why are there so many different laser lenses?

[reloader45]

hello,

My 470 nm Project died.
I am unable to Open the Chinese Module.
It is glued or pressed.

Best regards

Edgar

 

[hondaman900]

Consider using beam correction optics.

What's the best source/resource for beam correction optics for a 405 nm laser? I'm having difficulty finding anything with a focal length more than 3-4 cm and need 13 cm.