Eliezer From Artlaser Technology Co., Ltd

[Eliezer]

hei-hei, looks so much post on me.
Even like this "Some of the chinese manufacturers include the waste IR from the pump diode in the output specs of their DPSS units. "
I'm not anger about this. Just want to let every laserist know here, i come from a factory that with doing only laser machines. and we do the export ourself. I don't wanna lose the brand's honour-Artlaser in my hand.
Does anyone think there will be a third part like online-shop can sell more cheaper than me?
And i have to accept that some one in China like to bicker a little. But i will never do that, if u want to find the really cheap laser, contact big dipper, if u wanna find good quality laser, contact me.

Cheers
Eliezer

[buffo]

Eliezer;

I'm the one that posted the comment that "Some manufacturers include the waste IR power in their output figures." And I have seen FIRST HAND several lasers (including the F2000 Big Dipper RGB projector that DreamBeamz has) that specifically included IR power readings in the output specs. In that specific case, the unit is advertized as a "1.3 watt RGB laser" that really only makes 500 mw of visible light (400 mw of red, 50 mw of green and 50 mw of blue). Obviously, this is misleading.

DreamBeamz pointed this fact out to the buyers, and even tested the optical output (after installing an IR filter) to be CERTAIN that the power levels were correct. I simply mentioned the fact in my other post to remind others that this sort of thing DOES happen, and one must be aware of it. True, some manufacturers are producing units with *very* competitive price tags. However, there are also other manufacturers that are taking advantage of less-experienced buyers by over-stating the power output of their products.

I did not say that your company did this. I only advised that a potential buyer ask the question, "Do your lasers include IR filters?" before making a purchase. I believe it is a reasonable question to ask, given that not all units come with IR filters.

[RacerX]

In an RGB projector, wouldn't the dichroics already filter out the IR bandwidth negating use of specific IR filters on the module?

If that's true, why install IR filters at all?

Greg

[jkaiser3000]

That's a very good quetion .

I'm not entirely sure of the answer, but I suspect the dichroics could reflect/transmit SOME of the IR, as they are coated to work primarily on the visible part of the spectrum. Perhaps those coatings do not work well in the IR?.

It also depends on the arrangement. For instance, if you combine a green laser with a red one through a dichro which reflects red and transmits green, then IR will also go through the dichro. You then combine the blue with a dichro that reflects blue and transmits everything else and you'll end up with most of the IR from the green laser.

Either way, you could find an arrangement in which all IR will be eliminated. At least I think so :P

Just my thoughts

[buffo]

In an RGB projector, wouldn't the dichroics already filter out the IR bandwidth negating use of specific IR filters on the module? If that's true, why install IR filters at all?

Good question Greg!

The answer is twofold: I'll answer the second question first...

The reason you always install IR filters on a laser is because you do not know where the laser will be installed. Thus you can't be certain that there will be an IR filter downstream of the laser. I've never seen a US or European made DPSS laser that didn't include an IR filter on the laser output aperature to prevent IR output. (They also use really good coatings on the reflective optics inside the laser to keep the IR inside the cavity in the first place, where it can be used to make more power, instead of letting it leak out and be lost.)

But I have seen a few Chinese manufacturers use substandard coatings (which allow more IR to leak through the doubling cavity) and omit the IR filter at the aperature, presumably in an effort to save money. This is contrary to industry practice, both because it's wasteful (need more IR pump if you use cheap optics that leak) and dangerous (because you've got no filter to block the IR from the output yet the user expects the filter to be there.)

After all, you're buying a DPSS laser because you want the 532 nm light (or the 473 nm), not the 808nm or 1064 nm light. (Ok, 946 nm for the intra-cavity IR on a DPSS blue.) Bottom line, you're not buying an IR laser, you're buying a visible laser. So why would it be acceptable to have 5 times the visible output (or even more) present in the form of IR leakage? (Hint: It's not.) This is a real beef that I have with some Chinese manufacturers... :?

You first question is a little more complicated: First, dichros are frequently spec'd for the visible spectrum only. To add wavelengths beyond this range costs extra money. (To add wavelength bands IN GENERAL costs money, so the more bands you add, the more you pay.) Because they are only spec'd for visible light, their performance is questionable outside of the listed visible frequency range. (For example, nearly all dichros I've played with are completely transparent to 1064 nm, and most of them will pass a significant amount of 808 nm too.) Even a dichro that is designed to pass blue and green but reflect red will likely pass a good amount of 808 nm IR. (Not to mention 1064nm, which by the way is completely undetectable to the human eye - at least until it starts cooking!)

Now, if you put the red laser first in your projector (furthest away from the galvos), and then mounted the blue and green lasers at 90 degree angles to the red beam and used dichros to combine them, you'd probably do a pretty good job of filtering out any leaking IR from the DPSS units. (since it would pass through the dichro and hit the inside of the case) However, it's expensive to make blue photons, and also quite expensive to make a *lot* of red photons, while green photons are cheap. Each time a beam passes through a dichro you loose a little power, and this figures heavily into the order in which lasers are installed in a projector.

So you typically see the green laser at the back of the beam path, which means any stray IR from that unit will end up at the output. (It's a toss up as to which laser goes closest to the galvos, but it's nearly always either the blue or the red, depending on which one you'd rather lose less of.)

Adam

[JimBo]

How do you know if your laser has got an IR filter?

Jim

[RacerX]

Adam,

Thank you for the thoughtful and detailed reply.

It all makes sense now.

Greg

[buffo]

Jimbo:

Apart from taking it apart and looking for it, an easy way to tell is to pass the beam through a prism and let it shine across the room to a far wall. (This allows the IR to separate from the visible beam, since it will be refracted less than the higher-wavelength green.) Now place your power meter just to the side of the green dot on the wall. If you get a reading, then you've got leaking IR.

If you don't have a power meter, you can try using a video camera, or even a web cam, and the same prism trick above. They are sensitive to IR as well as visible light, so they'll show a bright spot if there is IR leaking. It might be tricky getting the camera just to the side of the green beam; you may want to cover the lens with a carboard mask and then cut a wide slot in the center.

Remember, you want the prism close to the laser and the wall where the dot is projected to be far away (15 feet or more). That way the two beams will separate completely.

Another way is to purchase (or borrow) an IR filter and place it in front of the laser. Now take a power measurement. Then remove the filter and check the power again. If the two readings are only a couple mw apart, then you're not leaking any IR. If they are a couple hundred mw apart, then you're leaking lots of IR!

Adam

[JimBo]

So there is no simple way?
I thought they might put the filter on the apperature of the laser.

Looks like I need to add a lasercheck to my wish list.

Jim

[RacerX]

What about using something like this after the prism to view the IR? Wouldn't measure it, but you would know if it was there.

Edited for 808nm check.

Thanks Adam.

http://shop.mellesgriot.com/products...39312&mscssid=