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4 Image Acquisition
4.5 Overlapped Image Acquisition Timing
The camera is able to perform an overlapped image acquisition. It means, a new exposure can
be started during the image readout of the previous image. Fig. 4.10 shows an image
acquisition procedure when images are captured in overlapped mode. The status "Frame
Active" remains active during the acquisition of the three frames since there is no gap between
two frames. The "Frame Trigger Wait" is asserted during the frame read out in order to
indicate, that a new exposure can be started.
All examples in the previous sections show a non overlapping frame timing. A new frame is
always started after the previous image read out has been finished. All these examples work
also in the overlap mode. It doesn’t show the overlap mode in order to simplify the diagrams.
The overlapped image acquisition is not available, when the triggered controlled
exposure mode is configured.
E x p o s u r e 1 R e a d O u t 1
F r a m e 1
E x p o s u r e 2 R e a d O u t 2
F r a m e 2
E x p o s u r e N R e a d O u t N
F r a m e N
A c q u i s i t i o n A c t i v e
A c q u i s i t i o n S t a r t
T r i g g e r 1
A c q u i s i t i o n E n d
T r i g g e r 1
F r a m e S t a r t
T r i g g e r 1
F r a m e S t a r t
T r i g g e r 2
F r a m e S t a r t
T r i g g e r N
F r a m e
T r i g g e r
W a i t F r a m e
T r i g g e r
W a i t F r a m e
T r i g g e r
W a i t
A c q u s i t i o n
T r i g g e r
W a i t A c q u s i t i o n
T r i g g e r
W a i t
A c q u i s i t i o n S t a r t ( ) A c q u i s i t i o n S t o p ( )
F r a m e A c t i v e
F r a m e
T r i g g e r
W a i t
Figure 4.10: Overlapped Image acquisition Timing
There is a restriction of the overlapped image acquisition: The exposure time of the current
frame must not end prior to the end of the read out of the previous frame. Two different
timing situation needs to be distinguished:
Exposure Time > Read Out Time An new exposure cycle can be started as soon as the read out
of the previous frame has been started (See Fig. 4.11).
Exposure Time < Read Out Time
The start of a new exposure has to be delayed by a certain
amount of time in order to ensure, that the exposure doesn’t end prior to the image read
out end of the previous frame (See Fig. 4.12).
The camera adjusts the timing automatically, and ensures that it complies with this restriction.
Frame start or frame burst start triggers which arrive too early and which violates the
overlapping restriction, will be ignored by the camera and indicated by a missed trigger event,
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