Quick Question about Lasers and Lenses

[Marseyus]

Ok for some reason I've read way too much on the subject and have one simple question. All the other web sites i go to complicate the heck out of it and all i really want to know is,

What type of lens do i need to focus a beam of light from a flashlight into a laser points type beam. In other words i want to know which lens will focus light into a beam?

 

[MikeMl]

See "positive (converging) lens" on this page

 

[vne147]

You'd need a combination of a convex and concave lenses. The width of the resultant beam would depend on the angle of incident light, the focal lenghts of the lenses, and how far apart they were placed. The system would work best if you collimated the incident light with a biconvex lense first. The other websites you've looked at complicated the heck out of it because it is not a trivial problem. Sorry. FYI, if you were able to collimate the light (i.e. get all light exiting your focusing system to travel in parallel paths) it still wouldn't technically be a laser becasue it wouldn't be coherent. The best thing you can do other than taking a course in optics is to get a concave and convex lense and play with them by placing them different distance apart. It won't be perfect but it might be good enough depending on what your purpose is.