Dark Noise Cancellation - Basler L800k User Manual

Operation and Features

3.9.2 Dark Noise Cancellation

When the camera is used at very low line rates or with long idle times, a sensor characteristic
known as "dark current" causes extraneous charges to accumulate in the pixels during the time
between exposures. This accumulated charge can cause all of the lines captured at very low line
rates to be too bright or can cause the first few lines captured after a long idle period to be too
bright.
This dark noise effect is most noticeable when:
• You continuously operate the camera at a line rate lower than 1 kHz.
• The camera is idle for longer than 10 ms and then you begin to capture lines.
• You start out with a low line rate and then ramp up to a higher line rate.
cameras have a dark noise cancellation feature available. The dark noise cancellation
L800
k
feature will eliminate the effect caused by the accumulation of extraneous charges when operating
at very low line rates or with long idle times.
In edge-controlled mode, the dark noise cancellation feature has no effect on the
image because no time is present between exposures in edge-controlled mode.
The dark noise cancellation feature should only be used in level-controlled and pro-
grammable exposure time control mode.
As mentioned in Section 3.4.1.3, there is a slight delay in both the start and the end of exposure
when you are using an ExSync signal to control the camera. When the dark noise cancellation
feature is enabled, the exposure start delay and end delay are increased. The size of the exposure
start delay and end delay with the dark noise cancellation feature enabled depends on the camera
model and the exposure mode setting. Table 3-6 shows the exposure start delay and end delay
for each camera model and exposure mode combination when the dark noise cancellation feature
is enabled.
Exposure Mode
Level-controlled
Programmable
Exposure Mode
Level-controlled
Programmable
Exposure Mode
Level-controlled
Programmable
Table 3-6: Exposure Start and End Delays with the Dark Noise Cancellation Feature Enabled
3-30
Draft
L801 Start Delay
k
212.6 (+0.7/-0.0) µs
212.6 (+0.7/-0.0) µs
L802 Start Delay
k
106.3 (+0.5/-0.0) µs
106.3 (+0.5/-0.0) µs
L803 Start Delay
k
70.9 (+0.5/-0.0) µs
70.9 (+0.5/-0.0) µs
L801 End Delay
k
217.6 (+0.7/-0.0) µs
212.6 (+0.7/-0.0) µs
L802 End Delay
k
108.8 (+0.5/-0.0) µs
106.3 (+0.5/-0.0) µs
L803 End Delay
k
72.6 (+0.5/-0.0) µs
70.9 (+0.5/-0.0) µs
BASLER L800
k