Light source device having a retardation plate and projection display apparatus including the light source

1. A light source device, comprising:

a first solid-state light source unit including:

a plurality of first solid-state light source elements disposed at a pitch “p,” configured to emit a first linearly-polarized light; and

a plurality of first lenses disposed on an emission side of the first solid-state light source elements, configured to cause the first linearly-polarized light to exit as a parallel light with a luminous flux width “d,” wherein a condition d>p/2 is satisfied;

a second solid-state light source unit including:

a plurality of second solid-state light source elements disposed at the pitch “p,” configured to emit a second linearly-polarized light orthogonal to the first linearly-polarized light; and

a plurality of second lenses disposed on an emission side of the second solid-state light source elements, configured to cause the second linearly-polarized light to exit as a parallel light with the luminous flux width “d,” wherein a condition d>p/2 is satisfied, the first linearly-polarized light exiting from the first lenses is orthogonal to the second linearly-polarized light exiting from the second lenses, and the second solid-state light source unit is disposed at a position displaced by p/2 relative to the first solid-state light source unit in a direction parallel to a polarization direction of the second linearly-polarized light;

a polarization combination mirror configured to combine polarized lights exiting from the first solid-state light source unit and the second solid-state light source unit so as to combine luminous fluxes of the polarized lights;

a first retardation plate configured to convert polarization states of the polarized lights coming from the polarization combination mirror;

a dichroic mirror configured to reflect and pass the polarized lights coming from the first solid-state light source unit and the second solid-state light source unit based on type of polarization;

a phosphor plate configured to be excited by polarized lights reflected by the dichroic mirror so as to emit fluorescence;

a second retardation plate configured to convert polarized lights passed from the dichroic mirror to a circularly-polarized light;

a reflecting plate configured to reflect the circularly-polarized light toward the second retardation plate, the circularly-polarized light having been converted by the second retardation plate; and

a third retardation plate having a strip shape disposed between the polarization combination mirror and the dichroic mirror, the third retardation plate being disposed at a position such that light having passed through the third retardation plate becomes a mixed light, the mixed light including both the first linearly-polarized light and the second linearly-polarized light.

2. The light source device according to claim 1 , wherein the first retardation plate is one of a half-wavelength plate and a quarter-wavelength plate.

3. The light source device according to claim 1 , wherein the second retardation plate is a quarter-wavelength plate.

4. The light source device according to claim 1 , wherein the third retardation plate is a half-wavelength plate.

5. The light source device according to claim 1 , wherein each of the first to third retardation plates is a thin-film retardation plate utilizing birefringence of a film formed with a dielectric material by oblique deposition.

6. The light source device according to claim 1 , wherein each of the first to third retardation plates is a fine-structure retardation plate utilizing birefringence achieved by a fine structure.

7. The light source device according to claim 1 , wherein each of the first to third retardation plates is made of quartz.

8. The light source device according to claim 1 , wherein the first retardation plate includes a rotation adjusting mechanism.

9. The light source device according to claim 1 , wherein the plurality of the solid-state light sources is blue-light semiconductor lasers.

10. The light source device according to claim 1 , wherein the lights exiting from the plurality of the solid-state light sources are linearly-polarized lights.

11. The light source device according to claim 1 , wherein the phosphor plate includes:

a rotation-controllable circular substrate, and

a phosphor layer of a cerium (Ce)-activated yttrium-aluminum-garnet (YAG) yellow phosphor, the layer being disposed on the substrate.

12. The projection display apparatus according to claim 1 , wherein both the first linearly-polarized light and the second linearly-polarized light are incident on the third retardation plate.

13. The projection display apparatus according to claim 1 , wherein both light emitted from the plurality of first solid-state light source elements and light emitted from the plurality of second solid-state light source elements are incident on the third retardation plate.

14. A projection display apparatus, comprising:

a light source device according to claim 1 ;

an illumination optical system for condensing light incident from the light source device so as to illuminate a to-be-illuminated region;

an image forming element for forming an image in accordance with an image signal; and

a projection lens for enlarging and projecting the image formed by the image forming element.

15. The projection display apparatus according to claim 14 , wherein the image forming element is a liquid crystal panel.

16. The projection display apparatus according to claim 14 , wherein the image forming element is a mirror-deflection-type digital micromirror device (DMD).