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– frame exposure, integrating all pixels at a time in contrast to CMOS imager which typically integrate
line-by-line.
– short shutter time, to get sharp images.
– flash control output to have enough light for short time.
Scientific applications:
• long time exposure for low light conditions.
• optimizing image quality using the variable shutter control.
1.19.1.1.2 Details of operation
The process of getting an image from the CCD sensor can be separated into three different phases.
1.19.1.1.2.1 Trigger
When coming out of reset or ready with the last readout the CCD controller is waiting for a Trigger signal.
The following trigger modes are available:
Mode Description
Continuous Free running, no external trigger signal needed.
OnDemand Image acquisition triggered by command (software trigger).
OnLowLevel Start an exposure of a frame as long as the trigger input is below the trigger threshold.
OnHighLevel Start an exposure of a frame as long as the trigger input is above the trigger threshold.
OnFallingEdge Each falling edge of trigger signal acquires one image.
OnRisingEdge Each rising edge of trigger signal acquires one image.
OnHighExpose Each rising edge of trigger signal acquires one image, exposure time corresponds to pulse
width.
See also
For detailed description about the trigger modes ( https://www.matrix-vision/manuals/ [mv←-
IMPACT Acquire API])
• C: TCameraTriggerMode
• C++: mvIMPACT::acquire::TCameraTriggerMode
1.19.1.1.2.2 Exposure aka Integration
After an active trigger, the exposure phase starts with a maximum jitter of t
trig
. If flash illumination is enabled
in software the flash output will be activated exactly while the sensor chip is integrating light. Exposure time is
adjustable by software in increments of t
readline
.
1.19.1.1.2.3 Readout
When exposure is finished, the image is transferred to hidden storage cells on the CCD. Image data is then shifted
out line-by-line and transferred to memory. Shifting out non active lines takes tvshift, while shifting out active lines
will consume t
readline
. The number of active pixels per line will not have any impact on readout speed.
MATRIX VISION GmbH
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