JPH08329382A - Vehicle license plate automatic recognition device - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention relates to an automatic license plate recognition device for an automobile, which is easy to install and can surely recognize a license plate. [Structure] The radar unit 1 and the photographing unit 4 are integrated and installed on the side of the road. The radar unit 1 radiates radio waves in the direction of the road to search for a vehicle. Then, the distance to the discovered vehicle is calculated and output to the recognition device 3.
The recognition device 3 determines the zoom magnification according to this distance by referring to the table 30, and outputs this to the photographing unit 4. The photographing unit 4 photographs the vehicle at the instructed zoom magnification and outputs the photographing data to the recognition device 3. The recognition device 3 reads the license plate from this data.
If the image cannot be read, the zoom magnification and the like are determined again, and then the image capturing is performed again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic license plate recognizing device for a vehicle, which is used in an automatic tollgate on a highway.

[0002]

2. Description of the Related Art A device for automatically recognizing a license plate of a vehicle is used in an automatic tollgate on a highway. An example of such a device is disclosed in Japanese Patent Laid-Open No. 61-2.
There is a "vehicle license plate reader" disclosed in No. 13999. The outline of this conventional technique is shown below in FIG.
Will be explained.

This license plate reading device is composed of a vehicle detector and a photographing device.

The vehicle detector is installed at a pre-installed gate with its sensitivity direction oriented substantially perpendicular to the traveling direction of the vehicle. When it is detected that the vehicle has passed through this gate, the image capturing device is informed accordingly. Let me know. The photographing device that has received this notification photographs the vehicle and supplies the image data obtained by this photographing to an image processing device (not shown). Then, the number of the vehicle is recognized by the image processing of the image processing device.

In this case, the photographing device is installed at a position separated from the gate by a distance sufficient to photograph a vehicle passing through the gate.

[0006]

However, in the above-mentioned prior art, since the vehicle detector and the photographing device are installed separately, the installation work was very troublesome.

[0007] Further, the chance of photographing by the photographing device is
It is limited to one time. Therefore, for example, if the photographing fails due to a sudden change in the photographing environment, backlighting, or the like, there is a problem that the license plate can no longer be recognized for the vehicle.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an automatic license plate recognizing device for a vehicle, which can be easily installed.

Another object of the present invention is to provide an automatic license plate recognizing device for a vehicle which can more reliably recognize the vehicle number.

[0010]

In order to achieve the above-mentioned object, the invention of claim 1 is a detection device for detecting the presence / absence of a vehicle in a detection target area, and a vehicle when the detection device detects the vehicle. Is a photographing device for photographing a photographing target region including at least a part of the detection target region, and photographing data obtained by the photographing device,
A recognition device for recognizing characters drawn on a license plate of the vehicle, and at least the photographing device and the detection device are integrated.

According to a second aspect of the present invention, a detection device for detecting the presence / absence of a vehicle in the detection target region, and when a vehicle is detected by the detection device, the detection device is set to include at least a part of the detection target region. A photographing device for photographing the photographed target region, and a recognition device for recognizing the characters drawn on the license plate of the vehicle by using the photographed data obtained by the photographing device. The longitudinal direction and the longitudinal direction of the detection target region are substantially the same direction.

According to a third aspect of the invention, in the automatic license plate recognizing device for a vehicle according to the first or second aspect, when the recognizing device cannot recognize the character, the photographic device re-photographs. It is characterized by making it.

The invention of claim 4 is the invention of claim 1, 2 or 3.
In the license plate automatic recognition device of the vehicle described,
The distance measuring device that measures the distance to the vehicle discovered by the detection device, and a parameter determining unit that determines a photographing parameter according to the distance measured by the distance measuring device, the photographing device, The photographing target area is configured to be changeable, and the photographing target area is changed according to the photographing parameter obtained by the parameter determining means.

According to a fifth aspect of the present invention, in the automatic license plate recognition apparatus for a vehicle according to the fourth aspect, the photographing parameter is a photographing magnification, and the photographing apparatus includes a zoom mechanism for changing the photographing magnification, and the photographing is performed. It is characterized in that the target area is changed including a change of the photographing magnification according to the photographing magnification obtained by the parameter determining means.

[0015]

When the license plate automatic recognition device is installed near a road, the installation work is simplified because the detection device and the photographing device are integrated in the present invention.

When the detection device (for example, including a radar) detects the presence / absence of a vehicle in the detection target area, the distance measuring device measures the distance to the vehicle found by the detection device. . Subsequently, the parameter determination unit determines a shooting parameter (for example, shooting magnification) according to the distance measured by the distance measuring device. The photographing apparatus changes the photographing target area according to the photographing parameter and then performs photographing. The imaging target area includes at least a part of the detection target area.

The recognition device recognizes the characters drawn on the license plate of the vehicle using the photographing data obtained by the photographing device. If the character cannot be recognized, the recognition device instructs the photographing device to re-photograph. The photographing device again photographs.

In the present invention, the longitudinal direction of the detection target area of the detection device and the longitudinal direction of the imaging target area of the imaging device are substantially the same direction. Moreover, both are arranged close to each other. Therefore, the range in which the vehicle can be detected and photographed is wide. As a result, the moving vehicle can be detected and photographed multiple times.

[0019]

An embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the automatic license plate recognition apparatus 1 of the present embodiment includes a radar unit 2, a license plate recognition apparatus 3, and a photographing unit 4.

The radar unit 2 includes a control calculation unit 20 and
As shown in FIG. 2, the radar transmitting / receiving unit 22 and the scan driving unit 24 are used to radiate radio waves or the like in the direction of the road r (that is, the traveling direction of the vehicle c), and the irradiation direction is the width of the road. The presence or absence of a vehicle is detected by scanning.

The radar transmission / reception unit 22 generates a laser radar, a millimeter wave radar or the like according to an instruction from the control calculation unit 20, irradiates the same in a predetermined direction, and detects a reflected wave of the irradiated laser or the like. It has a function to do.
The radar transmission / reception unit 22 has a sufficient output and detection sensitivity for the purpose of the present invention, and can also sufficiently detect reflection from an object (here, vehicle c) at a distance to some extent. ing. The type of radar actually used may be selected and adopted in consideration of the use environment, the search range, and the like.

The scan driving section 24 is for automatically scanning the direction of the radar transmitting / receiving section 22, that is, the direction of the radio wave to be emitted, within a preset angle range in accordance with an instruction from the control calculating section 20. And the control calculation unit 20
It is equipped with a motor, etc. that operates according to the instructions from.

The control arithmetic unit 20 is a microprocessor,
It is configured to include a memory and software, and integrally controls the operations of the radar transmitter / receiver 22 and the scan driver 24 described above. The control calculation unit 20 also has a function of obtaining the presence or absence of a vehicle and the detected distance to the vehicle by performing a predetermined calculation using the detection result input from the radar transmission / reception unit 22 as input data. The control calculation unit 20 outputs the obtained distance to the license plate recognition device 3. Although not shown in the figure, the control calculation unit 20 also includes an input device (for example, a keyboard) for inputting irradiation output of a laser or the like, various set values such as a scanning range angle, conditions, and the like. There is.

The photographing unit 4 includes a zoom controller 40 and
It is composed of an image data creation / transmission unit 42 and a camera 44, and photographs the vehicle detected by the radar unit 2 at a magnification most suitable for recognizing the license plate. Further, in this embodiment, the image pickup unit 4 and the radar unit 2 are housed in the case 5 so that they are integrated (see FIG. 2). Therefore, it is not necessary to install these separately, and the amount of installation work can be small.

The camera 44 is a CCD camera, which photographs the vehicle and outputs the image as electrical image data to the image data creation / transmission section 42. The optical system of the camera 44 has a central direction of light incident on the optical system from the outside (the “longitudinal direction of the photographing target area” in the claims).
Is equivalent to ) Is substantially aligned with the center direction (longitudinal direction) of the range in which the radar transmitter / receiver 22 irradiates the laser (corresponding to the “detection target area” in the claims), and the search for the radar unit 2 is performed. The range is included in the shooting area of the camera 44. The optics design virtually eliminates the need for focusing operations. The optical system also has a zoom function. Regarding the zoom function, CC
If D has a sufficient number of pixels, it can be replaced by trimming in image processing.

The zoom control section 40 comprises a motor and the like and a control circuit therefor, and drives the optical system of the camera 44 to change the zoom magnification thereof. The zoom magnification set by the zoom control unit 40 is instructed from the license plate recognition device 3.

The image data creation / transmission unit 42 is configured to include a memory and the like, and converts the image data obtained by the camera 44 into a data format that can be processed by the license plate recognition device 3 and outputs it.

The license plate recognition device 3 includes a distance-magnification table 30, a zoom magnification determination section 32, and a recognition section 3.
And image processing for determining the photographing magnification and recognizing the license plate.

The distance-magnification table 30 is a table in which the distance to the object to be photographed and the zoom magnification most suitable for photographing are stored in association with each other. This distance-magnification table 3
0 is prepared in advance in the memory.

The zoom magnification determining section 32 obtains a zoom magnification most suitable for photographing at that time in accordance with the distance information input from the radar unit 2. The zoom magnification determination unit 32 of this embodiment obtains this zoom magnification by referring to the distance-magnification table 30. The obtained zoom magnification is output to the recognition unit 34 and the zoom control unit 40 described above.

The recognition unit 34 includes an image data creation / transmission unit 42.
By performing a predetermined process (for example, binarization process) on the image data input from, the license plate portion is extracted from the image data, and the characters written on the license plate portion are read. The recognition unit 34 includes a zoom magnification determination unit 3
Since the determined zoom magnification of 2 is input, the recognition unit 34 can know in advance the size of the license plate on the imaged screen and the characters drawn on the license plate. Thereby, the speed of image processing and the recognition accuracy are improved.

Further, when the recognition unit 34 cannot recognize the image, the zoom ratio determination unit 32 is requested to re-determine the zoom magnification in preparation for re-photographing.

The recognition unit 34 outputs the recognized number to an external device such as an automatic fee collection system.

It should be noted that all of the respective parts constituting the automatic license plate recognition apparatus 1 are designed to be operable at a speed sufficient for photographing a vehicle traveling within the detection range of the radar unit 2 a plurality of times. Needless to say.

Here, the "detection device" in the claims corresponds to the radar unit 2 in this embodiment, and the "imaging device" corresponds to the imaging unit 4. The “recognition device” corresponds to the license plate recognition device 3.
Further, the “distance measuring device” corresponds to the radar unit 2 (in particular, the radar transmitting / receiving unit 22 and the control calculation unit 20). ”
The “parameter determining means” corresponds to the zoom magnification determining unit 32, and the “shooting parameter” is the zoom magnification (shooting magnification) in this embodiment.

Next, the operation of this embodiment will be described with reference to FIGS. When the radar unit 2 detects the vehicle c, the license plate recognition device 3 appropriately determines the zoom magnification according to the distance information from the radar unit 2 to the vehicle c, and the photographing unit 4 performs photographing at this magnification. Let The license plate recognition device 3 recognizes the license plate using the photographing data of the photographing unit 4. As a result, when the photographed image is good and the license plate can be recognized, the photographing of the vehicle c ends. On the contrary, if the license plate cannot be recognized because the captured image is defective, the photographing unit 4 is instructed to photograph the vehicle c again. In this case, the vehicle c is moving after the first shooting. Therefore, the license plate recognition device 3 determines the zoom magnification again based on the distance information from the radar unit 2. Hereinafter, the same processing is repeated until the license plate can be recognized.

Next, the operation of the radar unit 2 will be described in detail with reference to FIG.

After the operation is started, the control calculation section 20 outputs an operation start instruction and an operation condition (for example, output, scanning range) to the radar transmitting / receiving section 22 and the scan driving section 24. In response to this, the radar transmitting / receiving unit 22 starts irradiation of the laser and detection of the reflected wave thereof. Further, the scan driver 24 is
Scanning is performed by changing the direction of the radar transmitting / receiving unit 22 (step 300). In parallel with this, the control calculation unit 20
The analysis of the signal detected by the radar transmitter / receiver 22 is started (step 302). If the result of this analysis is that a reflected wave is included, then the distance d to the object that caused this reflected wave is calculated (step 304). Furthermore, the detection target area set at this time (here, 1
Whether or not this object exists within the range of 0 m or more and 100 m or less) is determined based on the size of d (step 306). If it is within the detection target area, the distance d obtained in step 304 is output to the zoom magnification determination unit 32 of the license plate recognition device 3. After that, the process returns to step 300 and the same processing is repeated.

If the reflected wave is not included in step 302, or if it is outside the detection target area in step 306, step 3 is performed as it is.
Returning to 00, the same processing is repeated.

Next, the operation of the license plate recognition device 3 will be described in detail with reference to FIG. After the operation is started, the zoom magnification determination unit 32 is in a standby state waiting for the input of the distance d from the radar unit 2 (step 400). When the distance d is input, the zoom magnification determination unit 32 obtains the zoom magnification value z corresponding to the input distance d by referring to the distance-magnification table 30 (step 40).
2). Then, the value z is output to the photographing unit 4 together with the photographing execution instruction (step 404).

The photographing unit 4 receiving this photographing instruction,
Photographing is performed at the input zoom magnification z, and the photographing data is output to the license plate recognition device 3. The photographing operation of the photographing unit 4 will be described later in detail with reference to FIG.

Although not clearly shown in FIG. 4, step 404
After that, the license plate recognition device 3 is connected to the photographing unit 4
It is in a standby state waiting for the input of image data from. When this image data is input, the recognition unit 34 executes the process of reading the characters on the license plate from this image data (step 408). Then, it is determined whether the character can be recognized (step 410). When the character can be recognized, the recognition unit 34 outputs the recognized character to a predetermined external device, and ends the photographing process for the vehicle c (step 412). After this, the license plate recognition device 3 returns to step 400 and prepares for photographing the next vehicle.

On the other hand, if it is determined in step 410 that the character cannot be recognized, the license plate recognition device 3 returns to step 400 in order to perform re-imaging.

Next, the operation of the photographing unit 4 will be described with reference to FIG. After the operation starts, the photographing unit 4 receives the photographing instruction from the license plate recognition device 3 and the zoom magnification z.
Waiting for input of (step 50
0). The shooting instruction and the like are output in step 402 of FIG.

When a photographing instruction or the like is input, the zoom control section 40 drives the optical system of the camera 44 to set the photographing magnification to the instructed value z (step 502). Subsequently, the camera 44 takes an image (step 504) and outputs the image data to the image data creation / transmission unit 42. The image data creation / transmission unit 42 converts the shooting data into predetermined data, and then outputs the data to the recognition unit 34 of the license plate recognition device 3 (step 506). After this, the photographing unit 4
Returns to step 500 in preparation for the next image capture (image capture of the next vehicle or re-image capture of this vehicle c).

According to the embodiment described above, since the same vehicle can be photographed a plurality of times, the license plate can be surely recognized.

Further, the radar unit 2 and the photographing unit 4
Since and are integrated, the amount of installation work is small. However, the radar unit 2 and the imaging unit 4 do not necessarily have to be integrated as a whole. If at least the radar transmission / reception unit 22 of the radar unit 2 and the camera 44 of the imaging unit 4 are integrated, the object of facilitating the installation work of the present invention can be achieved (Note: for other parts, Other structural members, because it does not need to be fixed to the ground, installation work is not required). Furthermore, the radar transmitter / receiver 22 and the camera 44 do not necessarily have to be integrated. In the present invention, since the radar transmitter / receiver 22 and the camera 44 are installed at substantially the same position, the object of facilitating the installation work can be achieved to some extent even if they are separately configured. For example, the work of arranging the cables connecting them is almost unnecessary. As used herein, "integrated" includes not only the case where two objects are directly connected, but also the case where they are structurally connected via one or more other members. Therefore, as in the above-described embodiment, the state in which the radar transmitting / receiving unit 22 and the camera 44 of the photographing unit 4 are housed in the same case, or the state indicated by the same supporting member is included. It is a concept.

In the above embodiment, the zoom magnification is obtained using the distance-magnification table. However, instead of this, a function that describes the relationship between the two (distance, zoom magnification) may be used. By doing so, the zoom magnification can be finely set without increasing the memory usage.

In the above-described embodiment, the photographing is performed again only when the license plate cannot be recognized. However, it is also possible to take a plurality of shots without fail. In this way, the time required for one shooting and its preparation operation can be lengthened by the processing time in the license plate recognition device 3. By doing so, it is possible to use a component having a slow response speed, and it is possible to reduce the cost. However, in this case, it is necessary to provide the license plate recognition device 3 or the photographing unit 4 with a storage device capable of storing images for a plurality of screens. The storage device in this case does not need to have the high speed of the semiconductor memory, and a magnetic disk device or the like can be used.

The camera 44 described above has a design in which the focusing is virtually unnecessary in the optical system. However, the camera 44
May have an autofocus function. In this case, the autofocus function of the camera 44 can replace the role of the radar unit 2 described above, and the independent radar unit 2 can be eliminated.

In the above embodiment, only the zoom magnification of the camera 44 is changed. However, the camera 44
The direction of may also be changed according to the distance to the vehicle and the position of the vehicle (in particular, the position in the road width direction).

[0052]

As described above, according to the present invention, since the same vehicle can be photographed a plurality of times, it is possible to avoid the situation that the photographing is not successful due to some reason and the license plate cannot be recognized. Further, since the functional part for detecting the vehicle and the functional part for photographing the vehicle are integrated, there is an effect that the installation work is simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a vehicle license plate automatic recognition apparatus according to the present invention.

FIG. 2 is a perspective view for explaining the outline of the embodiment shown in FIG.

FIG. 3 is a flowchart showing an operation example of the radar unit 2.

FIG. 4 is a flowchart showing an operation example of the license plate recognition device 3.

FIG. 5 is a flowchart showing an operation example of the photographing unit 4.

FIG. 6 is a perspective view showing an outline of a conventional technique.

[Explanation of symbols]

 1 Automatic license plate recognition device 2 Radar unit 3 License plate recognition device 4 Imaging unit 5 Case 20 Control calculation unit 22 Radar transmitter / receiver unit 24 Scan drive unit 30 Distance-magnification table 32 Zoom magnification determination unit 34 Recognition unit 40 Zoom control unit 42 Image Data creation / transmission section 44 Camera c Vehicle g Gate r Road

Claims (5)

[Claims] 1. A detection device for detecting the presence / absence of a vehicle in the detection target region, and an imaging target region set including at least a part of the detection target region when the detection device detects the vehicle. And a recognition device for recognizing the characters drawn on the license plate of the vehicle by using the photographing data obtained by the photographing device, and at least the photographing device and the detection device. Is an integrated license plate automatic recognition device for vehicles. 2. A detection device for detecting the presence or absence of a vehicle in the detection target region, and a photographing target region set including at least a part of the detection target region when the detection device detects the vehicle. And a recognition device for recognizing the characters drawn on the license plate of the vehicle by using the photographing data obtained by the photographing device, and the longitudinal direction of the photographing target region, and The automatic license plate recognition device for a vehicle, wherein the longitudinal direction of the detection target area is substantially the same direction. 3. The automatic license plate recognition device for a vehicle according to claim 1, wherein the recognition device causes the photographing device to re-photograph when the character cannot be recognized. . 4. A distance measuring device for measuring a distance to the vehicle discovered by the detection device, and a parameter determining means for obtaining a photographing parameter according to the distance measured by the distance measuring device, The image capturing apparatus is configured to be able to change the image capturing target area, and changes the image capturing target area in accordance with the image capturing parameters obtained by the parameter determining means. Automatic vehicle license plate recognition device. 5. The photographing parameter is a photographing magnification, the photographing apparatus includes a zoom mechanism for changing the photographing magnification, and the photographing magnification is changed according to the photographing magnification determined by the parameter determining unit for changing the photographing target area. 5. The automatic license plate recognition device for a vehicle according to claim 4, wherein