driver is controlled to output the corresponding power level in the next time segment so as to adjust the light intensities in different time segments take a color wheel having four color sections of white color w red color r green color g and blue color b for example each of the w r g and b sections has a fan shaped area whose inner angle is 90 degree in relation to the rotation axis it is certainly that the inner angles may be varied according to the manufacturer 39 s design in a case that four time segments are defined in one cycle period the duration of each time segment is equal to one fourth of the cycle period in accordance with a key feature of the present invention the numbers of pulses contained in the time interval t 0 at the tail portion of a current time segment define the power level to be outputted by the lamp driver in the next time segment as a result the lamp driver is controlled to output the corresponding power level in the next time segment so as to adjust the light intensities in different time segments in the other embodiments the number of time segments is less than the number of color sections of the color wheel under this circumstance the light intensities of different colors may be identical fig3 is a schematic block functional diagram illustrating a luminance control device of implementing the luminance control method as shown in fig2 the luminance control device includes a digital light processing dlp module 30 a lamp driver 32 and a power.