• Current Optics and Photonics
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• v.2 no.6
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• pp.612-622
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• 2018

In wave-front-sensor-less adaptive optics (WFS-less AO) systems, the Jacopo Antonello (JA) method belongs to the model-based class and requires few iterations to achieve acceptable distortion correction. However, this method needs a lot of measurements, especially when it deals with moderate or severe aberration, which is undesired in free-space optical communication (FSOC). On the contrary, the stochastic parallel gradient descent (SPGD) algorithm only requires three time measurements in each iteration, and is widely applied in WFS-less AO systems, even though plenty of iterations are necessary. For better and faster compensation, we propose a WFS-less hybrid approach, borrowing from the JA method to compensate for low-order wave front and from the SPGD algorithm to compensate for residual low-order wave front and high-order wave front. The correction results for this proposed method are provided by simulations to show its superior performance, through comparison of both the Strehl ratio and the convergence speed of the WFS-less hybrid approach to those of the JA method and SPGD algorithm.

• Current Optics and Photonics
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• v.5 no.6
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• pp.606-616
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• 2021

A photonic integrated interferometric imaging system possesses the characteristics of small-scale, low weight, low power consumption, and better image quality. It has potential application for replacing conventional large space telescopes. In this paper, the principle of photonic integrated interferometric imaging is investigated. A novel lenslet array arrangement and lenslet pairing approach are proposed, which are helpful in improving spatial frequency coverage. For the novel lenslet array arrangement, two short interference arms were evenly distributed between two adjacent long interference arms. Each lenslet in the array would be paired twice through the novel lenslet pairing approach. Moreover, the image reconstruction model for optical interferometric imaging based on compressed sensing was established. Image simulation results show that the peak signal to noise ratio (PSNR) of the reconstructed image based on compressive sensing is about 10 dB higher than that of the direct restored image. Meanwhile, the normalized mean square error (NMSE) of the direct restored image is approximately 0.38 higher than that of the reconstructed image. Structural similarity index measure (SSIM) of the reconstructed image based on compressed sensing is about 0.33 higher than that of the direct restored image. The increased spatial frequency coverage and image reconstruction approach jointly contribute to better image quality of the photonic integrated interferometric imaging system.

• Current Optics and Photonics
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• v.7 no.5
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• pp.529-536
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• 2023

The Morlet wavelet transform method is proposed to analyze a single interferogram with spatial carrier frequency that is captured by an optical interferometer. The method can retain low frequency components that contain the phase information of a measured optical surface, and remove high frequency disturbances by wavelet decomposition and reconstruction. The key to retrieving the phases from the low-frequency wavelet components is to extract wavelet ridges by calculating the maximum value of the wavelet transform amplitude. Afterwards, the wrapped phases can be accurately solved by multiple iterative calculations on wavelet ridges. Finally, we can reconstruct the wave-front of the measured optical element by applying two-dimensional discrete cosine transform to those wrapped phases. Morlet wavelet transform does not need to remove the spatial carrier frequency components manually in the processing of interferogram analysis, but the step is necessary in the Fourier transform algorithm. So, the Morlet wavelet simplifies the process of the analysis of interference fringe patterns compared to Fourier transform. Consequently, wavelet transform is more suitable for automated programming analysis of interference fringes and avoiding the introduction of additional errors compared with Fourier transform.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.55-60
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• 2007

The shadow, reflection, interference, and diffraction are proper phenomena concerning sound that is a kind of wave. By the late nineteenth century, similar optical phenomena had been detected already but these phenomena concerning sound had not been convincingly detected. It was Rayleigh who succeeded in detecting those phenomena without any reasonable doubt by the virtue of his original instruments and smart experimental settings. Rayleigh could detect the sound shadow by using the corner of a building and erase the shadow by some reflectors. And he constructed some apparatus similar to Young's interference apparatus famous in optics to detect the sonic interference. Furthermore, he first succeeded in illustrating the acoustical effectiveness of Poisson's disk by which optical diffraction had already been well known, and tested the effect of diffraction by spherical obstacles to ascertain that the result coincided with his theory.

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.11-11
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• 2004

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.77-80
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• 2001

In this paper, it is analyzed the statistical characteristics on the transmission performance of the optical SCM transmission in the CDMA RF signal relay system. Using Mach-Zehnder modulator, optical signal is regenerated into CDMA RF signal. Transfer function model of mach-Zehnder modulator is approximated to the third power of the input signal using Taylor series. BER results are analyzed under the multiple access interference and multi-path fading environment.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.493-495
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• 2005

The director profiles of the Bloch walls are directly visualized using fluorescence confocal polarizing microscopy. Both pure twist Bloch walls and diffuse Bloch walls are analyzed. Polar anchoring energy was measured from optical simulation of the transmitted light interference pattern or the fluorescence intensity profile of a pure twist wall..

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.84-85
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• 2003

최근 데이터 용량이 급격히 증가하면서 대용량의 정보를 전달할 수 있는 광통신 시스템의 대역폭이 증가되고 있다. 이러한 대역폭의 문제를 해결하기 위하여 한 개의 광섬유에 여러 개의 파장을 사용함으로써 대역폭을 증가시키는 WDM 기술이 대두되었으며, 사용되는 파장의 간격이 점차 좁아지고 있다. 따라서 채널 간격이 매우 좁은 고밀도 WDM(DWDM)기술에는 일정한 간격으로 여러 채널들을 분리시키고 합치는 파장분할 다중소자가 필요하다. (중략)

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.239-241
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• 2002

Basically, OCT used the interference effect of Michelson interferometer. First, we have analyzed the optical heterodyne interferometer for OCT. Second, we implement new optical heterodyne interferometer for OCT.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.442-445
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• 2004

We report principles and results of design large FOV retinal display systems by software WinDEMOS and software for computer testing display systems TEDiS. We discuss results design head mounted and head up display. As combiner we are used volume interference recorded or synthetic HOE, and as the sours of the image high resolution transmitting or reflective liquid crystal matrixes on silicon (LCOS) or CRT.