Abstract: A method of generating a color wheel index signal for use in a display system (10) that uses a spatial light modulator (14) and a color wheel (15). The index signal is compared to a reference signal associated with an input image signal so that the color wheel and the data being displayed can be synchronized (FIG. 2). The index signal is generated by placing a color-sensitive photodetector (14a) in close proximity to the spatial light modulator (14). Light filtered through the color wheel (15) illuminates both the spatial light modulator (14) and the photodetector (14a). The photodetector (14a) responds to color transitions in the filtered light, generating a pulse in response to each transition to the color to which it is sensitive.

Abstract: A motor control unit (15c) for synchronizing a color wheel (15) to an incoming video signal and for re-synchronizing the color wheel after a channel change. The motor control unit (15c) has an error control unit (31), which detects an out-of-phase condition, and derives a color wheel sync signal from the pixel sample clock adjusted by any phase error. A drive unit (33) phase locks this sync signal to an index signal provided by the color wheel. The result is a tightly controlled re-synchronization that minimizes perceived effects.

Abstract: A digital motor controller (17) for controlling both the phase and speed of a brushless DC motor (16). An error detection unit (21) detects a speed error or a phase error. An error logic unit (22) uses the error to determine a speed control value, that is proportional to represent an average motor input voltage that varies from the current input voltage by an amount determined by the error. A pulse width modulation unit (23) receives the speed control value and uses it to determine the duty cycle for the motor drive signals. A commutation unit (24) modulates the appropriate drive signal, and a drive stage (27) delivers the drive signals to the motor (16).