JP3022856B1 - License plate position extraction method - Google Patents

Abstract

An object of the present invention is to accurately recognize and extract position information of a license plate. An A / D converter (19) receives an input video signal (1).
8 is converted to an AD output 39. The ternarization unit 20 converts the AD output 39 into a ternary image output 40. The address generator 22 generates address data 41. The ternary image storage 21 stores
The value image output 40 is stored according to the address data 41 and the image data 42 is output. The continuation number calculation unit 23 calculates
2 to output continuous candidate data 43. Address generator 26
Outputs address data 45. The continuous number storage 24 stores continuous candidate data 43 in accordance with address data 45 and outputs continuous data 44. The plate position calculator 25 receives the continuous data 44 and outputs plate candidate data 46.
The reordering unit 27 receives the plate candidate data 46 and outputs plate candidates 33, 34, and 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a license plate position extracting method, and more particularly to a license plate position extracting method using digital processing of a video signal.

[0002]

2. Description of the Related Art In a conventional license plate position extraction method, when position information of a license plate is extracted from an image obtained by capturing a vehicle running on a road as a still image,
If there is a background similar to the license plate (vehicle bumper, etc.), the similar background may be erroneously extracted as a license plate, and the position information of the license plate may be missed.

One example of such a technique is disclosed in
Japanese Patent No. 301883 discloses a “license plate reader”.

In this publication, a pitch corresponding to the inclination of an image is obtained from image information of a capital letter portion of a license plate normally recognized by image processing, and image information of a small letter portion is read and stored with high accuracy in accordance with the pitch. The technology is described.

[0005]

The conventional license plate position extracting method described above has a drawback that a background image similar to a license plate is erroneously extracted as a license plate.

In addition, since the pitch corresponding to the inclination of the image is obtained from the image information of the upper part of the license plate, the image recognition process is complicated.

SUMMARY OF THE INVENTION It is an object of the present invention to hold license plate position information and position information similar to the license plate, and compare the position information to extract the license plate position information without missing it. It is to provide an extraction method.

[0008]

[0009]

[MEANS FOR SOLVING THE PROBLEMS] Number play of the present invention
The position extracting method includes an analog-to-digital converter that converts an input video signal into a digital signal, a ternary conversion unit that converts the digital signal into a ternary image output, and a ternary conversion unit that generates first address data. An address generator of 1 and 3
A ternary image storage for storing the value image output in accordance with the first address data and outputting image data, a continuous number calculating unit for outputting continuous candidate data from the image data, and outputting second address data A second address generator, a continuous number storage unit that stores the continuous candidate data according to the second address data and outputs continuous data, and a plate position calculating unit that inputs the continuous data and outputs plate candidate data. , A rearrangement processing unit that inputs the plate candidate data and outputs first, second, and third plate candidates.

The rearrangement processing section receives the plate candidate data, sequentially shifts the data, and holds the data.
The second and third cages, and the first, second, and third cage outputs output from each of the cages are input and rearranged to execute the first, second, and third cages. And a rearranger for outputting plate candidates.

[0011] The rearrangement processing section may be constituted by a microcomputer.

[0012] The invention is characterized in that the rearrangement processing section is integrated by a gate array.

[0013] Further, the present invention is characterized in that position information of an object is searched.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a license plate position extracting method according to the present invention.

In the present embodiment shown in FIG. 1, A is used to convert an input video signal 18 into a digitized AD output 39.
A / D converter 19, a ternarization unit 20 for converting the AD output 39 into a ternary image output 40, an address generator 22 for generating address data 41, and storing the ternary image output 40 in accordance with the address data 41. The ternary image storage 21 that outputs the image data 42, the continuous number calculator 23 that outputs the continuous candidate data 43 from the image data 42, the address generator 26 that outputs the address data 45, and the continuous candidate data 43 Address data 4
5, a continuous number storage 24 for outputting continuous data 44, a plate position calculator 25 for inputting continuous data 44 and outputting plate candidate data 46, and a plate candidate 33, 34, And a rearrangement processing section 27 that outputs the output 35.

Here, the ternarization means that, for example, a pixel is a white pixel,
This means that gray pixels are identified in addition to the binary values of black pixels.

FIG. 2 is a detailed block diagram showing an example of the rearrangement processing section of FIG.

Referring to FIG. 2, the reordering section 27 receives the plate candidate data 46, and sequentially holds the shifters 29, 30, and 31 for holding the data, and the holder outputs 47 and 48 output from these holders. , 49, and performs a rearrangement process to output plate candidates 33, 34, and 35.

Here, the plate candidate indicates image information having a high possibility of being a license plate.

The plate candidate data 46 including the plate candidate position coordinates calculated for each of the vertical blocks are input to the holders 29, 30, and 31 in the order of input, and if there are horizontally continuous plate candidates, the rearrangement process is performed. Then, by outputting the processing result, the license plate candidates are extracted. In general, a still image captured by a camera for detecting a license plate contains a lot of unnecessary information such as a background. In order to recognize a license plate as necessary information, it is necessary to detect horizontally continuous information originally possessed by the license plate as its characteristic and eliminate unnecessary information. The still image is equally divided in the horizontal direction in order to determine whether the license plate is continuous in the horizontal direction, and the license plate is recognized by comparing adjacent blocks.

In FIG. 2, components corresponding to those shown in FIG. 1 are denoted by the same reference numerals or symbols, and description thereof is omitted.

FIG. 3 is a view for explaining an example of the image screen display according to the present invention.

This is image data representing the plate candidate data 46, and shows a state in which one image includes plate candidates 4 to 17 of a license plate, and addresses are assigned in the horizontal and vertical directions. That is, an example of a screen display in the case where a plurality of license plate candidates are present in a captured still image is shown. Here, in particular, the horizontal continuous license plate candidate groups 1, 2, and 3 are arranged such that each plate candidate of a vertical block is located between vertical blocks. Is a candidate for a license plate in the case where the number is continuous in the horizontal direction.

The vertical block indicates a 1 / N pixel column in the vertical direction formed when one image is divided into N parts in the horizontal direction.

Next, the operation of the present embodiment will be described in more detail with reference to FIGS. 1, 2 and 3.

The plate candidate data 46 output by the plate position calculator 25 is held in the holders 29, 30, and 31 and processed by the rearrangement process of the rearranger 32. The plate candidate 4 is output as the plate candidate 33. You. The plate candidate 5 is output as a plate candidate 34, and the plate candidate 6 is output as a plate candidate 35.

Next, since the plate candidate 7 is held in the holder 29 and is continuous with the plate candidate 5 in the horizontal direction, it is output as the plate candidate 34 by the reordering unit 32 in the same manner as the plate candidate 5. Similarly, the plate candidate 8 is also output as the plate candidate 34, and since there are successive plate candidates 5, 7, and 8, these are extracted as the horizontal consecutive number plate candidate group 1.

Next, the plate candidates 9 and 10 are
The plate candidates 9 and 30 are rearranged by the rearranger 32. The plate candidate 9 is output as the plate candidate 33 and the plate candidate 10 is output as the plate candidate 34. The plate candidate 11 is input to the holder 29 and is rearranged by the rearrangement processor 32 because it is continuous with the plate candidate 10 in the horizontal direction.
Is output as The plate candidates 12 and 13 are input to the holders 29 and 30, however, since the plate candidate 13 is continuous with the plate candidate 11 in the horizontal direction, the plate candidate is rearranged by the rearrangement processor 32 and output as the plate candidate. You. On the other hand, the plate candidate 12 is output as the plate candidate 33.

Since the plate candidates 10, 11, and 13 are continuously present, they are extracted as a horizontally consecutive license plate candidate group 2. Next, plate candidates 14 and 15
Since they are continuous with the plate candidates 12 in the horizontal direction, they are similarly output as plate candidates 33, and are extracted as a horizontally consecutive number plate candidate group 3. The plate candidates 16 are input to the holder 30 and output as plate candidates 34. The plate candidate 17 is input to the holder 29 and output as a plate candidate 33.

Here, the operation of the rearranger 32 will be described.

As described above, rearranging the plate candidates in the vertical direction means detecting plate candidates from a plurality of blocks in the vertical direction and detecting a plate candidate in which a plurality of plate candidates exist horizontally. In order to rearrange the plate candidates, for example, if three plate candidates are detected in the first vertical block, the plate candidates are held in the holders 29, 30, and 31 from the top in the vertical line order. This is to detect horizontally adjacent plate candidates held by these cages. The plate candidates of the cages sequentially entered in units of vertical blocks are compared with the vertical lines, and the vertical lines of the first cage 29 are compared with the vertical lines. If the next vertical line of the holder 30 is the same, the plate candidates of the holder 30 are rearranged and detected as a horizontally adjacent horizontal continuous number plate candidate group.

FIG. 4 is a diagram for explaining the rearrangement process.

FIG. 4 shows a state in which the plate candidates are held in the respective holders based on FIG. 3, and the numbers of the plate candidates correspond in the respective drawings. Referring to FIG. 4, the license plate marked with () is a plate candidate based on the horizontal continuity. As a condition for determining the plate candidate, a plate having the same vertical line on the scanning line, that is, a plate arranged horizontally adjacently is selected. Then, the following three patterns A, B, and C are obtained.

A: (5), (7), (8) B: (1)
0), (11), (13) C: (12), (14), (15) By comparing these plate candidates with vertical lines, whether or not there is continuity is detected by the input of the holder 29. Because
If you output from the top in the vertical line order based on these,
The final output is obtained as follows.

First: (12), (14), (15) are plate candidates 33 Second: (5), (7), (8) are plate candidates 34 Third: (10), (11), (13) Plate candidate 35 As described above, a plate candidate is calculated from the captured still image on the basis of the character arrangement of the license plate in units of vertical blocks, and the plate candidate exists continuously in the horizontal direction. When there are a plurality of plate candidates in each vertical block as shown in the above, the plate candidates are held in the holders 29 to 31 from the head in units of vertical blocks. On the other hand, when the held information continuously exists in the horizontal direction, a plurality of license plate candidates are extracted by rearranging the outputs from the holders 29 to 31 by the rearranger 32.

Note that the rearrangement processing section 27 can be constituted by a microcomputer instead of a hard wire logic. Also, the rearrangement processing unit 27
Can be integrated by a gate array and used as an LSI.

Furthermore, the present invention is not limited to the position extraction of the license plate described here, but can also be used for searching for position information of a characteristic object by image processing.

[0039]

As described above, the license plate position extracting method of the present invention recognizes the horizontal continuity of a license plate image from a captured still image, thereby obtaining position information of a plurality of license plates. Since it can be extracted, there is an effect that the position information of the license plate is accurately recognized without being missed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a license plate position extracting method according to the present invention.

FIG. 2 is a detailed block diagram illustrating an example of a rearrangement processing unit in FIG. 1;

FIG. 3 is a diagram illustrating an example of an imaging screen display according to the present invention.

FIG. 4 is a diagram illustrating a rearrangement process.

[Explanation of symbols]

 1, 2, 3, horizontal consecutive number plate candidate group 4 to 17 plate candidate 18 video signal 19 A / D converter 20 ternarization unit 21 ternary image storage unit 22 address generator 23 continuation number calculation unit 24 continuation number storage Container 25 Plate position calculation unit 26 Address generator 27 Rearrangement processing unit 29, 30, 31 Holder 32 Rearranger 33 Plate candidate 34 Plate candidate 35 Plate candidate 39 AD output 40 Tri-level image output 41 Address data 42 Image data 43 Continuous candidate data 44 Continuous data 45 Address data 46 Plate candidate data 47, 48, 49 Cage output

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G08G 1/00-1/16

Claims (5)

(57) [Claims] 1. An analog-to-digital converter for converting an input video signal into a digital signal, a ternary conversion unit for converting the digital signal into a ternary image output, and a first unit for generating first address data. An address generator, a ternary image storage device that stores the ternary image output according to the first address data and outputs image data, and a continuation number calculation unit that outputs continuation candidate data from the image data. A second address generator for outputting second address data, a continuous number storage for storing the continuous candidate data according to the second address data and outputting continuous data, and a plate candidate data for inputting the continuous data; And a rearrangement processing unit that inputs the plate candidate data and outputs first, second, and third plate candidates. Plate position extraction method. 2. The reordering unit receives first, second, and third holders for inputting and sequentially shifting the plate candidate data and holding the data, and first, second, and third holders output from the respective holders. the running input reordering the holding output of the second and third first, claims that is characterized in having a sorting unit for outputting a second and third plate candidate 1. License plate position extraction method according to 1. 3. The license plate position extracting method according to claim 2 , wherein said rearrangement processing section is constituted by a microcomputer. Wherein said rearrangement unit is, license plate position extraction method according to claim 2, characterized in that it is integrated by the gate array. 5. A license plate position extraction system comprising the license plate position extraction system according to claim 1 , wherein the position information of the object is searched.