Abstract:
An improved apparatus and method of recognizing a character is disclosed. The side frame structures of characters or figures are discriminated by left and right margin detectors and corresponding left and right side frame recognition circuits. A final character discrimination circuit synthesized both the results of a conventional character recognition unit and the frame recognition circuits, and permits discrimination between similarly shaped characters.

Description:
This application is a continuation of application Ser. No. 894,075, filed Aug. 5, 1986, now abandoned, which is a continuation of Ser. No. 664,635, Nov. 7, 1984, abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an improved apparatus and method of automatic recognition of a character and, more specifically, of more precise recognition of a character by discriminating the frame-construction of the character to be recognized. 
     The invention is especially suitable for a hand-held optical character reading equipment or its combination with a bar-code reader or the like. 
     DESCRIPTION OF THE PRIOR ART 
     A character or alphanumeric figure (hereafter referred to as a character) is recognized by scanning with an image sensor having a two-dimensional array of photoelectric elements. 
     For example, a method of recognizing characters is disclosed in U.S. Pat. No. 4,180,800 wherein, as illustrated in FIG. 1 herein, characters on a sheet of paper 3 are scanned by a hand-held scanner 1 which is equipped with illuminating lamps 4, an optical lens 5, an image sensor 6 with a two-dimensional array of photoelectric cells, and a converter 7 for converting video output signals into digital signals representing a binary character pattern, as shown in FIG. 2 herein. 
     The character recognition method of U.S. Pat. No. 4,180,800 includes the step of determining the character area of the digitized pattern of the character by a vertical segmentation circuit 9 and a horizontal segmentation circuit 10. For instance, circuit 9 detects that the character &#34;2&#34; in FIG. 2 exists in the cells from line Lj to line Lj+N-1, and similarly circuit 10 determines that the character exists in the columns ranging from B1 to Bi in whole or at least in part. 
     The line features of the lines within the character area are then extracted by circuit 11. The features of the lines are classified and coded for all line segments of the character by a feature classification code. The line feature codes Ci may be compressed into partial feature codes Di, for example, by combining adjacent lines with the same feature classification code Ci into one partial code Di. The identity of the pattern is then determined by recognition circuit 13 by tracing the order of occurrence of partial feature codes Di through a predetermined decision network. 
     One problem to the above-described conventional method of character recognition is that only a limited number of characters can be reliably read, since there are a liited number of line feature criteria which can be discriminated when a practical scanning rate is desired. For example, in the prior method, all numerals plus a limited number of alphabetical characters in Font-B can be recognized. However, the numeral &#34;8&#34; cannot be distinguished from the character &#34;B&#34;, and &#34;K&#34; is recognized to be similar to &#34;X&#34;. Thus, conventional hand-held optical character readers (OCR) can recognize reliably the numerals and only about 10 alphabets. 
     It is possible to provide conventional OCR with additional functions to make it capable of distinguishing more characters, for example, by extracting more precise character line features. However, this results in a higher cost of the equipment due to the need for an increased capacity of read-only memory (ROM) in the recognizing circuit 13 and in the other circuits 11 and 12. 
     Accordingly, an object of the present invention is to eliminate the above-described difficulties which are inherent in the conventional methods of character recognition. More specifically, an object of the invention is to provide an improved apparatus and method of character recognition in which the function of recognizing character-frame construction is provided in order to allow more precise recognition of more characters than in the conventional methods. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an improved apparatus and method of character recognition enable discrimination of more characters by incorporating an additional function for discriminating the structure of the frame of the character. Discrimination of the frame is carried out by means of left and right margin detecting circuits and left and right side frame recognizing circuits. The recognized frame information is processed according to a predetermined decision network. The final character recognition is then obtained by synthesizing the outcome of discriminating both the line features of the character and its frame construction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and further features and advantages of the present invention will be described in detail with reference to the drawings, in which: 
     FIG. 1 is a block diagram illustrating a conventional character recognition device; 
     FIG. 2 is a diagram of a typical binary pattern for the character &#34;2&#34; obtained by an image sensor having a two-dimensional array of photoelectric cells; 
     FIG. 3 is a block diagram of one embodiment of an improved character recognition apparatus according to the present invention; 
     FIG. 4 is a flow diagram illustrating the transitional states for recognizing a frame of a character using the method and apparatus employed in the present invention; 
     FIG. 5 shows a detailed block diagram for a character-frame recognizing circuit in the apparatus of FIG. 3; 
     FIG. 6 is a block diagram of the frame discrimination means; 
     FIG. 7 is a block diagram showing the character synthesis means; and 
     FIG. 8 is a tabular representation of character synthesis. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In accordance with a preferred embodiment of the invention, FIG. 3 depicts a hand-held OCR scanner having similar components as referenced by numerals 1-13 of the conventional scanner described with respect to FIG. 1 above. The functioning of these conventional elements is considered to be known, for example, as disclosed in U.S. Pat. No. 4,180,800. In FIG. 3, left-margin detecting circuit 21 detects the presence of left-margin elements for each line segment of the binary pattern. The output signals Pi from the circuit 21 indicate the specific ones of the photoelectric elements detected in the left margin of the character. 
     In the case of the binary pattern &#34;2&#34; in FIG. 2, for example, the left margin of the pattern segment on the line Lj is detected by the photoelectric element in the column numbered B2. Accordingly, an output signal from circuit 21 for this line Lj is &#34;P2&#34;. As the left-margin detecting circuit 21 receives the signals indicating the character area which is outputted from the vertical segmentation circuit 9 and horizontal segmentation circuit 10, the circuit 21 detects the presence of left-margin segments of the pattern &#34;2&#34; throughout the lines in the corresponding character area. 
     The left-side character-frame recognizing circuit 23 receives the left-margin signals Pi from circuit 21, and recognizes a frame feature for the left side of the pattern. The frame recognition circuitry, which can consist of a ROM (read only memory) and a register, effects frame feature recognition by tracing the ordered sequence of the left-margin signals Pi. A transition flow diagram illustrating the process of recognizing a left-side frame feature of the pattern by circuit 23 is shown in FIG. 4. 
     In the figure, S0, S1, . . . etc. are states of transition in the process of recognizing a left-side character frame feature, and P2, P3, . . . etc. are signals Pi corresponding to the photocells in which left-margin line segments of the binary pattern are detected. For example, a recognition sequence is initiated at S0 and moves to S1 when P2 is inputted indicating a left-margin line segment detected in the photocell located in column B2 of the first line of the two-dimensional array of photocells. In the same manner, when subsequent signals Pi are inputted in the order of P2, P2, P8, P8, P8, P2, P2, then the states of transition follow in the order of S0, S1, S2, S3, S4, and finally lead to S5. As the final recognition result in this state corresponds to a frame feature defined as &#34;  &#34;, the left side frame of the pattern is determined to this frame feature. 
     FIG. 5 illustrates an example of the recognition circuit 23 for recognizing the above-described pattern frame features. The circuit is composed of ROM 30 and a register 31. Both the input signal Pi from the left-margin detector circuit 21 and the prior state output signal of the register 31 are introduced to ROM 30 as address signals, and the corresponding read-out state signal is then set in register 31. For example, in the initial state S0, the contents of register 31 are cleared, and when signal P2 is inputted to ROM 30 as an address signal, the transition state S1 is read out from ROM 30 and stored in register 31. The same procedure is then repeated until the final stage S5 is reached. The other (right) side frame recognition circuit 24 for the right side of the pattern operates in a similar manner as described above. 
     For right side frame recognition, right-margin detecting circuit 22 detects the presence of pattern segments on the lines on the right margin of the character area, and provides output signals Qi indicating the photocells where a right-margin pattern segment of the binary character pattern appears. For the pattern illustrated in FIG. 2, the signal Qi corresponds to the photocell on column Bi-1 on line Lj. Right-side character frame recognizing circuit 24 works similarly to the left-side recognizing circuit 23, by distinguishing the right side frame feature of the character pattern from signals Qi. A character-frame discrimination circuit 25 combines the results obtained from circuits 23 and 24, and thus determines the whole frame construction of the character. 
     Referring to FIG. 6, the circuit 25 consists of a ROM 32 and a register 33. A frame feature code signal Lj from the left-side character-frame recognizing circuit 23 and another frame feature code Rj from the right-side are used as address signals to ROM 32, and the resulting integrated signal Kj is set in register 33. For example, in the case of recognizing the character &#34;8&#34;, a code 02 is allocated when Lj corresponds to the left-side character-frame &#34; &#34;, and another code 04 is assigned for the right-side character-frame &#34;3&#34;. The resulting signal from ROM 32 with an address of 0204 corresponds to &#34; &#34; and the output signal Kj is 03. 
     From the output signals of both the character recognizing circuit 13 and the character-frame discrimination circuit 25, the final recognition result is determined by character discrimination synthesis circuit 26. To illustrate, in the case of distinguishing the characters &#34;8&#34; and &#34;B&#34;, conventional recognizing circuit 13 may output the same results for the two. Tbe output signals from the frame discrimination circuit 25, however, are different, since the left-side feature of the character-frame of &#34;8&#34; is &#34;  &#34;, and the opposite side feature is determined as &#34;3&#34;. On the other hand, the left-side feature of character &#34;B&#34; is determined to be &#34;|&#34;, and the opposite-side feature is determined to be &#34;3&#34;. The whole character frames of &#34;8&#34; and &#34;B&#34; are distinguished by the output Kj of circuit 25 for the respective two frame halves. 
     Referring to FIG. 7, the circuit 26 consists of a ROM 34 and a register 35. An output signal Tj from character recognizing circuit 13 and character-frame discrimination signal Kj are used as addresses to ROM 34, and the output Ch is registered in a register 35. To illustrate, in the case when the output signal from the circuit 13 is 08 corresponding to tbe character recognition results &#34;  &#34;, and the character-frame discrimination signal is 03 corresponding to the recognition results of character-frame discrimination circuit 25, a code 0803 is used as the address signal for ROM 34, and a signal Ch which corresponds to the character &#34;8&#34; is outputted as a final recognized character code. 
     On the other hand, the character &#34;B&#34; is addressed by a code 0804 wherein Tj is 08 and Kj is 04, and ROM 34 provides a final code signal which corresponds to the recognized alphanumeric character &#34;B&#34;. 
     Thus the apparatus and method of character recognition of the present invention enables distinguishing &#34;8&#34; from &#34;B&#34; or &#34;K&#34; from &#34;X&#34; by incorporating the additional functions of frame discrimination circuit 25 and character discrimination synthesis circuit 26 together with the conventional character recognizing functions of a scanner unit. 
     FIG. 8 explains the character synthesis further. RK j  is shown horizontally and LK j  is shown vertically. The points at which the horizontals and the verticals cross correspond to the synthesis results. For example, if LK j  is 00, which is the code for the character &#34;1&#34;, and RK j  is 04, which is the code of the character &#34;3&#34;, the result K j  is the code 04, which represents the character &#34;B&#34;. 
     In the above-described embodiments of the invention, the left and right side margins of a binary character pattern are detected for every line segment of the pattern. In practice, margins can also be detected for every column (top and bottom frames) or for a plurality of lines and/or columns or combinations thereof. It is to be understood that other variations or further modifications may be made such as would be apparent to those skilled in the art without departing from the principles of the invention. All such modifications and variations are intended to be encompassed within the scope of the invention, as defined in the appended claims: