Typical Question for a Non-typical Project! (Scan Effect)

[Boomerjinks]

Hey folks!

I've been lurking here for a little while as I try to get myself up to speed with laser terminology and functionality, and I'm afraid I've hit a bit of a brick wall. It's my own fault, as I seem to be having trouble translating this huge wealth of information into knowledge that applies to what I am working on.

So please, please please forgive my newbishness. I'm positively certain you've heard these questions before, and I'm certain the answers lie embedded somewhere on this forum, I think I just don't know the right words to plug into the search function!

Oye. Anyway.


To make things real brief, I build replica movie cars. I've got a Jurassic Park Jeep and a modern Ghostbusters replica. I run a movie car club, we've got everything from the General Lee to a few KITTs, DeLoreans, a Bluesmobile, Batmobile, etc. It's real fun. Each year I try to equip one of my cars with some new geek-tastic gimmick - last year we put a giant firetruck siren in the Ectomobile, the year before that we hookup up a sound chip in the Jeep to make the horn play different dinosaur roars.

This Halloween, I'd like to equip the Ecto-1 with "scanning lasers." The goal is to have the car on display outside local haunted houses, with a colored beam sweeping back and forth across a building or display. Something in the same family as this:

... only vertical, and a little more animated (I already tried this with a laser level and I could not get the desired effect).

The big goal is to be able to see something like this:

but with a visible beam of light "scanning" whatever is in front of the car.

My only requirements for the beam movement is a 90-degree side-to-side sweep and steady-on without any sweep.

A few things:
-yes I understand the hazards of having lasers on a vehicle, this is for when the car is on static display only
-yes I understand the hazards of scanning lasers and people, this is not for aiming at people
-yes I understand that the beam is likely going to be invisible 90% of the time, this is for combined use with atmospheric effects like fog and steam

Another hurdle is size. I need the laser unit to have a footprint not much larger than a discman. Larger, bulky 10"x10"x6" projectors or small suitcase units will be too big for mounting on the car (aesthetically).

So yeah! That's what I'm looking to accomplish, hopefully as inexpensively as possible, but I fully realize that cool laser effects aren't cheap

I would greatly appreciate any suggestions or advice available. I'm sure someone in the For Sale sections probably sells exactly what I am looking for, I just don't know what to look for!

Thanks again, this place is such an awesome wealth of information!

 

[rhd]

Hey,

So it strikes me that you need two things:

1) A component that will turn the single round beam into a "fan" like shape.
2) Something to move the fan 90 degrees back and forth

You could accomplish #1 with the type of mirror used for a liquid sky effect. Number 2 has less to do with lasers, and more to do with general mechanical engineering, so I'll let someone else tackle it.

For the liquid-sky like effect in #1, If you'd like a hex mirror, on a brush-less motor, I have one that I can send you.

 

[Guyfromhe]

To do #2 you could take #1 and put it on a servo or a motor that moves back and forth.. Something like a oscillating fan would work but it would be big... You may need to do a micro controller or something..

I know you should go with green as it's way more visible than anything you will get with a red laser level... If you go with something under 5 mW it should be safe (particularly if it's moving) If you are sure it will be above the heads of onlookers you can go with a more powerful laser and get a much better beam effect....

I want the Jurassic Park jeep!!!

 

[Boomerjinks]

Oh cool!

What would you guys recommend for somewhat powerful emitter (visible without fog) that is also inexpensive?

And yeah, green is what I was thinking, too!

 

[Guyfromhe]

I got one of these: 200mW 532nm Green Laser Pen (2*AAA) - Free Shipping - DealExtreme

It was $30 I don't know how long it would last running it continuously...
It has a great beam in the light (even indoors with the lights on and no fog) and an super beam in the dark... and it's cheap as chips...

You could always give it a shot and see if it does what you need... Otherwise you can look at a lab style brick laser....

I would say probably at least 60-80 mW of actual power would be needed for a half decent beam with no fog... (Keep in mind most inexpensive units are wayyy under spec)


EDIT: pics of the JP jeep!!!!

 

[Boomerjinks]

Sweeet!

Can I just disassemble that pointer and wire it up to the car? I'd imagine I'd need something that is meant for 12v?

Also, here ya go!

Check out Colorado Movie Cars on Facebook for waaaaay more fun!

 

[chipdouglas]

i feel jipped!!! replica is replica. not new car with decals. also rhd is correct. to have a visible sweeping pattern you will too much power which will not be safe around people. especially since it will be rigged on a car.

while the idea is very cool. i think it is not worth the risk to the public.

michael.

 

[Guyfromhe]

Sweeet!

Can I just disassemble that pointer and wire it up to the car? I'd imagine I'd need something that is meant for 12v?

Also, here ya go!
Check out Colorado Movie Cars on Facebook for waaaaay more fun!

It's hard to take that one apart.. You can also buy diode modules from users here or one of that zillions of sites that sell them like DX or o-like or TMart or anywhere really.

As far as safety I wouldn't want to be in charge of something like that but it's your neck...

I like the JP car much better than the Ghostbusters one it doesn't have the same feel as Ecto-1 it's too roundy...

That JP jeep is cool... what does one of those run??

 

[benmwv]

I think what you are looking for is a line generator lens on a green laser with a mirror to move it back and forth.

You can get the lens at o-like.com.

For the laser I suggest a 50mw green laser module, also at o-like. Many people will say to use a 5mw laser for safety, but there are a few reason why you can/should use a 50mw:
-Since you are projecting a line the laser's power density will be reduced to less than a 5mw pointer within a couple inches of the aperture.
-You should be able to see it with some smoke/fog much easier than a 5mw.
-You say you won't be shining it on people, and if anyone did happen to get hit in the eye it's likely that they will be a good 10-20 feet away at which point the laser would be far from dangerous.

Now for the problem of turning the mirror... I guess you could mount it on a servo and use like a flip flop circuit to change from turning it left to right. Google "astable multivibrator".

 

[Boomerjinks]

For the laser I suggest a 50mw green laser module, also at o-like. Many people will say to use a 5mw laser for safety, but there are a few reason why you can/should use a 50mw:
-Since you are projecting a line the laser's power density will be reduced to less than a 5mw pointer within a couple inches of the aperture.
-You should be able to see it with some smoke/fog much easier than a 5mw.
-You say you won't be shining it on people, and if anyone did happen to get hit in the eye it's likely that they will be a good 10-20 feet away at which point the laser would be far from dangerous.

Awweeeeesome info!!!

Do you guys think I should find a way to turn the lens back and forth, or the whole assembly? I mean, turning the reflector will work just as well, right?

 

[benmwv]

Yeah you should just glue the lens onto the module (don't use super glue, it will fog the lens) and just turn the mirror to move it.

 

[Boomerjinks]

Someone pointed me to these things.
COPAL POLYGON MIRROR LASER SCANNER - Surplus Shed

Any knowledge of their capabilities here?

 

[Cyparagon]

A simpler and solution would be to use a line generating lens.

 

[DrSid]

Imho go for static line lens. It's so much easier then scanner. Scanner will provide homogeneous brightness, but today's line lens will usually do the job just as well. It could also be safer, because scanner can stop working.

 

[Boomerjinks]

So I'm checking out line generating lenses, what should I look for? How much should I be paying? Any specific terminology I should look out for?

 

[DrSid]

Something like this, yes it is that cheap:

line and cross line generator lens [OL-L-8mm] - $3.00 : Welcome to O-Like.com, Your source for laser products

These are plastic, but I run them with 400mW green without problems. You just have to keep them clean.
You can also find lens like this in cheap red laser water level. It might come only marginally more expensive then ordering it from Singapore (IIRC o-like is Singapore, right ?). But generally if you will order laser from someone, there is good chance he will sell some gratings too.