What are G2, G3... Lenses

[Tuxifix]

Hi fellow laser enthusiasts,

stupid, quick question: what is a G2, G3... lens?
I read that G2 is a single lens, G3 is a combination of three lenses and so on. However, I cannot find a definition of the different kinds of lenses (probably because the search does not allow to use two-digit keywords and I do not know what else to search for). I just do not know what Gx stands for. Does someone have a definition?

Best regards,
Tuxifix

 

[RedCowboy]

They are both single element aspheric lenses available through DTR for our common visible wavelength laser diodes, they are respectively short and long focal length for the modules that take the standard M9 * 0.5 threaded lens barrels, example the 12mm diode modules and others.

There is also a 3-element lens but it is denoted as 3E or 3-element and is not the same as the "G" series lenses which simply stands for " GLASS " IINM as there are acrylic single elements and so far the G lenses are single element, G2, G3, G7, G9 the G7 is basically a G3 but not as handy IMHO and the G9 is a repurposed lens very similar to the G2 and not really available although I have a few. Sanwu also sells a G2 and there are Chinese copies of the G2, the G2 is the shorter FL lens that lets the most power through but being shorter in FL will make a wider spot at distance far field than the 3E or G3/G7

 

[paul1598419]

Yes, these are denotations first given to these lenses by DTR for the G2 and G3. The G2 has an EFL of 2.39 mm and the G3 has an EFL of 8 mm. While it is true that the longer focal length lenses will give you less divergence in the far field, for engraving the short FL lens is what you want. There was also a G1 that was around years ago, but haven't seen one for sale in awhile. But, if you look at professional lenses made for lasers you will never see a designation like G and a number. Many of the short focal length aspheric lenses are AR coated for 405nm to 450nm. If you want one AR coated for a different wavelength you will need to search for one. The acrlyic lenses are fine for lasers doing 400 mW or less, but for higher power lasers you always need a glass lens. The acrylic ones will melt.

 

[Lifetime17]

Hi Tuxifit,
Red Cowboy summed it up very well and to the point, he is on spot with laser optics and very well informative on the subject.

Rich

 

[Tuxifix]

Ahh, I see! I was not aware these are just names given by DTR. Thank you all a lot for the explanation.

 

[GSS]

Just to add the G3 lens seemed to surface quite recently but it's in the family of single lens like G2 and G7's
As far as I seen the G7's seem to be only on Sanwu's sight. but could be on ebay now.
The 3 lens combination is called a 3 element or 3E. You will notice they come in a dark barrel and the G2's etc. are usually in a brass barrel.

 

[RedCowboy]

LOL Rich, Thanks for the vote of confidence friend, but honestly what I don't know about optics could fill a book, however I have learned a lot and I hope to learn a great deal more.

 

[Lifetime17]

Hi Red,
Dont cut yourself to short you have the gift in optics really. I don't worry about what you don't know it's what you know that counts.

Rich

 

[Benm]

It's all a bit confusing really. I reckon the G just stands for glass, which is good since they will not melt at high power.

But there are other factors, like the anti-reflective coating on these lenses, which can be optimized for a particular wavelength. The optimal wavelength of the coating really depends on wavelength a lot, and those optimized for red could actually be quite bad for blue.

Then again, if you buy all of your stuff from a vendor that has detailed knowledge you should be able to get advise on what lens to use with what diode.

 

[RedCowboy]

It's all a bit confusing really. I reckon the G just stands for glass, which is good since they will not melt at high power.

But there are other factors, like the anti-reflective coating on these lenses, which can be optimized for a particular wavelength. The optimal wavelength of the coating really depends on wavelength a lot, and those optimized for red could actually be quite bad for blue.

Then again, if you buy all of your stuff from a vendor that has detailed knowledge you should be able to get advise on what lens to use with what diode.

Yes, I did mention that G is for Glass and the G2, G3, G7 are all suitable for red, green and blue laser diodes, only the G9 which is repurposed from DLP projectors may not work well on other than 445-470nm range diodes, but they are not really all that available and the unit they came from is out of production, so the G2, G3, and G7 which are currently available are wideband coated for visible and can be used for all visible wavelengths, no need for confusion.

 

[Dhodge77]

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Which of these is the best to use in an RGB projector set up. Im in the process of acquiring parts and planning to take on the challenge of building my first laser show projector. I was thinking G-8 or G7 but now these posts have me thinkin G-3. Ive seen a couple advertised G9's on Ebay but i also noticed they have them labeled as 3 element 3 glass lenses so they must be chinese or an attempt to take over the name. Idk if anyone noticed in my naming of the lenses in this post where i hyphenated in the lens names that are DTR official. You will notice that any G lenses by DTR will always be labeled G-2, G-3, G-8.

 

[Dhodge77]

Im using an 1.6W Osram PLTB450B for blue, a recapped 1W Nichia NUGM03T from LaserTree, and a 1.2W Ushio HL63283HD. Does anyone think those diodes will balance in power? I could probably dial back with the green a little. Also i should probably use several single mode reds to keep up with the green and blue instead of the terrible diverging red but im going to attempt to align this high powered red. Any advice on the best lense set up or alignment suggestions to align these three beams together?