1 ATST Imager and Slit Viewer Optics Ming Liang

2 Optical layout of the telescope, relay optics, beam reducer and imager. Optical Layouts

3 Gregorian Position Gregorian Instrument Bench

4 Spot diagrams on the Gregorian focus Spot Diagrams

5 Design propertyRequirement Field of view3’ x 3’ for f/20 imager 1.5’ x 1.5’ for f/40 imager Wavelength band0.33 to 1.1 μm Image qualityWithin the diffracted limitation Focal surfaceFlat focal surface and telecentric output Visible Imager Design Requirements

6 FOV: 3’ x 3’. Wavelength band:0.33 to 1.1 μ. Flat focal surface and telecentric output. The total bulk absorption is about 7% at 330 nm wavelength band N-BaK2 CaF2 N-BaK2 N-BaK2 CaF2 Silica F/20 Visible Imager

7 Spot diagrams for f/20 imager, within 3’x3’ fields. The circles in the spot diagrams are Airy disk size at 630 nm wavelength. Up left: Normal position. Up: 45º altitude. Left: 45º azimuth.

8 FOV: 3’X3’, wavelength band: 0.33 to 1.1 μm, slit mirror tilt 22.5° Slit mirror Slit viewer optics F/20 imager F/20 Visible Imager and Slit Viewer Optics

9 Spot diagrams for f/20 slit viewer, within 3’x3’ fields. The circles in the spot diagrams are Airy disk size at 630 nm wavelength Up left: Normal position. Up: 45º altitude. Left: 45º azimuth.

10 N-BaK2 CaF2 N-BaK2 CaF2 N-BaK2 Silica FOV: 1.5’ x 1.5’. Wavelength band:0.33 to 1.1 μ. Flat focal surface and telecentral output Con-focus with that of f/20 imager F/40 Visible Imager

11 Spot diagrams on f/40 Imager focus within 1.5’x1.5’ fields. The circles in the spot diagrams are Airy disk size at 630 nm wavelength Up left: Normal position. Up: 45º altitude. Left: 45º azimuth.

12 FOV: 1.5’x1.5’, wavelength band: 0.33 to 1.1 μm, flat focus. The same guiding system works for both f/20 and f/40 imager. F/40 imager Slit viewer optics F/40 Visible Imager, Slit Mirror and Slit Viewer Optics

13 Spot diagrams for f/40 guider, within 1.5’x1.5’ fields. The circles in the spot diagrams are Airy disk size at 630 nm wavelength Up left: Normal position. Up: 45º altitude. Left: 45º azimuth.

14 Design propertyRequirement Field of view3’ x 3’ for f/20 imager 1.5’ x 1.5’ for f/40 imager Wavelength band1 to 5 μm Image qualityWithin the diffracted limitation Focal surfaceFlat focal surface and telecentric output IR Imager Design Requirements

15 FOV: 3’ x 3’. Wavelength band:1 to 5 μ., Flat focal surface and telecentric output. Lens materials (follow the light pass): ZnSe, BaF2, CaF2 and CaF2. F/20 IR Lens Imager

16 Spot diagrams of f/20 lens imager for wavelength from 1 to 5 μm. The circles in the spot diagrams are Airy disk size at 1.6 μm wavelength. Spot Diagrams

17 FOV: 1.5’ x 1.5’. Wavelength band:1 to 5 μ., Flat focal surface and telecentral output.To make it con-focus with f/20 imager, there are two more lenses than the f/20 IR lens imager. Lens materials (follow the light pass): ZnSe, BaF2, CaF2, ZnSe, BaF2 and CaF2. F/40 IR lens imager

18 Spot diagrams of f/40 IR lens imager. The circles in the spot diagrams are Airy disk size at 1.6 μm wavelength. Spot Diagrams

19 Reflected Imager Options (For visible and IR)

20 Design propertyRequirement Field of view3’ x 3’ for f/20 imager 1.5’ x 1.5’ for f/40 imager Wavelength band0.33 to 28 μm Image qualityWithin the diffracted limitation Focal surfaceFlat focal surface and telecentric output Optical Design Requirements

21 2 mirror F/20 imager with flat focal surface and telecentric output. F/20 Reflected Imager

22 Spot diagrams for f/20 Imager, within 3’x3’ fields. The circles in the spot diagrams are Airy disk size at 630 nm wavelength Up left: Normal position. Up: 45º altitude. Left: 45º azimuth.

23 Folding mirror F/40 Reflected Imager Optical layout of f/40 visible imager with flat focus and telecentral output FOV: 1.5’x1.5’, wavelength band: 0.33 to 1.1 μm.

24 Spot diagrams on f/40 Imager focus within 1.5’ x 1.5’ field. The circles in the spot diagrams are Airy disk size at 630 nm wavelength Up left: Normal position. Up: 45º altitude. Left: 45º azimuth.

25 F/40 Imager F/40 Imager folding mirrors F/20 Imager The drawing shows how to exchange the f/20 imager to f/40 imager. When the f/40 imager is inserted, the f/20 beam will be bypassed by the f/40 folding mirror to the detector. Imager Exchange

26 IR channel Visible channel Dichroic Lens imagers in visible channel and mirror imagers in IR channel System Arrangement

27 Optical Train From Telescope to Detector ATST 250 K Visible Spectrograph Example (Current Spectrograph to be presented by David Elmore or HAO and Don Mickey for IR version) Telescope – Collimator Relay – Beam Reducer – f/20 Imager – CT spectrograph

28 F/20 imager Spectrograph F/20 Imager and Spectrograph

29 The optical layout shows the whole system from telescope to spectrograph. Whole Optical Layout

30 Imager Optics Appendices

31 Spot diagrams for f/20 lens imager, within 3’x3’ fields. The spot diagrams show the image rotate status for different telescope position. Up left: Normal position. Up: 45º altitude. Left: 45º azimuth.

32 FOV: 1.5’ x 1.5’. Wavelength band:1 to 5 μ., Flat focal surface and telecentric output. The folding mirrors help to con-focus with f/20 imager. The advantage: increase throughput and reduce scattering. Disadvantage: more polarizing. F/40 IR lens imager, con-focus by folding mirrors

33 Spot diagrams of f/40 IR lens imager with folding mirrors. The circles in the spot diagrams are Airy disk size at 1.6 μm wavelength. Spot Diagrams

34 F/20 camera F/40 camera Dichroic Folding mirrors An alternative arrangement of change between f/20 to f/40 mirror imager Alternative Imager Exchange

35 Dichroic Another Visible and IR Imagers Combination

36 Detail of Example Spectrograph

37 SpecificationRequirement Result Resolution>240,000 Goal ~ 300, pm at 600 nm 286,000 for 0.5” slit Wavelength range300nm – 1100nm Yes Spatial Resolution0.05 arc sec Goal: diffraction limited at 600 nm Close to diffraction limitation Spatial field of view3 arc minYes 250K Resolution Spectrograph Design Requirement

38 Spectrograph modelCzerny Turner type Resolution286 K for 0.05 arc sec slit width SlitWidth 0.05 arc sec, height 3” (70 mm) CollimatorFocal length 1800 mm, focal ratio f/20 Grating Echelle grating, blazing angle 57º, l/mm. 41 order for nm CameraFocal length 2400 mm, f/27 DetectorPixel size 13 μm, 0.025”/pixel Visible Spectrograph Design Characteristics

39 The collimator focal length is 1800mm and the camera focal length 2400 mm. Echelle grating: l/mm, blazing angle of 57º. Slit (f/20) Collimator mirror Echelle grating Image mirror Detector (f/27) Detail of the 250 K Visible Spectrograph

40 Spectrum spot diagrams centered at nm. The scales in the low right box indicate that the spot diagrams scale is 50 μm, the dispersion scale (space scale in x) is 4 mm and the field scale (space scale in y) is 15 mm. The numbers on the top line are the spectrum wavelengths and the numbers in the left column are the corresponding field on the slit. The ray tracings are from the telescope to the detector. The data under the spot diagrams are their position on the detector.

41 Spectrum spot diagrams centered at nm

42 Spectrum spot diagrams centered at nm

43 Spot diagrams of the spectrograph at wavelength of nm. The field along slit is 3 arc min. The circles in the spot diagrams show the size of Airy disk. Up left: Normal position. Up: rotate 45º in altitude. Left: rotate 45º in azimuth.

44 Multiple Instrument Example

45 Multiple Instrument Example

46 Multiple Instrument Example