Optical Distance Measurement with Adaptive Noise Thresholds
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Solution Overview
Problem
Conventional optical distance measuring apparatuses using photon-counting light receiving elements face issues with erroneous detection of reflected signals due to inappropriate threshold settings, especially when noise distributions do not follow a normal distribution, leading to increased detection rates or reduced detection distances.
Innovation Solution
An optical distance measuring apparatus that adaptively sets a detection threshold based on the relationship between a reference level and a boundary level derived from the average value of a noise probability distribution, using a conversion database to maintain a desired erroneous detection rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed threshold is used for signal detection, then the device complexity is reduced, but the reliability of detection increases due to adaptive threshold adjustment
Solution Approach 1:
The patent performs preliminary characterization of the noise probability distribution before actual distance measurement. By pre-analyzing the statistical properties of background noise and storing the relationship between reference levels and boundary levels in a conversion database, the system prepares detection parameters in advance, enabling reliable detection without complex real-time calculations.
Solution Approach 2:
The patent implements a feedback mechanism where the detected signal level continuously updates the threshold setting. The boundary level is dynamically adjusted based on the reference level obtained from the light receiving signal, creating a closed-loop system that adapts to changing noise conditions and maintains optimal detection reliability.
2Length of stationary object
If a low threshold is set to increase detection distance, then the measurement range is extended, but the erroneous detection rate increases due to noise
Solution Approach 1:
The patent changes the threshold parameter from a fixed value to a dynamically adjusted value based on noise statistics. By modifying the threshold setting mechanism to incorporate probability distribution analysis, the system can extend detection distance while maintaining low erroneous detection rates through adaptive parameter optimization.
Solution Approach 2:
The patent replaces simple threshold comparison with a statistically-based detection mechanism. Instead of using a fixed mechanical threshold, the system employs probability distribution analysis and cumulative probability calculations to determine optimal thresholds, substituting crude mechanical detection with sophisticated statistical processing.
3Reliability
If a high threshold is set to reduce erroneous detection, then the reliability improves, but the detection distance is reduced
Solution Approach 1:
The patent transforms the static threshold into a dynamic parameter that adapts to signal conditions. The threshold is no longer fixed but changes continuously based on the reference level and noise characteristics, allowing the system to optimize the balance between detection distance and erroneous detection rate in real-time.
4Measurement precision
If conventional threshold setting is used, then the ease of operation is maintained, but the measurement precision decreases due to inappropriate threshold selection
Solution Approach 1:
The patent implements self-service threshold setting where the system automatically determines optimal thresholds without user intervention. The conversion database and automatic boundary level calculation enable the device to self-optimize detection parameters based on environmental conditions, eliminating the need for manual threshold adjustment while improving precision.
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 apparatus effectively reduces erroneous detection rates while maintaining detection distance by dynamically adjusting the threshold according to noise conditions, enhancing the accuracy and reliability of distance measurements.
Implementation Method 1
The optical distance measuring apparatus using time-of-flight method (TOF: Time Of Flight) has a high spatial resolution (angular resolution) and can measure a wide angular range and a large range of distances
Implementation Method 2
the optical distance measuring apparatus includes a light emitting means, light receiving means, signal discrimination means, propagation estimation means and threshold setting means
Data Source
AI summary
An optical distance measuring apparatus comprises a laser diode emitting a light pulse, light receiver including a photon-counting light receiver, distance measurement unit including a signal discriminator and propagation estimator, and threshold determiner. The signal discriminator discriminates the signal component, exceeding a threshold, of the signal as a reflected signal resulting from reflection of the light pulse at a measurement object. The propagation estimator estimates a round-trip propagation time of the light pulse to the measurement object using the signal. The threshold determiner sets a boundary level as the threshold, corresponding to a reference level obtained from the signal when the signal discriminator determines the reflected signal, using the relationship between the reference and the boundary level. The reference level is obtained from the average value of a noise probability distribution in the signal. The boundary level represents a predetermined cumulative probability in the noise probability distribution.