Standard CMOS Image Sensor Research Articles

Simulation and design of a burst mode 20Mfps global shutter high conversion gain CMOS image sensor in a standard 180nm CMOS image sensor process using sequential transfer gates

A sequential transfer-gate and photodiode optimization method for CMOS Image sensors are described in this paper, which enables the design of large-scale ultra-high-speed burst mode CMOS Image sensors in a low-cost standard CMOS Image sensor process without the need for process customization or advanced process. The sequential transfer gates also show a clear advantage in minimizing the floating diffusion capacitance and improving image sensor conversion gain in large-scale pixels.

Time-of-flight imaging based on resonant photoelastic modulation.

A time-of-flight imaging system is proposed and its working principle demonstrated. To realize this system, a new device, a free-space optical mixer, is designed and fabricated. A scene is illuminated (flashed) with a megahertz-level amplitude-modulated light source, and the reflected light from the scene is collected by a receiver. The receiver consists of the free-space optical mixer, comprising a photoelastic modulator sandwiched between polarizers, placed in front of a standard complementary metal-oxide-semiconductor (CMOS) image sensor. This free-space optical mixer downconverts the megahertz-level amplitude modulation frequencies into the temporal bandwidth of the image sensor. A full-scale extension of the demonstrated system will be able to measure phases and Doppler shifts for the beat tones and use signal processing techniques to estimate the distance and velocity of each point in the illuminated scene with high accuracy.

Evaluation of size influence on performance figures of a single photon avalanche diode fabricated in a 180 nm standard CMOS technology

We present the performance characteristics of a single photon avalanche diode (SPAD) fabricated in a 180 nm standard CMOS image sensor technology. The SPAD structure was implemented in 8 different diameters between 5 and 40 μm to determine the influence of size variation on the SPAD performances in terms of dark count rate, afterpulsing, efficiency and time resolution. The measurements show a dark count rate below 10 kHz at 15 °C with a low afterpulsing probability (0.2 % at an excess bias of 300 mV), a good Photodetection efficiency (~20 %) and a very good time resolution (<70 ps FWHM at 450 nm) .