Variable Focal Length Lens Phase Offset Calibration

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Solution Overview

Problem

Conventional machine vision inspection systems face limitations in speed and accuracy for Z-height measurements due to the need for physical component movement, which hampers high-speed and high-throughput applications.

Innovation Solution

A variable focal length (VFL) lens system is employed to rapidly modulate focus positions using a tunable acoustic gradient index of refraction lens, synchronized with a phase timing signal, allowing for precise Z-height measurements by compensating for phase offsets, thereby eliminating errors related to phase variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If physical components are moved through a range of Z-height positions to perform measurements, then measurement coverage is improved, but measurement speed deteriorates

Engineering Contradiction:

Improvemeasurement coverageVSAvoidmeasurement speed

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The patent replaces mechanical movement of physical components with acoustic field modulation. A variable focal length lens is controlled by acoustic signals to change its focal position dynamically, eliminating the need for mechanical stage movement or component translation. This substitution of acoustic control for mechanical movement enables rapid focal length changes without the speed limitations of mechanical systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements dynamic focal length adjustment through acoustic control of the variable focal length lens. The lens focal position is continuously modulated in response to acoustic signals, allowing the system to adaptively scan through different Z-height positions dynamically rather than through static mechanical positioning. This dynamic approach enables high-speed measurement across the full Z-height range.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If phase offsets are present in the modulation signal, then measurement accuracy deteriorates, but the patent compensates for this to maintain precision

Engineering Contradiction:

ImproveZ-height measurement accuracyVSAvoidmeasurement consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements feedback through phase offset compensation mechanisms. The system monitors the phase relationship between the modulation signal and the focal position changes, detects any phase offsets, and applies corrective adjustments to the control signal. This feedback loop ensures that phase errors do not accumulate and that measurement accuracy is maintained despite variations in the acoustic control system.

Inventive Principle:

Principle #23Feedback

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 rapid and accurate Z-height measurements without compromising dimensional accuracy, facilitating high-speed and high-throughput inspections by eliminating the need for macroscopic mechanical adjustments and reducing positioning errors.

Implementation Method 1

a variable focal length lens system may include an imaging system, a controller, a focus determining portion and a phase offset compensating portion... the VFL lens may include a tunable acoustic gradient index of refraction lens

Methodology Applied

Scientific EffectGradient index of refraction modulation: Refraction

Implementation Method 2

Methodology Applied

Scientific EffectAcoustic gradient index effect: Acousto-optic Effect

Data Source

PatentUS9736355B1Phase difference calibration in a variable focal length lens system

Publication Date: 2017.08.15 MITUTOYO CORP

AI summary

A variable focal length (VFL) lens system is utilized to determine surface Z-height measurements of imaged surfaces. A controller of the system is configured to control a VFL lens (e.g., a tunable acoustic gradient index of refraction lens) to periodically modulate its optical power and thereby periodically modulate a focus position at a first operating frequency, wherein the periodically modulated VFL lens optical power defines a first periodic modulation phase. A phase timing signal is synchronized with a periodic signal in the controller that has the first operating frequency and that has a second periodic modulation phase that has a phase offset relative to the first periodic modulation phase. A phase offset compensating portion is configured to perform a phase offset compensating process that provides Z-height measurements, wherein at least one of Z-height errors or Z-height variations that are related to a phase offset contribution are at least partially eliminated.