Spectral Instruments Series 800, Руководство пользователя

Страница: 54 / 70

Spectral Instruments
Pt # 2500- 54
than 2000 units and no image appears, it is probably not an analog offset
problem.
The next most frequent cause of an all 0 image is over saturation of the
CCD or the analog processor. Cover up the camera front end. If the
“zeros” persist the problem is in the camera electronics unit. If a normal
bias is recorded then the problem is in the camera head and the CCD is
overloaded. Try short exposures or somehow reduce the light level to
relieve the overload.
8.1.1.2 Just A Bias
“Only a bias” image implies that the video signal from the camera head has
disappeared. If the camera has been operating properly and suddenly
ceases to produce images it is important to look at “what has changed”. If
the camera was moved or anything was disconnected, check that the camera
has been properly reinstalled.
Next, it is necessary to make certain that the problem is in the camera. If
the camera is warm obtain a 30-second dark. If it is cold, obtain a 5-minute
dark. Either image will exhibit the characteristic pattern of a dark image
from a CCD camera if the CCD and the electronics are working. If the
image is still very flat without any gradients or bright spots then the CCD is
truly not providing image data. This means that the camera must be
returned for service.
If a normal dark image is observed, check the application interface to see if
the source of illumination is blocked or not enabled somehow, because the
camera is working. Look for an inoperative shutter.
8.1.1.3 Fully Saturated Image
The light from even a darkened room is enough to saturate the CCD.
Again, cover the front of the camera and determine whether the saturated
condition persists.
Sometimes it is not so easy to darken the incoming signal but it is
important to make certain that the camera is not exposed to extraneous light
that is “leaking” into the camera head. Attempt to darken the incoming
light path and obtain a two-minute dark image. If the saturated condition
persists it is necessary to remove the camera head from the application and
cover it completely with a dark shroud and repeat the dark image. If the
saturated condition persists the camera head has failed and must be
returned for service.
8.1.2 Streaks In The Image
Streaks occur in numerous forms. The most common source of streaks is the
shutter failing to close fully before the image starts shifting. Some streaks