Dalsa Piranha HS 4x-02K30, User Manual, Page: 28 / 67

28 Piranha HS 4x User’s Manual
03-32-10040-03 PRELIMINARY DALSA Corp.
For FPN (dark light) the value of all pixels should be between 1DN and 127DN. For
PRNU (white light) the recommended value is between 64DN and 254DN. Use the
gl
command to ensure the proper input to the digital processing, V
input
.
White light calibration will gain up to maximum white light pixel plus the maximum
FPN subtract pixel.
When performing any camera calibration, random noise is minimized by averaging out
up to 64 lines of valid data. To adjust the sample line size, use the
css i
command,
where
i
is 16, 32, 64 (factory setting). A lower value reduces the camera’s calibration time,
at the expense of increased coefficient error.
Calibration Steps Overview
1. Set up the camera operating environment (i.e. line rate, exposure,etc.)
2. Perform all analog and digital adjustments described in section 3.11.1 on page 30.
3. Make sure there are suitable calibration targets. The target to calibrate should be a flat
field, e.g. plastic or ceramic for white calibration.
4. Set the calibration sample size using the command
css
(see Returning Multiple Lines
of Video page 26).
5. Perform Dark (FPN) calibration (see Dark Calibration on page 28).
6. Perform White (PRNU) calibration (see White Light Calibration on page 29).
7. Save settings and pixel coefficients using the commands
wus
and
wpc
.
Note: It is important to do the FPN calibration first. Results of the FPN calibration are
used in the PRNU procedure. We recommend that you repeat the calibration when a
temperature change greater than 10°C occurs.
Dark Calibration
Dark calibration is used to remove the fixed analog offset from the video path. It is
recommended that you repeat the calibration when a temperature change greater than
10°C occurs.
To perform dark calibration:
1. Stop all light from entering the camera. (Tip: cover lens with a lens cap.)
2. Verify that output signal level is within range by issuing the command
gl
or
gla
(recommended range is 1-127). If the signal level is too low, adjust the analog offset
( sao ) . If the signal level is too high, ensure that no light is entering the camera, reduce the
analog offset or reduce the gain level (
sg
) .
3. Issue the command
ccf
. The camera will respond with OK> if no error occurs. Dark
calibration automatically calibrates FPN coefficients and digital offset.
To perform a dark calibration with an analog offset value:
Use the ccf
[
i ] command, where
i
is the analog offset DN. When the optional parameter
is provided, this command sets the analog offset first to
i
before calculating the FPN
coefficients range from 1 to 100DN for 8-bit data mode, and 4 to 400DN for 10-bit data mode
for the specified region of interest. If value is left blank, current offset values are used.