Image projection apparatus

Abstract

A projector has a projection optical system unit, which has a positively powered optical system and a curved-mirror optical system. In the projector, a first curved mirror and a second curved mirror of the curved-mirror optical system are so arranged that the optical path that the base ray travels to reach the first curved mirror crosses the optical path that the base ray travels to leave the second curved mirror. Moreover, the second curved mirror has a negative optical power.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic optical cross-sectional view of a projector (Example 1);

FIG. 2 is a schematic optical cross-sectional view showing, mainly, the projection optical system unit included in the projector shown in FIG. 1;

FIG. 3 is a schematic perspective view of the projector of Example 1;

FIG. 4 is a spot diagram obtained with the projector of Example 1;

FIG. 5 is a distortion diagram obtained with the projector of Example 1;

FIG. 6 is a diagram illustrating θ1 to θ3 in the projector of Example 1;

FIG. 7 is a schematic optical cross-sectional view of another projector (Example 2);

FIG. 8 is a schematic optical cross-sectional view showing, mainly, the projection optical system unit included in the projector shown in FIG. 7;

FIG. 9 is a schematic perspective view of the projector of Example 2;

FIG. 10 is a spot diagram obtained with the projector of Example 2;

FIG. 11 is a distortion diagram obtained with the projector of Example 2;

FIG. 12 is a diagram illustrating θ1 to θ3 in the projector of Example 2;

FIG. 13 is a perspective view of a global coordinate system; and

FIG. 14 is a schematic perspective view of a projector provided with an optical path changing element.

Claims

1. An image projection apparatus comprising: a projection optical system unit that guides image light emitted from a light modulation element so as to project the image light onto a projection surface,wherein the projection optical system unit includes: a positively powered optical system that has an optical aperture and that has a positive optical power; anda curved-mirror optical system that has at least a first curved mirror and a second curved mirror, the second curved mirror reflecting light reflected from the first curved mirror,wherein the first and second curved mirrors are so located that, let a ray of the image light that travels from a center of a display surface of the light modulation element through a center of the optical aperture toward a center of the projection surface be called a base ray,an optical path that the base ray travels to reach the first curved mirror crosses an optical path that the base ray travels to leave the second curved mirror, andwherein the second curved mirror has a convex reflective surface.

2. The image projection apparatus of claim 1, wherein conditional formula (1) below is fulfilled: 15<θ1<45  (1)

3. The image projection apparatus of claim 2, wherein conditional formula (1a) below is fulfilled: 20<θ1<35  (1a)

4. The image projection apparatus of claim 1, wherein conditional formula (2) below is fulfilled: 30<θ2<60  (2)

5. The image projection apparatus of claim 4, wherein conditional formula (2a) below is fulfilled: 35<θ2<55  (2a)

6. The image projection apparatus of claim 4, wherein conditional formula (1) below is fulfilled: 15<θ1<45  (1)

7. The image projection apparatus of claim 1, wherein the projection surface is arranged substantially parallel to the optical path that the base ray travels from the positively powered optical system to the first curved mirror.

8. The image projection apparatus of claim 7, wherein conditional formulae (1) and (2) below are fulfilled: 15<θ1<45  (1)30<θ2<60  (2)

9. The image projection apparatus of claim 1, wherein conditional formula (3) below is fulfilled: 25<θ3<50  (3)

10. The image projection apparatus of claim 9, wherein conditional formulae (1) and (2) below are fulfilled: 15<θ1<45  (1)30<θ2<60  (2)

11. The image projection apparatus of claim 1, wherein conditional formula (4) below is fulfilled: 1.0<H×r(MC1)<3.0  (4)

12. The image projection apparatus of claim 11, wherein conditional formulae (1) and (2) below are fulfilled: 15<θ1<45  (1)30<θ2<60  (2)

13. The image projection apparatus of claim 1, wherein conditional formula (5) below is fulfilled: 2.5<H×r(MC2)<6.5  (5)

14. The image projection apparatus of claim 13, wherein conditional formulae (1) and (2) below are fulfilled: 15<θ1<45  (1)30<θ2<60  (2)

15. The image projection apparatus of claim 1, wherein conditional formula (6) below is fulfilled: 0.5<D(PSIS−MC1)/V<1.2  (6)

16. The image projection apparatus of claim 15, wherein conditional formulae (1) and (2) below are fulfilled: 15<θ1<45  (1)30<θ2<60  (2)

17. The image projection apparatus of claim 15, wherein conditional formula (3) below is fulfilled: 25<θ3<50  (3)

18. The image projection apparatus of claim 17, further comprising: the light modulation element that emits the image light.

19. The image projection apparatus of claim 1, wherein an optical path changing element for changing an optical path of the image light is disposed in an optical path within the positively powered optical system or in an optical path from the positively powered optical system to the curved-mirror optical system.

20. The image projection apparatus of claim 1, further comprising: the light modulation element that emits the image light.