nanomefos non-contact measurement machine for...
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NANOMEFOS Non-ContactMeasurement Machine for Aspheric and Freeform Optics
Rens Henselmans, G. Gubbels, C. van Drunen, B. van Venrooy, J. Leijtens
TNO Science & Industry
ICSO 20102
Contents
• Introduction• TNO Freeform program• NANOMEFOS machine• Results• Conclusion
ICSO 20103
TNO Opto-mechanical instrumentation
Space instruments• Earth observation
spectrometers• Calibration• Sun sensors• Space Science
Astronomy• Delay lines• Star separators• Adaptive optics
Other application areas• Fiber Bragg gratings• Fusion diagnostics• Medical applications
Semicon• System design• Sensors• Contamination control• Substrate handling• Semicon equipment
Leading customers: ESA, NASA, EADS
Leading customers: ASML, Zeiss, Philips.
Leading customers: ESO, UK-ATC.
Leading customers: EFDA, NS, Defence.
ICSO 20104
TNO Optical WorkshopProduction of specials, single piece, high-precision optics used in designs of TNO and external customers
• Lenses (plano to freeform, up to 500 mm)• Diamond turned mirrors (plano to freeform, up to 500 mm)• Prisms• Gratings• SiC mirrors• Coatings• Bonding and optical contacting
ICSO 20105
Aspherical and Freeform opticsAdvantages:• Eliminate aberrations• Fewer components• Smaller systems• Lower system mass• More design freedom
(optimal or radical designs)
ICSO 20106
TNO Freeform program
Pre-machining(milling/grinding)
Measuring
Coating
Local (corr.) polishing
NANOMEFOSabsolute metrology
Iterative loop
Iterative loop
SPDT with on-machine metrology
Design
Assembly & Alignment
ICSO 20107
Machine characteristics
• Universal (from flat to freeform, convex to concave)• Large measurement volume ( 500 x 100 mm)• High accuracy (30 nm, 2)• Non-contact• Fast (minutes)
ICSO 20108
Concept
R-stage
Spindle
-axis
Z-stage
Probe
Product
Base
Z R
Metrology frame
5 mm
ICSO 20109
Completed machine
ICSO 201010
Machine subsystemsMotion system• All air bearings• Z-stage aligned to vertical base plane • Separate position and preload frames
Metrology system• Interferometers directly onto probe• SiC metrology frame• Capacitive probes around spindle• Short metrology loop
Non-contact probe• 5 mm range• 0.1 nm resolution• 5° acceptance angle with
tilt dependency compensation• > 500 Hz servo bandwidth
ICSO 201011
Testing: Freeform• Flat with sines superimposed• 100 mm, ~2 mm PV• Diamond turned with slow-tool-servo
ICSO 201012
Testing: Stability (stationary)
0 0.02 0.04 0.06 0.08 0.1-10
-5
0
5
10
15Metrology system vs. Probe (5 nm offset added)
Time [s]
Dis
plac
emen
t [nm
]
Metrology systemProbe
0 0.02 0.04 0.06 0.08 0.1-4
-2
0
2
4Error (rms = 0.88 nm)
Time [s]
Erro
r [nm
]
• All stages blocked: 2.8 nm rms vibration• Most vibrations and drift eliminated by metrology system• Noise level: 0.88 nm rms in 0.1 s• Drift: 20 - 100 nm PV in 15 min. (in workshop environment)
ICSO 201013
Testing: Tilted flat
Repeatability: 2-4 nm rms with drift compensation
Flatness 8-9 nm rms at 13 m tilt (uncalibrated)
• 100 mm Zerodur (NMi: 7 nm rms)• 13 µm tilt and 0.73 mm tilt (0.6°)• 1 rev/s = 250 mm/s at probe tip• Drift compensation by radial scan• With tilt dependency compensation
ICSO 201014
Testing: Tilted flat• 100 mm Zerodur (NMi: 7 nm rms)• 13 µm tilt and 0.73 mm tilt (0.6°)• 1 rev/s = 250 mm/s at probe tip• Drift compensation by radial scan• With tilt dependency compensation
Without tilt dependency compensation: 14.4 nm rms and artifact
Probe tilt dependency: 100 nm PV on 0.6°With tilt dependency compensation: 7.8 nm rms
ICSO 201015
Calibration
• Repeatability single nm rms level• Calibration with known artifacts
• Flat• Precision sphere• Optical reference lenses• True square• etc.
• Current uncertainty (estimated):• ~1 µm on radius of curvature• ~5 nm rms in circumferential direction• ~10 nm rms in radial direction
• Limited by accuracy of test objects• Traceability with Dutch Metrology
Institute (VSL) planned
ICSO 201016
Nice pictures…• Centre defect• Polishing toolmarks (mid-spatials) on
asphere (HLEM meeting)• ~50 nm PV (on top of 3000 nm form error)
ICSO 201017
Nice pictures…• Sharp edge measurement• R1700 mm concave mirror• Line-scan with 2 µm point spacing• 100 nm / 2 mm edge slope
100 nm
1 mm
ICSO 201018
Nice pictures…• Ground SiC surface (flat)• Not reflective enough for other methods• Toolmarks
ICSO 201019
• Freeform fabrication test for TropOMI• Sphere, 1 mm off-axis, R110 mm, 20x140mm• 1 mm spacing for surface, 2 µm for scan• Form matches on-axis Zygo measurement• Mid-spatial from defective spindle cooler
Nice pictures…
ICSO 201020
1.4 m
Nice pictures• OTA: Beam expander for ESO VLT (4x)• 380 mm asphere• Pre-polished test blank measurement• Form and raster polishing toolmarks
ICSO 201021
Corrective polishing• NANOMEFOS in closed loop with Zeeko robot• 150 mm R375 convex stainless steel surface• From 419 nm PV to 40 nm PV in 3 runs
Run 0: 419 nm PV Run 1: 201 nm PV
Run 2: 90 nm PV Run 3: 40 nm PV
ICSO 201022
Conclusion• Prototype completed• Nanometer level repeatability on freeforms demonstrated• Machine calibrated and GUI developed• Now applied in projects at TNO Optical Workshop
• Fabrication of own designs• Optics production for customers• Measurements for customers
• TNO Freeform optics value chain completed
