xiQ - Technical Manual Version 1.35
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Description of the multiple slope integration:
Phase 1
•
All pixels are integrated until they reach the defined saturation level of kneepoint1 (SL1).
•
If the saturation level of kneepoint1 is reached, the integration stops. SL1 is the maximum saturation level for all pixels in
this phase.
Phase 2
•
All pixels are integrated until they reach the defined saturation level of kneepoint2 (SL2).
•
If the saturation level of kneepoint2 is reached, the integration stops. SL2 is the maximum saturation level for all pixels in
this phase.
Phase 3
•
All pixels are integrated until the exposure time is reached. The pixel saturation may reach the maximum saturation level.
The main idea of this method is to reach an approx. logarithmic saturation curve. In order to achieve this goal phase2 always has
a smaller slope than phase1 and phase3 smaller than phase 2. Thus, the signal response during phase1 is higher as during
phase2. And the signal increase during phase2 is higher than during phase3.
As a result, darker pixels can be integrated during the complete integration time and the full sensor sensitivity can be exploited.
Brighter pixels are limited at the knee points and lose a part of their integration time.
figure 4-11, HDR - approx. logarithmic saturation curve
# of photons
ou
tp
ut
s
ig
na
l
100%
saturation level
knee point 1
knee point 2
