Spectral Instruments Series 800, Руководство пользователя

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Spectral Instruments
Pt # 2500- 15
Spectral Instruments has designed a camera that is essentially bias-pattern-free
when it is operated from a suitable power source as directed in Section 2.3. If
that camera is mechanically connected to some apparatus that is at a different
ground potential than the power source, small currents flow through the camera
body. These small currents are always visible in the image; they are always
undesirable!
If the camera and the equipment cannot be grounded to the same point, it may be
necessary to introduce an electrical insulator (including screws) where the
camera physically is attached to your equipment.
1.2.5 TDI Operation
Spectral Instruments cameras can image in conjunction with a moving field. In
this mode the camera operates either through a timed delay or by synchronizing
the shifting of the image on the sensor to an external event. In the latter case, the
trigger input provides the synchronization. In TDI mode, a frame is discarded at
each end, which is overhead for this imaging mode.
1.2.6 Shutters And Timing Considerations
The camera provides millisecond resolution in timing your SICCD camera. That
resolution is useful when the camera is shuttered by equipment that responds in
tens of milliseconds.
The camera is also designed to obtain “images upon external signal”. This is
known as “triggered mode”. In this mode the camera is programmed to clear
charge continuously with the CCD staring into the application waiting for a
trigger event. The trigger event is provided by the application. The camera
ceases clearing immediately (within 5 milliseconds depending upon the CCD)
upon receipt of the trigger and stares into the application accumulating an image.
The camera stares for the currently set integration time and then it reads out.
When a SICCD camera is shuttered by any conventional multi- or twin-blade
shutter mechanism, the shutter requires some time to open and to close. These
shutter open and close delays must be considered when obtaining short
exposures. A user changeable shutter-close delay is programmed into the
exposure readout so readout does not start until the shutter is fully closed.
However, a good twin-blade shutter requires at least ten milliseconds to open as
well as close. A 10-millisecond exposure with such a shutter means that the
integration time is effectively 20 milliseconds for the center of the image and is
much less for the edge of the image. The resulting variation in effective
exposure is noticeable. The exact pattern observed depends upon the type of
shutter. In every instance, you must not expect uniformly exposed images when
the exposure times are within a factor of 10 of the shutter delay times. Large
shutters can take more than 50 milliseconds to open and close.