Abstract: An optical element disposed behind a main mirror and inclined relative to the optical axis is arranged at a position to correct aberration in the luminous flux generated by transmission through the main mirror.

Abstract: The AF sensor module primarily comprises condenser lens 16, mirror 17, aperture mask 18, separator lens 19 and CCD 20. Separator lens 19 is located such that its lengthwise center line M may be parallel to the lengthwise center line N of CCD 20 while it is inclined by micro-angle &dgr; with center line M as the rotational axis. By arranging the lens surface of separator lens 19 and the image pickup surface of CCD 20 such that they are non-parallel to each other, reflected light L1 existing due to the reflection of light between separator lens 19 and CCD 20 is prevented from striking CCD 20 once again so that a reduction in the accuracy of focus detection caused by said reflected light may be prevented.

Abstract: The AF sensor module primarily comprises condenser lens 16, mirror 17, aperture mask 18, separator lens 19 and CCD 20. Separator lens 19 is located such that its lengthwise center line M may be parallel to the lengthwise center line N of CCD 20 while it is inclined by micro-angle &dgr; with center line M as the rotational axis. By arranging the lens surface of separator lens 19 and the image pickup surface of CCD 20 such that they are non-parallel to each other, reflected light L1 existing due to the reflection of light between separator lens 19 and CCD 20 is prevented from striking CCD 20 once again so that a reduction in the accuracy of focus detection caused by said reflected light may be prevented.

Abstract: An optical element disposed behind a main mirror and inclined relative to the optical axis is arranged at a position to correct aberration in the luminous flux generated by transmission through the main mirror.

Abstract: A focus detector used in an AF-SLR camera has a plurality of focusing sensors disposed not only in the center but also in a region distant from the center of the frame. A first focusing sensor group of the focusing sensors which are disposed in a first region where light flux passing through a pupil of a lens having an F-number larger than a predetermined F-number such as F2.8 is always used without reference to the F-number of the lens. A second focusing sensor group of focusing sensors which are disposed in a second region where light flux passing through a pupil of a lens having an F-number equal to or smaller than the predetermined F-number and having a higher accuracy for focus detection is used only when the F-number of the lens is equal to or smaller than the predetermined F-number.

Abstract: Where a person is being photographed, for example, both light from the person located at closer range and light from the background located farther away enter the photodetector elements. Where the contrast of the background is high, the rate at which the information from the background contributes to the focus detection becomes larger, which hinders accurate focus detection with regard to the person. In this case, the focus detection device divides a predetermined focus area into smaller areas and detects focus condition in each smaller area.

Abstract: An auto focus detecting device capable of focus detection by a contrast detecting method and a phase-difference detecting method. In accordance with a condition of an object, either one of detecting method is selected, and then an amount of defocus is calculated based on a result obtained by the selected detecting method.