SPAD Array Signal Summing for Optical Distance Measurement
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Solution Overview
Problem
Existing optical distance sensors using single photon avalanche photodiodes (SPADs) face challenges in accurately detecting light due to stochastic reactions, leading to variations in photon detection, which affects the accuracy of distance measurement.
Innovation Solution
A light detection device comprising multiple SPADs, a signal combining circuit, a detection circuit, a time measurement circuit, and a timing extraction circuit that detects incident light by summing output signals and measuring the count period between the detection start timing and the detected timing, extracting timing information to facilitate accurate light detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single SPAD is used for light detection, then the device complexity is low, but the measurement precision deteriorates due to stochastic reactions
Solution Approach 1:
Multiple SPADs are combined into an array configuration where their output signals are summed together. This merging approach maintains individual SPAD simplicity while achieving improved measurement precision through statistical processing of combined signals from multiple stochastic detectors.
2Measurement precision
If multiple SPADs are used simultaneously for detection, then the measurement precision improves through statistical processing, but the detection timing becomes ambiguous
Solution Approach 1:
A timing extraction circuit performs preliminary detection and extraction of timing information from the combined signal before final measurement processing. This preliminary action identifies the detection timing by analyzing when the combined signal from multiple SPADs exceeds a threshold, resolving the timing ambiguity that would otherwise occur with simultaneous multi-SPAD detection.
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 solution enables accurate light detection and improved distance measurement by acquiring multiple timings for stochastic SPAD reactions, reducing variations and enhancing the sensitivity of light detection in optical distance sensors.
Implementation Method 1
a plurality of photosensors 10a to 10c receive light to generate output signals Sa to Sc indicating light reception results, respectively
Implementation Method 2
The time measurement circuit 4 measures a count period T2 between the detection start timing and the detected timing based on the detection signal S2. The optical distance sensor 2 measures a distance corresponding to the count period T2
Data Source
AI summary
A light detection device detects incident light according to a detection start timing. The light detection device includes photosensors, a signal combining circuit, a detection circuit, a time measurement circuit, and a timing extraction circuit. The photosensors receive light to generate output signals indicating light reception results, respectively. The signal combining circuit sums output signals from the respective photosensors to generate a combined signal. The detection circuit detects a timing at which the combined signal reaches a first threshold or larger to generate a detection signal. The time measurement circuit measures a count period between the detection start timing and the detected timing based on the detection signal. The timing extraction circuit extracts timing information from a predetermined period defined by the detected timing as a reference, the timing information indicating a timing at which the combined signal increases.