System and method for telecentric projection lenses

Abstract

A projection lens system which includes a telecentric lens assembly. The lens may be used to form an image from a light source, including for example a resonant microcavity phosphor or cathode ray tube, onto a screen or display, such as in a television or a projection device. In accordance with one embodiment, a planar cooling gap or cavity (which may or may not contain a cooling liquid) is included between the imaging surface and the matching planar surface of the field lens. The use of a planar gap alleviates any temperature differentials across the cooling liquid and the lens surfaces, as compared with alternate designs that may have a non-planar gap between the faceplate and the field lens, or that use liquid lenses.

1 . A system for projecting an image, comprising: 
 a cathode ray tube comprising a resonant microcavity phosphor and a faceplate, and that produces light for an image; and    a lens assembly for projecting the image, comprising 
 a plano-convex field lens element positioned close to the faceplate, and  
 a set of positively powered lens elements positioned further from the faceplate.  
   
   
   
       2 . The system of  claim 1 , wherein the lens assembly further comprises a negatively-powered lens element adapted to locate the image as a final image on a screen.  
   
   
       3 . The system of  claim 1 , wherein the field lens includes a planar surface optically coupled to the faceplate.  
   
   
       4 . The system of  claim 1 , wherein the lens assembly includes a gap between the faceplate and the planar surface of the field lens.  
   
   
       5 . The system of  claim 1 , further comprising: 
 multiple cathode ray tubes, wherein each cathode ray tube is capable of producing light of a particular color for use in creating an image; and    a separate lens assembly for each of the multiple cathode ray tubes, for projecting the light from that cathode ray tube to create the image.    
   
   
       6 . The system of  claim 1 , wherein the cathode ray tube is a resonant microcavity phospor device.  
   
   
       7 . The system of  claim 4 , wherein the gap between the faceplate and the field lens includes a cooling fluid.  
   
   
       8 . A method of projecting an image, comprising: 
 generating light for an image using a cathode ray tube comprising a resonant microcavity phosphor and a faceplate; and    projecting the image using a lens assembly that comprises 
 a plano-convex field lens element positioned close to the faceplate, and  
 a set of positively powered lens elements positioned further from the faceplate.  
   
   
   
       9 . The method of  claim 8 , wherein the lens assembly further comprises a negatively-powered lens element adapted to locate the image as a final image on a screen.  
   
   
       10 . The method of  claim 8 , wherein the field lens includes a planar surface optically coupled to the faceplate.  
   
   
       11 . The method of  claim 8 , wherein the lens assembly includes a gap between the faceplate and the planar surface of the field lens.  
   
   
       12 . The method of  claim 8 , wherein the step of generating light includes generating light using multiple cathode ray tubes, wherein each cathode ray tube is capable of producing light of a particular color for use in creating an image; and wherein the step of projecting the image includes using a separate lens assembly for each of the multiple cathode ray tubes, for projecting the light from that cathode ray tube to create the image.  
   
   
       13 . The method of  claim 8 , wherein the cathode ray tube is a resonant microcavity phospor device.  
   
   
       14 . The method of  claim 13 , wherein the gap between the faceplate and the field lens includes a cooling fluid.  
   
   
       15 . A system for projecting an image, comprising: 
 a plurality of cathode ray tubes, wherein each of said plurality of cathode ray tubes comprises a resonant microcavity phosphor and a faceplate, and is capable of producing light of a particular color for use in creating an image; and    a plurality of lens assemblies, including a separate lens assembly for each of the multiple cathode ray tubes, for projecting the light from that cathode ray tube to create the image, wherein    each lens assembly further comprises 
 a plano-convex field lens element positioned close to the faceplate, and  
 a set of positively powered lens elements positioned further from the faceplate.