Abstract: A method and system for digitally reproducing an image on a printing plate that includes enhancing gray levels so that plate may be imaged at lower resolutions and therefore higher speed. An image is scanned and a two dimensional array of optical density values. A comparison is made with a screen cell array having a repetitive pattern of a plurality of different screen cells. Each screen cells includes screen comparison values which when arranged in a sequence of increasing values are interleaved with values in a similarly arranged sequence of values from one of the different screen cells of the screen cell array. Pixel comparisons generate a binary value which is used to selectively operate a laser beam to expose microdots on a printing plate.

Abstract: A vacuum drum apparatus on which a mask is mounted having a resilient surface and an array of holes suitable for a substrate of a given size. The drum is a circular cylinder perforated with an array of holes. A hollow chamber within the drum is connected to a controlled pressure source for providing a vacuum. The mask may be magnetically attracted about the outer surface of the drum. Thus, the mask may be made of a flexible ferromagnetic sheet. The mask is preferably elastomeric and may include an inextensible layer.