How to obtain beam spread angle of a parabolic reflector?

[czh133]

Hi i am new to the forum and hopefully i can get some help.

I am trying to design a small parabolic light reflector that can be used with an LED array as being the source of light. The diameter of the LED array is 18.75mm. I am trying to obtain equations that would relate the diameter and height of the reflector with the beam spread angle. This way i can change the dimensions of the reflector to affect the angle i want to achieve. As an example i want to achieve a total of 70 degrees beam spread with the source being 18.75mm and placed on the focus point of the reflector. How can i find the diameter and height of the reflector with this information? any help is appreciated. thanks

 

[Andy Resnick]

Nonimaging optics is practically it's own branch of science, essentially disconnected from everything else.

http://en.wikipedia.org/wiki/Nonimaging_optics

This book (http://books.google.com/books?id=ykk1xQc25c0C&dq=Anidolic&source=gbs_navlinks_s) seems to be the primary resource in the field.

You may find some useful information here:
http://reflector-design.com/files/Computer_Aided_Optical_Design_Kusch_Oleg.pdf

It sounds like what you are asking relates to the design of searchlights, so look around for work based on the Mangin-Chikolev equation. Good luck...