LAO Activities Relevant To Keck NGAO Donald Gavel NGAO Team Meeting 6

LAO Activities Relevant To Keck NGAO

Donald Gavel

NGAO Team Meeting 6

April 26, 2007

Don Gavel: Keck NGAO meeting April

25, 2007 1

Outline

• The Laboratory for Adaptive Optics

• MEMS deformable mirror development

Open loop control experiments

• LGS tomography testbed (LTAO testbed)

Tomographic error model anchoring to laboratory experiment

• Pyramid wavefront sensor

Experimental validation of theory using a “very good” pyramid


25, 2007 2

LAO Facility in Thimann Labs Building, UCSC


25, 2007 3

Laboratory for Adaptive Optics

Claire Max, Principal Investigator

Joseph Miller, co-Investigator

Jerry Nelson, co-Investigator

Donald Gavel, Laboratory Director

• A permanent facility within the UCO/Lick Observatory located at the UC Santa Cruz campus

• Presently funded by a grant from the Gordon and Betty Moore

Foundation

LAO Goals

1. Develop Adaptive optics technology and methods for the next generation of extremely large ground-based telescopes

2.

Develop and build a planet finder instrument using “extreme” adaptive optics technology

3. Develop, test, and evaluate new components and key technologies for adaptive optics

4. Provide a laboratory where students and postdocs will be trained in adaptive optics design, modeling, and implementation


25, 2007 4

MEMS DM Flattening and Control to

Kolmogorov Phase Aberration


25, 2007 5

MEMS surface deflection depends on linear combination of electrostatic and spring forces

• Mirror surface:

• Nonlinear in displacement

• Linear in forces

• Net force deflecting top mirror plate depends on:

• Electrostatic force pulling actuator down

• Spring force restoring actuator up

Video credit Daren Dillon , LAO @ UCSC.

MEMS courtesy Boston Micromachines Corp.

Video created with Veeco interferometric microscope.


25, 2007 6

Openloop “Go-to” Control

(see Morzinski et. al., this meeting, paper # 6467-15)

To within

17 nm surface


25, 2007 7

Electrostatic and spring force look-up tables are calibrated empirically

• Actuate neighbors only

• Set central actuator to voltage = 0V

• Then f

E

= 0

•

Thus f

P

(w,0) = f

S

(w) and measure central actuator displacement

• Obtain spring force alone as f

S

= f

P

• Repeat with varying voltages on the central actuator

• Thus giving f

E

(w,v) = f

P

(w,v) - f

S

(w)


25, 2007 8

Found relation between displacement and spring force;

& relation btwn. displacement, voltage, and plate force voltage on central actuator / V displacement / nm

• Relation between spring force

•

Relation between voltage, displacement (via neighboring and displacement on central actuator voltage), and plate force

 electrostatic force


25, 2007 9

Sinusoid applied to MEMS in open-loop.

Residuals: 16nm rms; 85nm P-V

•

Applied sinusoid:

• Amplitude 300nm (600nm P-V)

• Wavelength 9 actuators

•

Measured residuals

Applied sinusoid.

P-V = 600nm

Measured sinusoid.

P-V = 550nm


25, 2007

Residuals.

P-V = 85nm

RMS = 16nm

10

Gaussian applied to MEMS in open-loop.


•

Applied gaussian:

• Height 390nm

• FWHM 56nm

•

Measured residuals

Applied gaussian.

P-V = 390nm

Measured gaussian.

P-V = 370nm


25, 2007

Residuals.

P-V = 140nm

RMS = 12nm

11

Kolmogorov atmosphere applied to MEMS in open-loop.


•

Applied Kolmogorov atmosphere phase screen

•

Measured residuals

Applied Kolmogorov.

P-V = 540nm

Measured Kolmogorov.

P-V = 480nm


25, 2007

Residuals.

P-V = 99nm

RMS = 16nm

12

LTAO/MCAO/MOAO Testbed

Deformable Mirrors (SLMs)

Kolmogorov Atmosphere phase aberrator plates

Interferometer reference beam

Open loop WFS path

QPI

Interferometer

Ref Flat

SLM

NGS LGS

Guide star fibers

Far Field Camera

• Up to 8 wavefront guide stars and 4 tip/tilt stars

• 10,000 DOF per DM (100x100 subaperture Hartmann sensors)

• Up to 3 DMs (MCAO) or 1 DM and open loop WFS path (MOAO)

• 5 Hz sample & control rate

• Moving phase plates (wind)

• Moving LGS fibers in z to simulate LGS elongation, or laser pulse

Hartmann Wavefront Sensors


25, 2007

Configurable guide star constellation

13

Similarity Parameters Map the Testbed to an On-Sky Case

Gemini 5 LGS constellation on 42.5 arcsec radius

Laboratory for Adaptive Optics

Scaling and similarity parameters for MCAO experiment

Transverse Magnification sqrt(Longitudinal Mag.)

Path, L

Aperture, D

Field angle at aper subaps across

Subap, d r00 r0

D/r0

Wavelength

Case 1

Atmos

1

1

1890

10

42.5

36

Lab

0.001

0.00408

0.0315

0.01

2550

36

Case 2

Atmos

1890

10

42.5

36

1

1

Lab

0.001

0.00408

0.0315 m

0.01 m

2550 arcsec

36

0.277777778

0.000277778

0.277777778

0.0002778 m

0.16

0.000718327

0.16

0.0002486 m

0.998686963

0.000998687

0.345640245

0.0003456 m

10.01314763

10.01314763

28.93181612

28.931816

2.30E-06 6.58E-07 9.50E-07 6.58E-07 m

3-layer model: mean altitude

Altitude, km Strength, % h^5/3

0 0.70

4.5

0.18

0

1226556.4

9

1.89 km

0.12

3894073.84

uncorrected rms r00, m theta00, arcsec c0

913.9221777

261.4612143

913.9221777

633.01136

0.16

0.000718327

0.16

0.0002486

3.264994502

0.01465834

3.264994502

0.0050732

3.17473E-13 2.59838E-09 3.17473E-13 1.523E-08


25, 2007 14

5 LGS Asterism Results

Error budget achieved in the lab

Error Budget (nm)

Fitting Error

Tomography Error

Wavefront Sensor Error

Aliasing Error

On-bench background

Case 1

Atmos Lab

Case 2

Atmos Lab

69.02377279

19.74680108

69.02377279

47.808045

104.8632219

30 96.7325228

67

62.37207263

17.84383643

41.8553553

28.990341

54.83533066

15.68767286

54.83533066

37.980682

6.990881459

2 2.887537994

2

Field stop misalign

SLM Lookup Table Error

27.41766533

7.84383643

27.41766533

18.990341

104.8632219

30 43.31306991

30

Static Uncorrectable S=0.85* 97.25055754

27.82211603

40.16870855

27.822116

Total rms 209.5526962

59.95029309

152.0850415

105.3389

Strehl 0.720571479

0.720571479

0.363571723

0.3635717

uncorrected rms r00, m theta00, arcsec c0

913.9221777

261.4612143

913.9221777

633.01136

0.16

0.000718327

0.16

0.0002486

3.264994502

0.01465834

3.264994502

0.0050732

3.17473E-13 2.59838E-09 3.17473E-13 1.523E-08

Simulations from TSW

TomographySphericalWave Simulations, r0=16cm, 5 LGS on 42.5 arcsec radius on-axis 15 arcsec 30 arcsec no noise, random seed 5 on-axis 15 arcsec 30 arcsec on-axis 15 arcsec 30 arcsec on-axis 15 arcsec 30 arcsec on-axis 15 arcsec 30 arcsec on-axis 15 arcsec 30 arcsec measurement noise, random seed 5 no noise, random seed 25 noise, random seed 25 no noise, random seed 13 noise, random seed 13

64

0

64

0

89

0

91 95.7548954

94.5727233

60 60 60

73

0

107

0

89

0

45 71.05632 65.73431

60 60 60

63

0

55

0

47 49.83974 60.20797 78.74643

0 60 60 60

64

1024

64 89 109

1024

113 112 73

1102

107 89 in simulator: no atmosphere and WFS nea = 0.05 arcsec generates 60 nm in tomography error

Noll says 0.05 nea => 52.071377 nm phase

75

1102

93


25, 2007

89 63

1053

55 47 78

1053

85 99

15

Plate 1 at 4km


25, 2007 16

4 to predict 1 in middle


25, 2007 17

5 LGS Asterism Results

• Field dependence – Mark Ammons


25, 2007 18

Lenslet-Pyramid Wavefront Sensor


25, 2007 19

Pyramid WFS Optical Layout


25, 2007 20


25, 2007 21

Lenslet-Pyramid WFS Response to

Sinusoidal Phase


25, 2007 22

LAO Activities Relevant To Keck NGAO Donald Gavel NGAO Team Meeting 6

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