Dual-receiver laser distance meter error compensation
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Solution Overview
Problem
Optical distance measuring instruments face reduced measurement accuracy due to systematic errors, particularly temperature-dependent signal times of flight within the evaluation circuit, which existing methods struggle to effectively compensate for.
Innovation Solution
A measuring apparatus with two identical integrated circuits and time measurement units, allowing for cross-connection between reception devices for both distance and reference measurements, enabling the formation of average values or differences to compensate for measurement errors, including temperature drifts and integrated circuit variations, while maintaining low costs by using identical circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference measurement path is used to compensate for background radiation, then measurement accuracy is improved, but systematic measurement errors due to temperature-dependent signal times of flight remain
Solution Approach 1:
The patent divides the measurement system into two separate reception devices (first and second reception devices), each with its own detector unit and time measurement unit. This segmentation allows independent measurement paths that can be combined to cancel out systematic errors. The first reception device measures the time of flight to the target object, while the second reception device measures the time of flight to a reference object, and their results are combined to eliminate temperature-dependent systematic errors.
Solution Approach 2:
The patent changes the operational parameters by introducing a reference measurement path with a known distance to a reference object. By measuring the time of flight to both the target object and the reference object under the same environmental conditions (including temperature), the system can calculate the difference and eliminate systematic errors that affect both measurements equally, such as temperature-dependent signal propagation delays in the evaluation circuit.
2Reliability
If two separate reception devices are used to compensate for systematic errors, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent employs two reception devices that are designed to be as identical as possible in terms of their detector units and time measurement units. This homogeneity ensures that both devices have the same systematic characteristics, including the same temperature-dependent time offsets. By making the devices homogeneous, the systematic errors become correlated and can be eliminated through differential measurement, while avoiding the need for complex calibration procedures.
Solution Approach 2:
The patent creates a copy of the reception device (second reception device) that mirrors the first reception device's structure and functionality. This copying approach allows the system to have two identical measurement paths that can be used in conjunction with each other. The second reception device serves as a reference copy that experiences the same environmental conditions and systematic errors, enabling error cancellation when their measurements are combined.
3Measurement precision
If temperature-dependent time of flight variations are compensated, then measurement accuracy is improved, but additional measurement paths are required
Solution Approach 1:
The patent introduces a reference object as an intermediary element that mediates the measurement process. This reference object serves as a stable reference point with a known distance, allowing the system to measure the time of flight under the same environmental conditions as the target object measurement. The reference measurement acts as an intermediary that captures the systematic errors (including temperature-dependent variations) so they can be subtracted from the target measurement to achieve accurate results.
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 configuration effectively compensates for time-of-flight differences caused by temperature drifts and integrated circuit variations, enhancing measurement accuracy and reliability while keeping costs low by utilizing identical circuits for reception devices.
Implementation Method 1
the distance measuring instruments emit a light beam in the direction of the target object and detect light reflected by the object and returning in the direction of the distance measuring instrument
Implementation Method 2
The distance may be determined by means of a time-of-flight method. The measurement may in this case be carried out in the time domain or in the frequency domain
Data Source
AI summary
A handheld distance measuring instrument includes a first emission device, a first reception device and a second reception device. The first emission device is configured to emit an optical measurement radiation onto a target object. The first reception device is configured to detect the radiation returning from the target object. The second reception device is configured in order to detect a reference radiation internal to the instrument. The reception devices respectively include a first detector unit, a second detector unit, a first time measurement unit, and a second time measurement unit. The first time measurement unit is configured to be connected selectively to the first detector unit and to the second detector unit. The second time measurement unit is configured to be connected selectively to the first detector unit and to the second detector unit.