JPS589984B2 - Mojiyomitrisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a character reading device, and particularly to a character reading device that is effective when the character surface is movable in two directions and the relative speed between the character surface and the observation system is variable. .

In conventional character reading devices, when reading characters optically using a one-dimensional image sensor as a light-receiving element, as shown in FIG. By irradiating it, the light reflected from each part of the character surface creates a one-dimensional image depending on the degree of reflectance.
An image is formed on the sensor 3 by an optical system.

The one-dimensional image sensor 3 converts this image into an electrical signal and transmits it to the next processing circuit.

The one-dimensional image sensor 3 is composed of a number of elements having sufficient resolution to decode character images, and is arranged perpendicularly to the direction of movement of the optical image.

Now, the number of elements of the one-dimensional image sensor 3 is n,
- If the number of scans of this one-dimensional image sensor 3 is M while the optical image for a character passes through the above-mentioned -dimensional image sensor, then the number of constituent meshes for a -character is n×M
It is.

This is transferred to the register of the processing circuit, and scanning of one character is completed.

When the relative speed of the character direction and the observation system that reads it is constant, and the size of the characters is the same, the number of meshes that constitute the above-mentioned characters will be a constant value of n × M, and the character pattern will always be constant. If the relative speed of the three character planes that can be obtained and the observation system that reads them is not constant, then the number of scans of the one-dimensional image sensor while the optical image for the characters passes through the one-dimensional image sensor is M M' is different from .

Therefore, the number of constituent meshes for the - character is nXM', and the character pattern obtained varies in various ways due to the change in the relative speed.

In this way, although the characters are the same, the reception patterns vary in various ways, which puts a heavy burden on subsequent processing circuits.

In another method, an extremely small spot light source is created on the CRTlIfi and projected onto the character surface through a lens system, and the reflection from the character portion is detected by a photo multiplier.

Therefore, if the spot light source is moved onto the CRT surface, the character surface is scanned, and a time-series output signal is obtained from the photo multiplier.

In this way, in conventional character reading devices, either the relative speed between the character surface and the observation system is constant as in the former case, or the relative speed between the character surface and the observation system is constant as in the latter case, the - character is regarded as a surface and the relative speed is fixed until the scanning of one character is completed. In most cases, the letters were kept stationary.

However, as the range of applications for character reading devices expands, a system that allows the relative speed between the character surface and the observation system (light receiver) to be variable becomes important.

For example, when observing the vehicle number at the entrance/exit of a freight car,
The moving direction is not only one direction but two directions, and the passing speed is not constant.

To read this using conventional methods, it is necessary to read only one direction, or to detect the direction by some other method and switch the processing circuitry based on the result, or to detect the speed by another method. there were.

In order to eliminate such drawbacks, the present invention provides preprocessing to detect the moving direction and relative speed, and to detect the moving direction and the relative speed of the character even when the relative speed between the character surface and the observation system changes and the moving direction is not constant. The objective is to efficiently cut out the character patterns obtained from the observation system, to always keep the character pattern in a constant shape, and to simplify the character recognition circuit in the subsequent stage.Two one-dimensional image sensors are arranged in parallel. , one image sensor detects a character part, the other image sensor obtains a character pattern, and one image sensor sends information about the number of scans used for half a sentence to the other image sensor. , the other image sensor has a function of making the scanning period variable or the data compression ratio in preprocessing variable depending on the information, and that the two image sensors each have a function of independently operating. , when the two image sensors detect the moving direction of the character surface or when a direction signal is received from the direction detecting means, the image sensor is switched to operate by switching to one of the image sensors. .

Hereinafter, the present invention will be explained in detail with reference to FIGS. 2 to 5.

FIG. 2 is a block diagram showing part of the light receiving section and the processing section.

In Fig. 2, 3 is a light receiving section, 4 and 5 are one-dimensional image sensors, 6 is a switching circuit, 7 is a character extraction circuit, 8 is a character feature extraction circuit, 9 is a character identification circuit, and 10 is a character recognition circuit. a circuit that detects the running direction and determines the state of the switching circuit 6;
11 is an image sensor driving circuit.

The two sensors 4 and 5 are both identical self-scanning image sensors, and are arranged at appropriate intervals as shown in FIG.

Since the moving direction of the character direction is not constant, it cannot be determined in advance which sensor 4 or 5 will detect the character first.

The direction detection section 10 detects this.

The direction detection unit 10 detects the running direction of the character surface using a proximity switch or two photoelectric switches, and sends a moving direction signal to the switching circuit 6 to determine the state of the switching circuit 6. It is determined whether the image sensors 4 and 5 receive light first.

If the image sensor 4 receives light first, the switching circuit 6 sends the output of the sensor 4 to the character cutting circuit 7, and then sends the output of the sensor 5 to the character feature extraction circuit 8.

In the image sensor 4, as shown in FIG. 4a,
When the character "2" is scanned at the a and mouth positions, an output Vout as shown in FIG. 4 is obtained.

When these output signals are summed for the same position of the image sensor 4, that is, the same bit numbers 1 to n, when one character has been scanned, the sum result is shown in the shaded area in Figure 5. It will be done.

The character cutting circuit 7 forms a horizontal histogram as shown in FIG. 5 based on the signal sent from the image sensor 4, and thereby cuts out the character in the vertical (height) direction.

Furthermore, by counting the number of scans from when a character is first detected until the character passes, the moving speed of the character can be determined indirectly.

Each time the character cutting circuit 7 finishes scanning one character, it sends the number of scans spent on one character to the image sensor drive circuit 11 as a scan number signal.

The image sensor drive circuit 11 changes the scanning period of the image sensor 5 based on the scanning number signal.

As a result, the character pattern signal input to the character feature extraction circuit 8 is approximately constant for each character, and processing in the character identification circuit 9 at the subsequent stage is extremely facilitated.

Furthermore, instead of changing the scanning period of the image sensor 5, the character feature extraction circuit 8 can cut out characters in the horizontal (horizontal) direction by changing the data compression ratio based on character movement speed information. can.

By cutting out the characters in this way, the subsequent identification process is greatly simplified.

In FIG. 2, the direction of character movement is detected by the direction detection section 10, but it is also possible to provide the two image sensors 4 and 5 with a direction detection function.

That is, when the character surface in FIG. 3 moves in the A direction, the sensor 5 detects the character pattern first, and when it moves in the B direction, the sensor 4 detects it first, so that the direction can be determined.

In this case, the character movement speed can be detected by measuring the character detection time of each image sensor arranged at regular intervals, and also by counting the number of scans from when the character is detected until it passes. Character movement speed can be detected.

Therefore, the function of one image sensor is to detect the character moving speed and the cutout portion of the character, and the function of the other image sensor is to detect character features.

As explained above, the present invention can obtain a pattern with a constant relative speed by changing the scanning period of the other sensor based on the speed information from one sensor, so that the relative speed of the character surface with respect to the observation system can be changed. Effective when changing.

Furthermore, since characters are cut out in the vertical direction using one sensor, there is no need to cut out new characters using the other sensor, and processing of patterns obtained by the sensor using external force becomes simple.

Furthermore, each of the two sensors operates independently by switching depending on the direction in which the character moves, and both functionally perform either function, so it is possible to read the movement of characters in both directions. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an optical system in a conventional character reading device, FIG. 2 is a block diagram of a character reading device showing an embodiment of the present invention, and FIG. 3 is a block diagram showing an example of an optical system in a conventional character reading device. FIG. 4 is an explanatory diagram of the scanning output in FIG. 2, and FIG. 5 is a horizontal histogram created by calculating the sum of the scanning outputs. 1: Character surface, 2: Emitter, 3: Light receiver, 4, 5 one-dimensional image sensor, 6: Signal switching circuit, 7: Character cutting circuit, 8: Character feature extraction circuit, 9: Character identification circuit, 10
: direction detection section, 11: image sensor drive circuit.

Claims (1)

[Scope of Claims] 1. In a character reading device that optically reads characters using a one-dimensional image sensor in which a plurality of photoelectric conversion elements are arranged in a straight line, two one-dimensional image sensors are arranged in parallel. The character portion is detected by one of the two one-dimensional image sensors, and the character pattern is obtained by the other one-dimensional image sensor, and the character portion is detected. The scanning period of the one-dimensional image sensor that obtains the character pattern is changed by the number of times the one-dimensional image sensor scans one and a half sentences, or when the character pattern information is compressed in the preprocessing section, the degree of compression is changed. A character reading device characterized by changing. 2. The two one-dimensional image sensors arranged in parallel each have a function of operating independently, and when the direction of movement of the character surface is detected by the direction detection means for detecting the direction of movement of the character surface, Or the two one-dimensional images
When one of the sensors detects the moving direction of the character surface by capturing a character, the one-dimensional image of the one of the two one-dimensional image sensors that is closer to the character to be read is generated based on the detection result. sensor for character detection,
2. The character reading device according to claim 1, wherein the character reading device operates by switching to detect the other character pattern depending on the moving direction of the character surface.