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Projection display device with negative feedback loop to correct all the faults of the projected image

  • US 5,231,481 A
  • Filed: 03/21/1991
  • Issued: 07/27/1993
  • Est. Priority Date: 03/23/1990
  • Status: Expired due to Fees
First Claim
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1. A video projection display device for projecting video images on a screen for detecting and correcting faults in the projected video images, comprising:

  • test chart signal generating means for generating at least one test chart signal to be projected on the screen;

    projecting means for projecting either the at least one test chart signal or a useful image on the screen, the projecting means comprising at least three projection tubes respectively associated with three color video channels to be superimposed, one of the three color video channels being a reference channel;

    video camera means for retaking the test chart and video images projected on the screen;

    computing means for measuring and analyzing images retaken by the video camera means, including comparing means for comparing temporal and amplitude differences between transitions of image signals between the at least one test chart projected on the screen and retaken by the video camera and the test chart signal generated by the test chart generating means, wherein the computing means calculates correction signals to be applied to the projecting means to correct faults in the projected video images.

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