Is there a lens that takes all the incoming light and sends it out in one dirction
Many lenses and lens systems can be used to gather light over a wide area and focus it down to a smaller area. A fisheye camera lens, for example, gathers light from a full hemisphere and directs it into a circle smaller than the film frame so all of that is visible. A telescope gathers light from a narrow angle but over a wide area, focusing it down to increase brightness rather than to show more.If you really want all the output going "in one direction" rather than being resolved at a specific image plane or focal point, you're talking about collimation. Websearch on that term will find more info on that topic. You're not going to get perfect collimation unless you're using the incoming light to pump a laser... and even that tends to be less than perfect in practice, if I remember correctly.Websearching on "lenses" and "optics" will probably find some good introductory lessons on what lenses can and can't do.
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Do you know if I could set the lasers up in a line pointing straight down, and use 45 degree one way mirrors to send them all the same direction.
A cheap hack-it-yourself version could be to use a magnifying glass to focus light onto the end of a bunch of optical fibres from one of those swishy lamps.You may melt the fibres, though.
Essentially that's a variant on the old collimation tube idea, just "solid state".(And if you're worried about heat, glass fibers might be a better solution.)BTW, see also https://www.instructables.com/id/Home-Made-Collimator/. Or websearch that term for some other common solutions.
WHat for ? A solar concentrator ?
My plan was to take a few high power lasers, aim them all at the lens, and then transmit it through a fiber optic cable, then I would focus it to a small point for cutting.
That's notoriously difficult to do I'm afraid. I'd study "collimating optical systems" as a topic if I were you. The other kicker is that diode lasers aren't circular beams, but tend to being elliptical, complicating things further.
What exactly do you mean? Do you mean a thing that sends light in parallel, or a thing that focuses everything into one spot, or a thing that is a mirror for light coming from one side of it, and glass from the other side?