Custom-Technology Single-Photon Avalanche Diode Linear Detector Array for Underwater Depth Imaging

Aurora Maccarone,Ivan Rech,Gerald S Buller,Darryl Newborough,Ivan Labanca,Giulia Acconcia,Ulrich Steinlehner

doi:10.3390/s21144850

Abstract

We present an optical depth imaging system suitable for highly scattering underwater environments. The system used the time-correlated single-photon counting (TCSPC) technique and the time-of-flight approach to obtain depth profiles. The single-photon detection was provided by a linear array of single-photon avalanche diode (SPAD) detectors fabricated in a customized silicon fabrication technology for optimized efficiency, dark count rate, and jitter performance. The bi-static transceiver comprised a pulsed laser diode source with central wavelength 670 nm, a linear array of 16 × 1 Si-SPAD detectors, with a dedicated TCSPC acquisition module. Cylindrical lenses were used to collect the light scattered by the target and image it onto the sensor. These laboratory-based experiments demonstrated single-photon depth imaging at a range of 1.65 m in highly scattering conditions, equivalent up to 8.3 attenuation lengths between the system and the target, using average optical powers of up to 15 mW. The depth and spatial resolution of this sensor were investigated in different scattering conditions.

Highlights

When this scanning technique is used with the triangulation approach, the advantage is improved depth resolution when compared with time-of-flight sensors at short ranges [8]; the main challenge is the calibration process to obtain the correct geometrical parameters of the system [9,10]
We investigate a Si-single-photon avalanche diode (SPAD) detector array fabricated in custom technology optimized for underwater three-dimensional imaging
Two cylindrical lenses (CL1 and CL2) were used to collect the light scattered by the target and focus the illuminated area efficiently onto the linear SPAD detector array

Summary

Introduction

One of the most used scanning techniques is based on a synchronous scan approach, which scans the target by using a highly collimated laser source and synchronously collects the scattered signal with a receiver having a narrow field of view [7]. When this scanning technique is used with the triangulation approach, the advantage is improved depth resolution when compared with time-of-flight sensors at short ranges (less than 3 m) [8]; the main challenge is the calibration process to obtain the correct geometrical parameters of the system [9,10]

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Conclusion