Fresnel Diffraction Curvature Measurement for Micro-Cantilevers
Solution Overview
Problem
Current methods for measuring surface curvature, particularly of micro-cantilevers, face challenges in accurately determining curvature parameters without overlapping images from neighboring surfaces and in avoiding cross-talk, especially when measuring arrays of micro-cantilevers.
Innovation Solution
The method involves forming a defocused image through Fresnel diffraction of electromagnetic radiation reflected from the surface, allowing for the determination of surface curvature by calculating a scaling factor using the measured image size and a predetermined formula, thereby avoiding overlap and cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a focused image is used for measurement, then image resolution is improved, but overlapping images from neighboring surfaces occur causing cross-talk
Solution Approach 1:
The patent transitions from measuring in the focused image plane to measuring in the defocused plane through Fresnel diffraction. By moving the measurement to a different dimensional space (the diffraction pattern space rather than the direct image space), the method achieves both resolution and isolation of neighboring surfaces simultaneously.
Solution Approach 2:
The patent changes the focusing parameter of the optical system from focused to defocused state. This parameter change transforms the imaging mode from direct geometric optics to Fresnel diffraction regime, which provides inherent spatial separation for curvature measurement while avoiding cross-talk from adjacent surfaces.
2Reliability
If Fresnel diffraction is used to form defocused images, then cross-talk between neighboring surfaces is avoided, but measurement complexity increases
Solution Approach 1:
The patent utilizes the natural Fresnel diffraction phenomenon that occurs when light reflects from a curved surface and propagates to a defocused plane. The system lets the physics do the work of separating neighboring surface images automatically, without requiring complex mechanical or optical intervention for isolation.
Solution Approach 2:
The patent replaces complex mechanical alignment systems and physical isolation mechanisms with an optical field-based solution. By using Fresnel diffraction patterns, the method substitutes mechanical complexity with optical field manipulation, achieving cross-talk avoidance through wave optics rather than mechanical means.
3Measurement precision
If conventional interference patterns are used for curvature measurement, then measurement capability is achieved, but absolute curvature values cannot be determined
Solution Approach 1:
The patent changes the measurement parameter from relative interference fringe shifts to absolute diffraction pattern scaling. By measuring the scaling factor of the Fresnel diffraction pattern, which has a direct mathematical relationship with absolute curvature values, the method recovers the lost absolute information while maintaining measurement precision.
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 enables precise measurement of surface curvature by forming a non-overlapping defocused image, allowing for accurate calculation of curvature parameters without requiring precise alignment or knowledge of the physical dimensions of the cantilevers, thus improving measurement accuracy and simplifying the process.
Implementation Method 1
forming an intensity distribution defined by Fresnel diffraction, wherein said intensity distribution is formed by electromagnetic radiation which has been reflected from a surface
Implementation Method 2
The defocused image may be formed by refracting (e.g: using a refracting element such as a lens) electromagnetic radiation which has been reflected from the surface
Data Source
Figure 1
Figure 2a~2d
Figure 3~4
AI summary
A method of measuring surface curvature comprises forming an intensity distribution defined by Fresnel diffraction, wherein said intensity distribution is formed by electromagnetic radiation reflected from a surface, obtaining data for the intensity distribution and determining information relating to the curvature of the surface using the obtained data.