Optoelectronic Sensor Distance Measurement Using Split Light Pulses
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Solution Overview
Problem
Conventional pulse methods for distance measurement using optoelectronic sensors face challenges with varying echo pulse amplitudes due to differing object reflectivities, leading to inaccurate time determination and overloading issues, especially when dealing with high and low reflectivity objects, which affects the dynamic range and stability of the receiver.
Innovation Solution
The method involves dividing reflected light pulses into two pulses with different energies, detected in separate channels, allowing for correction of reception times based on the differences in measured times, thereby improving the accuracy of distance measurement by utilizing the rising edge information and reducing noise and temperature dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pulse method is used with a comparator threshold to determine reception time, then the device complexity is low, but the measurement precision deteriorates due to amplitude errors caused by varying object reflectivities
Solution Approach 1:
The received light pulse is split into two separate pulses with different energies using a beam splitter. One pulse is detected by a first photodetector and the other by a second photodetector, allowing simultaneous measurement of both strong and weak echo signals without overloading the receiver.
Solution Approach 2:
The problem of amplitude error is solved by adding an energy dimension to the measurement. Instead of using a single threshold comparison, the system measures the time difference between two pulses with different energies, creating a new measurement dimension that is independent of the original signal amplitude.
2Adaptability or versatility
If the receiver is designed to cover a wide dynamic range to handle objects with varying reflectivities, then the adaptability improves, but the receiver inevitably overloads at high echo amplitudes
Solution Approach 1:
The received light pulse is split into two separate pulses with different energies using a beam splitter. One pulse is detected by a first photodetector and the other by a second photodetector, allowing simultaneous measurement of both strong and weak echo signals without overloading the receiver.
Solution Approach 2:
The system changes the energy parameter of the detected pulses by using a beam splitter to create two pulses with different energy distributions. This allows the receiver to handle a wide dynamic range of echo amplitudes by measuring the time difference between pulses with optimized energy levels for each detection channel.
3Measurement precision
If amplitude compensation is performed by measuring pulse width and subtracting from transit time, then the measurement precision improves, but the reliability deteriorates due to temperature-dependent pulse width instability in overdriven receivers
Solution Approach 1:
The received light pulse is split into two separate pulses with different energies using a beam splitter. One pulse is detected by a first photodetector and the other by a second photodetector, allowing simultaneous measurement of both strong and weak echo signals without overloading the receiver.
Solution Approach 2:
The system uses simple photodetectors without requiring complex temperature stabilization mechanisms. By splitting the pulse and using appropriate detection thresholds, the system achieves temperature-independent measurements without needing expensive thermal control systems.
4Measurement precision
If two threshold measurements are performed in rapid succession to determine rise time, then the measurement precision improves, but the productivity deteriorates due to the requirement for multiple high-accuracy time measurements in the picosecond range
Solution Approach 1:
The system combines multiple measurement functions into a single simultaneous measurement process. By splitting the received pulse and detecting both pulses at the same time with different photodetectors, the system obtains both the time of flight and the rise time information in one measurement cycle, eliminating the need for multiple sequential measurements.
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 distance measurement by correcting for amplitude errors and maintaining high precision across a wide dynamic range, even with weak signals, and is immune to multiple reflections and temperature variations, making it suitable for simple receivers.
Implementation Method 1
a transmitting unit emits light pulses, a receiving unit detects light pulses reflected back from an object to be measured
Implementation Method 2
light pulses reflected back from an object
Implementation Method 3
a receiving unit detects light pulses reflected back from an object
Data Source
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Figure 5
AI summary
The invention relates to a method for measuring the distance of objects, in which the following method steps are carried out: a transmitting unit emits light pulses, a receiving unit detects light pulses reflected back from an object to be measured, and a distance of the object is determined from a time difference between a time of receipt of a light pulse and a time of emission of this light pulse.According to the invention, this method is further developed in that the reflected light pulses are split into a first light pulse and a second light pulse before detection in the receiving unit, wherein the first light pulse has a different energy compared to the second light pulse, that the first light pulses are detected in a first detection channel of the receiving unit, that the second light pulses are detected in a second detection channel of the receiving unit, and that, depending on differences between the measured reception times of the first and second light pulses, the reception times are corrected with a correction value. The invention also relates to an optoelectronic sensor.