![]() The multiple pixels of each aperture that correspond to a certain reproduced pixel are treated as a sub-pixel. In the proposed method, the multiple lenses are regarded as a synthetic single lens to collect more photons. The multi-aperture system is composed of multiple components for both lens and sensor. In this paper, the RTS noise and dark current reduction based on a multi-aperture imaging system with a selective averaging method is presented. However, the buried channel causes lower transconductance, which leads to larger thermal noise. Thus, the influence of traps near the interface is alleviated, so the 1/f and RTS noise can be reduced. The RTS noise can be reduced by the in-pixel buried channel source follower, in which an n-type doping along the channel of n-MOS transistor is introduced to lead the channel away from the Si-SiO 2 interface. As the transistor is scaled down, the impurity concentration in the channel becomes non-uniform, and large RTS noise will appear. The RTS noise in CISs is a major issue, especially in low-light applications. RTS noise is described as a fluctuation in the current of a MOSFET and it is generated by capturing and emission of carriers in the MOSFET channel randomly at the traps of the silicon-silicon dioxide interface. However, these high gain amplifiers are not useful for reducing the in-pixel random telegraph signal (RTS) noise and dark current white defects. High-gain amplifiers for reducing readout circuits noise and amplifiers with multiple sampling are effective for reducing thermal noise of readout circuits. In the last two decades, many methods have been presented for low-noise CIS design. Since the active pixel sensor (APS) with pinned photodiode technology was applied in CISs in the mid 1990's, the reset and dark current in CISs have been improved significantly. Especially in low-light applications, the sensor noise such as dark current white defects and amplifier noise becomes more visible. Noise is one of the crucial elements which limit the performance of CISs. Recently, CMOS image sensors (CISs) have become wildly used in scientific, industrial, and biomedical applications, as well as consumer cameras. Under a low-light condition, in which the maximum average signal is 11e - per aperture, the RTS noise and dark current white defects are removed and the peak signal-to-noise ratio (PSNR) of the image is increased by 6.3 dB. In the experiment, a prototype 3 × 3-aperture camera, where each aperture has 200 × 200 pixels and an imaging lens with a focal length of 3.0 mm and F-number of 3.0, is developed. It is verified by simulation that the effective noise normalized by optical gain in the peak of noise histogram is reduced from 1.38e - to 0.48e - in a 3 × 3-aperture system using low-noise CMOS image sensors based on folding-integration and cyclic column ADCs. In the multi-aperture imaging system, a very small synthetic F-number which is much smaller than 1.0 is achieved by increasing optical gain with multiple lenses. In this paper, a multi-aperture imaging system and selective averaging method which removes the RTS noise and the dark current white defects by minimizing the synthetic sensor noise at every pixel is proposed. In extremely low-light conditions, random telegraph signal (RTS) noise and dark current white defects become visible.
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