Instruction manual

Description of the data path
8.2.1 IBIS5A multiple slope (High Dynamic Range mode)
ity.
The MF-131 sensor has a high dynamic range of about 60 dB. This can be extended to almost 100
dB by switching to a special mode.
This mode is called dual (in the case of rolling shutter) or multiple slope mode (in the case of
global shutter).
The following diagram, taken from FillFactory’s application notes, explains the functional
Figure 29: Multiple slope (high dynamic range) pixel charge as a function of time
The colored lines represent the analogue signal on the photodiode which decreases as a result of
exposure. The slope is determined by the amount of light at each pixel (the more light, the
steeper the slope). When the pixels reach the saturation level, the analogue signal will no longer
change despite further light exposure. As shown in the diagram, without any dual or multiple
slope pulse, pixels P3’ and P4’ reach saturation before the sample moment of the analogue
values.
When dual slope is enabled, a second reset pulse will be given (blue line) at a certain time before
the end of the integration time.
This dual slope reset pulse resets the analogue signal of the pixels below the dual slope reset
level to this level. After the reset, the analogue signal starts to decrease with the same slope as
before (pink P3 and yellow P4 lines).
This introduces a knee-point in the exposure function.
If the dual slope reset pulse is placed at the end of the integration time (90% for instance), the
analogue signal which would have normally reached the saturation level is no longer saturated at
read out. This effect increases the optical dynamic range of the sensor.
MARLIN Technical Manual
Page 54