Patent ID: 8251524

Claim:
A projection display apparatus for displaying an image on a projection plane by projection, comprising: an image capturing unit capturing an image; an angle calculator calculating an angle of the projection plane relative to the projection display apparatus; a straight line detector detecting at least one reference line segment in the captured image; a line segment complementing section setting at least one complementary line segment in the captured image on the basis of the calculated angle so that an area on the projection plane corresponding to an area defined by the reference line segment and the complementary line segment is rectangular; a vanishing point calculator calculating a vertical vanishing point through which a straight line in the captured image corresponding to a line perpendicular to a predetermined reference plane passes and a horizontal vanishing point through which a straight line in the captured image corresponding to a line parallel to the predetermined reference plane passes on the basis of the calculated angle; and a keystone corrector correcting a keystone distortion of an image displayed on the projection plane on the basis of the reference line segment and the complementary line segment, wherein a total number of reference line segments and complementary line segments equals four.