No abstract

No abstract

A single-chip receiver for pulsed laser direct time-of-flight 3-D imaging applications has been realized in a 0.35-µm HV CMOS technology. The chip includes a 32 × 128 single-photon avalanche diode (SPAD) array [35% fill factor (FF)] and 257 time-to-digital converters (TDCs) with a ∼78-ps resolution. Two adjacent rows (2 × 128 SPADs) at a time can be selected for simultaneous measurement, i.e., 16 measurement cycles are needed to cover the whole array. SPADs are capable of operating in a gated mode in order to suppress dark and background light-induced detections. The IC was designed to be used in a solid-state 3-D imaging system with laser illumination concentrated in both time (short sub-ns pulses) and space (targeting only the active rows of the SPAD array). The performance of the receiver IC was characterized in a solid-state 3-D range imager with flood-pulsed illumination from a laser diode (LD)-based transmitter, which produced short [∼150ps full-width at half-maximum (FWHM)] high-energy (∼3.8-nJ pulse/∼14-W peak power) pulses at a pulsing rate of 250 kHz when operating at a wavelength of 810 nm. Two detector/TDC ICs formed an 8k pixel receiver, targeting a field-of-view of ∼42 • ×21 • by means of simple optics. Frame rates of up to 20 fps were demonstrated with a centimeter-level precision in the case of Lambertian targets within a range of 3.5 m. Index Terms-3-D imager, CMOS, direct time-of-flight (dTOF), single-photon avalanche diode (SPAD), solid state, time gating, time-to-digital converter (TDC).

An integrated receiver-TDC (time-to-digital converter) chip set is developed for pulsed time-of-flight (TOF) laser rangefinding. The receiver detects the current pulse from the optical detector and produces a timing mark for the TDC. The receiver uses time mode walk error compensation scheme achieving <+/-2.5 mm residual timing walk error within a dynamic range of ~1:40,000. The multi-channel TDC measures the time position, width and rise time of the echo pulses simultaneously with ~ 10 picosecond (ps) precision. Both chips are manufactured in 0.35-µm complementary metal-oxide semiconductor (CMOS) technology. The functionality of the chip set was demonstrated in a laser radar platform using 12 W and 3-ns optical pulses produced by a laser diode. A measurement accuracy of ~+/-3 mm was achieved with non-cooperative targets at a distance range of a few tens of metres within an amplitude range of received echoes of 1:40,000.

No abstract