Non-line of Sight imaging by SPAD: Difference between revisions
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===Difference between APD and SPAD=== | ===Difference between APD and SPAD=== | ||
Traditional avalanche photo detector (APD) and SPAD both use avalanche effect to amplify signal. However, | Traditional avalanche photo detector (APD) and SPAD both use avalanche effect to amplify signal. However, they are very different in circuit configuration and performance. APD is often reversely biased to have a gain around 10-100, while SPAD is biased above breakdown voltage with a gain above <math>10^6</math> or even up to infinity. In timing response, APD usually have a time resolution of sub nanoseconds while SPAD have a time resolution of pico-seconds. The bandwidth of APD is limited by RC delay and timing resolution. On the other hand, SPAD is constrained by dead time, where it has to rest for a while before being sensitive to next arrival photon. | ||
===Work principle of SPAD=== | ===Work principle of SPAD=== | ||
Because of dead time, the measurement method for using SPAD is time-correlated single photon counting (TCSPC). We would like to use bio-fluorescence as a working example. As shown in | |||
===Imaging model of SPAD=== | ===Imaging model of SPAD=== | ||
Revision as of 07:08, 16 December 2016
Introduction
Silicon single photon avalanche detector (Si SPAD) has become a hot topic today for its single photon sensitivity, pico-second timing resolution and CMOS compatibility and low cost. Because of its unique properties, it becomes a tool to capture transient imaging for computer vision industry. One of applications enabled by transient imaging is non-line of sight problem, usually being referred to "look around the corner", where using Si SPAD, we could locate, track and recognize the shape of objects around the corner without directly seeing it.
The object of our project is to simulate Si SPAD response in non-line of sight imaging using ray tracing and verify its algorithm to track position of "hidden" object.
There have been multiple papers published on this topic. The one we have studied is “Detection and tracking of moving objects hidden from view”. It was published last year on nature photonics. The scenario they provided is as follow. First they have the SPAD and laser light source hang at the wall. Then the laser and SPAD would first hit the ground. And these two regions at the ground are our starting point and the end point.
This remains a hot area for recently years. The one we focus on is "“Detection and tracking of moving objects hidden from view".
Background
Difference between APD and SPAD
Traditional avalanche photo detector (APD) and SPAD both use avalanche effect to amplify signal. However, they are very different in circuit configuration and performance. APD is often reversely biased to have a gain around 10-100, while SPAD is biased above breakdown voltage with a gain above or even up to infinity. In timing response, APD usually have a time resolution of sub nanoseconds while SPAD have a time resolution of pico-seconds. The bandwidth of APD is limited by RC delay and timing resolution. On the other hand, SPAD is constrained by dead time, where it has to rest for a while before being sensitive to next arrival photon.
Work principle of SPAD
Because of dead time, the measurement method for using SPAD is time-correlated single photon counting (TCSPC). We would like to use bio-fluorescence as a working example. As shown in
Imaging model of SPAD
Methods
1) paper scene experiment 2) volumetric reconstruction
Results
1) Ray optic distribution 2) distance relationship 3) ray optics distribution verification 4) volumetric reconstruction verification
