3-D Table Layous

Colin Kaminski · Post by **Colin Kaminski** » Sat May 29, 2004 12:11 pm

I am going to move to an overhead reference. I have been trying to decide how high to build the gantry and I have realized I am a little uncertain about the geometries I will encounter. I would like to design the system around a 13" f 4.5 mirror.

Does anyone have any advice?

d a battin · Post by **d a battin** » Sat May 29, 2004 12:37 pm

i use 1 inch pipe schaffolding W/connectors for the frame mounted on top of 3x4 foot solid core top, the refrence mirror beam is folded. It becomes a whole diferent way of thinking about your set ups.I have to get some good photos to show you ,ill try this holiday weekend.

Bruce · Post by **Bruce** » Sat May 29, 2004 1:17 pm

Funny you should mention that as my current setup is an overhead collimated split beam reflection, one of the most difficult setups that I remember doing.
Keep in mind that the ref. beam will be angled up so spatial filters and wave plate (if necessary) may have to be set higher than usual, longer focal length mirrors will alleviate some of this headache.
The real limiting factor in my case was setting the mirror/film plane at Braggs angle which places the film quite close to the mirror and crowds object lighting to some extent.
So keep in mind, the angle of the ref. beam will impose (in my case) camber adjustable optics mount (B.S.) and spatial filter will be both relatively higher than normal as well as angled up. The mirror must have a decent range of tilt adjustment as determined by its focal length and Braggs angle at the film plate. My mirror is a "salad bowl" (very fast) so I am using a small portion of my table.
Geometry being everything, I found only one combination that will work for me and that required a fairly severe angle from the laser to mirror. My mirror is quite large and heavy so I used aluminum pipe and aluminum fittings used for handrail and handicapped railings type construction. This gave me stability and ease/range of adjustment. Mirror can be seen here: ?BCgnMuABxPbhAfxc

Bruce

Bruce · Post by **Bruce** » Sat May 29, 2004 1:24 pm

http://f2.pg.briefcase.yahoo.com/bconst ... global.net

Go to laser files and click on table yag.

danny bruza · Post by **danny bruza** » Sat May 29, 2004 1:50 pm

do you need a folder in the pcg gallorie.....you can up load your image there and then post them in the forum

Bruce · Post by **Bruce** » Sat May 29, 2004 4:14 pm

Thanx for the offer Danny, I think I'll wait until I do something interesting before posting it. So far it's porcelin crab shots.
Did you recieve the heatsink I sent you?

B.

danny bruza · Post by **danny bruza** » Sat May 29, 2004 4:38 pm

thanks it works good for the controller to cool it down...im using parfin oil to cool the head heatsink fins.. rather than water

Bruce · Post by **Bruce** » Sat May 29, 2004 7:44 pm

While I don't know for a true fact I would be concerned that the parafin (lamp oil) vapors might leave some residue on the output coupler window of the laser as well as being very flammable.
Just a thought...

B.

danny bruza · Post by **danny bruza** » Sat May 29, 2004 7:53 pm

it seem to be ok.., ive run it for hours and no film on window as yet

Dinesh · Post by **Dinesh** » Sat May 29, 2004 8:50 pm

Keep polarisation in mind. If you shoot at Brewsters, you'll need to have the polarisation vertical. You'll also have to have the object beam vertically polarised, which may not be necessary if the object completely depolarises. If it doesn't however, you'll lose a lot of object light. If the object beam is vertically polarised in a horizontal plane, it'll be 's' polarised and so some of the object beam may cause woodgrain. Of course, none of this is important if you're doing single beam Denisyuks, unless the object is metallic. If you are doing single beamDenisyuks, be sure to choose objects that reflect mainly onto the plate. A vertical object will mostly reflect down to the floor, a horizontal object will mostly reflect away from the plate. Depending on the plate size/object size, at 72 inches focal length, you may not need a microscope objective, a relatively cheap negative lens will conserve more light. Of course you can't spatially filter this. It may be possible to use a positive lens and filter it. You need to work out the Airy disc diameter and make the hole size appropriately.