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NIC-FPS Critical Design Review

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NIC-FPS Critical Design ReviewOpto-Mechanical ComponentsMark B. Vincent(CU-CASA)26 July 2002CASA-ARLBoulder, CO26 July 20022NIC-FPS Critical Design ReviewOpto-Mechanical Components Include:• Window – CaF2140 mm diameter, 14 mm thick, no wedge, no AR on exterior surface• Lens mounts – Collimator w/ 3 lenses, Camera w/ 5 lenses• Etalon Actuator – Linear translator• Lyot Stop – Stationary once aligned• Filter Wheels – Three 7 slot wheels• FPA Mount – Supplied by Rockwell26 July 20023NIC-FPS Critical Design ReviewLens Mounts• Collimator and camera in separate Al tubes• Collimator-camera alignment tolerances ~1 mm offset, ~ 1’ tilt• Warm up and cool down rates determined by contact area with bench• Individual lenses are held in collet fingers mounts based on the Ohio State University Imaging Sciences Laboratory’s (ISL) design• Collet fingers have decenter and tilt tolerances of < 50 µm which is sufficient for the NIC-FPS optics• Prototype lens mount provided by University of North Carolina• Lens spacing set by spacers between the collet fingers26 July 20024NIC-FPS Critical Design ReviewEtalon Actuator• Will use a cryogenic linear translator of ~ 90 mm travel• Wiring is flexible at 77 K – will flex our cable extension• Limited to 20 mm maximum depth• Three options:1. Commercially manufactured – available, but insufficient travel2. O’Brien (ISL) has a design that has worked without failure for a numberof years in OSIRIS3. Design one in-house• Etalon is mounted perpendicular to beam• Etalon itself is mounted by six m4 bolts, three on each face These bolts are the sole thermal contacts26 July 20025NIC-FPS Critical Design ReviewLyot Stop• Cold Lyot stop used to minimize radiation from beyond the primary mirror reaching the FPA• Pupil is 40 mm diameter with 4.6 mm central obstruction• Recommend undersizing the primary and oversizing the central obstruction by 175 µm. This is 0.9% by diameter and 1.8% by area• Lyot stop is a mask deposited onto a 50 mm diameter, 3 mm thick fused silica or CaF2substrate• Zemax runs suggests that once the stop is aligned to the optical axis, no further alignment is necessary to compensate for telescope-instrument misalignments• Alignment made by changing shims26 July 20026NIC-FPS Critical Design ReviewFilter Wheels• Three 7 slot filter wheels for 17 filters, 1 blank, 3 opens (one in each wheel)• Arranged in a pair and single on opposite sides of the bench• Direct drive cryo stepper motor in contact with gear around the circumference of the wheel, gear ratio ~ 23:1• Three microswitches provide direct position readout, one microswitchon detent• Wheel, detent, direct position readout and bearings based on ISLhighly successful design26 July 20027NIC-FPS Critical Design ReviewIntegration & Testing• Request for quotes on optics placed next week• Order optics in September• 4-5 month lead time on optics – arrive by February 2003• Design optomechanical & fab components August 2002 – February 2003• Final lens spacings will not be determined until the as-built optics specs are in. We will work closely with the vendor to minimize the impact of fabrication tolerances on image quality and element spacings.• Final pupil position is not known until the as-aligned optics are in house• Ron Probst and Jay Elias of NOAO will provide a tour of their facility and discuss optical alignment• May visit Tom O’Brien at OSU to see the upgrade of


NIC-FPS Critical Design Review

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