Projection display apparatus and control method therefor

1. A projection display apparatus projecting image light based on an image signal, comprising:

a lamp;

a display element that modulates light emitted from said lamp according to an amplitude of the image signal, and that emits the light as the image light;

a light intensity controller that changes a lamp power according to a power changing operation that is input from an outside so as to change the lamp power for driving said lamp, and, if the changed lamp power is lower than a rated power of said lamp and supplied to said lamp for at least a certain period of time, generates a control signal for causing a lamp refreshing process to be performed that increases the lamp power to the rated power and then reduces the lamp power to an original power after elapse of a predetermined period of time, identifies an amplitude value of the image signal where an intensity of the image light is constant before and after the change of the lamp power in said lamp refreshing process, and generates a control signal for changing the amplitude of the image signal to the identified amplitude value;

a ballast that drives said lamp and performs said lamp refreshing process according to the control signal, that causes said lamp refreshing process to be performed and that is generated by said light intensity controller; and

an image signal controller that controls the amplitude of the image signal according to the control signal, that causes the amplitude of the image signal to be changed and that is generated by the light intensity controller, and supplies the image signal whose amplitude is controlled to said display element.

2. The projection display apparatus according to claim 1 ,

wherein the predetermined period of time comprises at least a time period required to recover characteristics of said lamp due to a halogen cycle.

3. The projection display apparatus according to claim 1 , wherein said light intensity controller identifies the amplitude value of the image signal based on a ratio of a lamp power when said lamp refreshing process is performed on a lamp power prior to a time when said lamp refreshing process is supposed to be performed.

4. The projection display apparatus according to claim 1 , wherein said light intensity controller generates the control signal to cause said lamp refreshing process to be performed that increases the lamp power to the rated power from a first time to a second time and then reduces the lamp power to the original power from a third time, the third time being after elapse of a predetermined time after the second time to a fourth time.

5. The projection display apparatus according to claim 1 , wherein said light intensity controller generates the control signal to cause said lamp refreshing process to be performed that increases the lamp power to the rated power from a first time to a second time and then reduces the lamp power to the original power thereafter.

6. The projection display apparatus according to claim 1 , wherein said light intensity controller generates the control signal to cause said lamp refreshing process to be performed that increases the lamp power to the rated power then reduces the lamp power to the original power after the lamp power reaches the rated power.

7. The projection display apparatus according to claim 1 , wherein said light intensity controller identifies the amplitude value of the image signal based on a ratio of a lamp power.

8. The projection display apparatus according to claim 1 , wherein the ballast performs control so as to increase the lamp power to the rated power and then return the power to the original power after elapse of the predetermined period of time.

9. The projection display apparatus according to claim 1 , wherein the amplitude of the image signal is changed so that the intensity of the image light is constant before and after the change of the lamp power in the lamp refreshing process.

10. The projection display apparatus according to claim 8 , wherein the rated power comprises a power causing a stable halogen cycle, and

wherein the predetermined period of time is at least a time period required to recover characteristics of lamp due to the halogen cycle.

11. A control method of a projection display apparatus including a lamp and a display element that modulates light emitted from the lamp according to an amplitude of an image signal and that emits the light as image light, the method comprising:

causing a light intensity controller to change a lamp power according to a power changing operation that is input from an outside so as to change the lamp power for driving the lamp, and, if the changed lamp power is lower than a rated power of the lamp and supplied to the lamp for at least a certain period of time, to generate a control signal to cause a lamp refreshing process to be performed that increases the lamp power to the rated power and then to reduce the lamp power to an original power after elapse of a predetermined period of time, to identify an amplitude value of the image signal where an intensity of the image light is constant before and after the change of the lamp power in said lamp refreshing process, and to generate a control signal for changing the amplitude of the image signal to the identified amplitude value;

causing a ballast to drive said lamp and to perform said lamp refreshing process according to the control signal which causes said lamp refreshing process to be performed, the control signal being generated by said light intensity controller; and

causing an image signal controller to control the amplitude of the image signal according to the control signal which causes the amplitude of the image signal to be changed, the control signal being generated by the light intensity controller, and to supply the image signal whose amplitude is controlled to the display element.

12. The control method of a projection display apparatus according to claim 11 ,

wherein the predetermined period of time comprises at least a time period required to recover characteristics of the lamp due to a halogen cycle.

13. The control method according to claim 11 , wherein said causing said light intensity controller further causes said light intensity controller to identify the amplitude value of the image signal based on a ratio of a lamp power when said lamp refreshing process is performed on a lamp power prior to a time when said lamp refreshing process is supposed to be performed.

14. The control method according to claim 11 , wherein said causing said light intensity controller further causes said light intensity controller to generate the control signal to cause said lamp refreshing process to be performed that increases the lamp power to the rated power from a first time to a second time and then reduces the lamp power to the original power from a third time, the third time being after elapse of a predetermined time after the second time to a fourth time.

15. The control method according to claim 11 , wherein said causing said light intensity controller further causes said light intensity controller generates the control signal to cause said lamp refreshing process to be performed that increases the lamp power to the rated power from a first time to a second time and then reduces the lamp power to the original power thereafter.

16. The control method according to claim 11 , wherein said causing said light intensity controller further causes said light intensity controller to generate the control signal to cause said lamp refreshing process to be performed that increases the lamp power to the rated power then reduces the lamp power to the original power after the lamp power reaches the rated power.

17. The control method according to claim 11 , wherein said causing said light intensity controller further causes said light intensity controller to identify the amplitude value of the image signal based on a ratio of a lamp power.

18. The control method according to claim 11 , wherein said causing said ballast further causes the ballast to perform control so as to increase the lamp power to the rated power and then return the power to the original power after elapse of the predetermined period of time.

19. The control method according to claim 18 , wherein the rated power comprises a power causing a stable halogen cycle, and

wherein the predetermined period of time comprises at least a time period required to recover characteristics of lamp due to the halogen cycle.

20. The control method according to claim 11 , wherein the amplitude of the image signal is changed so that the intensity of the image light is constant before and after the change of the lamp power in the lamp refreshing process.