Laser and Prism Help

[Guest joewhite903]

Ok guys this show im helping out with, They are doing we will rock you, now at a scene during the show there is a laser jail now me being me said yes no problems, so ive made the boards up with my 80mw green laser attatched now ive gotta work out how in the hell to split the beam ideally without moving parts. the idea is to split the beam with a prisim (but I dont know what one I need) then catch these beams with a load off mirrors attatched to the same board as the laser and bounce them down a load off holes in a line on the board so that when this is all mounted up it will shine down surrounding the person bellow, Hop u guys can help thanks Joe

[prolightdesigner]

From experience it takes a lot of fidgeting with a prism to get a consistent output pattern. (That's why lasers with built in prisms can be quite expensive). I'm not too sure what type of prism you need. I would suggest finding a few cheap ones and see what works best. Make sure the one you finally decide to use is the best quality you can afford. Splitting a laser beam and then reflecting it can really cut down on its intensity because it's no longer concentrated in one powerful beam.

 

-Jeff

[mikienorth]

Just use pinspots or birdies, with very very narrow angle lamps in them. Not being an expert with, but having used and operated lasers before in the nightclub/touring band business, I'd say an 80mW isn't strong enough to do what you want.

A shape made of birdies coloured to whatever colour suits the look, fitted with say 12 degree lamps will probably pack more punch than an (assumed) easily available mass market laser. If colour isn't important, but cost is, get cheap downlights from your local DIY, get the right lamps from an electrical wholesaler, and mount downlights into wood. No birdies, but same effect. To colour, fit a wooden edging aroound the side of the wood the light comes out of 2" deep, and loosley staple chosen colour to it. Loosley to give airflow, and 2" gap to prevent or lessen melting.

 

Laser, although a good idea, is difficult and very very very expensive to do well enough to be successful.

 

'Laser' on the other hand, or rather the look of laser beams forming prison bars can be a lot cheaper and more successful, sometimes design is all about acheiving the right look without using the right tools....

[live]

Hi Joe,

Ideally what you need is some two way 45 deg refraction mirrors most laser manufacturers will stock them (Lasertech, Laserelectronics etc) Another way is get one of the laserdiscs that you can mount on the front of your laser and will give you several options like vertical and horizontal lines and starburst effects but with a far more open angle (up to 45 deg),also you can motorize the disc (from memory the discs are about £40 but I can't remember off the top of my head who the supplier was) I've found Jessop's (camera shop's) to be a really good source for mirror's and brackets for lasers

good luck

g

[Brian]

As Jeff said above, once you split a laser beam you reduce the effective power. If you take you 80mW unit and split it 16 ways each beam will only be 5mW (assuming no loss in the splitters). Which as I'm sure you'll know isn't that bright.

 

Go with Ike's suggestion of pinspots. For a really tight beam have a look at these available as 4 degree units. Mount these lamps at the end of a piece of tube painted black inside to cut down stray light and you'll get a pretty good effect in haze.

[musht]

Narrow beam lamps going to look better than low power beams at oblique angle to viewers.

 

For splitting beams, diffraction gratings are the way to go:

 

http://www.laservisuals.com/gratings.htm

 

Checkout barcode scanners use a rotating disc of holograms of lenses rather than physical lenses.

[Guest joewhite903]

Ok guys looks like a refraction lens is out off the window £50, Guess my next option is Par 36's got 8 long cans and 4 short is there anyway off adjusting ther beam angle on them (Blackout ) Etc . Thanks Joe

[Ynot]

This effect has most certainly been discussed here - most notably THIS ONE.

 

But my money's on (for a budget effect) a decent powered quality profile with a gobo rotator and ring of 'holes' gobo, or maybe even a 575 or 1200W moving head - most will have a holes gobo as standard (or you can buy one).

 

Trying to do this with a cheap disco laser is going to cause you LOTS of problems, when the simple answer is right there.

Or in fact HERE...! :)