mcao adaptive optics module subsystem optical designs r.a.buchroeder
TRANSCRIPT
MCAOMCAO
Adaptive Optics ModuleAdaptive Optics Module Subsystem Optical Designs Subsystem Optical Designs
R.A.Buchroeder
May 24-25, 2001 MCAO Preliminary Design Review
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MCAO Optical BenchMCAO Optical Bench
• In-plane optical layout, with room for electronics
• f/16 input, f/33.4 AOM output
• Image plane and exit pupil location match those of telescope
• DMs, TTM, BS, ADC in collimated space
• Gemini telescope plate scale 0.62 mm/arc sec
• MCAO output plate scale ~ 1.30 mm/ arc sec
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOScience path
LGS path
NGS path
Beam splitters
LGS focus
Science focus
NGS focus
Optical PathsOptical Paths
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Parameter Science Path NGS WFS Path LGS WFS Path
Spectral passband, m
0.85-2.5
0.5-0.85 0.589
Field-of-view radius, arc min
1 1 1 (width of square FOV)90—200 km range
Wave front quality
60 nm RMS uncorrectable and non-common path errors (59 nm at zenith; 96 at 45 degrees)
0.15 arc sec RMS spot size (120 nm RMS WFE)
Peak subaperture tilts less than 0.1 arc sec (102 nm RMS WFE)
Optical transmittance
0.75 (0.74 at 1.0 micron; 0.80 at 1.65; 0.82 at 2.2)
0.7 (0.46 at 0.5 micron; 0.69 at 0.7)
0.7 (0.65)
Pupil imaging
Worst case pupil motion of 3% on instrument cold stop (2% RMS)
NA Worst case WFS-to-DM misregistration 10% of a subaperture width (6.8% RMS)
Emissivity 19% NA NA
Atmospheric dispersion at 45 degrees, arc sec
0.007 for 0.85+/-0.07 m (0.002)0.010 for 1.25+/-0.1 m (0.0039)0.013 for 1.65+/-0.1 m (0.0019)0.018 for 2.20+/-0.2 m (0.0023)
0.05
NA
AO Module Optical AO Module Optical Design Design RequirementsRequirements
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AO Module Science AO Module Science PathPath
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H-band RMS wavefront errorH-band RMS wavefront error
• Wavelength 1.65 um
• ADC operating @ 45-deg zenith angle
• Upper part of +/- one arc-min FOV; field is not rotationally symmetric.
• Representative RMS
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MCAOMCAOScience Path: I-band w/o Science Path: I-band w/o ADCADC
Circle = 0.053 arc sec
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MCAOMCAOScience Path: I-band at Z = 45 Science Path: I-band at Z = 45 degdeg
Circle = 0.053 arc sec
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOScience Path: J band @ Z=45 Science Path: J band @ Z=45 degdeg
Circle = 0.08 arc sec
May 24-25, 2001 MCAO Preliminary Design Review
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Science Path: H-band Spot Science Path: H-band Spot DiagramsDiagrams
• H-band, 1.55 to 1.75 microns
• 2 arc-min FOV
• With ADC operating @45deg Zenith Angle
• Circle = Airy disc diameter = 0.103 arc sec
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOScience Path: K-band at Z=65 Science Path: K-band at Z=65 degdeg
Circle = 0.14 arc sec
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MCAOMCAOH-band Mapping error H-band Mapping error @ @ 45 degree Zenith Angle 45 degree Zenith Angle
Maximum distortion: 1.9%
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Science Path ADC Science Path ADC @ Maximum Correction@ Maximum Correction
• I-band (0.78- 0.92 um) to 65-deg zenith angle
• Angular deviation = 0 at 0.85 um; could be tip-adjusted for zero at H-band.
• Different, smaller symmetrical counter-rotations for J,H,K bands
May 24-25, 2001 MCAO Preliminary Design Review
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NGS Path Optical NGS Path Optical LayoutLayout
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NGS Path Image Quality NGS Path Image Quality
• @45-deg zenith angle
• Better at zenith
• < 1 mm image runout wrt ADC rotation
• Circle = Airy Disc
• Secondary color OK due to abnormal dispersion glass types
Circle ~ 0.04 arc sec
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
NGS Image NGS Image MappingMapping
• Varies slightly with zenith angle
• Shown here at 45-degree zenith angle
• 1.3% distortion typical
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NGS WFS Design ConceptNGS WFS Design Concept
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MCAOMCAOLGS Path: General LGS Path: General RequirementsRequirements
• Monochromatic @ 589nm
• FOV = square one arc-minute on a side
• Laser star range 90 to 200 km
• Telecentric intermediate image plane
• Pupil misregistration less than 10% of subaperture
• Small noncommon path wave front errors
• Transmittance goal = 70% (65% current performance)
• Performance requires zoom focus adjustment, adjustable relay elements, and pupil alignment mirrors.
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LGS Optical Path LayoutLGS Optical Path Layout
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LGS “Zoom Optics”LGS “Zoom Optics”
• LGS range 90 to 200 km
•V-coatings @ 589nm for high transmission
•Elements A and D fixed
• Elements B and C form a ‘mechanically compensated’ zoom
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LGS Image Quality vs RangeLGS Image Quality vs Range
• Spot diagrams at inter-mediate focus
• Residuals compensated by spot relay and LASER AIMING
• Superimposed at 4 ranges
• Marker = 200 microns
• Circle = Airy disc
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MCAOMCAOLGS: from Zoom Optics LGS: from Zoom Optics to to S-H Lenslet Array S-H Lenslet Array
May 24-25, 2001 MCAO Preliminary Design Review
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LGS: Wavefront at S-H ArrayLGS: Wavefront at S-H Array
• Representative case
• Central laser star
• 127 km range
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MCAOMCAOLGS: Mapping of DM0 to SH LGS: Mapping of DM0 to SH PlanePlane
• Best case; others similar
• Central laser star
• 127 km range
• Distortions scaled up by 100X on this plot
• By symmetry, 3 different collimators required.
Maximum Distortion 0.12 %
Pupil Map with distortion Magnified 100X
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MCAOMCAOLGS WFS: SH Focus to CCD LGS WFS: SH Focus to CCD RelayRelay
Adjustable relay reduces non-common path errors from 100 to below 10 nm RMS
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LGS WFS Relay: variable LGS WFS Relay: variable magnification mode magnification mode
• Geometrical spot diagrams
• Results superimposed over magnification range
• Circles = Airy disc
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LGS WFS: Relay Distortion LGS WFS: Relay Distortion
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Diagnostic WFS Design ConceptDiagnostic WFS Design Concept
• Insert into converging f/33.4 beam, pivot around exit pupil
• 32x32 sub apertures on 10.4mm pupil ( 325 um lenslet size )
•1k x 1k CCD, 10 um pixel
• Nyquist sampling @ 0.9 um
• Sub aperture FOV = ~11.3 arc-sec in object space
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MCAOMCAONGS WFS Transmittance NGS WFS Transmittance EstimateEstimate
Wavelength 500 nm 700 nm
Transmission per reflection 0.944 0.979
10 reflections 0.562 0.809
Science beamsplitter, net 0.990 0.995
NGS/LGS Rugate BS 0.950 0.950
NGS/LGS dielectric BS 0.850 0.850
Air-glass per surface 0.993 0.996
ADC net (4 surfaces) 0.970 0.984
Corrector Lens 0.986 0.992
APD Optical Path, Type A 0.79 0.82
APD Optical Path, Type B 0.91 0.93
Total transmission:
With Rugate BS and Type A 0.40 0.61
With Rugate BS and Type B 0.46 0.69
With dielectric BS and Type A 0.36 0.55
With dielectric BS and Type B 0.41 0.62
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOLGS WFS Transmittance LGS WFS Transmittance EstimateEstimate
Wavelength 589nm
Transmission per silvered reflection 0.962
9 silvered reflections 0.706
Science Beamsplitter net 0.980
NGS/LGS Rugate beamsplitter 0.990
NGS/LGS dichroic beamsplitter 0.850
Air-glass per surface optimized 589nm 0.998
4 element Zoom Lens Corrector 0.984
Collimator,dielectric mirror 0.998
Pupil Steering, dielectric mirror 0.998
De-anamorphoser lens 0.996
Shack-Hartmann Lens 0.996
6-group (8 element) SH-CCD relay lens 0.976
Total Transmission
With Rugate BS 0.65
With dichroic BS 0.56
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Optical Component FabricationOptical Component Fabrication
• Off-Axis Paraboloids, 3 required
• Science Path Beamsplitter, water-free fused silica
• Science Path ADCs, water-free fused silica and fluorite
• NGS/LGS beamsplitter made from ordinary fused silica, with small wedge angle and a cylindrical curvature on R2.
• NGS ADCs made from optical glass
• LGS four spherical optical glass lenses
• NGS sphero-parabolic optical glass lens
• Off-axis aspheric collimator mirrors, 5 required
• Afocal cylindrical deanamorphoser lenses, 5 required
• Miscellaneous
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MCAOMCAO
AOM Optical Design SummaryAOM Optical Design Summary
• All optical issues have viable solutions
• Relatively simple optical designs
• Thanks to OAPs, assembly and deflection tolerances are liberal
• Certain components are difficult and expensive to fabricate but prospective vendors indicate that they are feasible
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
PDR AgendaPDR Agenda
Thursday, 5/240800 Welcome 0805 Project overview 0830 Science case0930 Break0945 System overview1015 System modeling1100 AO Module optics1145 Lunch
1245 AO Module mechanics1340 AO Module electronics1400 Break1415 Beam Transfer Optics1510 Laser Launch
Telescope1545 Closed committee
session1800 Adjourn