ztf optics design

ZTF Technical Meeting

1

ZTF Optics Design

<P. Jelinsky>

2013-02-01

2013-02-01


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Optics Outline

• Overview of Requirements• Trade Studies• Conceptual Design• Future Work

2013-02-01


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Requirements Overview• Use the Oschin Schmidt telescope primary and corrector• Illuminate 12 CCD231-C6 e2v detectors (6k x 6k, 15 µm pixels (~

1 arcsecond))– 16 detectors had large vignetting and worse imaging (see next slide)

• R band average FWHM < 1.1 arcseconds (final, including alignment and manufacturing)– Allow 1.0 arcseconds for the optical design

• G band average FWHM < 1.2 arcseconds (final, including alignment and manufacturing)– Allow 1.1 arcseconds for the optical design

• Use materials that transmit in the U and I band– May add these filters later

2013-02-01


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Requirements Overview (continued)2013-02-01

Detector Pattern(with vignetting)

No Vignetting

10%Vignetting

20%Vignetting

30%Vignetting


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Initial Trade Study Inputs

• Distance from flattener to CCD is >= 2mm• Allow distance from Schmidt corrector to mirror to vary• Window diameter/thickness <= 14.4 (same as QUEST camera)

– Safe to have atmospheric pressure accross

• Window is Fused Silica• All spherical surfaces

– Aspheric surfaces did not change performance much

• Optimize over 5 wavelengths in the g’, r’ bands as below (allowing a focus change).

• Optimize over 9 field points• Merit function is the 2D FWHM (RMS radius * 2.3548)

2013-02-01


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Bandpass Definition2013-02-01

u’ g’ r’ i’Wavelength

(nm)Wavelength

(nm)Wavelength

(nm)Wavelength

(nm)325.0 398.0 593.0 719.5340.0 432.5 625.5 770.75355.0 467.0 658.0 822.0370.0 501.5 690.5 873.25385.0 536.0 723.0 924.5


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Initial Trade Study

• Initially did not include a filter in the trade study and concentrated only on the R band– Filter seemed to always make design worse

• Quicker to analyze to limit trade space

2013-02-01


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Initial Trade Study2013-02-01

Design Description G Band FWHMR Band FWHM

Classical Schmidt(just for a limiting case)

0.78”0.65”

Curved Focal Plane Powered window

1.85”1.48”

Flat focal planePowered window

2.20”1.86”

4 segment focal plane4 segment window

1.53”1.21”

• No designs with flat detectors and vacuum windows met requirements


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12 Segment Focal Plane Schematic2013-02-01

Filter

Window

12 flatteners

12 detectors


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12 Segment Focal Plane Schematic

• Each detector is flat but tilted with respect to the others (see previous slide)– 12 chords on focal plane

• One vacuum window for all detectors (see previous slide)– After FEA center thickness fixed at ~22mm

• Each detector has its own field flattener (see previous slide)– Allow field flattener to be decentered and tilted

2013-02-01


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12 Segment Focal Plane Inputs

• Distance from flattener to detector > 2mm (smaller preferred)• Distance from flattener to window from 3 mm to 110 mm (larger preferred)• Distance from window to filter from 15 mm to 110 mm (larger preferred)• Filter, Window, and flatteners are Fused Silica

– Good transmission in UV and IR

• Only Optimized G and R band simultaneously (allowing focus change)• Optimize over 5 wavelengths in the g’, r’ bands• Optimize over 9 field points in each detector• Merit function is the average 2D FWHM (RMS radius * 2.3548)

– Use RMS field map with 50 x 50 points

2013-02-01


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12 Segment Focal Plane Trends• Thicker Windows degrade optical

performance– 22mm center window thickness

gives factor of safety of 8 (from FEA analysis)

• Thicker filter degrades optical performance

• Flat filter degrades optical performance

• Larger CCD – flattener spacing degrades optical performance

2013-02-01


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12 Segment Trade Study

• PTF Corrector Distance = 6075.3 mm; Original Corrector Distance = 6122.4 mm• (A) = asphere• (S) = sphere

2013-02-01

Case Filter Window Flattener R Band FWHM G Band FWHM CorrectorDistance

I Meniscus (5mm) Meniscus(A) Off axis 9.1µm (0.60”) 13.2µm (0.88”) 6263.6 mm

II Meniscus (5mm) Plano-Concave(S) Off axis 9.1µm (0.61”) 14.1µm (0.94”) 6214.6 mm

III Meniscus (5mm) Meniscus(A) On axis 9.0µm (0.60”) 14.1µm (0.94”) 6263.9 mm

IV Meniscus (5mm) Plano-Concave(S) On axis 9.1µm (0.61”) 14.0µm (0.93”) 6215.0 mm

V Meniscus (5mm) Meniscus(A) Identical 9.0µm (0.60”) 13.7µm (0.92”) 6252.5 mm

VI Meniscus (5mm) Plano-Concave(S) Identical 9.4µm (0.63”) 13.9µm (0.92”) 6212.6 mm

VII Plano-Convex (5mm) Concave-Plano(S) Off axis 9.4µm (0.63”) 14.8µm (0.98”) 6013.8 mm

VIII Plano-Convex (5mm) Concave-Plano(S) On axis 9.4µm (0.63”) 16.8µm (1.12”) 6013.9 mm

IX Plano-Convex (5mm) Concave-Plano(S) Identical 9.5µm (0.63”) 16.8µm (1.12”) 6014.5 mm

X Meniscus (10mm) Meniscus(A) Off axis 9.7µm (0.65”) 14.5µm (0.97”) 6319.2 mm

XI Meniscus (10mm) Meniscus(S) Off axis 9.8µm (0.65”) 15.5µm (1.04”) 6250.9 mm

XII Meniscus (10mm) Meniscus(S) On axis 9.8µm (0.65”) 15.5µm (1.03”) 6251.1 mm

XIII Meniscus (10mm) Meniscus(S) Identical 10.1µm (0.67”) 15.5µm (1.04”) 6250.3 mm

XIV Plano-Convex (10mm) Biconcave(S) Identical 9.7µm (0.65”) 16.8µm (1.12”) 6108.7 mm

XV Plano-Convex (5mm) Biconcave(S) Identical 9.1µm (0.60”) 14.9µm (1.00”) 6107.1 mm

XVI Plano-Plano(10mm) Meniscus(A) Identical 20.5µm (1.37”) 27.7µm (1.85”) 6155.5 mm

XVII Plano-Plano(10mm) Meniscus(A) Off axis 20.5µm (1.37”) 28.0µm (1.86”) 6160.9 mm

XVIII Plano-Plano(5mm) Meniscus(A) Off axis 18.0µm (1.20”) 24.6µm (1.64”) 6154.6 mm


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Case XV Imaging Results (1 Quadrant)

• R Band average FWHM = 0.60 arcseconds; maximum FWHM = 0.88 arcseconds• G Band average FWHM = 1.00 arcseconds; maximum FWHM = 1.26 arcseconds

2013-02-01

0

0.2

0.4

0.6

0.8

1

1.2R Band G Band

FWH

M (a

rcse

cond

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Future Work

• Finish I and U band results• Complete optical tolerance analysis

– Budget/split tolerances into telescope and cryostat sections• E.g. filter location (part is telescope filter mechanism/ part is

cryostat manufacture)

• Complete vignetting/obscuration analysis• Complete ghosting/scattered light analysis• Complete manufacturability/cost studies

2013-02-01


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BACKUP SLIDES

2013-02-01


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Detector

Field Flattener

Detector Gap

• If t is the thickness of the flattener, d is the distance from detector to the flattener, c is the chamfer of the flattener, g is the gap between the flatteners, f is the f/# of the beam, n is the index of refraction of the glass, and s is the spacing between the detectors, then

• For g = 2mm, c = 1mm, t = 5mm, d=2mm, f=2.5, n = 1.5 then s = 8.2 mm– I assumed 8.4 mm in the analysis

2013-02-01

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Detector Layout• Two Detectors layouts have been considered

– Minimize the gap in each direction (asymmetrical, need 3 detectors in Zemax)– Place detectors centers on a square grid (symmetrical, need 2 detectors in Zemax)

2013-02-01

• Only the minimize gap has been studied at the moment• The square grid

version will be a slight modification to the optics

Detector X (mm) Y (mm) xfield (°) yfield (°)1 4.2 4.2 0.079 0.0791 50.4 4.2 0.945 0.0791 96.6 4.2 1.810 0.0791 4.2 50.28 0.079 0.9421 50.4 50.28 0.945 0.9421 96.6 50.28 1.810 0.9421 4.2 96.36 0.079 1.8061 50.4 96.36 0.945 1.8061 96.6 96.36 1.810 1.8062 105 4.2 1.967 0.0792 151.2 4.2 2.832 0.0792 197.4 4.2 3.695 0.0792 105 50.28 1.967 0.9422 151.2 50.28 2.832 0.9422 197.4 50.28 3.695 0.9422 105 96.36 1.967 1.8062 151.2 96.36 2.832 1.8062 197.4 96.36 3.695 1.8063 4.2 104.76 0.079 1.9633 50.4 104.76 0.945 1.9633 96.6 104.76 1.810 1.9633 4.2 150.84 0.079 2.8253 50.4 150.84 0.945 2.8253 96.6 150.84 1.810 2.8253 4.2 196.92 0.079 3.6863 50.4 196.92 0.945 3.6863 96.6 196.92 1.810 3.686

Field locations for minimum gap

Detector X (mm) Y (mm) xfield (°) yfield (°)1 4.32 4.32 0.081 0.0811 50.4 4.32 0.945 0.0811 96.48 4.32 1.808 0.0811 4.32 50.4 0.081 0.9451 50.4 50.4 0.945 0.9451 96.48 50.4 1.808 0.9451 4.32 96.48 0.081 1.8081 50.4 96.48 0.945 1.8081 96.48 96.48 1.808 1.8082 105.12 4.32 1.970 0.0812 151.2 4.32 2.832 0.0812 197.28 4.32 3.693 0.0812 105.12 50.4 1.970 0.9452 151.2 50.4 2.832 0.9452 197.28 50.4 3.693 0.9452 105.12 96.48 1.970 1.8082 151.2 96.48 2.832 1.8082 197.28 96.48 3.693 1.808

Field locations for square grid


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Minimize the gap (Zemax settings)

• RMS field map settings– Ray density = 6– Data = Spot Radius– Wavelength = All– Method = Gauss Quad– Center field = 5– Refer To = Centroid– X field size = 0.8655– Y field size = 0.8655– X field sampling = 50– Y field sampling = 50– Surface = Image

• Use the text->Window->Copy clipboard to place the data into excel for analysis

2013-02-01


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Case XV Optical Prescription (Detector 1)2013-02-01

88

66

44

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2

)1(11rArArArA

rck

crz

# Type Surface ROC = (1/c)(mm)

Thickness(mm) Glass Diameter

(mm) A2 A4 A6 A8

1 STANDARD CORRECTOR 117054.9 11.481 LLF6 1244.75 2 EVENASPH CORRECTOR 64570.285 17.221 BK7 1245.40 0 -5.68E-12 0 03 EVENASPH CORRECTOR 173900.95 2850.000 1246.32 0 2.25E-12 8.01E-20 04 STANDARD Infinity 3257.102 1501.99 5 STANDARD M1 -6123.94 -2750.000 MIRROR 1803.40 6 STANDARD R band Focus Infinity -39.996 427.63 7 STANDARD G band Focus Infinity -40.077 0.00 8 STANDARD filter -2949.311 -19.472 SILICA 403.85 9 STANDARD Infinity -110.000 398.98 10 EVENASPH window 4808.0832 -22.278 SILICA 337.21 0 0 0 011 EVENASPH -2123.604 -110.000 325.74 0 0 0 012 STANDARD Det 1 focus Infinity -0.569 277.72 Decenter X Decenter Y Tilt X Tilt Y

13 COORDBRK Flat1 tilt Infinity 0.000 0.00 50.6747 50.5515 -1.2043 1.220314 STANDARD Det1 flat -731.0547 -5.062 SILICA 132.45 15 STANDARD Infinity -2.000 131.67 Decenter X Decenter Y Tilt X Tilt Y

16 COORDBRK Det1 Tilt Infinity 0.000 0.00 0 0 -0.0508 0.037627 STANDARD FILM Infinity 0.000 130.60


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88

66

44

2222

2

)1(11rArArArA

rck

crz



(mm) A2 A4 A6 A8

1 STANDARD CORRECTOR 117054.9 11.481 LLF6 1244.75 2 EVENASPH CORRECTOR 64570.285 17.221 BK7 1245.40 0 -5.68E-12 0 03 EVENASPH CORRECTOR 173900.95 2850.000 1246.32 0 2.25E-12 8.01E-20 04 STANDARD Infinity 3257.102 1501.99 5 STANDARD M1 -6123.94 -2750.000 MIRROR 1803.40 6 STANDARD R band Focus Infinity -39.996 427.63 7 STANDARD G band Focus Infinity -40.077 0.00 8 STANDARD filter -2949.311 -19.472 SILICA 403.85 9 STANDARD Infinity -110.000 398.98 10 EVENASPH window 4808.0832 -22.278 SILICA 337.21 0 0 0 011 EVENASPH -2123.604 -110.000 325.74 0 0 0 017 STANDARD Det2 focus Infinity -5.000 447.66 Decenter X Decenter Y Tilt X Tilt Y


21 COORDBRK Det2 tilt Infinity 0.000 0.00 0 0 -0.9843 2.765027 STANDARD FILM Infinity 0.000 130.60


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88

66

44

2222

2

)1(11rArArArA

rck

crz



(mm) A2 A4 A6 A8

1 STANDARD CORRECTOR 117054.9 11.481 LLF6 1244.75 2 EVENASPH CORRECTOR 64570.285 17.221 BK7 1245.40 0 -5.68E-12 0 03 EVENASPH CORRECTOR 173900.95 2850.000 1246.32 0 2.25E-12 8.01E-20 04 STANDARD Infinity 3257.102 1501.99 5 STANDARD M1 -6123.94 -2750.000 MIRROR 1803.40 6 STANDARD R band Focus Infinity -39.996 427.63 7 STANDARD G band Focus Infinity -40.077 0.00 8 STANDARD filter -2949.311 -19.472 SILICA 403.85 9 STANDARD Infinity -110.000 398.98 10 EVENASPH window 4808.0832 -22.278 SILICA 337.21 0 0 0 011 EVENASPH -2123.604 -110.000 325.74 0 0 0 022 STANDARD Det3 focus Infinity -4.977 446.97 Decenter X Decenter Y Tilt X Tilt Y


26 COORDBRK Det3 tilt Infinity 0.000 0.00 0 0 -2.8059 1.040827 STANDARD FILM Infinity 0.000 130.60

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