Lens wheel optics for CD18

Layout of lens wheel for CD018

Angle     Optical Component                          Voltage
-120 deg  mirror                                     4.9V
-60 deg   1% neutral density filter                  5.9V
0 deg     25mm KRS5 lens                             6.9V
60 deg    Open                                       7.9,1.9V
120 deg   ZnSe lens                                  8.9,2.9V
180 deg   38mm KRS5 lens + 1% neutral density filter 3.9V

i_KRS5=39.9 mm, installed at 40.6 mm from detector
i_ZnSe=28.8 mm, installed at 29.0 mm from detector
i_KRS5_25mm=52.6, installed at ~50mm from detector

38mm KRS5 lens + 38mm ND filter:
In CD017, we were unable to image the pupil with the previous arrangement of the 38mm KRS lens and 25mm 10% ND filter. This was probably due to multiple reflections between the lens and filter.
In CD017, the arrangement had been detector-ND-lens.
For CD018, the 38mm 1% ND filter has been placed outside the lens:  detector-lens-ND.


We have a shortage of 38mm retaining rings for the barrels and thus couldn't hold any blocker windows in the remaining free slot. I chose to put in another pupil lens, purposely installed closer to the detector than would be ideal for imaging the echelle grating. Maybe it will do a better job on imaging the TAAS hot plates?

I will ask Emmett to make more retaining rings for us in time for CD19.