Image processing
Pearleye Technical Manual
V2.2.0
36
modules and the corresponding correction data is applied. Some modules may
also write back new data to the correction memory: But currently the modules
writhe back only to the SDRAM and not to the non-volatile flash memory.
The main correction modules are in detail:
•
Two-point correction
•
Background correction
•
Bad pixel correction
•
Drift compensation
•
Look-up table (LUT)
Two-point correction
With help of the
two-point correction
(likewise
gain offset correction
) the nor-
mally distinctive underground structure of the microbolometer sensor can be
equalized. The gain and the offset for each pixel of the input image can be
adapted to the set values on the basis of two reference images so that in the
optimum case no image structure is discernible.
Background correction
The
Pearleye P-007 LWIR
/
Pearleye P-030 LWIR
models feature an electrome-
chanical shutter. In conjunction with the background correction the image
quality can additionally be enhanced. The shutter is closed for a short time to
acquire a temporary background correction image. This image is subtracted
from the two-point corrected image data to reduce the remaining fixed pattern
noise.
Bad pixel correction
The
bad pixel correction
uses up to six non-false neighbour pixels to determine
an interpolated value from the neighbour pixels that replaces the bad pixel. In
this way the image appears without disturbing
hot
or
cold
pixels.
Drift compensation
As the temperature of the camera itself directly influences the output data, for
stable measurements it is necessary to compensate this drift. Therefore the cor-
rection module
drift compensation
can be used. It directly incorporates an
internally measured temperature into a drift correction function.
Look-up table (LUT)
The temperature characteristic curve of the microbolometer sensor usually is
not linear. With help of the
look-up table (LUT)
there is the possibility to lin-
earize the data at the end of the processing chain, so that more precise temper-
ature values are resulting.
