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DCx Cameras
2.3.3 Color Filter (Bayer filter)
For technical reasons, digital image sensors can only detect brightness information, but no color information. To
produce color sensors, a color filter is applied to each photocell (pixel). The arrangement of the color filters is
illustrated in the following figure. Two out of every four pixels have a green filter, one pixel has a red filter and one
has a blue filter. This color distribution corresponds to the color sensitivity of the human eye, and is called the Bayer
filter pattern. With the help of the Bayer pattern the correct brightness and color information can be calculated for
each pixel. Full sensor resolution is retained.
Bayer conversion
A Bayer conversion, also referred to as de-Bayering, is carried out to determine the color information from the raw
sensor data (raw Bayer). By default all DCx Cameras transmit the image data to the PC in raw Bayer format. The
PC then uses the functions of the uc480 API to convert the image data to the color format you need for displaying
or further processing the data.
To convert the colors, a filter mask moves over the image and calculates a color value for each pixel from the
surrounding pixels. The uc480 API provides two filter masks that differ in image quality and CPU load.
Normal Quality (Mode IS_CONV_MODE_SOFTWARE_3x3/IS_CONV_MODE_HARDWARE_3x3)
A smaller filter mask is used for conversion. This algorithm has a low load on the CPU. The filter's averaging
function may cause a slight blur. Noise is reduced. This filter is recommended for image processing tasks.
High Quality (Mode IS_CONV_MODE_SOFTWARE_5x5)
A large filter mask is used for conversion. This algorithm offers very accurate color positioning and an increased
level of detail. The CPU load is higher than with the normal filter. This filter is recommended for visualization
applications.
Note
Software conversion with high quality should only be used for sensors whose green pixels have the same
sensitivity. This applies to the following sensors:
DCU223C / DCU224C
DCC1240C, DCC3240C
For all other sensors, we recommend using the standard filter mask.
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