DETECTOR FOR STATE OF PLATE

A machine for scanning printing plates to determine the ratio of "printing" to "non-printing" area for pre-adjustment of the ink dosing elements of a printing machine has an array of electronic photo-sensors, each sensor being disposed in a channel having low-reflection chambers which permit sharp delimination of resolution elements on the printing plate and ensure high definition scanning of different types of printing plates under practical conditions. Preferably the diaphragms dividing the channel into chambers have greater spacing at greater distances from the element sensed on the printing plate. To accommodate printing plates of different materials, means are provided for selecting the wave length of the light source. To prevent measurement error due to changes in the distance from the printing plate to the light source and sensor array, the photosensor array is preferably directed or aimed 60 DEG to 45 DEG with respect to the normal vector of the printing plate, and the light source is in the same quadrant as the photo-sensor array at an angle of 0 DEG to 45 DEG with respect to the normal vector. Automatic calibration, automatic printing plate size determination, automatic sensing of identification information engraved on the printing plate, and a stairstep scan to increase the scanning rate are provided by suitable procedures executed by a microcomputer controlling the scanning process and analyzing, adjusting, and interpreting data received from the sensor array.