TOF Optical Safety Sensor With Cross-Unit Fault Localization
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Solution Overview
Problem
Existing optical safety sensors using the Time of Flight (TOF) method for intrusion detection require dedicated standard light transmitters and receivers for self-testing, leading to high costs and inability to specify abnormality locations, and they often duplex optical safety sensors which continue monitoring but fail to pinpoint issues when abnormalities occur.
Innovation Solution
An optical safety sensor configuration with multiple light projectors/receivers that measure distances using the TOF method, where each light projector/receiver forms a set with a distance measurement and detection portion, allowing for abnormality detection and location specification by comparing distance measurement results across multiple units, and enabling continued monitoring even if one unit fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated standard light transmitters and receivers are used for self-testing, then safety standard compliance is achieved, but cost increases
Solution Approach 1:
The patent makes the light projectors/receivers serve dual functions: they act as both monitoring sensors for detecting intrusions and as self-test components for safety verification. Each light projector/receiver monitors the monitoring area while also enabling self-testing by having other units receive their projected light, eliminating the need for dedicated standard light transmitters and receivers.
Solution Approach 2:
The optical safety sensor system performs self-testing using its own light projectors/receivers without requiring external dedicated test equipment. The system self-verifies safety by having light projectors/receivers test each other, with each unit serving as both test subject and test instrument, thereby reducing costs while maintaining safety compliance.
2Reliability
If dedicated standard light transmitters and receivers are used for self-testing, then safety verification is achieved, but abnormality location specification capability is lost
Solution Approach 1:
The same light projectors/receivers used for monitoring also perform self-testing, maintaining a one-to-one correspondence between monitoring and testing functions. This unified approach preserves the ability to identify which specific unit is abnormal while ensuring safety verification, unlike dedicated test equipment that loses location information.
Solution Approach 2:
The system implements feedback by having each light projector/receiver test others and report results, creating a network of mutual verification. This feedback mechanism not only verifies safety but also provides diagnostic information about which specific unit is malfunctioning, enabling both safety confirmation and abnormality location identification.
3Duration of action of stationary object
If optical safety sensors are duplexed to continue monitoring, then monitoring continuity is maintained, but diagnostic accuracy decreases
Solution Approach 1:
Each light projector/receiver serves dual purposes: continuous monitoring of the monitoring area and self-testing for diagnostics. This eliminates the need for separate duplexed safety sensors, as the same units perform both monitoring and diagnostic functions, maintaining continuity while improving diagnostic accuracy through comparative analysis.
Solution Approach 2:
The patent uses the light projectors/receivers themselves as intermediaries for mutual testing. Instead of requiring separate safety test equipment, each unit acts as an intermediary that tests others while being tested, enabling continuous monitoring with preserved diagnostic capability through cross-verification.
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 configuration allows for continuous monitoring while detecting abnormalities and specifying their locations, reducing costs by using commercial TOF modules instead of dedicated standard components, and enhancing diagnostic accuracy through comparative analysis.
Implementation Method 1
measures distances to a subject within the monitoring area using time required from the light projecting to the light receiving
Data Source
AI summary
An optical safety sensor is inexpensively implemented. An optical safety sensor includes: a plurality of light projectors/receivers (a first light projector/receiver and a second light projector/receiver), which includes light projecting portions and light receiving portions; distance measurement portions, which measure distances using the time from light projecting to light receiving; and detection portions, which detect, based on measurement results, an abnormality occurring in any one of the plurality of light projectors/receivers; each of the light receiving portion provided in the plurality of light projectors/receivers receives reflected light caused by the light projected from the light projecting portions of all the plurality of light projectors/receivers.