Abstract
A pulsed TOF laser radar utilizing the single-photon detection mode has been implemented, and its performance is characterized. The transmitter employs a QW double-heterostructure laser diode producing 0.6 nJ/100 ps laser pulses at a central wavelength of ∼810 nm. The detector is a single-chip IC manufactured in the standard 0.35-μm HV CMOS process, including a 9×9 single-photon avalanche diode (SPAD) array and a 10-channel time-to-digital converter (TDC) circuit. Both the SPAD array and the TDC circuit support a time gating feature allowing photon detection to occur only within a predefined time window. The SPAD array also supports a 3×3 SPADs subarray selection feature to respond to the laser spot wandering effect due to the paraxial optics and to reduce background radiation-induced detections. The characterization results demonstrate a distance measurement accuracy of +/−0.5 mm to a target at 34 m having 11% reflectivity. The signal detection rate is 28% at a laser pulsing rate of 100 kHz. The single-shot precision of the laser radar is ∼20 mm (FWHM). The deteriorating impact of high-level background radiation conditions on the SNR is demonstrated, as also is a scheme to improve this by means of detector time gating.
Highlights
Time-of-flight (TOF) laser radar techniques have been widely used for distance measurement applications such as the measurement of material levels in containers, profiling and scanning of objects, traffic safety applications such as collision avoidance, speed measurement, and traffic control, and positioning, surveying, and docking
The transit time of a short laser pulse from the transmitter to the object and back to the receiver is measured with a time-to-digital converter, and the target distance is calculated from this based on the known speed of light
The operating principle of the to-digital converter (TDC) is based on a counter and two interpolators, and its purpose is to measure the time intervals between the start signal generated by a laser drive current pulse and the nine separate stop signals induced by single-photon avalanche diode (SPAD) triggering
Summary
Time-of-flight (TOF) laser radar techniques have been widely used for distance measurement applications such as the measurement of material levels in containers, profiling and scanning of objects, traffic safety applications such as collision avoidance, speed measurement, and traffic control, and positioning, surveying, and docking. Since the single-shot precision is determined by the laser pulse width as a first-order approximation, this width is reduced from the value of 3 to 4 ns (FWHM), which is typically used in pulsed TOF laser radars to ∼100 ps This pulse is produced at a relatively high-energy level (∼0.6 nJ), with a specially designed quantum well double heterostructure (QW DH) laser diode with enhanced gain switching.[11,12]. The large area and electrical configurability of the detector can be utilized in minimizing the timing walk error, by acquiring TOF information only from those SPAD elements operating in the singlephoton mode This construction reduces the accuracy of the tolerances in the mechanical adjustments of the laser radar system.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
