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Advanced Sensors in Pr ecision Manufacturing
are used to sample and process the return signal. Lenses shape that 307
laser light into a plane wave incident upon the acoustooptical sensor.
The integration in space is effected at the moment of sampling by the
focusing action. The position of the focal point in the cell depends on
the range delay of the corresponding target, and light is brought to
focus on two CCD imaging arrays at positions that depend on the
range.
The sinusoidal reference signal component of the cell interacts
with laser radiation to generate a plane wave of light that interferes
with the light focused by the cell. This produces interference fringes
that encode the phase information in the range-compressed optical
signal. These fringes are correlated with a mask that has a predeter-
mined spatial distribution of density and that is placed in front of, or
on, one of the CCD arrays. This CCD array is operated in a delay-
and-integrate mode to obtain the desired correlation and integration
in time for the azimuth compression. The output image is continu-
ously taken from the bottom picture element of the CCD array.
Two CCDs are used to alleviate a large undesired bias of the
image that occurs at the output as a result of optical processing. CCD
1
is used to compute this bias, which is then subtracted from the image
of CCD to obtain a better image.
2

6.22 The Use of Optoelectronic/Vision Associative
Memory for High-Precision Image Display
and Measurement
Storing an image of an object often requires large memory capacity
and a high-speed interactive controller. Figure 6.24 shows schemati-
cally an optoelectronic associative memory that responds to an input

FIGURE 6.24 A developmental optoelectronic associative memory.