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Piranha4 8K Camera Color User's Manual
03-032-20156-02
Teledyne DALSA
Spatial Correction and Bilinear Sensor Design
The Piranha4 bilinear color camera is based on Teledyne DALSA‘s bilinear CMOS sensor and designed such that
the first line of this two line sensor has red (R) and blue (B) alternating pixels, while the second line has all green
(G) pixels. The sensor has a 100% fill factor with zero gap between the two lines, which minimizes any artefact due
to spatial correction. The G channel can be used as a monochrome output.
Figure 5: Piranha4 Color Bilinear Sensor Block Diagram
Note:
The interpolation procedure does not work on the first and last pixels. As a result, the number of effective full
color (RGB) pixels is reduced by 2 to 8190 pixels.
There is no sp acing betw een the sensor lines. When the im age p asses the tw o lines of p ixels, the red / blu e
and green com p onents for the sam e im age location are cap tu red at a d ifferent tim e as d ictated by the line
sp acing. The cam era au tom atically corrects for the line sp acing to ensu re that the red / blu e and green
com p onents of the im age p ixel are all aligned w hen o u tp u t. H ow ever, this is only correct w hen the object
p ixel size is squ are; i.e., the d istance m oved by the object for one EXSYN C p eriod is equ al to the w id th of
the object pixel. In some ap plications it may not be possible to achieve a ‗squ are‘ object pixe l as fine
ad ju stm ent of the lens m agnification and / or the d istance m oved for each EXSYN C p eriod is not p ossible.
This scenario m ay be esp ecially ap p arent w hen trying to integrate the cam era into an existing system .
When it is not p ossible to generate a squ are object p ixel, color artefacts w ill occu r in the scan d irection
and is p articu larly noticeable at sharp ed ge transitions. The size of the ed ge artefact is p rop ortional to
how far the p ixel is from squ are. To correct for this, the cam era has a featu re , Line Sp atial Correction (or
three letter com m and ssa), w hich allow s fine ad ju stm ent of the com p ensation m echanism the cam era u ses
to correct for the line sp acing.
The d efau lt setting for this featu re is 1, w hich is set for squ are object p ixels. The sett ing can be ad ju sted
from 0 to 3 to com p ensate for rectangu lar p ixels
—
w hether they are too long or to short.
The follow ing exam p les of im age artefacts show black to w hite im age transitions and the associated
corrected im age after ap p lying a sp ecific ssa setting.
Red
Pixel 1
Green
Pixel 1
Blue
Pixel 2
Green
Pixel 2
Red
Pixel 3
Green
Pixel 3
Blue
Pixel 4
Green
Pixel 4
Red
Pixel 5
Green
Pixel 5
Blue
Pixel 6
Green
Pixel 6
Red
Pixel 7
Green
Pixel 7
Blue
Pixel 8
Green
Pixel 8
Red
Pixel
8191
Green
Pixel
8191
Blue
Pixel
8192
Green
Pixel
8192
Top Line
Bottom Line
