Projection display apparatus using liquid cooling and air cooling

1. A projection display apparatus comprising:

a liquid crystal unit assembly which includes a liquid crystal panel, an incident side polarizing plate and an emitting side polarizing plate which are arranged on an incident side and on an emitting side of said liquid crystal panel, respectively, and a color combining prism;

a fan;

a duct which is connected to said fan and which is provided with an opening for supplying cooling air, wherein said opening is arranged near said liquid crystal panel and said incident side polarizing plate;

a holder for holding said emitting side polarizing plate and said color combining prism; and

a heat exchanger which is connected to said holder, wherein said heat exchanger uses liquid coolant.

2. The projection display apparatus according to claim 1 , wherein said heat exchanger is connected to said holder via a surface of said holder, said surface being opposite to a surface to which said color combining prism is attached.

3. The projection display apparatus according to claim 2 , further comprising:

another holder for holding said color combining prism via a surface of said color combining prism, said surface of the color combining prism being opposite to a surface to which said holder is attached; and

another heat exchanger, wherein said another heat exchanger is connected to said another holder via a surface of said another holder, said surface of the another holder being opposite a surface to which said color combining prism is attached.

4. The projection display apparatus according to claim 3 , wherein each of said heat exchanger and said another heat exchanger is provided with a passage for said liquid coolant, said passage being arranged inside said heat exchanger and said another heat exchanger, and

wherein said projection display apparatus further comprises:

a pump for circulating said liquid coolant; and

a radiator for cooling said liquid coolant.

5. The projection display apparatus according to claim 4 , wherein said radiator is arranged near an air intake of said fan.

6. The projection display apparatus according to claim 3 , wherein said another heat exchanger includes a fin that is connected to said another holder, said fin being inserted into said duct, and

wherein said heat exchanger is provided with a passage for said liquid coolant said passage being arranged inside said heat exchanger, and

wherein said projection display apparatus further comprises:

a pump for circulating said liquid coolant; and

a radiator for cooling said liquid coolant.

7. The projection display apparatus according to claim 3 , wherein said another heat exchanger comprises a fin that is connected to said another holder.

8. The projection display apparatus according to claim 1 , wherein said emitting side polarizing plate is sandwiched between a translucent plate and said color combining prism, and

wherein said emitting side polarizing plate is connected to said holder by a frame member.

9. The projection display apparatus according to claim 1 , wherein said color combining prism has a higher thermal conductivity than said emitting side polarizing plate.

10. The projection display apparatus according to claim 1 , wherein the emitting side polarizing plate is not cooled by the cooling air.

11. The projection display apparatus according to claim 1 , wherein the emitting side polarizing plate is cooled by exchanging part of heat in said emitting side polarizing plate with said liquid coolant rather than the cooling air.

12. The projection display apparatus according to claim 1 , wherein heat is removed from the emitting side polarizing plate by a different mechanism than a mechanism that removes heat from the incident side polarization plate.

13. The projection display apparatus according to claim 1 , wherein said projection display apparatus further comprises another holder which is connected with a pin fin type heat sink that is installed inside said duct.

14. A method for cooling a liquid crystal unit which includes a liquid crystal panel, an incident side polarizing plate and an emitting side polarizing plate which are arranged on an incident side and on an emitting side of said liquid crystal panel, respectively, said method comprising:

a first cooling of said incident side polarizing plate and said liquid crystal panel through heat exchange with cooling air; and

a second cooling of said emitting side polarizing plate by exchanging part of heat in said emitting side polarizing plate with liquid coolant.

15. The method according to claim 14 , wherein said second cooling comprises:

transmitting heat in said emitting side polarizing plate to said liquid coolant via two sides of said emitting side polarizing plate, said two sides being opposite to each other; and

radiating the heat using a radiator, the heat being transmitted by said liquid coolant.

16. The method according to claim 14 , wherein said second cooling comprises:

transmitting part of heat in said emitting side polarizing plate to a fin that is inserted into a duct, via a first side of said emitting side polarizing plate;

transmitting the heat to the cooling air in said duct, the heat being transmitted to said fin;

conveying the cooling air using a fan, wherein the heat is transmitted to the cooling air;

transmitting part of the heat in said emitting side polarizing plate to the liquid coolant, via a second side that is opposite to said first side of said emitting side polarizing plate; and

radiating the heat using a radiator, the heat being transmitted by said liquid coolant.

17. The method according to claim 16 , wherein said radiating the heat includes drawing the cooling air from an air intake of said fan through said radiator.

18. The method according to claim 14 , wherein heat is removed from the emitting side polarizing plate by a different mechanism than a mechanism that removes heat from the incident side polarization plate.

19. The method according to claim 14 , wherein the emitting side polarizing plate is not cooled by the cooling air.

20. A projection display apparatus comprising:

a liquid crystal unit assembly which includes a liquid crystal panel, an incident side polarizing plate, and an emitting side polarizing plate;

a fan;

a duct which is connected to said fan and which is provided with an opening for supplying cooling air, wherein said opening is arranged near said liquid crystal panel and said incident side polarizing plate rather than said emitting side polarizing plate;

a holder for holding said emitting side polarizing plate and a color combining prism;

a heat exchanger which is connected to said holder, wherein said heat exchanger uses liquid coolant; and

another holder which is connected with a pin fin type heat sink installed inside said duct.