JP3591583B2 - Recording medium recording license plate recognition system and batch dictionary creation / collation program - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a license plate recognition system for recognizing a license plate for a vehicle and a recording medium recording a program for creating / collating a collective dictionary.
[0002]
[Prior art]
As shown in FIG. 6, the license plate for a vehicle in Japan is composed of a plurality of items of land transportation branch office code / vehicle type code / use code / serial number, and each item is composed of one or more characters.
[0003]
In a conventional license plate recognition system, characters constituting a license plate are separated one by one as shown by a broken line in FIG. 6, and character recognition is performed using a technique such as pattern matching for each character individually. .
[0004]
[Problems to be solved by the invention]
However, in the conventional license plate recognition system, it is difficult to increase the resolution by enlarging the license plate due to the limitation of the number of pixels of the photographing camera and the photographing range. Separation becomes difficult, and in particular, there is a problem that the separation of characters of a land transportation branch office code or a vehicle type code fails, and recognition becomes impossible or erroneous recognition occurs.
[0005]
In particular, with regard to the vehicle type code, the tendency of occurrence of a problem such as unrecognition is increasing as the vehicle type code is converted into three digits.
[0006]
The present invention has been made in view of the above-described problems of the related art, and is capable of improving a license plate recognition rate without causing unrecognizable or erroneous recognition. It is an object of the present invention to provide a recording medium recording a recognition system and a program for creating / collating a collective dictionary.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
A camera for photographing a license plate including a plurality of items, and each character constituting the license plate is cut out from the license plate photographed by the camera, and the cut-out characters are separated for each of the plurality of items; A license plate recognition system comprising: a license plate recognition device that collectively recognizes all of the characters constituting the item for each item of
The license plate recognition device,
An individual dictionary which is a dictionary pattern of each character constituting the plurality of items, and a collective list which is a combination list for making a combination of each character of the individual dictionary into a combination existing in each of the plurality of items And a dictionary medium for storing
A dictionary combining function unit that creates a collective dictionary that is a dictionary pattern of a combination of characters present in each of the plurality of items by combining each character of the individual dictionary based on the collective list stored in the dictionary medium; ,
A dictionary memory for storing the collective dictionary created by the dictionary combining function unit;
A character cutout function unit that cuts out each character constituting the license plate from the license plate photographed by the camera,
A separating function unit that separates the character cut out by the character cutting function unit for each of the plurality of items;
For each of the plurality of items separated by the separation function unit, a character collation function unit for collating all of the characters constituting the item collectively with the batch dictionary stored in the dictionary memory,
On the basis of the result of collation with the collective dictionary in the character collation function unit, all the characters constituting the item are collectively recognized for each of the plurality of items.
[0009]
Further, the dictionary memory stores the individual dictionary stored in the dictionary medium while storing the collective dictionary,
The character collation function unit, for each of the plurality of items separated by the separation function unit, collectively collates all of the characters constituting the item with the batch dictionary, and is cut out by the character cutout function unit. Collated each character with the individual dictionary stored in the dictionary memory,
Based on the result of collation with the collective dictionary in the character collation function unit, all of the characters constituting the item are collectively recognized for each of the plurality of items, and the character dictionary is compared with the individual dictionary in the character collation function unit. It is characterized in that the character is recognized for each character based on the collation result.
[0010]
In addition, each character constituting the license plate including a plurality of items is cut out, and the cut-out characters are separated for each of the plurality of items, and then all the characters constituting the item are collectively collected for each of the plurality of items. A storage medium storing a program for creating / collating a collective dictionary used for recognition,
An individual dictionary which is a dictionary pattern of each character constituting the plurality of items and a collective list which is a combination list of each character of the individual dictionary which is a combination existing in each of the plurality of items are read. Steps and
Creating a collective dictionary which is a dictionary pattern of a combination of characters present in each of the plurality of items by combining each character of the individual dictionary based on the collective list stored in the dictionary medium. Is recorded.
[0011]
A step of photographing the license plate;
Cutting out each character constituting the license plate from the license plate;
Separating characters cut out from the license plate for each of the plurality of items,
A step of collectively collating all of the characters constituting the item with the collective dictionary for each of the plurality of items.
[0012]
Also, a program is recorded for each of the plurality of items, wherein all characters constituting the items are collectively collated with the collective dictionary, and each character cut out from the license plate is collated with the individual dictionary. It is characterized by the following.
[0013]
(Action)
In the present invention configured as described above, each character constituting the license plate is cut out, and the cut-out character is separated into a plurality of items. In order to collectively recognize the characters, even if the extraction of the characters fails, the characters that failed to be extracted are separated for each item, and then all the characters constituting the items are collectively recognized for each item.
[0014]
As described above, even if the extraction of characters fails, it is possible to prevent the occurrence of unrecognizable or erroneous recognition, thereby improving the recognition rate.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a diagram showing an embodiment of a license plate recognition system according to the present invention.
[0017]
As shown in FIG. 1, the present embodiment is directed to a camera 16 that shoots a video including a license plate and outputs the video signal, and a license plate recognition device that performs character recognition processing based on the video signal output from the camera 16. And 10.
[0018]
Further, the license plate recognition device 10 includes an A / D conversion processing unit 11 that converts a video signal output from the camera 16 into a digital image, and a license plate conversion unit that converts the digital image converted by the A / D conversion processing unit 11 into a digital image. A plate cutout processing unit 12 for detecting an image, a dictionary medium 14 for storing an individual dictionary and a batch list (details will be described later), and characters cut out and cut out from a license plate image detected by the plate cutout processing unit 12. A character recognition processing unit 13 for recognizing characters based on an individual dictionary and a batch list stored in a dictionary medium 14, and outputs a result of recognition of the characters recognized by the character recognition processing unit 13 to an external device (not shown). And an output processing unit 15.
[0019]
FIG. 2 is a diagram illustrating a configuration example of the character recognition processing unit 13 illustrated in FIG.
[0020]
As shown in FIG. 2, the character recognition processing unit 13 in the present configuration example reads the individual dictionary 29 and the collective list 30 stored in the dictionary medium 14 and creates a collective dictionary based on the read individual dictionary 29 and the collective list 30. A dictionary combining function unit 27, a dictionary memory 28 for storing the collective dictionary created by the dictionary combining function unit 27, and a digital image input function unit 21 for taking in a digital image of the license plate detected by the plate cutout processing unit 12. And a character segmentation function unit 22 for segmenting each character from the digital image captured by the digital image input function unit 21; and a land transportation branch office code / vehicle code / application code / A code separation function unit 23 that separates a plurality of items of a serial number, For each item, a character matching function unit 24 that collectively matches all of the characters constituting the item with a batch dictionary stored in the dictionary memory 28, and obtains a recognition result from the matching result in the character matching function unit 24 It is composed of a coincidence evaluation function unit 25 and a result output function unit 26 that outputs a recognition result from the coincidence evaluation function unit 25 to the output processing unit 15.
[0021]
Here, the individual dictionary 29 is an individual dictionary pattern of each character constituting the land transportation branch office code / vehicle type code / use code / serial number, a "numeric dictionary" for the vehicle type code and the serial number, the land transportation branch office code There is a "kanji dictionary" for Japanese characters and a "Hiragana dictionary" for land transportation branch office codes and application codes.
[0022]
The collective list 30 is a combination list for making the combination of each character of the individual dictionary 29 a combination existing in the land transportation branch office code / vehicle type code / use code / serial number. There are lists of vehicle type codes / application codes / serial numbers.
[0023]
The collective dictionary is a dictionary pattern of a combination of characters present in each of the land transportation branch office code / vehicle type code / use code / serial number, and is created based on the individual dictionary 29 and the collective list 30. The above-mentioned dictionary pattern is an array (bit pattern of 0 and 1) having components in both X and Y directions.
[0024]
Hereinafter, the operation of the license plate recognition system configured as described above will be described focusing on the operation of the character recognition processing unit 13.
[0025]
3A and 3B are flowcharts for explaining the operation of the character recognition processing unit 13 shown in FIG. 2, wherein FIG. 3A is a flowchart for explaining the operation at the time of starting the apparatus, and FIG. It is a flowchart for demonstrating the operation | movement performed each time it is input.
[0026]
When the apparatus is started, the dictionary combining function unit 27 reads the individual dictionary 29 and the collective list 30 of the land transportation branch office code / vehicle type code / use code / serial number from the dictionary medium 14 (steps S301 and S302), and Based on the list 30, a collective dictionary of land transportation branch office code / vehicle type code / application code / serial number is created and written in the dictionary memory 28 (steps S303, 304). At this time, the dictionary combination function unit 27 also writes the individual dictionary 29 read from the dictionary medium 14 into the dictionary memory 28.
[0027]
Here, when the digital image of the license plate is captured by the digital image input function unit 21, the character cutout function unit 22 reads out the digital image captured by the digital image input function unit 21 and cuts out each character (step S305, S306), transfer to the code separation function unit 23.
[0028]
Next, the code separation function unit 23 separates each character cut out by the character cutout function unit 22 into items of land transportation branch office code / vehicle type code / use code / serial number as shown by the broken line in FIG. Is transferred to the character matching function unit 24 (step S307).
[0029]
Next, for each item of land transportation branch office code / vehicle type code / use code / serial number, the character collation function unit 24 collectively writes all the characters constituting the item into the dictionary memory 28, Collation is performed (step S308), and the matching degree evaluation function unit 25 evaluates the matching degree based on the result of the comparison in the character matching function unit 24 (step S309). At this time, the character collation function unit 24 also performs a process of collating each character extracted by the character extraction function unit 22 with the individual dictionary 29 as in the conventional method.
[0030]
Thereafter, the result output function unit 26 creates a recognition result based on the matching degree evaluation result in the matching degree evaluation function unit 25 and outputs the result to the output processing unit 15 (step S310).
[0031]
Thereafter, each time a license plate image is taken into the digital image input function unit 21, the processing in steps S305 to S310 described above is repeated.
[0032]
Here, the collective dictionary creation operation in the dictionary combination function unit 27 will be specifically described with reference to FIG.
[0033]
5A and 5B are diagrams for explaining the operation of the dictionary combination function unit 27 shown in FIG. 2, wherein FIG. 5A is a diagram for explaining the operation when creating a collective dictionary of vehicle type codes, and FIG. FIG. 7 is a diagram for explaining an operation when creating a collective dictionary of land transportation branch office codes.
[0034]
As shown in FIG. 5A, when creating the collective dictionary 52 for the vehicle type code, the dictionary combination function unit 27 reads the individual dictionary 51 for the vehicle type code and the collective list 53 from the dictionary medium 14 and, for example, On the basis of the list 53, “0” and “1” of the individual dictionary 51 are combined to create a collective dictionary 52 that is a dictionary pattern of “10”. Note that a dictionary pattern “01” is also conceivable as another combination of “0” and “1”. However, since the combination list “01” does not exist in the batch list 53, the dictionary pattern “01” is created. do not do.
[0035]
Also, as shown in FIG. 5B, when creating the collective dictionary 55 for the land transportation branch office code, the dictionary combining function unit 27 reads the individual dictionary 54 and the collective list 56 for the land transportation branch office code from the dictionary medium 14. For example, based on the collective list 56, the collective dictionary 55 which is a dictionary pattern of "Yamaguchi" is created by combining "mountain" and "mouth" of the individual dictionary for the land transportation branch office code.
[0036]
As described above, in the present embodiment, the character cutout function unit 22 cuts out each character constituting the license plate, and the code separation function unit 23 separates the characters cut out by the character cutout function unit 22 for each item. After that, all characters constituting the item are collectively recognized for each item.
[0037]
For this reason, for example, when the land transportation branch office code of the license plate is “Yokohama” and the vehicle type code is “500”, these characters are changed to “horizontal”, “hama”, “5” and “00” in the character extraction function unit 22. If the character extraction fails, such as cutting out or cutting out "tree", "yellow", "beach", "50", or "0", the conventional method may not be able to recognize or may cause erroneous recognition. In the present embodiment, in the code separation function unit 23, characters that have failed to be cut out can be separated for each code as “Yokohama” and “500”, and thereafter, for each code, all of the characters constituting the item are deleted. Since recognition can be performed in a lump, it is possible to prevent occurrence of non-recognition and the like.
[0038]
In this embodiment, a collective dictionary, which is a dictionary pattern of a combination of characters present in each item, is not stored in the dictionary medium, and is created on the dictionary memory based on the individual dictionary and the collective list when the apparatus is started. Therefore, it is possible to collectively recognize all the characters constituting the item for each item without increasing the capacity of the dictionary medium.
[0039]
Taking the vehicle type code as an example, the dictionary patterns of the individual dictionaries are ten types from 0 to 9, while the dictionary patterns of the collective dictionary are 1110 types considering all combinations of the vehicle type codes. Since such a collective dictionary is not stored in the dictionary medium, the capacity of the dictionary medium does not increase.
[0040]
【The invention's effect】
As described above, in the present invention, each character constituting the license plate is cut out, the cut-out character is separated into a plurality of items, and then all the characters constituting the item are collectively collected for each of the plurality of items. Therefore, even if the extraction of a character has failed, the characters that failed to be extracted can be separated for each item, and then all the characters constituting the item can be collectively recognized for each item.
[0041]
As described above, even if the character cutout fails, it is possible to prevent occurrence of unrecognizable or erroneous recognition, thereby improving the recognition rate.
[0042]
Also, based on an individual dictionary which is a dictionary pattern of each character constituting a plurality of items and a collective list which is a combination list of each character of the individual dictionary, a dictionary of combinations of characters present in each of the plurality of items is provided. Since the collective dictionary as a pattern is created, all the characters constituting the item can be collectively recognized for each item without increasing the capacity of the dictionary medium.
[0043]
In addition, since a combination list is used in which the combination of each character in the individual dictionary is a combination that exists in each of a plurality of items, a dictionary pattern that does not exist in a plurality of items is not generated. The capacity of the dictionary memory for storing the collective dictionary can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a license plate recognition system according to the present invention.
FIG. 2 is a diagram illustrating a configuration example of a character recognition processing unit illustrated in FIG. 1;
3A and 3B are flowcharts for explaining the operation of the character recognition processing unit shown in FIG. 2, wherein FIG. 3A is a flowchart for explaining the operation at the time of starting the apparatus, and FIG. 9 is a flowchart for explaining an operation performed each time the operation is performed.
FIG. 4 is a diagram for explaining an operation content of a code separation function unit shown in FIG. 2;
5A and 5B are diagrams for explaining the operation of the dictionary combination function unit shown in FIG. 2, wherein FIG. 5A is a diagram for explaining the operation when creating a collective dictionary of vehicle type codes, and FIG. It is a figure for explaining operation at the time of creating a collective dictionary of a land transportation branch office code.
FIG. 6 is a diagram for explaining the operation of a conventional license plate recognition system.
[Explanation of symbols]
Reference Signs List 10 License plate recognition device 11 A / D conversion processing unit 12 Plate cutout processing unit 13 Character recognition processing unit 14 Dictionary medium 15 Output processing unit 16 Camera 21 Digital image input function unit 22 Character cutout function unit 23 Code separation function unit 24 Character collation Function unit 25 Matching degree evaluation function unit 26 Result output function unit 27 Dictionary combining function unit 28 Dictionary memory 29 Individual dictionary 30 Batch list

Claims (5)

A camera for photographing a license plate composed of a plurality of items, and each character constituting the license plate is cut out from the license plate photographed by the camera, and the cut out characters are separated for each of the plurality of items; A license plate recognition system comprising: a license plate recognition device that collectively recognizes all of the characters constituting the item for each of the items.
  The license plate recognition device,
  An individual dictionary which is a dictionary pattern of each character constituting the plurality of items, and a collective list which is a combination list for making a combination of each character of the individual dictionary into a combination existing in each of the plurality of items And a dictionary medium for storing
  A dictionary combining function unit that creates a collective dictionary that is a dictionary pattern of a combination of characters present in each of the plurality of items by combining each character of the individual dictionary based on the collective list stored in the dictionary medium; ,
  A dictionary memory for storing a collective dictionary created by the dictionary combining function unit;
  A character cutout function unit that cuts out each character constituting the license plate from the license plate photographed by the camera,
  A separating function unit that separates the characters cut out by the character cutting function unit for each of the plurality of items;
  For each of the plurality of items separated by the separation function unit, a character matching function unit that collectively matches all of the characters constituting the item with the batch dictionary stored in the dictionary memory,
  A license plate recognition system, wherein the character matching function unit collectively recognizes, for each of the plurality of items, all of the characters constituting the item, based on a result of comparison with the collective dictionary. The license plate recognition system according to claim 1 ,
The dictionary memory stores the collective dictionary and stores the individual dictionary stored in the dictionary medium,
The character collation function unit, for each of the plurality of items separated by the separation function unit, collectively collates all of the characters constituting the item with the batch dictionary, and is cut out by the character cutout function unit. Collated each character with the individual dictionary stored in the dictionary memory,
Based on the result of collation with the collective dictionary in the character collation function unit, all of the characters constituting the item are collectively recognized for each of the plurality of items, and the character dictionary is compared with the individual dictionary in the character collation function unit. A license plate recognizing system for recognizing each character based on a collation result. After cutting out each character constituting the license plate composed of a plurality of items, separating the cut-out characters for each of the plurality of items, all of the characters constituting the item are collectively recognized for each of the plurality of items. A storage medium storing a program for creating / collating a collective dictionary used at the time of
An individual dictionary which is a dictionary pattern of each character constituting the plurality of items and a collective list which is a combination list of each character of the individual dictionary which is a combination existing in each of the plurality of items are read. Steps and
Creating a collective dictionary which is a dictionary pattern of a combination of characters present in each of the plurality of items by combining each character of the individual dictionary based on the collective list stored in the dictionary medium. A recording medium characterized by recording information. A recording medium recording the collective dictionary creation / collation program according to claim 3 ,
Photographing the license plate;
Cutting out each character constituting the license plate from the license plate;
Separating characters cut out from the license plate for each of the plurality of items,
A step of collectively collating all of the characters constituting the item with the collective dictionary for each of the plurality of items. A recording medium recording the collective dictionary creation / collation program according to claim 4 ,
Recording a program having a step of collating all of the characters constituting the item with the collective dictionary for each of the plurality of items and collating each character cut out from the license plate with the individual dictionary. Characteristic recording medium.

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