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AMULETAdvanced Metrology Using
LasEr Tracers
John Dale
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Project Aim
• To take Frequency Scanning Interferometry (FSI) from the lab into a product
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Frequency Scanning Interferometry (FSI) Absolute measurements
• Used for several projects in Oxford– ATLAS– LiCAS– MONALISA
• Ratio of phase advance is equal to the ratio of the lengths
• Reference interferometer is an absolute length scale– Can determine D if L known
• Scalable– Any number of measurement
interferometers
Tunable Laser
Reference Interferometer: L
Measurement Interferometer: D
Measurement Interferometer: D2
Time
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Intensity
Intensity
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Project Tasks• Improve FSI Technique
• Practicality• Stability• Traceability
• Implement FSI in a laserTRACER
• Reduce equipment cost
• Simultaneous multiple length-measurements
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LaserTRACER• Developed by NPL, PTB and
marketed by Etalon AG
– A self tracking laser interferometer
– Automatically follows retro reflector
– Uses differential interferometry with a frequency stabilised laser
Frequency StabilisedLaser
Time
Intensity
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Why Absolute Measurement?• Differential measurement
– laserTRACER tracks retro reflector
• If Absolute measurement system added– No problems with beam breaks
– Switch from one target to the next
– Divergent beam allows simultaneous measurements
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Current Reference Interferometers
• Evacuated folded path reference interferometers– Bulky– Expensive– Difficult to thermally stabilise
• We require– Compact– Can be thermally stabilised– Long term stability
1.2m
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Compact fibre reference interferometer
• Fibre Reference Interferometer– Compact (Coiled)– Cheaper– Dispersion
• Experimental Prototype under construction– Fluid bath – Insulated– Temperature monitored
• Optical length with submicron stability
• To be developed into a product
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LaserTRACER Implementation• Install into LaserTRACER head
• Take advantage of:– Tracking capabilities– Stabilised construction– Market presence
• Many possible configurations
• Multiple measurement interferometers
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Reduced Laser Cost
• Working with laser manufacturers – Produce simpler stripped down frequency
scanning lasers.– Lasers which better suit FSI
• Laser is significant cost, reduction could open other markets.
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Why are they useful• Particle Accelerator/Detector Alignment
• CMM and CNC Calibration– Require calibration 1-4 times per year– With absolute measurement capabilities, calibration much
quicker
• Combined CMM and CNC machines.– Absolute distance measurements capability– Especially interesting at large machines (20-30m)– Small machines if cost reduced.
• Metrology assisted assembly– Fitting of aeroplane wings
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Summary
• Project will lead to a product: FSI enhanced laserTRACER
• Generate Intellectual property
• NPL and Etalon AG have established market presence
• laserTRACER has an established customer base
• On the market in 4-5 years