JPS5465526A - Optical device for copying machine - Google Patents

Abstract

PURPOSE:To copy an original document of any size to the same size regardless of the size of the document by operating a light amount control mechanism which shifts integrally with the lens when the copying multiplication ratio is changed so as to control the light amount given to the lens. CONSTITUTION:String 64 is trained over betwen pulley 60 secured to the base of rotatable shaft 59 of lens support 7 and lens stopping operating unit 63 via intermediate pulleys 61, 62, and two swing links 66, 67 are provided between the tip of the rotatable shaft 59, shiftable shaft 65 below the shaft 59, and the shaft 56. And pulleys 58, 68 of the same diameter are rotatably mounted on the shaft 65, and pulley 69 of the same diameter as that of the pulley is secured to the rotatable shaft 59. Then the spring 70 is trained over pulleys 58, 68, 69. Therefore when stopping control dial 48 is rotated, its rotation force is transmitted to operation unit 63 via each pulley and string to control the predetermined light amount. When the lens shifts to the position of multiplication change, the pulley 68 moves between shafts 56, 65 as its radius. Automatic correction of exposure light amount accompanied by the change of multiplication is done by the mechanism between pulleys 58, 69. Thus the copy of the same size can be obtained at all times.