TM 1-6625-476-30
7-7
7-6. TEST DESCRIPTION. (CONT)
(2)
VIDEO AMPLITUDE TEST. Measure the peak-to-peak amplitude of the target video for
minimum value.
(3)
VIDEO SNR TEST. Measure the target signal-to-noise ratio.
(4)
CTF TEST. Contrast transfer function test. Measure the black-to-white response (contrast) at
certain frequencies and adjust as necessary.
d. RASTER GEOMETRY TESTS. These tests check the vidicon output for proper reproduction of target
video and check the boresight offset circuits.
(1)
RASTER ROTATION TEST. Measure the mechanical rotation of the vidicon and adjust if
necessary.
(2)
TEMPERATURE CONTROL TEST. Check the temperature control circuits on top of the
camera for proper operation and adjust if necessary.
(3)
HORIZONTAL SIZE TEST. Check the horizontal size potentiometers (full scan and underscan)
for proper adjustment to allow size markers generated by the camera to match markers generated by the
automatic test equipment.
(4)
VERTICAL SIZE TEST. Check the vertical size potentiometers (full scan and underscan) for
proper adjustment to allow size markers generated by the camera to match markers generated by the
automatic test equipment.
(5)
BORESIGHT AND SCALING TEST. Check the horizontal and vertical centering controls for
proper adjustment. Apply horizontal and vertical scaling voltages to the offset circuits of the camera to
allow measurement of camera offset.,
(6)
GEOMETRIC DISTORTION TEST. The crosshatch generator in the automatic test equipment
generates a test pattern that is superimposed over the target to allow measurement of distortion.
e. SIGNAL UNIFORMITY TESTS. Check the output video for absence of shading or blemishes.
(1)
SHADING TEST. Measure any shading in the output video produced by electronic circuits and
adjust it out.
(2)
BLEMISH TEST. Check certain zones on the face of the vidicon for blemishes of certain size,
amplitude, and color.
(3)
AFTER IMAGE TEST. Verify that no test pattern images are produced by the vidicon after test
pattern signals are removed. If any exist, an intense light will be generated over the entire vidicon screen
and gradually removed to cause any after-images to disappear.
