Rotation Angle Detection via Optical Projection
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Solution Overview
Problem
Conventional rotation angle detecting apparatuses for surveying instruments are expensive and require high precision in assembly, making them costly and difficult to set up accurately, especially for mini total stations that demand high angular accuracy over short distances.
Innovation Solution
A rotation angle detecting apparatus using a simple structure with an angle detection pattern projected onto an image sensor, allowing for accurate detection of rotational displacement without the need for expensive encoders, and enabling correction for tilt errors through focal length calculations, thus reducing manufacturing costs and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional encoder is used for rotation angle detection, then high measurement precision is achieved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent replaces the mechanical encoder system with an optical projection system consisting of a condenser lens, angle detection pattern, and image sensor. This substitution eliminates complex mechanical components while achieving equivalent or superior measurement precision through optical field analysis.
Solution Approach 2:
The invention creates an optical copy of the angle detection pattern through the condenser lens projection onto the image sensor. This optical copying mechanism allows for precise angle measurement without requiring direct mechanical contact or complex encoder structures, simplifying the overall system.
2Reliability
If high precision assembly is required for rotation shaft and bearing holder, then rotation accuracy is improved, but ease of manufacture deteriorates
Solution Approach 1:
The angle detection pattern is designed to self-align with the optical axis of the condenser lens through its radial line segment configuration. This self-aligning mechanism compensates for assembly variations, allowing the system to achieve high rotation accuracy without requiring extremely precise manual assembly of the rotation shaft and bearing holder.
Solution Approach 2:
The invention changes the detection parameter from mechanical position encoding to optical pattern recognition. By detecting the rotational angle through image processing of the projected pattern rather than mechanical encoder readings, the system becomes less sensitive to assembly precision variations while maintaining high measurement accuracy.
3Measurement precision
If expensive encoders are used for angle detection, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive, complex encoders with inexpensive optical components (condenser lens, simple angle detection pattern, and image sensor). These simpler components can be manufactured at lower cost while achieving the same measurement precision, making the system economically viable for mass production in mini total stations.
Solution Approach 2:
The invention substitutes the mechanical encoder system with an optical field-based detection system. This substitution eliminates the need for expensive precision-machined encoder discs and read heads, replacing them with optically manufactured patterns and digital image processing, thereby significantly reducing manufacturing costs while maintaining or improving measurement precision.
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
Enables highly accurate angular detection with reduced manufacturing costs by eliminating the need for expensive encoders and allowing for initial setting flexibility, even with lower assembly precision, thereby enhancing the mobility and affordability of mini total stations.
Implementation Method 1
a condenser lens which is provided in the bearing holder space and projects the angle detection pattern onto the image sensor
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
A rotation angle detecting apparatus comprises a bearing holder 3, a rotation shaft 1 rotatably supported by said bearing holder, a shaft portion space 4 formed in said rotation shaft, a bearing holder space 5 formed in said bearing holder, a first condenser lens 7 which is accommodated in said shaft portion space and has an optical axis 9a that coincides with a center line of said rotation shaft, a second condenser lens 8 which is provided in said bearing holder space and also provided on an extension of a center line of said rotation shaft, an angle detection pattern 11 provided at a focal position of one of said first condenser lens and said second condenser lens, and an image sensor 12 provided at a focal position of the other of said first condenser lens and said second condenser lens, wherein said image sensor detects a projection image of said angle detection pattern projected onto said image sensor, and a displacement of said projection image involved by the rotation of said rotation shaft is detected.