Has anyone tried these lenses with their PHR?

[kernelpanic]

Hello All,

Found 405nm collimating lenses on ebay-

http://cgi.ebay.com/Bluray-Laser-Di...39:1|66:2|65:12|240:1318&_trksid=p3911.c0.m14


Just wondering if anyone on this forum has tried them... and how well they work.

cheers,
kernelpanic

 

[IgorT]

That's a lens dug out of the PHR sled. I tested it and all the others long ago, and later again when someone asked this same question.

It's useless for pointers, because of the long FL. By the time the light cone gets to the lens at focal distance, it has diverged so much, that most of it simply misses the lens. The part of the light cone, that does hit the lens forms a massivelly thick perfectly round beam with a diameter of the lense's effective diameter, perfectly round, because everything else just misses the lens. My 6x which put out 190mW after an AixiZ lens, only did 60mW after this lens in "parallel" focus. If you bring this lens very close, it will pass more light, than an AixiZ lens, but it will be completelly out of focus.

The lens is made to work as a part of an optical train. It can't work as a single element, even if you had a way to mount it. Well it can work, just not as described.


It's just people from this forum trying to make money of what they would otherwise be throwing away, using lies or half truths, consisting of stuff picked up here, in order to attract customers. This same person sells de-canned PHRs as "150mW Sharp diodes - open can type" IIRC.


You can dig this lens out of any PHR sled and test it yourself. It's just above the focusing assembly. It's a lens with such a long FL, that it looks flat.
Also, the FL is not 10mm but closer to 27mm.

 

[kernelpanic]

That's a lens dug out of the PHR sled. I tested it and all the others long ago, and later again when someone asked this same question.

It's useless for pointers, because of the long FL. By the time the light cone gets to the lens at focal distance, it has diverged so much, that most of it simply misses the lens. The part of the light cone, that does hit the lens forms a massivelly thick perfectly round beam with a diameter of the lense's effective diameter, perfectly round, because everything else just misses the lens. My 6x which put out 190mW after an AixiZ lens, only did 60mW after this lens in "parallel" focus. If you bring this lens very close, it will pass more light, than an AixiZ lens, but it will be completelly out of focus.

The lens is made to work as a part of an optical train. It can't work as a single element, even if you had a way to mount it.


It's just people from this forum trying to make money of what they would otherwise be throwing away, using lies or half truths, consisting of stuff picked up from here, in order to attract customers. This same person sells de-canned PHRs as "150mW Sharp diodes - open can type" IIRC.


You can dig this lens out of any PHR sled and test it yourself. It's just above the focusing assembly. It's a lens with such a long FL, that it looks flat.

Thanks fior the info. I figured the 10mm focal length would be a deal breaker. But I did find modules that'll take the lens. Glad I didn't bid/buy as I've already got half a dozen of these lenses, LOL

Thanks,
kernelpanic

 

[IgorT]

Yeah, but it's not really 10mm FL. It's 27mm FL.

The thing is, most people who would buy that wouldn't know how to use it anyway, so they would never figure out they were ripped off.


It just annoys me to see people using info picked up from here, to misrepresent a product and make it sound better than it is.. I have here in front of me 30 lenses custom made of glass and AR coated for blu rays, that work in AixiZ modules and actually do increase the power, but i don't want to sell them, because they are spherical lenses and create mess around the dot. Altho the beam is nice and thin.... Maybe i should give them to that person, he can sell them and we split the profits?  :

 

[kernelpanic]

Yeah, but it's not really 10mm FL. It's 27mm FL.

The thing is, most people who would buy that wouldn't know how to use it anyway, so they would never figure out they were scammed.


It just annoys me to see people using info picked up from here, for scamming. I have here in front of me 30 lenses custom made of glass and AR coated for blu rays, that work in AixiZ modules and actually do increase the power, but i don't want to sell them, because they are spherical lenses and create mess around the dot. Altho the beam is nice and thin.... Maybe i should give them to that person, he can sell them and we split the profits?  :

I say sell 'em here. As long as buyers are aware that they are spherical lenses I see no problems. Those that want a 'clean' dot won't buy them. But for a burner they'd be great... And you could recover some of your R&D costs. (I'd definitely be interested in buying one or two myself should you decide to.)

Again, thanks! Buying laser parts online is often a crapshoot. This forum really helps wade through the sewage that is ebay.

cheers,
kernelpanic

 

[IgorT]

Several people suggested offering the spherical ones for sale, to offset the "R&D cost"..

I wouldn't want to give all of them away, but if anyone wants to try one, i wouldn't mind selling some at a reduced price, to get at least a bit back... I posted pictures of what they do in the custom lens thread..

They make a ridiculously thin beam, that burns you even when it's parallel. And as long as you don't look at the spot, all is good.  ;D Also, i know how to remove most of the "wings", by lowering the NA...

Hmmm....  :

 

[daguin]

One man's trash is another man's treasure

Peace,
dave

 

[kernelpanic]

Igor,

I want! PM sent...

cheers,
kernelpanic

 

[kernelpanic]

To the person who sells these lenses.  Assuming you're a member here step up and defend your 'product' on this thread, please.

Thank You,
kernelpanic

 

[lasersbee]

Hey Igort,
are you saying... that the 405 lenses being sold on eBay can not be
used to collimate a 405nm Laser Diode if I have nothing else ???

I've actually tested these exact lenses and you can collimate the 405nm beam.

If you don't have a perfectly coated (for 405nm) glass/plastic lens or any other
kind of 405nm collimating lens then these sled lenses will work.

Jerry

 

[IgorT]

No LaserBee, you misunderstood me.

Of course it can collimate the beam, that's what it's made for. You can use this lens or any aspherical lens of the right properties to collimate a laser beam. I just said that the product is misrepresented.

It says:
- Increased power over AixiZ acrylics
- 10mm FL

Neither is true. The FL is closer to 27mm IIRC (it's been a while since i measured it), and the power of my 6x blu ray, which does 189mW after an AixiZ acrylics, after this lens in parallel focus was around 61-64mW.

That's because of the low NA (numerical apperture - determines how much of the diode's output a lens can collect). The NA is determined by the lenses FL and the lenses effective diameter.

As the light exits the diode it diverges rapidly. If you want a higher power, you need a lens at the right distance from the diode, with a high enough effective diameter to collect as much of the light "cone" as possible. Ideally the NA of the lens should be the same as, or higher than the NA of the diode. That way the lens will collect all of the diode's output. It is then, that material and coatings come into play and can increase the power.

But when a lens is 27mm away from the diode it would need a huge effective diameter, to collect all or even most of the light. Since the lens is around 6.3mm diameter, it's effective diameter is around <5mm. At 27mm FL this means a VERY low NA, very little light collection. Sure, it passes the part of the light it collects better than other lenses, but it collects very little. Especially, if you consider the fact, that the fast axis of a 405nm diode spreads so fast, that it hits the inner threads of the AixiZ module, before it can even leave it. A good lens has to sit close enough to capture the light before it spreads over the lenses effective diameter.


There is one part of the description, that is true. The "round dot". Sometimes, when you want a diode laser with a round dot, you can use a lens with a lower NA. That will result in the edges of the fast axis of the diode output to be "clipped", and only the middle will get collimated. The result will be a round beam, but with some lost power. This is assuming, that the NA is low enough to clip some of the fast axis, but not low enough to clip the slow axis. That would be a NA of around 0.2 for a 405nm diode.. The beam would still not be perfectly round, but rounder, than we are used to.

But when a low diameter lens is 27mm away from the diode for parallel focus, or even if it was really 10mm, both the fast and the slow axis will get clipped resulting in a PERFECTLY round beam with a diameter of the lenses clear apperture, but with huge losses - that's why the beam is round, everything else is lost, and in this case, more than needed for a perfectly round dot is lost..

Because of that, it is not true, that this lens can increase the power. Sure, it could increase the power compared to an uncoated lens of the same FL and NA. But not compared to an AixiZ acrylics, which while it has far greater losses in material and reflections, at least collects most of the diode's output.


If you want to increase the power a little, you need either higher NA or better material + coating. If you want to increase the power a lot, you need higher NA and better material + coating.

When the diameter of the lens is limited (as is the case in our modules), the only way to get higher NA is by using a shorter FL.

This lens does have a higher transmittance than an AixiZ acrylics, but it can only produce a higher power beam, if that beam is passed to it with just the right divergence by another lens. Not by standing in front of a diode by itself.


So to sum it up. The product description is deceitful.

If the description would say "high transmittance material, x-y coating, low NA for a round beam", then it would not be a lie. But it says "higher power than AixiZ acrylics", which is not true. You can't have a clipped round beam and a higher power at the same time.

 

[lasersbee]

IgorT...
if I understand correctly... using this PHR803T lens.. I can get a rounder
dot but at less power because I' am picking off less of the available beam power
due to the fact that the lens is not large enough in diameter at its required focal length
to collect all of the available beam. :-?
But the lens is still usable to collimate the 405nm beam and create a rounder beam (dot)
but at less than optimal power.

Jerry  

 

[kernelpanic]

IgorT...
if I understand correctly... using this PHR803T lens.. I can get a rounder
dot but at less power because I' am picking off less of the available beam power
due to the fact that the lens is not large enough in diameter at its required focal length
to collect all of the available beam. :-?
But the lens is still usable to collimate the 405nm beam and create a rounder beam (dot)
but at less than optimal power.

Jerry  

Yes that is what he is saying (At WAY LESS than optimal power- 2/3 lost!)) And you will also get a larger dot as the focal lenth is so long... See the attached picture. It'll make perfect sense.

cheers,
kernelpanic

 

[IgorT]

Thanks for the drawing, kernelpanic... Now try to imagine this in a 3D system. This picture is actually quite correct if we say it shows the slow axis of the diode. The fast axis diverges much faster, and partially misses even the effective diameter of the "normal" collimating lens (if that's AixiZ)..


LaserBee:
Yeah, you can get a rounder beam with the sled lens. In fact clipping the edges of the diode output, to get a rounder beam is common practice in some pointers, where a round spot is desired and power is not important. But normally, the idea is to clip the beam just enough, but not too much, so that you get a somewhat round spot, but still with as much power as possible.

For example the AixiZ lens has that retaining plate with a small circular hole in the middle. All that does is clip the completelly "flat" output of the 5mW diode (which puts out a thin stripe), so that somewhat of a "spot" would come out. That plate basically lowers the NA of the lens. But not by much, since the round opening is closer to the diode than the lens.

We open that hole up, or even rip the entire ring out, in order to get as much of the diode output collimated as possible, for higher power. But the AixiZ acrylics still has a relativelly low NA (0.3). Because of that, the unfocused spot looks round-ish, with a brighter somewhat oval middle. With lenses with a higher NA, the beam will look even flatter.


But you can get a perfectly round spot using an AixiZ lens too.

You can take that retaining plate out in one piece, turn it around and put it back in, so that the plate with the small hole is now closer to the lens. This will reduce the NA of the AixiZ lens even further, and you will get a rounder dot than usual, but wasting even more of the power than the AixiZ lens does by itself.

You could then play with the diameter of that hole, till you get it just right, and clip the fast axis, but not the slow axis. That would give you a clipped round beam, wasting only the minimum required to get a round spot.

The result would be a thin round beam of a lower power than without the plate, but the power would still be higher than using the sled lens alone.

 

[lasersbee]

Thanks for the detailed explanation IgorT... You confirmed what I thought
I knew...