Light source device and projection display apparatus including plural light sources, and a lens condensing light from the plural light sources into one spot

Abstract

A first light source device includes: a solid-state light source; a condenser element that collects light from the solid-state light source; a retardation plate that converts linearly polarized light into circularly polarized light; and a reflection plate, wherein the retardation plate is disposed at a point of incidence of collected light and divergent light between the condenser element and the reflection plate. A second light source device includes: a solid-state light source; a retardation plate that changes a polarization direction of light from the solid-state light source to make a ratio of p-polarization and s-polarization components of the light constant under control; and a dichroic mirror that separates the light from the retardation plate according to the polarization direction, wherein the retardation plate is disposed at a point of incidence of one of collected light and divergent light between the solid-state light source and the dichroic mirror.

What is claimed is: 
     
         1 . A light source device comprising:
 a solid-state light source;   a condenser element that collects light transmitted through the solid-state light source;   a first retardation plate that changes a polarization direction of light from the solid-state light source to make a ratio of p-polarization and s-polarization components of the light constant under control;   a dichroic mirror that separates the light from the first retardation plate according to the polarization direction;   a second retardation plate that converts linearly polarized light into circularly polarized light; and   a reflection plate, wherein   the first retardation plate is disposed at a point of incidence of one of collected light and divergent light between the solid-state light source and the dichroic mirror, the collected light being collected at a single light collection spot, the divergent light diverging from a single light collection spot, and   the second retardation plate is disposed between the condenser element and the reflection plate.   
     
     
         2 . The light source device according to  claim 1 , wherein
 each of the first and the second retardation plates is a thin-film retardation plate that uses birefringence due to oblique vapor deposition and includes an inorganic material.   
     
     
         3 . The light source device according to  claim 1 , wherein
 each of the first and the second retardation plates is a microstructural retardation plate that uses birefringence due to a microstructure.   
     
     
         4 . A projection display apparatus comprising:
 the light source device according to  claim 1 ;   an illumination optical system that collects light from the light source device and illuminates a to-be-illuminated region with the light;   an image forming element that forms an image according to a video signal; and   a projection lens that magnifies and projects the image formed by the image forming element.   
     
     
         5 . The light source device according to  claim 1 , further comprising a collimating lens between the first retardation plate and the dichroic mirror, the collimating lens being configured to collimate light from the solid-state light source. 
     
     
         6 . The light source device according to  claim 5 , further comprising a first diffusion plate between the collimating lens and the dichroic mirror, the first diffusion plate being configured to diffuse the light collimated by the collimating lens. 
     
     
         7 . The light source device according to  claim 6 , wherein a width of the first retardation plate is less than a width of the first diffusion plate. 
     
     
         8 . The light source device according to  claim 1 , further comprising a second diffusion plate between the condenser element and the second retardation plate, the second diffusion plate being configured to diffuse the light collected by the condenser element. 
     
     
         9 . The light source device according to  claim 8 , wherein a width of the second retardation plate is less than a width of the second diffusion plate. 
     
     
         10 . The light source device according to  claim 1 , further comprising a mirror configured to reflect light from the solid-state light source toward the first retardation plate. 
     
     
         11 . The light source device according to  claim 10 , wherein the mirror is configured such that the reflected light focuses between the mirror and the first retardation plate. 
     
     
         12 . The light source device according to  claim 1 , wherein the second retardation plate converts linearly polarized light which is transmitted through the dichroic mirror into circularity polarized light. 
     
     
         13 . The light source device according to  claim 1 , wherein the second retardation plate is disposed between the dichroic mirror and the reflection plate. 
     
     
         14 . The light source device according to  claim 1 , wherein the dichroic mirror reflects light which is reflected by the reflect plate. 
     
     
         15 . The light source device according to  claim 1 , further comprising a lens element that is located between the first retardation plate and the dichroic mirror, wherein
 light collimated by the lens element incidents the dichroic mirror.   
     
     
         16 . The light source device according to  claim 15 , further comprising a diffuser that is disposed between the lens element and the dichroic mirror. 
     
     
         17 . The light source device according to  claim 1 , further comprising a phosphor plate, wherein
 the dichroic mirror separates the light into first light and second light, and   the phosphor plate converts the first light.   
     
     
         18 . The light source device according to  claim 17 , wherein
 the solid-state light source emits blue light, and   the phosphor plate converts the blue light into yellow light.