Good spot to get lenses suitable for IR?

[con-f-use]

I'm looking to repeat this build. So I want to project IR dots on my wall for use with a Wii Mote (940nm). I can't really find a source for suitable lenses. I don't want to spend more than 20 $ for lenses and shipping. Do you know a place to get similar lenses as in the picture? He uses aspheric lenses with a f=26mm but that's not that critical. Any converging lense with a small focal length would do.

[jeremy]

It looks like these are the one he used: http://www.aliexpress.com/item/L01-1SET-78mm-Lens-82mm-Reflector-Collimator-Base-Housing-85mm-Fixed-bracket-For-100W-High/615667269.html

Plenty of other lenses on aliexpress, just search for "aspheric lens"

[con-f-use]

What worries me: they don't give a focal length on many of them.

[jeremy]

You're trying to get one for $20, you can't have everything and even if it is specified, it is probably wrong.

If you want well characterised lenses, go to thorlabs. But you'll pay for it; a proper aspheric lens that size would easily go for >$1000.

[miguelvp]

You're trying to get one for $20, you can't have everything and even if it is specified, it is probably wrong.

If you want well characterised lenses, go to thorlabs. But you'll pay for it; a proper aspheric lens that size would easily go for >$1000.

Edmund optics will be cheaper but I doubt you'll find something for $20.

http://www.edmundoptics.com/optics/optical-lenses/aspheric-lenses/

Hopefully a regular lens works on the NIR band, specialized NIR lenses might cost more. Also using fresnel lenses might do the trick.

[miguelvp]

I would think the WiiMote will work in the NIR band, so that's why they are using regular optics.

The project you linked is based on another that was using a fresnel lens and as far as I can tell it was a regular visible light lens as well.

Here is a link for materials for IR and the overlap for Visible as well.

http://www.edmundoptics.com/technical-resources-center/optics/the-correct-material-for-infrared-applications

Just any optical lens should have no problem in the NIR range I believe.

[David Hess]

You might find something suitable over at Edmund.

http://www.edmundoptics.com/optics/optical-lenses/plano-convex-pcx-spherical-singlet-lenses/mega-clearance-optics/3390

[con-f-use]

The cheap laser modules I found in a quick search are out of the wavelength range the Wii can detect. Also I worry for people's eyes. Also I have a bunch of 2W IR leds around for illumination of security cameras, I install for a client.

I ordered a few cheap lenses from Alixpress. I'll see how that goes and get back to you. Thanks people!
I really like the helpful attitude in the forum!

Edit: Strange, the laser diode post from before disappeared!

[MK]

look at the variation of focal length with wavelength, you may need to consider the difference for the IR wavelength you are using, it may need some research to find the curve for the lense material you end up buying.

[miguelvp]

Or get a cheap webcam, remove the IR filter and add a visible light filter (dark exposed film/or floppy magnetic material) and use that to see how focused the spot is. You only have to find the right focal point from the emitter to the lens.

Might show also on an unmodified camera phone while previewing video, at least well enough so that you can adjust it if the wavelength changes the focal point by that much.

I wouldn't think Near IR is going to change the focal point that much from visible light.

[con-f-use]

Cell phone camera in the dark works well for my IR Leds. I can see the glow on the wall from about half a meter.

[mzzj]

Or get a cheap webcam, remove the IR filter and add a visible light filter (dark exposed film/or floppy magnetic material) and use that to see how focused the spot is. You only have to find the right focal point from the emitter to the lens.

Might show also on an unmodified camera phone while previewing video, at least well enough so that you can adjust it if the wavelength changes the focal point by that much.

I wouldn't think Near IR is going to change the focal point that much from visible light.

some older slr camera lenses even have separate focusing marks for infrared.

[MK]

I wouldn't think Near IR is going to change the focal point that much from visible light.

Unfortunately it really does depend on the lens material in use.

[westfw]

You should check out http://www.surplusshed.com/ - surplus dealer specializing in optics.
As other have said, normal glass and plastic lenses should work fine at "near IR" wavelengths, with slightly different focal lengths; you only need exotic materials when you start talking about "thermal" wavelengths (and also want to filter out the visible wavelengths.)
I used to do some experiments with 35mm Infrared photography: Kodak has/had a film sensitive to IR that you could get in most camera stores, and process with normal chemistry.  It worked fine with normal cameras with normal lenses.

(I'll also add that there is a pretty significant market in used camera lenses on eBay/etc (and in many general purpose technical surplus stores.)  Now that everyone wants digital cameras with super-zoom lenses, the old film camera fixed FL lenses are selling for pennies on the dollar.  Why fiddle with simple glass when you can buy high-quality optics with focus rings, arperatures, and mounting hardware for similar prices?)

(Finally, the little plastic lenses found in disposable cameras are apparently pretty good...)

[rs20]

+1 to SurplusShed, have bought from them before and will do again. Lenses are listed with a focal length and diameter (two most important things), but not complete dimensioning/drawings.