A 64×64 Gated-SPAD Image Sensor With 2-D and 3-D Imaging Using a Time-Domain Sampling Histogram

A proof-of-concept prototype is presented, which can be used for 2-D and 3-D imaging with a resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$64\times 64$ </tex-math></inline-formula>, and it consists of a 110-nm complementary metal oxide semiconductor (CMOS) sensor chip, a gated high-voltage driver circuit, and an additional field-programmable gate array (FPGA) to perform the digital signal processing (DSP), and a laser driver circuit. The sensor chip consists single-photon avalanche diode (SPAD) array with a resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$64\times 8$ </tex-math></inline-formula>, 512 passive quenching circuits, 64 time-to-digital converter (TDC) with 160-ps resolution and 80-ns dynamic range, and readout circuits. The gated high-voltage driver circuit is used to control the working time of the SPAD, which can improve background noise suppression capability, linearity of 2-D imaging, and extend the dynamic range of the sensor chip. The DSP contains the partial histograms based on time-domain sampling algorithm, the histogram-based 2-D imaging algorithm, the backpropagation (BP) neural network filter, and the nonlinear fitting algorithm. Compared with traditional partial histograms, partial histograms based on a time-domain sampling algorithm can further reduce the utilization of logical unit resources of the histogram and improve the signal-to-noise ratio (SNR) of coarse histograms. The proposed histogram-based 2-D imaging algorithm can improve linearity and reduce the in-pixel counter compared with traditional 2-D imaging technology. The extensive experiments show that measurement distance, measurement accuracy, and frame rate are 64 m, 20 cm, and 10 Hz at 2 klux, respectively. When the background light is increased to 100 klux, the effective measurement distance is reduced to 8 m. In 2-D imaging, SPAD receives more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 10^{6}$ </tex-math></inline-formula> photons/s without distortion.