Image projection system with autofocusing
AssigneeU.S. Philips Corporation
InventorWilhelmus A. G. Timmers
Life of this patent
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Abstract
An image projection device comprising at least one display panel (26, 27, 28), a projection lens system (C) and a focus error detection system (FS) is described. Since the radiation source (50) and the radiation-sensitive detector (51) of the focus error detection system are arranged in planes which effectively coincide with the plane of the display panel (28), and a focus measuring beam b traverses the projection lens system twice on its path to and from a projection screen (D), an accurate and reliable focus error signal (S.sub.f) is obtained.
Claims34
An image projection device comprising a display system having at least a display panel for generating an image to be projected, a projection lens system for projecting the image formed by the display system on a projection screen, a focus error detection system provided with an auxiliary radiation source which supplies a focus measuring beam, and a radiation-sensitive detector for converting focus measuring beam radiation reflected by the projection screen into a focus error signal, wherein the improvement comprises that the auxiliary radiation source is arranged in a plane which, viewed from the projection lens system, effectively coincides with the plane of a display panel and emits a focus measuring beam whose radiation on its path from the radiation source to the detector traverses the projection lens system twice by the projection screen, and in that the detector is arranged in a plane which, effectively coincides with the plane-of the auxiliary radiation source.
Dependencies are inferred from the claim text.