US 5,231,481 AGranted

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

AssigneeThomson-CSF

InventorsJean-Yves Eouzan, Tristan de Couasnon, Yvon Fouche

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Abstract

A projection display device is provided with a negative feedback chain designed to correct all the faults of the projected image, said faults resulting as much from the projection tubes and from their optic systems (geometrical or focusing faults) as from the differences between these tubes (faults in convergence, colorimetry or uniformity of brilliance). The negative feedback chain comprises a test chart generating means, a means to retake the entire projected image and means for the comparision of the signals coming from the test image and from the retaken image. Correction signals are prepared on the basis of this comparison and are applied to the different control circuits defining the projection characteristics. The disclosed device can also be used for the real-time follow-up of the adjustments obtained in a phase prior to the projection of the sequence of useful video images. The invention can be applied notably to video projectors, retro-projection display devices or beam-index tubes.

Claims10

Dependent claims

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.

1 more element

Dependencies are inferred from the claim text.