Which lens should I buy ?

[Externet]

Good day.
A chinese cheap and common 1500mW violet engraving laser 12mm module focuses to about 10 cm with its supplied lens adjusted all the way in... What lens can be installed instead to focus at ~10m, or beyond ? It is not for engraving.

 

[milantheone]

10m or beyond sounds like you want to focus to infiniy..
probably same lens can do the trick.. you have to move it out... find the sweet spot..

if you are not happy with the beam/dot of stock lens than consider G8 or 3element lens..

 

[Externet]

Thank you.
The current lens supplied with this cheap engraving laser focuses the beam dot to shorter distance when unscrewed out; from about 12cm all the way in to about 3 cm when out.
Does not provide a dot at any distance farther than 12cm when the lens is all the way in.
When the lens is screwed all the way in, the distance from the lens glass to the laser aperture inside is about 4mm, cannot get closer as the lens thread bottoms to the housing.
As a beginner, cannot discern the terminology of what is what, what does what when see G8, G2, collimating, focusing, M9P05-10, 3 element... Cannot decide by myself. I can identify wavelenghts, diode dimensions in the descriptions.
If your expertise can suggest which to buy from a common source -say ebay- with a better chance of sucess, please link. There will be no wrong feelings if fails. Am just playing and learning.
Would this behave ? ---> eBay item number:112395261851 (I cannot post a link yet as a novice here)

 

[milantheone]

it would be better if you stated what you want from the lens ..

i suppose you want a nice beam/dot... so i have to say G8 lens and 3element are your best choice for that..

find some threads about them here on the forum.. there is plenty.. but to summarize:

G8 is best overall.. nice small dot at the distance
3element - nice small dot at the distance but it will give you around 20percent lower output than G8 - basicaly it reduces output of the laser diode a bit.. it should not concern you as your diode is 1500mW so you will still get a lot of power..

if you are UK located here is some reputable seller:
https://odicforce.com/epages/05c54fb6-7778-4d36-adc0-0098b2af7c4e.mobile/en_GB/?ObjectID=35689393

if you prefer ebay there is lot of sellers but i used to buy from this one:
https://www.ebay.co.uk/itm/325048337623?hash=item4bae6404d7:g:Il8AAOSwOY5dlXYE

there is one issue with G8 lens though..
if you focus to infinity - for nice dot.. the lens screw to the module just barely. total opposite of what you have right now.. there are workarounds but for me it is not so user friendly as 3element.

so i would stick to 3 element.. this sits deep in the module and has nice tight dot, and 20 percent loss of brightness at high powers is not something to be worried about

https://www.ebay.co.uk/itm/323141958403?hash=item4b3cc2fb03:g:9lYAAOSwdTBaeos9

 

[paul1598419]

The G2 lens offered by DTR is also a good lens and will give you the greatest output power at infinity focus. You can find similar lenses on eBay for less money too. These have a focal length of ~2.39 mm, IIRC.