Dalsa Piranha HS 4x-02K30, Руководство пользователя, Страница: 27 / 67

Piranha HS 4x User’s Manual 27
DALSA Corp. PRELIMINARY 03-32-10040-03
To return the average of multiple lines of video, use the command:
Syntax:
gla [ x1 ] [ x2 ]
Syntax Elements:
[ x1 ]
Optional parameter. This sets the start pixel to display on screen.
Allowable range is 1 to 2048. This value does not affect the Min,
Max, and Mean statistics generated at the end of the line output.
[ x2 ]
Optional parameter. This sets the end pixel to display on screen.
Allowable range is (
x1
+ 1) to 2048. This value does not affect the
Min, Max, and Mean statistics generated at the end of the line
output.
Notes:
•
If you do not specify a pixel range to display, the line output will
display all sensor pixels within the region of interest. The region of
interest (
roi
) command is described on page 25.
•
If you are using binning (
sbv 2
and/or
sbh 2
), the min, max, and
mean statistics are generated for every second pixel only.
•
Values returned are in DN.
Example:
gla 10 200
3.11 Calibrating the Camera
The Piranha HS 4x cameras have the ability to calibrate themselves in order to remove
non-uniformity in the image. 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 ) - digital offset) * 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).