March 12, 2022
While successful, implementation of collimated beam projector to date has two issues: 1) dynamic range mismatch between monitor diode (wants nA of current) and astronomical instrument (100,000 electrons per pixel max), and 2) not directly monitoring beam at exit pupil, due to size mismatch.
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At 808 nm:
| angle (degrees) | Rp | Rs |
|---|---|---|
| 0 | 0.041365 | 0.041365 |
| 5 | 0.040948 | 0.041784 |
| 10 | 0.039693 | 0.043069 |
| 15 | 0.037593 | 0.045301 |
| 20 | 0.034640 | 0.048630 |
If angle of incidence is 10 degrees, reflected beam rotates by 20 degrees. If beam of diameter D rotates by theta, distance it must travel to not have incident and reflected overlap obeys tan(theta)=D/L so L/D=1/tan(theta)
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This wedge pair needs to be tilted relative to incident beam. Five degree wedge angle seems good, as a pair. That gives us variation from zero to around 30 arcmin. For any sensible focal plane array of 4K x 4K
Jan 31 2024 CWS
light source conceptual design
If we use a laser-driven Xenon light source, from Energetiq (we have one in lab, in a box) we get this output spectrum: (https://www.energetiq.com/eq99xfc-fiber-coupled-broadband-light-source)
If we operate with spectral bandwidth of around 1 nm, with a 200 micron diameter fiber we get around 10 uW/nm of spectral density. That would generate around 5 uA of photocurrent in photodiode, that's a lot! Even with factor of one hundred loss in transmission to photodiode we should be fine.
Possible double monochromator: https://www.spectralproducts.com/CM112/2232
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| Description | Qty | Part # | Details | Purchase Date |
|---|---|---|---|---|
| Pitch and Yaw Tilt Platform with Thumbscrew Drives | 8 | APY001 | 01/30/24 | |
| Ø2" UVFS Wedged Window, Uncoated | 8 | WW42012 | 01/30/24 | |
| 60 mm Cage Cube | 8 | LC6WR | 01/30/24 | |
| Light-Tight Blank Cover Plate for 60 mm Cage Cube, 1/4"-20 Tap | 10 | LB1C | 01/30/24 | |
| SM2-Threaded Cover Plate for 60 mm Cage Cube | 4 | LB2C | 01/30/24 | |
| Kinematic Prism Platform for 60 mm Cage Cube, Imperial Taps | 6 | LB4C | 01/30/24 | |
| 60-mm-Cage-Compatible Rectangular Filter Mount | 2 | LFFM1 | 01/30/24 | |
| Ø2" Optic Mount for 60 mm Cage Cube with Setscrew Optic Retention | 8 | LB5C1 | 01/30/24 | |
| 60 mm Kinematic Cage Cube Connector | 8 | DFM2-CC | 01/30/24 | |
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