3-D Range Imaging Using Stripe-Like Illumination and SPAD-Based Pulsed TOF Techniques

Abstract

A solid-state three-dimensional (3-D) range imager using the pulsed time-of-flight principle and a single photon avalanche diode (SPAD) based receiver is demonstrated. Contrary to conventional flood illumination, the suggested system uses sequentially scanned illumination stripes to increase the irradiance under the measured field of view and to reduce the receiver complexity. At equal average illumination power levels this approach increases the signal-to-noise ratio in the receiver enabling thus longer range and/or better performance in high background illumination conditions, albeit at the cost of lower transversal resolution. The transmitter uses eight sequentially driven laser diodes, each of which produces an optical pulse power, length and wavelength of ∼50 W, 2 ns and 905 nm, respectively at a pulse rate of ∼30 kHz so that the total effective pulsing rate is ∼250 kHz and the average illumination power is ∼30 mW. 3-D imaging is demonstrated outdoors in over 50 klux ambient lighting up to ∼10 m distance with 15 Hz frame rate and mm–cm level longitudinal precision in a field of view of about 40 × 10 degrees. The transversal resolution of the system is 16 × 128 pixels. The measurement results show 3-D measurement precision scaling according to the laser pulse width and averaging.

Keywords

• Laser radar
• LiDAR
• range imaging
• single photon detection