SPAD Distance Measurement via Probability Evaluation
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Solution Overview
Problem
Existing 3D distance measurement methods using single-photon avalanche diodes (SPADs) face challenges with background light interference and high circuit complexity, leading to erroneous measurements and increased susceptibility to defects.
Innovation Solution
A device and method that emit light pulses with definable pulse durations, receive detection signals, and evaluate probability values across time windows to determine object distance using the time-of-flight method, reducing the need for counters or time-to-digital converters and enhancing hardware efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct time-of-flight measurement with TDC is used, then distance measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the TDC (time-to-digital converter) and counter components from the sensor system. Instead of using complex electronic timing circuits, the invention uses a simplified approach where the light pulse duration directly defines the measurement window, eliminating the need for sophisticated time measurement electronics while maintaining distance measurement capability.
Solution Approach 2:
The patent changes the measurement parameter from direct time-of-flight measurement to probability-based detection within defined time windows. By using the pulse duration as a fixed parameter and measuring detection probabilities across multiple pulses, the system achieves distance measurement without requiring complex time measurement circuits.
2Productivity
If multiple counters are used for time-efficient measurement, then measurement speed is improved, but device complexity increases
Solution Approach 1:
The patent removes the counter components entirely from the system. Instead of counting photons within time windows using complex counter circuits, the invention uses probability calculation based on detection events, which can be implemented with simpler logic circuits while maintaining high measurement speed.
Solution Approach 2:
The patent replaces the mechanical/electronic counting system with a probability-based detection system. Rather than using counters to tally detection events, the system calculates probabilities based on detection patterns across multiple pulses, substituting complex counting mechanics with simpler probabilistic evaluation.
3Measurement precision
If SPADs are operated in Geiger range for single photon detection, then detection sensitivity is improved, but susceptibility to background light increases
Solution Approach 1:
The patent uses periodic light pulse emission with defined durations to create time-gated measurement windows. By emitting pulses at regular intervals and defining detection windows based on pulse duration, the system can distinguish between reflected signal photons and background light photons, reducing background interference while maintaining single-photon detection sensitivity.
Solution Approach 2:
The patent performs preliminary definition of time windows based on light pulse duration before actual detection occurs. By pre-defining when to expect signal photons based on the known pulse timing and duration, the system can filter out background light that arrives outside these predetermined windows, reducing background interference before it affects measurement accuracy.
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 reduces circuit complexity, improves resistance to background light, and enables higher-resolution sensors with increased filling factor and pixel numbers, while maintaining accurate distance measurements.
Implementation Method 1
the time of flight of light pulses, e.g. of infrared laser light, which are emitted by a transmission device and reflected by a target object, are measured by detecting the residual intensity
Implementation Method 2
light pulses, e.g. of infrared laser light, which are emitted by a transmission device and reflected by a target object
Implementation Method 3
Single-photon avalanche diodes (SPAD) are avalanche photodiodes operated above their breakdown voltages (avalanche voltages). Within this so-called Geiger range, one single photon, which is absorbed within the active range of the diode and generates a free charge carrier, will suffice for resulting in the breakdown of the diode and, therefore, in a macroscopic flow of current through the diode
Implementation Method 4
one single photon, which is absorbed within the active range of the diode and generates a free charge carrier
Data Source
AI summary
The invention relates to a device for determining a distance from an object, including a transmission device for emitting several light pulses including a pulse duration, including a reception device for receiving signals and for generating detection signals, and including an evaluation device for evaluating the detection signals. The evaluation device determines, on the basis of a number of the light pulses emitted and on the basis of the detection signals, probability values of several time windows which each have a respective time period equaling the pulse duration which relate to probabilities for reception of a signal within one of the time windows, respectively. In addition, the evaluation device determines, in accordance with the time-of-flight method, a measure of the distance of the object on the basis of the probability values determined. In addition, the invention relates to a corresponding method.