Laser Scanner Prism Rotation Angle Correction
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Solution Overview
Problem
The laser scanner using Risley prisms experiences errors in distance measurement due to optical path length differences caused by the rotation angles of the prisms, leading to inaccuracies in deflecting and receiving distance measuring light.
Innovation Solution
A method and device that corrects the measurement value by detecting the rotation angles of the prisms and calculating the optical path length differences, using a correction table or parameters to adjust the distance measurement value, thereby accounting for the path length variations during light emission and reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Risley prisms are used to deflect distance measuring light in arbitrary directions, then scanning capability is improved, but optical path length differences occur according to rotation angles of the prisms
Solution Approach 1:
The patent pre-calculates optical path length differences for various rotation angle combinations of the Risley prisms and stores these values in a correction table before actual measurement. During operation, the system simply retrieves the appropriate correction value based on current prism angles, avoiding real-time complex calculations and enabling quick compensation.
Solution Approach 2:
The system continuously monitors the rotation angles of the Risley prisms using detecting units, and uses this feedback information to select the appropriate correction value from the pre-prepared correction table. This closed-loop feedback mechanism ensures that the correction always corresponds to the actual prism positions, maintaining measurement accuracy throughout the scanning range.
2Adaptability or versatility
If rotation angles of Risley prisms are varied to achieve arbitrary light deflection, then scanning flexibility is improved, but optical path length varies causing measurement errors
Solution Approach 1:
The patent performs comprehensive pre-calibration by calculating optical path length differences for all possible rotation angle combinations of the Risley prisms before actual measurement operations. These correction values are stored in a lookup table, allowing the system to quickly compensate for any prism angle configuration without performing complex real-time calculations.
Solution Approach 2:
The system changes the correction parameter based on the rotation angles of the Risley prisms. By selecting different correction values from the correction table corresponding to different prism angle configurations, the system dynamically adjusts for optical path length variations while maintaining measurement accuracy across the full scanning range.
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 measurements in the laser scanner by compensating for optical path length differences, improving the precision of three-dimensional point group data acquisition.
Implementation Method 1
By passing through Risley prisms on the light emitting unit side, a distance measuring light is deflected in an arbitrary direction
Implementation Method 2
By passing through Risley prisms on the light receiving unit side, the optical axis of a reflected distance measuring light is returned onto a light receiving optical axis
Implementation Method 3
the laser scanner measures a round-trip time of the distance measuring light based on a light receiving signal of the light receiving unit to calculate a distance to a measurement point
Data Source
AI summary
A method of correcting a measurement value of a laser scanner includes: in a laser scanner including a light emitting unit, a light receiving unit, a distance measuring unit, an optical axis deflecting unit having at least a pair of prisms deflecting a distance measuring light and a reflected distance measuring light, and an emitting direction detecting unit detecting a deflection angle and an emitting direction of the distance measuring light from the optical axis deflecting unit, (a) measuring a distance to a measurement point, (b) detecting rotation angles of the prisms, and (c) obtaining, based on rotation angles of the prisms, a true distance measurement value corrected for a length of an optical path length difference in light emission and/or light reception caused according to the rotation angles of the prisms by subtracting the optical path length difference from a distance measurement value of the distance measuring unit.