Optical Scanning Photoelectric Switch Interference Prevention
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Solution Overview
Problem
Optical scanning type photoelectric switches experience interference with adjacent switches, leading to inaccurate distance measurement and potential safety issues, as they scan a two-dimensional plane and measure object distance based on time differences in light projection and reception.
Innovation Solution
The optical scanning type photoelectric switch adjusts its light projection period and scanning period, and phase of the light projection pulse to prevent interference by changing these parameters when the object's position is determined to be inside the protection area multiple times, ensuring a non-permission signal is output only when the object is consistently within the area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the optical scanning type photoelectric switch scans a two-dimensional plane in a broad range, then the coverage area is improved, but interference with adjacent photoelectric switches occurs
Solution Approach 1:
The patent applies periodic action by modulating the light projection pulse with a specific period (frequency) that is unique to each photoelectric switch. This periodic modulation allows the receiving end to distinguish between light from its own transmitter and light from adjacent switches by detecting the specific frequency, thereby preventing interference while maintaining broad coverage area.
Solution Approach 2:
The patent changes the parameter of light projection period (or scanning period/phase) dynamically. When interference is detected, the system changes the light projection period to a different value, which resolves the interference issue while maintaining the broad scanning coverage. This parameter change approach allows the system to adapt to different installation environments.
2Object-affected harmful factors
If the light projection period is changed to prevent interference, then interference with adjacent switches is reduced, but the light curtain formation at desired height is affected
Solution Approach 1:
The patent applies dynamics by making the light projection period changeable rather than fixed. The system can dynamically adjust the light projection period based on the installation environment and requirements. This allows the light curtain to be formed at the desired height while using a different period value to prevent interference with adjacent switches.
Solution Approach 2:
The patent changes the light projection period parameter to resolve interference issues. By selecting an appropriate period value that differs from adjacent switches, the system can maintain both the desired light curtain height and prevent interference simultaneously.
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 solution effectively prevents repeated interference with adjacent switches by dynamically adjusting the light projection and scanning periods, ensuring accurate distance measurement and reliable safety signal output.
Implementation Method 1
measures a distance to the object based upon a time difference between a light projection timing of a light projection pulse and a light reception timing of reflected light from the object
Implementation Method 2
performs two-dimensional scanning with light projection pulse to detect an object
Data Source
AI summary
There is provided an optical scanning type photoelectric switch capable of preventing interference with another photoelectric switch by use of its own capability, wherein, as for light projection pulse periods of the first and second optical scanning type photoelectric switches, the period is set to 30 μs in the first optical scanning type photoelectric switch while the period is set to 33 μs in the second optical scanning type photoelectric switch 1B, the light projection pulses have the same pulse width, and by setting the light projection periods different between the first and second optical scanning type photoelectric switches, even if mutual interference occurs between any optical axes, a phase difference of 36 degrees in rotation period is generated therebetween in a next scan, thereby preventing occurrence of the interference in succession in a plurality of times of scanning.