Wednesday, December 8, 2010

Reflector Beam

Reflector beams.
I thought about this for some time, toying with different ways to put it together, and decided that given the materials on hand this was the way to go.
First I had to make the initial frame which was pretty straight forward, except for making sure that the top and bottom which held the mirrors was parallel, to do this I made the top on a swivel.
That sorted, the next area I looked at was the laser, I needed some way to be able to adjust it for angle and align it centrally, for this I found a piece of electrical conduit pipe with a socket on the end, I cut two 1/4 inch pieces from the socket, and a suitable length of the pipe, slipping the socket pieces onto the end, this at first was a little tight, but rubbing the inside with some sandpaper eased it nicely. I drilled a hole in the centre of the pipe to fit the laser, which was held in place with a little super glue.
The placement of the detector, depends on where the beam end's. The circuit  was  that used in the Crossbeam article.
Adding power to the laser and trying to align the beams proved to be much more difficult than I had imagined, instead of getting a nice line of laser dots I got an arc, but by lifting the opposite end to the laser did straighten the dots to a useful degree, but the dots were not an equal distance apart. This was quite a puzzle to me at first, but on doing some research, I found out that the main problem was caused by refraction, as far as I could make out, the first  reflection bounced of the glass surface, another passing through the glass got refracted, was then reflected by the mirror surface and refracted again, this happened over and over again.
I had heard about surface mirrors, so again made a search of the internet, and found that someone making Spirographs had found a method of removing the protective coating on the back of the mirrors. So I tried this method and it worked perfect on both glass and Acrylic mirrors.


1. Mirrored Acrylic, or Glass Mirror.
2. "Mötsenböcker’s Lift off 5 Latex Based Paint Remover" . This is the one I found here in Australia.
Mötsenböcker’s doesn't damage the mirror surface or the acrylic at all. You have to let it sit for awhile though, about 5 - 30 minutes. You shouldn't have to "rub" to get the paint off, if you let it sit long enough, the paint will just float off.
3. Once the paint cracks up, remove it from the lift off and rinse under running tap. the liquid can be returned to it's container for  reuse.
4. let it Dry, then polish lightly with soft cloth to remove any water smear.
Another product that works equally well is "Winning  Colors Stain Remover". ("not found here in Australia").
Both are available in the USA.
Ok, here's the big question ("Did it work ?") Well yes in the first instance, to a fashion that is, but not how I wished as explained above, but since using the surface mirror idea, things have changed.
I still got the arc, but with a bit of adjustment of the Laser itself, it worked fine, it does take some fiddling but the end result is pretty good, I managed to get the gapes between the beam dots to about 1/2 inch apart.
Not sure how this would work on a larger scale, it may need to use two laser’s.
Being as my Olympus E520 camera has a shutter lag of 500ms I can’t do any real trials outdoors, But I am in the process of making a unit via an Arduino that will allow me to use the Panasonic FZ50  which they tell me is pretty quick, time will tell.
Reflected beam
Reflector beam
This photo was taken before I changed the mirrorsOLYMPUS DIGITAL CAMERAOLYMPUS DIGITAL CAMERA

Here are a couple of examples taken in the dark via flash, will try to add some real-time camera shots later


Glacial Wanderer said...

I understand the problem when not using surfaceless mirrors. However I don't understand your solution and I'd like to since a surfaceless mirror is harder to find. By removing the protective coating on the back of the mirror are you just making it a standard piece of glass? That seems like it would have an aweful low efficency rating for a mirror since most of the beam isn't reflected by the glass... Could you explain how removing the protective backing on the glass helped?

Ernie Hatt said...

Maurise, what happens is you are only removing the backing, and leaving the mirror surface in tact.
What you end up with is in fact a double sided mirror, one side the conventional one, the other is you surface mirror, the one I am using here. Ernie