SPAD Array Distance Measuring Device with Range Walk Compensation
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Solution Overview
Problem
Existing distance measuring devices face limitations in accurately measuring distances over a wide range due to issues like detector saturation, noise interference, and range walk problems, particularly at short distances or with high reflectivity targets, which restrict their dynamic range and measurement accuracy.
Innovation Solution
The use of an optoelectronic sensor based on an array of single photon avalanche photodiodes (SPAD arrays) in conjunction with a computing unit that derives signature parameters from the reception signal, including amplitude, pulse shape, and curvature, to correct for distance offsets and compensate for range walk, enabling precise distance measurements across a high dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threshold value method is used for detecting backscattered pulses, then noise and interference signals are prevented from being incorrectly detected, but detection is no longer possible when pulse intensity falls below the threshold value, limiting measurement range
Solution Approach 1:
The patent introduces an intermediary signal processing stage between the detector and threshold comparison. The received signal is first amplified by a low-noise amplifier and then processed through a discriminator that extracts timing information before threshold comparison. This intermediary processing allows weak signals to be detected by amplifying them first, then using the discriminator to identify the signal presence independently of absolute amplitude, enabling detection below original threshold levels while maintaining noise rejection.
Solution Approach 2:
The patent applies preliminary signal amplification and conditioning before the threshold detection step. A low-noise amplifier boosts weak backscattered signals before they reach the threshold comparator. Additionally, a discriminator is used in advance to determine signal presence and extract timing information, allowing the system to detect signals that would otherwise be too weak to trigger the threshold, thus extending the measurable distance range.
2Measurement precision
If signal sampling is used to detect weak backscattered signals, then measurement accuracy increases, but detector saturation occurs at short distances or high reflectivity, making signal evaluation impossible
Solution Approach 1:
The patent implements dynamic range compression through the discriminator circuit. Instead of directly sampling the full dynamic range of the received signal which causes saturation, the discriminator dynamically adapts by detecting signal presence and extracting timing information in a way that compresses the dynamic range. This allows the system to handle both very weak distant signals and very strong near signals without saturation, maintaining measurement precision across the full distance range.
Solution Approach 2:
The patent changes the parameter being measured from direct signal amplitude to timing information. By using a discriminator to detect the arrival time of the backscattered signal rather than measuring its absolute amplitude, the system avoids saturation issues. The timing parameter remains valid even when signal strength varies over large ranges, allowing accurate distance measurement from both short and long distances without detector saturation.
3Adaptability or versatility
If conventional photodetectors are used with wide dynamic range, then full signal range is detected, but electronic receiver circuit has limited linear modulation range causing saturation and loss of measurement information
Solution Approach 1:
The patent introduces a discriminator as an intermediary device between the photodetector and the evaluation electronics. The discriminator converts the wide dynamic range optical signal into a standardized timing signal that fits within the limited linear range of electronic circuits. This intermediary transformation allows the system to utilize the full dynamic range capability of the photodetector while keeping the electronic receiver operating within its linear modulation range, preventing saturation and maintaining measurement precision.
Solution Approach 2:
The patent transforms the measurement parameter from signal amplitude (which has wide dynamic range but causes electronic saturation) to time of flight (which has a compressed, electronics-friendly range). The discriminator extracts timing information from the optical signal, converting it into an electrical pulse whose width and position are within the linear handling capability of standard electronic circuits. This parameter transformation enables the system to preserve the photodetector's wide dynamic range advantage while avoiding electronic saturation.
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 solution allows for accurate distance measurements with sub-millimeter precision, both for short and long distances, and on various scattering surfaces, overcoming the limitations of traditional methods by providing a high signal-to-noise ratio and avoiding saturation, thus enabling precise 3D scans and high-precision distance determination.
Implementation Method 1
an optoelectronic sensor based on an array of single photon avalanche photodiodes (SPAD arrays)
Implementation Method 2
the distance to the target can be determined for example on the basis of the time of flight
Data Source
AI summary
A distance measuring device comprising a sensor for highly accurate distance measurement with a very high dynamic range and range walk compensation, said sensor being provided by means of an array of single photon avalanche photodiodes.