Compact multibeam laser light source and interleaving raster scan line method for exposing printing plates

An interleaving raster scan line method for imaging printing plates by generating raster points using an array of n laser light sources, which use an imaging optics to image n image points arranged on a line, the n image points being separated by a spatial interval of adjacent points l, comprising the steps of:

• simultaneously generating n image points on a printing plate by a plurality of laser light sources;
• generating a relative motion between the image points and printing plate;
• displacing the image points with a translation component perpendicular to the line of the image points by a first specific amount;
• displacing the n image points in a direction defined by the line of the n image points by a second specific amount;
• repeating the displacement steps, an amount of the second specific displacement being greater than the spatial interval l of adjacent image points.

A print unit comprising at least one device for imaging printing plates, the device including an array of n laser diodes which image n image points, so that one laser diode of the array is allocated to each i-th point, with i being from {1, . . . , n}, the n image points being separated by a spatial interval l between adjacent image points, with a pitch distance p of dots to be imaged by the array, the laser diodes being individually-drivable single stripe laser diodes;

• the spatial interval l between adjacent image points, measured in units of the pitch distance p of the dots, being an integral multiple m of the pitch distance p between the dots;
• wherein the integral multiple m and the number n of image points have no common divisor;
• and
• at least one detector for testing for correct functioning and determining a power output of one or of a plurality of the laser diodes.