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Functions and Operations
A typical CCD camera does not use the full dynamic range due to the nominal gain and the output specification such as RS-170. The typical CCD camera’s gain is set at 16 to 22 dB and the RS-170 video level is 714 mV. Using 20 dB gain for the calculation, CCD output is limited to 714/10 = 71.4 mV. Since the CCD’s saturation voltage is 400 mV to 500 mV, it uses less than 1/5 of the full dynamic range.
Machine vision and outdoor applications, cannot afford to miss image information behind the saturation, which is why the dynamic range adaptation is critical.
6.5.1Programmable Look-Up Table (LUT) and Knee Control
The TM-4200CL has a built-in LUT (look-up table) for dynamic range control.
At a specific gain setting, the offset (minimum level.... dark point) and A/D reference top voltage
(maximum level... saturation point) are set to 12-bit A/D input so that the full dynamic range of the CCD is utilized at 12-bit references as the input and the LUT output is converted into either 8-bit or 10- bit to adjust the gamma correction. There is no 12-bit LUT.
The look-up table has two knee points (variable gamma selection) that allow the 10-bit input to be segmented into three regions. The look-up table selection can be made by knee curve direct input.
TM/TMC-4200CL Series Progressive Scan Cameras
