Light Curtain Pulse Timing for Fault-Tolerant Object Detection
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Solution Overview
Problem
The reliability of existing light curtains is compromised by amplitude-dependent light pulses, leading to signal distortions and incorrect detection, affecting their ability to reliably monitor surveillance areas.
Innovation Solution
The light curtain employs a pulse train of light pulses from transmitters, with the evaluation unit determining the time interval between pulse sequences of different beam axes and comparing it to a target value to ensure uninterrupted beam axes, increasing detection reliability and tolerance to signal distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If light pulses are used for object detection in the light curtain, then the detection speed and responsiveness are improved, but signal distortion and false detections occur due to amplitude dependency
Solution Approach 1:
The patent changes the evaluation parameter from amplitude-based detection to time interval-based detection. Instead of evaluating the amplitude of received light pulses (which causes distortion and false detections), the system measures the time interval between consecutive pulse sequences from different beam axes. This parameter change eliminates the reliability problem while maintaining the speed advantage of pulsed detection.
2Area of stationary object
If individual transmitters are activated cyclically to monitor multiple beam axes, then the coverage area and detection capability are improved, but the complexity of synchronization and signal evaluation increases
Solution Approach 1:
The patent employs periodic activation of transmitters in a cyclic sequence, where each transmitter is activated in turn to emit light pulses along its beam axis. This periodic action allows multiple beam axes to be monitored systematically while simplifying synchronization, as the cyclic pattern creates predictable time intervals between pulse sequences from different beam axes that can be easily evaluated.
3Use of energy by moving object
If amplitude-dependent light pulses are used, then the energy efficiency and signal concentration are improved, but signal distortion leads to incorrect detection results
Solution Approach 1:
The patent changes the measurement parameter from amplitude to time interval. Instead of measuring the amplitude of light pulses (which is prone to distortion and energy-related variations), the system measures the time interval between pulse sequences from different beam axes. This maintains energy efficiency while achieving accurate detection independent of amplitude variations.
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 reliability and availability of object detection, allowing for high error tolerance even with incorrect detection of individual light pulses, and provides a fault-tolerant method for monitoring surveillance areas.
Implementation Method 1
the transmitters are activated cyclically, one after the other. During each activation, light beams are emitted in the form of a pulse sequence of light pulses
Implementation Method 2
the time interval between the pulse sequence of the transmitter of this beam axis and a pulse sequence of a transmitter of another beam axis is determined as a criterion for an uninterrupted beam axis
Data Source
Figure 1
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Figure 4~5
AI summary
The invention relates to a light curtain (1) for detecting objects in a monitoring area, comprising a number of light beams (3) emitting transmitters (4) and light beams (3) receiving receivers (6). A transmitter (4) and an associated receiver (6) form a beam axis, such that, when the monitoring area is clear, the light beams (3) from all transmitters (4) converge on their respective associated receivers (6). When an object enters the monitoring area, the light beams (3) of at least one beam axis are interrupted. An evaluation unit (8) generates an object detection signal based on the received signals from the receivers (6). The transmitters (4) are activated cyclically, one after the other. During each activation, light beams (3) are emitted in the form of a pulse sequence of light pulses.In the evaluation unit (8), the time interval of the pulse sequence of the transmitter (4) of this beam axis to a pulse sequence of a transmitter (4) of another beam axis is determined as a criterion for an uninterrupted beam axis in the evaluation unit (8) on the basis of received signals and compared with a target value stored in the evaluation unit (8).