[Laser] Trihedral prism source?

[Jim Moss]

James,
The arrangement of the 3 mirrors involves 2 hinges
Consider 3 mirrors arranged in an L configuration, see this crude text-gram.
Each mirror was mounted on a wood frame.

[ ][ ]

[ ]

Put hinges on the adjacent sides.
If folded upward, they will form a corner cube.
The corner that the 2 lifted sides intersect is where the adjustments are made.

Mount a piece of 90 deg angle aluminum and an aluminum flat strip that will be parallel to each other in each axis/plane. Mount them so that they are about 1 inch apart when the surfaces of the mirror are at about 90 degrees.
I L   
A 1.25 inch screw will go between these 2 parallel plates. A single 4-40 screw & 3 nuts are used to adjust & hold the plates.

Arrangement:
Screw head - plate - nut1 - adjustment space - nut2 - L plate - nut3
 
Nut1 holds the screw head to plate firmly.  Nut2 and nut3 are used to push/pull the L plate and hold it in position.
Assuming 1 foot mirrors (1 foot from hinge to adjustment screw), one revolution of the nut will adjust the surface angles about 0.12 degrees. (from memory) 
arctan (1/40 divided by 12) = angle

Do the same thing for the other axis/plane.
The fit will be tight, but there will still be some fine control.

Does this explain it well enough to get the idea?
Jim


----- Original Message ----
From: James Whitfield <n5gui at cox.net>
To: Free Space LASER Communications <laser at mailman.qth.net>
Sent: Tuesday, March 10, 2009 9:49:52 AM
Subject: Re: [Laser] Trihedral prism source?

Jim

I tried to contact you offline.  I do not know if the message got to you.

I was wondering if it would be possible to get pictures of the 12X12 mirror 
retro-reflector that you built.  Of particular interest is the method you 
used to adjust the relative angles.

My attempts were rather crude and un-successful.  That probably was due to 
my lack of imagination to "see" the solution.  I would like to see how you 
approached the problem.

Thank you.

James
n5gui



----- Original Message ----- 
From: "Jim Moss" <n9jim-6 at pacbell.net>
To: "Free Space LASER Communications" <laser at mailman.qth.net>
Sent: Sunday, March 01, 2009 12:36 PM
Subject: Re: [Laser] Trihedral prism source?


James,
Agree with your inputs. I use the same items.
I recommend the stick on reflective tape. Pretty easy to use and attach.

I've built the 12x12 setup, and it works well, especially when the beam has 
expanded to greater than the size of the reflectors, then you get "1" beam 
back.
For adjusting, I used a screw/nut arrangement to hold the angles. This 
allows easy tweeking of the sides.

Jim
N9JIM




______________________________________________________________
Laser mailing list
Home: http://mailman.qth.net/mailman/listinfo/laser
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Laser at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html