Operation
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RM/TM-2040GE Series
All AccuPiXEL color cameras are carefully designed for maximum color performance. JAI Inc. strongly suggests
that you use digital output for the best performance.
Some software is used on board (FPGA or DSP) to perform the interpolation. Other software simply uses the
host computer’s memory and CPU. The processing speed may vary depending on the architecture and speed of
the computer.
3.3
Dynamic Range Control
Figure 11.
Output and Blooming
The typical interline transfer CCD has fixed noise levels based on dark current (thermal or KT noise), pattern
noise, and the operating clock speed. In general, the level of the 20 MHz pixel clock CCD at room temperature
is around 20 to 50 electrons. The maximum capacity of CCD charges is limited by the well capacity at
saturation. The range is limited by the structure and the pixel size.
The TM-2040GE uses a CCD with 7.4 µm x 7.4 µm pixels and a two-phase vertical shift register structure. The
well capacity is 40,000 electrons. The theoretical dynamic range is 40,000:30 = 1333:1 (60 dB).
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.
3.3.1
Programmable Look-Up Table (LUT) and Knee Control
The TM-2040GE 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.
Summary of Contents for RM-2040GE Series
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