Abstract

Image-velocity sensors find application in aerial camera-control systems by providing the servo intelligence necessary to achieve accurate image-motion compensation. This paper explores the theory of operation of image-velocity sensors which employ a parallel-slit reticle to effect the light flux modulation resulting in a time frequency directly proportional to image velocity.

Experimental data is presented, and a graphical analysis is used to demonstrate the computing action of the parallel-slit sensor. The effect on signal quality of varying certain geometrical parameters is demonstrated, and limitations of the method are explored. An interesting conclusion is that the computing action is not dependent upon any inherent periodicity in the image. An approach to explaining the phenomenon by information-theory principles is outlined, and practical considerations involved in utilizing this effect in aerial photography are briefly explored.

© 1963 Optical Society of America

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References

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  1. U. S. Patent2,413,349: “Camera for Aerial Photography,” D. Hancock and H. E. Meinema, December1946.
  2. H. E. Meinema, Electronics 26, 135–137 (1953).
  3. Conducted by the author at Bill Jack Scientific Instrument Company, August 1950.
  4. A small fraction of a slitwidth.
  5. G. Aroyan, Proc. IRE 47, 1563 (1959).
    [Crossref]
  6. W. D. Montgomery, J. Opt. Soc. Am. 52, 1259 (1962).
    [Crossref]

1962 (1)

1959 (1)

G. Aroyan, Proc. IRE 47, 1563 (1959).
[Crossref]

1953 (1)

H. E. Meinema, Electronics 26, 135–137 (1953).

Aroyan, G.

G. Aroyan, Proc. IRE 47, 1563 (1959).
[Crossref]

Hancock, D.

U. S. Patent2,413,349: “Camera for Aerial Photography,” D. Hancock and H. E. Meinema, December1946.

Meinema, H. E.

H. E. Meinema, Electronics 26, 135–137 (1953).

U. S. Patent2,413,349: “Camera for Aerial Photography,” D. Hancock and H. E. Meinema, December1946.

Montgomery, W. D.

Electronics (1)

H. E. Meinema, Electronics 26, 135–137 (1953).

J. Opt. Soc. Am. (1)

Proc. IRE (1)

G. Aroyan, Proc. IRE 47, 1563 (1959).
[Crossref]

Other (3)

U. S. Patent2,413,349: “Camera for Aerial Photography,” D. Hancock and H. E. Meinema, December1946.

Conducted by the author at Bill Jack Scientific Instrument Company, August 1950.

A small fraction of a slitwidth.

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Figures (10)

Fig. 1
Fig. 1

Schematic representation of an aerial camera photographing flat terrain, showing basic geometrical factors.

Fig. 2
Fig. 2

Basic optical system arrangement for sensing image motion with a reticle.

Fig. 3
Fig. 3

Design of experiment to obtain record of typical light flux distribution in the terrain.

Fig. 4
Fig. 4

Recorded sample of typical light flux distribution in rural area terrain.

Fig. 5
Fig. 5

Method of numerical integration to compute light transmitted by reticle.

Fig. 6
Fig. 6

Results of image flux modulation by a typical (hypothetical) test reticle, computed by numerical integration process.

Fig. 7
Fig. 7

Image flux modulation results for various test reticles, computed by numerical integration. Slit-widths are approximate.

Fig. 8
Fig. 8

Fourier transform designations for reticle-scan system.

Fig. 9
Fig. 9

Reticle arrangement for ambient light cancellation.

Fig. 10
Fig. 10

Reticle assembly for automatic drift correction.

Equations (6)

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i = F tan θ , i = F ( X / H ) ,
d i / d t = ( F / H ) ( d x / d t ) ,
d i / d t = ( V / H ) ( F ) ,
d i / d t = V F cos θ / H .
F time ( cps ) = ( d i / d t ) ( in . / sec ) F space ( cycles / in . ) .
I ( x , y , t ) = 0 1 ( t ) 0 2 ( x , y ) L ( x , y ) R ( x , y ) ,