Apparatus for measuring the area of image portion of image-bearing member.

摘要

In an apparatus which measures an area factor of an image portion of an image-bearing member (11), such as a printing plate used in an offset press, having image and non-image portions with different reflectivities, a single light source (51) and a single photoelectric conversion element (56) are used for measuring reflected light from the image-bearing member (11) by optically scanning the image-bearing member. An arithmetic operation unit (57) is provided so that the reflected light data are measured on the basis of electrical signals from the photoelectric conversion element (56) each time a light beam moves for a unit distance in the X axis direction of the image-bearing member (11), and the corresponding reflected light data are added in the Y axis direction to obtain area data for each unit region in the X axis direction. In the offset press, an area factor of an image portion for each ink control zone of the press is calculated on the basis of the area data forthe respective unit regions and the quantity of ink for each ink control zone is thus controlled.