SPAD Edge Counting Circuit for Precise Light Detection Timing
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Solution Overview
Problem
Conventional light detection devices using single photon avalanche diodes (SPADs) face challenges in accurately estimating light detection timing due to the delay in peak timing caused by the elongation of pulse signal transmission periods, leading to inaccurate detection of incident light intensity.
Innovation Solution
A light detection device with multiple light receiving parts and edge detection parts, where each light receiving part includes a SPAD and a signal output part generating pulse signals, and edge detection parts count the number of edges between clock signals to accurately estimate light detection timing by avoiding the influence of SPAD response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the period for SPADs to transmit pulse signals is elongated, then the number of SPADs that can respond to incident light increases, but the peak timing of detection is delayed from the true timing
Solution Approach 1:
The patent introduces an edge detection circuit as an intermediary component that detects transitions in the pulse signal from the SPAD. This edge detection mechanism allows the system to capture the timing information at the moment of light detection without being affected by the elongated pulse transmission period, thus resolving the timing accuracy issue while maintaining the ability to detect multiple SPAD responses
Solution Approach 2:
The patent replaces the conventional method of counting pulse signals with a method that detects edges (transitions) in the pulse signal. This substitution changes the detection mechanism from counting entire pulse periods to detecting the rising or falling edges, which occurs at a specific moment and is not influenced by the pulse width or transmission period elongation
2Productivity
If the period for SPADs to transmit pulse signals is elongated, then more incident light can be detected, but the response time influence cannot be avoided
Solution Approach 1:
The patent applies preliminary action by detecting the edge of the pulse signal immediately when it occurs, before the pulse transmission period elongation can affect the timing. The edge detection circuit is prepared and active beforehand to capture the transition moment, ensuring that timing information is recorded at the exact moment of light detection rather than being smeared over an elongated period
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device accurately estimates light detection timing with high precision by counting edges instead of just the number of SPAD responses, effectively correcting for the delay in pulse signal transmission and improving the accuracy of incident light detection.
Implementation Method 1
each of the plurality of light receiving parts has a single photon avalanche diode or a SPAD configured to detect incident photons or incident light
Data Source
AI summary
A light detection device has light receiving parts, edge detection circuits and an addition unit. Each light receiving part has a quench resistance, a SPAD and a pulse signal output part. The SPAD responses incident photons, i.e. incident light. The quench resistance and pulse signal output part generate and transmit a pulse signal to a corresponding edge detection circuit when the SPAD receives and responds to the incident light. The edge detection circuits and the addition unit detects the number of edges during a period from a previously received CLK signal to a currently received CLK signal every time it receives a CLK signal transmitted at a predetermined period. The edge represents a state change from a first state which receives no pulse signal to a second state which receives the pulse signal.