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4 Functionality
4.5 Reduction of Image Size
With Photonfocus cameras there are several possibilities to focus on the interesting parts of an
image, thus reducing the data rate and increasing the frame rate. The most commonly used
feature is Region of Interest (ROI).
4.5.1 Region of Interest (ROI)
Some applications do not need full image resolution. By reducing the image size to a certain
region of interest (ROI), the frame rate can be drastically increased. A region of interest can be
almost any rectangular window and is specified by its position within the full frame and its
width and height. Fig. 4.20 gives some possible configurations for a region of interest, and
Table 4.2 shows some numerical examples of how the frame rate can be increased by reducing
the ROI.
Only reductions in y-direction result in a higher frame rate. A reduction of the
ROI in x-direction reduces the amount of transferred data. The sensor read out
architecture limitates the possible ROI values in x-direction. In 8 tap output mode
settings modulo 8 are possible. In 10 tap output mode settings modulo 40 are
possible.
The software takes the user inputs and converts these values into allowed set-
tings. Due to the restrictions of the up- and down-buttons in the PFRemote
software the calculation procedure usually rounds off the user’s values. In case
of a user input, which is 1 number higher than an allowed value, the software
rounds up.
a )
b ) c ) d )
Figure 4.20: ROI configuration examples
ROI Dimension Frame rate
1280 x 1024 488 fps
1280 x 512 977 fps
1280 x 256 1953 fps
1280 x 128 3906 fps
1280 x 16 31250 fps
Table 4.2: Frame rates of different ROI settings (exposure time 10
µ
s; correction off, CFR off and simulta-
neous readout mode)
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