Abstract: A finder system including a first optical system and a second optical system apart from the first optical system by a certain base length. Based on an object distance obtained with use of an active or passive distance measuring device, degree of coincidence of images respectively formed by the first and second optical system and superimposed is varied so that superimposed images of an object that is located at the detected object distance coincide.

Abstract: A focus detecting apparatus includes a focus detecting device which forms an image through a telephotographic system, onto a line sensor, and which detects a focus state of the telephotographic system based on an output from a predetermined portion of the line sensor. An assigning device which assigns the pixels to be used in detecting the focusing state in the case where the actual center of the line sensor deviates from the reference position of the telephotographic system.

Abstract: An automatic focusing apparatus including a focus detecting device which detects a defocus amount of image optical system, a focusing device which focalizes based on the defocus amount calculated by the focus detecting device. An adjustment device which adjusts said defocus amount calculated by said focus detecting device by an adjustment value.

Abstract: An optical pick-up for reading data in the data recording surface of an optical data recording material by collecting light from a light source by means of an objective lens, and shining reflection light from the data recording surface onto a light receiving element through the objective lens, the optical pick-up being adapted to read data in the data recording surface of first and second optical data recording materials wherein the thickness of a protective substrate is different from each other, wherein the objective lens is so determined that the aberration is corrected in response to the thickness of the protective substrate of the first optical data recording material, and in reading data in the data recording surface of the second optical data recording material which has a thickness different from that of the first optical data recording material, the object.image distance is adjustable so as to adjust the aberration.