Abstract

Two-wavelength phase-measuring interferometry with dual laser-diode sources has been developed that is based on a phase-shifting method that uses two wavelengths varied stepwise by separately changing the currents in two laser diodes. A synthetic wavelength is produced by the addition of two single-wavelength interferograms without the need for auxiliary techniques. The phases are equally shifted in opposite directions to each other on an unbalanced interferometer. The fringe shifts that result from modulated phases are monitored with an electronic sensor to ensure accuracy. Our experimental result shows measurements of the profile of a step object with a 4.6-μm synthetic wavelength.

© 1991 Optical Society of America

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References

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    [CrossRef] [PubMed]
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1990 (1)

L. Bartolini, G. Fornetti, M. FerriDeCollibus, G. Occhionero, F. Papetti, Rev. Sci. Instrum. 61, 1177 (1990).
[CrossRef]

1989 (1)

Y. Ishii, Proc. Soc. Photo-Opt. Instrum. Eng. 1163, 176 (1989).

1988 (1)

1987 (1)

1985 (1)

1984 (1)

1974 (1)

1973 (1)

Bartolini, L.

L. Bartolini, G. Fornetti, M. FerriDeCollibus, G. Occhionero, F. Papetti, Rev. Sci. Instrum. 61, 1177 (1990).
[CrossRef]

Brangaccio, D. J.

Bruning, J. H.

Chen, J.

Cheng, Y.-Y.

Dändliker, R.

Fercher, A. F.

FerriDeCollibus, M.

L. Bartolini, G. Fornetti, M. FerriDeCollibus, G. Occhionero, F. Papetti, Rev. Sci. Instrum. 61, 1177 (1990).
[CrossRef]

Fornetti, G.

L. Bartolini, G. Fornetti, M. FerriDeCollibus, G. Occhionero, F. Papetti, Rev. Sci. Instrum. 61, 1177 (1990).
[CrossRef]

Gallagher, J. E.

Herriott, D. R.

Hu, H. Z.

Ishii, Y.

Y. Ishii, Proc. Soc. Photo-Opt. Instrum. Eng. 1163, 176 (1989).

Y. Ishii, J. Chen, K. Murata, Opt. Lett. 12, 233 (1987).
[CrossRef] [PubMed]

Murata, K.

Occhionero, G.

L. Bartolini, G. Fornetti, M. FerriDeCollibus, G. Occhionero, F. Papetti, Rev. Sci. Instrum. 61, 1177 (1990).
[CrossRef]

Papetti, F.

L. Bartolini, G. Fornetti, M. FerriDeCollibus, G. Occhionero, F. Papetti, Rev. Sci. Instrum. 61, 1177 (1990).
[CrossRef]

Polhemus, C.

Prongué, D.

Rosenfeld, D. P.

Thalmann, R.

Vry, U.

White, A. D.

Wyant, J. C.

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Figures (5)

Fig. 1
Fig. 1

Experimental arrangement for measurements of the test phase with dual FM LD's.

Fig. 2
Fig. 2

(a) LD1 and LD2 current variations increasing (solid line) and decreasing (dashed line) stepwise at the same time. (b) The intensity ij varying with time.

Fig. 3
Fig. 3

Interference signals (each lower trace) corresponding to I1 and I2 interferograms, respectively, matched to the reciprocally signed phase-shift condition in Eq. (4) and introduced by mutually inverted triangular waves (each upper trace) of the two LD currents.

Fig. 4
Fig. 4

Cross-sectional profiles of four sequential two-wavelength interferograms produced by dual FM LD's versus the object position. This demonstrates the π phase difference between the intensities marked by the arrows.

Fig. 5
Fig. 5

Three-dimensional phase maps of the test step object with single-wavelength (λ1) interferograms (top) and with two-wavelength (Λ) interferograms (bottom) with phase-shifting techniques.

Equations (5)

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i ( x , y , l ) = a ( x , y ) + b ( x , y ) cos { π [ 2 w ( x , y ) + l ] / Γ } × cos { π [ 2 w ( x , y ) + l ] / Λ } ,
δ k j = π l Δ λ k λ k 2 = j π l α k Δ i k λ k 2 ( j = 1 , , N ) ,
i j = a j + b j cos ( ψ δ 1 j δ 2 j ) cos ( Φ δ 1 j + δ 2 j ) ,
δ 1 j = δ 2 j ,
i j = a + b cos ( ψ ) cos ( Φ 2 δ 1 j ) ,

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