ATST Imager and Slit Viewer Optics

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ATST Imager and Slit Viewer Optics

• Ming Liang

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Optical Layouts
Optical layout of the telescope, relay optics,
beam reducer and imager.
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Gregorian Position
Gregorian Instrument Bench
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Spot Diagrams
Spot diagrams on the Gregorian focus
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Visible Imager Design Requirements
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
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F/20 Visible Imager
FOV 3 x 3. Wavelength band0.33 to 1.1
µ. Flat focal surface and telecentric output.
The total bulk absorption is about 7 at 330 nm
wavelength band
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Spot diagrams for f/20 imager, within 3x3
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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F/20 Visible Imager and Slit Viewer Optics
FOV 3X3, wavelength band 0.33 to 1.1 µm,
slit mirror tilt 22.5
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Spot diagrams for f/20 slit viewer, within 3x3
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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F/40 Visible Imager
FOV 1.5 x 1.5. Wavelength band0.33 to 1.1
µ. Flat focal surface and telecentral
output Con-focus with that of f/20 imager
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Spot diagrams on f/40 Imager focus within
1.5x1.5 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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F/40 Visible Imager, Slit Mirror and Slit Viewer
Optics
FOV 1.5x1.5, wavelength band 0.33 to 1.1 µm,
flat focus. The same guiding system works for
both f/20 and f/40 imager.
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Spot diagrams for f/40 guider, within 1.5x1.5
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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IR Imager Design Requirements
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
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F/20 IR Lens Imager
FOV 3 x 3. Wavelength band1 to 5 µ., Flat
focal surface and telecentric output. Lens
materials (follow the light pass) ZnSe, BaF2,
CaF2 and CaF2.
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Spot Diagrams
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.
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F/40 IR lens imager
FOV 1.5 x 1.5. Wavelength band1 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.
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Spot Diagrams
Spot diagrams of f/40 IR lens imager. The circles
in the spot diagrams are Airy disk size at 1.6 µm
wavelength.
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Reflected Imager Options(For visible and IR)
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Optical Design Requirements
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
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F/20 Reflected Imager
2 mirror F/20 imager with flat focal surface and
telecentric output.
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Spot diagrams for f/20 Imager, within 3x3
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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F/40 Reflected Imager
Optical layout of f/40 visible imager with flat
focus and telecentral output FOV 1.5x1.5,
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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Imager Exchange
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.
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System Arrangement
Lens imagers in visible channel and mirror
imagers in IR channel
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Optical Train From Telescope to DetectorATST 250
K Visible SpectrographExample(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 and Spectrograph
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Whole Optical Layout
The optical layout shows the whole system from
telescope to spectrograph.
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Imager Optics Appendices
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Spot diagrams for f/20 lens imager, within 3x3
fields. The spot diagrams show the image rotate
status for different telescope position. Up left
Normal position. Up 45º altitude. Left 45º
azimuth.
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F/40 IR lens imager, con-focus by folding mirrors
FOV 1.5 x 1.5. Wavelength band1 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.
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Spot Diagrams
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.
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Alternative Imager Exchange
An alternative arrangement of change between f/20
to f/40 mirror imager
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Another Visible and IR Imagers Combination
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Detail of Example Spectrograph
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250K Resolution Spectrograph Design Requirement
Specification Requirement Result
Resolution gt240,000 Goal 300,000 2.5 pm at 600 nm 286,000 for 0.5 slit
Wavelength range 300nm 1100nm Yes
Spatial Resolution 0.05 arc sec Goal diffraction limited at 600 nm Close to diffraction limitation
Spatial field of view 3 arc min Yes
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Visible Spectrograph Design Characteristics
Spectrograph model Czerny Turner type
Resolution 286 K for 0.05 arc sec slit width
Slit Width 0.05 arc sec, height 3 (70 mm)
Collimator Focal length 1800 mm, focal ratio f/20
Grating Echelle grating, blazing angle 57º, 64.67 l/mm. 41 order for 630.2 nm
Camera Focal length 2400 mm, f/27
Detector Pixel size 13 µm, 0.025/pixel
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Detail of the 250 K Visible Spectrograph
The collimator focal length is 1800mm and the
camera focal length 2400 mm. Echelle grating
64.67 l/mm, blazing angle of 57º.
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Spectrum spot diagrams centered at 630.2 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.
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Spectrum spot diagrams centered at 331.3 nm
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Spectrum spot diagrams centered at 1076.6 nm
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Spot diagrams of the spectrograph at wavelength
of 630.2 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.
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Multiple Instrument Example
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Multiple Instrument Example
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Multiple Instrument Example