FOBOS Calibration System
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Description: The FOBOS calibration system is housed in the focal plane
module. Its purpose is to supply calibration light to the science fibers
which in turn transmit the light to the bench spectrograph. The system path
within the focal plane module is highlighted in blue in the figure below.
To minimize expense, 2 off-the-shelf Edmund Industrial Optics achromatic doublets were used for this design. The layout can be viewed here. A spot diagram is available here. A ZEMAX file is also available.
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System/Prescription Data
Title: FOBOS Calibration System
Date : WED AUG 27 2003
LENS NOTES:
This design uses Edmund Industrial Optics lenses and provides 2X
magnification (maps 1" of opal glass to 2" at science ferrules).
GENERAL LENS DATA:
Surfaces : 14
Stop : 1
System Aperture : Float By Stop Size = 11.2
Glass Catalogs : SCHOTT
Ray Aiming : Off
Apodization : Uniform, factor = 0.00000E+000
Effective Focal Length : 106.4693 (in air at system temperature and pressure)
Effective Focal Length : 106.4693 (in image space)
Back Focal Length : 84.65516
Total Track : 215.9
Image Space F/# : 4.753094
Paraxial Working F/# : 13.04881
Working F/# : 13.08376
Image Space NA : 0.03828959
Object Space NA : 0.07641245
Stop Radius : 11.2
Paraxial Image Height : 19.8377
Paraxial Magnification : -2.00003
Entrance Pupil Diameter : 22.4
Entrance Pupil Position : 0
Exit Pupil Diameter : 25.6689
Exit Pupil Position : -333.3097
Field Type : Object height in Millimeters
Maximum Field : 9.9187
Primary Wave : 0.5875618
Lens Units : Millimeters
Angular Magnification : 0.8726513
Fields : 3
Field Type: Object height in Millimeters
# X-Value Y-Value Weight
1 0.000000 0.000000 1.000000
2 3.175000 4.965700 1.000000
3 0.000000 9.918700 1.000000
Wavelengths : 3
Units: Microns
# Value Weight
1 0.486133 1.000000
2 0.587562 1.000000
3 0.656273 1.000000
SURFACE DATA SUMMARY:
Surf Type Comment Radius Thickness Glass Diameter Conic
OBJ STANDARD Infinity 146.1444 19.8374 0
STO STANDARD Infinity 0 22.4 0
2 STANDARD (-)EDSCI 32494 197.7066 2.2 SF5 25 0
3 STANDARD 66.212 5.7 BK7 25 0
4 STANDARD -91.3659 25 25 0
5 STANDARD EDSCI 45215 184.84 3 BK7 25 0
6 STANDARD -134.06 2.5 SF5 25 0
7 STANDARD -393.98 48.3082 25 0
8 COORDBRK - 0 - -
9 STANDARD Infinity 0 MIRROR 42.06361 0
10 COORDBRK - -215.9 - -
11 COORDBRK - 0 - -
12 STANDARD Infinity 0 MIRROR 52.42035 0
13 COORDBRK - 31.75 - -
IMA STANDARD Infinity 39.87771 0
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The calibration lamp assembly consists of 3 arc lamps and one
quartz-tungsten-halogen (QTH) lamp that illuminate an opal diffusing glass.
The back side of the glass, which acts as a pseudo-integrator, is imaged
onto the focal plane ferrules. To simulate telescope-focused light,
the system uses optics that focus the calibration light at
approximately f/13.5. In order to achieve this focal ratio while limiting
the overall track length for the system, a 2X magnification is built in to
allow full illumination of the focal plane ferrule array.
