Can anyone help me by explaining the purpose of the first lens before the first mirror I have highlighted in the picture below? I’m wondering if it is essential as I see some lasers don’t have it, and I was wondering if it’s purpose is just to reflect the guide light towards M1. If it is not essential can it interfere with the laser in anyway?
I can see a red glow on that combiner lens and behind it so surely there is a red laser element pointing at it somewhere… You can block that and verify the red dot at your laser head disappears when you cover the output of the red laser pointer element.