JPS59180410A - Automatic identifying method of automobile - Google Patents

Abstract

PURPOSE:To perform identification process at an extremely high speed and to perform automatic identification of automobiles effectively, by determining the registered numbers of the automobiles at a constant distance by a TV camera all the time. CONSTITUTION:The registered numbers of automobiles are detected by using a TV camera. As for a position where the TV camera is placed, the position, where the vehicle is once stopped or goes slowly, such as, e.g., a toll station of a speed way or an intersection is suitable. The DC component of a picture signal obtained by the TV camera is cut in a filter circuit (c) in order to extract bright and dark data, which are the features of the picture. Then the signal is sliced in a comparator (d) at a specified level. Thus binary coding is performed. The binary-coded picture signal is decomposed into many picture element signals. Picture element shift registers (b) in the number of stages corresponding to a picture element number N for one scanning line are arranged in parallel in multiple stages by a number M of the scanning lines occupying one character of the registered number in the longitudinal direction in one screen. The signals of the picture elements obtained from the binary coded picture signal of each scanning line are sequentially stored in the registers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically identifying a vehicle by automatically recognizing the registration number displayed on the vehicle's license plate.

Automatic identification of vehicles by automatic recognition of vehicle registration numbers 1d
It can be effectively used not only to discover stolen vehicles and automate toll collection on toll roads, but also to measure the number of passing vehicles, average speed, density, etc. of automobile traffic flow.

When performing such automatic recognition of vehicle registration numbers, the processing time is slow when applying pattern recognition technology using a general computer that has been used in the past, making it difficult to process fast phenomena such as traffic flow. I can't.

However, if the characteristics of a vehicle registration number are effectively utilized, a vehicle can be identified extremely quickly by recognizing the registration number.

In other words, the display of the above vehicle registration number is standardized with some exceptions, and the shape and dimensions are all the same.
It is painted with sharp contrast. It is also displayed in the same location on both cars. Therefore, displaying this registration number is advantageous for automatic recognition rather than capturing it with a television camera and processing the video signal, and this makes it possible to easily and reliably identify a vehicle. I can do it. In particular, since the size of the numbers etc. used in the display is constant, if you place the TV camera at a position where the distance between the display and the display is approximately constant and observe it, the numbers etc. will always be displayed. will appear to be a certain size, and therefore a standard pattern for numbers etc. in a state that will be observed by a television camera at a specific distance is created in advance and registered in the recognition device, By comparing what is actually captured by a television camera at that specific distance, automatic recognition of the registration number can be performed in an extremely short time and with fewer erroneous recognitions.

The present invention aims to provide a method for automatically identifying a vehicle in real time by automatically recognizing the vehicle registration number. A TV camera located at a distance captures an image of a certain size, converts the video signal into a λ value, and then sets up shift registers in parallel according to the size of the letters in the registration number. ,
It is stored in these shift registers, and the registration number is recognized by comparing this lambda-valued video signal with a standard pattern registered in advance in the recognition device, and the vehicle is identified based on that. be.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

In the automatic recognition of vehicle registration numbers based on the present invention,
First, as shown in FIG. 1, a vehicle registration number is detected using a television camera. This television camera uses video information as a surface, so a sequential operation method is suitable.

Further, the suitable location for installing this television camera is a place where cars temporarily stop and then slow down, such as at expressway toll booths and intersections. Automatically recognizing the registration number of a car traveling at high speeds requires a special camera, such as a television camera with a shutter.

The above TV camera is adjusted so that it can clearly detect the registration number of a car that has arrived at a certain distance from its installation position. Therefore, registration number recognition processing, which will be described later, can be easily performed in a short time. In addition, in order to detect only the registration number of a car located at a certain distance from the TV camera as described above, it is possible to detect the registration number of a car at a certain distance from the TV camera by using binocular vision using two TV cameras. By arranging the two television cameras so that they intersect and ANDing the images from both television cameras, it is also possible to extract only the video signal when the two images match and perform recognition processing. In this case, when the images from the two television cameras match, subsequent registration number recognition processing is performed on the video signal, thereby making it possible to greatly reduce misrecognition.

In order to extract the brightness information that characterizes the image, the video signal obtained by the above TV camera is sliced at a constant level by a comparator after cutting the DC component in a filter circuit, as shown in the figure. By doing so, it is converted into a λ value. Then, this λ-valued video signal is decomposed into signals of a large number of pixels in a shift register A, and further, a pixel shift register with a number of stages corresponding to the number of pixels of /scanning line is divided into signals of registration numbers in one screen. / characters are provided in parallel in multiple stages equal to the number M of scanning lines in the vertical direction, and these are made to sequentially hold pixel signals obtained from the λ-valued video signal of each scanning line. For example, when dividing the horizontal direction into 512 pixels, use a 512-stage pixel shift register, and arrange the same number of pixels in parallel in one screen as many as M, the number of Kamishima scanning lines. become.

In this way, chronological! The digitized video signal is sequentially delayed and stored in the pixel shift register. Therefore, if each shift register is provided with an output terminal, it becomes possible to simultaneously obtain the information of the MXH pixels.

It is stored in the pixel shift register! The entire portion of the digitized video signal corresponding to the vehicle registration number is extracted and the registration number is recognized by pattern matching.

In general, long row shift registers have an output end only at the last stage, so a shift register for registration numbers with n stages can store pixel information corresponding to the horizontal size of each digit of the registration number. A required number M of shift registers are arranged in parallel, and these shift registers hold information for one registration number. In this case, as mentioned above, the distance to the license plate of the vehicle is determined by the television camera at a certain distance (i.e., the vehicle registration number is a certain size in the image of the television camera). Since the image is captured, the binarized video signal of the registration number is
It is stored as having a fixed size in an M x n shift register.

On the other hand, standard patterns such as digits (including ``]-'', dot, etc.), hiragana, and kanji to be recognized are registered in advance in the recognition device. This standard number turn is created to have the same size as the registration number that is imaged by a television camera and stored in the M x n shift register.

As shown in Fig. 2, the content of the M x n shift register obtained from the video signal of the television camera and the above standard pattern are compared by calculating, for example, exclusive OR using the logic operation circuit. As a result, an adder calculates how many pixels the content of the two matches and how much of a difference there is, and a comparator with a mismatch tolerance set in consideration of recognition accuracy determines whether the content matches or does not match. If the standard pattern is determined to be a match, it is recognized as the same numbers or characters as the standard pattern, and is stored in the microcombinator along with the position on the television image.

Furthermore, since automobile registration numbers are displayed with regularity in the arrangement of numbers, etc., and letters, numbers, hyphens, etc. are displayed in a fixed arrangement, by repeating the character recognition described above, it is possible to obtain a specified number. When a number or the like is recognized in the array, it is recognized as a vehicle registration number, a message to that effect is appropriately displayed, and the recognition process is completed.

As is clear from the above detailed description, according to the present invention, the characteristics of a vehicle registration number, namely, its display is standardized and has a clear contrast, and is unique to any vehicle. We focused on the points displayed in almost the same position and always captured them from a certain distance with a TV camera.We converted the video signal into a λ value and compared it with a standard pattern, which enabled us to recognize it at extremely high speed. processing can be carried out, and therefore automatic vehicle identification can be carried out effectively.

[Brief explanation of drawings]

1 and 2 are block diagrams showing an outline of an apparatus for carrying out the method of the present invention.

Claims (1)

[Claims] 1. The registration number displayed on the license plate of a car is captured by a TV camera at a certain distance from the registration number, and the image signal is converted into a value, and then registered. Shift registers are provided in parallel according to the size of the letters in the number, stored in these shift registers, and this λ-valued video signal is compared with a standard pattern registered in the recognition device in advance. An automatic vehicle identification method characterized by recognizing a number and identifying the vehicle based on the number.