Demetrio MagrinINAF – Astronomical Observatory of Padovademetrio.magrin@oapd.inaf.it

Optical DesignCatania, 11/06/2014

Outlines Design parameters (Definition phase) Nominal Baseline (Definition phase) Nominal Performances (EE, spot diagram, PSFs,

vignetting factor) Sensitivity and thermal analysis Breadboard – Prototype New (Last…) Baseline Open Issues

Spectral range 500 – 1000 nmEntrance Pupil Diameter 120 mm

Working F/# 2.06 @ 700 nmField of View 1151.5 degree2

Image quality 90% Enclosed energy < 2×2 pixel2 over 1108.3 degree2

Maximum Field Distortion 5.043%Plate scale 15 arcsec/pixelPixel size 18 micron

CCD format 4510×4510 (×4) pixel2

FPA size 164.36 mm (2 mm CCDs gap)Optical elements weight 5 Kg (<6 Kg)Working Temperature -80°C

Working Pressure 0 atm

Design parameters

Nominal DesignDefinition phase (18/03/2011)

X

Y

Z

BK7 (G18)S-FPL51

N-KZFS11CaF2

S-FPL53 KZFSN5

BK7

368 mm

196.

2 m

m

R Thickness Glass K a4 a6 Shape Diameter(mm) (mm) (mm)

window S1 infinity 6.000 BK7G18 circular 190S2 infinity 2.000 190

Lens 1 S3 177.857 23.000 S-FPL51 -3.681 3.605E-8 -4.020E-12 circular 178S4 infinity 27.351 178

Lens 2 S5 795.855 7.000 N-KZFS11 circular 142

S6 135.943 56.975 130

Lens 3 S7 151.697 23.000 CAF2 circular 114S8 -225.536 59.886 116

Lens 4 S9 -742.200 17.000 S-FPL53 circular 130S10 -139.241 16.240 131

Lens 5 S11 -101.194 5.000 KZFSN5 circular 129.6S12 -144.005 115.547 135.4

Lens 6 S13 -103.083 5.000 N-BK7(G18) circular 154

S14 infinity 4.000 184FPA S15 infinity square

Nominal DesignDefinition phase (18/03/2011)

Aspheric surface S-FPL51

0

5

10

15

20

25

0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 80,0

mm

mm Surface Sag

BFS Sag

0

0,2

0,4

0,6

0,8

1

1,2

0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 80,0

mm

mm Deviation

Maximum deviation from BFS 1.050 mm

See R.Ragazzoni presentation

Enclosed Energy

2x2 pixels

G0V + detector QE

-40 micron +40 micron

Enclosed Energy (through focus)

Spot diagrams and FoV

13.6 deg, 13.6 deg

14.3 deg, 14.3 deg

4x4 pixels

About vignetting

Natural vignetting

7.5% at the edge of the ‘in spec’ FoV

9.0% at the edge of the full FoV

About vignetting

Mechanical vignetting

4.2% at the edge of the ‘in spec’ FoV

6.4% at the edge of the full FoV

About vignetting

Natural + Mechanical vignetting

11.7% at the edge of the ‘in spec’ FoV

15.4% at the edge of the full FoV

Polychromatic PSFs

PLATOSim

Element Decentering (+/- in micron)

Tilt (+/- in degrees)

L1 80 0.07L2 100 0.05L3 30 0.03L4 60 0.03L5 60 0.05L6 100 0.10

Sensitivity Analysis

Optical elements defocus 30-50 micron

Merit Function: 80%EE< 2×2 pixel2 over the corrected FoV

Thermal Analysis

• In the case of the of a uniform change of the temperature the optical system has 2 C of tolerances without the need of refocusing. With a temperature change of 10 C the nominal performances are still recoverable by applying a defocus through the three resistors.

• In the case of temperature gradient around the nominal temperature, the optical system maintain the nominal performance with a T=5 C without the need of refocusing. While the performances are recoverable by applying a defocus in the case of a T=10 C.

BreadBoard/Prototype Design

X

Y

Z

L1* L2* L3

L4 L5

L6

X

Y

Z

L1 L2 L3

L4 L5

L6 Window

The baseline design has been modified to allow the SESO tools adaptation (surfaces curvatures) and to facilitate and to speed up the manufacturing and mounting processes (some thicknesses and apertures have been increased). For procurement reasons, the glass of L5, KZFSN5, has been substituted by N-KZFS5.

(J.Farinato / V.Viotto / M.Bergomi presentations)

1) A physical stop in front of L3 (at about 2.84 mm edge to edge).

2) New weights for the wavelengths used in the Zemax merit function provided by P. Levacher - P. Bernardi.

3) Change the glass of L5 from KZFSN5 to N-KZFS5 (almost no optical impact and facilitate the procurement).

4) Change the thicknesses of L5 and L6 from 5mm to 7mm (all the industries suggested to increase these numbers).

5) Change on all lenses apertures from 1mm to 2mm with respect to the clear aperture. It should help to minimize the mechanical vignetting.

My last ‘New Baseline’… 21/05/2011

Data mining… (about 3 years to resurrect). Converge on a well-identified design to use

as baseline. Optimize the design for new/modified

requirements.Plate scale, PSF size, window material and thickness, 2 F-TOUs dedicated design.

Perform a detailed manufacturing/alignment tolerances and consolidate sensitivity/thermal analysis.RUAG warnings: the design is tight/ de-spacing tolerances are sub-micron.

Double-check performances in terms of EE/Simulator

Contact SESO and discuss the upgrade from breadboard to prototype with the related implications.

Open Issues