H. Imaging Demonstration
Based on the measured performance, the presented imager
is supposed to operate in both low light and normal light conditions.
In order to validate this idea, images were taken using
the presented image sensor in a dark room with a controlled
level of light. The imager was set with an exposure time of
12ms and a frame rate of 84 fps. Fig. 18(a) and (b) show
images taken with the chip under different low light levels
using the ×64 column gain mode at light levels of 0.005 lux
and 0.066 lux corresponding to an average of 3 and 41 photogenerated
electrons per pixel, respectively. In Fig. 18(a), the
SNR of the input light (limited by the photon shot noise) is
below 5 dB. The dominant noise sources are the photon shot
noise and the temporal read noise. One can see that even with
such a low input light, the objects in the scene can still be
distinguished. In Fig. 18(b), the SNR of the input light is
about 16 dB. Due to the high column gain, one can see that the
image is not far from saturation due to voltage swing of the
column-level amplifier. In these conditions, the photon shot
noise and fixed pattern noise are supposed to be the dominant
noise sources. Fig. 18(c) shows an image obtained at a light
level of 0.5 lux corresponding to an average of 320 photogenerated
electrons per pixel and the column-level gain set
to 1. Here the input SNR is about 25 dB.