Optoelectronic Sensor Time-of-Flight Noise Filtering
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Solution Overview
Problem
Conventional distance measurement methods, such as pulse averaging using histograms, require significant memory and processing resources, especially for spatially resolved 3D imaging, leading to high hardware costs and reduced processing speed, and avalanche photodiodes are prone to noise interference.
Innovation Solution
An optoelectronic sensor that transmits a sequence of light pulses and accumulates individual times of flight only if they coincide within a defined time window, using a filter to distinguish actual signals from noise events, allowing for real-time evaluation without forming memory-intensive histograms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If histogram evaluation is used for pulse averaging, then measurement robustness against interference is improved, but memory requirements and device complexity increase significantly
Solution Approach 1:
The patent extracts only the essential information needed for measurement (individual time of flight values) and processes them sequentially through a filter, rather than storing complete histograms. This removes the memory-intensive histogram storage requirement while retaining the ability to perform pulse averaging and filter out interference events.
Solution Approach 2:
The patent implements a filter structure that processes time of flight values in a nested manner, where each new measurement is compared against previously filtered results. This nested filtering approach allows robust interference rejection without requiring parallel storage of all possible histogram bins.
2Adaptability or versatility
If spatially resolved distance measurement is implemented, then three-dimensional imaging capability is improved, but processing time and memory requirements increase
Solution Approach 1:
The patent segments the measurement process into independent pixel-level operations, where each pixel's time of flight values are filtered separately through the same efficient filter algorithm. This segmentation allows parallel processing across pixels without requiring centralized histogram storage, maintaining processing speed while enabling spatial resolution.
Solution Approach 2:
The patent applies filtering to only the necessary degree for each pixel - processing individual time of flight values just enough to reject interference and determine valid measurements. This partial action approach avoids the excessive computation of complete histogram evaluations for each pixel, maintaining productivity while achieving spatial resolution.
3Measurement precision
If avalanche photodiodes are used for light detection, then detection sensitivity is improved, but susceptibility to noise interference increases
Solution Approach 1:
The patent implements a feedback mechanism where the filter uses previously accepted time of flight measurements to establish expected ranges, and continuously compares new measurements against these ranges. This feedback loop allows the system to maintain high sensitivity to valid signals while automatically adapting to reject noise interference patterns.
Solution Approach 2:
The patent converts the noise interference problem into a benefit by using the statistical properties of noise events. Since noise events occur randomly and don't follow the consistent time of flight patterns of valid reflections, the filter learns to distinguish and reject these harmful events while preserving sensitive detection of valid signals.
4Device complexity
If sequential processing of pixels is used to avoid increased memory requirements, then memory usage is reduced, but acquisition time increases significantly
Solution Approach 1:
The patent implements periodic filtering operations that can be applied to multiple pixels in a systematic sequence. By using efficient filter algorithms that process each pixel independently and rapidly, the system maintains low memory usage while minimizing acquisition time through optimized periodic processing cycles across all pixels.
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 high measurement accuracy with minimal hardware requirements, enabling fast and cost-effective real-time processing while reducing noise interference, particularly suitable for avalanche photodiodes.
Implementation Method 1
a light receiver having at least one light reception element for receiving the individual light pulses reflected or remitted by the object
Implementation Method 2
In an avalanche photodiode (APD), the incident light triggers a controlled avalanche. The charge carriers generated by incident photons are multiplied, and a photo current results which is proportional to the reception light intensity
Implementation Method 3
An individual time of flight measuring unit for determining a sequence of individual times of flight of the individual light pulses as a duration between a transmission point in time of a respective individual light pulse and its reception point in time
Data Source
AI summary
An optoelectronic sensor for measuring a distance comprises a light transmitter (20) for transmitting a sequence of individual light pulses (22) and a light receiver (26) for receiving the individual light pulses (24). An individual time of flight measuring unit (28) determines a sequence of individual times of flight of the individual light pulses (22, 24) as the duration between a transmission point in time and its reception point in time. An evaluation unit (30, 32) accumulates individual times of flight and determines a common measurement value for the distance from the accumulated individual times of flight. The evaluation unit (30) comprises a filter (36) for accumulating an individual time of flight only if it coincides, within a time window, with a preceding individual time of flight.