(57) This invention relates to a sheet sensor comprising a light source (62) coupled to
an optical waveguide (60) arranged to direct light at the path of the sheet (54).
At least a second waveguide is arranged to receive light after transmission through,
or reflection from, the light. A transducer converts the received light into an electrical
signal which indicates the presence or the absence of a sheet in the path. Both the
light source and the «transmission» waveguide are secured to each other and to a common
substrate (64).
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