Apparatus for detecting the inclination angle of a projection screen and projector comprising the same

ÄProblemÜ To provide a simple-structured angle detecting apparatus and a projector utilizing a line-type passive range-finding device for use on the camera or the like. ÄMeans for ResolutionÜ A control circuit (5) computes a relative horizontal inclination angle between a screen (1) and a projector (2) on the basis of range-finding computing results achieved by a line-type passive range-finding device (3), and a relative vertical inclination angle between a screen (1) and a projector (2) on the basis of range-finding computing results achieved by a line-type passive range-finding device (4). A display driving section (7) adjusts a projection optical system (8) including a condensing lens on the basis of the vertical and the horizontal inclination angles computed by the control circuit (5), thereby correcting for a keystone distortion in an image projected.