US 2004/0070694 A1 · Projection-type display apparatus

Abstract

In measuring the angle of inclination of a liquid crystal projector with respect to the screen for automatically adjusting a trapezoidal distortion, the calculation of the angle of inclination by determining the distance from the screen using a distance sensor conventionally requires a high distance measurement accuracy and hence an expensive distance sensor. According to the invention, a distance sensor is rotated and the level of the wave reflected from it is observed. The angle of inclination with respect to the screen is detected from the rotational angle associated with the maximum value of the level of the reflected wave thereby to correct the trapezoidal distortion. In this way, the trapezoidal distortion can be adjusted automatically using an inexpensive distance sensor.

Claims19

Dependent claims

A projection-type display apparatus for projecting an input video signal in enlarged form on a screen, comprising:

a sensor which radiates selected one of an ultrasonic wave and light on said screen and receives said selected one of said ultrasonic wave and said light reflected from said screen;
a rotator which rotates said sensor;
a detector which detects the level of said received signal;
a circuit which corrects the trapezoidal distortion of said video signal based on the result of detection from said level detection means;
and
projection means;
wherein the video signal processed for correction of the trapezoidal distortion is projected on said screen.

4 more elements

Dependencies are inferred from the claim text.

Projection-type display apparatus

Life of this patent

Projection-type display apparatus

Life of this patent

Abstract

Claims19