There has recently been a keen interest in developing Light Detection and Ranging (LiDAR) systems using Single Photon Avalanche Diode (SPAD) sensors. This has led to a variety of implementations in pixel combining techniques and Time to Digital Converter (TDC) architectures for such sensors. This paper presents a comparison of these approaches and demonstrates a technique capable of extending the range of LiDAR systems with improved resilience to background conditions. A LiDAR system emulator using a reconfigurable SPAD array and FPGA interface is used to compare these different techniques. A Monte Carlo simulation model leveraging synthetic 3D data is presented to visualize the sensor performance on realistic automotive LiDAR scenes. INDEX TERMS Light detection and ranging (LiDAR), macro-pixel, Monte Carlo simulation, single photon avalanche diode (SPAD), synthetic 3D data, time-of-flight (ToF), time to digital converter (TDC).

Large-format single-photon avalanche diode (SPAD) arrays often suffer from low fill-factors—the ratio of the active area to the overall pixel area. The detection efficiency of these detector arrays can be vastly increased with the integration of microlens arrays designed to concentrate incident light onto the active areas and may be refractive or diffractive in nature. The ability of diffractive optical elements (DOEs) to efficiently cover a square or rectangular pixel, combined with their capability of working as fast lenses (i.e., 3 ) makes them versatile and practical lens designs for use in sparse photon applications using microscale, large-format detector arrays. Binary-mask-based photolithography was employed to fabricate fast diffractive microlenses for two designs of 32 32 SPAD detector arrays, each design having a different pixel pitch and fill-factor. A spectral characterization of the lenses is performed, as well as analysis of performance under different illumination conditions from wide- to narrow-angle illumination (i.e., 2 to 22 optics). The performance of the microlenses presented exceeds previous designs in terms of both concentration factor (i.e., increase in light collection capability) and lens speed. Concentration factors greater than 33 are achieved for focal lengths in the substrate material as short as 190 , representing a microlens f-number of 3.8 and providing a focal spot diameter of 4 . These results were achieved while retaining an extremely high degree of performance uniformity across the 1024 devices in each case, which demonstrates the significant benefits to be gained by the implementation of DOEs as part of an integrated detector system using SPAD arrays with very small active areas.

Advanced complementary metal‐oxide semiconductor‐compatible single‐photon avalanche diode array technology is progressing rapidly and is being deployed in a wide range of applications. We report for the first time the use of a complementary metal‐oxide semiconductor‐compatible single‐photon avalanche diode array to perform detailed optical measurements on pixels of an organic light‐emitting diode microdisplay at very high sampling rate, very low light level, and over a very wide dynamic range of luminance. This offers a clear demonstration of the huge potential of this single‐photon avalanche diode technology to reveal hitherto obscure details of the optical characteristics of individual and groups of organic light‐emitting diode pixels.

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We report the development of a novel line-scanning microscope capable of acquiring high-speed time-correlated single-photon counting (TCSPC)-based fluorescence lifetime imaging microscopy (FLIM) imaging. The system consists of a laser-line focus, which is optically conjugated to a 1024 × 8 single-photon avalanche diode (SPAD)-based line-imaging complementary metal-oxide semiconductor (CMOS), with 23.78 µm pixel pitch at 49.31% fill factor. Incorporation of on-chip histogramming on the line-sensor enables acquisition rates 33 times faster than our previously reported bespoke high-speed FLIM platforms. We demonstrate the imaging capability of the high-speed FLIM platform in a number of biological applications.