Optical image scanning apparatus detecting sheet size and displacement

An image scanning apparatus scanning an image formed on an original sheet placed on a scan table, original sheet information including size and displacement information of said original sheet placed on said scan table being obtained before scanning of said image is performed, said image scanning apparatus comprising:

• beam emitting means for emitting a coherent first beam;
• deflecting means for deflecting said first beam so that said first beam traces a predetermined scan line on a plane including a surface of said original sheet, said predetermined scan line being formed on said plane so that a length of a beam path from a beam originating point of said deflecting means to any point on said predetermined scan line is uniform, and an incident angle of said first beam at any point on said surface of said original sheet is uniform;
• beam sensing means for sensing an intensity of a second beam generated by reflection of said first beam at said surface of said original sheet, said second beam being input to said sensing means via said deflecting means;
• said original sheet information being obtained in accordance with a detection of a sharp change in said intensity of said second beam received by said sensing means with reference to a scanning position of said first beam;
• and
• wherein said predetermined scan line forms at least part of a circle having a center which corresponds to a beam originating point of said deflecting means when said circle is viewed in a direction perpendicular to said plane.

An image scanning apparatus scanning an image formed on an original sheet placed on a scan table, original sheet information including size and displacement information of said original sheet placed on said scan table being obtained before scanning of said image is performed, said image scanning apparatus comprising:

• beam emitting means for emitting a coherent first beam;
• deflecting means for deflecting said first beam in a direction parallel to a plane including a surface of said original sheet placed on said scan table;
• direction changing means for changing said first beam deflected by said parallel deflecting means to a direction perpendicular to said plane so that said first beam is projected onto said original sheet in the direction perpendicular to said surface of said original sheet;
• and
• beam sensing means for sensing an intensity of a second beam generated by reflection of said first beam at said surface of said original sheet, said second beam being input to said sensing means via said deflecting means;
• said original sheet information being obtained in accordance with a detection of a sharp change in said intensity of said second beam received by said sensing means with reference to a scanning position of said first beam.