Spectral Instruments Series 800, User Manual, Page: 10 / 70

Spectral Instruments
Pt # 2500- 10
1.1.3 Cooling The CCD - Why
SICCD cameras are cooled to reduce the image contaminant called dark signal.
Images accrue this unwanted signal at a rate that decreases as the temperature of
the CCD is lowered. It is not the dark signal that is the problem (it could be
subtracted from the image), it is the noise associated with the dark signal. That
noise cannot be subtracted; it must be prevented.
The S800 camera system employs a thermoelectric cooler that is capable of
lowering the temperature of a typical CCD to -40
o
C. The heat from the hot side
of the TEC is removed by a liquid heat exchanger that is connected to the camera
head. As long as the temperature of the camera is not reduced below the local
dew point, it is possible to lower the operating temperature of the CCD by using
chilled water in the heat exchanger rather than water at room-air temperature.
1.1.4 Sensitivity Of The Camera
SICCD cameras are designed to “see in the dark”. They do so quite well. You
can’t permanently hurt your camera by exposing it to too much light although, if
you have done so, it will affect your ability to make precise measurements of low
light level scenes until after you have warmed up the camera and then cooled it
back down again.
Dark images are a good way to find out how much light is leaking into your
equipment. An image obtained with no external light coming through the normal
path provides a view of how much light is coming from extra-normal paths. This
camera can see light leaks very well! To realize the full potential of your SICCD
camera, it, and the equipment to which it is attached, must be light tight.
1.2 The S800 Camera
The camera is shown in profile in Figure 3. In this view, the position of the CCD
relative to the front flange, or plate, of the camera is shown. Also shown are the
overall dimensions of the camera. The camera back-view is shown in Figure 4.
Several different connections are required to integrate the camera into your
application. The dimensions are all millimeters.
Power is provided through a 14-pin twist-lock connector. The DC voltages to
operate the camera are supplied at this connector. The source of power may be a
Spectral Instruments S800 rack mount power supply or a DC source in your
application (typically through a DC - to - DC converter package supplied by
Spectral). In either case, a power sub-system is an integral part of a S800
camera. Connection to the computer is either through a 50-pin sub-miniature D
(looks like a SCSI) connector (as shown in Figure 4.) or by a MT-RJ type of fiber
optic data and communication connector.
The computer interface module will have a matching connector. Adapters are
available that split the twin MT-RJ fiber pair into two ST type of fibers. The
dual ST to MT-RJ combining equivalent is also available for use at the data
interface card. The data rate is limited to a maximum of 4,000,000 pixels per