Optoelectronic Sensor Edge Detection Multi-Frequency Phase
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Solution Overview
Problem
Time-of-flight measurements using phase methods in optoelectronic sensors face challenges with edge detection, leading to inaccurate distance calculations due to the mixing of reflections from multiple object surfaces, which cannot be differentiated, resulting in systematic errors and measurement artifacts.
Innovation Solution
An optoelectronic sensor that modulates transmitted light with multiple frequencies to determine phase offsets and amplitudes, allowing for the detection of edges by evaluating amplitude differences, thereby distinguishing between noise and edge-induced amplitude variations, and discarding or treating edge measurements separately to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase method with single modulation frequency is used, then measurement precision is improved within small range, but unambiguity range is limited to half modulation wavelength
Solution Approach 1:
The measurement process is segmented into multiple measurement cycles, each using a different modulation frequency. By dividing the measurement into segments with different frequencies, the system achieves both high precision (from phase method) and extended unambiguity range (through synthetic difference frequency), resolving the contradiction between precision and range.
Solution Approach 2:
The system transitions from single-frequency measurement to multi-frequency measurement space. By adding the frequency dimension and using synthetic difference frequency, the unambiguity range is extended from half wavelength to a much larger range while preserving the precision benefits of phase-based measurement.
2Area of stationary object
If multiple modulation frequencies are used to extend unambiguity range, then unambiguity range is enlarged, but measurement complexity increases
Solution Approach 1:
The system uses periodic modulation of transmitted light at different frequencies in sequential measurement cycles. This periodic action allows the system to measure phase offsets at multiple frequencies and combine them through synthetic difference frequency, extending unambiguity range while managing complexity through structured periodic measurement.
3Quantity of substance
If transmitted light impinges on edge in monitoring area, then light reflects from multiple object surfaces, but received signal becomes mixture of different distance measurements causing systematic errors
Solution Approach 1:
The system uses feedback from amplitude evaluation to detect edge conditions. By monitoring amplitude differences at different modulation frequencies, the system identifies when light impinges on edges and triggers special evaluation routines, allowing it to distinguish edge cases from normal measurements and correct for the resulting errors.
Solution Approach 2:
The system changes measurement parameters (modulation frequency) to detect and identify edge conditions. By evaluating amplitude differences across different frequencies, the system can recognize when multiple reflections are present and apply appropriate correction or filtering to maintain 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 enhances the accuracy of distance measurements by identifying and handling edge cases correctly, reducing systematic errors and simplifying data processing, particularly beneficial for precise volume measurements and small object detection.
Implementation Method 1
a light transmitter (12) for transmitting transmitted light (16), a light receiver (26) for generating a received signal from remitted light (22) remitted by the object (20)
Implementation Method 2
the control and evaluation unit (28) is configured to modulate the transmitted light (16) with at least a first frequency and a second frequency, to determine a phase offset between transmitted light and remitted light
Implementation Method 3
The light time of flight often is measured in order to determine the distance of a scanned object. This type of distance measurement is also known as ToF (Time of Flight)
Data Source
AI summary
An optoelectronic sensor for determining the distance of an object in a monitoring area has a light transmitter for transmitting transmitted light, a light receiver for generating a received signal from remitted light remitted by the object, and a control and evaluation unit configured to modulate the transmitted light with at least a first frequency and a second frequency, to determine a phase offset between transmitted light and remitted light for the first frequency and the second frequency, and to determine a light time of flight. The control and evaluation unit is configured to determine a first amplitude and a second amplitude for the first frequency and the second frequency from the received signal and to detect whether the transmitted light impinges on an edge in the monitoring area on the basis of an evaluation of the first amplitude and the second amplitude.