Display device

1. A display device comprising:

a light modulating element which transmits or reflects incident light;

a display unit which emits display light toward the light modulating element; and

a retroreflective element which retroreflects the display light reflected from the light modulating element,

the light modulating element including an inner surface on a side opposed to the display unit and the retroreflective element, and an outer surface on a side opposite to the inner surface,

the light modulating element comprising a first mode of transmitting light incident from the outer surface at a first transmittance, and a second mode of transmitting the light incident from the outer surface at a second transmittance lower than the first transmittance, wherein the light modulating element comprises:

a first polarizing element which is located on a side closer to the inner surface, and includes a first transmission axis which reflects first linearly polarized light and transmits second linearly polarized light crossing the first linearly polarized light;

a second polarizing element including a second transmission axis;

a first substrate comprising a plurality of first control electrodes;

a second substrate comprising a second control electrode opposed to the plurality of first control electrodes; and

a liquid crystal layer which is located between the first polarizing element and the second polarizing element, and is held between the first substrate and the second substrate.

2. The display device of claim 1 , wherein the display unit emits the display light in the first mode, and does not emit the display light in the second mode.

3. The display device of claim 1 , wherein the light modulating element further comprises a third polarizing element which is located between the first polarizing element and the liquid crystal layer, and includes a third transmission axis parallel to the first transmission axis.

4. The display device of claim 1 , further comprising a retardation film which imparts a retardation to transmitted light, wherein

the retardation film is arranged along an inner surface of the retroreflective element.

5. The display device of claim 1 , wherein

at least one of the first control electrode and the second control electrode is a semi-transmissive layer.

6. The display device of claim 1 , wherein the light modulating element comprises:

a semi-transmissive layer located between the first polarizing element and the second polarizing element.

7. The display device of claim 1 , wherein the light modulating element comprises:

a controller which controls a voltage to be applied to the liquid crystal layer for forming a liquid crystal lens in the liquid crystal layer, and

the controller applies a voltage for forming the liquid crystal lens to the liquid crystal layer in the second mode, and does not apply a voltage to the liquid crystal layer in the first mode.

8. A display device comprising:

a light modulating element which transmits or reflects incident light;

a display unit which emits display light toward the light modulating element;

a retroreflective element which retroreflects the display light reflected from the light modulating element; and

a controller which controls the light modulating element,

the controller setting the light modulating element to a first transmittance state having a first transmittance at a display period when the display unit emits the display light, and setting the light modulating element to a second transmittance state having a second transmittance of which is lower than the first transmittance, at a non-display period when the display unit does not emit the display light.

9. The display device of claim 8 , wherein the light modulating element comprises:

a first polarizing element including a first transmission axis;

a second polarizing element including a second transmission axis; and

a liquid crystal layer located between the first polarizing element and the second polarizing element, and

the controller applies a voltage to the liquid crystal layer in the first transmittance state, and does not apply a voltage to the liquid crystal layer in the second transmittance state.

10. The display device of claim 9 , wherein a retardation of the liquid crystal layer in the first transmittance state is substantially zero, and the second transmission axis is parallel to the first transmission axis.

11. The display device of claim 9 , wherein:

a retardation of the liquid crystal layer in the first transmittance state is substantially λ/2, where λ is a wavelength of light transmitted through the liquid crystal layer; and

the second transmission axis crosses the first transmission axis.

12. The display device of claim 8 , wherein the light modulating element comprises:

a first polarizing element including a first transmission axis which reflects first linearly polarized light, and transmits second linearly polarized light crossing the first linearly polarized light;

a second polarizing element including a second transmission axis;

a first substrate comprising a plurality of first control electrodes;

a second substrate comprising a second control electrode opposed to the plurality of first control electrodes; and

a liquid crystal layer which is located between the first polarizing element and the second polarizing element, and is held between the first substrate and the second substrate.

13. The display device of claim 8 , further comprising a retardation film which imparts a retardation to transmitted light, wherein

the retardation film is arranged along an inner surface of the retroreflective element.

14. The display device of claim 8 , wherein the light modulating element comprises:

a first polarizing element including a first transmission axis;

a second polarizing element including a second transmission axis;

a first substrate comprising a plurality of first control electrodes;

a second substrate comprising a second control electrode opposed to the plurality of first control electrodes; and

a liquid crystal layer which is located between the first polarizing element and the second polarizing element, and is held between the first substrate and the second substrate, and

at least one of the first control electrode and the second control electrode is a semi-transmissive layer.

15. The display device of claim 8 , wherein the light modulating element comprises:

a first polarizing element including a first transmission axis;

a second polarizing element including a second transmission axis;

a first substrate comprising a plurality of first control electrodes;

a second substrate comprising a second control electrode opposed to the plurality of first control electrodes;

a liquid crystal layer which is located between the first polarizing element and the second polarizing element, and is held between the first substrate and the second substrate; and

a semi-transmissive layer located between the first polarizing element and the second polarizing element.

16. The display device of claim 8 , wherein the light modulating element comprises:

a first substrate comprising a plurality of first control electrodes;

a second substrate comprising a second control electrode opposed to the plurality of first control electrodes; and

a liquid crystal layer held between the first substrate and the second substrate,

the controller controls a voltage to be applied to the liquid crystal layer for forming a liquid crystal lens in the liquid crystal layer, and

the controller applies a voltage for forming the liquid crystal lens to the liquid crystal layer in the second transmittance state, and does not apply a voltage to the liquid crystal layer in the first transmittance state.