Photodiode transmissive media sensor for aligning media

In a media transporter in which media having opposed faces is transported along a path of a track on said media, a media position alignment system for determining the position of the media relative to reference points thereof, comprising:

• (a) a light sensor having a light-sensitive surface facing one face of the media in at least approximate registration with said track, said light-sensitive surface comprising plural sections, said sensor producing plural signals at an output thereof proportional to the intensity of light impinging on respective ones of said plural sections of said light-sensitive surface;
• (b) a spatially varying pattern forming said track and including,
• (b1) an elongated center stripe in parallel alignment with the path in which said media is moved, said stripe having a width less than the width of a square portion comprising said plural sections of said light-sensitive surface, and,
• (b2) a series of spaced squares centered along said center stripe and extending beyond the width of said stripe wherein each of said squares is of generally the same orientation and approximate size as the square portion comprising the plural sections of said light-sensitive surface, and wherein spacing between adjacent ones of said squares is uniform and is about equal to the length of the square comprising the plural sections of said light-sensitive surface;
• (c) a light source directing a beam of light through the opposite face of the media onto said light-sensitive surface, whereby said plural signals vary as a function of said spatially varying pattern of said track as said media is transported along the path of said track;
• and
• (d) signal detection and logic means for converting said signals to representations of position of said media.