SVS-Vistek HR Series, Manual

Page: 22 / 102

SVS-VISTEK
Feature description 22
6.1.8 Color
Color cameras are identical to the monochrome versions. The color pixels
are transferred in sequence from the camera, in the same manner as the
monochrome, but considered as “raw”-format.
The camera sensor has a color mosaic filter called “Bayer” filter pattern
named after the person who invented it. The pattern alternates as follows:
E.g.: First line: GRGRGR... and so on. (R=red, B=blue, G=green)
Second line: BGBGBG... and so on. Please note that about half of the
pixels are green, a quarter red and a quarter blue. This is due to the
maximum sensitivity of the human eye at about 550 nm (green). De-
Bayering is not done in the camera, it has to be done in the client
software. See SDK functions as well. Not all sensors do have the same
sequence of color. The GenICam property P
I X E L
C
O L O R
F
I L T E R
does
indicate the sequence of the color pixels when reading color images.
Using color information from the neighboring pixels the RG and B values
of each pixel is interpolated by software. E.g. the red pixel does not have
information of green and blue components. The performance of the
image depends on the software used.
Camera Link frame grabber need information of the sequence order of
the colours. The order depends on sensor type. USB3 and GigE cameras
provide this in their XML file.
NOTICE
It is recommended to use an IR cut filter for color
applications
White Balance
The human eye adapts to the definition of white depending on the lighting
conditions. The human brain will define a surface as white, e.g. a sheet of
paper, even when it is illuminated with a bluish light.
White balance of a camera does the same. It defines white or removes
influences of a color based on a non-white illumination.
Figure 1: CCD with Bayer Pattern