Abstract: A rotatable image-mounting drum for use in a scanner or plotter. The drum has an end for permitting the releasable attachment of the drum to the scanner's or plotter's supporting and turning means. The drum's image-mounting surface and the drum's attachment end are preferably made of the same material, preferably acrylic. The attachment end of the drum includes a disk at the end of the drum, which has an opening or openings passing from its outer face to its inner face. The other end of the drum preferably is not attached directly to the rest of the scanner. The plotter's or scanner's mechanism for releasably attaching the rotatable drum includes a drum mount rotatable by a motor. A clasp stem, passing through a drum-mount opening, has a clasp finger rigidly attached thereto. A cam surface, having a varying elevation, can be rotated so as to push the cam stem through the drum-mount opening. A spring urges the stem against the cam surface.

Abstract: A system that permits the plotting of any combination of several colors in one pass. Three differently colored light sources are provided, and thus one, two or three colors may be plotted at the same time. An apparatus is provided for causing relative movement between the scanning head and the substrate along each of the two axes of the substrate. Preferably, the first axis is disposed circumferentially about a cylinder, on which the substrate is situated, the cylinder having a central axis, and the second axis is disposed approximately parallel to the central axis. The system includes deflection means, preferably acousto-optical modulators, for deflecting along a path a portion of each beam of light by an amount dependent upon the frequency of a signal that is present at the deflection means' input.

Abstract: A vacuum drum apparatus on which a mask is mounted having a resilient surface and a plurality of holes suitable for a substrate of a given size. The vacuum drum apparatus is balanced for rotation at high speeds by attaching a counterweight to the mask. The drum is a circular cylinder perforated with an array of holes. The drum has flat surfaces on its outer surface that are used to mount the mask and the substrate on the drum. 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 may also be staged on the drum with other mechanical type entanglements. The mask is preferably elastomeric and may include an inextensible layer.

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.

Abstract: A spread spectrum digital screening mask and a method and system for digital screening a continuous tone image with the spread spectrum digital screening mask. The mask is characterized in the frequency domain by a function in magnitude independent of angle within a band of frequencies between a minimum frequency and a maximum frequency. The mask may be further characterized by its thresholded binary planes at each of a plurality of predetermined threshold values. The binary planes are characterized in frequency domain by magnitudes primarily distributed within the band of frequencies. For each binary plane, the number of pixels having one of the binary values divided by the total number of pixels in the binary plane equals a fraction determined by the predetermined threshold value of the binary plane divided by the maximum threshold value.