Optical Protractor Using Spiral Phase Plate Resonator
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Solution Overview
Problem
Current methods for measuring roll angles, especially in large or heavy aerospace parts and 3D printing, face challenges such as mechanical contact, limited precision, and complexity in confined spaces, particularly when dealing with rotating surfaces or curved surfaces, and lack a miniaturized non-contact solution that maximizes precision.
Innovation Solution
An optical protractor system employing a spiral phase plate resonator (SPPR) device generates an optical vortex intensity pattern, allowing non-contact measurement of roll angles and rotation rates using a tunable laser source, reflective surfaces, and a processor to align intensity lines with fiducial points, determining the angle from frequency changes, and calibrating for accuracy in harsh environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical protractor is used to measure roll angle, then measurement can be made on static surfaces, but the mechanical contact with the surface is detrimental for non-contact measurement applications
Solution Approach 1:
The patent replaces the mechanical protractor system with an optical system that uses a laser source, spiral phase plate resonator, and detector to measure roll angles without mechanical contact. The optical vortex intensity pattern is projected onto the surface and detected by a sensor, eliminating all mechanical contact while maintaining measurement capability.
Solution Approach 2:
The patent introduces an optical intermediary (the optical vortex intensity pattern projected by the laser and SPPR device) between the measurement system and the surface. This optical pattern serves as a mediator that allows angle measurement without direct mechanical contact, as the pattern can be projected onto and detected from the surface remotely.
2Measurement precision
If the radius of the protractor is increased to measure smaller angles in confined spaces, then measurement precision improves, but the device size increases making it problematic for confined spaces
Solution Approach 1:
The patent transitions from a two-dimensional mechanical protractor scale to a three-dimensional optical field. The spiral phase plate resonator creates an optical vortex with radial intensity lines that can be detected at various angular positions, allowing precise angle measurement without increasing the physical footprint of the device. The measurement is achieved through the angular distribution of light intensity rather than physical scale markings.
3Measurement precision
If a mechanical protractor with gears is used to amplify precision, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical amplification mechanisms (gears, linkages) with an optical resonance system. The spiral phase plate resonator naturally generates the optical vortex pattern with precise angular characteristics through its resonant modes, eliminating the need for mechanical amplification components while achieving high measurement precision.
Solution Approach 2:
The patent uses changes in optical parameters (wavelength, resonance mode) of the laser-SPPR system to achieve precise angle measurement. By detecting shifts in the optical vortex pattern or resonance conditions, the system can measure small angular changes without requiring mechanical amplification, thereby reducing device complexity while maintaining precision.
4Measurement precision
If conventional optical systems with motorized stages are used to control vortex roll angle, then angle measurement capability is achieved, but device complexity and size increase
Solution Approach 1:
The patent employs a resonant optical system where the spiral phase plate resonator naturally generates and maintains the optical vortex pattern through its resonant modes. This dynamic resonance approach eliminates the need for motorized stages or active control mechanisms, as the system self-adjusts to maintain the measurement pattern, thereby reducing complexity while preserving measurement capability.
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 precise, non-contact measurement of roll angles and rotation rates on static or rotating surfaces with high accuracy, suitable for industrial applications like aerospace and 3D printing, without the need for mechanical parts or complex optical systems, and can be miniaturized for smaller sizes.
Implementation Method 1
a spiral phase plate resonator (SPPR) device that generates an optical vortex intensity pattern
Implementation Method 2
coherent superposition of optical vortices
Implementation Method 3
a tunable laser source, reflective surfaces, and a processor to align intensity lines with fiducial points
Data Source
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AI summary
An optical protractor that employs a spiral phase plate resonator (SPPR) device for measuring a roll angle between two points on a static surface or a rotating surface. The protractor includes a tunable laser source that generates a laser beam. The SPPR device is responsive to the laser beam, and includes opposing reflective surfaces that reflect the beam back and forth in the device, where one of the reflective surfaces includes a spiral step index that causes multiple reflected beams having different phases to be combined as an output beam from the device having an optical vortex intensity pattern defined by the phases of the multiple beams, and where the intensity pattern includes radial light intensity lines. The protractor includes a lens that projects the output beam onto the element and the intensity pattern is detected to measure the roll angle.