Abstract

The use of digital image processing techniques for electronic speckle pattern interferometry is discussed. A digital TV-image processing system with a large frame memory allows us to perform precise and flexible operations such as subtraction, summation, and level slicing. Digital image processing techniques make it easy compared with analog techniques to generate high contrast fringes. Some experimental verifications are presented in the cases of surface displacement and vibration amplitude measurements.

© 1980 Optical Society of America

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References

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  1. J. N. Butters, J. A. Leendertz, Opt. Laser Technol. 3, 26 (1971).
    [CrossRef]
  2. A. Macovski, S. D. Ramsey, L. F. Schaefer, Appl. Opt. 10, 2722 (1971).
    [CrossRef] [PubMed]
  3. T. J. Cookson, J. N. Butters, H. C. Pollard, Opt. Laser Technol. 10, 119 (1978).
    [CrossRef]
  4. O. J. Lokberg, O. M. Holje, H. M. Pedersen, Opt. Laser Technol. 8, 17 (1976).
    [CrossRef]
  5. T. Nakajima, H. Saito, Jpn. J. Opt. 8, 91 (1979) (in Japanese).
  6. L. Ek, N.-E. Molin, Opt. Commun. 2, 419 (1971).
    [CrossRef]

1979

T. Nakajima, H. Saito, Jpn. J. Opt. 8, 91 (1979) (in Japanese).

1978

T. J. Cookson, J. N. Butters, H. C. Pollard, Opt. Laser Technol. 10, 119 (1978).
[CrossRef]

1976

O. J. Lokberg, O. M. Holje, H. M. Pedersen, Opt. Laser Technol. 8, 17 (1976).
[CrossRef]

1971

L. Ek, N.-E. Molin, Opt. Commun. 2, 419 (1971).
[CrossRef]

J. N. Butters, J. A. Leendertz, Opt. Laser Technol. 3, 26 (1971).
[CrossRef]

A. Macovski, S. D. Ramsey, L. F. Schaefer, Appl. Opt. 10, 2722 (1971).
[CrossRef] [PubMed]

Butters, J. N.

T. J. Cookson, J. N. Butters, H. C. Pollard, Opt. Laser Technol. 10, 119 (1978).
[CrossRef]

J. N. Butters, J. A. Leendertz, Opt. Laser Technol. 3, 26 (1971).
[CrossRef]

Cookson, T. J.

T. J. Cookson, J. N. Butters, H. C. Pollard, Opt. Laser Technol. 10, 119 (1978).
[CrossRef]

Ek, L.

L. Ek, N.-E. Molin, Opt. Commun. 2, 419 (1971).
[CrossRef]

Holje, O. M.

O. J. Lokberg, O. M. Holje, H. M. Pedersen, Opt. Laser Technol. 8, 17 (1976).
[CrossRef]

Leendertz, J. A.

J. N. Butters, J. A. Leendertz, Opt. Laser Technol. 3, 26 (1971).
[CrossRef]

Lokberg, O. J.

O. J. Lokberg, O. M. Holje, H. M. Pedersen, Opt. Laser Technol. 8, 17 (1976).
[CrossRef]

Macovski, A.

Molin, N.-E.

L. Ek, N.-E. Molin, Opt. Commun. 2, 419 (1971).
[CrossRef]

Nakajima, T.

T. Nakajima, H. Saito, Jpn. J. Opt. 8, 91 (1979) (in Japanese).

Pedersen, H. M.

O. J. Lokberg, O. M. Holje, H. M. Pedersen, Opt. Laser Technol. 8, 17 (1976).
[CrossRef]

Pollard, H. C.

T. J. Cookson, J. N. Butters, H. C. Pollard, Opt. Laser Technol. 10, 119 (1978).
[CrossRef]

Ramsey, S. D.

Saito, H.

T. Nakajima, H. Saito, Jpn. J. Opt. 8, 91 (1979) (in Japanese).

Schaefer, L. F.

Appl. Opt.

Jpn. J. Opt.

T. Nakajima, H. Saito, Jpn. J. Opt. 8, 91 (1979) (in Japanese).

Opt. Commun.

L. Ek, N.-E. Molin, Opt. Commun. 2, 419 (1971).
[CrossRef]

Opt. Laser Technol.

J. N. Butters, J. A. Leendertz, Opt. Laser Technol. 3, 26 (1971).
[CrossRef]

T. J. Cookson, J. N. Butters, H. C. Pollard, Opt. Laser Technol. 10, 119 (1978).
[CrossRef]

O. J. Lokberg, O. M. Holje, H. M. Pedersen, Opt. Laser Technol. 8, 17 (1976).
[CrossRef]

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Figures (9)

Fig. 1
Fig. 1

Schematic diagram of arrangement for normal displacement measurement. Digital image processing system consists of high speed ADC, digital frame memory, memory update controller, nonlinear signal processor, and DAC.

Fig. 2
Fig. 2

Schematic representation of nonlinear processing for output signal: (a) half-wave rectification; (b) level slicing; and (c) one level windowing.

Fig. 3
Fig. 3

Fringes obtained by (a) half-wave rectification, (b) level slicing at 37th level, and (c) one level windowing at 43rd level.

Fig. 4
Fig. 4

Implementation of a binary correlator using analog preprocessor of level slicing and digital operations.

Fig. 5
Fig. 5

Interferogram obtained by the binary correlator shown in Fig. 4. Fringe pattern was displayed by means of one level windowing at 195th level.

Fig. 6
Fig. 6

Interferogram showing transient behavior of circular plate obtained by level slicing at 25th level. Object vibrated at 0.05 Hz, and subtraction was carried out at intervals of (a) 0.5, (b) 1.0, and (c) 1.5 sec.

Fig. 7
Fig. 7

Schematic diagram of arrangement for lateral displacement measurement.

Fig. 8
Fig. 8

Typical fringe pattern obtained for circular disk rotating about center axis normal to its plane. Signal after subtraction was subjected to level slicing at 10th level. Average speckle size was 8.6 μm.

Fig. 9
Fig. 9

Typical vibration mode of object obtained by summation of 60 frames of speckle patterns. Signal after summation was subjected to level slicing at 95th level. Frequency of vibration was 2.45 kHz. Brightest and second brightest fringes show vibration amplitudes of zero and 0.19 μm, respectively.

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