Illumination apparatus, projector, and illumination method

1. An illumination apparatus comprising:

a first light source section disposed on an illumination optical axis;

a plurality of second light source sections disposed in positions away from the illumination optical axis; and

an optical axis conversion element having an entrance face and an exit face and having a plurality of reflective surfaces which allows a light incident from the first light source section to emit in such a way that an exiting optical axis of the light approximately coincides with the illumination optical axis, and allows lights incident from the plurality of second light source sections to emit in such a way that exiting optical axes of the lights become approximately parallel to the illumination optical axis in positions close to the illumination optical axis, wherein

light from each respective second light source sections corresponding to a respective individual reflecting surface of the plurality of reflecting surfaces converges on a respective individual reflecting surface, or in the vicinity thereof,

each reflective surface having an area substantially equal to a cross sectional area of the light from the respective second light source section at the reflective surface, such that a cross sectional area of light exiting each second light source is larger than both the cross sectional area of light from the respective second light source section at the reflective surface and the area of the respective reflective surface,

light from the first light source section converges within the optical axis conversion element between the entrance and exit faces, at a position slightly toward the entrance face side of the exit face, and

the exiting optical axes of the lights emitted from the plurality of second light source sections are each disposed a distance away from the illumination optical axis, and the distance is set to half of a diameter of a collected light spot in which the light intensity is reduced to around 5% to 20% of a peak intensity.

2. The illumination apparatus according to claim 1 , wherein

the light from the first light source section converges on the light exiting end of the optical axis conversion element, or in the vicinity thereof.

3. The illumination apparatus according to claim 1 , wherein

the optical axis conversion element reflects and emits the lights emitted from each of the plurality of second light source sections.

4. The illumination apparatus according to claim 3 , wherein

each of the individual reflective surfaces is tilted in such a way as to form a predetermined angle with the illumination optical axis; and

each of the lights emitted from the plurality of second light source sections is reflected by a corresponding individual reflecting surface among the plurality of reflecting surfaces.

5. The illumination apparatus according to claim 4 , wherein

the reflecting surfaces of the optical axis conversion element are surface reflecting surfaces which surface reflect the lights emitted from each of the plurality of second light source sections.

6. The illumination apparatus according to claim 5 , wherein

a dielectric multilayer is formed on the reflecting surfaces.

7. The illumination apparatus according to claim 4 , wherein

the reflecting surfaces of the optical axis conversion element are total reflecting surfaces which totally reflect the lights emitted from each of the plurality of second light source sections.

8. The illumination apparatus according to claim 1 , wherein

the optical axis conversion element refracts and emits the lights emitted from each of the plurality of second light source sections.

9. The illumination apparatus according to claim 1 , wherein

the optical axis conversion element has a pair of parallel planes approximately perpendicular to the illumination optical axis, and

the light emitted from the first light source section is transmitted through the parallel planes.

10. The illumination apparatus according to claim 1 , wherein

the optical axis conversion element has a hollow portion passing through in a direction in which the illumination optical axis extends, and

the light emitted from the first light source section is transmitted through the hollow portion.

11. The illumination apparatus according to claim 1 , wherein

a first light source section optical axis conversion element which bends the optical axis of the light emitted from the first light source section is provided on the light incident side of the optical axis conversion element.

12. The illumination apparatus according to claim 1 , wherein

a second light source section optical axis conversion element which bends the optical axis of the light emitted from at least one of the plurality of second light source sections is provided on the light incident side of the optical axis conversion element.

13. The illumination apparatus according to claim 1 , wherein

a heat dissipation member is provided on the optical axis conversion element.

14. The illumination apparatus according to claim 1 , wherein

the optical axis conversion element is housed in a casing having a light transmissivity.

15. A projector comprising: the illumination apparatus according to claim 1 ; an optical modulator which modulates light from the illumination apparatus; and a projection system which magnifies and projects the light modulated by the optical modulator.

16. The illumination apparatus according to claim 1 , wherein the illumination optical axis corresponds to a normal line that is perpendicular to a surface to be illuminated of an illumination object.

17. The illumination apparatus according to claim 16 , wherein the illumination object is a light valve.

18. An illumination method comprising:

providing an optical axis conversion element having an entrance face and an exit face and having a plurality of reflective surfaces; and

allowing a light emitted from a first light source section disposed on an illumination optical axis to emit toward an illumination object in such a way that an exiting optical axis of the light approximately coincides with the illumination optical axis, and lights emitted from a plurality of second light source sections disposed in positions away from the illumination optical axis to emit toward the illumination object in such a way that exiting optical axes of the lights become approximately parallel to the illumination optical axis in positions close to the illumination optical axis;

light from each respective second light source sections, corresponding to a respective individual reflecting surface of the plurality of reflecting surfaces, converging on a respective reflecting surface, or in the vicinities thereof, each reflective surface having an area substantially equal to a cross sectional area of the light from the respective second light source section at the reflective surface, such that a cross sectional area of light exiting each second light source is larger than both the cross sectional area of light from the respective second light source section at the reflective surface and the area of the respective reflective surface,

light from the first light source section converges within the optical axis conversion element between the entrance and exit faces, at a position slightly toward the entrance face side of the exit face, and

the exiting optical axes of the lights emitted from the plurality of second light source sections are each disposed a distance away from the illumination optical axis, and the distance is set to half of a diameter of a collected light spot in which the light intensity is reduced to around 5% to 20% of a peak intensity.