Spherical Shape Measurement Using Dual-Axis Rotation and Stitching
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Solution Overview
Problem
Conventional techniques are limited in measuring the shape of an entire sphere, particularly around the shaft and held portions, and cannot accurately measure areas beyond half of the sphere due to restricted measurement ranges and positional displacement errors.
Innovation Solution
A method and apparatus that freely rotate the sphere, allowing overlapping partial measurements to be stitched together, with a detachable sphere support table and adjustable positions for comprehensive measurement, including a mechanism for re-holding the sphere to cover the entire surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the sphere is held by a fixed shaft for measurement, then the measurement device structure is simple, but the measurement range is limited to approximately half of the sphere and areas around the shaft cannot be measured
Solution Approach 1:
The invention transforms the static fixed-shaft holding method into a dynamic dual-axis rotation system. The sphere can now rotate about a first rotation axis (θ axis) and a second rotation axis (φ axis) that is orthogonal to the first, enabling the measurement beam to access the entire spherical surface including areas previously obscured by the shaft.
Solution Approach 2:
The invention adds a second rotational dimension (φ axis orthogonal to the θ axis) to the measurement system. This dimensional addition allows the measurement beam to approach the sphere from multiple angular directions, completely eliminating the blind zones that existed with single-axis rotation or fixed-shaft holding.
2Area of stationary object
If the measurement position is changed by rotating the sphere about orthogonal axes, then the measurement range is extended, but positional displacement errors occur
Solution Approach 1:
The invention incorporates position detection means that continuously monitor the angular positions of both the θ and φ rotation axes. This feedback information is used by the control means to calculate and compensate for any positional displacement errors, ensuring that the sphere's position and orientation are accurately known throughout the measurement process.
Solution Approach 2:
The invention replaces purely mechanical positioning with a hybrid system that uses optical or electromagnetic position detection and computational control. Instead of relying solely on mechanical precision of the rotation axes, the system uses detection means and control algorithms to achieve and maintain accurate positioning.
3Area of stationary object
If the entire sphere surface is measured by rotating about multiple axes, then comprehensive coverage is achieved, but the measurement time increases
Solution Approach 1:
The invention enables continuous measurement by rotating the sphere about the θ axis while simultaneously adjusting the φ axis angle. The measurement beam continuously scans the spherical surface without interruption, and the dual-axis rotation allows the system to progress through different angular positions efficiently, covering the entire surface in a continuous operation rather than discrete steps.
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 high-accuracy measurement of the entire sphere by overcoming limitations in measurement range and positional displacement errors, ensuring comprehensive coverage and precision.
Implementation Method 1
measures the surface shape of a sphere (10) by using a reference spherical surface (22) having a spherical shape and comparing the wavelength of laser light (26) generated by a laser light source (24), which is used as a yardstick, with the reference spherical surface (22)
Data Source
AI summary
In a spherical shape measurement method for measuring a surface shape, a sphere to be measured is made freely rotatable. The partial spherical shape of each measurement area, which is established so as to have an area overlapping with another measurement area adjacent to each other, is measured at each rotation position, and the surface shape is measured by joining the partial spherical shapes of the measurement areas by a stitching operation based on the shape of the overlapping area. In the state of detaching the sphere from the sphere hold mechanism to which the sphere is freely attachable and detachable, the sphere support table holds the sphere. The sphere is re-held at a different position, so that the shape of the entire sphere can be measured with high accuracy.