Astigmatic Optical Path for Simultaneous Height and Angle Measurement

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Solution Overview

Problem

Conventional atomic force microscopes face challenges in accurately measuring both translational and angular displacements of a cantilever simultaneously due to the mixing of information in cantilever deformation, leading to inaccuracies that depend on geometric and material characteristics of the cantilever, which vary widely.

Innovation Solution

A system utilizing an optical path mechanism with astigmatism effects, where a laser beam focuses on the object's surface, and reflected light is analyzed by a photo sensor assembly to separate translational and angular displacements through focus error signals and angular signals, allowing for precise non-contact measurement of height and angle variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the beam deflection method is used to measure angular displacement, then angular displacement measurement is enabled, but translational displacement information becomes mixed with angular displacement information and cannot be separated accurately

Engineering Contradiction:

Improveangular displacement measurementVSAvoidtranslational displacement information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent segments the measurement information by using two separate detection methods: the beam deflection method for angular displacement measurement and an interferometer for translational displacement measurement. This segmentation allows each method to measure its specific parameter independently without information mixing, resolving the contradiction between enabling angular displacement measurement and preserving translational displacement information.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If the interferometer is used to measure translational displacement, then translational displacement measurement is enabled, but angular displacement measurement becomes impossible

Engineering Contradiction:

Improvetranslational displacement measurementVSAvoidangular displacement information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent divides the measurement functions between two instruments: the interferometer is dedicated to translational displacement measurement while the beam deflection method handles angular displacement measurement. This functional segmentation enables each method to excel at its specific measurement type without the limitations of trying to perform both measurements with a single method.

Inventive Principle:

Principle #1Segmentation

3Ease of operation

If conventional AFM measurement system is used, then measurement capability is provided, but measurement accuracy depends on cantilever geometric and material characteristics which vary widely

Engineering Contradiction:

Improvemeasurement capabilityVSAvoidmeasurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical cantilever-based measurement system with an optical measurement system using laser beams, interferometers, and position-sensitive detectors. This substitution eliminates the dependency on cantilever geometric and material characteristics, providing universal measurement capability that does not require calibration specific to each cantilever's physical properties.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 simultaneous and precise measurement of translational and angular displacements, improving the accuracy and cost-effectiveness of surface profiling, and is easy to operate, capable of integration with closed-loop control systems and micro electromechanical systems.

Implementation Method 1

an optical path mechanism using the astigmatism as its measurement configurations

Methodology Applied

Scientific EffectAstigmatism:

Implementation Method 2

a laser beam passes through a lens assembly and focuses on the surface of the object to be measured

Methodology Applied

Scientific EffectOptical focusing: Focusing

Implementation Method 3

the reflected light passes through said lens assembly and an astigmatic lens

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 4

projects onto a photo sensor assembly comprising a plurality of photo sensors, forming a light spot thereon

Methodology Applied

Scientific EffectPhotoelectric detection: Photoelectric Effect

Data Source

PatentUS7247827B1System for measurement of the height, angle and their variations of the surface of an object

Publication Date: 2007.07.24 ACAD SINICA

AI summary

A system for measurement of the height, angle and their variations of the surface of an object comprises a measurement module and an astigmatic optical path mechanism. The optical path mechanism makes a laser beam pass a lens assembly and focus on an object. The reflected light passes the lens assembly and an astigmatic lens, arriving at the photo sensor assembly, forming a light spot thereon. The translational displacements of the object are measured by the variations in shape of the light spot on the photo sensors. The angular displacements of the object are measured accordingly by the movement of the light spot on the photo sensors.