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US 4,376,949 AGranted
Color projection TV systems
AssigneeZenith Radio Corporation
InventorWilliam A. Rowe
Life of this patent
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AssigneeZenith Radio Corporation
InventorWilliam A. Rowe
Estimating the term…
A projection television system having three different primary color pitcure tubes in an in-line configuration, one centrally located on the projection screen axis and the other two on opposite sides of the axis. In order to compensate for the defocussing which these off-axis locations produce at the edges of the projected image, the off-axis picture tubes are rotated relative to the optical axes of their respective focussing lenses, thus rotating the corresponding projected images into coincidence with the projection screen. The off-axis positioning also produces color shading by making the square law fall-off in illumination vary across the projection screen, and also by producing a trapezoidal distortion which is compensated by pre-distortion which introduces additional color shading effects. The first effect is reduced by making the lenses tangent or nearly tangent to each other, thus minimizing the angular deviation of the projection axes. The second effect results from the use of slanted CRT electron guns to achieve the compensatory trapezoidal pre-distortion of the off-axis object images, and is corrected by laterally offsetting these object images (CRT rasters) from the optical axes of their focussing lenses. This off-set can be achieved by laterally displacing the entire picture tube, or by laterally displacing the electron gun relative to the tube faceplate, or by magnetically deflecting the electron beam. The degree of offset is preferably such as to equalize the distances of all object image corner points from the lens axis. The offset then must itself be compensated by rotating the off-axis lenses so that their optical axes are underconverged.
In an image projection system of the type comprising:
In an image projection system of the type comprising:
A projection television system of the composite image type, comprising:
An image projection system of the kind having:
A composite image projection system of the kind having:
An angle projection system comprising:
An in-line composite color image projection system of the type having a projection screen, a plurality of projectors each arranged to project respective different colored portions of a composite image on said screen, each projector including respective lens means having respective optical axes, said lens means being located in side-by-side relation to each other, and at least one of said lens means being skewed so that its optical axis is at an acute angle to said screen axis;
Dependencies are inferred from the claim text.