Abstract

We report a new laser datum system for precision point-by-point profilometry of large curved optical surfaces. The laser datum is sensed by a nulling quadrant photodiode mounted in a flexural system with hybrid actuators, which also carries interferometer reference optics for vertical and horizontal displacement measurement. The flexure characteristics such as cross-talk and hysteresis were investigated. The optimum environmental conditions for the active position-control were studied, and closed-loop control was modeled. The experimental results for compensation accuracy showed a repeatability of ± 4 nm rms, the compensation accuracy of 10 nm (vertical channel) and 20 nm (horizontal channel).

© 2003 Optical Society of America

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References

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  1. CELT, The California Extremely Large Telescope, <a href="http://celt.ucolick.org/">http://celt.ucolick.org/</a>
  2. National Physical Laboratory, NPL and the EURO50 telescope, <a href="http://www.npl.co.uk/length/dmet/euro50.html">http://www.npl.co.uk/length/dmet/euro50.html</a>
  3. OWL, 100 m OWL telescope concept, <a href="http://www.eso.org/projects/owl/owl_design.html">http://www.eso.org/projects/owl/owl_design.html</a>
  4. D.D.Walker et al., �??The primary and secondary mirrors for the proposed Euro50 telescope,�?? Design Study Report (2002).
  5. D. J. Whitehouse, Handbook of surface metrology (IOP, 1995), Chap. 4.
  6. W.T.Estler, �??Calibration and use of optical straightedges in the metrology of precision machines,�?? Opt. Eng. 24, 372-379 (1985).
  7. D.S.Anderson, J.H.Burge, �??Swing-arm Profilometry of Aspherics,�?? in Optical manufacturing and testing, V.J.Doherty and H.Stahl, Proc. SPIE 2536, 169-179 (1995).
    [CrossRef]
  8. P.Z.Takacs, S.-N. Qian and J. Colbert, �??Design of a long-trace surface profiler,�?? in Metrology:Figure and Finish, B.E.Truax, Proc. SPIE 749, 59-64 (1987).
    [CrossRef]
  9. P.Z.Takacs, S.C.K. Feng, E. L. Church, S. -N. Qian, W. -M. Liu, �??Long trace profile measurements on cylindrical aspheres,�?? in Advances in Fabrication and Metrology for optics and large optics, J.B.Arnold and R.E.Parks, Proc. SPIE 966, 354-364 (1989).
    [CrossRef]
  10. S.-N. Qian, W.Jark, P. Z. Takacs, �??The penta-prism LTP: A long-trace-profiler with stationary optical head and moving penta prism,�?? Rev. Sci. Instrum. 66, 2562-2569 (1995).
    [CrossRef]
  11. P.Z.Takacs, �??Significant Improvements in Long Trace Profiler Measurement Performance,�?? in Optics for High-brightness synchrotron radiation beamlinseII, L.E.Berman and J.R.Arthur., Proc. SPIE 2856, 236- 245 (1996).
    [CrossRef]
  12. S.Qian, G.Sostero, P.Z.Takacs, �??Precision calibration and systematic error reduction in the long trace profiler,�?? Opt. Eng. 39, 304-310 (2000)
    [CrossRef]
  13. M. Virdee, �??Non-contacting straightness measurementto nanometer accuracy,�?? Int. J. Mach. Tools Manufact. 35, 157-164 (1995).
    [CrossRef]
  14. K. S. Lee Neville, Yimin Cai, Ajay Joneja, �??High-resolution multidimensional displacement monitoring system,�?? Opt. Eng. 36, 2287-2293 (1997).
    [CrossRef]
  15. K. S. Lee Neville, Yimin Cai, S. F. Wong Alfred, Ajay Joneja, �??Ultra-high-resolution optical monitoring system using a noise cancellation technique,�?? Opt. Eng. 36, 3353-3359 (1997).
    [CrossRef]

Int. J. Mach. Tools Manufact.

M. Virdee, �??Non-contacting straightness measurementto nanometer accuracy,�?? Int. J. Mach. Tools Manufact. 35, 157-164 (1995).
[CrossRef]

Opt. Eng.

K. S. Lee Neville, Yimin Cai, Ajay Joneja, �??High-resolution multidimensional displacement monitoring system,�?? Opt. Eng. 36, 2287-2293 (1997).
[CrossRef]

K. S. Lee Neville, Yimin Cai, S. F. Wong Alfred, Ajay Joneja, �??Ultra-high-resolution optical monitoring system using a noise cancellation technique,�?? Opt. Eng. 36, 3353-3359 (1997).
[CrossRef]

S.Qian, G.Sostero, P.Z.Takacs, �??Precision calibration and systematic error reduction in the long trace profiler,�?? Opt. Eng. 39, 304-310 (2000)
[CrossRef]

W.T.Estler, �??Calibration and use of optical straightedges in the metrology of precision machines,�?? Opt. Eng. 24, 372-379 (1985).

Proc. SPIE

D.S.Anderson, J.H.Burge, �??Swing-arm Profilometry of Aspherics,�?? in Optical manufacturing and testing, V.J.Doherty and H.Stahl, Proc. SPIE 2536, 169-179 (1995).
[CrossRef]

P.Z.Takacs, S.-N. Qian and J. Colbert, �??Design of a long-trace surface profiler,�?? in Metrology:Figure and Finish, B.E.Truax, Proc. SPIE 749, 59-64 (1987).
[CrossRef]

P.Z.Takacs, S.C.K. Feng, E. L. Church, S. -N. Qian, W. -M. Liu, �??Long trace profile measurements on cylindrical aspheres,�?? in Advances in Fabrication and Metrology for optics and large optics, J.B.Arnold and R.E.Parks, Proc. SPIE 966, 354-364 (1989).
[CrossRef]

P.Z.Takacs, �??Significant Improvements in Long Trace Profiler Measurement Performance,�?? in Optics for High-brightness synchrotron radiation beamlinseII, L.E.Berman and J.R.Arthur., Proc. SPIE 2856, 236- 245 (1996).
[CrossRef]

Rev. Sci. Instrum.

S.-N. Qian, W.Jark, P. Z. Takacs, �??The penta-prism LTP: A long-trace-profiler with stationary optical head and moving penta prism,�?? Rev. Sci. Instrum. 66, 2562-2569 (1995).
[CrossRef]

Other

CELT, The California Extremely Large Telescope, <a href="http://celt.ucolick.org/">http://celt.ucolick.org/</a>

National Physical Laboratory, NPL and the EURO50 telescope, <a href="http://www.npl.co.uk/length/dmet/euro50.html">http://www.npl.co.uk/length/dmet/euro50.html</a>

OWL, 100 m OWL telescope concept, <a href="http://www.eso.org/projects/owl/owl_design.html">http://www.eso.org/projects/owl/owl_design.html</a>

D.D.Walker et al., �??The primary and secondary mirrors for the proposed Euro50 telescope,�?? Design Study Report (2002).

D. J. Whitehouse, Handbook of surface metrology (IOP, 1995), Chap. 4.

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Figures (6)

Fig. 1.
Fig. 1.

Schematic diagram of profilometer test bench.

Fig. 2.
Fig. 2.

The diagram of flexure system in the laser datum system.

Fig. 3.
Fig. 3.

Generation of position signal from quardrantdiode electronics: Pvertical=(VA+VC) - (VB+VD), Phorizontal=(VA+VB) - (VC+VD)

Fig. 4.
Fig. 4.

(a) Horizontal (filled square symbol)/vertical (filled circle symbol) displacement of the QD for the vertical (bottom x-axis)/horizontal (top x-axis) flexure movement. (b) Cross-talk and hysteresis of the flexure system after modification.

Fig. 5.
Fig. 5.

Positional compensation model, when the PZT is activated.

Fig. 6.
Fig. 6.

(a) Simulated transient response of the PZT (circle points) to the step disturbance (solid line). (b) Experiment results of position compensation of the datum beam at both channels. The dotted lines are the original position.

Tables (1)

Tables Icon

Table 1. Typical P-V displacements of the laser datum beam on the quadrant diode in three different conditions.

Equations (3)

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Y ( s ) = P ( s ) ( 1 + G ( s ) )
G ( s ) = α β K 1 K 2 K 3
K ( f ) = A dc ( 1 + j f f 1 )

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