Illumination optical device and virtual image display

1. An illumination optical device comprising:

a light source;

a light pipe consisting of a single light pipe configured to guide illumination light from said light source, the light pipe having an emitting surface, the emitting surface having:

(a) a light emitting surface height;

(b) a light emitting surface width;

a diffuser arranged on an emitting surface side of said light pipe; and

an illuminated object including an illuminated object surface facing the emitting surface and having:

(a) an illuminated object surface height in a direction corresponding to the light emitting surface height; and

(b) an illuminated object surface width in a direction corresponding to the light emitting surface width,

wherein: the light emitting surface height is set greater than the illuminated object surface height, and the light emitting surface width is set smaller than illuminated object surface width.

2. The illumination optical device according to claim 1 , wherein a space is provided between said diffuser and said illuminated object.

3. The illumination optical device according to claim 2 , wherein said illuminated object is a spatial light modulator.

4. A virtual image display comprising:

a light source;

a light pipe consisting of a single light pipe guiding illumination light from said light source, the light pipe having an emitting surface, the emitting surface having:

(a) a light emitting surface height; and

(b) a light emitting surface width;

a diffuser arranged on an emitting surface side of said light pipe; and

a spatial light modulator modulating the illumination light incident from said diffuser according to an image to produce image light, the spatial light modulator having:

(a) an illuminated spatial light modulator surface facing the emitting surface and having a spatial light modulator surface height in a direction corresponding to the light emitting surface height;

(b) and a spatial light modulator surface width in a direction corresponding to the light emitting surface width;

a collimating optical system converting the image light from said spatial light modulator into groups of parallel rays and emitting the groups of parallel rays; and

a light guide plate in which said groups of parallel rays enter and are propagated while repeatedly undergoing total internal reflection, wherein the light emitting surface height is set greater than the spatial light modulator surface height, and the light emitting surface width is set smaller than the spatial light modulator surface width.

5. The virtual image display according to claim 4 , wherein a space is provided between said diffuser and said spatial light modulator.

6. The virtual image display according to claim 5 , wherein said light guide plate includes:

a first reflective volume holographic grating arranged on one end thereof, the end being opposite to said collimating optical system; and

a second reflective volume holographic grating arranged on the other end thereof, the end being opposite to a pupil of a viewer.

7. The virtual image display according to claim 4 , wherein said spatial light modulator is a transmissive liquid crystal panel.

8. The illumination optical device according to claim 1 , wherein the light pipe is configured so that the cross-sectional area thereof increases from a light incident surface adjacent to the light source toward the emitting surface.

9. The illumination optical device according to claim 1 , wherein the diffuser is configured to diffuse the incident rays so as to spread from the center of the incident rays to exhibit a Gaussian distribution, and is configured to adjust an exit angle and numerical aperture based on an incident light distribution.

10. The illumination optical device according to claim 1 , wherein the diffuser is the same in size and shape as the emitting surface of the light pipe.

11. The illumination optical device according to claim 1 , wherein the diffuser and illuminated object are configured and arranged such that a surface of the diffuser is coplanar with the illuminated object surface.

12. The virtual image display according to claim 5 , wherein each group of the parallel rays have a different angle of view.

13. The virtual image display according to claim 6 , wherein the first and second reflective volume holographic gratings have uniform interference fringes over entire hologram surfaces thereof.