Infrared Filters advice, specs and where to buy

[m0f]

Hi, I am looking for some advice regarding infrared filtering. First of all, I'm playing around with various optics, mirrors and motors and eventually plan on building a small personal laser projector. I'm using a disassembled 15mw leadlight clamped to a heatsink it for a longer duty cycle.

Now I'm looking to add a red component. From what I understand in order to appear the same intensity as the green, somewhere between 80 - 100mw at 650 - 660 nm should do ? Being a diode laser (not dpss) from what I understand there should be no IR emmissions so filtration is not necessary. I just wanted to confirm that first.

Now onto my main question. In looking around I was looking at the sik series of laser projectors as a possible source of lasers and optics due to the great price they are offered at. Particularly the Red, green, yellow model which I imagine would include some sort of mixing mirror as well as the servo style scanning assemblies and in this particular case a 40mw green and a 100mw red. All in all sounds like some very useful parts and from what I can figure, purchased separately would cost way more than that.

Here's the problem, from what I have been able to determine from asking the sellers, it is not equipped with IR filters (at least that is what I was told when I asked). Now if I'm correct, the red shouldn't need one, however the green dpss is an accident waiting to happen. What would be entailed in adding an IR filter to their green dpss unit ? Where are they available ?

In searching I found this http://www.rosco.com/us/filters/protect.asp#IR-UV Down at the bottom are the "hot mirrors", which sound like it might be suitable however not directly designed for use with a coherent laser source. Any comments on this ?

After filtration I would imagine the power output would be around 15mw anyhow, so perhaps just replacing it with my modified leadlight would be the cheapest way.

They also sell just a red version which would save a bunch of cash, from which I could yank it apart and incorporate those parts along with my leadlight for a red and green projector. Only thing missing there would be a suitable mixing optic to obtain yellow.

Any advice would be greatly appreciated

Thanks

Miles

EDIT: I just thought of a possible source of IR filters. Perhaps removing one from a webcam ? Or would it likely melt given the intensity of the IR source ?

 

[jkaiser3000]

1.- All digital cameras (CCD or CMOS based) do indeed have some sort of IR blocking. Some inexpensive ones have the filter laid as a coating on the lens, so it would be useless for your particular application. Others do have a separate filter that will be useful, that is, if you're willing to butcher the camera in the first place . These filters will not melt under such low powered lasers, one less worry there :laughing:. I'm sure Edmund Optics will have some also, but can't give you a direct link. Try searching their online catalog.


2.- Red pointers do not need IR filters. As you said, they're directly injected, and therefore are lasing in the specified wavelength. Greens, on the other hand, are basically a crystal being pumped by an IR laser, hence the need for a filter.

3.- For combining red and green, you'll need a dichroic mirror that can reflect red and will transmit everything else, or one that will reflect green and transmit everything else. The projector that has red/green/yellow has one incorporated. If you go with the red projector only, you'll need one. There's a seller on ebay by the name of bjomejag that specializes in dichroic filters and mirrors.

4.- The hot mirror would work, but you need to realize that it will be reflecting the ir, not blocking it. If you use that, you will need to be weary of the IR reflections. You could reflect to a place where it will not be harmfull, or enclosing it in an IR absorbing material. I'd go for the filter instead, but it can be used if needed .

5.-

After filtration I would imagine the power output would be around 15mw anyhow, so perhaps just replacing it with my modified leadlight would be the cheapest way.

If you mean from the 40mw green in the projector, I'm not sure, but the filter should not block the green. If the 40mw is actual green output, then including an IR filter will not decrease the power. In either case, I'm pretty sure the green itself has an IR filter inside the module. Maybe the guy told you no IR filter in the projector itself (outside the laser)?. If the thing is outputing 40mw combined green/IR, then that thing is junk. I bet in that case green would be like 5-10mw.

Anyway, hope this helps

 

[Aiki1]

I was considering an SIK RGY projector as well.... how to tell if it has IR filtering on the green?? Got to make sure before purchasing....

:huh2: :huh2: :huh2:

 

[ajohnson]

You didn't say what seller, but there's more than one, including one that says they are the factory. Try specifically asking all of them if the green dpss has an internal IR filter. Hopefully you dont get conflicting answers Here's 2, but there's probably more:

http://stores.ebay.com/SIK-laser-lighting
http://stores.ebay.com/AixiZ-Service-and-International-LLC

I haven't bought from either seller personally so I make no statments good or bad about them. Apparently Craig (LedMuseum) has purchased from AixiZ, at least according to their ads, and reviewed a module that appears very similar to this one: http://cgi.ebay.com/650nm-100mW-laser-module-3-2VDC-w-adj-lens-650-nm_W0QQitemZ110028174291QQihZ001QQcategoryZ53141QQcmdZViewItem

now if I could just figure out how to post better links instead of these big huge things