Abstract: An original size sensing method for an apparatus which includes a photoelectric converter for reading an image of an original placed on a platen, and a light source for irradiating the original with light, determines the presence/absence of incidence of ambient light on the basis of an output from the photoelectric converter while the light source is kept off. When ambient light is found to be incident, the method determines the size of an original placed on the platen on the basis of that output from the photoelectric converter, which falls outside the range in which the ambient light is incident, while the light source is kept on.

Abstract: An original size sensing method for an apparatus which includes a photoelectric converter for reading an image of an original placed on a platen, and a light source for irradiating the original with light, determines the presence/absence of incidence of ambient light on the basis of an output from the photoelectric converter while the light source is kept off. When ambient light is found to be incident, the method determines the size of an original placed on the platen on the basis of that output from the photoelectric converter, which falls outside the range in which the ambient light is incident, while the light source is kept on.

Abstract: An original size sensing method for an apparatus which includes a photoelectric converter for reading an image of an original placed on a platen, and a light source for irradiating the original with light, determines the presence/absence of incidence of ambient light on the basis of an output from the photoelectric converter while the light source is kept off. When ambient light is found to be incident, the method determines the size of an original placed on the platen on the basis of that output from the photoelectric converter, which falls outside the range in which the ambient light is incident, while the light source is kept on.

Abstract: An original scanning apparatus includes a reciprocable original scanning optical system, a first driving mechanism having a first motor, a second driving mechanism having a second motor and a clutch for drivingly connecting the first driving mechanism to the optical system after the optical system starts to move by the second driving mechanism in a forward direction. The backward movement of the optical system is provided by the second driving mechanism.

Abstract: An optical assembly for forming an image of the original to be copied on a photosensitive member at a selected magnification, is detachably mounted in a copying apparatus. The optical assembly includes a number of small imaging elements which are arranged in a row or rows in the direction crossing the optical axes of the imaging elements. The copying apparatus is provided with a detector for detecting the imaging magnification of the optical assembly mounted in the copying apparatus. The optical assembly provided with a portion actable on the detector.