JPH0313628B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an apparatus for extracting characteristics of read characters.

The character recognition device extracts the reading waveform of the magnetic ink characters on the card as a differential waveform and integrates it.
The integral waveform is sampled and held by a sampling pulse at the midpoint of each position where the peak of the differential waveform appears selectively according to the character,
Japanese Patent Laid-Open No. 56-103774 discloses a method for extracting the characteristics of a read character and recognizing the read character by comparing this sampling hold waveform and the above-mentioned integral waveform using the above-mentioned sampling pulse and observing the increase/decrease relationship in the above-mentioned integral waveform. It is known from the publication No. However, in this character recognition device, sampling and comparison are performed in the middle of each position where the peak of the differential waveform selectively appears, but this middle part is where the ink protrudes and the comparison occurs.
This occurs in a position where noise is likely to occur due to dents, blurring, etc., and the integral waveform also fluctuates due to this noise, making it impossible to accurately grasp the relationship between increases and decreases, making it impossible to correctly extract the characteristics of the read characters and making it impossible to recognize the read characters. The character recognition rate was low.

SUMMARY OF THE INVENTION An object of the present invention is to provide a feature extraction device for read characters that avoids areas where noise is likely to occur and monitors increases and decreases in integral output in order to extract features of read characters without error.

The present invention will be described below by way of examples with reference to the drawings.

FIG. 1 shows an example of a character recognition device to which the present invention is applied.

In this example, magnetic ink characters E13B recorded on a medium such as a card such as a check are read and recognized. magnetic ink letters are magnetized. The magnetic head 12 magnetically reads the magnetized characters on the card and outputs a differential waveform thereof. The magnetic ink characters on the card change when the character recording area 42 for one character (in this figure, the character 0 is recorded) is divided into seven equal blocks by dividing lines ~, as shown in Figure 2. The peak of the quantity appears selectively according to each character above the dividing line ~, and the peak of the read signal from the magnetic head 12 selectively appears according to the character at the point corresponding to the dividing line ~. . FIG. 3 is a timing chart when a magnetic ink character "1" is read, and the read signal from the magnetic head 12 has a lot of noise in the middle of the point where peaks selectively appear. This read signal is amplified by an amplifier 13, and then integrated by an integrating circuit 18 consisting of an operational amplifier 14, a capacitor 15, and resistors 16 and 17, resulting in a waveform as shown in FIG. Added to 20. Also, monostable multiviprator (hereinafter abbreviated as monomulti)
21 is triggered at the beginning of the read signal from the magnetic head 12 to produce an output pulse as shown in FIG. 3C having a time width t corresponding to the specified character width.
Here, the magnetic ink characters all have their starting edges on the dividing line. The mono multi 22 is triggered by the rising edge of the output pulse of the mono multi 21 and outputs a pulse with a constant time width, and the mono multi 23 outputs a pulse with a fixed time width.
It is triggered by the falling edge of the second output pulse and the output remains at a low level for a certain period of time. The mono multi 24 is triggered by the rising edge of the output of the mono multi 23 and outputs a pulse with a constant time width, and the mono multi 22 is triggered by the falling edge of this pulse. magnetic head 1
In the read signal from 2, peaks appear selectively in accordance with the magnetic ink characters at points corresponding to the dividing line ~, but if the interval between these points is A, the output pulse width of the monomulti 22 will be 1/4A. Set.
The time width of the low level output of Mono Multi 23 is 2/4A
The output pulse width of the mono multi 24 is set to 1/
It is set to 4A. Therefore, the output of the monomulti 22 becomes as shown in FIG. 3 E, and the output of the monomulti 23 becomes as shown in FIG.
The output of 4 is as shown in FIG. The sampling pulse oscillator 25 generates a sampling pulse as shown in FIG. 3H at the rising edge of the output pulse of the monomulti 23, and the comparison pulse oscillator 26 generates a sampling pulse as shown in FIG. Generates a comparison pulse. The above sampling pulse and comparison pulse are applied to the magnetic head 12.
The peak of the read signal from the signal selectively appears at a point 1/4 A away from the center around the point where the peak selectively appears. Sampling hold circuit 2
0 consists of a switch 28 and a capacitor 29,
The output signal of the integrating circuit 18 is sampled when the switch 28 is turned on by the sampling pulse, and is held by the capacitor 29. The offset circuit 19 is provided to prevent a small potential change in the output signal of the integrating circuit 18 from being judged as a potential change.
2. Diodes 33, 34 and variable resistors 35, 3
6, which corrects the output signal of the integrating circuit 18 upward and downward by a predetermined level. The comparator 37 compares the upwardly corrected output of the offset circuit 19 with the output of the sampling and hold circuit 20, and when the former is larger than the latter, the output becomes "1", and when the former is smaller than the latter, the output becomes "0". A comparator 38 compares the downwardly corrected output of the offset circuit 19 and the output of the sampling hold circuit 20, and when the former is smaller than the latter, the output becomes "1".
and when the former is larger than the latter, the output is “0”
become. The D flip-flops 39 and 40 latch the outputs of the comparators 37 and 38 using the comparison pulses, and therefore the sampling and holding circuit 2
The comparison between the output of 0 and the output of the offset circuit 19 is substantially performed at the timing of generation of the comparison pulse. For this reason, as shown in FIG.
The above-mentioned sampling S and the above-mentioned comparison C are performed at a point 4A away from the point where there is no fluctuation due to noise, and the increase/decrease relationship in the output signal of the integrating circuit 18 is detected, thereby determining the characteristics of the read character. The data is correctly extracted as shown in Figure 1. The identification circuit 41 reads the output data of the D flip-flops 39 and 40 using the pulse from the comparison pulse generator 26 when the output pulse of the monomulti 21 is input, and determines whether each bit is valid or invalid based on the division pattern stored in the internal memory. It recognizes the read characters by comparing them with each character pattern in internal memory.

Note that the above sampling and comparison were performed using the magnetic head 12.
By performing this at both points within 3/8 before and after the point where the peak of the differential waveform selectively appears, it is possible to avoid points where noise is likely to occur and detect increases and decreases in the integral output with high accuracy. However, due to the relationship with noise and accuracy problems due to the interval between the sampling and comparison being too narrow, the sampling and comparison described above are performed at 1/1/2 of the point before and after the point where the peak of the differential waveform from the magnetic head selectively appears. It is best to use 4A.

As described above, according to the present invention, since the increase or decrease in the integral output is checked while avoiding points where noise is likely to occur, the characteristics of the read character can be extracted without error, and as a result, the character recognition rate is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an application example of the present invention, FIG. 2 is a diagram showing a block configuration of magnetic ink characters,
FIG. 3 is a timing chart during one reading recognition of the above application example. 22-24...Monomulti, 25...Sampling pulse oscillator, 26...Comparison pulse oscillator.

Claims (1)

[Claims] 1. The character reading signal is extracted as a differential waveform and integrated, and by comparing this integrated waveform and its sampling hold waveform, the above integral is calculated before and after the point where the peak of the differential waveform selectively appears. In a read character feature extraction device that extracts features of read characters by looking at the increase/decrease relationship in the waveform, a timing signal is generated at a point within half of the interval between adjacent peak points, centering on the peak point in the differential waveform. What is claimed is: 1. A feature extraction device for read characters, comprising: means for generating a character, and performing the sampling and comparison in accordance with the timing signal.