Character reader having optimum quantization level

Claim 2

A character reader which comprises: a photoelectric conversion device disposed to optically scan the surface of a record carrier bearing an original character marking to be scanned in succession in at least one of a horizontal and vertical direction so as to optically convert the markings on elemental areas of said surface into corresponding video signals; a quantizer receiving video signals from said photoelectric conversion device to quantize said video signals received from said photoelectric conversion device at a threshold voltage level for each of the elemental areas, said elemental areas forming a matrix of rows and columns, so as to generate quantized pattern signals comprised of at least binary logical digits ''''1'''' and ''''0;'''' a quantized pattern storing device coupled to said quantizer to temporarily store quantized pattern signals from said quantizer; and a quantization level responsive apparatus including: an average character stroke width calculating device coupled to said quantizer and arranged to calculate the average stroke width of the orginal character on the record carrier in response to changes in signals corresponding to at least four adjacent elemental areas in the matrix signals successively supplied from said quantizer; a character block number calculating device coupled to said quantizer and arranged to determine the block number of the original character on the record carrier in response to changes in signals corresponding to at least four adjacent elemental areas in the matrix signals successively supplied from said quantizer; a quantizatIon level evaluating circuit coupled to both of said calculating devices and responsive to the outputs of both of said calculating devices to distinguish whether or not the quantizer conducted quantization at a proper level; a gate circuit coupled to said quantized pattern storing device and operated only when the result of determination by said evaluating circuit corresponds to the optimum level of quantization conducted by the quantizer; and a character recognition circuit connected to the output of said gate circuit so as to effect the actual reading of the original character in response to the quantized pattern appearing at the output of said gate circuit.

Claim 3

A character reader according to claim 1 wherein the threshold quantization level of said quantizer is controllable, and, wherein said quantization level evaluating circuit is arranged to produce an output signal when the threshold level is not at its optimum level, said output signal being fed to the quantizer to alter the quantization level of said quantizer to an optimum level.

Claim 4

A character reader according to claim 1 including a plurality of quantizers, each provided with: a quantized pattern storing device, an average character stroke width calculating device, a character block number calculating device, a quantization level evaluating circuit and a gate circuit, said quantizers being arranged to quantize the video signals from the photoelectric conversion device at different levels, the actual reading of a character being effected by reading the contents of the quantized pattern storing device stored with quantized pattern signals from that quantizer whose quantization was conducted at the optimum level, as determined by the quantization level evaluating circuits.

Claim 5

A character reader according to claim 1 wherein said average character stroke width calculating device comprises shift registers successively supplied with quantized pattern signals from said quantizer and having a bit arrangement corresponding to the arrangement of elemental areas, each shift register having a capacity corresponding to at least two elemental areas of an original character on the record carrier which are arranged in the scanning direction; a 2 X 2 bits pattern recognizing circuit successively supplied with quantized pattern signals corresponding to four adjacent elemental areas in two adjacent rows and two adjacent columns in respect of a character, three different cases in respect of a quantized pattern existing, the first case being that of the quantized pattern signals representing two adjacent bits in a row or column of said 2 X 2 bits all consists of ''''1'''' or all consist of ''''0,'''' the second case being that a quantized pattern signal representing any one only of said 2 X 2 bits consists of ''''1'''' or ''''0'''' and the third case being that quantized pattern signals representing both of two slantwise bits of said 2 X 2 bits consist of ''''1'''' or both consist of ''''0;'''' three counters for counting signals from the first 2 X 2 bits pattern recognizing circuit corresponding to the three cases respectively which represent a unit length approximating that of the original character stroke; a further counter for counting quantized pattern signals consisting of ''''1'''' from the quantizer; and an arithmetic operation circuit which, upon completion of scanning of the original character by the photoelectric conversion device, calculates the following value:

Claim 6

A character reader according to claim 1 wherein said photoelectric conversion device scans said original character in the horizontal direction.

Claim 7

A character reader according to claim 1 wherein the character block number calculating device comprises two first shift registers successively supplied with quantized pattern signals from the quantizer and having a bit arrangement corresponding to the arrangement of elemental areas, each register hAving a capacity corresponding to at least two elemental areas of an original character on a record carrier arranged in the scanning direction; a loop filling circuit successively supplied with quantized 2 X 2 bits pattern signals representing two adjacent bits at the forward end of each of said shift registers, said circuit being brought to a set state when there are detected quantized pattern signals corresponding to the forward end of a loop included in the original character, and being brought to a reset state when there are detected quantized pattern signals corresponding to the rear end of said loop; a second shift register wherein, when the loop filling circuit is in a set state, the first bit at the forward end of said second register is supplied with quantized pattern signals consisting of ''''1,'''' and the second and subsequent bits of said second register are supplied in turn with quantized signals consisting of ''''1'''' synchronously with the timing of quantization by the quantizer until the loop filling circuit is brought back to a reset state, and upon resetting of the loop filling circuit, the contents stored therein are cleared by being transferred to one of the first registers; a 2 X 2 bits pattern recognizing circuit successively supplied after the filling of the loop with quantized pattern signals representing four bits at the respective two rear ends of the first shift registers so as separately to detect quantized pattern signals denoting three different angular displacements of the unit length of a quantized character pattern approximating that the original character outline associated with three different cases: the first case being that a quantized pattern signal representing any one only of said 2 X 2 bits consists of ''''1,'''' the second case being that a quantized pattern signal representing any one only of said 2 X 2 bits consists of ''''0'''' and the third case being that quantized pattern signals representing two slantwise bits of said 2 X 2 bits both consist of ''''1'''' or both consist of ''''0;'''' and a reversible counter whose first bit at the rear end is supplied with an output 1 corresponding to the condition of said first case and an output -1 corresponding to the condition of said second case and whose second bit at the rear end is supplied with an output -2 corresponding to the condition of said third case, such that upon completion of the scanning of the original character by the photoelectric conversion device, the number of blocks of said character is counted according to the result of calculation conducted by the reversible counter.

Claim 8

A character reader according to claim 4 wherein the 2 X 2 bits pattern recognizing circuit comprises a plurality of AND gates each having four input terminals which are supplied with the corresponding 2 X 2 bits quantized pattern signals; and three OR gates which are supplied in common with outputs from the AND gates corresponding to those of the 2 X 2 bits quantized patterns involved in each of the aforesaid three cases which may be designated by the same numerical value.

Claim 9

A character reader according to claim 6 wherein the 2 X 2 bits pattern recognizing circuit comprises a plurality of AND gates each having four input terminals which are supplied with the corresponding 2 X 2 bits quantized pattern signals; and three OR gates which are supplied in common with outputs from the AND gates corresponding to those of the 2 X 2 bits quantized patterns involved in each of the aforesaid three cases which may be designated by the same numeral value.

Claim 10

A character reader according to claim 6 wherein the character block number calculating device further comprises two third shift registers provided with a 2 X 2 bits pattern recognizing circuit and a further reversible counter which is similar to the first mentioned reversible countEr, and which is connected to the third shift registers and calculates a value (number of blocks-number of loops) in accordance with the angular displacements of the unit length of the outer and inner outlines of the original character, and further including means for calculating the number of loops included in said character by subtracting the aforementioned value from the number of blocks calculated by the first-mentioned reversible counter.