TOF Optical Safety Sensor with Shared Self-Diagnosis
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Solution Overview
Problem
Existing optical safety sensors using the Time of Flight (TOF) method for monitoring areas are costly due to dedicated standard light transmitters and receivers for self-test, and fail to accurately identify abnormality locations when malfunctions occur, leading to incomplete monitoring coverage.
Innovation Solution
An optical safety sensor configuration utilizing multiple light projectors/receivers that share distance measurement and detection portions, allowing for continuous monitoring even if one unit fails, with abnormality diagnosis through comparative distance measurements and light sharing between units, enabling cost-effective implementation and precise abnormality location identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated standard light transmitters and receivers are used for self-test, then safety standard compliance is achieved, but equipment cost increases
Solution Approach 1:
The light projectors/receivers are designed to perform multiple functions: both monitoring the monitoring area and serving as test targets for self-test. This eliminates the need for separate dedicated standard light transmitters and receivers, reducing equipment cost while maintaining safety standard compliance
Solution Approach 2:
The system uses itself as the test target for self-test. The light projectors/projected light and light receivers/reflected light are configured such that each unit can test the others, eliminating the need for external dedicated test equipment
2Reliability
If simple duplexing of optical safety sensors is used, then continuous monitoring is maintained, but abnormality location identification capability is lost
Solution Approach 1:
The system compares distance measurement results from multiple light projectors/receivers to detect abnormalities. When a malfunction occurs, the comparison mechanism provides feedback that enables identification of the specific abnormal location, maintaining both continuous monitoring and diagnostic capability
Solution Approach 2:
The monitoring area is divided into multiple regions monitored by different light projectors/receivers. This segmentation allows the system to identify which specific unit has malfunctioned by comparing results from different segments, preserving abnormality location identification while maintaining continuous monitoring
3Area of stationary object
If multiple light projectors/receivers are used, then monitoring coverage is improved, but system complexity increases
Solution Approach 1:
Multiple light projectors and light receivers are merged into integrated light projectors/receiver units. Each unit combines both light projecting and light receiving functions, simplifying the overall system configuration while expanding monitoring coverage
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 continuous and accurate monitoring of areas with reduced equipment costs by using commercial TOF modules, allowing for the detection and diagnosis of malfunctions in light projectors/receivers, thus ensuring comprehensive and reliable monitoring.
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
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AI summary
An optical safety sensor is inexpensively implemented. An optical safety sensor (1) includes: a plurality of light projectors/receivers (a first light projector/receiver (20A) and a second light projector/receiver (20B)), which includes light projecting portions (21) and light receiving portions (22); distance measurement portions (31), which measure distances using the time from light projecting to light receiving; and detection portions (32), 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.