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ALIGNMENT PROCEDURE

Assumption: The camera optics mounts are machined such that the elements
are located within the specified tolerances. The warm alignment test
checks the centering and tip/tilt of the foreoptics. The warm alignment
test also checks the centering of the dewar optics, if accessible. The
cold alignment test checks the image quality.

# A. Warm Alignment.

# Tests the positioning of the elements. Can be done with or without the detector. If done without the detector, think about placing a ball bearing with its center at the center of the detector focal plane. Need all the other opto-mechanical mounts in-place.

1\. Define the optical axis as the beam passing through the center of
the instrument mounting flange and the folding flat mirror (FFM). Put
crosshair on the instrument mounting flange to mark the center, using
the 4 dowel pins spaced 90 degrees apart. Mark the center of the FFM
with crosshair?

Align a HeNe laser to the optical axis as defined above.

2\. Mark the center of the field mirror (FM) with a crosshair? Adjust
the tip/tilt of the FFM to center the laser beam on the FM.

3\. Mark the center of the window mount with a crosshair. Check that the
laser beam centers on the window. Adjust the FM tip/tilt if necessary to
center the beam at the window.

4\. QUESTION: are the dewar elements visible during alignment? If so,
without the window (which is opaque in the visible) or other
transmissive optical elements, check that the laser beam centers at the
mounting holes for the optical elements inside the dewar. Check the list
of tolerances for the dewar optics for the amount of decentering
allowed. If necessary, shim to adjust the (x, y) centering.

5\. Check that the beam is centered at the detector fold mirror (DFM)
and the detector. Adjust the tip/tilt of the DFM with shims if necessary
to center the beam at the detector. Look for the back-reflection from
the detector.

(If the elements aren't visible, look at the back-reflection with the
guide camera and a pellicle beamsplitter?)

6\. QUESTION: are the lens mounts designed so that the lenses are
off-centered at room temperature? If so, skip this step. If not, install
the lenses for Bands 2-4 and check that the beam is still centered at
the detector. Adjust the tip/tilt of the lenses if necessary to keep the
beam centered.

7\. Defocus the laser beam and look at scattered light patterns and
paths. Check that baffles are adequate. Are the point source and hot
plate bright enough to repeat this test with?

# 

# B. Cold Alignment

# Needs a functional detector. Tests the camera image quality.

1\. Install all the optics, filters, stops and the detector. (Note, the
Lyot stop defines the pupil in this test, so make sure it is in place.)
Cool-down the dewar.

2\. Check the optics alignment with the calibration point source. Optics
should be diffraction-limited. (How large is the point source?) If
alignment needs adjustment, iterate between warm-cold cycles. Adjust the
z-position of the lenses for defocus, and tip/tilt of the lenses for
bore-sight.