Image projection system

Abstract

An image projector is provided with a light valve having an upstream side and an downstream side. A light source is disposed on the upstream side of the light valve, and a front lens system with an entrance pupil is disposed on the downstream side of the light valve. A back optical system is disposed between the light source and the light valve. The back optical system has a nonimaging device with an exit aperture that is either imaged into the entrance pupil of the front lens system (Kohler) or imaged onto the light valve (Abbe).

What is claimed is:  
     
       1. An image projector optical system comprising: 
       a light source;  
       a nonimaging device defined by a edge ray method positioned downstream of the light source;  
       a light valve positioned downstream of the nonimaging device;  
       a front lens system positioned downstream of the light valve;  
       wherein light from the light source is projectable through the nonimaging device onto the light valve.  
     
     
       2. The projector of  claim 1 , further comprising a light pipe positioned between the light source and the nonimaging device, the light from the light source being transmittable through the light pipe to the nonimaging device. 
     
     
       3. The projector of  claim 1 , wherein the light valve is a digitally-driven reflective light valve. 
     
     
       4. The projector of  claim 1 , wherein the light valve is a digitally-driven transmissive light valve. 
     
     
       5. An image projector comprising: 
       a light valve having an upstream side and a downstream side;  
       a light source disposed on the upstream side of the light valve;  
       a front lens system disposed on the downstream side of the light valve, the front lens system having an entrance pupil and;  
       a back optical system disposed between the light source and the light valve, the back optical system having a nonimaging device with an exit aperture, the exit aperture being imaged onto at least one of the light valve and the entrance pupil of the front lens system.  
     
     
       6. The projector of  claim 5 , wherein the back optical system includes a light pipe. 
     
     
       7. The projector of  claim 6 , wherein the light pipe has a high numerical aperture >0.50. 
     
     
       8. The projector of  claim 6 , wherein the light pipe has an elongate, curved sheape. 
     
     
       9. The projector of  claim 5 , wherein the back optical system includes a first curved mirror that focuses light from the light source, the curved mirror having a numerical aperture >0.50. 
     
     
       10. The projector of  claim 5 , wherein the nonimaging device comprises a light expander. 
     
     
       11. The projector of  claim 10 , wherein the light expander has a conical shape with small and large diameter ends, and the large diameter end is disposed downstream of the small diameter end. 
     
     
       12. The projector of  claim 5 , wherein the light valve is a digitally-driven light valve. 
     
     
       13. The projector of  claim 5 , wherein the light valve is a reflective light valve. 
     
     
       14. The projector of  claim 13 , wherein the back optical system includes a color wheel. 
     
     
       15. The projector of  claim 5 , wherein the light valve is a transmissive light valve. 
     
     
       16. The projector of  claim 5 , wherein a second mirror images the exit aperture into the entrance pupil. 
     
     
       17. The projector of  claim 5 , wherein the light valve serves as an aperture stop. 
     
     
       18. The projector of  claim 5 , wherein the exit aperture of the nonimaging device serves as an aperture stop. 
     
     
       19. The projector of  claim 18 , wherein the exit aperture is rectangular. 
     
     
       20. An image projector, comprising: 
       
         a back optical system which includes a source of illumination and from which light propagates along an optical path;  
       
       
         a front optical system including a projection lens; and  
       
       
         a curved mirror and a light valve of a light reflecting type optically communicating with the back and front optical systems and partly defining the optical path, the curved mirror and the light valve optically associated with each other and optically interacting with the front optical system such that the curved mirror is positioned to receive and direct the light propagating from the back optical system to strike as incident light on the light valve and the light valve is positioned to reflect toward the projection lens the incident light striking the light valve. 
       
     
     
       21. The image projector of  claim 20 , in which the light valve includes a reflective digitally driven micro- mirror device.   
     
     
       22. The image projector of  claim 20 , in which the front optical system has an optical axis and the curved mirror has a surface normal that is inclined at a predetermined angle with respect to the optical axis, the predetermined angle establishing a direction of the optical path that causes the light propagating from the back optical system to strike as incident light on the light valve. 
     
     
       23. An image projector, comprising: 
       
         a back optical system which includes a source of illumination and from which light propagates along an optical path;  
       
       
         a front optical system including a projection lens;  
       
       
         a curved mirror and a light valve optically communicating with the back and front optical systems and partly defining the optical path, the curved mirror and the light valve optically associated with each other and optically interacting with the front optical system such that the curved mirror is positioned to receive and direct the light propagating from the back optical system to strike as incident light on the light valve and the light valve is positioned to direct toward the projection lens the incident light striking the light valve; and  
       
       
         a light pipe positioned and operable to transmit the light propagating along the light path between the back optical system and the curved mirror. 
       
     
     
       24. An image projector, comprising: 
       
         a back optical system which includes a source of illumination and from which light propagates along an optical path;  
       
       
         a front optical system including a projection lens; and  
       
       
         a curved mirror formed in the shape of a spherical segment and a light valve optically communicating with the back and front optical systems and partly defining the optical path, the curved mirror and the light valve optically associated with each other and optically interacting with the front optical system such that the curved mirror is positioned to receive and direct the light propagating from the back optical system to strike as incident light on the light valve and the light valve is positioned to direct toward the projection lens the incident light striking the light valve. 
       
     
     
       25. The image projector of  claim 23 , in which the light valve is of a light reflecting type and reflects the incident light toward the projection lens. 
     
     
       26. The image projector of  claim 25 , in which the light valve includes a reflective digitally driven micro- mirror device.   
     
     
       27. The image projector of  claim 24 , in which the light valve is of a light reflecting type and reflects the incident light toward the projection lens. 
     
     
       28. The image projector of  claim 27 , in which the light valve includes a reflective digitally driven micro- mirror device.