Optical device and projector

1. An optical device comprising:

a light modulation element that modulates a luminous flux emitted from a light source;

a casing that houses the light modulation element;

a holding member that holds the light modulation element, the holding member having a part exposed to the outside;

a refrigerant housed in a housing space surrounded by the casing, the holding member and the light modulation element; and

a convection start unit that is provided in the casing, the convection start unit rotates about a rotation axis to cause convection of the refrigerant.

2. The optical device according to claim 1 , wherein the convection start unit is provided on the holding member.

3. The optical device according to claim 1 , wherein the light modulation element is a transmissive liquid crystal element,

a refrigerant reservoir that stores a part of the refrigerant is provided around an image forming area of the light modulation element in the housing space, and

the convection start unit is provided in the refrigerant reservoir.

4. The optical device according to claim 3 , wherein a polarization member is provided on an outer side of a cover glass that forms the housing space.

5. The optical device according to claim 1 , wherein a rectifying member that rectifies the flow of the refrigerant is provided in the housing space.

6. The optical device according to claim 1 , wherein a driving unit that drives the convection start unit is provided outside of the casing.

7. The optical device according to claim 6 , wherein the driving unit is an electromagnetic motor or piezoelectric ultrasonic motor.

8. The optical device according to claim 1 , wherein a radiation fin is provided at the part of the holding member that is exposed outward from the casing.

9. A projector comprising:

a light source that emits light;

plural optical devices that include the optical device according to claim 1 ;

a light combining unit that has lateral side which is arranged along the plural optical devices, and combines color lights emitted from the plural optical devices; and

a projection unit that projects an optical image combined by the light combining unit.

10. The projector according to claim 9 , further comprising a radiation unit in contact with the holding members of the plural optical devices.

11. The projector according to claim 10 , wherein the light combining unit is a dichroic prism and the radiation unit is provided on a surface of the dichroic prism where the plural optical devices are not provided.

12. An optical device, comprising:

a light modulation element that modulates a luminous flux emitted from a light source;

a casing that houses the light modulation element;

a holding member that holds the light modulation element, the holding member having a part exposed to the outside;

a refrigerant housed in a housing space surrounded by the casing, the holding member and the light modulation element; and

a convection start unit that is provided in the casing and causes convection of the refrigerant, the convection start unit having a driving unit that drives the convection start unit, the driving unit being provided outside of the casing.

13. The optical device according to claim 12 , wherein the driving unit is an electromagnetic motor or piezoelectric ultrasonic motor.

14. An optical device for use with a light source that emits light, the optical device comprising:

a light modulation element that modulates the light emitted from the light source;

a casing;

a holding member that holds the light modulation element;

a cooling chamber surrounded by the casing, the holding member and the light modulation element;

coolant disposed in the cooling chamber, and

a convector provided in the casing and rotatable to cause convection of the coolant.