Patent ID: 7891820

Claim:
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.