Holographyforum.org / holowiki.org

I don't have one, but I saw a cheap filter on eBay from someone in the UK, that transmits 532 but blocks everything between about 750 and 1100 (rough estimate based on memory). It was about $15. Im not sure if I should get the filter, or just plan on buying a cheap lab-style 532 laser that puts out a constant power. (All I need is about 10mW)

Doesn't the ir have much worse divergence than the 532? How about just some distance between the laser and the sensor?

I was playing with a green laserpointer and a prism a while ago, and took a picture of it through an IR viewer. The three blobs are the 532 (small one on the left) 808 (big blob in the middle) and 1064 (small one on the right)

http://www.bobdbob.com/~tjohnson/lab/20 ... 55.jpg.jpg

I was surprised at how badly it leaked.

The better ones have better IR blockers so that they can have more green light and not exceed 5mw since the law specifies total output not green output. You can upgrade the IR blocker as well and dial up the power on the LD driver board. If you bounce it off a DVD you can get more spread and measure the powers separately. Back when they were very expensive I modified one for a few weeks but I finall broke it trying to press fit the diode case into a better heatsink. Mine would drop in power when warm.

Jeffrey Weil wrote:Doesn't the ir have much worse divergence than the 532? How about just some distance between the laser and the sensor?

Thanks for the tip, but the output power is so irregular, that it's difficult to get a handle on things. But after the pointer settles down a bit, it produces a fairly decent yellow with the HeNe, and is good enough for my current needs. Probably I should upgrade the pointer with a cheap lab laser (with stable output), and those types of laser should have a decent filter to block the IR.

Joe Farina wrote:

rzeheb wrote:I wonder how much of that 188 mw was really IR?

Upon further testing, maybe a lot.

Today I got an IR filter which blocks everything between 700 and 1100nm, but has 85% transmission at 532. With my Lasercheck set at 532nm, I took three readings of the 532nm pointer: without filter 172mW, with filter 31mW; without filter 136mW, with filter 26mW; without filter 136mW, with filter 20mW.

So a lot of IR, but also a lot more 532 nm than advertised. Unless the filter is unable to block all of the IR. It might be worth trying to expand the beam a bit and try your test again. That way all the energy doesn't have to pass through a very small part of the filter.