Method and apparatus for detecting the profile and feeding state of paper sheets

A method for detecting the dimensions of a papr sheet, comprising the steps of:

• conveying at least one sheet of paper in a feeding direction along a conveyance path;
• directing light toward said sheet being conveyed;
• optically scanning the light directed toward said sheet by said directing step which passes across said path along a line perpendicular to the feeding direction of said conveyed sheet, said line including at least first and second distinct view field regions separated from one another by the center of said path;
• producing, for said scan, a value of the dimension a conveyed sheet projects into each of said first and second regions;
• repeating said scanning and producing steps a plurality of times as said sheet is conveyed along said path by said conveying step;
• summing, for each said scan, the values obtained for said at least first and second regions with a predetermined constant value to produce a sequence of width values W.sub.1, W.sub.2, W.sub.3 . . . W.sub.n representing the widths of said conveyed paper sheet at a corresponding plurality of longitudinal positions along said sheet;
• selecting the width values W.sub.i from said sequence (i=1 through n) falling within the range W.sub.s -.DELTA.W.ltoreq.W.sub.i .ltoreq.W.sub.s +.DELTA.W, where W.sub.s is a predetermined nominal width value of said paper sheet and .DELTA.W is a present allowable deviation of the width of said paper sheet from said nominal width value W.sub.s ;
• computing the average width value of said sheet from said selected values;
• and
• comparing said average width value with a reference width value.

A method for detecting the dimensions of an optically opaque sheet comprising the steps of:

• (1) conveying an opaque sheet in a feeding direction along a conveyance path;
• (2) directing light from a first side of said conveyance path toward said path and onto said sheet being conveyed by said conveying step (1);
• (3) sensing the light which passes through said path to a second side of said path opposite said first side and which falls upon a line fixedly oriented with respect to said path perpendicular to said feeding direction and substantially parallel to said sheet being conveyed;
• (4) producing values representing the lengths WW.sub.1 and WW.sub.3 of portions of first and second discrete segments of said line which are illuminated by said sensed light, said first and second segments being spaced apart by a predetermined space WW.sub.2, the center of said sheet being included in said space WW.sub.2.
• (5) storing the length values produced by said detecting step (4);
• (6) repeating steps (3)-(5) a plurality n times as said sheet is conveyed by said conveying step (1) to thereby produce values measure representing said lengths WW1 and WW3 at a plurality of longitudinal positions 1-n along said sheet;
• (7) calculating the values representing the widths from W.sub.1 to W.sub.n of said sheet at said plurality of longitudinal positions from 1 to n from the values stored by said storing step (5);
• (8) selecting, from said values representing widths from W.sub.1 to W.sub.n calculated by said calculating step (7), those values which fall within a predetermined range about a predetermined nominal expected width value of said sheet;
• and
• (9) calculating the average of the width values selected by said selecting step (9).