Dear Friends.
I try to concentrated light by fresnel lens using solar simulator (halogen lamp). But i can't get a focus point. Anybody have experience to concentrated light using simulator?
Thanks,
Dear friend...Fresnel lenses make poorer quality images because of a problem called spherical aberration: light rays which travels through a Fresnel lens at different angles will come to a focus at slightly different points, giving a blurred image.Hence You get a bit of distortion because the surface of a Fresnel lens is discontinuous. You'll probably also find that different colors are refracted by the lens to different degrees, giving you unwanted color fringes in your image (a problem called chromatic aberration). Although it's possible to adjust the angle of the steps in a Fresnel lens to minimize aberrations, generally you'd use a conventional lens (optical quality glass) for higher optical performance.
I hope this may prove a bit useful for your work.
Dear Idris,
Mayank is totally right about spherical and chromatic aberrations.
To say it in an other way, Fresnel lens will focus rays that are parallel before reaching the lens. If you use a ponctual source that is at a finite distance from the lens, then incoming rays are not parallel to each other, which lead to a bad quality of concentration.
Moreover, halogen is a polychromatic source, and as Mayank already said, each wavelength will focus at a different focal length, leading to chromatic aberration.
Regards,
Dear Idris,
You can but you need to collimate the incident angle of the rays that fall on the Fresnel lens surface for the main reasons our friends indicate above, anyway, the chromatic aberration is not your main problem unless you want to concentrate the light more than 1000x or similar.
It is simple and may be cheap, depends on how big is your Fresnel lens, to collimate the light from the halogen lamp. You only need a parabolic mirror and the lamp on the focal plane of the parabola. After the reflection, the rays will be collimated and you can send them to the Fresnel lens to concentrate the light. The concentration reached is going to depends on your set-up, power of the light, quality of the mirror, sizes...
Regards,
Eduardo
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