Abstract

We propose a new type phase locked interferometer which uses tunability of the wavelength of a laser diode. The phase lock is achieved by controlling the injection current of the laser diode. A CCD image sensor is used as a photodetector to scan electrically a measuring point along the surface of the object. Since this interferometer uses no mechanical elements such as a piezoelectric transducer and galvanomirror, the measurement accuracy is not limited by the mechanical properties. The characteristics of the feedback control system for the phase lock are examined through measurements of surface profiles of the diamondturned aluminum disks.

© 1989 Optical Society of America

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References

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  1. K. Tatsuno, Y. Tsunoda, “Diode Laser Direct Modulation Heterodyne Interferometer,” Appl. Opt. 26, 37–40 (1987).
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    [CrossRef] [PubMed]
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1988 (1)

1987 (3)

1986 (3)

1978 (1)

Chen, J.

Hamilton, D. K.

Ishii, Y.

Lee, B. S.

Matthews, H. J.

Mnatzakanian, S.

Moore, D. T.

Murata, K.

Murray, R.

Nara, M.

Neves, F. B.

Okazaki, H.

Sakai, M.

Sasaki, O.

Sheppard, C. J. R.

Strand, T. C.

Tatsuno, K.

Tsunoda, Y.

Yoshino, T.

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Figures (6)

Fig. 1
Fig. 1

Phase locked laser diode interferometer.

Fig. 2
Fig. 2

Block diagram of the feedback control system.

Fig. 3
Fig. 3

Value of IA for the various proportional gain Kp.

Fig. 4
Fig. 4

Surface profiles of sample I measured with (a) the PLLD interferometer and (b) the Talystep instrument.

Fig. 5
Fig. 5

Surface profiles of sample II measured with (a) the PLLD interferometer and (b) the Talystep instrument.

Fig. 6
Fig. 6

Normalized value of the measured amplitude of sample I as a function of ratio TI/Tscan.

Equations (10)

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I m ( t ) = a cos ω c t .
S ( t ) = S 0 cos [ z cos ω c t + α ( x ) ] ,
α ( x ) = ( 4 π / λ 0 ) [ D 0 + D ( x ) ] .
α L = ( 4 π / λ 0 ) D 0 .
( 4 π / λ 0 ) D 0 = [ 4 π / ( λ 0 + λ c ) ] [ D 0 + D ( x ) ] ,
λ c = β I c ( x ) .
D ( x ) = ( D 0 / λ 0 ) β I c ( x ) .
S ( t ) = S 0 [ cos α ( x ) ] [ J 0 ( z ) 2 J 2 ( z ) cos ( 2 ω c t ) + ] S 0 [ sin α ( x ) ] [ 2 J 1 ( z ) cos ω c t 2 J 3 ( z ) cos ( 3 ω c t ) + ] ,
U ( x ) = 2 J 1 ( z ) sin α ( x ) .
IAE = 0 1 | e ( t ) e s | d t ,

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