HAMAR LASER STEALTH Series, General Training Manual

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Target Cell Function and Accuracy
Hamar Laser targets use a position-sensitive cell
with varying ranges of detection. This type of cell
will integrate to and find the center of energy of
any light shining on the surface, regardless of the
light spot's shape or size. There are four
connections on the front face of the cell--two
vertical connections and two horizontal
connections--and a fifth (or substrate) connection
on the rear of the cell.
The two vertical leads, one on the top and one on
the bottom of the cell, each yield a positive
voltage in proportion to the position of the center
of energy of the light spot. When these two
vertical signals are combined by the electronics, a
bipolar (±) DC voltage is produced. This voltage
is proportional to the vertical position of the
spot's center of energy in relation to the electrical
center of the cell. If both voltages are equal, the
center of the spot is located at the electrical center
of the cell. (Generally speaking, the electrical
center is located at the mechanical center of the
active area of the cell.) The same is also true for
the two horizontal leads.
Target resolution (for centering) is typically
.0001 in. (2.5 microns). The linear ranges for
single and dual axes vary with cell size. Angular
range for a four-axis target varies with the focal
length and application, from as much as 10
degrees to .5 degrees for the most sensitive
target.
Figure 45 - The Target Cell