Patent ID: 8836869

Claim:
A projection display apparatus including: a display unit that generates an image; a projection unit that projects the image, via a projection lens; a control unit configured to control the image; a storage unit that stores a first horizontal reference value corresponding to an installed state of the projection display apparatus which is in a vertically not-reversed state, and a second horizontal reference value corresponding to an installed state of the projection apparatus which is in a vertically reversed state; a vertical reversal determination unit that determines the installed state of the projection display apparatus; a detection unit that issues an output (Vout) depending on an inclination angle θ of an optical axis of the projection lens; and an angle calculation unit that calculates the inclination angle θ based upon output (Vout) and a selected horizontal reference value selected from either the first or second horizontal references value, wherein the selected horizontal reference value is determined by the control unit based upon input from the vertical reversal determination unit, wherein the control unit is configured to execute a trapezoid correction on the image generated by the display unit, by using the inclination angle of the projection display apparatus calculated by the angle calculation unit, wherein the first horizontal reference value subtracted from the second horizontal reference value equals sin[2×(θG 0 −θL 0 )], where θG 0 is an inclination angle of a detection axis of the detection unit relative to the horizontal state, and θL 0 is an inclination angle of the optical axis of the projection lens relative to the horizontal state.