International Business Machines Corporation

Megumi Hasegawa

Shigeki Asada

A document scan apparatus in which the position of a document support table relative to an optical system is detected during the relative movement between the document support platen and the optical system. A reference position marker is mounted on the document support table which directly reflects a light from a document illumination light source into an optical sensor array or a CCD sensor array through a mirror and a lens for causing the CCD sensor array to operate in a saturated range to generate a higher output signal level than an expected highest signal level of the CCD sensor array in the document scan operation; and by setting a threshold level of a comparator circuit to a high level which is exceeded by the higher output signal level of the CCD sensor array. The reference position marker is positioned within the field of view of the CCD sensor array for sensing the image of the document, so that the CCD sensor array sensing the document image also senses the reference position marker.

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Fujisawa, Japan

Megumi Hasegawa