TAG Lens Imaging System for High-Speed 3D Metrology

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Solution Overview

Problem

Conventional machine vision inspection systems face limitations in achieving high-speed 3D measurement and extended depth-of-field imaging, particularly due to mechanical complexities and inaccuracies associated with mechanical translation of optical components, which are slow and detrimental to precision measurements.

Innovation Solution

A tunable acoustic gradient (TAG) lens imaging system is operated using a smart lighting pulse control routine/circuit (SLPCRC) that periodically modulates the focus position without adjusting the spacing between elements, allowing for high-speed 3D measurement and extended depth-of-field imaging by activating points from focus (PFF) and extended depth of focus (EDOF) modes, respectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If mechanical translation of optical components is used to achieve extended depth of field, then depth of field is extended, but measurement speed decreases and precision is compromised

Engineering Contradiction:

Improvemeasurement precisionVSAvoidmeasurement speed

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent replaces mechanical translation of optical components with acoustic field manipulation. Specifically, it uses acoustic radiation pressure to dynamically adjust the focal length of a lens, enabling rapid focus changes without mechanical movement. This substitution eliminates the mechanical complexity and inertia that limit speed and precision in conventional systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state of the lens by using acoustic fields to dynamically adjust its focal length parameter. By controlling the acoustic pressure distribution within the lens, the focal length can be rapidly modified without mechanical translation, achieving both high speed and precision in measurement operations.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If mechanical translation of optical components is used to collect image stacks, then extended depth of field is achieved, but device complexity increases

Engineering Contradiction:

Improvedepth of fieldVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical translation system with an acoustic field-based focal length adjustment mechanism. This substitution eliminates moving parts and mechanical linkages, significantly reducing device complexity while maintaining the ability to achieve extended depth of field through acoustic pressure control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If mechanical translation is used for autofocus operations, then focus adjustment is achieved, but operation speed is limited

Engineering Contradiction:

Improveautofocus operationVSAvoidautofocus speed

Core Design Contradiction:

Ease of operationVSSpeed

Solution Approach 1:

The patent replaces mechanical autofocus translation with acoustic field manipulation to adjust focal length. This enables rapid focus adjustment by changing the acoustic pressure distribution within the lens, achieving autofocus speeds limited only by the acoustic response time rather than mechanical movement capabilities.

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 rapid acquisition of image stacks for Z-height coordinate mapping and extended depth-of-field images, significantly improving measurement speed and accuracy while maintaining precision, with the ability to process images in less than 1 second or 250 milliseconds.

Implementation Method 1

Methodology Applied

Scientific EffectAcoustic radiation pressure: Acoustic Radiation Pressure

Data Source

PatentUS10812701B2High-speed tag lens assisted 3D metrology and extended depth-of-field imaging

Publication Date: 2020.10.20 MITUTOYO CORP

AI summary

A method is provided for operating a tunable acoustic gradient (TAG) lens imaging system. The method includes: (a) providing a smart lighting pulse control routine/circuit (SLPCRC) that provides a first mode of exposure control corresponding to a points from focus (PFF) mode of the TAG lens imaging system and a second mode of exposure control corresponding to an extended depth of focus (EDOF) mode of the TAG lens imaging system; (b) placing a workpiece in a field of view of the TAG lens imaging system; and (c) periodically modulating a focus position of the TAG lens imaging system without macroscopically adjusting the spacing between elements in the TAG lens imaging system, wherein the focus position is periodically modulated over a plurality of focus positions along a focus axis direction in a focus range including a surface height of the workpiece, at a modulation frequency of at least 30 kHz.