Image projection device with suppressed moire

• US 5,580,144 A
• Filed: 05/24/1995
• Issued: 12/03/1996
• Est. Priority Date: 05/26/1994
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Stroomer, Martinus V. C.
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US08/449,133
• Time in Patent Office: 559 Days
• Field of Search: 353/31, 353/33, 353/34, 353/37, 353/38, 353/24, 353/22, 353/69, 353/81, 353/100, 359/40, 359/49
• US Class Current: 353/69
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/149 using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: G02B 27/60 Systems using moiré fringes
• CPC Class Codes: G02B 5/00 Optical elements other than lenses light guides G02B6/00; optical logic elements G02F3/00

Abstract

The invention relates to an image projection device. This device comprises an illumination system having a lamp for supplying an illumination beam, at least one image display panel for modulating the illumination beam in accordance with an image to be projected to a signal beam, and a projection lens system for projecting the image on a projection screen. To suppress Moire interference between the structure of the image projection screen and the image display panel, an optically transparent beam-displacing element is arranged at an angle with respect to the signal beam axis in at least a portion of the signal beam in the light path between the image display panel and the projection screen at a position where a lamp image is present.

Claims

1. An image projection device comprising an illumination system having a lamp for supplying an illumination beam, at least one image display panel having a periodical structure of pixels for modulating the illumination beam in accordance with an image to be projected to a signal beam, and a projection lens system for projecting the image on an image projection screen, characterized in that an optically transparent beam-displacing element is arranged at an angle with respect to the signal beam axis and extends through only a portion of the signal beam in the light path between the image display panel and the projection screen at a position where a lamp image is present.

2. An image projection device as claimed in claim 1, characterized in that the beam-displacing element extends in substantially half the signal beam.

3. A colour image projection device comprising an illumination system having a lamp for supplying an illumination beam, means for splitting the radiation beam into three monochrome sub-beams, three monochrome image display panels having a periodical structure of pixels for modulating the sub-beams in conformity with an image to be projected to signal sub-beams, means for recombining the signal sub-beams to a single signal beam, and a projection lens system for projecting the image on an image projection screen, characterized in that an optically transparent beam-displacing element is arranged at an angle with respect to the signal beam axis and extends through only a portion of the signal beam at a position where a lamp image is present.

4. An image projection device comprising an illumination system having a lamp for supplying an illumination beam, at least one image display panel having a periodical structure of pixels for modulating the illumination beam in accordance with an image to be projected to a signal beam, and a projection lens system for projecting the image on an image projection screen, said projection lens system having an entrance pupil, characterized in that an optically transparent beam-displacing element is arranged at an angle with respect to the signal beam axis in a portion of the signal beam between the image display panel and the projection screen at a position where a lamp image is present, said position being in the entrance pupil.

5. An image projection device as claimed in claim 4 wherein the beam-displacing element extends in substantially half the signal beam.