JPH0520497A - License plate character cutting device - Google Patents

Abstract

(57) [Summary] [Purpose] The character area of the license plate is cut out from the captured image. [Structure] An image obtained by capturing an image of a vehicle by a camera 1 is once stored in an image memory 2 and then replaced by a binary image by a binarization processing circuit 3. Further, the image is divided by the area dividing circuit 4, and the same character area candidate as the predetermined designated frame is extracted by the character area candidate extracting circuit 5. Then, the character relationship around the character area candidate is detected by the positional relationship detection circuit 6, and the character area selection circuit 7 selects one that matches the character positional relationship of the license plate, and the license plate is cut out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a license plate character slicing device for imaging a vehicle with a camera and slicing a character area of a license plate from the captured image.

[0002]

2. Description of the Related Art Conventionally, in a license plate clipping device, a binarization process is performed on a captured vehicle image, and a region dividing process is performed on the binary image by labeling process. Further, the vehicle number character area is selected from the already divided areas by using known information such as the vertical dimension and the horizontal dimension of the circumscribing frame surrounding the vehicle number character area. An example of the above-described conventional license plate recognition device will be described below with reference to the drawings.

FIG. 2 is a schematic block diagram of a conventional license plate character cutting device. In FIG. 2, reference numeral 1 denotes a camera, which outputs one frame data of a vehicle image. 2 is an image memory for A / D analog image data from the camera
It is converted and stored as digital image data. 3 is 2
The binarization processing circuit converts the image data output from the image memory 2 into binary image data. 4 is a region division circuit,
Region division processing is performed on the binary image data. A character area selection circuit 8 cuts out a character area from the shape feature of the license plate character.

Next, the operation of the above embodiment will be described.
The vehicle multi-valued image input by the camera 1 is stored in the image memory 2
Is stored in the binarization processing circuit 3 by the threshold value obtained by using a method such as a discrimination threshold value selection method.
Converted to a value image. Further, the binary image data is subjected to labeling processing in the area dividing circuit 4 to perform area division, and then in the character area selecting circuit 8, the circumscribing frame surrounding the outer circumference of the character and the positional relationship between the circumscribing frame are shown in FIG. Among the license plates shown, the land support, the vehicle type, the use, and the code of the serial number, the positional relationship of the same circumscribing frame as the serial number was searched for, and characters were cut out as the license plate.

[0005]

However, in the above-mentioned conventional license plate character slicing device, when selecting a license plate character region from the divided regions, the license plate character slicing device is simply selected from the positional relationship between the circumscribing frames. Since the serial number is searched for, there is a problem that an incorrect area is selected if there is an area-divided area having a similar positional relationship between circumscribing frames.
The present invention solves such conventional problems,
An object of the present invention is to provide an excellent license plate character slicing device that solves the above-mentioned problem of area division and can perform good character slicing.

[0006]

In order to achieve the above-mentioned object, the present invention extracts a character area candidate extracting means for extracting a circumscribing frame having the same vertical and horizontal lengths among the areas divided by the area dividing means. And a positional relationship detecting means for detecting a character positional relationship around the extracted character area candidates, and a character area selection for selecting one of the character area candidates having the detected character positional relationship that matches the character positional relationship of the license plate. Means are provided.

[0007]

Therefore, according to the present invention, among the extracted character area candidates, the character positional relationship around these candidates can be compared with the character positional relationship of the license plate, and a matching character area candidate can be selected. , Even if it is a character area candidate that matches the vertical and horizontal lengths of the circumscribing frame of the serial number of the license plate, it will not be selected as the license plate unless the character positional relationship around the character area candidate matches, so a more accurate number It has the effect of allowing the characters to be cut out from the plate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A license plate character cutting device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a camera, which outputs one frame data of a vehicle image. An image memory 2 A / D converts the analog image data from the camera and stores it as digital image data. A binarization processing circuit 3 converts the image data output from the image memory 2 into binary image data. An area dividing circuit 4 performs area dividing processing on the binary image data. A character area candidate extraction circuit 5 selects character area candidates based on the vertical and horizontal lengths of a circumscribing frame surrounding the outer circumference of the character divided by the area dividing circuit. A positional relationship detection circuit 6 detects the positional relationship of each of the character area candidates selected by the character area candidate extraction circuit. Numeral 7 is a character area selection circuit, which determines whether or not each area selected above is located at the location of land support, vehicle type, application, or serial number based on the result detected by the positional relationship detection circuit. The selected area is selected as the character area.

Next, the operation of the above embodiment will be described.
The vehicle multi-valued image input by the camera 1 is stored in the image memory 2
Memorized in. In the binarization processing circuit 3, the Laplacian histogram method is applied to the multivalued image data.
A density histogram is created only for pixels having a large absolute value of the second-order differential value, and a threshold value is obtained from this density histogram by using the discrimination threshold value selection method and converted into a binary image. This binary image data is subjected to labeling processing in the character area dividing circuit 4 to perform area division, and then in the character area candidate extracting circuit 5, the vertical and horizontal lengths of the circumscribing frames surrounding this area are known. The area that is compared with the length and has the same circumscribing frame layout as the serial number in the license plate is extracted as a license plate character area candidate.

After extracting the license plate character area candidates, the positional relationship detecting circuit 6 detects the relationship with the surrounding character positions from the center position coordinates or the barycentric position coordinates of the areas extracted as the character area candidates. To do.
In the character area selection circuit 7, based on the position coordinates detected above, it is determined whether or not each character area candidate exists at the position of the licensed licenser, vehicle type, application, and serial number,
Select the matching one from the character area candidates.

As described above, according to the above embodiment, among the extracted character area candidates, the character positional relationship around these candidates is compared with the character positional relationship of the license plate, and the matching character area candidates are selected. Therefore, it is possible to more accurately cut out the characters on the license plate.

In the above embodiment, the serial number of the license plate is targeted as a character area candidate. However, any one of the land support of the license plate, vehicle type, application and serial number may be specified. However, it has the same effect as the above embodiment.

[0014]

The present invention is clear from the above embodiment,
Of the extracted character area candidates, the character positional relationship around these candidates is compared with the character positional relationship of the license plate, and the matching character area candidate can be selected. It can be said that even if character area candidates that match the vertical and horizontal lengths of are not selected as license plates unless the character position relationships around the character area candidates match, more accurate license plate character cutting is possible. Has the effect. Even in image data including a large number of regions having substantially the same circumscribed frame shape, the character region can be reliably cut out without error, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a license plate character cutting device according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a conventional license plate character cutting device.

FIG. 3 is a diagram showing an example of names of license plates.

[Explanation of symbols]

 1 camera 2 image memory 3 binarization processing circuit 4 area division circuit 5 character area candidate extraction circuit 6 positional relationship detection circuit 7 character area selection circuit

Claims (1)

Claim: What is claimed is: 1. A camera for picking up an image of a vehicle, an image data storage unit for storing image data input by the camera, and a binary image for the image data stored in the image data storage unit. Binarization processing means for converting to data and this 2
A region dividing unit that divides the binary image binarized by the binarizing unit into regions, a character region candidate extracting unit that extracts the same character region candidate as a predetermined specified frame from the region dividing unit, A positional relationship detecting means for detecting the positional relationship of the characters located around the extracted character area candidates, and the positional relationship of the characters detected by the positional relationship detecting means from the character area candidates and the character of the license plate. A license plate character slicing device comprising a character area selecting means for selecting one having a matching positional relationship.