Optical Surface Roughness Measurement Using Refractive Prism
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Solution Overview
Problem
Existing methods for measuring surface roughness, such as stylus-based techniques and speckle pattern analysis, face limitations in resolution and accuracy due to physical constraints and contact damage, and alternative methods like illuminating with collimated radiation at slightly different angles are restricted by the size of beam splitters and mirrors, leading to errors in measurement.
Innovation Solution
An optical surface roughness measurement arrangement using a collimated radiation source and a rotatable refractive optical element, such as an optical prism, to refract the beam at a non-parallel angle, allowing for improved angular precision and reduced error in surface roughness measurement, with a motorized flipper for alignment and a detector for reflected radiation processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a stylus is used to measure surface roughness, then the measurement method is simple, but the resolution is limited to the dimensions of the stylus and contact pressure can damage the surface
Solution Approach 1:
The patent replaces the mechanical stylus-based measurement system with an optical measurement system using collimated radiation and speckle pattern analysis. This substitution eliminates the mechanical contact limitations (stylus dimensions and contact pressure) while maintaining measurement simplicity through non-contact optical fields.
Solution Approach 2:
The patent introduces an optical intermediary (collimated radiation field and resulting speckle pattern) between the measurement device and the surface. This intermediary enables high-resolution measurement without direct mechanical contact, resolving the contradiction between simplicity and precision.
2Adaptability or versatility
If beam splitters and mirrors are used to illuminate the surface at different angles, then the measurement range is extended, but the physical size of components presents a lower limit on the angular difference and introduces measurement errors
Solution Approach 1:
The patent transitions from using large physical beam splitters and mirrors to a compact optical arrangement where collimated radiation passes through a refractive element. This dimensional change in the optical path enables precise angular control without the physical size constraints of traditional components.
Solution Approach 2:
The patent changes the optical parameters by using a refractive element to control the angular separation of beams. This allows precise adjustment of the angular difference between illumination paths without being constrained by the physical dimensions of beam splitters or mirrors, thereby improving angular precision while maintaining extended measurement range.
3Ease of operation
If traditional optical methods are used for large materials, then the setup is practical, but the lower angular limit constraint reduces measurement accuracy
Solution Approach 1:
The patent employs a rotatable refractive optical element that can dynamically adjust the angular separation of illumination beams. This dynamic adjustment capability allows the system to maintain practical operation for large materials while achieving higher angular precision by optimizing the angular difference according to the specific measurement requirements.
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
This approach enhances the measurement range and accuracy of surface roughness by removing the lower angular limit constraint, enabling more precise determination of surface roughness with reduced error, particularly suitable for large materials where traditional methods are impractical.
Implementation Method 1
a refractive optical element rotatably mounted on the arrangement and when optically aligned with the beam of radiation, disposed along the first axis, for refracting the beam along a second axis which is non-parallel with the first axis
Implementation Method 2
a motorised flipper for moving the refractive optical element to optically align the refractive optical element with the beam of radiation along the first axis
Implementation Method 3
a detector which is arranged to detect the radiation reflected off the surface of the material, which was incident upon the surface along the first axis and second axis
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
An optical surface roughness measurement-enabling arrangement and method are disclosed for enabling measurement of the surface roughness of a material. The arrangement comprises an optical radiation source for generating a beam of collimated radiation along a first axis for illuminating the surface of the material with the radiation directed along the first axis, a refractive optical element optically alignable with the beam of radiation for refracting the beam along a second axis which is non-parallel with the first axis, for illuminating the surface of the material with the radiation directed along the second axis and a detector which is arranged to detect the radiation, incident upon the surface along the first axis and second axis, which becomes reflected off the surface of the material. An optical surface roughness measuring arrangement and method are also disclosed for providing a measurement value of the surface roughness.