Variable magnification electrostatic copying machine

An electrostatic copying machine including a platen for supporting an original document, a photoconductive member, a variable magnification optical means for focussing a light image of the document onto the photoconductive member to form an electrostatic image, developing means for developing the electrostatic image to form a toner image, support means for supporting a copy sheet and transfer means for moving the copy sheet from the support means into toner image transferring engagement with the photoconductive member, characterized by comprising:

• sensor means for sensing a vertical length and a horizontal length of the document on the platen;
• and
• computing means for comparing the vertical and horizontal lengths of the document with vertical and horizontal lengths of the copy sheet and adjusting a reduction ratio of the optical means to a value such that a maximum length of the light image of the document is substantially equal to a corresponding one of the vertical and horizontal lengths of the copy sheet;
• the optical means comprising rotation means for selectively rotating an optical axis of the light image between a first position in which a vertical length of the light image corresponding to the vertical length of the document is parallel to the vertical length of the copy sheet and a horizontal length of the light image corresponding to the horizontal length of the document is parallel to the horizontal length of the copy sheet;
• and a second position in which the vertical length of the light image is perpendicular to the vertical length of the copy sheet and the horizontal length of the light image is perpendicular to the horizontal length of the copy sheet;
• the computing means comprising means for, when the rotation means is in the first position, dividing the vertical length of the document by the vertical length of the copy sheet to obtain a first ratio, dividing the horizontal length of the document by the horizontal length of the copy sheet to obtain a second ratio, comparing the first ratio with the second ratio and adjusting the reduction ratio of the optical means to be substantially equal to a largest one of the first and second ratios;
• and when the rotation means is in the second position, dividing the vertical length of the document by the horizontal length of the copy sheet to obtain a third ratio, dividing the horizontal length of the document by the vertical length of the copy sheet to obtain a fourth ratio, comparing the third ratio with the fourth ratio and adjusting the reduction ratio of the optical means to be substantially equal to a largest one of the third and fourth ratios.