JPS63174197A - Number plate position detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a license plate position detection device that extracts only the license plate portion from a predetermined image when automatically reading the license plate number of a vehicle.

BACKGROUND ART FIG. 10 is a diagram of an image memory in a conventional license plate position detection device, and FIG. 11 is a diagram of a standard pattern of a license plate of the conventional example.

The conventional license plate position detection device temporarily stores an image including the license plate in an image memory 1 as shown in FIG. (
(cut out).

The problem that the invention aims to solve This conventional extraction method is called a pattern matching method.

However, according to the conventional pattern matching method,
Since the license plate 2 in the image memory 1 is much smaller than the image memory 1, a simple comparison with the standard pattern 9 requires comparing each pit one by one, which requires a large number of comparison/judgment circuits and takes a long time to process. It takes time. In addition, for license plates that are different in size from the standard pattern, or for license plates that are installed at an angle to the vehicle, the cutting accuracy may be significantly reduced, and the license plate image in the image memory may have vertical and horizontal orientations. Since distortion may occur, it was necessary to prepare several types of standard patterns and perform pattern matching on each.

In addition, since the font color and background color of the plate are reversed for private use and self-mounted use, it was necessary to prepare twice the number of non-inverted and inverted patterns for the above pattern.

Therefore, since many types of standard patterns are compared one by one, there is a problem in that the processing time increases significantly.

The present invention eliminates the problems of the conventional example,
It is highly accurate even for license plates of different sizes and tilts of the license plate, and is excellent in that it extracts the license plate part from the image memory at high speed and determines its position without distinguishing between inverted and non-inverted plate colors. The purpose of the present invention is to provide a license plate position detection device.

Means for Solving the Problems In order to achieve the above object, the present invention provides a ternarization circuit that classifies the results of calculating the projection sum for each block in an image memory into white, black, and three values in between. is provided, and each level of these three values is continuously compared with a plate judgment condition set value that takes into account errors in plate size and plate inclination.

Comparison (=In this case, both white and black are the background part, and the intermediate level can be used as the text part.

Therefore, according to the present invention, it is only necessary to compare the continuous length of white or black and the continuous length of the intermediate level with the set value.
There is no need to shift each bit bit by bit to match multiple patterns of different sizes and colors, which significantly reduces processing time.

EXAMPLE Below, the configuration of an example of the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of a license plate position detection device according to an embodiment of the present invention.

In FIG. 1, 21 is a camera that images the screen including the license plate, 22 is an A/D conversion circuit that converts the image signal of the camera 21 into a digital signal, and 23 is this A/D.
This is a binarization circuit that converts the digital signal of the conversion circuit 22 into a binary signal based on the density of the license plate.

24 is an image memory that stores this binary signal, 25 is a plate horizontal position detection circuit that detects the horizontal position of the license plate in the image memory 21I, and 26 is an image memory 24.
A plate vertical position detection circuit 27 detects the vertical position of the license plate inside; 27 is a plate horizontal position detection circuit 2;
5 and the position information of the plate vertical position detection circuit 26. Reference numeral 28 denotes an output terminal for outputting a signal obtained by cutting out only the license plate portion from the image memory 24 by the character cutting circuit 27.

The plate horizontal position detection circuit 25 and the plate vertical position detection circuit 26 are constructed as shown in FIGS. 2 and 3, respectively.

In FIG. 2, 24a is an input terminal for inputting the output of the image memory 24, 30 is a memory address calculation circuit that calculates addresses in the image memory 24 and calculates each divided block address, and 31 is this memory address calculation circuit 30. A projection adder circuit 32 sequentially adds the data of the addresses of , and ternaryizes this addition result into three levels of white, intermediate, and black, and divides each divided block into a vertical column of l'-00J, "01", or "10". A digitization circuit 33 is a circuit for counting the number of consecutive white, intermediate, or black colors that calculates this ternary signal.

35 is a comparison judgment circuit that compares the horizontal direction plate judgment condition setting value 34 set in advance with the consecutive number of three values, and if the consecutive number is within the set value range, the output is sent to the plate horizontal position output 36. A match signal is output, and if there is no match, a match signal is output to the memory address arithmetic circuit 3o to cause the next divided block to be processed.

In FIG. 3; 2, parts having the same functions as those in FIG. 2 are given the same numbers. ,: 252 is an input terminal to which the output of the plate horizontal position detection circuit 25 is input; 37 is an input terminal for calculating the address of the input signal of the input terminal 25a, and the image memory 2
a memory address calculation circuit that calculates the vertical address of 4;
Reference numeral 38 designates a preset vertical plate determination condition setting value, and reference numeral 39 designates a plate vertical position output that outputs the vertical position of the license plate when a one-turn signal is input from the comparison determination circuit 35. This vertical position signal is output from the output terminal 26a.

FIG. 4 shows a diagram of the standard pattern of the license plate according to this embodiment, FIG. 5 is a horizontal projection of this standard pattern, and FIGS. 6(a) and (b) are vertical projections of the standard pattern. 7 is a diagram of a binarized image memory after the license plate is imaged according to this embodiment, and FIG. 8 is a horizontal projection diagram of this image memory diagram.

Figures 4 to 8 (= where 41 is the license plate,
42 is a code indicating the region and vehicle type, 43 is a serial number, 42a
is a horizontal projection of the symbol 42, and 43a is the serial number 43
, 42b is a vertical projection of 42, and 43b is a vertical projection of 43.

Reference numeral 44 is an image memory diagram in which the license plate 41 is imaged and binarized. It is divided according to 4.
5 is the license plate to be detected.

Next (=, the operation of the above embodiment will be explained.

In FIG. 1, when a camera 21 captures an image of a screen including a license plate, an A/D converter 22 converts the image into a digital value. This digital value is converted into a binarization circuit 23.
converts it into black and white binary values and stores it in the image memory 24.

In order to cut out the number plate portion from the image in the image memory 24, first, the plate horizontal position detection circuit 25 determines the horizontal position. 2 to 8 (=), the memory address calculation circuit 30 detects the position of the boundary line 51 of the image memory 44, the projection addition circuit 31 calculates the projection sum, and the ternarization circuit 32 calculates the projection sum. White, black, 3 at intermediate level
Value. Then, for the ternary data, the number of consecutive intermediate levels from the top is counted by 33, and the comparison/determination circuit 25 determines whether this satisfies the set value of the determination condition circuit 34.

In FIG. 7, the boundaries 51 and 5 of the image memory 44 are
Since the block surrounded by 2 does not have a continuous number of intermediate levels, the memory address calculation circuit 30 uses the next boundary lines 52 and 53.
The block surrounded by (one block is compared in the same way.

If the memory address calculation circuit 30 processes the blocks surrounded by 53 and 54, 42a and 43 in FIG.
a is at an intermediate level and the consecutive number is within the allowable range of 12 and 24 in Fig. 5, and above 42a, between 42a and 432, and 43
If the area below a is all white or all black and the consecutive number is within 13 between 422 and 438, if the area above 428 is 11 or more and the area below 432 is 15 or more, it is determined to be a plate, and 4
2a is the land/vehicle type code section, and 43a is the horizontal address of the serial number section.

Next, the plate vertical position detection circuit 26 detects the vertical position at the sixth position.
Figures (a) and (b) are projected separately. In this case, since the number of characters is different, the plate judgment condition setting value 38 has a plurality of set values of 1, but basically the memory address calculation circuit 37 specifies the location on the image memory 44 in the same process as in the horizontal direction.

In this manner, when the plate horizontal position detection circuit 25 and the plate vertical position detection circuit 26 detect the position of the license plate in the image memory 24, the character cutout circuit 27 cuts out the license plate and outputs it from the output terminal 28.

FIG. 9 is a block diagram showing an application example of the plate position detection device which is an embodiment of the present invention. In FIG. 11, 46 is a (number) plate position detecting device according to this embodiment, and this plate position detecting device 46 detects a number from a predetermined screen.

- Cut out only the part marked "-" and send it to the character recognition circuit 47. 48 is a determination result output unit that outputs the characters of the license plate recognized by the character recognition circuit 47. In this way, the (number) plate position detection device 46 is applied to read the characters on the license plate after cutting out the characters on the license plate.

Effects of the Invention As is clear from the above embodiments, the present invention has the following effects.

(1) Set the projection direction of each block in the image memory to white, black,
Intermediate level ternaryization is performed, but white and black are the plate background parts,
Since the intermediate level is judged as a plate character part, the judgment can be made by comparing two values, and the circuit remains simple, and the same processing can be performed for plates with reversed black and white backgrounds for home use and business use without being aware of the reversal. You can cut out the plate.

(2) By changing the upper and lower limits of the slice level setting values for ternarization (c), it is effective in retry processing for brightness fluctuations and plate stains, and the plate cutting rate can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a license plate position detection device according to an embodiment of the present invention, FIG. 2 is a block diagram of a plate horizontal position detection circuit of the same embodiment, and FIG. 3 is a block diagram of a plate vertical position detection circuit of the same embodiment. FIG. 4 is a standard pattern diagram of the license plate of the same embodiment, FIG. 5 is a horizontal projection of the standard pattern of the same embodiment, and FIG. 6(a)
, (b) is a vertical projection view of the standard pattern of the same example, Figure 7 is a binarized image memory diagram after license plate imaging of the same example, and Figure 8 is a horizontal view of this image memory diagram. 9 is a block diagram showing an application example of the same embodiment, FIG. 10 is a diagram of an image memory of a conventional example, and FIG. 11 is a diagram of a standard pattern of a conventional license plate. 21... Camera, 22... A/D conversion circuit, 23.
...Binarization circuit, 24...Image memory, 25...Plate horizontal position detection circuit, 26...Plate vertical position detection circuit, 27...Character cutting circuit, 30...Memory address calculation circuit , 31... Projection addition circuit, 32
-...Binarization circuit, 33...Continuous 3-value counting circuit, 34...Plate judgment condition setting circuit, 35...
Comparison/judgment circuit, 36...Plate horizontal position output, 39
... Plate vertical position output, 41. ,,Standard pattern of license plate, 44...Number plate that can be image-memorized. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure Otsu Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 2b, 41 Figure 7 M 8 Figure

Claims (1)

[Claims] An image memory that binarizes and stores the image including the license plate in black and white, a projection addition circuit that projects the specified area of this image memory in the horizontal and vertical directions, and the sum of the outputs of this projection addition circuit as white. A ternarization circuit that divides the black into three levels between black and black, and a continuation number counting circuit that calculates the continuation width of each level for each of the three values from the output of this ternarization circuit.
The plate judgment condition setting circuit, which is predetermined to allow for errors in plate size and plate inclination, is compared with the output of the 3-level continuous number counting circuit and the output of the plate judgment condition setting value circuit, and the conditions are determined. If satisfied, output that area as the plate horizontal position,
A license plate position detection device comprising: a comparison determination circuit that advances the designated area of the projection addition circuit to the next level if the specified area is not satisfied.