As-built optical models for the LDT

Please contact Tom Bida to request the Zemax models.

A.  Two optical models are available for folded instrument cube ports, including the instrument cube mechanical and optical geometry.  A standard fold mirror is an elliptical pyrex flat, with a clear mounted aperture of (115mm X 166mm).  Existing fold mirrors have both protected aluminum and gold coatings.  The dichroic fold mirror is an elliptical fused silica element 12.7mm thick, with both sides polished for reflection and transmission, and a 0.15 deg wedge for transmitted astigmatism compensation.  Existing coated dichroic elements efficiently transmit from 300-700nm (UBVr'), and reflect from 900-2500nm (YJHK).  The dichroic element has a reflected clear mounted aperture of (128mm X 184mm).  The dichroic blank can be replicated as a fold mirror without the wedge or polished back surface, to fit into the existing dichroic cell assembly.  

  1. The unvignetted FOV of a standard fold mirror is 2.4 arcmin circular diameter, or 1.7 arcmin square.  Maximum field curvature is approximately 15 microns.
  2. The unvignetted FOV of the dichroic fold mirror is 4 arcmin circular diameter, or 3 arcmin square.  Maximum field curvature is approximately 45 microns.
  3. The back focus from the instrument mounting flanges for folded cube ports is 180mm.
  4. The RC plate scale is 8 arcsec/mm.

B.  For the RC corrector, with LMI including the dual filter wheel, and surface points for the cube structure and components. 

The 2-element corrector has the following characteristics:

  1. The 2 lenses are fabricated of fused silica, with transmission of 98.5% from 300-1100nm.
  2. The corrected, unvignetted FOV is 0.5 deg diameter, with 0.03% differential distortion over this FOV.
  3. The AR coatings provide average reflectance of 0.84% from 300-1100nm, with < 0.025% additive ghost-reflection sky background.
  4. The modeled spot size is 4.2-6.4 microns RMS (< 0.082 arcsec FWHM) over the LMI FOV (0.205 deg square), for B through I-bands.

The LMI CCD is a deep-depletion e2v CCD-231-C6, 6K x 6K 15 micron pixels, coated with a 4-layer Astro AR coating.  The plate scale is 0.12 arcsec/pixel.