U.S. Philips Corporation

Wilhelmus A Timmers

Jill F Goldenberg

Martinus V Stroomer

Adrianus H Van Den Brandt

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.

Image projection system with autofocusing

An efficient illumination system for an image projection apparatus is described, which system comprises a radiation source (20), a concave reflector (21) and a first and a second lens plate (25, 28) each being provided with a matrix of lenses (26, 29) for forming superimposed images of the radiation source on the object (1) to be illuminated, the aspect ratio of the lenses (26, 29) corresponding to that of the object (1).

Optical illumination system and projection apparatus comprising such a

In a liquid crystal projection t.v. system the color gradient over the projected image, which is due to angular sensitivity of the dichroic mirrors, is minimized by introducing a field lens (61,62,63) next to the light values or LC-panels (21, 22, 23) in the light paths of the blue (b.sub.B), green (b.sub.G) and red (b.sub.R) beams. By chosing different length light paths before and after the light valves and LC-panels a difference in angular sensitivity of the separation mirror (41,42) and the recombination mirrors (52,53) can be compensated for.

Modulation system for projection display

A low-throughput illumination system is described, comprising a radiation source (1), a plurality of condensors (2, 14; 3, 15) for forming a plurality of beams (b.sub.1, b.sub.2) from the radiation supplied by the source and a first reflector (4, 5) for each beam, which reflectors direct the beam towards the principal axis (00'). The system comprises second reflectors (6, 7) which deflect the beams in the direction of the principal axis so that the beams have their narrowest constrictions (8, 9) in the exit plane (10) and are located close together.

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Eindhoven, Netherlands

Wilhelmus A Timmers