Aperiodic Interference Pattern Position Measurement
Solution Overview
Problem
Current position measurement systems, such as interferometers, face challenges in accuracy and cost, particularly for large-scale measurements, as they require expensive and complex setups, and are limited by the precision of grating systems, which are expensive and prone to contamination, and have issues with identifying zero distance due to periodic signals and measuring multiple axes simultaneously.
Innovation Solution
A measurement system utilizing a two-dimensional intensity pattern, specifically a translationally aperiodic interference pattern, which allows for precise and accurate measurement of multiple axes with a simpler and cost-effective setup, using a detector that captures a minority part of the pattern, and can operate with a coherent light source to determine position, orientation, and wavelength of electromagnetic radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interferometers are used for position measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical interferometer systems with a simplified optical system using a single diffraction grating and detector. The mechanical alignment complexity of traditional interferometers is substituted by a fixed grating structure that generates interference patterns directly detectable by the sensor, maintaining measurement precision while reducing device complexity.
Solution Approach 2:
The patent extracts the essential interference pattern generation function from the complex interferometer system, isolating it to a single diffraction grating element. By taking out only the critical component needed for pattern generation and using a detector to capture the patterns, the system achieves precise measurement without the full complexity of traditional interferometers.
2Measurement precision
If grating systems are used for position measurement, then measurement accuracy is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent transitions from one-dimensional linear grating systems to two-dimensional diffraction grating patterns that project interference fringes across a measurement volume. This dimensional change allows the grating to encode position information in multiple spatial dimensions simultaneously, reducing the precision burden on any single grating line while maintaining overall measurement accuracy.
Solution Approach 2:
The patent uses composite optical paths with multiple diffraction gratings at different orientations and spacings. By combining multiple gratings with different characteristics, the system achieves high measurement accuracy through the collective interference pattern while each individual grating can be manufactured with relaxed precision tolerances.
3Measurement precision
If periodic interference patterns are used, then measurement sensitivity is improved, but identification of zero distance becomes difficult
Solution Approach 1:
The patent introduces asymmetric elements into the periodic interference pattern system, such as non-symmetric grating configurations or asymmetric detection algorithms. This asymmetry breaks the periodic symmetry that causes zero-distance ambiguity, allowing the system to maintain measurement sensitivity while uniquely identifying the zero distance position through the asymmetric pattern signature.
4Length of stationary object
If large-scale measurement systems are implemented, then measurement range is improved, but cost increases
Solution Approach 1:
The patent uses two-dimensional diffraction grating patterns that extend interference fringes across a large measurement volume. By projecting patterns in multiple dimensions rather than using long linear gratings, the system achieves large measurement range without proportionally increasing grating size or system cost, as the pattern geometry provides scale extension.
Solution Approach 2:
The patent designs a multi-functional system where a single diffraction grating setup can measure positions across large ranges, determine orientations, and identify zero distances simultaneously. This universal approach eliminates the need for multiple specialized systems for different measurement scales, reducing overall cost while maintaining large 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 high-precision, multi-axis measurement with low rotational symmetry, reducing costs and complexity, and maintaining accuracy across large scales without the need for precise alignment or expensive components, while being adaptable for various applications including wavelength and refractive index determination.
Implementation Method 1
uses of electromagnetic interference patterns
Implementation Method 2
A two-dimensional intensity pattern, specifically a translationally aperiodic interference pattern
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
Various uses of visible light interference patterns are provided. Suitable interference patterns are those formed by diffraction from patterns of apertures. Typical uses disclosed herein relate to spatial metrology, such as a translational and/or angular position determination system. Further uses include the analysis of properties of the light itself (such as the determination of the wavelength of the electromagnetic radiation). Still further uses include the analysis of one or more properties (e.g. refractive index) of the matter through which the light passes. Part of the interference pattern is captured at a pixellated detector, such as a CCD chip, and the captured pattern compared with a calculated pattern. Very precise measurements of the spacing between maxima is possible, thus allowing very precise measurements of position of the detector in the interference pattern.