DTOF Sensor Array Timing Layout for Distance Error Correction
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Solution Overview
Problem
Existing direct time-of-flight (DTOF) sensors face challenges in achieving precise distance measurements due to transmission delays in logic circuits, leading to significant errors in calculated distances.
Innovation Solution
A DTOF sensor array system with a 2-dimensional array of single-photon avalanche diodes (SPADs) and a processing circuitry that includes TDC blocks on opposite sides to measure roundtrip photon travel time, using complementary signal paths to correct for path length biases and calculate an average time difference to determine accurate distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a direct time-of-flight (DTOF) method is used to calculate distance by measuring total flight time of emitted light, then distance measurement capability is achieved, but transmission delays in logic circuits contribute relatively large errors to the measured distance results
Solution Approach 1:
The patent introduces TDC blocks as intermediary components that convert time measurements to digital values, and histogramming circuits as mediators that aggregate multiple measurements to statistically determine flight time, thereby isolating the measurement process from logic circuit delays and improving accuracy
Solution Approach 2:
The system implements feedback through the histogramming process where multiple distance measurements are accumulated and processed to generate a probability distribution, allowing the system to identify the most likely true distance by analyzing the peak of the distribution, thus compensating for random errors from transmission delays
2Measurement precision
If high precision on measuring flight time is required to reduce error, then measurement accuracy improves, but device complexity increases due to additional components needed for precise timing
Solution Approach 1:
The patent segments the sensor array into multiple pixels, each with its own TDC block and histogramming circuit, allowing parallel processing of multiple measurements simultaneously. This segmentation enables high precision through statistical aggregation while distributing complexity across many simple, identical units rather than requiring one complex centralized timing 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
The system provides accurate and precise distance measurements by mitigating path length biases and errors, enabling the generation of depth images with relative and absolute distance information.
Implementation Method 1
a direct time of flight (DTOF) sensor array (210) to an object (109)... a plurality of single-photon avalanche diodes (SPADs) disposed in a plurality of pixels
Implementation Method 2
measuring the total flight time of the emitted light... measuring the roundtrip photon travel time... calculate a first distance from the first pixel to the object according to a first arrival time of the first photon detection signal
Data Source
AI summary
An apparatus, a processing circuitry and a method for measuring a distance to an object are provided. The apparatus comprising a light source, a direct time of flight (DTOF) sensor array configured to receive a reflected signal from the object, a processing circuitry coupled to the DTOF sensor array and comprising a first time to digital converter (TDC) and a second TDC, respectively disposed on opposite sides of the DTOF sensor array, the processing circuitry configured to receive, by the first TDC, a first photon detection signal transmitted by a first pixel, receive, by the second TDC, a second photon detection signal transmitted by the first pixel, and calculate a first distance from the first pixel to the object according to a first arrival time of the first photon detection signal detected by the first TDC and a second arrival time of the second signal detected by the second TDC.