| 摘要 |
A method of measuring a zoom ratio of a projection optical system adapted to project image light representing an original image on a projection screen, the method includes: (a) projecting and displaying a measuring image including a measurement point on the projection screen so that the measurement point is displayed at a position with an offset from an optical axis of the projection optical system; (b) detecting a projected measurement point, which is the measurement point projected and displayed on the projection screen, from a measurement point detection position having a fixed position relative to the projection optical system; and (c) determining the zoom ratio using position information of the detected projected measurement point and correspondence between the position information and the zoom ratio, the correspondence being prepared previously. |
