• Title/Summary/Keyword: optical interferometry

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Holospeckle interferometry for measureen of 3-D displacement (3차원 변위측정을 위한 홀로스펙클 간섭법)

  • 박승옥
    • Proceedings of the Optical Society of Korea Conference
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    • 1990.02a
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    • pp.131-135
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    • 1990
  • The combined technique of holographic interferometry and speckle photography, so called holospeckle interferometry, has been attention for the measurement of 3-D displacements. This new technique enables the researcher to obtain information of in plane and out-of plane displacements from one photographic plate. There is room for further development of special optical arrangement in order to apply holospeckle interferometry in specific field. In this study, the enlarged fringe pattern was obtained by specifical optical arrangement.

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Nano-level High Sensitivity Measurement Using Microscopic Moiré Interferometry (마이크로 무아레 간섭계를 이용한 초정밀 변형 측정)

  • Joo, Jin-Won;Kim, Han-Jun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.2
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    • pp.186-193
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    • 2008
  • [ $Moir{\acute{e}}$ ] interferometry is an optical method, providing whole field contour maps of in-plane displacements with high resolution. The demand for enhanced sensitivity in displacement measurements leads to the technique of microscopic $moir{\acute{e}}$ interferometry. The method is an extension of the $moir{\acute{e}}$ interferometry, and employs an optical microscope for the required spatial resolution. In this paper, the sensitivity of $moir{\acute{e}}$ interferometry is enhanced by an order of magnitude using an immersion interferometry and the optical/digital fringe multiplication(O/DFM) method. In fringe patterns, the contour interval represents the displacement of 52 nm per fringe order. In order to estimate the reliability and the applicability of the optical system implemented, the measurements of rigid body displacements of grating mold and the coefficient of thermal expansion(CTE) for an aluminium block are performed. The system developed is applied to the measurement of thermal deformation in a flip chip plastic ball grid array package.

Measurement of a Mirror Surface Topography Using 2-frame Phase-shifting Digital Interferometry

  • Jeon, Seok-Hee;Gil, Sang-Keun
    • Journal of the Optical Society of Korea
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    • v.13 no.2
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    • pp.245-250
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    • 2009
  • We propose a digital holographic interference analysis method based on a 2-frame phase-shifting technique for measuring an optical mirror surface. The technique using 2-frame phase-shifting digital interferometry is more efficient than multi-frame phase-shifting techniques because the 2-frame method has the advantage of a reduced number of interferograms, and then takes less time to acquire the wanted topography information from interferograms. In this measurement system, 2-frame phase-shifting digital interferograms are acquired by moving the reference flat mirror surface, which is attached to a piezoelectric transducer, with phase step of 0 or $\pi$/2 in the reference beam path. The measurements are recorded on a CCD detector. The optical interferometry is designed on the basis of polarization characteristics of a polarizing beam splitter. Therefore the noise from outside turbulence can be decreased. The proposed 2-frame algorithm uses the relative phase difference of the neighbor pixels. The experiment has been carried out on an optical mirror which flatness is less than $\lambda$/4. The measurement of the optical mirror surface topography using 2-frame phase-shifting interferometry shows that the peak-to-peak value is calculated to be about $0.1779{\mu}m$, the root-mean-square value is about $0.034{\mu}m$. Thus, the proposed method is expected to be used in nondestructive testing of optical components.

The effect of background subtraction of the interogram on the accuracy of the reconstructed wavefront in digital interferometry (Digital Interferometry에서 간섭무늬의 배경제거가 재생된 파면의 정확도에 미치는 영향)

  • 강주식;이상수
    • Proceedings of the Optical Society of Korea Conference
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    • 1988.06a
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    • pp.68-75
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    • 1988
  • The imporance and technique of sudtrating the background intensity of the interferogram in digital interferometry is discussed. Also the way of determinating the polynomial and its degree to fit the wavefront is discussed.

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Optical Encryption Scheme for Cipher Feedback Block Mode Using Two-step Phase-shifting Interferometry

  • Jeon, Seok Hee;Gil, Sang Keun
    • Current Optics and Photonics
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    • v.5 no.2
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    • pp.155-163
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    • 2021
  • We propose a novel optical encryption scheme for cipher-feedback-block (CFB) mode, capable of encrypting two-dimensional (2D) page data with the use of two-step phase-shifting digital interferometry utilizing orthogonal polarization, in which the CFB algorithm is modified into an optical method to enhance security. The encryption is performed in the Fourier domain to record interferograms on charge-coupled devices (CCD)s with 256 quantized gray levels. A page of plaintext is encrypted into digital interferograms of ciphertexts, which are transmitted over a digital information network and then can be decrypted by digital computation according to the given CFB algorithm. The encryption key used in the decryption procedure and the plaintext are reconstructed by dual phase-shifting interferometry, providing high security in the cryptosystem. Also, each plaintext is sequentially encrypted using different encryption keys. The random-phase mask attached to the plaintext provides resistance against possible attacks. The feasibility and reliability of the proposed CFB method are verified and analyzed with numerical simulations.

Absolute Temperature Measurement using White Light Interferometry

  • Kim, Jeong-Gon
    • Journal of the Optical Society of Korea
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    • v.4 no.2
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    • pp.89-93
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    • 2000
  • Recently a new signal processing algorithm for white light interferometry was presented. In this paper, the proposed signal processing algorithm was applied for absolute temperature measurement using white light interferometry. Stability testing and absolute temperature measurement were demonstrated. Stability test demonstrated the feasibility of absolute temperature measurement with an accuracy of 0.015 fringe. The test also showed that the absolute temperature measurement system using white light interferometry is capable of obtaining the theoretical minimum detectable change (0.0005 fringe), which is consistent with the performance predicted by the proposed signal processing algorithm.

Application of Phase-Shifting Method in Speckle Interferomtery to Measurement of Micro-Scale Displacement

  • Baek, Tae-Hyun;Kim, Myung-Soo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.3
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    • pp.162-168
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    • 2006
  • Speckle interferometry with phase-shifting method has been applied to measurement of micro-scale displacement through optical signal processing. Four-step phase-shifting method by PZT is used to measure out-of-plane displacement in spot-welded cantilever and results of optical experiments are comparable to those of FEM. Phase-shifting method using Fourier transform by PZT is applied to measurement of in-plane displacement on rectangular steel plate with a circular hole. The results of optical experiment agree well with theoretical calculation. New phase-shifting method in speckle interferometry has been implemented with a quarter wave plate. In-plane displacement of specimen is measured by the new phase-shifting method. Results of optical experiment show that the quarter wave plate can be used for phase-shifting method that is cheap and easy to use in speckle interferometry.

Common-path Optical Interferometry for Stabilized Dynamic Contrast Imaging: A Feasibility Study

  • Seung-Jin, Lee;Young-Wan, Choi;Woo June, Choi
    • Current Optics and Photonics
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    • v.7 no.1
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    • pp.65-72
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    • 2023
  • The motion of organelles inside a cell is an important intrinsic indicator for assessing cell physiology and tissue viability. Dynamic contrast full-field optical coherence tomography (D-FFOCT) is a promising imaging technology that can visualize intracellular movements using the variance of temporal interference signals caused by biological motions. However, double-path interferometry in D-FFOCT can be highly vulnerable to surrounding noise, which may cause turbulence in the interference signals, contaminating the sample dynamics. Therefore, we propose a method for stabilized D-FFOCT imaging in noisy environments by using common-path interferometry in D-FFOCT. A comparative study shows that D-FFOCT with the proposed method achieves stable dynamic contrast imaging of a scattering phantom in motion that is over tenfold more noise-insensitive compared to the conventional one, and thus this imaging capability can provide cleaner motion contrast images. With the proposed approach, the intracellular dynamics of biological samples are imaged and monitored.

Accuracy Improvement and Systematic Bias Analysis of Scanning White Light Interferometry for Free-form Surfaces Measurements (자유 곡면 형상 측정을 위한 백색광 주사 간섭계의 정확도 향상 및 시스템 오차 분석)

  • Ghim, Young-Sik;Davies, Angela;Rhee, Hyug-Gyo
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.7
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    • pp.605-613
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    • 2014
  • Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.