Abstract

Acoustic pressure is directly converted to a parallel 3-bit binary code using optical interference. Since the diaphragm deforms sinusoidally when pressure is applied, the interference is different from point to point on the diaphragm. We simultaneously detected the interference intensity at an adequate sampling of three points. A quantized bit plane is produced in parallel without scanning. The dynamic range is ±240 Pa, and good linearity is obtained. This method can be used to measure other quantities such as temperature and voltage.

© 1983 Optical Society of America

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References

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  1. A. Armand, A. A. Sawchuk, T. C. Strand, D. Boswell, B. H. Soffer, Opt. Lett. 5, 129 (1980).
    [CrossRef] [PubMed]
  2. G. D. H. King, R. Cebulski, Electron. Lett. 18, 1099 (1982).
    [CrossRef]
  3. M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), Sec. 7.6.

1982 (1)

G. D. H. King, R. Cebulski, Electron. Lett. 18, 1099 (1982).
[CrossRef]

1980 (1)

Armand, A.

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), Sec. 7.6.

Boswell, D.

Cebulski, R.

G. D. H. King, R. Cebulski, Electron. Lett. 18, 1099 (1982).
[CrossRef]

King, G. D. H.

G. D. H. King, R. Cebulski, Electron. Lett. 18, 1099 (1982).
[CrossRef]

Sawchuk, A. A.

Soffer, B. H.

Strand, T. C.

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), Sec. 7.6.

Electron. Lett. (1)

G. D. H. King, R. Cebulski, Electron. Lett. 18, 1099 (1982).
[CrossRef]

Opt. Lett. (1)

Other (1)

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), Sec. 7.6.

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Figures (5)

Fig. 1
Fig. 1

Optical system for direct analog-to-digital conversion for microphone: HM, half mirror; RP, reference plane; D, diaphragm; Det, detector (photodiode array).

Fig. 2
Fig. 2

Displacement of the diaphragm and the interference light intensity. Solid lines and dashed lines are light intensity and quantized value, respectively.

Fig. 3
Fig. 3

Pressure dependence of the interference light intensity.

Fig. 4
Fig. 4

Shift of the beam reflected from the diaphragm. The symbols are in the text.

Fig. 5
Fig. 5

Linearity of the 3-bit binary code.

Equations (8)

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I n = r 1 2 + r 2 2 2 r 1 r 2 cos 4 π λ ( d u n ) 1 + r 1 2 r 2 2 2 r 1 r 2 cos 4 π λ ( d u n ) I 0 ,
u = u max cos π 2 r x ,
s = ( L u ) tan θ = ( L u ) tan | π 2 r u max 2 u 2 | ,
s = L π 2 r u max 2 u 2 .
s = L π λ 8 r 2 2 n 1 .
w > s = L π λ 8 r 2 2 n 1 .
V P = F P U P V U ,
V n P = F P U n F I n U n V n I n .

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