Patent ID: 7887196

Claim:
A method for operating a projection system, wherein a brightness level in an image is represented by the total length of a number of light switch-on phases within a particular image cycle, wherein a high pressure discharge lamp of the projection system is operated via a lamp driver with an essentially square-wave alternating current so that an overshoot sequence, which occurs in the alternating current after a current zero crossing during operation of the high pressure discharge lamp, has a frequency so high that for each possible brightness level at least one full period of the overshoot sequence lies essentially within a light switch-on or switch-off phase following the zero crossing; and wherein the brightness level is represented digitally by a sequence of bits with different values within an image cycle, the bits respectively being defined by the length of a light switch-on phase in the relevant image cycle, and the high pressure discharge lamp being operated so that the frequency of the overshoot sequence is so high that at least one full period of the overshoot sequence lies essentially within the switching phase of a least significant bit.