Eclipse EC-11-xxx40, Руководство пользователя

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EC-11 User’s Manual
41
DALSA Corp. 03-32-00418-05
Note:
Parameters need to be specified for both forward and reverse direction in calibrated and uncalibrated
modes.
Calibrating Gains
To calibrate the analog gain, use the
calibrate_analog_gain
command. Values
range from 128 to 250DN and this function requires constant light input while executing.
This command sets gain in uncalibrated mode.
C9 Calibrating the Camera: Overview
This camera has the ability to calibrate itself in order to improve the FPN and PRNU
performance. This video correction operates on a pixel-by-pixel basis and implements a
two point correction for each pixel. This correction can reduce or eliminate image
distortion caused by the following factors:
•
Fixed Pattern Noise (FPN)
•
Photo Response Non Uniformity (PRNU)
•
Lens and light source non-uniformity
The two point correction is implemented such that for each pixel:
V
output
= (V
input
- FPN( pixel ) ) * PRNU(pixel)
where V
output
= digital output pixel value
V
input
= digital input pixel value from the CCD
PRNU( pixel) = PRNU correction coefficient for this pixel
FPN( pixel ) = FPN correction coefficient for this pixel
The calibration algorithm is performed in two steps. The fixed offset (FPN) is determined
first by performing a calibration without any light. This calibration determines exactly
how much offset to subtract per pixel in order to obtain flat output when the CCD is not
exposed.
The white light calibration is performed next to determine the multiplication factors
required to bring each pixel to the required value (balance target) for flat, white output.
Video output is set slightly above the brightest pixel (depending on offset subtracted).
For FPN (dark light) the value must be between 1DN and 127DN, for PRNU (white light)
the value must be between 128DN and 254DN. Use the
get_line
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 must be averaged out to ensure
proper sampling. Sample size is fixed at 128.
Dark Calibration
Dark calibration is used to remove the fixed analog offset from the video path. It is
recommended you repeat the calibration when a temperature change greater than 10°C
occurs.