Patent ID: 7992868

Claim:
An image forming apparatus, comprising: a feeding mechanism for feeding a sheet on a feeding path at a prescribed feeding speed; one or more light emitting sources for emitting light onto said feeding path; a plurality of light receiving elements arranged on a side opposite to a side on which said light emitting source is provided, with said feeding path being interposed therebetween, linearly at a defined interval from an upstream side to a downstream side in a feeding direction in said feeding mechanism, and respectively outputting signals according to amounts of received light; an information storage device including buffers respectively corresponding to said plurality of light receiving elements, and a buffer other than those; and a computation device for (i) performing computation on a plurality of data obtained from said signals respectively from said plurality of light receiving elements at a defined computation cycle, and obtaining computation results respectively corresponding to said plurality of data, (ii) storing said computation results in the buffers according to corresponding said light receiving elements, in said information storage device, and (iii) detecting a position of an edge portion of the sheet being fed on said feeding path based on a characteristic of a data series formed of entire said computation results by arranging said respective stored computation results according to an arrangement of corresponding said light receiving elements, wherein said computation is processing that shifts previous computation results respectively stored in said buffers to the buffers corresponding to the light receiving elements adjacent to corresponding said light receiving elements in said feeding direction in said arrangement, adds or subtracts the shifted computation results to or from the data obtained from said signals from said light receiving elements corresponding to the buffers receiving the shifted computation results, and thereby obtains new computation results, at each said computation cycle.