The Flash Window - Basler ace acA640-90gm User Manual

Image Acquisition Control
Setting the Shutter Mode
The camera's shutter has two operating modes: electronic rolling shutter mode and global reset
release mode. The shutter will operate in the electronic rolling shutter more whenever the global
reset release mode is disabled. When the global reset release mode is enabled, the shutter will
operate in global reset release mode.
You can enable and disable the global reset release mode for the rolling shutter from within your
application software by using the Basler pylon API. The following code snippet illustrates using the
API to enable and disable the global reset release mode:
// Enable the global reset release mode
Camera.GlobalResetReleaseModeEnable.SetValue( true );
// Disable the global reset release mode
Camera.GlobalResetReleaseModeEnable.SetValue( false );
You can also use the Basler pylon Viewer application to easily set the mode.
7.7.2.1

The Flash Window

Flash Window in Electronic Rolling Shutter Mode
If you are using the electronic rolling shutter mode, capturing images of moving objects requires the
use of flash exposure. If you don't use flash exposure when capturing images of moving objects,
the images will be distorted due to the temporal shift between the start of exposure for each line.
You can avoid distortion problems by using flash lighting and by applying the flash during the "flash
window" for each frame. The flash window is the period of time during a frame acquisition when all
of the lines in the sensor are open for exposure.
Figure 48 illustrates the flash window for the electronic rolling shutter mode.
You can calculate when the flash window will open (i.e., the time from the point where the frame is
triggered until the point where the window opens) using this formula:
Time to Flash Window Open = tRow x (AOI Height -1)
You can calculate the flash window width (i.e., how long the flash window will remain open) using
this formula:
Flash Window Width = Exposure Time Abs Parameter Setting - [ (tRow x (AOI Height -1) ]
For the acA2500-14gm/gc, tRow = 35 µs.
100 Basler ace GigE