I was hoping that someone would be willing to offer any insight or guidance they have on a project that I am working on. We are trying to use a lens mounted on a headlamp to focus a plain white light to as small of a point as possible at about 2ft away. We are not able to use a laser light because of safety issues. We tried using a single convex lens but we were not able to focus the light enough.
Our current thought is to use a fresnel lens. These is our issue: The lens needs to be very close to the light (no more than half an inch). We've been playing around with a cheap reading magnifier to focus the light, but we have to move the light a foot away to focus the light.
Our question is that would we be able to stack multiple fresnel lenses together to achieve the focus length we need (we've determined that's roughly 300mm focal length) at a close distance to the light. Single fresnel lenses with around a 300mm focal length seem to have two problems:
- They are very large (we would need a lens that is not much more than a few inches length and width to fit on a headlamp)
- They are very expensive