Receiver Tube

Created April 24, 2004

Last updated April 24, 2004

The reciever tube is to be a well baffled/filtered light-tight box that houses the receiver optics and detector. A narrow-band filter at the front prohibits all but 532 nm light from entering. A spatial filter focuses the remaining light into a small hole (about 3-arcseconds) so that only green moonlight right around our target is allowed into the rest of the system. Further baffles all the way to the detector eliminate rogue photons.

The optical train goes like:

1. Narrow-band filter: probably about 1 nm bandpass or a little tighter, set at an angle so-as to allow the rejected light to be picked up by the CCD camera.
2. PLZT or other variable attenuator for further reduction of internal corner-cube photons.
3. Spatial filter lens, 25 mm diameter, about 100 mm focal length
4. Spatial filter hole: about 0.25 mm in diameter for 100 mm focal-length lens
5. Spatial filter lens, identical to the previous one: re-collimates beam
6. Focusing lens, roughly 400 mm focal length, 25 mm diameter
7. Lenslet array and APD

The optical mounts ahould allow three degrees of translational freedom for initial alignment. Once aligned it is not anticipated that we will have to adjust their positions. A square cross-section may be easiest to deal with, especially since this allows the top cover to be removed and baffles/lens-mounts slid into and out of place in slotted acceptors. The inside will be painted black, and baffle planes will be placed every inch or two.

The arrangement will be supported at a couple of places onto the optical table. This should be a repeatable (kinematic) mount so that the receiver can be removed for access to other components on the laser bench, and replaced in exactly the same position. The APD box will be a mechanically separate piece, probably butting up to some gasket seal at the back of the baffle box.

I will finalize the optical design soon and place the specifics here.

APOLLO To Do Task List.