trying something a little different...

[GoolGaul]

Hey all:

(I don't know if this is the right section to post this in, so don't slap too hard if you break out the trout)

I want to build something similar to an old-school radar display (you know, with the slowly rotating green radius).

My Plan: Use a stepper motor with a FS mirror @ 45 deg. angle. Mirror protrudes thru a center hole in a (fill in the best material for this concept) disc. Laser shines at mirror and gets bounced into the inner edge of (material above) disc, radiating out to the perimeter...

Here is the catch: It's gotta be a low powered laser, yet be highly visible while in the mystery material.

This disc should be about 24" diameter, giving a me 12" long line in the disc...

The perimeter would be painted black as a beamstop. (again reinforcing the need for lower-powered laser)

Thanks in advance and any advice is greatly appreciated !

[swamidog]

how about just passing the laser through a slowly rotating line grating?

Hey all:

(I don't know if this is the right section to post this in, so don't slap too hard if you break out the trout)

I want to build something similar to an old-school radar display (you know, with the slowly rotating green radius).

My Plan: Use a stepper motor with a FS mirror @ 45 deg. angle. Mirror protrudes thru a center hole in a (fill in the best material for this concept) disc. Laser shines at mirror and gets bounced into the inner edge of (material above) disc, radiating out to the perimeter...

Here is the catch: It's gotta be a low powered laser, yet be highly visible while in the mystery material.

This disc should be about 24" diameter, giving a me 12" long line in the disc...

The perimeter would be painted black as a beamstop. (again reinforcing the need for lower-powered laser)

Thanks in advance and any advice is greatly appreciated !

[GoolGaul]

I thought about using a line grating, but then I need some distance to project. Front-projection wouldn't work as viewers would potentially block the laser. Rear Projection wouldn't work either as I need my display to be as flat-ish as possible.

That's why I wanted to shoot a beam into the edge.

I know that the nature of the material I am seeking is quite opposing to the nature of materials laserists would normally use.

(BTW - I had hoped that you'd chime in SwamiDog!)

[Stoney3K]

You're never going to get 360 degree coverage if you use a motor, unless your source laser is aligned with the axis of the 'screen'. There's going to be something sticking out on either end if you do it like that, be it the motor driving the mirror or the source laser on the screen axis.

If you want the beam to be visible in your mystery material, it has to be somewhat opaque. Something like 25% smoked acrylic would be a good bet to start with, depending on the power of your laser.

Otherwise, you could even build a (fairly) air-tight cylinder with acrylic faces on either end and blow smoke into it with a fog machine and a fan.

[GoolGaul]

the motor would be behind the disc and would have a FS mirror at a 45 deg. angle. the laser would be bounced from behind the disc, then w/ 2 x other stationary 45 deg's would bounce to the mirror on the motor, which would then align the beam into the inner edge of hole in the center of the disc for 360 coverage.

I am resigned to having something that sticks out of the front of the disc, as I can't think of a way to do it simply (aka cost-effectively & reliably).

[stateside]

Hi, Hope you dont mind me comming in. I had to do the same for a stage producton. I didnt use a laser at all. It was a plexiglass disc around 12" but you can make it bigger, a dark green filter gell behind with a small slot from center to the edge to represent the beam. Its back lit with 20 watt 12v lamps or leds. The disc is driven at around 20 rpm from the center and on a stage looks the bees do da's. Any help!

[Stoney3K]

Hi, Hope you dont mind me comming in. I had to do the same for a stage producton. I didnt use a laser at all. It was a plexiglass disc around 12" but you can make it bigger, a dark green filter gell behind with a small slot from center to the edge to represent the beam. Its back lit with 20 watt 12v lamps or leds. The disc is driven at around 20 rpm from the center and on a stage looks the bees do da's. Any help!

I doubt GoolGaul wants something that looks exactly like a radar display. Because that would have been easy, anything that can display an image that's big enough (like a 32" flat screen) is a lot easier to use.

Given the fact that he want to use lasers, I suspect the piece will need to be partly transparent when viewed from either end.

[GoolGaul]

Thanks Stateside for chiming in. cool idea and infinitely easier than what I am trying to do, but not quite what I was looking to achieve.

Stoney has the right idea though. Transparency (or translucency) is key... not exactly like a radar screen as you pointed out, but that is the general concept...

[Eidetic]

A holographic directional diffuser might work. Transparent to light that goes straight through, diffuse for light coming along the reconstruction path. Anamorphic distortion of the line pattern going in along the off-axis reconstruction path would need to be considered. Just a thought.