Abstract: In a character imaging system, a selected one of a plurality of different characters (letters, numerals, symbols etc.) arrayed as windows in an otherwise opaque mask, is projected optically onto a selected location on a working surface. In this manner, laser light can be used to burn an impression into a workpiece, with successive characters spelling out words and sentences. Alternatively, the system can be used to project non-coherent light onto photographic film or onto a screen. The improvement in this type of system provided by the invention resides in the avoidance of a need to move the mask, or the working surface, or the final lens that projects the light beam onto such surface. And yet the improved system nevertheless enables sequential selection of different characters in the mask, as necessary to build up words and sentences on the working surface.

Abstract: A gas laser includes a pair of subsidiary electrodes to form a sharpening gap. These subsidiary electrodes are located within the envelope of the laser so as to be exposed to the same gas or mixture of gases that flow between the main electrodes and support the main lasing action. The efficiency of the laser and the lifetime of the electrodes of the sharpening gap are thereby improved, together with other advantages.