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New iStar ICCD
Pre-Acquisition Setup - Image Intensifier
5.4.6 - Integrate on Chip (IoC)
IOC is a function that enables the image intensifier to be opened and closed a number of times while the CCD sensor
makes a single acquisition. Light signal passes through the intensifier while it is open (or switched on) and reaches the
CCD sensor. The CCD sensor accepts the light continuously for the entire duration of the acquisition while the intensifier
is opening and closing. Charges are built up on the sensor or ‘integrated’ until the acquisition is complete. Then all the
charges that have been built up are read out in the normal way.
IOC greatly improves the signal-to-noise ratio achievable, since the signal is being integrated on the sensor itself while
being read out once. Hence noise will only be generated from a single readout. The signal-to-noise ratio achieved while
operating the New iStar’s IOC function is better than that obtained while operating the system in accumulate acquisition
Mode. This is because during accumulate mode, the CCD is read out a number of times and accumulated in computer
memory. So the signal-to-noise ratio in this case will include noise generated from each read out that occurs.
This mode also allows to mimimize the CCD dark current contribution by filling up the CCD exposure time with multiple
useful signal contributions, further enhancing the overall signal-to-noise performance.
A checkbox, accessible on the
Gating
tab of the
Setup Acquisition
interface, allows the user to apply the Integrate On
Chip function and is only available in DDG gate mode.
IOC allows several gate pulses, as well as outputs A/B/C synchronization signals, to be generated within the CCD
exposure. When outputs A, B, or C are enabled, the first set of pulses is determined by the delay and width of these
outputs as set by the user. The delay applies from the rising edge of the Fire pulse for internal trigger or rising/falling
edge (user selected) for external trigger. This delay is in addition to the inherent insertion delay.
Once the first set of pulses is finished, subsequent sets are spaced out by the period/frequency pre-set in the IOC
section. Since subsequent sets cannot start before the first set is finished, the software automatically adjusts the period/
frequency according to the time from the start of the first pulse to the end of the last pulse. The start of the first pulse
could be the delay value in gater or output A/B/C, and the end of the last pulse could be the delay plus width of gater or
output A/B/C.
Please refer to the following page for detailed setting of these modes under different trigger conditions.
