Image data flow
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Goldeye G/CL Technical Manual V4.1.1
Image corrections
The corrections applied to the image are of special relevance within the Goldeye
camera. They are applied by the following modules.
•
Non-uniformity correction (NUC)
•
Background correction (BC)
•
Defect pixel correction (DPC)
The corrections need special correction data that must be provided prior to
operating the image processing chain.
Determination and storage of correction data
For each individual camera, specific correction data is determined during the
manufacturing process. All necessary correction data is stored within the camera‘s
non-volatile flash memory ex works.
During camera start-up, the available correction data is copied from the flash
memory onto the correction data memory for real time access.
From the correction data memory, the correction data is transferred to the
individual correction modules. The correction data transfer is synchronized with
the transfer of image data from the sensor. A correction module may also write
back to the correction data memory, depending on its functionality.
The IR specific image correction modules are described in detail below.
Non-uniformity correction (NUC)
Every pixel of an InGaAs sensor possesses its individual amount of dark signal (dark
signal non-uniformity, DSNU) and an individual sensitivity for light (photo response
non-uniformity, PRNU). Thus, while exposing, each sensor creates a specific, non-
uniform underlying pattern. This pattern can be compensated with help of the
non-uniformity correction.
To correct the non-uniformity, correction values for gain and offset of each pixel
are determined based on multiple reference images and applied to the actual
image. Ideally, after correction no image structure is recognizable.
However, there are various conditions that influence the image quality:
•
analog gain setting
•
sensor temperature
•
exposure time
These conditions need corresponding correction data for best correction quality.
Thus, the camera contains several data sets for a range of conditions.
