ZTF Field Flattener 12 segment designs 22 mm thick window P. Jelinsky 2012/11/27

Revision History 2 RevisionCommentAuthorDate 1Initial Analysis (only minimum gap orientation)pnj2012/11/27

Assumptions 3 Distance from flattener to CCD is >= 2mm Distance from filter to window between 15 and 110 mm Distance from window to flatteners between 3 and 110 mm Allow distance from corrector to mirror to vary Center Window thickness = 22mm Window, filter and flatteners are Fused Silica 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 * ) Use RMS field map with 50 x 50 points u’g’r’i’ Wavelength (nm) Wavelength (nm) Wavelength (nm) Wavelength (nm)

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

Schematic 5 Filter Window 12 flatteners 12 detectors

Detector Layout 6 Two Detectors layouts have been studied Minimize the gap in each direction (slightly asymmetrical, need 3 detectors in Zemax) Place detectors centers on a square grid (symmetrical, need 2 detectors in Zemax) DetectorX (mm)Y (mm)xfield (°)yfield (°) Field locations for minimum gap DetectorX (mm)Y (mm)xfield (°)yfield (°) Field locations for square grid

Minimize the gap 7 RMS field map settings Ray density = 6 Data = Spot Radius Wavelength = All Method = Gauss Quad Center field = 5 Refer To = Centroid X field size = Y field size = X field sampling = 50 Y field sampling = 50 Surface = Image Use the text->Window->Copy clipboard to place the data into excel for analysis

Minimize the Gap (cont) 8 CaseFilterWindowFlattenerR Band FWHMG Band FWHM Corrector Distance IMeniscus (5mm)Meniscus(A)Off axis9.1µm (0.60”)13.2µm (0.88”) mm IIMeniscus (5mm)Plano-Concave(S)Off axis9.1µm (0.61”)14.1µm (0.94”) mm IIIMeniscus (5mm)Meniscus(A)On axis9.0µm (0.60”)14.1µm (0.94”) mm IVMeniscus (5mm)Plano-Concave(S)On axis9.1µm (0.61”)14.0µm (0.93”) mm VMeniscus (5mm)Meniscus(A)Identical9.0µm (0.60”)13.7µm (0.92”) mm VIMeniscus (5mm)Plano-Concave(S)Identical9.4µm (0.63”)13.9µm (0.92”) mm VIIPlano-Convex (5mm)Concave-Plano(S)Off axis9.4µm (0.63”)14.8µm (0.98”) mm VIIIPlano-Convex (5mm)Concave-Plano(S)On axis9.4µm (0.63”)16.8µm (1.12”) mm IXPlano-Convex (5mm)Concave-Plano(S)Identical9.5µm (0.63”)16.8µm (1.12”) mm XMeniscus (10mm)Meniscus(A)Off axis9.7µm (0.65”)14.5µm (0.97”) mm XIMeniscus (10mm)Meniscus(S)Off axis9.8µm (0.65”)15.5µm (1.04”) mm XIIMeniscus (10mm)Meniscus(S)On axis9.8µm (0.65”)15.5µm (1.03”) mm XIIIMeniscus (10mm)Meniscus(S)Identical10.1µm (0.67”)15.5µm (1.04”) mm XIVPlano-Convex (10mm)Biconcave(S)Identical9.7µm (0.65”)16.8µm (1.12”) mm XVPlano-Convex (5mm)Biconcave(S)Identical9.1µm (0.60”)14.9µm (1.00”) mm PTF Corrector Distance = mm; Original Corrector Distance = mm (A) = asphere (S) = sphere