How to design a fresnel lens and can any one gimme a practical design example?

The fresnel lens, to be designed is to use in automobile lighting applications and for PDA displays. I need some nice books/websites/references for the design process. An example for calculating the facet angle, valley and peak values, relief angles and values would be nice.

How to design a fresnel lens and can any one gimme a practical design example?
A Fresnel lens basically approximates the curvature of a spherical lens in small coaxial segments; the result being the same as if you cut a plano-convex or plano-concave lens into such segments and then cut off a hollow cylinder of material from each segment such that what remains is, roughly, the curved top, a newly-cut flat bottom, and one vertical side (i.e., a near-triangular cross section). Obviously some material needs to be left to hold all these segments together, so there will be a small fourth side, i.e. a constant added thickness. The 'curved' top may actually be flattened for easier manufacture. Some old lighthouses use concentric circular 3-sided prisms, a real approximation. I'd guess that segment size, valley and peak values depend on the material's mechanical properties more than optics.
Reply:this site has places that you can purchace them