Projection display apparatus
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorKatsumi Asakawa
Life of this patent
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Abstract
A projection display apparatus with a light source, a light valve and an optical system for projecting an image formed in an image-forming plane of the light valve onto a screen is disclosed. The projection display apparatus includes a first processor for calculating an area of an image projected onto the screen, a photometer for measuring illuminance in the neighborhood of the image projected onto the screen, a second processor for calculating a black-level correction value from the area of the image calculated by the first processor and the illuminance measured by the photometer, and a light-source-power controller for controlling power supplied to the light source on the basis of the black-level correction value calculated by the second processor.
Claims7
A projection display apparatus in which a light emitted from a light source enters a light valve, an image corresponding to an input video signal is formed in an image-forming plane of the light valve, and the formed image is projected onto a screen through an optical system including a zoom lens, the projection display apparatus comprising:
- a distance-measuring device automatically measuring a distance between the projection display apparatus and the screen;
- a first processor for calculating an area of an image projected onto the screen on the basis of a target position of the zoom lens and the distance measured by the distance-measuring device;
- a photometer for measuring illuminance in the neighborhood of the image projected onto the screen;
- a second processor for calculating a black-level correction value from the area of the image calculated by the first processor and the illuminance measured by the photometer;
- and
- a light-source-power controller for controlling power supplied to the light source on the basis of the black-level correction value calculated by the second processor.
A method for controlling a black level value in a projection display apparatus, wherein light emitted from a light source enters a light valve in the projection display apparatus and an image corresponding to an input video signal is formed and projected onto a screen through an optical system, the method steps comprising:
- automatically measuring a distance between the projection display apparatus and the screen;
- calculating an area of an image projected onto the screen by a first processor on the basis of a target position of the zoom lens and the distance measured by the distance-measuring device;
- measuring illuminance, with a photometer, in the neighborhood of the image projected onto the screen;
- calculating, with a second processor, a black-level correction value from the area of the image calculated by the first processor and the illuminance measured by the photometer;
- and
- controlling power supply to the light source, by a light-source-power controller, on the basis of the black-level correction value calculated by the second processor.
Dependencies are inferred from the claim text.