Computer Input
Figure 1 LR-1 Line Rectifier
module on the right contains the input unit and com-
puter.
The input unit includes the photocarrier and radial
arm measuring assembly. The photocarrier contains
adjustable back illumination for viewing transparen-
cies. The radial arm assembly projects the illuminated
measuring mark down onto the image as a dot of light
surrounded by an open circle and cross. The intensity
of the mark is adjustable. A small support keeps the
radial arm at a constant height above the image, pre-
serving the measuring-mark focus. The lengths and
angles of the two radial arm segments establish the
image location of the measuring mark. Precision re-
solvers continuously measure the sines and cosines of
the angles; since the segment lengths are constant,
simple trigonometric relations express the Cartesian
coordinates of the mark at any time. The radial arm
assembly can be disconnected from the photocarrier
and used on any flat surface if desired.
When plotting rectified images, the operator grips
an adjustable control knob on the radial arm assem-
bly and moves the measuring mark over the images of
interest. The operator can change the friction of each
radial arm with a small screw to provide the desired
subjective “feel” while tracing. The input unit can be
tilted forward and down over the computer for opera-
tor convenience while plotting, as shown in Figure 2.
The electronic analog computer is packaged in a
compartment about 30 cm wide, 45 cm deep, and 10
cm high. Microelectronic circuitry is used to minimize
the size of the computer. Most of the input controls
are located on the front face of the computer.
The plotter unit consists of the base cabinet, vacu-
um table, and X-Y assembly. The base cabinet con-
tains the controls for the output offset, polarity, and
scale, in addition to supporting the vacuum table and
X-Y assembly. The vacuum table, made of a single
piece of microperforated stainless steel, 56 cm square,
holds the manuscript and may be used in either a
horizontal or an upright position. A small fan creates
LR-1 PORTABLE RECTIFIER
Figure 2 Input/Computer Module—
Input in Operate Position
sufficient pressure differential to hold the plotting
paper on the table. The X-Y assembly includes the
drive motors for the X and Y axes; as shown in Figure
3, it may be removed from the vacuum table and used
on any flat surface if desired.
The plotting head holds an ordinary lead pencil or
ball-point pen. It plots the rectified and scaled traced
photo images at speeds up to 25 cm per second. The
pen or pencil is lowered and raised under control of a
foot-switch.
Figure 3 X-Y Plotting System
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