Deflectometry Surface Inspection via Pattern Shifting

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Solution Overview

Problem

Existing surface inspection technologies, such as deflectometry, face challenges in achieving high accuracy, reliability, and cost-effectiveness for universally applicable and fast inspection of surfaces with varying quality parameters, particularly in industrial production settings.

Innovation Solution

A device comprising a screen with a light profile pattern, a holder for sample positioning, an auxiliary lens or mirror, and an image recording unit with an evaluation unit to generate phase images, allowing for precise surface property determination through multiple image recordings and pattern analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the moving speed of the motor vehicle is adjusted accurately to the geometric conditions of the pattern, then the inspection accuracy is improved, but the productivity decreases due to the need for precise speed control

Engineering Contradiction:

Improveinspection accuracyVSAvoidinspection speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent applies dynamics by making the pattern movable relative to the surface being inspected. Instead of moving the vehicle at a precisely controlled speed, the pattern is shifted dynamically across the surface, allowing flexible inspection speed while maintaining measurement accuracy through the relative motion between pattern and surface.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent inverts the traditional approach by keeping the surface stationary and moving the pattern instead of moving the surface through a fixed pattern. This reversal eliminates the need for precise speed control of the inspected object while maintaining inspection accuracy.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If multiple cameras are used to record the surface, then the measurement precision is improved, but the device complexity increases

Engineering Contradiction:

Improvesurface measurement accuracyVSAvoidnumber of cameras

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses a single camera to capture images of the pattern reflected from the surface at different positions. Instead of using multiple cameras to simultaneously capture multiple views, one camera takes multiple images as the pattern moves, creating copies of the surface view from different pattern positions. This reduces device complexity while maintaining measurement precision.

Inventive Principle:

Principle #26Copying

3Measurement precision

If the pattern covers exactly one period of the intensity profile, then the measurement precision is improved, but the inspection area is limited

Engineering Contradiction:

Improvelocal slope determination accuracyVSAvoidinspection area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent maintains continuous useful action by shifting the pattern continuously across the entire surface to be inspected. Instead of limiting inspection to areas covered by a single pattern period, the pattern is repeatedly shifted across different regions, allowing continuous inspection of large areas while maintaining the precision benefits of one-period coverage at each location.

Inventive Principle:

Principle #20Continuity of useful action

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 fast, reliable, and accurate surface inspection with increased height resolution and sensitivity to topographical changes, effectively detecting defects and surface properties across diverse industrial applications.

Implementation Method 1

an auxiliary lens or an auxiliary curved mirror arranged between the screen and the holder for providing a second light profile pattern having areas which form a second spatial intensity profile with a second spatial period when at least a part of the first light profile pattern is passed through the auxiliary lens or is reflected by the auxiliary mirror

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

the first light profile pattern is becoming reflected by the surface

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS10261028B2Device for optically inspecting a surface of a sample

Publication Date: 2019.04.16 CARL ZEISS IND METROLOGY LLC

AI summary

A device for optically inspecting a surface of a sample includes: a screen providing a first light profile pattern formed with lighter and darker areas wherein the areas form a first spatial intensity profile having a first spatial period, a holder for positioning the sample with the surface relative to the first pattern such that the first pattern is reflected by the surface, an auxiliary lens and/or curved mirror arranged between the screen and the holder for providing a second light profile pattern having areas which form a second spatial intensity profile with a second spatial period when at least a part of the first pattern passes the lens or is reflected by the mirror, an image recording unit for receiving an image of the second pattern reflected from the surface of the sample, and an evaluation unit for determining properties of the surface in dependence on the image.