Patent ID: 8272746

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 two straight lines at a left side and a right side of a frame of the projection plane having the largest integrated value of values correlated with an edge amount along the corresponding straight line out of the straight lines passing through a vertical vanishing point in the captured image, and two straight lines at a top side and a bottom side of the frame of the projection plane having the largest integrated value of values correlated with an edge amount along the corresponding straight line out of the straight lines passing through a horizontal vanishing point in the captured image; and a keystone corrector correcting a keystone distortion of an image to be displayed on the projection plane on the basis of the detection result in the straight line detector.