Distance Measuring Device Multi-Threshold Noise Filtering
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Solution Overview
Problem
Distance measuring devices employing the Time of Flight method face challenges in accurately detecting objects due to erroneous detection of internal noise, particularly in scenarios with low brightness or far objects, leading to inaccurate measurements and false alarms.
Innovation Solution
The implementation of a distance measuring device with multiple thresholds and reference distances, where a comparator system sets high and low thresholds to differentiate between signal and noise, and determines valid distance measurements based on the intersection points of the received signal with these thresholds, effectively filtering out internal noise and improving accuracy across various brightness levels and distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the threshold is set to a low value to detect far objects with low brightness, then the detection range and sensitivity are improved, but internal noise is erroneously detected as valid signals
Solution Approach 1:
The patent segments the threshold detection process into multiple discrete threshold levels (first threshold, second threshold, third threshold) with different heights. By dividing the single threshold detection into multiple staged thresholds, the system can differentiate between noise signals and valid reflected light signals, resolving the contradiction between detection sensitivity and false alarm rate.
Solution Approach 2:
The patent introduces a new dimension of threshold height differentiation, creating multiple threshold levels rather than using a single threshold value. This dimensional expansion allows the system to evaluate signals at multiple sensitivity levels, enabling discrimination between noise and valid signals while maintaining high detection sensitivity.
2Measurement precision
If multiple thresholds with height differences are used to improve distance measurement accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the threshold processing into distinct stages with clearly defined height relationships (first threshold > second threshold > third threshold). Each threshold level corresponds to specific detection scenarios, organizing the complexity into manageable segments rather than a monolithic processing system.
Solution Approach 2:
The patent systematically varies the threshold parameter across three distinct levels, creating a gradient of sensitivity. By changing the threshold parameter in a structured manner (with specific height relationships), the system achieves high measurement precision while maintaining manageable processing complexity through predictable parameter progression.
3Adaptability or versatility
If the threshold is set low to detect weak reflected light from far objects, then detection capability is improved, but internal noise from optical components is erroneously detected
Solution Approach 1:
The patent segments the detection process into multiple threshold-based evaluation stages. By dividing the single detection event into multiple threshold comparisons (first, second, and third thresholds), the system can identify and reject noise signals that would otherwise be detected as valid reflections, thereby reducing internal noise interference while maintaining detection capability.
Solution Approach 2:
The patent introduces intermediate threshold levels (particularly the second threshold positioned between the first and third thresholds) that act as mediators in the detection process. These intermediate thresholds serve as filtering stages that allow valid weak signals to pass through while blocking noise signals, reducing internal noise interference without sacrificing detection capability.
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 allows for accurate distance measurement without the influence of internal noise, enabling reliable detection of objects at both near and far distances, even with low brightness, and reduces the occurrence of false alarms by setting predetermined invalid distances for noise detection.
Implementation Method 1
a light receiving element (15) to receive the signal reflected by the object and to output a received signal according to the received strength
Implementation Method 2
A TOF method measures the distance to an object by measuring transmitting time (Time of Flight) of a signal emitted by emitting a pulse of a laser beam hitting an object and then returning
Data Source
Figure 1~2
Figure 3A~3C
Figure 4A~4B
AI summary
The present invention makes it possible to measure the distance to an object with high precision by avoiding the effects of noise. This distance measuring device is provided with: a transmitting means (12); a receiving means (15) for receiving a signal reflected from an object; a received signal detecting means (19) for outputting a digital signal which identifies when the received signal output by the receiving means exceeds a threshold and when the received signal does not exceed said threshold; and a signal processing means (10) for calculating the distance to the object on the basis of a propagation time of the signal from the transmitting means to the receiving means via the object; wherein one or a plurality of thresholds (Th1, 2, ...) at different levels are set in the received signal detecting means, and one or a plurality of different reference distances (D1, 2, ...) are set in the signal processing means, and for each threshold, if the distance calculated for the threshold satisfies a condition of being greater than a certain reference distance, the signal processing means sets the distance as a valid value, and if the condition is not satisfied, the signal processing means sets the distance as an invalid value. Further reference distances are applied to lower thresholds.