Dalsa CALIBIR 640 GigE, Руководство пользователя

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36 • Features and Configuration Options Calibir 640 GigE IR Camera User's Manual
Defective Pixel Correction
The Calibir camera uses a defective pixel map to identify bad pixels in the sensor. These bad pixels
are replaced by the average value of neighboring valid pixels. The defective pixel map is a bitmap
file (.bmp) that uses two pixel values; 0 (black) indicates a good pixel, 255 (white) indicates a bad
pixel.
Figure 14: Defective Pixel Map
Two defective pixel maps are available: a factory calibrated set and a user-defined map. The
factory calibrated defective pixel map identifies defective pixels across the full range of ambient
operating temperatures (-40
o
C to +65
o
C).
For the user-defined map, automatic defective pixel detection is available. It adds pixels to the list
of defective pixels, in case some pixels become defective during the camera’s life after factory
initialization. It updates the user-defined map by launching a sequence that compares each pixel
value with the average value of its neighbors. Configurable parameters include the size of the
neighborhood window and the threshold uses to identify bad pixels (the number of standard
deviations from the average value) . To generate valid results, a uniform scene should be
presented to the camera (for example, a sheet of paper, or a cardboard box). Additionally, it can
help to adjust the lens completely out of focus.
Note that the automatic defective pixel detection only adds pixels to the list of defective pixels;
therefore it can be run at different ambient operating temperatures to identify pixels that do not
respond well at certain temperatures only. If invalid results are generated, the user-defined
defective pixel map can always be reinitialized from the factory defective pixel map.
Both the factory and user-defined pixel maps can be downloaded from or uploaded to the camera
using the file access functionality.
Related GigE Vision Features
Users can access the user defective pixel map to modify individual pixels in this map using the
features available in the Image Processing Category. Alternatively, an 8-bit .bmp image
representing the defective pixel map can be downloaded from or uploaded to the camera using the
File Access Control Category features.