Image sensors and optical devices

Which correctly describes the "conversion gain" of a CMOS image sensor?

  1. AThe output voltage per electron stored in the pixel (for example, µV/e⁻)
  2. BThe magnification of the lens
  3. CThe factor by which the pixel count is doubled
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Answer: A. The output voltage per electron stored in the pixel (for example, µV/e⁻)

Conversion gain expresses how much voltage change one signal electron produces when transferred to the floating diffusion (FD); it increases as the FD capacitance decreases. A higher conversion gain makes readout noise relatively less significant and improves low-light performance, but the number of electrons that can be handled (dynamic range) tends to shrink.

  • A. Correct. It is the voltage change per electron.
  • B. It is not the lens magnification.
  • C. It is unrelated to pixel count.
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