JP6945490B2 - License plate classification device, license plate classification system and license plate classification program - Google Patents

Description

The present invention relates to a technique for determining the type of vehicle.

Conventionally, it has been possible to determine the type of vehicle with an infrared camera.
Specifically, by determining whether the background of the license plate is white or black based on the infrared image, it is possible to determine whether the vehicle reflected in the infrared image is a business vehicle or a private vehicle. there were.

Patent Document 1 describes that when a plurality of character recognition candidates are obtained as vehicle use codes from the license plate, the vehicle use code is specified from the plurality of character recognition candidates based on the color of the license plate. There is.

Japanese Unexamined Patent Publication No. 2011-11340

In recent years, license plates with patterns have been introduced.
On the license plate with the design, the design is drawn using a paint that reflects infrared rays. Therefore, in the infrared camera, both the background of the business plate with the design and the background of the private plate with the design or no design appear white. As a result, it is no longer possible to identify a commercial vehicle with a license plate with a design using an infrared camera.

An object of the present invention is to make it possible to identify a commercial vehicle to which a license plate with a design is attached.

The license plate classification device of the present invention
A background color determination unit that determines whether the background color of the license plate is a commercial plate color based on an infrared image showing the license plate, and
A frame determination unit that determines whether the license plate has a commercial plate frame based on a color image showing the license plate, and a frame determination unit.
When the background color of the license plate is determined to be the business plate color, the license plate is classified as a non-designed business plate, and the background color of the license plate is not the business plate color. It is provided with a classification unit that classifies the license plate into a business plate with a pattern when it is determined that the license plate has a business plate frame.

According to the present invention, it is possible to identify a commercial vehicle to which a license plate with a design is attached.

The block diagram of the license plate classification system 200 in Embodiment 1. FIG. The block diagram of the license plate classification apparatus 100 in Embodiment 1. FIG. The flowchart of the license plate classification method in Embodiment 1. The flowchart of the license plate classification process (S110) in Embodiment 1.

In embodiments and drawings, the same elements and corresponding elements are designated by the same reference numerals. The description of the elements with the same reference numerals will be omitted or abbreviated as appropriate. The arrows in the figure mainly indicate the flow of data or the flow of processing.

Embodiment 1.
The form of classifying the photographed license plates will be described with reference to FIGS. 1 to 4.

*** Explanation of configuration ***
The configuration of the license plate classification system 200 will be described with reference to FIG.
The license plate classification system 200 includes a license plate classification device 100, an infrared camera 220, a lens 221 and a color camera 230, a lens 231 and an illumination 240.

The infrared camera 220 is an infrared camera for photographing the vehicle 210 within the photographing range.
The lens 221 is a lens for the infrared camera 220.
The solid line from the lens 221 represents the field of view of the infrared camera 220, that is, the shooting range of the infrared camera 220.
An infrared camera in which the infrared camera 220 and the lens 221 are integrated may be used.

The color camera 230 is a color camera for photographing the vehicle 210 within the photographing range.
The lens 231 is a lens for the color camera 230.
The broken line from the lens 231 represents the field of view of the color camera 230, that is, the shooting range of the color camera 230.
A color camera in which the color camera 230 and the lens 231 are integrated may be used.

The illumination 240 is an illumination for illuminating the photographing range of the infrared camera 220 and the photographing range of the color camera 230.
The dotted line from the illumination 240 represents the irradiation range of the illumination 240.
The shooting range of the infrared camera 220, the shooting range of the color camera 230, and the irradiation range of the illumination 240 almost overlap.

The license plate classification device 100 is a device for classifying the license plate 211 of the vehicle 210 and outputting the classification result.

The configuration of the license plate classification device 100 will be described with reference to FIG.
The license plate classification device 100 is a computer including hardware such as a processor 101, a memory 102, an auxiliary storage device 103, and an input / output interface 104. These hardware are connected to each other via signal lines.

The processor 101 is an IC (Integrated Circuit) that performs arithmetic processing, and controls other hardware. For example, the processor 101 is a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or a GPU (Graphics Processing Unit).
The memory 102 is a volatile storage device. The memory 102 is also called a main storage device or a main memory. For example, the memory 102 is a RAM (Random Access Memory). The data stored in the memory 102 is stored in the auxiliary storage device 103 as needed.
The auxiliary storage device 103 is a non-volatile storage device. For example, the auxiliary storage device 103 is a ROM (Read Only Memory), an HDD (Hard Disk Drive), or a flash memory. The data stored in the auxiliary storage device 103 is loaded into the memory 102 as needed.
The input / output interface 104 is an interface to which the infrared camera 220, the color camera 230, the lighting 240, and other devices are connected. For example, the input / output interface 104 is a port. For example, other devices are computers or communication devices.

The license plate classification device 100 includes elements such as a control unit 111, an image reception unit 112, a search unit 113, a recognition unit 114, a background color determination unit 115, a frame determination unit 116, a design determination unit 117, a classification unit 118, and an output unit 119. Be prepared. These elements are realized in software.

The auxiliary storage device 103 includes a computer as a control unit 111, an image reception unit 112, a search unit 113, a recognition unit 114, a background color determination unit 115, a frame determination unit 116, a symbol determination unit 117, a classification unit 118, and an output unit 119. A license plate classification program for functioning is stored. The license plate classification program is loaded into the memory 102 and executed by the processor 101.
Further, the auxiliary storage device 103 stores an OS (Operating System). At least part of the OS is loaded into memory 102 and executed by processor 101.
That is, the processor 101 executes the license plate classification program while executing the OS.
The data obtained by executing the license plate classification program is stored in a storage device such as a memory 102, an auxiliary storage device 103, a register in the processor 101, or a cache memory in the processor 101.

The memory 102 functions as a storage unit 120 for storing various data used in the license plate classification device 100. However, another storage device may function as the storage unit 120 instead of the memory 102 or together with the memory 102.

The license plate classification device 100 may include a plurality of processors that replace the processor 101. The plurality of processors share the role of the processor 101.

The license plate classification program can record (store) on a non-volatile recording medium such as an optical disk or a flash memory so that it can be read by a computer.

*** Explanation of operation ***
The operation of the license plate classification device 100 corresponds to the license plate classification method. In addition, the procedure of the license plate classification method corresponds to the procedure of the license plate classification program.

The license plate classification method will be described with reference to FIG.
In step S101, the control unit 111 causes the infrared camera 220 and the color camera 230 to take a picture by controlling the infrared camera 220, the color camera 230, and the illumination 240.

Specifically, the control unit 111 transmits a timing signal to the infrared camera 220, the color camera 230, and the illumination 240 at a predetermined timing or an arbitrary timing. The timing signal is a signal for operating the infrared camera 220, the color camera 230, and the illumination 240 at the same timing.
When the illumination 240 receives the timing signal, the illumination 240 illuminates the irradiation range by emitting light.
When the infrared camera 220 receives the timing signal, the infrared camera 220 takes a picture of the shooting range.
When the color camera 230 receives the timing signal, the color camera 230 takes a picture of the shooting range.

In step S102, the image receiving unit 112 receives the infrared image obtained by the infrared camera 220.
Specifically, the infrared camera 220 transmits an infrared image, and the image receiving unit 112 receives the infrared image.
The infrared image is an image obtained by taking a picture with the infrared camera 220. The infrared image shows the shooting range of the infrared camera 220.

Further, the image receiving unit 112 receives the color image obtained by the color camera 230.
Specifically, the color camera 230 transmits a color image, and the image receiving unit 112 receives the color image.
The color image is an image obtained by taking a picture with the color camera 230. The color image shows the shooting range of the color camera 230.

In step S103, the search unit 113 finds the plate portion from the infrared image by performing image processing on the infrared image.
The plate portion is a portion where the license plate 211 is reflected.

Further, the search unit 113 finds the plate portion from the color image by performing image processing on the color image.

The image processing in step S103 is also called a cutting process.

In step S104, the search unit 113 determines whether the plate portion is found in each of the infrared image and the color image.
When the plate portion is found in each of the infrared image and the color image, the process proceeds to step S105.
If the plate portion is not found in at least one of the infrared image and the color image, the process proceeds to step S107.

In step S105, the recognition unit 114 obtains the description information of the license plate 211 from the infrared image by performing image processing on the infrared image.
Specifically, the recognition unit 114 performs character recognition processing on the plate portion of the infrared image. As a result, the description information indicating the number written on the license plate 211 and the characters written on the license plate 211 can be obtained.

In step S110, the license plate classification device 100 performs the license plate classification process.
The license plate classification process is a process for classifying the license plate 211.
The license plate classification process (S110) will be described later.
After step S110, the process proceeds to step S106.

In step S106, the output unit 119 outputs the classification result of the license plate 211 and the description information of the license plate 211.
Specifically, the output unit 119 transmits the classification result of the license plate 211 and the description information of the license plate 211 to a specific device. For example, a particular device is a computer in a system that monitors the vehicle 210.
Further, the output unit 119 may output an infrared image and a color image.

In step S107, the control unit 111 determines whether to stop the processing of the license plate classification method.
For example, the control unit 111 determines whether to stop the processing of the license plate classification method based on whether or not the stop command has been input to the license plate classification device 100 or whether or not the stop time has come.
If it is determined that the processing of the license plate classification method is stopped, the processing ends.
If it is determined that the process of the license plate classification method is not stopped, the process proceeds to step S101.

The license plate classification process (S110) will be described with reference to FIG.
In step S111, the background color determination unit 115 determines whether the background color of the license plate 211 is the commercial plate color based on the infrared image.
The background color of the license plate 211 is the color of the portion (background) on which numbers or letters are not described.
The business plate color is a color defined as the background color of the business plate without a pattern. Specifically, the commercial plate color is black or dark green.
The business plate is a license plate attached to a business vehicle, and is also called a business license plate.

Specifically, the background color determination unit 115 determines whether the background color of the license plate 211 is closer to black or white by analyzing the plate portion of the infrared image.
When the background color of the license plate 211 is close to black, the background color determination unit 115 determines that the background color of the license plate 211 is the commercial plate color.
When the background color of the license plate 211 is close to white, the background color determination unit 115 determines that the background color of the license plate 211 is the private plate color.
The private plate color is a color defined as the background color of the private plate. Specifically, the color of the private plate is white or yellow.
The private plate is a license plate attached to a private vehicle, and is also called a private license plate.

When the background color of the license plate 211 is the business plate color, the process proceeds to step S112.
If the background color of the license plate 211 is not the business plate color, the process proceeds to step S113.

In step S112, the classification unit 118 classifies the license plate 211 into a symbolless business plate.
A business plate without a design is a business plate on which no design is drawn.
After step S112, the license plate classification process (S110) ends.

In step S113, the frame determination unit 116 determines whether the license plate 211 has a business plate frame based on the color image.
The business plate frame is a frame defined as a frame possessed by a business plate with a pattern, and is painted in a specified color. Specifically, the color of the commercial plate frame is green.

Specifically, the frame determination unit 116 determines whether the license plate 211 has a green frame by analyzing the plate portion of the color image.
When the license plate 211 has a green frame, the frame determination unit 116 determines that the license plate 211 has a business plate frame.
When the license plate 211 does not have a green frame, the frame determination unit 116 determines that the license plate 211 does not have a business plate frame.

If the license plate 211 has a commercial plate frame, the process proceeds to step S114.
If the license plate 211 does not have a commercial plate frame, the process proceeds to step S115.

In step S114, the classification unit 118 classifies the license plate 211 into a pattern-filled business plate.
A business plate with a design is a business plate on which a design is drawn. The design is drawn on a commercial plate using a paint that reflects infrared light.
After step S114, the license plate classification process (S110) ends.

In step S115, the symbol determination unit 117 determines whether the license plate 211 has a symbol based on the color image.

Specifically, the classification unit 118 determines whether the license plate 211 has a symbol by analyzing the color image.

If the license plate 211 has a symbol, the process proceeds to step S116.
If the license plate 211 has no symbol, the process proceeds to step S117.

In step S116, the classification unit 118 classifies the license plate 211 into a private plate with a pattern.
A private plate with a design is a private plate on which a design is drawn. The design is drawn on a private plate using a paint that reflects infrared rays.
After step S116, the license plate classification process (S110) ends.

In step S117, the classification unit 118 classifies the license plate 211 into a plate for private use without a symbol.
A private plate without a design is a private plate on which no design is drawn.
After step S117, the license plate classification process (S110) ends.

*** Effect of Embodiment 1 ***
The license plate 211 can be classified into any of a business plate with a design, a business plate without a design, a private plate with a design, and a private plate without a design.
This makes it possible to determine the type of vehicle 210. For example, it is possible to identify a commercial vehicle having a license plate with a pattern.

*** Other configurations ***
In step S104 (see FIG. 3), when the plate portion is not found in the color image but the plate portion is found in the infrared image, the license plate classification device 100 executes steps S105, a part of step S110, and step S106. You may. In this case, the license plate classification device 100 executes step S111 and step S112 as a part of step S110 (see FIG. 4).

If the plate portion is not found in the infrared image but the plate portion is found in the color image in step S104 (see FIG. 3), the license plate classification device 100 may execute step S105, step S110, and step S106. good. In this case, the license plate classification device 100 determines the background color of the license plate based on the color image in step S111 (see FIG. 4).

The license plate classification device 100 may operate without using an infrared image.
In this case, the license plate classification device 100 obtains the description information of the license plate 211 from the color image in step S105 (see FIG. 3). Further, the license plate classification device 100 determines the background color of the license plate based on the color image in step S111 (see FIG. 4).

The infrared camera 220, the color camera 230, and the illumination 240 may operate in synchronization with each other regardless of the control of the control unit 111. For example, instead of the control unit 111, either the infrared camera 220, the color camera 230, or the illumination 240 may transmit a timing signal.

The timing at which the timing signals are transmitted to the infrared camera 220, the color camera 230, and the illumination 240 may be simultaneous or may be shifted.
The timing signal may be simultaneously transmitted to the infrared camera 220, the color camera 230, and the illumination 240, and the timing of operation may be shifted between the infrared camera 220, the color camera 230, and the illumination 240.

The control unit 111 may analyze the brightness of each of the infrared image and the color image, and determine the necessity of light emission based on the analysis result. When the light emission is unnecessary, the control unit 111 stops the operation of the illumination 240. For example, the control unit 111 does not transmit the timing signal to the illumination 240 from the next time onward.

*** Supplement to the embodiment ***
The embodiments are examples of preferred embodiments and are not intended to limit the technical scope of the invention. The embodiment may be partially implemented or may be implemented in combination with other embodiments. The procedure described using the flowchart or the like may be appropriately changed.

100 license plate sorter, 101 processor, 102 memory, 103 auxiliary storage device, 104 input / output interface, 111 control unit, 112 image reception unit, 113 search unit, 114 recognition unit, 115 background color determination unit, 116 frame determination unit, 117 Design judgment unit, 118 classification unit, 119 output unit, 120 storage unit, 200 license plate classification system, 210 vehicle, 211 license plate, 220 infrared camera, 221 lens, 230 color camera, 231 lens, 240 lighting.

Claims (7)

A background color determination unit that determines whether the background color of the license plate is a commercial plate color based on an infrared image showing the license plate, and
A frame determination unit that determines whether the license plate has a commercial plate frame based on a color image showing the license plate, and a frame determination unit.
When the background color of the license plate is the business plate color, the license plate is classified into a designless business plate, and the license plate is not the business plate color but the license plate When the license plate has the business plate frame, the license plate is classified into a business plate with a pattern, and the background color of the license plate is not the business plate color and the license plate does not have the business plate frame. A license plate classification device including a classification unit that classifies the license plate into a private plate in some cases. When the background color of the license plate is determined not to be the business plate color based on the infrared image, the frame determination unit has the license plate having the business plate frame based on the color image. The license plate classification device according to claim 1. The license plate classification device further
A symbol determination unit for determining whether the license plate has a symbol based on the color image is provided.
The classification unit
When the background color of the license plate is not the color of the business plate and the license plate does not have the business plate frame and the license plate has a design, the license plate is classified as a private plate with a design.
When the background color of the license plate is not the color of the business plate and the license plate does not have the business plate frame and the license plate has no design, the license plate is classified as a private plate without a design. The license plate classification device according to claim 1. When the background color of the license plate is determined not to be the business plate color based on the infrared image, the frame determination unit has the license plate having the business plate frame based on the color image. Judge
A claim that the symbol determination unit determines whether the license plate has a symbol based on the color image when it is determined that the license plate does not have the business plate frame based on the color image. The license plate classification device according to 3. The license plate classification device further
A control unit that controls an infrared camera and a color camera,
1 to claim 1, further comprising an image receiving unit that receives an image obtained by photographing a vehicle with the infrared camera as the infrared image and receives an image obtained by photographing the vehicle with the color camera as the color image. The number plate classification device according to any one of claims 4. An infrared camera that obtains an infrared image by taking a picture of the vehicle,
A color camera that obtains a color image by photographing the vehicle, and
Equipped with a license plate sorting device
Based on the infrared image, the license plate classification device determines whether the background color of the license plate reflected in the infrared image is the commercial plate color, and a background color determination unit.
A frame determination unit that determines whether the license plate shown in the color image has a commercial plate frame based on the color image, and
When the background color of the license plate is the business plate color, the license plate is classified into a designless business plate, and the license plate is not the business plate color but the license plate When the license plate has the business plate frame, the license plate is classified into a business plate with a pattern, and the background color of the license plate is not the business plate color and the license plate does not have the business plate frame. A license plate classification system including a classification unit that classifies the license plate into a private plate in some cases. A background color determination unit that determines whether the background color of the license plate is a commercial plate color based on an infrared image showing the license plate, and
A frame determination unit that determines whether the license plate has a commercial plate frame based on a color image showing the license plate, and a frame determination unit.
When the background color of the license plate is the business plate color, the license plate is classified into a designless business plate, and the license plate is not the business plate color but the license plate When the license plate has the business plate frame, the license plate is classified into a business plate with a pattern, and the background color of the license plate is not the business plate color and the license plate does not have the business plate frame. A license plate classification program for operating a computer as a classification unit that classifies the license plate into a private plate in some cases.

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