Laser interferometer

Su-Jin Kim, GNU& Xiaoyu Ding

Laser Interferometer

• What’s laser interferometer?• The principle of standard interferometer• Types of interferometers• Applications

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What’s a Laser Interferometer

• Laser Interferometer: – the instrument used for high precision

measurements (distance, angles…. etc.)– it uses interferometry as the basis for

measurement.– it uses the very small, stable and accurately

defined wavelength of laser as a unit of measure.

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Physics Review

• Diffraction

Diffraction of Water Waves

Diffraction is a sure sign that whatever is passing through the hole is a wave.

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Physics Review

• Diffraction of LightLight, just like a water wave, does spread out behind a hole is the hole is sufficiently small.

Light is a electromagnetic wave.

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Diffraction of light Wave

Physics Review

• A Double-Slit Interference Experiment

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Interference of Light

Visible light

Color pattern

Principle of Michelson Interferometer

• Albert Michelson (1852~1931)– the first American scientist to receive

a Nobel prize, invented the optical interferometer.

– The Michelson interferometer has been widely used for over a century to make precise measurements of wavelengths and distances.

Albert Michelson

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Principle of Michelson Interferometer

• Michelson Interferometer1) Separation2) Recombination3) Interference

A Michelson Interferometer for use on an optical table

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Principle of Michelson Interferometer

• Analyzing Michelson Interferometer– The central spot in the fringe pattern alternates

between bright and dark when Mirror M2 moves.

Photograph of the interference fringes produced by a Michelson interferometer.

If we can know the spacing distance of M2 between two sequent central bright spots and the number of central bright spots appeared, then we can calculate how long M2 moved.

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λ/4 -> bright to dark

He Ne

• 632.8 nm wave length is used.

Applications

• Measurement of Distance– 1) frequency stabilized He-Ne laser tube– 2) combination of beam-splitter and retroreflector– 3) a moving retroreflector – 4) detection electronics

Aerotech’s LZR3000 Series Laser Interferometer System

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Applications

• Other Applications– Measure angles, flatness, straightness, velocity

and vibrations, etc.

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Rearrangements of the light paths

Resolution

• XL-80 Laser Measurement System

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References• http://www.aerotech.com/products/engref/intexe.html• http://www.renishaw.com/en/interferometry-explained--7854• http://en.wikipedia.org/wiki/Michelson_interferometer• http://en.wikipedia.org/wiki/Interferometry• PHYSICS FOR SCIENTISTS AND ENGINEERS, Randall D. Knight, 2003.

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Laser interferometer

Su-Jin KimGyeongsang National University

Linear Distance Measurement

The positioning accuracy is measured by comparing the position value displayed by machine with the actual position.

Rectangularity Measurement

Measurement of the rectangularity between the x-axis and z-axis.

Straightness Measurements

Straightness and parallelism measurements with moving board up to 20 mm.

Reference

• http://www.youtube.com/watch?v=VyePASErr5Q Theory

Renishaw

• http://www.youtube.com/watch?v=41Auhp1RTP0