Apparatus for the reduction of image intensity variations in a continuously variable reducing copier

DETAILED DESCRIPTION Having thus described our invention, what we claim as new and desire to secure by Letters Patent is: 1.
An electrostatic reducing copying machine for reproducing an object with a reduction in a reproduced image in the range 1:1 to 1:K, where K is less than about 0.
8 and image intensity variation is .
+-.
6% or less throughout said range, comprising: an electrostatic image carrier; means for laying down a latent image thereon including a document support, a source of illumination directed at said document support and lens means for focusing reflected illumination onto said electrostatic image carrier; means for continuously varying the reduction ratio in the range 1:1 to 1:K, where K is less than about 0.
8 or less, wherein the improvement comprises: a single fixed aperture means located between said lens means and said object support for reducing image intensity variations, caused by changes in said reduction ratio, and by non-uniform illumination across said object plane, and correction for lens cos.
sup.
4 losses, to within .
+-.
6%.
2.
The apparatus of claim 1 wherein said single fixed aperture has a compound dogbone shape including a first portion extending from an edge of said aperture which narrows in width to a minimum width and then increases in width.
3.
The apparatus of claim 1 in which said source of illumination provides an illumination profile peaking at a point about 50% of the maximum width document to be copied from a reference edge.
4.
The apparatus of claim 2 in which said single fixed aperture has a width varying from a first width at an extreme edge, to a minimum width approximately in the center of said aperture, to a second width which is not equal to said first width at another extreme edge of said aperture.
5.
The apparatus of claim 4 in which said first width corresponds to a reference edge of a document to be copied and said second width is greater than said first width.
6.
The apparatus of claim 5 in which said width decreases to a first minimum width and then increases slightly to a first intermediate maximum width before decreasing to said minimum width