Confocal Optical Protractor Using Vortex Beams for 3-Axis Angle Measurement
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Solution Overview
Problem
Current methods for measuring roll, pitch, and yaw angles are limited in precision and range, particularly for roll angles, and often require complex setups or mechanical contact, which is problematic for large or curved surfaces and environments like 3D printing and clean rooms.
Innovation Solution
A confocal optical protractor system utilizing a spiral phase plate resonator (SPPR) device generates an optical vortex beam that is reflected off an element, allowing for non-contact measurement of roll, pitch, and yaw angles with high precision, using a tunable laser source and a processor to analyze the intensity pattern projected onto a detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical protractors are used for non-contact angle measurement, then contact with the surface is required, but this is detrimental for applications requiring non-contact measurement and for curved surfaces
Solution Approach 1:
The patent replaces mechanical protractors and autocollimators with an optical system using a spiral phase plate resonator that generates optical vortex beams. This substitution eliminates mechanical contact requirements while maintaining high measurement precision through optical interference patterns that can measure angles on both flat and curved surfaces non-contactly.
2Measurement precision
If autocollimators are used to measure pitch and yaw angles with high precision, then the measurement range is limited and complex arrangements are required for roll angle measurement
Solution Approach 1:
The spiral phase plate resonator system is designed to measure all three Euler angles (roll, pitch, and yaw) using a single optical configuration. The optical vortex beam generates intensity patterns that encode all angular information, allowing one device to perform multiple measurement functions that traditionally required separate autocollimators and complex optical arrangements.
3Reliability
If mechanical devices with movable parts are used for angle measurement, then the system is compact, but the probability of failure increases during long-term operation
Solution Approach 1:
The patent eliminates all movable mechanical parts by using a fixed spiral phase plate resonator that generates optical vortex beams. The measurement is achieved through optical interference patterns rather than mechanical scanning or moving components, dramatically improving reliability for long-term operation in harsh environments while maintaining a compact form factor.
4Measurement precision
If the radius of the protractor is increased to measure smaller angles in confined spaces, then measurement precision improves, but the size of the protractor increases making it problematic for confined spaces
Solution Approach 1:
The patent transitions from mechanical angular ticks on a 2D protractor surface to optical interference patterns in the spatial domain. The spiral phase plate creates concentric ring patterns where the radial intensity distribution encodes angular information, allowing high precision measurement of small angles without increasing the physical size of the measurement device.
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
The system provides accurate, non-contact measurement of angles on static or rotating surfaces, including curved ones, with enhanced precision and range, suitable for harsh environments and applications like aerospace and 3D printing, without the need for mechanical parts or complex optical arrangements.
Implementation Method 1
one of the reflective surfaces includes a spiral step index that causes multiple reflected field amplitudes having different phases to be combined and generate an optical vortex intensity pattern
Implementation Method 2
The SPPR device includes opposing reflective surfaces that reflect the laser beam back and forth in the device
Implementation Method 3
a lens being responsive to and projecting the first split measurement beam onto the element and being responsive to a reflected beam from the element. The protractor further includes a measurement detector responsive to the reflected beam from the element, where the reflected beam is imaged by the lens onto the measurement detector
Data Source
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AI summary
A method for measuring pitch, yaw and roll angles of an element, said method comprising: providing a frequency tunable laser beam; directing the laser beam into a spiral phase plate resonator, SPPR, device, said SPPR device including opposing reflective surfaces that reflect the laser beam back and forth in the device, wherein one of the reflective surfaces includes a spiral step index that causes multiple reflected amplitudes having different phases to be combined and generate an optical vortex intensity pattern defined by the phases of the multiple amplitudes, where the intensity pattern includes a singularity centroid and four radial light peaks; reflecting the laser beam off of the element after it has propagated through the SPPR device so that the laser beam is directed onto a camera that generates images of the optical vortex intensity pattern; determining a location of the centroid in the images generated by the camera; determining integrated counts along a radial direction from the centroid in the images generated by the camera as a function of beam roll angle; determining a location of the radial light peaks in the images generated by the camera using the integrated counts; changing the frequency of the laser beam to rotate the radial light peaks in the optical vortex intensity pattern in the images generated by the camera; estimating the roll angle of the element from the change in frequency that rotated the optical vortex intensity pattern; determining the pitch angle of the element by a shift of the vortex intensity pattern in one plane in the images generated by the camera; and determining the yaw angle of the element by a shift of the vortex intensity pattern in a plane orthogonal to the one plane in the images generated by the camera.