Spectral Instruments Series 800, User Manual, Page: 55 / 70

Spectral Instruments
Pt # 2500- 55
result from low-level instabilities in the external electrical environment
around the camera.
8.1.2.1 Shutter Problems
Shutters have a finite lifetime and should be considered as a regular service
item. One sign of shutter failure is smearing of bright image areas in the
direction away from the serial register. An image that contains discrete bright
spots will show streaking from the site of the bright spot toward high-
numbered rows. If the shutter is only beginning to fail the streaking may not
extend all of the way to the end of the image. Replace the shutter and see if
the problem goes away. Another shutter failure mode is not holding open.
This means that every exposure is too short. If the shutter “clicks” open and
then closes immediately, the shutter should be replaced.
8.1.2.2 General Streaking
These are patterns all over the image. They may be bands or they may be
limited to individual columns. Rows rarely streak. Sometimes herring bone
patterns march diagonally across the image and these are always related to
pickup of external signals during readout.
Remove the camera head from the application environment and isolate it
electrically from the application equipment. If the streaks are still visible,
ground loops are eliminated and something has changed in the camera head,
which must be returned for service. If the streaks go away there is an
extraneous low-level electrical circuit between the camera head and the
application that must be eliminated. Make certain that the AC electrical
connections are to a common power source.
8.1.2.3 Streaking In Triggered Images
Images obtained in response to triggered input usually are obtained from a
scintillating source. It is frequently the case that the scintillation persists for
some time after the “event” that stimulated the scintillation disappears. It is
necessary to wait for this persistent image to reduce to a negligible level
before the camera readout is started. Extending the exposure time for the
camera is usually the easiest method of delaying the readout. Changing the
shutter-close delay may also provide a suitable delay control.
8.1.3 Noisy Image
Noise indicates a signal intrusion into the application environment or a camera
failure. It is also usually due to something "running" in the application or to a
bad ground connection between the camera and the application.
8.1.3.1 Isolation And Detection
It is recommended that you consult with Spectral Instruments if you have a
noise pattern that is not cured by either plugging the computer, the camera