Opaquing method and apparatus thereof

Abstract

In the negative form of lith type film or photographic printing paper, the ground part is light-untransmissible and image part (letter, pattern) is light-transmissible. Apart from them, pinholes and stains also constitute light-transmissible areas. Although the light-transmissible areas of letter and pattern are necessary, the light-transmissible areas of pinhole and stain are unnecessary. Thus, the unnecessary light-transmissible areas must be distinguished from the necessary light-transmissible areas, and an opaque layer must be provided on the unnecessary areas to make them opaque. Generally, however, the unnecessary light-transmissible areas are minute and many in number, so that their detection and opaquing is a very laborious work. Thus, according to the opaquing method of the present invention, only the necessary light-transmissible area is detected and the other light-transmissible areas are regarded as unnecessary and the latter are stopped out. Otherwise, unnecessary light-transmissible areas are detected, and they are stopped out. The opaquing apparatus of the invention is equipped with a means for exposing a lith type film or a photographic printing paper to light, a means for detecting necessary light-transmissible area, and a means for providing an opaque layer on the unnecessary light-transmissible areas detected by the detecting means.