Display device

1. A display device, comprising:

a display element including a display surface on which image is displayed;

a first mirror and a second mirror that each reflect emission light emitted from the display surface of the display element;

a first λ/4 plate; and

a polarization element, wherein:

the polarization element is configured to reflect and transmit the emission light,

the emission light is reflected off the polarization element, then reflected off one of the first and second mirrors, then transmitted though the polarization element, then reflected off another of the first and second mirrors, and then reflected again on the polarization element,

the first mirror is closer to one of an upper end and a lower end of the display surface,

the second mirror is closer to another of the upper end and the lower end of the display surface,

the polarization element is located between the first mirror and the second mirror and opposes the display surface,

the first λ/4 plate is located between the polarization element and the first mirror,

the polarization element includes:

a reflective polarization plate opposing the display surface and the first mirror; and

a second λ/4 plate opposing the second mirror, and

the emission light is:

(a) reflected off the reflective polarization plate;

(b) transmitted through the first λ/4 plate;

(c) reflected off the first mirror to be transmitted again through the first λ/4 plate;

(d) transmitted through each of the reflective polarization plate and the second λ/4 plate;

(e) reflected off the second mirror;

(f) transmitted through the second λ/4 plate; and

(g) reflected off the reflective polarization plate to be transmitted again through the second λ/4 plate.

2. The display device according to claim 1 , wherein

at least one of the first mirror and the second mirror is a concave mirror.

3. The display device according to claim 2 , wherein

the second mirror is a concave mirror, and

at least one of an upper end part and a lower end part of the second mirror is curved to have a convex shape in a front view of the second mirror.

4. The display device according to claim 2 , wherein

the second mirror is a concave mirror, and

the polarization element has an end part opposing the second mirror, the end part being curved to have a convex shape corresponding to a concave shape of the second mirror.

5. The display device according to claim 1 , further comprising:

a transmissive polarization plate opposing the second λ/4 plate of the polarization element; and

a third λ/4 plate located between the transmissive polarization plate and the second λ/4 plate, wherein

the emission light which is reflected off the reflective polarization plate and then transmitted again through the second λ/4 plate is transmitted through each of the third λ/4 plate and the transmissive polarization plate.

6. The display device according to claim 1 ,

the polarization element has a wedge-shaped cross section, and

the polarization element includes a first end part closer to the second mirror and a second end part closer to the first mirror, the first end part having a thickness different from a thickness of the second end part.

7. The display device according to claim 1 , wherein

the first mirror is a Fresnel mirror.

8. The display device according to claim 7 , wherein

the first λ/4 plate is inclined with respect to the first mirror.

9. The display device according to claim 1 , wherein

a perpendicular line perpendicular to the display surface is not parallel with an optical path of the emission light that is transmitted again through the second λ/4 plate after being reflected off the reflective polarization plate.

10. The display device according to claim 1 , wherein

the emission light emitted from the display surface is a linear polarized light having a polarization direction perpendicular to a transmission axis of the reflective polarization plate, and

the polarization element is inclined with respect to the display surface, about an axis line parallel to the polarization direction of the linear polarized light.

11. A display device comprising:

a display element including a display surface on which image is displayed;

a first mirror and a second mirror that each reflect emission light emitted from the display surface of the display element;

a polarization element configured to reflect and transmit the emission light;

a first λ/4 plate located between the polarization element and the first mirror; and

a case housing the display element, the first and second mirrors, and the polarization element, the case having an opening from which the emission light exits, wherein:

the emission light is reflected off the polarization element, then reflected off one of the first and second mirrors, then transmitted though the polarization element, then reflected off another of the first and second mirrors, and then reflected again on the polarization element,

in a view from the opening,

the display element is disposed in an upper part of the case,

the first mirror is disposed in an innermost part of the case, and

the second mirror is disposed in a lower part of the case,

the polarization element is located between the display element and the second mirror and is inclined to cause an upper end part of the polarization element to be closer to the opening than a lower end part of the polarization element is,

the polarization element is located between the first mirror and the second mirror and opposes the display surface,

the polarization element includes:

a reflective polarization plate opposing the display surface and the first mirror; and

a second λ/4 plate opposing the second mirror, and

the emission light is:

(a) reflected off the reflective polarization plate;

(b) transmitted through the first λ/4 plate;

(c) reflected off the first mirror to be transmitted again through the first λ/4 plate;

(d) transmitted through each of the reflective polarization plate and the second λ/4 plate;

(e) reflected off the second mirror;

(f) transmitted through the second λ/4 plate; and

(g) reflected off the reflective polarization plate to be transmitted again through the second λ/4 plate.

12. The display device according to claim 11 , wherein

at least one of the first mirror and the second mirror is a concave mirror.

13. The display device according to claim 12 , wherein

the second mirror is a concave mirror, and

at least one of an upper end part and a lower end part of the second mirror is curved to have a convex shape in a front view of the second mirror.

14. The display device according to claim 12 , wherein

the second mirror is a concave mirror, and

the polarization element has an end part opposing the second mirror, the end part being curved to have a convex shape corresponding to a concave shape of the second mirror.

15. The display device according to claim 11 , further comprising:

a transmissive polarization plate opposing the second λ/4 plate of the polarization element; and

a third λ/4 plate located between the transmissive polarization plate and the second λ/4 plate, wherein

the emission light which is reflected off the reflective polarization plate and then transmitted again through the second λ/4 plate is transmitted through each of the third λ/4 plate and the transmissive polarization plate.

16. The display device according to claim 11 ,

the polarization element has a wedge-shaped cross section, and

the polarization element includes a first end part closer to the second mirror and a second end part closer to the first mirror, the first end part having a thickness different from a thickness of the second end part.

17. The display device according to claim 11 , wherein

the first mirror is a Fresnel mirror.

18. The display device according to claim 17 , wherein

the first λ/4 plate is inclined with respect to the first mirror.

19. The display device according to claim 11 , wherein

a perpendicular line perpendicular to the display surface is not parallel with an optical path of the emission light that is transmitted again through the second λ/4 plate after being reflected off the reflective polarization plate.

20. The display device according to claim 11 , wherein

the emission light emitted from the display surface is a linear polarized light having a polarization direction perpendicular to a transmission axis of the reflective polarization plate, and

the polarization element is inclined with respect to the display surface, about an axis line parallel to the polarization direction of the linear polarized light.