Aperture plate for an exposure head for use in a picture scanning reproducer

Claim 1

An exposure head of a picture scanning reproducer which traces scanning lines on a recording medium, comprising, an intensity modulated light source element, a condenser lens element, an aperture plate element having an aperture therethrough, and a focusing lens element, said elements being arranged substantially co-axially in series and adapted to be positioned relative to the recording medium such that a light beam directed from said light source through said aperture is focused upon the recording medium, said aperture having a shape delimited by: an edge leading with respect to the scanning direction and an edge trailing with respect to the scanning direction which are parallel straight lines in the feed direction perpendicular to the scanning direction; and end edges joining the ends of these leading and trailing edges, said end edges being curves oppositely and symmetrically disposed to one another with respect to the scan direction, and each of said end edges being composed of first and second lines which start from a mutually defined cusp and open up away from one another in the direction away from the cusp so that the angle between the tangents to them increases, the farther away from the cusp whereby the exposure distribution in the feed direction when each scanning line is exposed defines exponentially shaped curves in both of its ends corresponding to the exponentially shaped curves of the aperture to obtain a uniform concentration value distribution in the feed direction due to the overlapping of the exponentially shaped curves on the recording medium.