Optical Proximity Sensor Echo Cancellation for Multi-Object Detection
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Solution Overview
Problem
Conventional optical proximity sensors face challenges in reducing light leakage and specular reflections, which degrade their ability to detect objects accurately, and are limited in their capability to simultaneously detect multiple objects at different distances.
Innovation Solution
The implementation of echo cancellation techniques using a coefficient generator, delay, and multiplication units in optical proximity sensors to differentiate between light reflected from objects and interference light, allowing for improved detection range and the ability to detect multiple objects at various distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an opaque light barrier is used to isolate the light source from the light detector, then light leakage is reduced, but the complexity, cost and size of the optical sensor increase
Solution Approach 1:
The patent extracts and removes the harmful light leakage and specular reflection components from the detected signal through digital signal processing. By separating the unwanted reflected light components (barrier reflections, cover plate reflections) from the useful object reflection signal in the time domain, the system eliminates the need for physical light barriers while maintaining detection accuracy.
Solution Approach 2:
The patent replaces the mechanical/optical light barrier structure with an electronic/digital signal processing system. Instead of using physical components to block light, the system uses echo cancellation algorithms to electronically subtract the harmful light components from the detector signal, thereby substituting a mechanical solution with an electronic one.
2Adaptability or versatility
If conventional optical sensors are used, then the structure is simple, but they cannot simultaneously detect multiple objects located at multiple distances
Solution Approach 1:
The patent segments the detected light signal into multiple time-domain components corresponding to different reflection paths. By dividing the continuous detector signal into discrete time segments (each representing reflections from different surfaces at different times), the system can identify and analyze multiple objects at different distances independently within a single detection cycle.
Solution Approach 2:
The patent employs periodic pulsed light emission and corresponds each pulse to its reflected echoes in a periodic manner. By sending out light in periodic pulses and measuring the time-delayed reflections systematically, the system can distinguish multiple objects by their different time delays while maintaining a simple periodic detection rhythm, avoiding the need for complex simultaneous multi-channel detection.
3Reliability
If a cover plate is placed over the optical sensor, then the sensor is protected, but specular reflections reduce the capability to sense proximity
Solution Approach 1:
The patent converts the harmful specular reflections from the cover plate into useful information. By detecting the characteristic time delay and pattern of cover plate reflections, the system identifies these harmful components and uses them as reference signals for echo cancellation, thereby eliminating their harmful effect while preserving the protective cover plate.
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 detection range and accuracy of optical proximity sensors by effectively canceling out interference light and enabling the simultaneous detection of multiple objects at different distances, thereby improving the usability of optical sensors in various applications.
Implementation Method 1
based on the magnitude of light originating from the light source that is reflected from an object and detected by the light detector
Implementation Method 2
an echo canceller includes a coefficient generator that produces echo cancellation coefficients... the echo canceller generates an echo cancellation signal that is combined with the detection signal to produce an echo cancelled detection signal
Data Source
AI summary
An optical sensor includes a driver, light detector and echo canceller. The driver is adapted to selectively drive a light source. The light detector is adapted to produce a detection signal indicative of an intensity of light detected by the light detector. The echo canceller is adapted to produce an echo cancellation signal that is combined with the detection signal produced by the light detector to produce an echo cancelled detection signal having a predetermined target magnitude (e.g., zero). The echo canceller includes a coefficient generator that is adapted to produce echo cancellation coefficients indicative of distance(s) to one or more objects, if any, within the sense region of the optical sensor. The optical sensor can also include a proximity detector adapted to detect distance(s) to one or more objects within the sense region of the optical sensor based on the echo cancellation coefficients generated by the coefficient generator.