Projector and method for igniting lamp

1. A method for igniting a lamp of a projector, the projector also comprising a casing and a fan, the fan being for cooling the lamp, the casing having an air inlet, said method comprising the steps of:

(a) in response to power-off of the projector, sensing a first temperature at the air inlet and a second temperature near the lamp, and calculating a first temperature difference between the first temperature and the second temperature;

(b) in response to power-on of the projector, obtaining an aftercooling time, and judging whether the aftercooling time is shorter than a predetermined cooling time, if YES, performing step (c); otherwise, performing step (g);

(c) sensing a third temperature at the air inlet and a fourth temperature near the lamp, and calculating a second temperature difference between the third temperature and the fourth temperature;

(d) judging whether a ratio of the second temperature difference to the first temperature difference is larger than a threshold; if YES, performing step (e); otherwise, performing step (g);

(e) calculating a re-cooling time according to a condition of the ratio, wherein when the ratio is increasing, the calculated re-cooling time is increasing accordingly, when the ratio is decreasing, the calculated re-cooling time is decreasing accordingly;

(f) controlling the fan to operate for the re-cooling time to cool the lamp; and

(g) igniting the lamp.

2. The method of claim 1 , before step (a), further comprising the step of:

periodically updating the first temperature difference during power-on of the projector.

3. The method of claim 1 , wherein the aftercooling time represents an interval from power-off of the projector to complete loss of power in the projector.

4. The method of claim 1 , wherein the aftercooling time represents an interval from power-on of the projector switched to next power-on of the projector.

5. The method of claim 3 , wherein if power-off the projector occurs due to power-cut of the projector, the aftercooling time is equal to 0.

6. The method of claim 1 , wherein the re-cooling time is calculated according to the following formula:

TimeB

=

(

TimeF

-

TimeA

)

-

(

1

-

V

⁢

⁢

2

/

V

⁢

⁢

1

)

1

-

X

*

TimeF

;

wherein TimeB represents the re-cooling time, TimeF represents the predetermined cooling time, TimeA represents the aftercooling time, V 1 represents the first temperature difference, V 2 represents the second temperature difference, and X represents the threshold.

7. The method of claim 1 , wherein step (f) further comprises:

updating the aftercooling time to be 0 after the lamp is cooled.

8. A projector, comprising:

a casing, having an air inlet;

a lamp, disposed in the casing;

a fan, disposed in the casing, for cooling the lamp;

a first temperature sensor, disposed at the air inlet of the casing, in response to power-off of the projector, the first temperature sensor sensing a first temperature; in response to power-on of the projector, the first temperature sensor sensing a third temperature;

a second temperature sensor, disposed near the lamp, in response to power-off of the projector, the second temperature sensor sensing a second temperature;

in response to power-on of the projector, the second temperature sensor sensing a fourth temperature; and

a processor, electrically coupled to the lamp, the fan, the first temperature sensor and the second temperature sensor, respectively, in response to power-off of the projector, the processor calculating a first temperature difference between the first temperature and the second temperature; in response to power-on of the projector, the processor obtaining an aftercooling time and judging whether the aftercooling time is shorter than a predetermined cooling time, if NO, the processor igniting the lamp; otherwise, the processor calculating a second temperature difference between the third temperature and the fourth temperature, and then judging whether a ratio of the second temperature difference to the first temperature difference is larger than a threshold, if NO, the processor igniting the lamp; otherwise, the processor calculating a re-cooling time according to a condition of the ratio, wherein when the ratio is increasing, the calculated re-cooling time is increasing accordingly, when the ratio is decreasing, the calculated re-cooling time is decreasing accordingly; afterwards, the processor controlling the fan to operate for the re-cooling time to cool the lamp, and then igniting the lamp.

9. The projector of claim 8 , wherein during power-on of the projector, the processor updates the first temperature difference periodically.

10. The projector of claim 8 , wherein the aftercooling time represents an interval from power-off of the projector to complete loss of power in the projector.

11. The projector of claim 8 , wherein the aftercooling time represents an interval from power-on of the projector switched to a next power-on of the projector.

12. The projector of claim 10 , wherein if power-off of the projector occurs due to power-cut of the projector, the aftercooling time is equal to 0.

13. The projector of claim 8 , wherein the re-cooling time is calculated according to the following formula:

TimeB

=

(

TimeF

-

TimeA

)

-

(

1

-

V

⁢

⁢

2

/

V

⁢

⁢

1

)

1

-

X

*

TimeF

;

where TimeB represents the re-cooling time, TimeF represents the predetermined cooling time, TimeA represents the aftercooling time, V 1 represents the first temperature difference, V 2 represents the second temperature difference, and X represents the threshold.

14. The projector of claim 8 , wherein after the lamp is cooled, the processor updates the aftercooling time to be 0.

15. A method for igniting a lamp of a projector, the projector also comprising a casing and a fan, the fan being for cooling the lamp, the casing having an air inlet, said method comprising the steps of:

(a) in response to power-off of the projector, sensing a first temperature at the air inlet and a second temperature near the lamp, and calculating a first temperature difference between the first temperature and the second temperature;

(b) in response to power-on of the projector, sensing a third temperature at the air inlet and a fourth temperature near the lamp, and calculating a second temperature difference between the third temperature and the fourth temperature;

(c) according to a ratio of the second temperature difference to the first temperature difference, calculating a re-cooling time, wherein when the ratio is increasing, the calculated re-cooling time is increasing accordingly, when the ratio is decreasing, the calculated re-cooling time is decreasing accordingly;

(d) controlling the fan to operate for the re-cooling time to cool the lamp; and

(e) igniting the lamp.

16. The method of claim 15 , before step (a), further comprising the step of:

periodically updating the first temperature difference during power-on of the projector.

17. The method of claim 15 , wherein calculating the re-cooling time is performed by the step of:

judging whether the ratio of the second temperature difference to the first temperature difference is larger than a threshold; and if YES, calculating the re-cooling time according to the following formula:

TimeB

=

(

TimeF

-

TimeA

)

-

(

1

-

V

⁢

⁢

2

/

V

⁢

⁢

1

)

1

-

X

*

TimeF

;

wherein TimeB represents the re-cooling time, TimeF represents the predetermined cooling time, TimeA represents the aftercooling time, V 1 represents the first temperature difference, V 2 represents the second temperature difference, and X represents the threshold.

18. The method of claim 17 , wherein the aftercooling time represents an interval from power-off of the projector to complete loss of power in the projector.

19. The method of claim 17 , wherein the aftercooling time represents an interval from power-on of the projector switched to a next power-on of the projector.

20. The method of claim 18 , wherein if power-off of the projector occurs due to power-cut of the projector, the aftercooling time is equal to 0.

21. The method of claim 17 , wherein step (d) further comprises:

updating the aftercooling time to be 0 after the lamp is cooled.