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Description of the data path
OSCAR Technical Manual V2.4.0
89
High SNR mode (High Signal Noise Ratio)
To configure this feature in an advanced register: See Table 101: Advanced
register: High Signal Noise Ratio (HSNR) on page 197.
In this mode the camera grabs and averages a set number of images and out-
puts one image with the same bit depth. This means that the camera will out-
put an 8 bit averaged image when an 8-bit image format is selected.
Because of the fact that normally uncorrelated (photon-, amplifier-) noise
dominates over correlated noise (fixed pattern noise), adding two images
will double (6 dB) the gray levels but only increase the noise levels by
(3 dB).
This enhances both the dynamic range as well as the signal to noise ratio.
Consequently adding 256 8-bit images will lead to a potential signal-to-noise
enhancement of 24 dB.
Figure 42: 2 out of 4 H+V sub-sampling (color)
Note
L
Changing sub-sampling modes involves the generation of new
shading reference images due to a change in the image size.
Note
L
• The averaged image is output at a lower frame rate
being exactly the fraction: fps/number of images.
• The camera must be in idle before turning this feature
on.
• The potential SNR enhancement may be lower when
using more than 8-bit original bit depth.
• Select 16-bit image format in order to take advantage
of the full potential SNR and DNR (DyNamic Range)
enhancements.
2 out of 4 H+V sub-sampling
2