Optoelectronic Sensor Trigger Circuit for Time-of-Flight Accuracy
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Solution Overview
Problem
The accuracy of distance determination in optoelectronic sensors is affected by latency and temperature drift in the delivery of activation signals to light sources, which complicates time-of-flight measurements.
Innovation Solution
An optoelectronic sensor with a trigger circuit that generates a trigger signal based on a voltage exceeding a threshold at the light source, directly correlating with the emission of light pulses, thereby reducing latency influences and using a voltage divider and monostable flip-flop to process and stabilize the signal for precise time measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current or voltage pulse is delivered to the light source to activate light emission, then the light pulse is emitted and time-of-flight measurement can be performed, but latency and temperature drift occur between the activation signal and light pulse emission, reducing measurement accuracy
Solution Approach 1:
The patent introduces a trigger circuit as an intermediary component that generates a trigger signal based on the actual voltage at the light source. This trigger signal serves as a reliable reference that directly correlates with light pulse emission, eliminating the latency and temperature drift issues associated with separate activation signals. The trigger circuit acts as a mediator between the control system and the light source, providing accurate timing information.
Solution Approach 2:
The trigger circuit incorporates feedback by monitoring the actual voltage applied to the light source and using this information to generate the trigger signal. This feedback mechanism ensures that the trigger signal accurately reflects the real-time state of the light source, compensating for temperature drift and other variations in the electrical characteristics of the light source over time.
2Measurement precision
If calibration is performed to compensate for latency between activation signal and light pulse emission, then measurement accuracy improves, but the system complexity increases due to additional calibration procedures and components
Solution Approach 1:
The patent extracts the timing reference function from the complex calibration procedures and separate activation signaling system. By deriving the trigger signal directly from the light source voltage, the system eliminates the need for separate calibration of latency parameters and complex compensation algorithms. This extraction simplifies the system while maintaining high measurement accuracy.
Solution Approach 2:
The trigger circuit performs self-calibration by automatically adjusting its threshold and timing based on the actual voltage characteristics of the light source. The system uses its own operational parameters (the voltage applied to the light source) to generate the trigger signal, eliminating the need for external calibration equipment or procedures.
3Measurement precision
If additional optical components and light receivers are added to detect light pulse emission, then latency influences are eliminated, but the arrangement becomes complex with increased space requirements and adjustment effort
Solution Approach 1:
The patent replaces the mechanical/optical detection system (light receivers and optical components) with an electrical sensing system. The trigger circuit monitors the electrical voltage at the light source to detect when the light pulse is emitted, substituting complex optical detection with simpler electrical measurement. This eliminates the need for additional optical components while achieving the same timing accuracy.
Solution Approach 2:
The trigger circuit serves multiple functions: it monitors the light source voltage, detects the light pulse emission timing, generates the trigger signal for the time-of-flight measurement, and provides a reference for accuracy compensation. This multi-functionality eliminates the need for separate components for each function, reducing overall system complexity.
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 accuracy of light transit time measurements by directly linking the trigger signal to the light pulse emission, minimizing latency and thermal dependencies, thus improving the precision of distance calculations.
Implementation Method 1
at least one light source for emitting light pulses into a monitored area
Implementation Method 2
An associated light receiver generates received signals from light pulses reflected or remitted by objects in the monitored area
Data Source
Figure 1~2
Figure 3
AI summary
An optoelectronic sensor for detecting and determining the distance of an object in a monitoring area is specified, comprising a light transmitter with a light source for emitting light pulses, a light receiver for generating a received signal from a light pulse emitted by the object, and a control and evaluation unit designed to control the light transmitter and determine a light transit time and, from this, a distance of the object to the sensor. The control and evaluation unit includes a timing unit configured to receive the received signal and a trigger signal and to determine the light transit time from a time interval between the trigger signal and the received signal.The sensor also features a trigger circuit designed to tap into a voltage applied to the light source of the light transmitter and to output the trigger signal when the amount of the tapped voltage exceeds a predetermined threshold.