Position detection device for detecting sheet position, conveyance device, and image formation device

A position detection device for detecting a position of a sheet, comprising:

• a light detection unit configured to detect reflected light or transmitted light from the sheet, and including a plurality of element blocks arranged in a line, each of the plurality of element blocks including a plurality of reading pixels;
• an acquiring unit configured to acquire sheet type information indicating reflection characteristics of a surface of the sheet;
• a first threshold determination unit configured to select a first threshold corresponding to the sheet type information acquired by the acquiring unit, based on a previously determined correspondence relationship between sheet type information of the sheet and thresholds;
• a binarization unit configured to compare signals output by the plurality of reading pixels of each of the plurality of element blocks included in the light detection unit with the first threshold selected by the first threshold determination unit, to binarize the signals;
• a position determination unit configured to specify, as a first lateral edge position of a lateral edge in a lateral direction perpendicular to a conveyance direction of the sheet, a position at which the binary signal output by the binarization unit changes;
• an element selection unit configured to select one of the plurality of element blocks that corresponds to the first lateral edge position determined by the position determination unit, based on a correspondence relationship between positions of the plurality of element blocks and the first lateral edge position determined by the position determination unit;
• and
• a second threshold determination unit configured to determine a second threshold based on signals output from the plurality of reading pixels included in the element block selected by the element selection unit, wherein
• the binarization unit further compares signals output from the plurality of reading pixels included in each of the plurality of element blocks with the second threshold determined by the second threshold determination unit, to binarize the signals, and
• the position determination unit further determines, as a second lateral edge position of the lateral edge of the sheet, a position at which the binary signal output by the binarization unit changes.

A conveyance device for conveying a sheet, comprising:

• a light detection unit configured to detect reflected light or transmitted light from the sheet, and including a plurality of element blocks arranged in a line, each of the plurality of element blocks including a plurality of reading pixels;
• a threshold determination unit configured to determine a threshold based on a signal output from one of the plurality of element blocks that faces a position of a lateral edge of the sheet in a lateral direction perpendicular to a conveyance direction of the sheet;
• a binarization unit configured to compare signals output by the plurality of reading pixels included in each of the plurality of element blocks with the threshold determined by the threshold determination unit, to binarize the signals;
• and
• a position determining unit configured to determine, as the position of the lateral edge, a position at which the binary signal output by the binarization unit changes from a high level to a low level or from a low level to a high level.

An image formation device comprising:

• a conveyance device including a position detection device configured to detect a position of a sheet;
• and
• an image formation unit configured to form an image on the sheet conveyed by the conveyance device, wherein
• the position detection device includes
• a light detection unit configured to detect reflected light or transmitted light from the sheet, and including a plurality of element blocks arranged in a line, each of the plurality of element blocks including a plurality of reading pixels,
• a threshold determination unit configured to determine a threshold based on a signal output from one of the plurality of element blocks that faces a position of a lateral edge of the sheet in a lateral direction perpendicular to a conveyance direction of the sheet,
• a binarization unit configured to compare signals output by the plurality of reading pixels included in each of the plurality of element blocks with the threshold determined by the threshold determination unit, to binarize the signals, and
• a position determining unit configured to determine, as the position of the lateral edge, a position at which the binary signal output by the binarization unit changes.