Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.arcetri.astro.it/~ferruzzi/VST_220798_optic2.PDF Äàòà èçìåíåíèÿ: Mon May 6 16:38:35 2002 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 03:47:29 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 63

Document: VST_220798_optic2.doc Release: 1 First rel.date: 21.07.98 Last rel. date: 22.07.98 Page 1 of 10

AN OPTICAL SOLUTION FOR THE VST WITH REMOVABLE ADC AND ONE FIXED LENS CORRECTOR

Authors: D. Ferruzzi, G. Marra Supervised by: D. Mancini Checked by: D. Mancini

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Introduction

In this document, another possible optical solution for the VST, is reported. Respect to the one presented in the VST_180798_optic1.doc document, there is one fixed lens, when changing from the configuration in which ADC is inserted to that in which it is removed. All Kick-off meeting requirements are satisfied, although the optical quality is lower than for the design in which all corrector elements are removed when changing configuration. The first surface of the first lens, and the first and last surface of ADC were normalized to DIN table 58166. The other radius of curvature values were rounded, because a normalization produces a decrease of the optical quality.

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One fixed lens and removable ADC

In this solution, respect to the previous one, one lens is fixed when inserting or removing ADC. So, only one lens has to be inserted or removed. For this design one lens less would be manufactured. The optical quality is below that of the previous solution, but still satisfies requirements. Respect to the previous design, the dewar window has an higher curvature. The distance between the mirrors is still fixed when changing the corrector for use in the different bands. All lenses and ADC surfaces are spherical as requested. In Figures 2-1 and in 2-2, the complete optical layout of the telescope with one lens and the ADC and the zoom of the corrector are shown. In Figures 2-3, 2-4 the complete optical layout of the telescope with the two lenses and the zoom of the corrector are reported. In Tables 2-1 and 2-2 the diffraction encircled energy values for the two configurations in which ADC is inserted ( B, V, R, I band) and removed (U Â I), are reported for all fields of view, at zenith angle z=0° and at the zenith angle corresponding to the maximum dispersion of ADC. In Figure 2-5 the fraction of polichromatic diffraction encircled energy values curves are shown.

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Figure 2-1 VST complete optical layout of telescope with one fixed lens, the ADC and a curve dewar window

Figure 2-2 VST zoom of the optical layout of the corrector with one fixed lens, the ADC and a curve dewar window

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Figure 2-3 VST optical layout of telescope with two lenses (U Â I bands)

Figure 2-4 VST zoom of the optical layout of the two lenses (U Â I bands)

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FRACTION (%) OF DIFFRACTION ENCIRCLED ENERGY
1 FIXED LENS +ADC CORRECTOR Field radius (deg) Zenith (z=0°) 2.07 pxl (32 µm) 0 0.3535 0.5 0.707 0.735 96 92 85 82 80 z = 63° 2.66 pxl (40 µm) 97 91 84 82 80 z=0° z=63° z=0° z=63° z=0° z=63° z=0° z=63° B ÂI bands (0.365 Â 1.014 µm) B band (420 Â 520 nm) V band (560 Â 650 nm) R band (650 Â 740 nm) I band (775 Â 900 nm)

1.4 pxl 1.06 pxl 1.46 pxl 1.4 pxl 1.6 pxl 1.53 pxl 1.73 pxl 1.73 pxl (20µm) (16µm) (22µm) (20 µm) (24 µm) (23 µm) (26µm) (26µm) 97 88 80 93 91 93 87 80 86 81 99 90 80 81 84 98 93 81 84 87 99.9 93 83 80 82 98 95 85 80.5 83.4 98 95 86 80 82 97 96 88 81 84

Table 2-1 Percentage diffraction encircled energy values, from B to I bands and for each band, for the configuration of one fixed lens and ADC FRACTION (%) OF DIFFRACTION ENCIRCLED ENERGY TWO LENSES CORRECTOR Field radius (deg) U ÂI bands (0.320 Â 1.014 µm) 2 pxl (30 µm) 0 0.3535 0.5 0.707 0.735 83.7 96.5 85.8 81 81.4

Table 2-2 Diffraction encircled energy values for the configuration with two lenses corrector from U to I bands

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VST optical data and performance

In Table 3-1 VST main optical data are reported. In Tables 3-2 and 3-3 the optical data for the two configurations, with the ADC inserted and with the ADC removed are respectively shown. In Tables 3-4, 3-5 the optical performance for the two configurations are reported. Respect to the solution of VST_180798_optic1.doc document, the maximum distortion is reduced from 0.19% to 0.15%, when ADC is inserted, and from 0.18% to 0.12% when ADC is removed. The maximum field curvature values are comparable. VST MAIN OPTICAL CHARACTERISTICS Main optical data for the full system Optical configuration Pupil diameter Angular field of view F# Equivalent focal lenght Modified Ritchey Chretien 2600 mm (1.47°) 5.5 14500mm (two lenses) 14379.4 mm (one fixed lens +ADC) Image scale 0.21 arcsec/pixel Overall lenght 4445.78 mm (fixed) Distance between M1 and M2 3405.78 mm (fixed) Spectral Range U Â I bands 400 mm (min. req) Distance M1 vertex to first corrector lens in B Â I bands 400 mm (min. req) Distance M1 vertex to first corrector lens in UÂ I bands Distance M1 vertex to CCD plane 1040 mm (< max.req) Footprint diameter of light beams in M1 centre hole 490 mm (< max. req) Distance between last corrector element and the image plane 206.37 mm for one lens +ADC (> min. req) 249.75 mm for two lenses (> min. req) Image plane corrector in B, V, R, I bands One fixed lens +ADC Atmospheric Dispersion Corrector (ADC) Two double prisms made of UBK7 and LLF6 Two lenses Image plane corrector in UÂ I bands Focal Plane CCd mosaic 16 k x 16 k Ccd pixel size 15µm x 15µm Primary Mirror parameters Outer Diameter 2600 mm Inner Diameter 720 Ray of curvature -9829 mm Conic constant K1 -1.145442 f/number 1.89 Secondary Mirror parameters Diameter 894 mm Ray of curvature -4571.06 mm Conic constant K2 -5.782526 Table 3-1 VST main optical data

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OPTICAL DATA FOR ONE LENS AND ADC CORRECTOR, FILTER AND DEWAR Element Prism angle R1 R2 Material Diameter Thickness L1 ADC S1 (First prism) ADC S2 (First prism) ADC S3 (Second prism) ADC S4 (Second prism) Filter (B band) Filter (V band) Filter (R band) Filter (I band) Dewar window 0° 0° 3° 0° 3° 1258.9 mm -1294.81 Infinity Infinity 10000 2238.7 mm Silica UBK7 LLF6 UBK7 LLF6 440.4 mm 432.6mm 378.05 mm 377.9 mm 375.3 mm 375.6 mm 50 mm 19 mm 15 mm 15 mm 20 mm

Air thickness 311.63 mm 0 mm 3 mm 0 mm 76.37 mm

Infinity Infinity Infinity Infinity 930.57 mm

Infinity Infinity Infinity Infinity 829.63 mm

Silica Silica Silica Silica Silica

370.7 mm 370.6 mm 370.7 mm 370.5 mm 373.8 mm 373.2 mm 370.8 mm 370.6 mm 370 mm 367 mm

15 mm 15 mm 15 mm 15 mm 20 mm

50 mm 50 mm 50 mm 50 mm 45 mm

Table 3-2 VST optical data for one fixed lens, ADC, filter and dewar window in, B, V, R, I bands

Element L1 L2 Filter Dewar window

OPTICAL DATA FOR TWO LENSES CONFIGURATION R1 R2 Material Diameter Thickness 1258.9 mm 2238.7 mm Silica 440.4 mm 50 mm 432.6 mm -1295.7 5997.4 mm Silica 383.4 mm 58.72 mm 380.6 mm Infinity Infinity Silica 377.7 mm 15 mm 377.5 mm 930.57 mm 829.63 mm Silica 375.8 mm 20 mm 372.6 mm

Air thickness 281.53 mm 119.75 mm 50 mm 45 mm

Table 3-3 VST optical data for two lenses corrector, filter and dewar window in U Â I bands

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VST OPTICAL PERFORMANCE (WORST CASE) FOR THE CONFIGURATION WITH 1 FIXED LENS +ADC B BAND Diffraction encircled energy Tangential maximum field of curvature Sagittal maximum field of curvature Maximum distortion Glass transmission V BAND Diffraction encircled energy Tangential maximum field of curvature Sagittal maximum field of curvature Maximum distortion Glass transmission R BAND Diffraction encircled energy Tangential maximum field of curvature Sagittal maximum field of curvature Maximum distortion Glass transmission I BAND Diffraction encircled energy Tangential maximum field of curvature Sagittal maximum field of curvature Maximum distortion Glass transmission Z=0°: 80% in 1.73 pixel Z=63°: 81% in 1.73 pixel z=63°: 0.32 mm at =1.014 µm on axis z=63°: 0.33 mm at =1.014 µm on axis z=63°: 0.14% (< 0.3% goal) at =0.775 µm at the edge of the field 99 % at =0.810 µm Z=0°: 80% in 1.6 pixel Z=63°: 80% in 1.5 pixel z=63°: 0.27 mm at =0.74 µm on axis z=63°: 0.25 mm at =0.74 µm on axis z=63°: 0.15% (< 0.3% goal) at =0.65 µm at the edge of the field 99% at =0.660 µm Z=0°: 80% in 1.46 pixel Z=63°: 81% in 1.4 pixel z=63°: 0.23 mm at =0.65 µm on axis z=63°: 0.25 mm at =0.65 µm on axis z=63°: 0.14% (< 0.3% goal) at =0.56 µm at the edge of the field 99% at =0.580 µm Z=0°: 80% in 1.4 pixel Z=63°: 85% in 1.06 pixel z=63°: 0.22 mm at =0.52 µm z=63°: 0.20 mm at =0.52 µm z=63°: 0.15% (< 0.3% goal), at =0.42 µm at the edge of the field 95% at =0.365 µm

Table 3-4 Optical performance for the configuration with ADC inserted

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OPTICAL OPERFORMANCE FOR THE CONFIGURATION WITH TWO LENSES (WORST CASE) U Â I bands (0.320 Â 1.014 µm) 80% in 2 pixel 0.41 mm at = 1.014 µm on axis 0.41 mm at = 1.014 µm on axis 0.12 % at the edge of the field at = 0.32µm 99 %

Diffraction encircled energy Maximum tangential field of curvature Maximum sagittal field of curvature Maximum distortion Glass transmission

Table 3-5 Optical performance for the configuration with two lenses

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Field curvature and distortion curves

In Figures 4-1, 4-2 the field curvature and distortion curves for the configurations with one fixed lens and ADC and with two lenses are reported

Figure 4-1 Field curvature and distortion curves for the configuration with one lens and ADC

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Figure 4-2 Field curvature and distortion curves for the configuration with two lenses

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Spot diagrams

In figures 5-1, 5-2 the spot diagrams for one fixed lens and ADC configuration at zenith and at 63° are reported from B to I bands, and in Figure 5-3 the spot diagrams for two lenses configuration are shown.

Figure 5-1 Spot diagram for one fixed lens and ADC at zenith from B to I
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Figure 5-2 Spot diagrams for one fixed lens and ADC at z=63°

Figure 5-3 Spot diagram for two lenses from U to I bands
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