Precautions When Using The Ccd - Hamamatsu Photonics C9100-02 Instruction Manual

10. PRECAUTIONS WHEN USING THE CCD

C9100 uses a CCD. Read the following points regarding handling of the CCD carefully.
(1) White spots
During long exposure times, imperfection in the CCD's silicon wafer cause white
spots to be generated on the image. As of the present time, there is no workaround
for this phenomenon. Certain CCD temperature characteristics can cause these
white spots to multiple in relation to exposure time, but using dark subtraction* can
compensate for this phenomenon. Atomic ray may generate white spot.
*
After acquiring an image using an arbitrary exposure time, the CCD is placed in a dark state for an equal amount of
time, and reacquires the image without any light exposure. Subsequently, the second image is subtracted from the
first, canceling dark-area information from the original image.
(2) Smear
When imaging very bright objects, bright vertical stripes (vertical smear) may be
visible in the images being taken. This is due to the incident light while transferring
the electrons from sensor part to memory part. The amount of smear is dependent
on (the ratio between) readout time and exposure time. Smear tends to appear more
strongly at shorter exposure time to readout time.
Impact from smear is just a little for the camera in normal mode and frame blanking
mode, but sometimes it is observed when exposure time is shortened to readout
time in external control mode.
(3) Folding distortion
A rough-edged flicker may be visible when imaging striped patterns, lines, and
similar subject matter.
(4) Interference fringes pattern
Coherent light such as LASER light may generate interference fringes pattern on
image.
(5) Electron Multiplier gain (EM gain)
Start the measurement after the inside cooling temperature becomes stable because
the Electron Multiplier gain depends on the temperature. The inside cooling
temperature usually becomes stable after approximately 30 minuets.
When the EM gain is set higher, a part of output signal might show zero. When it is
not good for the measurement, please use with the higher offset level.
(6) EM gain degradation
In order to maintain proper camera performance do not expose the CCD chip to
excessive incident light or excessive EM gain. Turn off power when the C-mount is
exchanged or incident light levels are too high.
This CCD chip has the following characteristics:
1) Higher EM gain creates greater EM gain shift down while maintaining the same
incident light level.
2) Higher incident light levels create greater EM gain shift down while maintaining
the same EM gain setting.
C9100-02 Ver.1.7
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