Multi-function detecting device for a document reproduction machine

Abstract

An optical sensing array is adapted to filter incident light so as to generate two output electrical signals from two different portions of the array. The sensing array, which can be a linear CCD array, is assembled with a glass filter overlying the array, the filter being coated with a material which transmits light over a selected wavelength. One portion of the glass filter is uncoated. Thus, a light source incident on the array will activate two separate areas of the array; one underlying the open window and the other underlying the overcoated portion. The results in two different responses over different portions of the wavelength and results in generation of two electrical signals of different levels, representing different detected wavelengths of light. These electrical signals are useful to represent different functions; for example, various characteristics of said background density and size of a document being copied on a xerographic copier.

Dependencies are inferred from the claim text.