Teledyne Princeton Instruments PI-MAX 3, System Manual

Page: 239 / 250

Appendix H Glossary 239
Frame Rate (fps):
The number of frames that can be readout per second. The
effective frame rate can be increased by defining a Region of
Interest (ROI) that is smaller than the full-frame size. This means
that a selected portion of the image can be displayed and the
remainder of the accumulated charge discarded. The frame rate
generally increases with reduction in the size of the detected
area. For example, a CCD with a sensor size of 1000 x 1000 and
an output rate of ten frames/second can produce 100
frames/second if the read-out region is reduced to 100 x 100
pixels.
Full-Well
Capacity:
The number of electrons that can be stored in a pixel. The smaller
the pixel, the fewer electrons can be stored; therefore, either the
exposure times need to be shorter or the signal intensity must be
lower. Note that binning relies on the full-well capacity of the
pixels in the serial shift register and of the output node. Typically,
a serial shift register pixel has a full-well capacity that is 2 times
greater than that of an image pixel and the output node has a
full-well capacity that is about 1.5-2 times greater than that of a
serial register pixel.
Filmless Gen III
Intensifier:
Filmless Gen III intensifier devices use GaAsP photocathodes
which have no ion barrier film (MCP).
Gen III filmless intensifiers offer ultra-fast gating as well as >50%
QE for the best combination of sensitivity in the visible region
(<780 nm) and gate speed.
FWHM:
Full Width Half-Maximum. Time period from the mid-point of the
leading edge to the mid-point of the trailing edge of the gate
pulse. Used to describe pulse width.
Gate Delay:
The time between the beginning of the trigger pulse (either
internal or external) and the beginning of the photocathode gate
pulse.
Gate Mode:
PI-MAX3 intensifier mode in which the photocathode is biased on
only for the time that each gate pulse is applied. In this way, the
array can be exposed to multiple images during a single exposure
time. As a result, the tolerance to room light is higher in gated
operation, but the risk of damaging overload from intense light
sources such as lasers remains. In fact, intense light sources in
gated experiments can cause spot damage that would be
undetected by the alarm circuit.
Gate Width:
The time during which light will be detected by the intensifier,
intensified, and applied to the CCD. Basically, the intensifier
controls what the chip sees during the exposure time. For signal
to be detected, it must both fall in a valid gate width and in a valid
exposure time.