FOCUS DETECTING SYSTEM FOR REFLEX TELEPHOTO LENS AND REFLEX TELEPHOTO LENS

摘要

PURPOSE:To obtain a reflex telephoto lens which is low in cost and compact in constitution and never produces vignetting of lens, by properly discriminating the propriety of focus detection in accordance with data related to the outer and inner diameters and position of an exit pupil read from the lens. CONSTITUTION:A focus detecting means 3 discriminates whether or not optically correct focus detection is possible in accordance with data related to the outer and inner diameters and position of an exit pupil from a reflex telephoto lens ML. Since an operation permitting means 5 actuates the focus detecting means 3 if the discriminated result is 'yes', whether focus detection is possible or not can be discriminated properly even when the reflex telephoto lens ML is used. Moreover, data related to the outer and inner diameters and position of the exit pupil inherent to the lens ML are stored in a fixed state and the data are sent to the camera body side in accordance with read signals from the body side. Therefore, a focus detecting system using an inexpensive compact reflex telephoto lens can be realized and whether focus detection is possible or not can be discriminated.