Lightobject.com Support Forum

Hello,

So, after reading this forum post, I went ahead and purchased a GaAs lens.
I am disappointed.

I've done a side by side comparison between GaAS http://www.ebay.com/itm/HQ-GaAs-Focus-L ... 0738475365
and HQ ZnSe http://www.lightobject.com/High-quality ... -P669.aspx

I found that the GaAs has an inferior transmission rate.
GaAs allows approximately 57% transmission rate, this is similar to the transmission rates of the OEM ZnSe lenses that come with cheap machines.
The HQ ZnSe transmits 82%.

The GaAs lens required an 85% power level to achieve the same results as the HQ ZnSe at 60% power.

I have been cutting Acrylic with various Chinese 40W machines for years and have never come across a better lens at an affordable price than the Lightobject HQ ZnSe.

Has anyone else done any side by side comparisons?

Hi there
I dont know where you take your data from,but something is off at your comparison.
I use this GaAs lenses since more then a year and in the mean time many others and we have completly different results to you.
the required power level with the GaAs lens to cut any kind of material is only 60 to 70 % of the power level with the Hq ZnSe lens.
this comparisson are made in real praxis cutting not theoretical!
I have cut 30 sets of railroad model houses out of 1/8 regular HD plywood and lots of engraving and cleaned the lense many many
times with just a eyglass whipe and still have no scratches, try this with any Znse lens and you are out of luck.
maybe something to add the beam has to be exactly centered on all mirrors and four corner.
hey nothing against marcos price thats a great price but this was not about price.
greetings
waltfl

salahaddam wrote:Hello,

So, after reading this forum post, I went ahead and purchased a GaAs lens.
I am disappointed.

I've done a side by side comparison between GaAS http://www.ebay.com/itm/HQ-GaAs-Focus-L ... 0738475365
and HQ ZnSe http://www.lightobject.com/High-quality ... -P669.aspx

I found that the GaAs has an inferior transmission rate.
GaAs allows approximately 57% transmission rate, this is similar to the transmission rates of the OEM ZnSe lenses that come with cheap machines.
The HQ ZnSe transmits 82%.

The GaAs lens required an 85% power level to achieve the same results as the HQ ZnSe at 60% power.

I have been cutting Acrylic with various Chinese 40W machines for years and have never come across a better lens at an affordable price than the Lightobject HQ ZnSe.

Has anyone else done any side by side comparisons?

~I've also found that the GaAs lenses are a great improvement over the stock lenses that come with these machines. I've not tried better quality ZnSe though. I can now cut 2mm mdf at 68% power (18ma) and 14 speed, whereas before it struggled to do it at 7mm/s.

Folks, there are different 'grade' on ZnSe and the GaAs lens. The stock one or someone selling on eBay we called "China made" which means that both materials and processing are done in China. The "High quality" one I'm carrying is "imported materials", polish and coating in China. That make the difference. Of course, there are even better which is 100% made in USA or Israel but the price is more than double of the optics I'm selling.

Now my question to "salahaddam": Did you buy the GaAs lens from me or from someone else?


Marco

Here is the exact item I purchased http://www.ebay.com/itm/HQ-GaAs-Focus-L ... 0738475365

And I compared it to the HQ ZnSe I use everyday and which I purchased from Lightobject 1 1/2 years ago.

I came to my results through a practical side by side comparison.
I have been cutting Acrylic for many years and using a variety of mirrors and lenses.

The GaAs lens which I mentioned appears to be of high quality and it is comparable in price to the HQ ZnSe.
But it will not cut the exact same material with the exact same machine without raising the power output significantly.

The benefit of GaAs seems to be durability, but it is worse at transmitting.
Check out the science behind this.

http://www.americanphotonics.com/znse.php
http://www.americanphotonics.com/gaas.php

Hi there
did you know that the GaAs lense has two sides??? one side up is better for engraving and the other for cutting.
in my case its the concave side up what let me cut up to 6mm oak wood with 43% power and 6mm/sec speed just as a sample
and I can cut acrylic 6mm with 38%power and 6 to 8mm/sec speed.
like I said the price was not the importance more importand is the cutting capability and the scratch resistenc.
the GaAs lenses are used mainly in high power comercial and industrial machines what do you think why?
greetings
waltfl

salahaddam wrote:Here is the exact item I purchased http://www.ebay.com/itm/HQ-GaAs-Focus-L ... 0738475365

And I compared it to the HQ ZnSe I use everyday and which I purchased from Lightobject 1 1/2 years ago.

I came to my results through a practical side by side comparison.
I have been cutting Acrylic for many years and using a variety of mirrors and lenses.

The GaAs lens which I mentioned appears to be of high quality and it is comparable in price to the HQ ZnSe.
But it will not cut the exact same material with the exact same machine without raising the power output significantly.

The benefit of GaAs seems to be durability, but it is worse at transmitting.
Check out the science behind this.

http://www.americanphotonics.com/znse.php
http://www.americanphotonics.com/gaas.php

I believe you may have adjusted something else when you changed your lens.

I have been testing them under the exact same circumstances and find the GaAs to transmit roughly 25% less power.
Maybe someone else will try this and report what they find.

I was not trying to compare prices, but only point out that they are about the same.

There are three reasons large machines are outfitted with GaAs.
GaAs is usually cheaper than ZnSe.
They are purposefully overpowered and don't require full power transmission.
And they are operated in dirty environments and are likely to be handled / mis-handled by their operators, the GaAs being less prone to dirt / dust / handling scratches.

As far as lens sides, using your lens with convex side up is always preferred, cutting or engraving.



Here's how these lenses actually work:
http://folk.uio.no/walmann/Publications ... node8.html
http://eksmaoptics.com/optical-componen ... ex-lenses/

Light entering the convex side will always create a smaller focus point and therefore more focused power.
Flipping the lens gives a broader, 4 times less focused point and therefore reduced power

The only benefit to flipping your lens would be to lose some focus and blur the beam and lose power for possible smoother engraving.
(Basically un-focusing your beam, which can be done many ways including raising or lowering your material or laser head)

The science behind the materials used to create these lenses is very clear
http://www.americanphotonics.com/znse.php
http://www.americanphotonics.com/gaas.php

When equally formed and polished ZnSe will always transmit more light in the .5 to 14 um range.
Co2 lasers like ours are 10 um.