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ATST Imager and Slit Viewer Optics

Ming Liang

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

Optical Layouts

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Gregorian Position

Gregorian Instrument Bench

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Spot diagrams on the Gregorian focus

Spot Diagrams

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Design property Requirement

Field of view 3’ x 3’ for f/20 imager

1.5’ x 1.5’ for f/40 imager

Wavelength band 0.33 to 1.1 μm

Image quality Within the diffracted limitation

Focal surface Flat focal surface and telecentric output

Visible Imager Design Requirements

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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

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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.

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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

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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.

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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

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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.

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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

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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.

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Design property Requirement

Field of view 3’ x 3’ for f/20 imager

1.5’ x 1.5’ for f/40 imager

Wavelength band 1 to 5 μm

Image quality Within the diffracted limitation

Focal surface Flat focal surface and telecentric output

IR Imager Design Requirements

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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

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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

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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

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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

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Reflected Imager Options(For visible and IR)

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Design property Requirement

Field of view 3’ x 3’ for f/20 imager

1.5’ x 1.5’ for f/40 imager

Wavelength band 0.33 to 28 μm

Image quality Within the diffracted limitation

Focal surface Flat focal surface and telecentric output

Optical Design Requirements

212 mirror F/20 imager with flat focal surface and telecentric output.

F/20 Reflected Imager

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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.

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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.

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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.

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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

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IR channel

Visible channel

Dichroic

Lens imagers in visible channel and mirror imagers in IR channel

System Arrangement

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Optical Train From Telescope to DetectorATST 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

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F/20 imager

Spectrograph

F/20 Imager and Spectrograph

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

Whole Optical Layout

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Multiple Instrument Example

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Multiple Instrument Example

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Multiple Instrument Example