Tracking Laser Interferometer Absolute Distance Estimation
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Solution Overview
Problem
Conventional tracking laser interferometers face limitations in measurement accuracy due to triangulation methods and require cumbersome operations or expensive absolute distance sensors for precise distance measurement between the interferometer and retroreflector, which hinders high-accuracy applications.
Innovation Solution
The method estimates the absolute distance by performing arithmetic operations based on angular position variations of the two-axis rotating mechanism, using deviation amounts of return light relative to a predetermined position, eliminating the need for an additional absolute distance sensor and allowing for automatic reestimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If triangulation method with two-axis rotating mechanism is used for distance measurement, then spatial two-axis coordinate measurement is achieved, but measurement accuracy is limited
Solution Approach 1:
The patent combines the distance measurement function and optical axis direction measurement function into a single integrated system. The distance measurement unit and the unit for measuring optical axis direction deviations work together to provide both relative distance and absolute distance information, eliminating the need for separate measurement systems and improving overall measurement accuracy.
Solution Approach 2:
The patent introduces a retroreflector as an intermediary element that reflects measurement light back to the interferometer. This retroreflector enables the system to measure both the distance to the target and the alignment of the optical axis by analyzing the reflected light, thereby improving measurement capabilities without adding complex direct measurement devices.
2Measurement precision
If absolute distance sensor is added to improve distance measurement accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the measurement light serve multiple functions: it simultaneously measures relative distance through interferometry and provides information for absolute distance calculation through the interaction with the retroreflector. This multi-functionality eliminates the need for separate absolute distance sensors while maintaining high measurement accuracy.
Solution Approach 2:
The system uses its own measurement light and existing optical components to determine absolute distance. By analyzing the deviation amounts of reflected light and the operational state of the two-axis rotating mechanism, the system self-determines absolute distance without requiring external sensors or additional measurement devices.
3Measurement precision
If manual origin return operation is required for absolute distance measurement, then absolute distance can be determined, but operation time and complexity increase
Solution Approach 1:
The patent implements feedback control where the position detecting element continuously monitors the deviation of the reflected light spot from the optical axis. This feedback information is used to automatically adjust the two-axis rotating mechanism and calculate absolute distance in real-time, eliminating the need for manual origin return operations and significantly reducing operation time.
Solution Approach 2:
The system performs preliminary calibration by establishing the relationship between the deviation amounts measured by the position detecting element and the corresponding absolute distance values. This preliminary action enables the system to directly determine absolute distance during normal operation without requiring time-consuming manual return to origin operations.
4Ease of operation
If tracking control is performed without considering distance variations, then system operation is simplified, but tracking precision deteriorates
Solution Approach 1:
The patent implements dynamic tracking control where the control amount automatically adjusts based on the measured distance. As the distance between the interferometer and retroreflector changes, the system dynamically modifies the tracking control parameters to maintain optimal tracking precision throughout the measurement range, rather than using fixed control parameters.
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 tracking control precision, reduces operator intervention, and maintains high accuracy with fewer errors, enabling robust and efficient coordinate measurement systems.
Implementation Method 1
the retroreflector for reflecting and returning incident measurement light in an incident direction
Implementation Method 2
a two-axis rotating mechanism for rotationally moving in an exit direction of the measurement light so that optical axes of the measurement light and return light are collimated
Implementation Method 3
tracking laser interferometers by laser interferometry length measurement
Data Source
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AI summary
To provide a method for estimating an absolute distance L between a tracking laser interferometer and a retroreflector 70, the tracking laser interferometer including; the retroreflector 70 for reflecting and returning incident measurement light A in an incident direction; and a two-axis rotating mechanism 40 for rotationally moving in an exit direction of the measurement light A so that optical axes of the measurement light A and return light B are collimated, which outputs a measurement value according to an increase or decrease in the distance between the interferometer and the retroreflector 70, wherein the absolute distance L between the interferometer and the retroreflector 70 is estimated by performing arithmetic operation based on an angular position variation θ2 of the two-axis rotating mechanism 40 when a deviation amount d of the return light B from the retroreflector 70 relative to a predetermined position is given as a predetermined value d2. This enables an appropriate increase or decrease of the control amount of a tracking control according to a distance between the interferometer and the retroreflector without forcing an operator to perform a troublesome origin return operation and adding an expensive absolute distance sensor.