Scanning device comprising a sensor assembly including photoelectric conversion elements in a row that detect a rectangular hole to determine a scanning start position

A scanning device, comprising:

• a casing;
• an original document table having a peripheral part being held by the casing, the original document table including an original document placement surface on which an original document is to be placed;
• a sensor assembly movable in a sub-scanning direction to scan the original document placed on the original document table, the sensor assembly including a light source and a photoelectric converter which faces the original document table from an opposite side of the original document placement surface, the photoelectric converter including a plurality of sensor chips, each of the plurality of sensor chips including a photoelectric conversion element row in which a plurality of photoelectric conversion elements are arranged in a main scanning direction, a seam being provided between a position corresponding to a photoelectric conversion element row of a first sensor chip and a position corresponding to another photoelectric conversion element row of a second sensor chip, the first sensor chip being closest to the light source, and the second sensor chip being adjacent to the first sensor chip in the main scanning direction
• where the casing has a facing area facing the peripheral part of the original document table from a side of the original document placement surface,
• wherein a rectangular hole is formed on the facing area, the rectangular hole having edges extending along the main scanning direction and edges extending along the sub-scanning direction, the rectangular hole forming a shadow by light from the light source,
• wherein at least one of the edges extending along the sub-scanning direction located at a position corresponding to a central area of the photoelectric conversion element row with excluding each end thereof,
• wherein the sensor assembly including a light guide elongated in the main scanning direction, the light guide being configured to guide light from the light source in the main scanning direction;
• wherein the light source is located at one side of the light guide in the main scanning direction;
• and
• wherein the rectangular hole is formed at a position corresponding to the photoelectric conversion element row of the first sensor chip closest to the light source.