Patent ID: 7425932

Claim:
A projection system comprising: a projection display; at least one light source; and a sensor means for sensing and compensating for changes in the luminous flux emitted by the at least one light source, wherein the at least one light source is configured to have a focal plane situated at an entering face of a rod integrator of the projection system, the rod integrator being positioned in between the at least one light source and the projection display, wherein the focal plane of the at least one light source is subject to change or shift due to instabilities of the at least one light source, wherein light emitted from the at least one light source comprises first and second spatial components (I) and (R) at the entering face which impinge on (i) a central transparent first region and (ii) a second mirrored region, surrounding the first region, respectively, of the entering face of the rod integrator and wherein the light emitted from the at least one light source further comprises a third spatial component (M) which fails to impinge on the entering face and instead is directed (iii) into a region immediately surrounding the entering face, and wherein the sensor means comprises a sensor arrangement configured in a region of the entering face to sense, along a circumference of the rod integrator with weightings that are as equal as possible, the third spatial component of the light from the light source that is directed into the region immediately surrounding the entering face.