, it is necessary to control the residual DC for the FFS mode with the high image quality. It is possible to eliminate the image stiking when the extra pixel voltage is applied through the circuit tunning for reducing the difference of residual DC accroding to the panel position.

• Journal of the Optical Society of Korea
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• 제13권2호
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• pp.251-255
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• 2009

In the non-contact 3-dimensional (3D) shape measurements, the fringe pattern projection method based on the phase-shifting technique has been considered very effective for its high speed and accuracy. The digital fringe projector in particular has great flexibility in generating fringe patterns since the patterns can be controlled easily by the computer program. In this work, we have developed a high-speed digital laser grating projection system using a laser diode and a polygon mirror, and evaluated its performance. It has been demonstrated that all the optical measurements required to find out the profile of a 3D object could be carried out within 31 ms, which confirmed the validity of our 3D measurement system. The result implies the more important fact that the speed in 3D measurement can be enhanced remarkably since, in our novel system, there is no device like a LCD or DMD whose response time limits the measurement speed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 추계학술대회 논문요약집
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• pp.259-259
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• 2003

• 대한지리학회지
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• 제29권
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• pp.1-19
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• 1984

• 한국통신학회논문지
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• 제32권2C호
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• pp.132-140
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• 2007

본 논문에서는 디지털화된 형태로 취득 및 저장된 홀로그램 신호를 부호화하는 새로운 기술을 제안한다. 디지털 홀로그램의 독특한 특성을 파악하여 적절한 형태의 데이터로 변환한 후에 현재 널리 사용되고 있는 표준 압축 기술들에 적용하고자 한다. 전처리과정 이후에 부호화를 위해 추출된 홀로그램은 위치적인 다시점 특성을 이용하여 분할된다. 분할된 홀로그램은 2차원의 여러 시점에서 객체를 촬영한 것과 유사한 특성을 보인다. 시각적으로 잡음과 유사한 형태로 관찰되는 홀로그램의 회절 패턴은 그 자체로써 압축에 이용하기 어렵다. 따라서 홀로그램 생성 원리와 유사하면서 고속 변환이 가능한 2차원 DCT (Discrete Cosine Transform)를 이용하여 분할된 홀로그램을 주파수 변환한다. 주파수 변환된 분할 영역들은 시간적 및 공간적 상관도에 따라서 3차원 스캔 과정을 거치면서 하나의 비디오 스트림으로 구성된다. 비디오 스트림의 한 프레임에 해당하는 분할된 영역들은 다양한 범위를 가지는 계수들로 구성되는데 이를 재구성한 후에 부호화 알고리즘을 이용하여 압축한다. 실험 결과를 살펴보면 제안한 알고리즘은 기존의 기술에 비해서 16배 이상의 높은 압축율에서 더 좋은 복원 성능을 보였다.