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That depends on the country. In Germany there was a court case a couple of years ago about selling "unbundled" versions of OEM SW (from a reseller dealer who got PCs with XP on them, but wanted to sell them with Linux installed). Microsoft fought hard against this, but they lost... so here it IS...

On the same vein: why do anti-cellphone-radiation protectors exist, why do anti-earthray (don't know the proper word, it's supposedly harmful radiation supposedly emanating from "water veins" and odd rock formations and what not) protectors exist, why do electromagnetic water-decalcifiers exist...

From the description it sounds like they're just using better quality lenses...

@Grix: where does it say that? I just get "OD4, 60%VLT" for the 532nm goggles (SKG-06) in the "Detailed product description" table.

I think that getting lots of neg-reps is less a reason for banning than giving lots of them... unfortunately that's something you don't see in a persons profile.

No, that's wrong. Even with 50% air, you could have nearly the same conductivity (but less heat capacity). Heat conductivity depends on the contact area between particles, not on the amount of empty space - that affects only the heat capacity. The air, being essentially a non-conductor of heat...

I've read somewhere around here that someone had made a hologram of a small object (~6cm) using an LPC-815 diode, so it should be possible... I was searching for info on "coherence length" at the time IIRC.

A common binocular contains many optical elements for correcting color dispersion (chromatic aberration) and for turning the image right-side-up - you don't need either in a beam expander; all air/glass interfaces reflect and scatter a certain amount of light so the fewer there are, the better...

I've bought a green laser on the streets in Shanghai (they're selling them at every corner), and divergence seems to be better than 1mrad as well. It looks little worse than my red, which is about 0.5mrad (measured over 45m/150ft). I've done no measurements yet, however. Note, using a mirror to...

Finding the right material (crystal) is exactly the problem.... however, the research direction is more in replacing the complex, expensive and finicky DPSS setup by something that lases directly in the desired wavelength.

As I've mentioned before, the OD rating is pretty irrelevant in this case. Generally an OD rating is used if you want to look at the spot in comfort for focusing. IT DOES NOT TELL YOU HOW MUCH ENERGY THE GLASSES CAN WITHSTAND, so focusing (pun) on OD is a grave error. What you want here, is...

Can it be that you've asked that several times before? It would be possible, however the problem is that you'd get a pretty bad beam divergence (because you'd be reducing not just the beam separation, but the beam diameter as well. Low diameter=high divergence). On second reading, I'm not sure...

I have in the meantime used these glasses at a fireworks show. The video doesn't half do them justice; in fact, when watching it, I just kept on thinking "Stop fiddling with the focus, you &^%$#@!" :D (I realise it was just the autofocus which couldn't handle the low-light situation). Each...

Quite correct.

Addendum: if you play around with the formulas, you can determine the grid constant, given lambda, d and D. For these glasses, it works out to a grid spacing of 4870nm, or 205 lines/mm, or 5200 lines/inch. I'll leave it as an exercise for the interested student to find the formula (it's trivial).

For people wondering what to do with these, I have now posted the description of two simple yet worthwhile experiments you can do with them (and your lasers) in the Experiments & Modifications section: What to do with your diffraction glasses I: wavelength determination What to do with your...

3 weeks ago I bought a couple of these diffraction glasses from Alexzupinhea. After they arrived, I played around with them a bit and came up with two simple-to-do experiments which may have some practical merit for one or the other. The first one is on how to check your lasers wavelength. This...

3 weeks ago I bought a couple of these diffraction glasses from Alexzupinhea. After they arrived, I played around with them a bit and came up with two simple-to-do experiments which may have some practical merit for one or the other. The first one is on how to check your lasers wavelength. The...

Since you'd normally set all diodes to the same current anyway, you can just wire them all in series and use a single driver - that way they're guaranteed identical currents. Due to variations between diodes, they would all output slightly different amounts of power, but again, it'd be the same...

Even in a perfect world, you'd get divergence. It is caused by the wave nature of light, not by technical imperfections. Because of its lower wavelength, a violet beam would have less divergence than a red one, all other things being equal. Yes, skin is partially transparent to red light...