SPAD Time-of-Flight Readout for Lower Power and Data Throughput
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Solution Overview
Problem
Time-of-flight sensors face challenges with high power consumption and large data throughput, necessitating the development of more advanced sensing devices and methods that minimize power consumption and data throughput.
Innovation Solution
The proposed solution involves a sensing device with an array of single photon avalanche diodes (SPADs) coupled to a readout circuit, including time-to-digital converters (TDCs), a delay locked loop, and a multiplexer, which performs pre-processing operations such as averaging or summing raw data frames to reduce data throughput while maintaining accurate depth mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Time-correlated single photon counting (TCSPC) methodology is used to achieve high precision depth measurement, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent divides the sensing device into multiple independently controllable groups, where each group contains several SPADs sharing common readout circuitry. This segmentation allows selective activation of only necessary sensing groups, reducing overall power consumption while maintaining measurement precision in active regions.
Solution Approach 2:
The patent implements variable resolution depth mapping where different regions of the sensing array operate at different precision levels. Less critical regions use lower resolution (reducing power consumption) while critical regions maintain high resolution, achieving partial action that balances precision and energy usage.
2Measurement precision
If Time-correlated single photon counting (TCSPC) methodology is used to achieve high precision depth measurement, then measurement precision is improved, but data throughput increases
Solution Approach 1:
The patent merges readout operations by having multiple SPADs within a group share common readout circuitry and timing resources. This combining approach reduces the total number of independent data streams, lowering data throughput requirements while preserving measurement precision through coordinated readout of the grouped sensors.
Solution Approach 2:
The patent applies variable resolution depth mapping that processes only necessary data at high precision levels. By identifying and prioritizing critical measurement regions, the system performs partial high-precision processing only where needed, reducing overall data throughput while maintaining essential measurement accuracy.
3Measurement precision
If array of single photon avalanche diodes with full readout circuitry is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines readout functions by implementing shared readout circuitry that serves multiple SPADs within each group. This merging eliminates redundant circuit elements, reducing device complexity and component count while maintaining the precision capabilities of individual SPADs through coordinated group readout.
Solution Approach 2:
The shared readout circuitry is designed to handle multiple sensing channels simultaneously, making it a universal component that performs the measurement function for entire groups of SPADs. This multi-functional approach reduces overall device complexity by replacing multiple specialized circuits with a single versatile readout system.
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
This approach achieves low power consumption and reduced data throughput while maintaining high precision in depth measurement, as evidenced by the reduction in full-width half maximum (FWHM) values and improved histogram analysis, enabling efficient operation in miniaturized sensing applications.
Implementation Method 1
an array of single photon avalanche diodes (SPADs) coupled to a readout circuit
Data Source
AI summary
A method of a sensing device, comprising steps of emitting, by a light source of the sensing device, a light pulse in each of n cycles; measuring, by a single photon avalanche diodes array of the sensing device, a time-of-flight value with a resolution of m in each of the n cycles to generate n raw data frames based on a reflected light of the light pulse; performing, by a pre-processing circuit of the sensing device, a pre-processing operation to n raw data frames to generate k pre-processed data frames, wherein m, n and k are natural numbers, and k is smaller than n; and generating, by post-processor of the sensing device, a histogram according to the k pre-processed data frames and analyzing the histogram to output a depth result.