Optical Distance Sensor Foreign Matter Detection
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Solution Overview
Problem
Optical distance sensors with coaxial optical systems face challenges in accurately detecting foreign matter on the front screen surface due to internal reflections and external contamination, which can lead to measurement inaccuracies and increased complexity with separate optical systems for dirt detection.
Innovation Solution
An optical distance sensor utilizing a coaxial optical system with a time counter and foreign matter detector that differentiates between internal reflections and reflections from external objects based on light pulse characteristics, allowing for accurate detection of foreign matter across the entire front screen surface without additional components or structural complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a coaxial optical system is used for distance measurement, then the structure is simple and alignment is easy, but internal reflection occurs at the front screen causing false sensing
Solution Approach 1:
The patent converts the harmful internal reflection at the front screen into a useful detection signal. By analyzing the time difference and intensity characteristics of the reflected light, the system identifies foreign matter deposits based on the modified reflection pattern, transforming the previously problematic internal reflection into a diagnostic feature for detecting contamination.
2Reliability
If a separate optical system is added for dirt detection, then foreign matter detection capability is improved, but device complexity and number of components increase
Solution Approach 1:
The patent makes the existing distance measurement optical system serve dual purposes: both distance measurement and foreign matter detection. By utilizing the same light emitter, front screen, and receiver while adding temporal and intensity analysis capabilities, the system achieves multi-functionality without adding separate optical components for dirt detection.
Solution Approach 2:
The system uses its own internal reflection characteristics to detect foreign matter. The time counter and intensity detector analyze the light pulses reflected from the front screen itself, allowing the system to self-diagnose contamination using its existing optical path without requiring external detection systems.
3Device complexity
If foreign matter is deposited on the front screen, then the structure remains simple, but measurement accuracy deteriorates due to light reflection from the deposit
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the reflection characteristics from the front screen. By comparing the time difference and intensity of reflected light pulses against reference values, the system detects changes caused by foreign matter deposits and can alert users or adjust measurements accordingly, maintaining accuracy despite contamination.
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
Enables precise detection of foreign matter on the front screen surface, improving measurement accuracy and maintaining a simple sensor structure by leveraging internal reflections for foreign matter detection, while also determining the size and position of deposits and tolerating varying deposition conditions.
Implementation Method 1
a part of the emitted light is reflected by an inner surface of the front screen as an internal reflection
Implementation Method 2
a time counter counting time between emission of the light from the light emitter and reception of the light by the light receiver as counted time
Implementation Method 3
a light receiver for receiving the light, in which the light emitted from the emitter reaches the receiver after a reflection on a detection object
Data Source
AI summary
An optical distance sensor includes a foreign matter detector that utilizes a coaxial optical system for distance measurement as well as utilizing a first pulse and a second pulse respectively caused as an internal reflection of a front screen and as a reflection from a detection object for a detection of foreign matter deposit on the front screen based on a difference of light amounts between the first and second pulse. The foreign matter detector determines that the optical distance sensor is in a normal state, in an obstacle cover state or in a foreign matter deposit state respectively corresponding to three states of the front screen (i.e., (i) having no foreign matter deposit, (ii) having a covering obstacle, or (iii) having a foreign matter deposit).