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TutorialSelection of Vibration Isolators

Masaki HosodaDec. 7, 2009

OPTI 521

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Contents

PurposeMotivationTwo types of Vibration Isolation

Passive Vibration IsolationActive Vibration Isolation

Summary

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Purpose of this presentation

Let you knowhow vibration isolation workshow to select vibration isolatorsexamples of application

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Motivation

Vibration Isolation is important forOptical measurementsOptical fabricatons

From Zygo, GPI serieshttp://www.zygo.com/?/met/interferometers/gpi/flashphase/

From TMC, STACIS

http://www.techmfg.com/appnotes/SematechAppnote.htm

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Two types ofVibration Isolation

Passive Vibration IsolationMass, Spring, and DamperCan isolate high frequency (5Hz~)

Active Vibration IsolationMass, Spring, Damper, and Feedback or FeedforwardCan isolate low frequency (~5Hz)+ high frequency

From TOKKYOKIKIhttp://www.tokkyokiki.co.jp/technology/technology_a.html

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Passive Vibration Isolation2

1 12n

C

k Cfm Cπ

⎛ ⎞⎛ ⎞⎜ ⎟= − ⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠

C/CC is Critical damping ratio CR

•You want fd/fn•fd is defined.•Then fn should•C/CC should•k should•m should

Advantage•Low costDrawback•Amplification Region•Not stable.

From Barry isolators selection guide.pdf

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Selection ofPassive Vibration Isolator

Determine fd (Disturbing frequency)and Min. fn

2d

nff =

Use direct measurementor Rule of Thumb

From Yoder

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Example ofPassive Vibration Isolator

From THORLAB

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Active Vibration Isolation

Advantage•No Amplification RegionDrawback•Cost•algorism•Need reference

Feedback

Feedback + Feedforward

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Selection ofActive Vibration Isolator

Need correct referenceNeed correct model

Fast responseFeedforward+ Feedback

Slow responsedurable for unexpected disturbance

Feedback

DrawbackAdvantage

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Example ofActive Vibrartion Isolator

Vibration isolation platform

1. Pressure (Force)2. Position3. Velocity

Lithography Stage by Canon

S. Wakui, “Active vibration isolator, exposure apparatus, exposure method and device manufacturing method”United States Patent 6,286,644 B1 (2001)

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Summary

Two types of Vibration IsolationPassive Vibration Isolation

Low cost, works for high frequencyHave amplification region, Not stable

Active Vibration IsolationNo amplification region, works for low freq.Need Algorism and reference