Curvature Measurement of Small Samples Using Laser Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current thin film stress measurement techniques face challenges in accurately measuring curvature radius and stress in small samples, especially at high temperatures, due to limitations in sample size and temperature range, and the complexity of existing optical designs.
Innovation Solution
A system using a laser source, beam expander, grating mask, and CCD camera to create non-parallel laser beams for interference pattern formation, allowing for high-resolution curvature measurement and stress calculation, capable of operating at room temperature and high temperatures, with novel image processing methods to determine curvature radius and stress in small samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional laser beam deflection methods are used to measure curvature radius, then measurement capability is provided, but measurement precision deteriorates for small samples due to diffraction spreading limiting the number of beams to no more than twelve
Solution Approach 1:
The patent segments a single broad laser beam into multiple non-parallel beams by reflecting it off a curved sample surface. This segmentation allows the system to effectively use more than twelve beams for measurement, overcoming the diffraction limit while maintaining a relatively simple optical design with only a single laser source and detector.
Solution Approach 2:
Instead of generating multiple separate laser beams and measuring their deflection, the patent inverts the approach by using a single broad beam that is reflected off the curved sample surface to naturally create multiple non-parallel beams. This inversion simplifies the optical path while achieving the same measurement objective.
2Measurement precision
If a larger distance between detector and sample surface is used to measure larger curvature radius, then measurement accuracy improves, but the apparatus requires larger sample size which is not compatible with laboratory research samples
Solution Approach 1:
The patent transitions from measuring beam deflection in a single dimension to utilizing the curved sample surface as a three-dimensional reflective element. The curved surface transforms a single broad beam into multiple non-parallel beams with different angles, effectively adding angular dimensionality to the measurement and enabling accurate curvature measurement of small samples without requiring large detector-sample distances.
3Temperature
If existing stress measurement techniques are used, then stress evaluation is provided, but temperature capability is limited to up to 500° C. which is insufficient for high temperature processing near or above 1000° C.
Solution Approach 1:
The patent replaces mechanical contact-based or complex optical systems with a non-contact optical measurement system using laser beam reflection. This substitution eliminates temperature constraints associated with physical sensors or complex optical components, enabling operation at high temperatures up to 1000° C. and above while maintaining measurement precision through the simplicity and robustness of the optical design.
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 curvature measurement with high resolution (δ down to 4×10−6) of small samples (5 mm×5 mm) and thermal expansion measurement, overcoming limitations of existing methods by improving measurement accuracy and extending temperature capabilities.
Implementation Method 1
expanding a size of the light beam emitted from the laser source to create a broad laser beam
Implementation Method 2
reflecting the broad laser beam off of a curved surface of the sample; creating a plurality of non-parallel laser beams by passing the reflected broad laser beam through a grating mask or a biprism
Implementation Method 3
using the plurality of non-parallel laser beams to create an interference pattern at a camera image sensor
Data Source
AI summary
Systems and methods for measuring a curvature radius of a sample. The methods comprise: emitting a light beam from a laser source in a direction towards a beam expander; expanding a size of the light beam emitted from the laser source to create a broad laser beam; reflecting the broad laser beam off of a curved surface of the sample; creating a plurality of non-parallel laser beams by passing the reflected broad laser beam through a grating mask or a biprism; using the plurality of non-parallel laser beams to create an interference pattern at a camera image sensor; capturing a first image by the camera image sensor; and processing the first image by an image processing device to determine the curvature radius of the sample.