4D Technology Corporation

Transcription

1 4D Technology Corporation Dynamic Laser Interferometry for Company Profile Disk Shape Characterization DiskCon Asia-Pacific 2006 Chip Ragan

2 Interferometry Basics Two Beam Interference I = I1 +I2 +2 I1I2 cos(α 1 α 2 ) The Leader in Dynamic Interferometry α 1 α 2 α 1 α 2 phase difference between interfering beams = ( 2 π ) (optical path difference) λ TEST SURFACE SOURCE BEAM SPLITTER REFERENCE SURFACE DETECTOR

3 Temporal Phase Shifting Interferometry (PSI) Physical translation of reference surface to generate data. I(x,y) = I 0 + I' cos[φ(x,y)+ φ(t)] I 1 (x,y) = I 0 + I' cos [ φ (x,y)] φ (0.03s) = 0 (0 ) I 2 (x,y) = I 0 - I' sin [φ (x,y) ] φ (0.06s) = π/2 (90 ) I 3 (x,y) = I 0 - I' cos [φ (x,y) ] φ (0.09s) = π (180 ) I 4 (x,y) = I 0 + I' sin [φ (x,y) ] φ (0.12s) = 3π/2 (270 ) (, ) ϕ x y = Tan ( ) ( ) I x, y I ( x, y) I1 x, y I 3 ( x, y) Height (x, y) = λ 4 π ϕ (x, y) Note: Method is camera frame-rate limited Typical acquisition time is msec

4 Dynamic Phase Shift Method The Leader in Dynamic Interferometry Use polarizer as phase shifter LHC ref RHC test Circ. Pol. Beams ( φ) + linear polarizer (α) cos ( φ + 2α) Phase-shift depends on polarizer angle Kothiyal and Delsile, Appl. Opt. V24 n24 p4439 (1985) Kemo, et. al, Appl Opt. V41 n 13 p2448 (2002)

5 Device Architecture The Leader in Dynamic Interferometry Pol. orientation A B Unit Cell Layout Single layer A B Multi-layer A B C D C D Substrate C D Substrate Fabrication Photolithographic single layer method High accuracy matching to pixels Contrast ratio >1000:1 Wavelengths 400nm - >1 micron

6 Phase Sensor Array Array of oriented micropolarizers Polarizer array Matched to detector array pixels α=45, φ=90 α=0, φ=0 Unit Cell α=135, φ=270 α=90, φ=180

7 Tilt Beam Fizeau Test Part Transmission Flat R T 16 Double Polarizer 30 R R T 28 T Birefringent Beam Combiner Phase Camera Test Cavity Collimator Laser Source Note: Alignment Arm not shown Multiple patents pending

8 Static Shape of Al Disk 12.4 micron P-V Interferogram Surface profile Supports all standard analysis parameters for PV, RVA, Flatness, Waviness

9 Dynamic Shape of Al Disk Surface Measurements, 5600 RPM

10 Modal Analysis Configuration Frequency, Phase, Amplitude, Trigger Interval D/A Software Interface Trigger Phase Drive Signal Acquisition Trigger Signal Transducer Amplifier Dynamic Interferometer Test Mirror

11 Modal Analysis Phase Movie 3069Hz Resonance The Leader in Dynamic Interferometry

12 Environmental Testing The Leader in Dynamic Interferometry Figure testing of 300 mm Zerodur mirrors at cryogenic temperatures, Baer & Lotz, SPIE July 2002

13 System Configuration For Glass test Glass L Ref. Fizeau Interferometer collimator Beam splitter T Aperture T T Mask and Detector S 2 S 1 (System can be used on-axis) PBS QWP L source M2 Short Coherence Source L HWP QWP M1 stage Path compensation module

14 Front Side, 95mm Glass Fringes Focused on Top Surface of Glass Disk (S 1 ) Surface referenced to Transmission Flat Measurement is top surface shape. M 1 = S 1

15 Back Side, 95mm Glass Fringes Focused on Back Surface (S 2 ) Measurement is M 2 = ns 2 (n-1)s 1 Back surface (S 2 ) can be calculated by M 2 + (n+1)s 1 n

16 Thickness Variation Difference of S 2 and S 1 Thickness variation map across sample.

17 Al Disk with Short Coherence Short Coherence Dynamic Interferometry provides flexibility for both Al and Glass measurements.

18 Direct Thickness Variation test L Ref. collimator Beam splitter T Aperture T T Mask and Detector source PBS (System can be used on-axis) QWP L M2 L HWP QWP M1 stage Path compensation module Transmission Flat removed Front of Glass Disk used as Reference

19 Direct Thickness Variation Disk clocked approximately 90 from previous measures. Provides direct measure of thickness variation across glass disk.

20 Conclusion Dynamic Interferometry Static Surface Measurement of Aluminum Disks Dynamic Surface Characterization Environmental Chamber Testing Short Coherence Dynamic Interferometry Aluminum Front Side Dynamic Surface Characterization Glass Front Side Back Side Thickness Variation Dynamic Surface Characterization