High-speed wide dynamic range linear mode time-of-flight receiver based on zero-crossing timing detection

Aram Baharmast,Juha Kostamovaara

doi:10.1117/1.oe.59.10.104102

Aram Baharmast, Juha Kostamovaara

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https://doi.org/10.1117/1.oe.59.10.104102

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Journal: Optical Engineering	Publication Date: Oct 14, 2020
Citations: 4	License type: cc-by

Affiliation: University of Oulu

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We present an accurate laser radar receiver with a wide dynamic range intended for ranging applications based on an event-based approach, in which a receiver-time-to-digital converter is used to extract the timing information from the reflected echo. The receiver is based on LC resonance pulse shaping at the input so that the unipolar pulse detected by the avalanche photodiode is converted to a bipolar signal, and the first zero-crossing of this converted signal is marked as the only timing point. One important aspect of the proposed scheme is that it does not need any postcompensation or gain control for achieving a wide dynamic range. The receiver chip was fabricated in a 0.35-μm standard CMOS technology, and a laser radar platform was developed to verify the functionality of the proposed receiver channel. The measured accuracy of the receiver is ±3.5 cm within a dynamic range of more than 1:250,000 using 3-ns FWHM pulses when target materials with different reflectivities are used in the measurements. The single-shot precision of the receiver (σ value) is ∼5 cm for a minimum SNR of ∼10.

Highlights

Laser ranging devices have many well-established applications in industry, traffic control, farming, geodesy, and airborne laser scanning.[1,2,3] Nowadays, these devices are even more attractive due to their important role in self-driving cars, drones, consumer electronics, robotics, and gesture control, for example.[4,5,6]Optical time-of-flight (TOF) laser ranging devices can be characterized as either direct or indirect,[7,8] with both techniques employed in a wide variety of applications
In iTOF method, an amplitude-modulated light carrier is emitted to the target, and the distance is resolved from the phase difference between the transmitted and received signal echoes. This technique can achieve a high level of accuracy in short-range applications,[9] but it suffers from a limited unambiguous measurement range, which is directly dependent on the modulation frequency employed (Rmax 1⁄4 c∕2 f, where c is the speed of light and f is the modulation frequency), which is typically in the range 10 to 100 MHz.[10,11]
We have proposed a new implementation of unipolar-to-bipolar pulse shaping, in which an LC resonator is combined with a nonlinear shunt feedback transimpedance amplifier (TIA) at the input to the receiver channel

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Introduction

Laser ranging devices have many well-established applications in industry, traffic control, farming, geodesy, and airborne laser scanning.[1,2,3] Nowadays, these devices are even more attractive due to their important role in self-driving cars, drones, consumer electronics (games), robotics, and gesture control, for example.[4,5,6]Optical time-of-flight (TOF) laser ranging devices can be characterized as either direct or indirect (iTOF versus dTOF),[7,8] with both techniques employed in a wide variety of applications. In this method, the optical power of the laser can be concentrated into the moment of timing (contrary to modulated continuous emission) so that cm-level (or even mm level) precision can be achieved even in a single measurement.[11,13,14] Here, dTOF approach is followed

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