ZTF Field Flattener12 segment designs

P. Jelinsky2012/10/02

Revision History

2

Revision Comment Author Date1 Initial Analysis pnj 2012/09/04

2 Completed Case II – III added Case IV through VI pnj 2012/09/18

3 Added window thickness and ccd distance study pnj 2012/10/02

Assumptions

3

• Distance from flattener to CCD is >= 3mm• Distance from filter to window between 15 and 110 mm• Distance from window to flattnerers between 3 and 110 mm• Allow distance from corrector to mirror to vary• d/t <= 14.4 (same as QUEST camera)• 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 in each detector• Merit function is the 2D FWHM (RMS radius * 2.3548)

u’ g’ r’ i’Wavelength

(nm)Wavelength

(nm)Wavelength

(nm)Wavelength

(nm)325.0 398.0 593.0 719.5

340.0 432.5 625.5 770.75

355.0 467.0 658.0 822.0

370.0 501.5 690.5 873.25

385.0 536.0 723.0 924.5

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 = 1.8 then s = 6 mm— I assumed 8.4 mm in the following analysis

4

Detector

Field Flattener

1)14(

2222

fn

tfdcgs

Schematic

5

Filter

Window

12 flatteners

12 detectors

Case I Identical Axisymmetric Flatteners

6

Case R Band FWHM G Band FWHMCurved 5mm filter 14.3µm (0.95”) 24.2µm (1.61”)Curved 10 mm filter 15.4µm (1.03”) 26.1µm (1.74”)Flat 5 mm filter 27.0µm (1.80”) 35.8µm (2.39”)Flat 10 mm filter 29.5µm (1.96”) 39.1µm (2.61”)

R Band G Band

Case II Non Identical Axisymmetric Flatteners

7

Case R Band FWHM G Band FWHMCurved 5mm filter 11.5µm (0.77”) 22.7µm (1.51”)Curved 10 mm filter 12.8µm (0.85”) 23.4µm (1.56”)Flat 5 mm filter 26.7µm (1.78”) 35.7µm (2.38”)Flat 10 mm filter 29.2µm (1.95”) 39.1µm (2.60”)

R Band G Band

Case III Non Identical Non Axisymmetric Flatteners

8

Case R Band FWHM G Band FWHMCurved 5mm filter 11.5µm (0.75”) 21.3µm (1.42”)Curved 10 mm filter 13.3µm (0.88”) 23.4µm (1.56”)Flat 5 mm filter 24.0µm (1.60”) 32.4µm (2.07”)Flat 10 mm filter 26.5µm (1.76”) 35.8µm (2.38”)

R Band G Band

Case IV Non Identical Non Axisymmetric Flatteners (Window Asphere front)

9

Case R Band FWHM G Band FWHMCurved 5mm filter 10.4µm (0.70”) 19.6µm (1.30”)Curved 10 mm filter 10.7µm (0.72”) 22.4µm (1.49”)Flat 5 mm filter 24.2µm (1.61”) 32.6µm (2.17”)Flat 10 mm filter 26.6µm (1.77”) 35.9µm (2.40”)

R Band G Band

Case V Non Identical Non Axisymmetric Flatteners(Window Asphere rear)

10

Case R Band FWHM G Band FWHMCurved 5mm filter 10.7µm (0.72”) 19.2µm (1.28”)Curved 10 mm filter 11.1µm (0.74”) 21.7µm (1.45”)Flat 5 mm filter 24.1µm (1.60”) 32.8µm (2.19”)Flat 10 mm filter 26.9µm (1.79”) 36.4µm (2.42”)

R Band G Band

Case VI Non Identical Non Axisymmetric Flatteners(Window Asphere front Silica flattener)

11

Case R Band FWHM G Band FWHMCurved 5mm filter 12.5µm (0.83”) 18.0µm (1.20”)Curved 10 mm filter 13.2µm (0.88”) 20.5µm (1.37”)Flat 5 mm filter 20.7µm (1.38”) 30.2µm (2.01”)Flat 10 mm filter 23.0µm (1.53”) 33.4µm (2.23”)

R Band G Band

Non Identical Non Axisymmetric Flatteners(Changing Window thickness)

12

Center Window Thickness R Band FWHM G Band FWHM17.6 mm 8.5µm (0.57”) 12.0µm (0.80”)23.6 mm 9.1µm (0.61”) 13.9µm (0.93”)28.3 mm 9.4µm (0.62”) 15.9µm (1.06”)35.7 mm 11.4µm (0.76”) 17.7µm (1.18”)

R Band G Band

Curved 5mm filter

Non Identical Non Axisymmetric Flatteners(Changing CCD to flattener distance)

13

CCD to flattener distance R Band FWHM G Band FWHM0.0 mm 8.4µm (0.56”) 13.7µm (0.91”)1.0 mm 8.3µm (0.56”) 15.0µm (1.00”)2.0 mm 9.4µm (0.62”) 15.9µm (1.06”)3.0 mm 10.7µm (0.71”) 16.4µm (1.09”)4.0 mm 12.3µm (0.82”) 17.4µm (1.16”)

R Band G Band

Curved 5mm filter (28.3 mm thick window)