JPH0135386B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical character reading device that reduces the rate of misreading.

Conventionally, some optical character reading devices (hereinafter referred to as OCR) have adopted a similarity method as a character recognition method. In this similarity method, characters written on a form are photoelectrically converted, and a similarity calculation is performed between the photoelectrically converted character pattern and a standard character pattern stored in a recognition dictionary prepared in advance. Then, the similarity value of the first candidate sentence with the highest similarity value is greater than or equal to a predetermined value,
In addition, when the difference from the similarity value of the second-ranked complementary character is equal to or greater than a predetermined value, the first-ranked complementary character is output as the answer.

Therefore, with this similarity method, even if the letters are similar in shape, such as lowercase letters such as j and i, which are clearly different in size (width and height),
There were flaws that could lead to misreading.

This invention was made in view of the above circumstances, and it is possible to reduce the misreading rate by checking whether the answer obtained by the similarity method is valid or not based on the relative relationship of the projection value with the preceding and succeeding characters. It is an object of the present invention to provide an optical character reading device that can reduce the number of characters.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an OCR according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a photoelectric conversion unit, which has the function of optically scanning the surface of a form (not shown) on which characters are written and converting reflected light into an analog electrical signal. 2 is a quantization circuit which has a function of converting the analog signal sent from the photoelectric conversion section 1 into a digital signal. Reference numeral 3 denotes a detection circuit which has the function of storing the digital signal sent from the quantization circuit 2, detecting and cutting out the stored character pattern (photoelectrically converted character pattern) into character patterns in units of characters. There is. Reference numeral 4 denotes a normalization circuit, which has a function of normalizing the position of the character pattern, line width, etc., which are cut off from the cutoff circuit 3.
A preprocessing circuit 5 has a function of performing preprocessing such as adjusting the data amount and data format of the character pattern normalized by the normalization circuit 4. 6 is a recognition dictionary in which standard character patterns for reference are stored. Reference numeral 7 denotes a similarity calculation circuit, which calculates the similarity between the character pattern preprocessed by the preprocessing circuit 5 and each standard character pattern by referring to each standard character pattern stored in the recognition dictionary 7. It has a function to calculate similarity value. Reference numeral 8 denotes a projection memory in which the projection of the height and width of each character pattern inspected by the inspection circuit 3 and the position information of the character pattern are stored. Reference numeral 9 is a correction table, which stores height and width correction values for each character, which are set based on the difference in height and width of each two standard character patterns, in accordance with the combination of two standard character patterns. . 10 is a judgment circuit;
The first line of one line sent from the similarity calculation circuit 7
It has a function of checking whether or not the complementary character of the position is appropriate as an answer by referring to the contents stored in the projection memory 8 and the correction table 9 and performing a predetermined calculation.

Next, the operation of the above embodiment will be explained. Characters written on a form (not shown) are photoelectrically converted by the photoelectric converter 1 into character patterns. This photoelectrically converted character pattern is converted into a black and white binary value and quantized character pattern by a quantization circuit 2. This quantized character pattern is processed by the verification circuit 3.
The character pattern is checked character by character. At this time, a projection of the height and width of the cut-out character pattern is taken, and each projection value of the height and width is stored in the projection memory 8 for each cut-out character pattern.
At this time, position information of the character pattern is also stored. On the other hand, the cut-out character pattern is normalized by a normalization circuit 4, such as alignment and correction of line width to make it uniform. The normalized character pattern is subjected to preprocessing in a preprocessing circuit 5. The similarity calculation circuit 7 calculates the similarity of this preprocessed character pattern with each standard character pattern stored in the recognition dictionary 6, and the standard character pattern with the highest similarity value is ranked first. It is sent to the determination circuit 10 as a complementary character. Then, by the same operation as above, the first complementary character is obtained by calculating the similarity for each character pattern in one line, and the projected values of height and width for each character pattern in one line are stored in the projection memory 8. When stored in the determination circuit 1
0 checks whether the first complementary character for each character pattern in a line is appropriate as an answer as follows.

That is, for example, as shown in FIG. 2A, it is assumed that the first complementary character for each character pattern in one line is obtained. Further, as shown in FIG. 2B, corresponding to FIG. 2A, it is assumed that the projection values of the width X and height Y of each character pattern in one line are stored in the projection memory 8. Whether or not the first complementary character a of the first character in a line is appropriate as an answer is determined from the relationship of the projection value with the first complementary character b of the second character. Specifically, the determination circuit 1
0 is a projection value Y a of the height of the first complementary character a of the first character, a projection value _{Y b} of the height of the first complementary character b of the next character, and two characters in advance. Between the characters a and b extracted from the correction table 9 that stores the width correction value XΔ and height correction value YΔ set based on the height difference and width difference of each character from the combination of From the height correction value YΔ _ab ,
If the formula Y _a <Y _b −YΔ _ab is satisfied, it is determined that the first complementary character a of the first character is suitable as the answer. In this case, the width projection values X _a , X _b
As for the width, since the difference in width between characters a and b is small, the width correction value _XΔab is also small, so the projected width value is not checked. Similarly, the second character is checked against the first and third characters. In this way, the first
Regarding the complementary character in the position, a check is performed based on the projection value of the preceding and succeeding characters, and it is determined whether or not each complementary character should be output as an answer.

Note that the projection values of the width and height of the character pattern and the position information stored in the projection memory 8 are stored so that they can be indexed for each first-place candidate or its character code. In addition, the correction values stored in the correction table 9 in advance are such that, taking the JIS-OCR-B font as an example, lowercase English letters such as p, q, and j have a large difference in vertical position compared to other characters. Yes, even considering the permissible vertical variation between characters,
That information is valid. Since such characters require different values depending on the combination of the preceding and following characters, they are stored in the correction table 9 so that they can be indexed by the combination of characters. If it is determined that the check based on the projection value of the complementary character with any of the characters before or after is incorrect, it is rejected and rereading is performed.

Furthermore, in order to find the skew of a character string, quantized character pattern strings are sometimes tracked, but in this case, if the projection center of a period, comma, etc. is set as the character center, the error will be large. It is even more effective if the position information of the character pattern stored in the projection memory 8 is used for correction. In this case, it is necessary to store position information for each character pattern for one line. Further, as analog position information, there is a method of employing a combination of the height and center of gravity of a character pattern, and the distance between each upper edge and lower edge of two adjacent character patterns. Taking the JIS-OCR-B font as an example, if numbers excluding the capital letter "1" and English sentences excluding "I" and "J" are each considered as one group, the storage capacity of position information for skew correction is can be reduced.

In this type of OCR, once a sentence has been recognized, a relative check is performed based on the previous and subsequent projections, so that stable checking can be performed even if the state of the optical system changes.

As described above, according to the present invention, the misreading rate can be reduced by checking whether the answer obtained by the similarity method is valid or not based on the relative relationship of the projection value with the preceding and following characters. It is possible to provide an optical character reading device that can.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of OCR according to an embodiment of the present invention, FIG. 2A is a diagram showing an example of characters recognized as a result of one line in the same embodiment, and FIG. 2B is a diagram showing recognition in FIG. 2A. FIG. 7 is a diagram showing the calculated width and height projection values of the original character pattern for the resultant character. 1...Photoelectric conversion unit, 2...Quantization circuit, 3...
Verification circuit, 4... Normalization circuit, 5... Preprocessing circuit, 6... Recognition dictionary, 7... Similarity calculation circuit, 8
...Projection memory, 9...Correction table, 10...
Judgment circuit.

Claims (1)

[Claims] 1 A photoelectric conversion unit that photoelectrically converts character strings on a form, a quantization circuit that quantizes the photoelectrically converted character pattern string, and a quantized character pattern string that converts the quantized character pattern string into 1
A detection circuit that cuts out character patterns in character units,
A projection memory that stores one line of projection values for each cut-out character pattern, and a similarity calculation circuit that calculates by matching complementary characters of the cut-out character pattern with standard character patterns stored in a dictionary. and a correction table in which projection correction values are stored in advance for each character combination, and the projection value difference between the checked complementary character and the preceding and/or subsequent complementary characters read from the projection memory is calculated. ,
Based on the relationship between the difference between the obtained projection values and the projection correction value corresponding to the combination of the candidate character to be checked and the previous and/or subsequent candidate characters read from the correction table, the complementary character to be checked is determined. What is claimed is: 1. An optical character reading device comprising: a determination circuit for determining whether or not to output as an answer.