Abstract

In an earlier paper, Agrawal and McCullough demonstrated that a single laser beam focused at the point of measurement can be used to obtain both the magnitude and direction of local fluid velocity without the use of beam-splitting optics or frequency biasing devices. Additionally, the photoelectric signal was shown to be a zero-mean sine wave suitable for existing counter-type laser Doppler velocimeter signal processors. The method described in the above paper indicated the use of two offset photodetector arrays; the resulting photocurrents from the two arrays were correlated to give direction. In this paper we describe the implementation of the method using a self-scanning diode array. Detector sensitivity in the array is discussed and microchannel plate detectors are suggested for increased sensitivity.

© 1984 Optical Society of America

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References

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  1. Y. C. Agrawal, J. R. McCullough, Appl. Opt. 20, 1553 (1981).
    [CrossRef] [PubMed]
  2. M. J. Rudd, J. Phys. E 2, 723 (1969).
    [CrossRef]
  3. Y. C. Agrawal, “A CCD Chirp-Z FFT Doppler signal processor for laser velocimetry”, J. Phys. E. submitted for publication.

1981 (1)

1969 (1)

M. J. Rudd, J. Phys. E 2, 723 (1969).
[CrossRef]

Agrawal, Y. C.

Y. C. Agrawal, J. R. McCullough, Appl. Opt. 20, 1553 (1981).
[CrossRef] [PubMed]

Y. C. Agrawal, “A CCD Chirp-Z FFT Doppler signal processor for laser velocimetry”, J. Phys. E. submitted for publication.

McCullough, J. R.

Rudd, M. J.

M. J. Rudd, J. Phys. E 2, 723 (1969).
[CrossRef]

Appl. Opt. (1)

J. Phys. E (1)

M. J. Rudd, J. Phys. E 2, 723 (1969).
[CrossRef]

Other (1)

Y. C. Agrawal, “A CCD Chirp-Z FFT Doppler signal processor for laser velocimetry”, J. Phys. E. submitted for publication.

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Figures (7)

Fig. 1
Fig. 1

Schematic of the simplified optical arrangement.

Fig. 2
Fig. 2

Linear photodiode array, with the spatial response function as shown in (a) is electronically arranged to produce two periodic arrays (b) and (c).

Fig. 3
Fig. 3

Sensitivity of the array as a ratio of the width of the central lobe of the diffraction-limited image to the period of the detector array 2π/K′.

Fig. 4
Fig. 4

Diffraction-limited image travels across the periodic response photodetector array (a) producing the photocurrent shown in (b).

Fig. 5
Fig. 5

Electronic block diagram.

Fig. 6
Fig. 6

Photocurrents observed when a diffraction-limited image (a) traverses across the array. In (b), the top and bottom traces represent the two photocurrents I1 and I2.

Fig. 7
Fig. 7

Signals observed from the differential arrays A and B. The sudden change of phase in the middle of the figure is caused by the arrival of a second particle before the first leaves the probe volume.

Equations (4)

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E ( z ) = C A ( l ) H ( z - M l ) .
I i = C A 2 ( l ) H ( z - M l ) 2 n B n cos ( n K z + ϕ n i ) d z ,
f c = 1 2 π M u K , where u = v ¯ · n ¯ .
I = A 2 ( l ) cos 2 ( M k δ z f 0 ) H ( z - M l ) 2 B n cos ( n K z + ϕ n ) d z .

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