Method and device for focusing an image of an original onto an image surface of a camera tube or the like

摘要

A method for focusing an image of an original of arbitrary size, or a portion thereof, onto an image surface (target) of predetermined position and size using an objective lens, the image surface being scannable by means of a camera tube, a two-dimensional CCD array or a one-dimensional CCD array, comprises the procedural steps of using a varifocal lens (4) as the objective lens, of bringing a focusing mask (10) of the predetermined size of the image surface (1) to the position of the latter and illuminating it in the direction of the varifocal lens (4), of adjusting the varifocal lens (4) and/or a stage (5) for the original (2) until the mask image is brought into coincidence with the original (2) or the portion thereof whose image is to be formed, and the mask image is formed sharply on the original (2), and of then removing the focusing mask (10) and its illumination arrangement (11) from the optical path of the varifocal lens (4) and bringing the camera tube, the two-dimensional CCD array or the one-dimensional CCD array for scanning the image surface (1) into the objective optical path. It is thereby possible to produce and scan pictures of uniform size and position from originals of various size and to be able to focus the objective lens for each individual original. <IMAGE>