2D CMOS SPAD array techniques in 1D pulsed TOF distance measurement applications

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

L10, Linnanmaa, remote connection: https://oulu.zoom.us/j/63671806318

Topic of the dissertation

2D CMOS SPAD array techniques in 1D pulsed TOF distance measurement applications

Doctoral candidate

Master of Science in Technology Jaakko Huikari

Faculty and unit

University of Oulu Graduate School, Faculty of Information Technology and Electrical Engineering, Circuits and systems

Subject of study

Electronics design


Docent, Dr. Eng. Markku Åberg, VTT


Professor emeritus Juha Kostamovaara, University of Oulu

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2D CMOS SPAD array techniques in 1D pulsed TOF distance measurement applications

The goal of the research was to study the characteristics, performance and feasibility of a pulsed time-of-flight 1D laser radar system employing a 2D SPAD detector array in conjunction with a custom-made laser diode producing high energy and high-speed laser pulses. The research included the characterization and comparison of custom-made QW and bulk laser diodes operating in enhanced gain switching mode and producing laser pulses with a total energy of ~1–5 nJ and an FWHM of ~100 ps at pulsing rates >100 kHz. The receiver module was a purpose-built single-chip CMOS IC incorporating a 2D 9x9 SPAD array and a 10-channel TDC circuit enabling parallel SPAD-specific TOF measurements.

The key performance parameters of the laser radar system are intrinsic timing walk error ~5 cm (dynamic range ~1:100 000), linearity ± 0.5 mm, signal detection rate ~28% (target distance 34 m and reflectivity 11%) and precision ~2 cm. The total energy of a probe pulse was 0.6 nJ and the diameter of the circular receiver aperture ~20 mm. The selectable subarray feature of the receiver IC enables laser spot tracking on the detector array while maintaining a small effective field of view, thus reducing background radiation-induced noise detections, and offering prospect of walk error free measurement results. Detection time gating proved an effective means for signal-to-noise ratio improvement under conditions of high-level background radiation. Feasibility studies demonstrated high spatial accuracy of the system in practical settings when performing non-contact human heart rate measurement and when distinguishing individual free-falling snowflakes.

The implementation and performance of the 1D laser radar system demonstrated the viability of the proposed technology as an alternative along with a conventional laser radar operating in the linear detection mode for high performance, compact and cost-effective laser radar applications.
Last updated: 1.3.2023