Optical Position Measurement Device Using Polarization State Detection
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Solution Overview
Problem
Existing methods for measuring rotational position around a beam of light face limitations in achieving high accuracy and ease of use, particularly in terms of field of view, mechanical motion requirements, and sensitivity to acceleration and polarization effects.
Innovation Solution
A device utilizing a polarized beam of light, a polarizing optic, and a sensor system with a control system to maintain sensor readings, coupled with beam steering platforms and a processor for precise measurement of rotation and translation degrees of freedom, allowing operation over long ranges and independent rotation of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polarization property of light is used to measure rotation about the beam, then measurement capability is extended to include roll angle, but measurement accuracy deteriorates due to sensitivity to beam impingement angles on optical surfaces
Solution Approach 1:
The patent replaces mechanical motion systems with optical field-based measurement. Instead of using mechanical targets that move along known tracks or require precise mechanical positioning, the invention uses the polarization state of light itself as the measurement medium. The polarization property of light is modulated and detected to directly measure roll angle without mechanical components, thereby eliminating sensitivity to mechanical positioning errors while maintaining measurement versatility.
Solution Approach 2:
The patent changes the measurement parameter from mechanical position or intensity-based detection to polarization state detection. By monitoring changes in polarization angle and state rather than mechanical displacements or light intensity, the system achieves immunity to beam impingement angle variations. The polarization parameter remains stable regardless of the angle at which the beam strikes optical surfaces, resolving the accuracy problem while maintaining adaptability.
2Adaptability or versatility
If a moving target is used to determine rotation angles, then three rotational degrees of freedom can be calculated, but the device has limited ability for performing measurements while the probe is moving and requires a large field of view
Solution Approach 1:
The patent eliminates the mechanical moving target system and replaces it with an optical field-based measurement approach. The polarization-modulated light field directly encodes rotational information without requiring physical target movement. This allows the probe to move freely during measurement while continuously acquiring rotational data, as the optical field adapts instantaneously to the probe's position and orientation without mechanical inertia or field-of-view constraints.
3Adaptability or versatility
If polarizing beam splitter and sensors are used to measure roll angle, then rotation about the beam can be measured, but fine resolution is difficult to achieve since the measurement covers a range of 180 degrees
Solution Approach 1:
The patent enhances the measurement parameter by using full polarization state detection rather than simple intensity measurement through a polarizing beam splitter. By detecting both the polarization angle and ellipticity (using Stokes parameters or similar polarization state characterization), the system achieves fine resolution within the 180-degree range. The polarization state provides continuous, high-resolution information that overcomes the limitation of coarse intensity-based detection.
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 accurate measurement of rotational and translational degrees of freedom with improved ease of use and resistance to acceleration, offering enhanced precision and flexibility in optical measurement systems.
Implementation Method 1
A device utilizing a polarized beam of light, a polarizing optic, and a sensor system
Implementation Method 2
a sensor system with a control system to maintain sensor readings
Implementation Method 3
coupled with beam steering platforms and a processor for precise measurement
Implementation Method 4
beam steering platforms
Data Source
AI summary
A device capable of measuring one or more degrees of freedom with respect to a beam of light is described. The angle of rotation around the beam is obtained with a polarized beam of light and a polarizing optic and a sensor. A control system holds a sensor reading to a predetermined value. Therefore as the device is rotated around the beam, the optic will be rotated to maintain the sensor reading and an encoder provides the measurement of the amount of rotation. A position sensing device provides transverse information about the location of the beam and rotation of the device around two other axes. A second position sensing device at a difference distance from the light transmitter allows for the separation of transverse and rotational measurements. Alternately, the transverse measurement can be obtained by a light transmitter capable of making the measurement on a reflected beam.