Directional diffuser

Abstract

A diffuser is disclosed which transmits or reflects incident light into a specific range of angles. In a preferred embodiment, this light is uniformly scattered throughout a cone of angles. The diffuser consists of two parts. The first part diffracts or reflects light into a specific offset angle. The second part, in the preferred embodiment, uniformly scatters the light through a range of angles, which is centered on the offset angle. The diffusers have utility in applications such as screens for wrist watches, computers, calculators, and cell phones.

1 - 15 . (canceled)  
   
   
       16 . A method for making a directional reflector having a reflective surface, wherein the reflective surface includes at least one periodic surface comprising a plurality of periodic surface pieces and wherein the period surface pieces are each described by a parabolic function and reflect an incident ray throughout a specified uniform cone of angles, comprising the steps of: 
 creating a gray scale mask;    transmitting recording light through the gray scale mask such that a desired parabolic function is displayed; and    recording the desired parabolic function in a layer of photoresist.    
   
   
       17 . The method for making a directional reflector having a reflective surface of  claim 16 , further comprising the step of coating a second periodic surface with the layer of photoresist prior to recording the desired parabolic function.  
   
   
       18 . The method for making a directional reflector having a reflective surface of  claim 17 , wherein the second periodic surface is wedge-shaped.  
   
   
       19 - 20 . (canceled)  
   
   
       21 . A method for making a directional reflector for reflecting an amount of incident light, the directional reflector having a reflective surface, wherein the reflective surface has a periodicity on the order of a wavelength of the incident light and wherein the reflective surface further includes a coarse periodicity having an asymmetrical blazed profile and a fine periodicity, comprising the steps of: 
 creating the coarse periodicity having an asymmetrical blazed profile by prism coupling and recording into a layer of photoresist using more than one beam, wherein each beam is separated by a small angle and wherein each beam is incident at a large oblique angle; and    creating the fine periodicity by reflecting a single beam from the layer of photoresist using prism coupling.    
   
   
       22 . The method for making a directional reflector having a reflective surface of  claim 21  further comprising the step of adding a diffuse component by having one beam be incident through the photoresist layer onto a predetermined diffuse reflector by means of prism coupling.  
   
   
       23 . A method for obtaining white light using a directional reflector having a reflective surface, wherein the reflective surface has a periodicity on the order of a wavelength of incident light and wherein the reflective surface further includes a coarse periodicity having an asymmetrical blazed profile and a fine periodicity, comprising the steps of: 
 creating the coarse periodicity having an asymmetrical blazed profile by prism coupling and recording into a layer of photoresist using more than one beam, wherein each beam is separated by a small angle and wherein each beam is incident at a large oblique angle;    creating the fine periodicity by reflecting a single beam from the layer of photoresist using prism coupling; and    recording the fine periodicity in adjacent narrow parallel stripes, wherein each stripe reflects a different color.    
   
   
       24 . A method for making a directional reflector having a reflective surface, the reflective surface comprising a first periodic surface component having a periodic wedge-shape, the periodic wedge-shape having a first period and a second periodic surface component, the second periodic surface component having a second period, wherein the combination of the first periodic surface component and the second periodic surface component cause an oblique light ray, which is incident on the reflective surface, to be reflected into a cone of rays, comprising the steps of: 
 mechanically ruling the wedge-shape;    creating a plastic replica from the mechanical ruling;    creating a random array of shallow parabolic depressions by spraying the plastic replica-with a fine droplet spray containing a plastic solvent.    
   
   
       25 . The method for making a directional reflector having a reflective surface of  claim 24 , further comprising the steps of: 
 creating a metal replica from the sprayed plastic replica;    creating a second plastic replica from the metal replica; and    spraying the second plastic replica with a fine droplet spray containing a plastic solvent.    
   
   
       26 . The method for making a directional reflector having a reflective surface of  claim 25  wherein the steps are repeated.