TAG Lens Stabilization via Adaptive Drive Control

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Solution Overview

Problem

High-speed variable focal length lenses, such as tunable acoustic gradient (TAG) lenses, face challenges in maintaining stable operating conditions due to temperature changes and electro-mechanical responses, leading to measurement errors in precision metrology systems.

Innovation Solution

Implementing a method that controls the TAG lens using an imaging drive control configuration during imaging drive mode periods and a regulating adaptive drive control configuration during adaptive drive mode periods, based on monitoring signals, to stabilize the lens's operating state and compensate for differences between the standard and current states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a TAG lens is used to achieve high-speed variable focal length imaging, then imaging speed and focal length modulation capability are improved, but measurement precision deteriorates due to temperature drift and electro-mechanical response variations

Engineering Contradiction:

Improveimaging speedVSAvoidmeasurement precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent implements a feedback control system that continuously monitors the actual resonant frequency of the TAG lens and compares it to a reference frequency. Based on the frequency deviation detected by the monitoring circuit, the control system automatically adjusts the drive signal parameters to compensate for drift, thereby maintaining measurement precision while preserving high-speed imaging capability

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the drive signal parameters (frequency, amplitude, or pulse width) dynamically based on the monitored TAG lens state. By adjusting these parameters in response to temperature drift and electro-mechanical variations, the system maintains optimal focal length modulation performance and measurement accuracy throughout operation

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the TAG lens operates at high resonant frequencies for fast focal length modulation, then productivity is improved, but stability of operating conditions deteriorates due to temperature changes and electro-mechanical response drift

Engineering Contradiction:

ImproveproductivityVSAvoidstability of operating conditions

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent employs periodic monitoring and adjustment cycles where the TAG lens resonant frequency is continuously tracked and the drive signal is periodically recalibrated. This periodic feedback action ensures that productivity is maintained through continuous operation while stability is preserved through regular correction of drift conditions

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system performs self-calibration by using its own monitoring circuit to detect frequency drift and automatically adjusting its drive parameters without external intervention. This self-service capability maintains stable operating conditions during continuous high-speed operation

Inventive Principle:

Principle #25Self-service

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 effectively reduces measurement errors by maintaining the TAG lens at a desired operating state, ensuring precise imaging and dimensional measurements in precision metrology systems.

Implementation Method 1

The sound waves may be created by application of an electrical field at a resonant frequency to a piezoelectric tube surrounding the fluid medium

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The sound waves create a time-varying density and index of refraction profile in the lens' fluid, which modulates its optical power and focal length or focus position

Methodology Applied

Scientific EffectAcoustic radiation pressure: Acoustic Radiation Pressure

Implementation Method 3

The sound waves create a time-varying density and index of refraction profile in the lens' fluid, which modulates its optical power and focal length or focus position

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 4

A TAG lens is a high speed VFL lens that creates a lensing effect using sound waves in a fluid medium. The sound waves may be created by application of an electrical field at a resonant frequency

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentEP3454546B1Stabilizing operation of a high speed variable focal length tunable acoustic gradient lens in an imaging system

Publication Date: 2022.04.27 MITUTOYO CORP

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AI summary

A method is provided for operating an imaging system to maintain a tunable acoustic gradient (TAG) lens at a desired operating state. In a first step, the TAG lens operates using a standard imaging drive control configuration (e.g., a standard drive voltage and duration) during a plurality of imaging drive mode time periods, to achieve a standard imaging state of the TAG lens. In a second step, the TAG lens operates using a regulating adaptive drive control configuration during a plurality of regulating adaptive drive mode time periods, wherein at least one of a different respective TAG lens drive voltage and a different respective TAG lens drive duration is used for different respective regulating adaptive drive mode time periods, based on a monitoring signal that is indicative of a difference between the standard imaging state and a current operating state of the TAG lens.