[Laser] Trihedral prism source?

[Jim Moss]

I just used inexpensive decorative wall mirrors.
Jim




----- Original Message ----
From: Zack Widup <w9sz.zack at gmail.com>
To: Free Space LASER Communications <laser at mailman.qth.net>
Sent: Tuesday, March 10, 2009 8:26:19 PM
Subject: Re: [Laser] Trihedral prism source?

I'm going to have to build me one of those!

Question - are your mirrors glass? If so, is the reflective surface on the
front or behind the glass?

73, Zack W9SZ


On 3/10/09, Jim Moss <n9jim-6 at pacbell.net> wrote:
>
>
> 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
>
>
>
>
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