| 摘要 |
PURPOSE:To enable highly accurate focus detection whatever brightness a photographic lens in use has by properly switching the stop opening shape of a stop mounted in front of a secondary optical system according to the brightness of a projection lens in use. CONSTITUTION:The pupil 7 of an objective 1 is divided into plural areas, light quantity distributions regarding a subject image are formed by using pieces of luminous flux passed through the respective areas, and the relative position relation of the light quantity distributions is found to detect the focusing state of the objective 1. Then a secondary optical system 4 which detects the light quantity distributions regarding the subject image and the stop 6 which limits luminous flux passing through the secondary optical system are provided; and the stop is constant in the distance L0 between the centers of gravity of a couple of openings 6 and the couple of openings vary in area so that the maximum width 11 of the openings in the direction of the straight line connecting the centers of gravity of the openings and the maximum width W of the openings in the direction Z crossing the straight line direction at right angles are different in variation quantity. Consequently, the best focus detection becomes possible corresponding to the brightness of the photographic lens. |
