JPH07121794A - Vehicle registered number recognition device - Google Patents

Abstract

PURPOSE:To provide the vehicle registered number recognition device which is constituted including a near infrared range lighting device and can pick up an image with a proper contrast between a vehicle registered number and its background and has good recognition precision through an easy image process for all of three cases of a self-illumination type license plate in a nonillumination state and a self-illumination type license plate in an illumination state, not to mention a normal license plate. CONSTITUTION:The vehicle registered number recognition device has the near infrared range lighting device 12, a self-illumination type license plate detecting means 13, a video camera 11, and an image processing part 20A; when the self-illumination type license plate 3 in the illumination state is detected, an image is picked up without lighting in response to vehicle detection to perform vehicle registered number recognition, but an image is picked up with lighting in other cases to perform vehicle registered number recognition. In another way, the device has the near infrared range lighting device, video camera, and image processing part, an image picked up in the presence of lighting and an image picked up without lighting are both obtained in response to vehicle detection, and both the images are processed in order to perform vehicle registered number recognition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle registration number recognition apparatus for image processing using a near-infrared region lighting device as a lighting device used in a parking lot system, a traffic system and the like.

[0002]

2. Description of the Related Art In image processing, for example, in order to prevent people from noticing it in crime prevention and to prevent the vehicle driver from feeling glare in the field of road traffic, it is stable regardless of the weather. In order to obtain a shadow image, a near-infrared illumination device is often used as an illumination device to be imaged.

A near-infrared region illumination device is also used when the image signal obtained by picking up an image of a license plate of a vehicle is subjected to image processing to recognize a vehicle registration number. FIG. 7 shows an example of such a device. The device shown in FIG. 7 is a vehicle registration number recognition device for an underground parking lot, and is approximately 1
The license plate is extracted from the foreground of the automobile imaged by the camera installed at the height of m, and the vehicle registration number is recognized.

This vehicle registration number recognition device comprises a near infrared illumination device 12, a video camera 11, and an image processing section 20C to which these are connected. Also, the projector 31A
It is equipped with a vehicle head sensor composed of a light receiver 31B and a light receiver 31B, and is also connected to the image processing unit 20C.

The near-infrared region illumination device 12 has an image processing unit 20C.
The near-infrared illumination light is emitted to the vehicle traveling path by the control of.
The video camera 11 captures an image of the vehicle traveling path 1 and drives the traveling vehicle 2
To get the foreground of. The image signal from the video camera 11 is an image processing unit 20C including a CPU.
Entered in.

A vehicle head detection signal from a light receiver 31B which constitutes a vehicle head sensor together with the light projector 31A is input to the image processing section 20C. Further, a shutter signal is output to the video camera 11 and a drive signal is output to the near-infrared region lighting device 12. There are many proposals for the configuration of the image processing unit 20C, and a predetermined vehicle registration number recognition processing process is performed under the control of the CPU.

In this type of apparatus, generally, a video signal including a vehicle obtained by the image input unit is stored as a still image in the image storage unit, and then the license plate extraction unit extracts the license plate equivalent portion. Then, the binarization processing unit appropriately sets
After the binarization, the character cut-out portion extracts the character equivalent portions, and the character recognition portion character-recognizes the characters corresponding to these character equivalent portions. Note that each processing unit is generally configured as an integrated processing device.

When the foreground including the license plate portion of the vehicle is imaged by this device, a near infrared illumination device is used to obtain a stable image, and when the vehicle is detected (when the vehicle reaches a predetermined position, ) The near-infrared region lighting device is driven, and an image taken in synchronization with this is taken into the image processing unit to recognize the vehicle registration number.

Various devices for extracting license plates have been proposed, for example, the applicant of the present invention has proposed it as Japanese Patent Application No. 4-137873 (image processing device). A license plate extraction method has also been proposed, for example, by the present applicant as Japanese Patent Application Laid-Open No. 5-143888 (Japanese Patent Application No. 3-332552). In particular, an example in which the extraction accuracy is improved by paying attention to the color of the license plate portion is proposed as Japanese Patent Application No. 5-28579. Regarding the method of recognizing the vehicle registration number, for example, there is a proposal of Japanese Patent Application No. 4-137874 (a method of recognizing numbers etc.) by the applicant.

By the way, in addition to the usual painted license plate, the license plate is a license plate in which the character portion shines by itself (hereinafter referred to as a self-illuminating license plate. )
There is. This self-illuminating license plate also emits light in the near infrared region. However, in a conventional vehicle registration number recognition device using a CCD camera and a near-infrared illumination device that are sensitive to the near-infrared region, the near-infrared region is recognized for all vehicles regardless of the difference in license plates as described above. It was illuminating.

Therefore, the image obtained by illuminating the vehicle emitting the near-infrared region component from the vehicle registration number part by illuminating the self-illuminating license plate with the near-infrared region illumination light is the background of the license plate and the character region. There was a case where the vehicle registration number could not be recognized due to the lack of contrast.
As a countermeasure for this, it is possible to perform more complicated processing for character extraction, but it is difficult to say that this is an appropriate solution because the processing speed inevitably decreases and the apparatus becomes complicated.

[0012]

The respective inventions of the present application have been made in order to solve the problem that the conventional vehicle registration number recognition device cannot deal with the self-illuminating license plate as described above. Not to mention the plate,
Near-infrared region with high recognition accuracy that can be imaged with proper contrast between vehicle registration number and ground for all three cases of self-illuminating license plate when turned off and self-illuminating license plate when lit An object of the present invention is to provide a vehicle registration number recognition device including an illuminating device.

[0013]

In order to achieve the above object, in the first invention of the present application, a vehicle registration number recognition device is provided with a near-infrared region illuminating device for irradiating a near-infrared region illumination light to a vehicle traveling path, and the vehicle traveling. A self-illuminating license plate detecting means for detecting a self-illuminating license plate of a traveling vehicle on a road, a video camera for capturing an image of the traveling road of the vehicle to obtain a foreground or a rear view of the traveling vehicle, and an output of the video camera. An image processing unit for recognizing a vehicle registration number, and when the image processing unit detects a self-illuminating license plate illuminated by the self-illuminating license plate detecting means, the near-infrared lighting device responds to vehicle detection. The vehicle registration number is recognized by performing image processing on the video signal captured by the video camera without lighting by
When the illuminated self-illuminating license plate is not detected, the near-infrared illumination device is illuminated in response to vehicle detection, and the video signal captured by the video camera is image-processed to recognize the vehicle registration number. .

Further, in the second invention of the present application, the vehicle registration number recognition device is provided with a near-infrared region lighting device for irradiating the vehicle traveling road with near-infrared region illumination light, and a foreground or rear view of the traveling vehicle by imaging the vehicle traveling road. A video camera for obtaining a view, and an image processing unit for recognizing a vehicle registration number from the output of the video camera,
An image captured by a video camera in which this image processing unit performs illumination by a near-infrared illumination device in response to vehicle detection, and
Both of the images captured by the video camera without illumination are obtained, and both images are sequentially processed to recognize the vehicle registration number.

[0015]

In the first aspect of the invention, when the vehicle entering is lighting the self-illuminating license plate, the self-illuminating license plate detecting means detects this and inputs it to the image processing section. For a vehicle with self-illuminating license plate lighting, the image processing unit captures the foreground image when it detects that the vehicle has reached a fixed position without performing near-infrared illumination, and obtains a video signal with good contrast to obtain an image. Processing is performed to recognize the vehicle registration number. On the other hand, when it is detected that a vehicle other than the self-illuminating license plate lighting vehicle has reached a fixed position, the near infrared illuminating device is driven to image the foreground during illumination. A video signal with good contrast is obtained by the reflected light from the illumination, and the image signal is processed to recognize the vehicle registration number. In either case, since the image of the license plate portion with good contrast is processed, simple image processing is sufficient and recognition accuracy is improved.

According to the second aspect of the present invention, when it is detected that the approaching vehicle has reached the localization value, the near-infrared region illumination device illuminates the image and then the image is obtained without the illumination. Image processing is performed on one of the images, and if the desired vehicle registration number recognition result is obtained, the process ends, but if the desired vehicle registration number recognition result is not obtained, vehicle registration number recognition is performed on the remaining images. Since either image contains a license plate part with good contrast, simple image processing is sufficient and recognition accuracy is improved.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings based on embodiments. FIG. 1 is a block diagram showing an embodiment of a vehicle registration number recognition device of the first invention of the present application. Further, FIG. 2 is a schematic plan view of the parking lot gate portion for explaining the arrangement and the like of the apparatus of this embodiment. This vehicle registration number recognition device recognizes the vehicle registration number of a vehicle entering or leaving a parking lot, and is installed on the side of the vehicle running path 1 at the parking gate.

This vehicle registration number recognition device comprises a near infrared illumination device 12, a video camera 11, and an image processing section 20A to which these are connected. Also, the projector 31A
It is equipped with a vehicle head sensor including a light receiver 31B and a light receiver 31B, and is also connected to the image processing unit 20A. In addition, the apparatus of the embodiment is provided with the self-illuminating license plate detecting means 13 for detecting the self-illuminating license plate only when the light is turned on. In the embodiment, it is realized by performing image processing on the video signal (detailed later), and there is no special substance part. Of course, the self-lighting license plate detection means 13 may be provided with a separate appropriate device as shown by the broken line in the figure, and the output thereof may be input to the image processing unit 20A.

The near-infrared illuminating device 12 has an image processing unit 20A.
Control (described later) to illuminate the vehicle traveling path with near-infrared illumination light. The video camera 11 captures an image of the vehicle traveling path 1 and obtains the foreground of the traveling vehicle 2. The video signal from the video camera 11 is the image input unit 2 of the image processing unit 20A.
Input to 1.

The image processing unit 20A includes an image input unit 21 to which a video signal is input, an image memory 22, and this image memory 2.
2 and an image processor 23 connected by a direct bus, and a CPU that is connected to each of the above units via a CPU bus to control each unit and input / output data.
24, the CPU 24 also has an I / O circuit 25 connected to the CPU bus for inputting / outputting with the outside.

The I / O circuit 25 receives a vehicle head detection signal from a light receiver 31B which constitutes a vehicle head sensor together with the light projector 31A. Further, the I / O circuit 25 outputs a shutter signal to the video camera 11 as well as a drive signal for driving the near infrared illumination device 12.
Further, the vehicle registration number recognition result and the like obtained by the image processing are also transmitted to the remote host device via the I / O circuit 25. If the self-illuminating license plate detecting means 13 described above is used
Is a separate object, the detection signal is connected to the I / O circuit 25. The image input unit 21, the image memory 22, the image processor 23, etc. may have a known configuration, and a CPU
Under the control of 24, predetermined image processing, that is, license plate extraction, extraction of characters from the extraction unit, recognition of each character, and the like are performed.

Next, the operation of the embodiment apparatus will be described. Note that FIG. 3 shows an example of a corresponding flowchart. In the first invention of the present application, it is important that the approaching vehicle has a self-illuminating license plate attached thereto, and that the self-illuminating license plate detecting means detects that the self-illuminating license plate is in a lighting state.

In the embodiment, the lit self-illuminating license plate is detected from the video signal. Therefore, the green component of the area corresponding to the position of the license plate is extracted.
Therefore, a color camera or a color extraction camera is used as the video camera. In addition, since there is a possibility that the green component of a normal license plate may be extracted under visible light, it is necessary to make it dark so that the place where the target vehicle is photographed is not exposed to visible light. This condition is naturally satisfied in underground parking lots, etc., but in ordinary outdoor parking lots, it is possible to use a method such as establishing a tunnel in advance at the shooting position of the target vehicle so that the vehicle can pass through it. Keep it out of the light.

During operation of the apparatus, a light beam is constantly emitted from the light projector 31A toward the light receiver 31B. Light receiver 3
When light from the light projector 31A is cut off by the entering vehicle, the vehicle 1B responds to this by transmitting a signal different from that at the time of light reception (normal state). This change (rise or fall) is recognized as a vehicle head detection signal by the image processing unit 20A, and the entry of the vehicle can be recognized (FIG. 3, S1).

In the image processing section 20A, the input video signal is correspondingly image-processed to extract the luminous intensity of the green component in the region substantially corresponding to the position of the license plate. The self-illuminating license plate being lit is detected depending on whether the luminous intensity of the green component is equal to or higher than a predetermined value (S2).

When the self-illuminating license plate which is lit is detected, the image is subsequently taken in (S4). Then, based on this image, a predetermined vehicle registration number recognition process is performed (S5). Since a high-luminance image is obtained only in the light emitting portion of the self-illuminating license plate, that is, the character portion to be recognized, the vehicle registration number can be easily recognized.

However, in the above step (S2), when the self-illuminating license plate which is lit is not detected, that is, even if the target vehicle has a normal license plate or has a self-illuminating license plate attached. If not, the image processing unit 20A outputs a drive signal to the near-infrared region lighting device 12, and the near-infrared region lighting device 12 illuminates correspondingly (S3). Under this illumination, an image is captured based on the obtained video signal (S4), and then a predetermined vehicle registration number recognition process is performed (S5).

As described above, in the embodiment, in the case of a license plate coated with normal paint, when the self-illuminating license plate is turned off and when the self-illuminating license plate is turned on, the plate is used as the base of the plate in any of the three cases. The recognition algorithm is simplified because an appropriate contrast can be obtained with the character area. This also leads to improvement in recognition accuracy.

Next, the second invention of the present application will be described. FIG. 4 is a block diagram showing an embodiment of the vehicle registration number recognition device of the second invention of the present application, and FIG. 5 is a schematic plan view of a parking lot gate portion for explaining the arrangement and the like. This vehicle registration number recognition device is also for recognizing the vehicle registration number of the vehicle entering and leaving the parking lot as in the previous embodiment. The schematic configuration is the same as that of the above-mentioned embodiment, and is different only in that the above-mentioned self-lighted license plate detecting means 13 is not provided. Of course, the content of image processing and the content of control of each unit are correspondingly different.

When the configuration is simply repeated, this vehicle registration number recognition device is also connected to the near infrared region illumination device 12, the video camera 11, the vehicle head sensor including the projector 31A and the light receiver 31B, and these components are connected. Image processing unit 20B
It is equipped with. The video signal from the video camera 11 is input to the image input unit 21 of the image processing unit 20B.

The image processing unit 20B is also the same as that of the above-mentioned embodiment, and includes an image input unit 21, an image memory 22, an image processor 23 connected to the image memory 22 by a direct bus, and a CPU bus for each of the above units. Is connected via C to control each part and input / output data.
A PU 24 and an I / O circuit 25 for the CPU 24 to perform input / output with the outside are provided.

A light receiver 31B is also connected to the I / O circuit 25 to receive a vehicle head detection signal, and a shutter signal is output from the I / O circuit 25 to the video camera 11 as well as a near infrared region. The same is true in that a drive signal for driving the lighting device 12 is output and the vehicle registration number recognition result obtained by image processing is transmitted to the host device.

In the second invention of the present application, all approaching vehicles regardless of the type of license plate are illuminated by the near-infrared region illumination device and taken by the video camera, and by the video camera without illumination. Both of the picked-up images are taken in, and these two images are sequentially processed to recognize the vehicle registration number from the appropriate one. Next, the operation of the apparatus of this embodiment will be described. Note that FIG. 6 shows an example of a corresponding flowchart.

During operation of the apparatus, a light beam is always emitted from the light projector 31A toward the light receiver 31B. Light receiver 3
When light from the light projector 31A is cut off by the entering vehicle, the vehicle 1B responds to this by transmitting a signal different from that at the time of light reception (normal state). This change (rise or fall) is recognized by the image processing unit 20B as a vehicle head detection signal, and the entry of the vehicle can be recognized (FIG. 6, S1 ′).

Correspondingly, the image processing section 20B obtains both an image under illumination by the near infrared illumination device and an image without illumination. For example, the image processing unit 20B outputs a drive signal to the near-infrared region lighting device 12, and the near-infrared region lighting device 12 illuminates (emits) correspondingly (S2 '). First, the (first) image is captured based on the video signal obtained under this illumination (S3 '). Subsequently, the image processing unit 20B stops the drive signal, and correspondingly stops (turns off) the illumination of the near-infrared region lighting device 12 (S4 '). Then, the second (second) image is captured based on the video signal obtained without illumination (S5 ').

In this way, two types of images can be obtained almost simultaneously. If it is a self-illuminating license plate that is lit,
It is not possible to obtain an image of the license plate portion with good contrast in the first image, but it means that an image of the license plate portion with good contrast is obtained in the remaining second image. On the contrary, if it is a normal license plate or a self-illuminating license plate in the off state, it is possible to obtain an image of the license plate portion with good contrast in the first image under illumination in the near infrared region. At this time, the second image is an image of the license plate portion with poor contrast.

As described above, since an image of the license plate portion having a high contrast is always obtained in either image for any license plate, an appropriate image is selected (S6 '), Then, a predetermined vehicle registration number recognition process is performed (S7 '). Of course, for the time being, try the vehicle registration number recognition process for the first image, and if the desired result is obtained, it is adopted as it is and recognition is completed, and if the desired recognition is not possible, switch to the second image and switch the vehicle registration number. The recognition process may be performed.

As described above, according to the present embodiment as well, in the case of a normal-painted license plate, when the self-illuminating license plate is turned off, and when the self-illuminating license plate is turned on, there are three cases. Since an appropriate contrast can be obtained between the base of the plate and the character area, the subsequent recognition algorithm is simplified and the recognition accuracy is improved.

The above-mentioned near-infrared illuminating device may be one that continuously lights up, but may be one that emits strobe light. In this case, the video camera is controlled to perform the shutter operation within the flash emission time. For image selection, the image processing up to the extraction of the character part is performed, and if the extraction is successful, the character recognition process is advanced if it can be extracted, and if it cannot be extracted, the image is switched and the character part extraction process is performed. The character recognition process that follows may be performed.

[0040]

As described above in detail, the vehicle registration number recognition device of the first invention of the present application is a near infrared illumination device for irradiating a vehicle traveling path with near infrared illumination light and lighting of a traveling vehicle on the vehicle traveling path. A self-illuminating license plate detecting means for detecting the self-illuminating license plate, a video camera for capturing the foreground or the rear view of the traveling vehicle by imaging the traveling path of the vehicle, and vehicle registration number recognition from the output of the video camera. An image processing unit is provided, and when the image processing unit detects a self-illuminating license plate illuminated by the self-illuminating license plate detecting means, the near-infrared illumination device does not perform illumination in response to vehicle detection. The image signal of the video image captured by the video camera is processed to recognize the vehicle registration number, but if the illuminated self-illuminating license plate is not detected, the near-infrared lighting device is supported to detect the vehicle. It is configured to perform image processing of the video signal captured by the video camera by illuminating the vehicle and recognize the vehicle registration number.Therefore, a normal license plate, a self-illuminating license plate that is off and a self-illuminating system that is on. In all three cases of the license plate, it is possible to take an image with a proper contrast between the vehicle registration number and the background, and the recognition accuracy is improved with simple image processing.

Further, in the second invention of the present application, the vehicle registration number recognition device is provided with a near-infrared region lighting device for irradiating the near-infrared region illumination light to the vehicle traveling path, and the foreground or the rear of the traveling vehicle by imaging the vehicle traveling route. A video camera for obtaining a view, and an image processing unit for recognizing a vehicle registration number from the output of the video camera,
This image processing unit obtains both an image captured by the video camera with illumination by the near-infrared illumination device in response to vehicle detection and an image captured by the video camera without illumination, and outputs both images. Since the vehicle registration number is recognized by sequentially performing image processing on the vehicle, three types of the ordinary license plate, the self-illuminating license plate in the off state and the self-illuminating license plate in the lit state are provided, as in the first invention. In all cases, an image can be picked up with a proper contrast between the vehicle registration number and the background, and the recognition accuracy is improved with simple image processing.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a vehicle registration number recognition device of the first invention of the present application.

FIG. 2 is a plan view illustrating the arrangement of the apparatus of the embodiment shown in FIG.

FIG. 3 is a flowchart illustrating the operation of the apparatus of the embodiment shown in FIG.

FIG. 4 is a block diagram showing a configuration of an embodiment of a vehicle registration number recognition device of the second invention of the present application.

5 is a plan view for explaining the arrangement of the apparatus of the embodiment shown in FIG.

FIG. 6 is a flowchart illustrating the operation of the apparatus of the embodiment shown in FIG.

FIG. 7 is a plan view showing an example of a conventional vehicle registration number recognition device.

[Explanation of symbols]

 3 ... Self-illuminating license plate, 11 ... Video camera, 12 ... Near-infrared illuminating device, 13 ... Self-illuminating license plate detecting means, 20A, 20B ... Image processing unit.

Claims (2)

[Claims] 1. A near-infrared region lighting device (12) for irradiating a near-infrared region illumination light to a vehicle traveling road and self-luminous light for detecting a self-illuminating license plate (3) of a traveling vehicle on the traveling route of the vehicle. Type license plate detection means (13) and a video camera (11) for capturing the traveling path of the vehicle to obtain the foreground or rear view of the traveling vehicle.
And an image processing unit (20A) for recognizing the vehicle registration number from the output of the video camera (11), wherein the image processing unit (20A) is a self-illuminating license plate detection device. When the self-illuminating license plate (3) illuminated by the means (13) is detected, the near-infrared lighting device (1
The image signal of the video image captured by the video camera (11) is processed without illuminating by 2) to recognize the vehicle registration number, but if the illuminated self-illuminating license plate (3) is not detected, vehicle detection is supported. The vehicle registration number recognition apparatus is characterized in that the vehicle registration number recognition is performed by performing image processing on the image signal captured by the video camera (11) by illuminating the near infrared region illumination device (12). 2. A near-infrared region illumination device (12) for irradiating a near-infrared region illumination light to a vehicle traveling route, and a video camera (11) for capturing an image of the traveling route of the vehicle to obtain a foreground or a background of the traveling vehicle, A vehicle registration number recognition device having an image processing unit (20B) for recognizing a vehicle registration number from the output of the video camera (11), wherein the image processing unit (20B) corresponds to a vehicle detection Both the image captured by the video camera (11) with illumination by the external illumination device (12) and the image captured by the video camera (11) without illumination are obtained, and both images are processed in sequence. Vehicle registration number recognition device characterized by performing vehicle registration number recognition.