JP2002133579A - Vehicle license plate reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle license plate reader capable of reading not only a general license plate but also a character lighting license plate. SOLUTION: In this vehicle license plate reader, a license plate is imaged by an imaging means n-times when at least the license plate is within the imageable region of the imaging means. Among them, the imaging is performed while lighting an illumination means for m times (m<n), and performed without lighting for the remaining n-m times. When the imaging is performed while lighting the illumination means in an insufficient illuminance, the license plate information for the general license plate is read, and when the imaging is performed without lighting, the license plate information for the character lighting license plate is read.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle license plate reading apparatus capable of reading license plate information of both a normal license plate and a character-type license plate.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a system configuration of a conventionally used license plate reader. That is, an image pickup means 3 for picking up an image of a license plate, which is realized by, for example, a charge-coupled device camera (hereinafter abbreviated as a CCD camera), an illuminating means 1 which is turned on when illuminance is insufficient, and an image recognition means for recognizing license plate information. And a computer 5 for performing various processes based on the license plate information. Image recognition means 4
When the control signal C1 is sent to the image pickup means 3, the image pickup means 3 is operated, and the control signal C2 synchronized with the camera shutter timing is sent from the image pickup means 3 to the light supply means 1.
Lights up. As shown in FIG. 3, the imaging unit 3 and the illumination unit 1 are installed near a road, for example, on a mount 9 on a support 6, and mounted on a front portion of a vehicle 7 running on a road 8. The license plate is illuminated and imaged.

The illuminating means 1 is a light emitting diode (LE) that emits infrared light so as not to distract the driver of the vehicle.
D) or the like, and is lit when the illuminance is insufficient such as at night, rainy weather, or cloudy weather. The image pickup means 3 always takes pictures at time intervals (1/30 seconds) corresponding to the video rate, and sends the image data I to the image recognition means 4.
The image recognizing means 4 binarizes the image data to determine whether or not there is a license plate in the image data. If there is a license plate in the image data, the image recognition means 4 converts the image of the license plate portion of the vehicle. Cut out and recognize license plate information.

Further, the recognized license plate data D is sent to the computer 5 and stored, and compared with, for example, license plate information of a stolen vehicle that has been registered in advance, thereby finding a stolen vehicle or a criminal vehicle. Used for

[0005] This type of license plate reader is shown in FIG.
Not only on the side of the road, but also at the entrances of indoor and outdoor parking lots, waste disposal sites, etc., it is often used for managing vehicles entering and exiting.

[0006]

Normally, the illuminating means 1 is turned on when the illuminance is insufficient such as indoors, rainy weather or cloudy weather. In this case, the lighting timing A of the illumination means 1 and the shutter timing B of the imaging means 3 are synchronized as shown in FIG. 5 when the time direction is represented by t, and in the case of a normal license plate, License plate information can be recognized at such a shutter timing. In this case, the image of the license plate imaged by the imaging means is substantially as shown in FIG.

However, when the character light type license plate is turned on at night, a sufficient contrast between the character portion and the ground portion reflecting the light of the lighting device cannot be obtained due to the light emitted from the character. Therefore, the image of the license plate captured by the image capturing means 3 is substantially as shown in FIG. 7, and the license plate information cannot be recognized. Therefore, even when the license plate is turned on at night or the like, a vehicle license plate reader capable of recognizing the license plate information is required. For this purpose, the following methods have been proposed.

One is that an illuminating means is provided with an infrared transmitting filter, and a band-pass (band-pass) filter for passing only light in a wavelength region different from the light emitted from the character portion of the character-type license plate is used by the imaging means. A device which is provided in front of a CCD camera and attempts to obtain a contrast between a character portion and a ground portion of a license plate by blocking light coming from the character portion (Japanese Patent Laid-Open No. 11-339176).
The other uses an infrared laser diode for illumination means,
Install a bandpass filter that illuminates intensely for a very short time, which is sufficiently shorter than one frame taken by the CCD camera, and passes only light corresponding to the wavelength of light emitted from the laser diode in front of the CCD camera. To obtain a contrast between the ground portion of the license plate and the character portion (Japanese Patent Laid-Open No. 11-29578).
4).

In the former, an infrared transmission filter is provided for the illumination means, and a band pass filter is provided for the CCD camera of the imaging means. Although these filters transmit light of a desired wavelength, they actually attenuate the light a little, so that in order to obtain sufficient illuminance, the light source used for the illumination means must be reduced accordingly. It is necessary to increase the output, and the output is wasted. In addition, since two types of filters are used, the configuration becomes complicated accordingly.

In the latter, an infrared laser diode is used as an illuminating means in order to output a powerful infrared ray having a very narrow wavelength half width in a very short time. However, a laser diode is more expensive than an ordinary infrared LED. It is.

The present invention has been made in view of the above situation, and its object is to provide a simple structure similar to a conventionally used license plate reader, and to use not only a normal license plate but also a character light type reader. It is an object of the present invention to provide a license plate reading device which can also read license plate information of a license plate.

[0012]

In order to solve the above-mentioned problems, a license plate reader according to the present invention is provided with an image pickup means for picking up an image of a license plate of a vehicle, and a lighting device which is turned on in synchronization with a shutter signal from the image pickup means. In a license plate reading device including a lighting unit for illuminating the license plate and an image recognizing unit that reads an image captured by the imaging unit, when the license plate is at least in an imageable area of the imaging unit, the imaging is performed. The imaging is performed n times by the means, of which m times (m <n) are performed by turning on the lighting means, and the remaining nm times are performed without turning on the lighting means. .

With this configuration, the imaging is performed without turning on the illuminating unit at least once out of the n times of imaging by the imaging unit, so that the illuminating unit is turned on to perform imaging. In this case, the license plate information of the normal license plate is read, and when the image is taken without lighting the license plate information, the license plate information of the character light type license plate is read.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. In FIG. 1, components common to FIG. 4 showing the prior art are denoted by the same reference numerals. That is, the illuminating means 1 is realized by a light emitting diode or the like that emits infrared light so as not to distract the driver on the road, and is turned on indoors or at night, when the illuminance is insufficient such as rainy weather or cloudy weather.

The image pickup means 3 always takes pictures at time intervals (1/30 seconds) corresponding to the video rate, and sends the image data I to the image recognition means 4. The image recognizing means 4 binarizes the image data to determine whether there is a license plate in the image data. If there is a license plate in the image data I, the image of the license plate portion of the vehicle is displayed. And recognize the license plate information. The recognized license plate data D is sent to the computer 5.

When the control signal C1 is sent from the image recognition means 4 to the image pickup means 3, the image pickup means 3 operates, and the image pickup means 3 sends the control signal C2 synchronized with the shutter timing of the camera shutter to the signal selection means 2. And send. Further, from the signal selecting means 2 to the lighting means 1
When the control signal C3 is sent to the lighting unit 1, the lighting unit 1 is turned on. Here, the signal selecting means 2 has a function of sending every other control signal from the imaging means 3 to the lighting means 1.

If the speed of the vehicle traveling on the road is, for example, 80 km / h, the vehicle travels about 70 cm during the time corresponding to the video rate (1/30 second). Therefore, while the vehicle passes through the area in which the license plate can be imaged, the imaging by the imaging means 3 is performed about two or three times.

That is, the license plate is used as the image pickup means 3.
In the above case, when the image is within the image-capturable area, the imaging unit 3 performs one (m) of the two (n) imagings.
Turns on the illuminating means 1 to take an image, and the remaining one time (nm)
Times, m <n), the image is taken without turning on the illumination means 1,
These two imagings are repeated as one cycle. Here, the lighting timing A of the illumination means 1, the shutter timing B of the imaging means 3, and the time T required for the license plate to pass through the imageable area of the imaging means 3
FIG. 2 shows the relationship with the time direction t.

In the case of a vehicle equipped with a normal license plate when the illuminance is insufficient, the license plate information cannot be read when the image is taken without turning on the illuminating means 1.
The travel distance of the vehicle until the next imaging timing when the lighting unit 1 is turned on is, as described above, the imaging unit 3 performs shooting at the time interval (1/30 second) corresponding to the normal video rate. Therefore, for example, a vehicle traveling at a speed of 80 km / h is about 70 cm. As a result, the license plate is sufficiently within the image-capable area of the imaging unit 3 even after the elapse of this time, so that the license plate information can be read at the next lighting timing when the lighting unit 1 is lit.

In the case of the character-type license plate, the image pickup timing when the illuminating means 1 is turned off is opposite to the above case.
The license plate information can be read.

Therefore, if the lighting means 1 is turned on at the timing shown in FIG. 2, the license plate information is obtained for both a vehicle equipped with a normal license plate and a vehicle equipped with a character-type license plate. Can be read.

If the illuminance is sufficient, such as during the daytime, there is no need to turn on the lighting device, and if the illuminance is sufficient, the character-type license plate will not be turned on. The license plate information of any license plate can be read. In the case where the internal light bulb for lighting the character-type license plate is damaged, it goes without saying that the license plate information can be read in the same manner as a normal license plate.

In FIG. 1, the signal selection means 2 is a separate unit from the imaging means 3 and the illumination means 1, but the signal selection means 2 is integrated with either the imaging means 3 or the illumination means 1. Or a unit in which these three members are integrated. Further, in FIG. 2, the lighting unit is turned on once for two imagings by the imaging unit, but the traveling speed of the vehicle is slow enough or the vehicle is stopped for a while, as at the entrance of a parking lot. If it is a place where it is expected that, for example, five times of imaging by the imaging means, the lighting means may be turned on for example three times and the lighting means may not be turned on for the remaining two times, or the lighting means may be turned on. It will be apparent that the ratio of the number of times of imaging that accompanies and the number of times of imaging that does not involve lighting of the illumination means may be other than this. In this embodiment, a CCD camera is used as the image pickup means, but the image pickup means may be other than this.

In FIG. 1, a signal selection means for selecting a control signal from the imaging means is provided in order to generate the lighting timing of the illumination means and the shutter timing of the imaging means as shown in FIG. The timing device may adjust the lighting timing of the illumination means and the shutter timing of the imaging means.

The following are examples of applications of the present license plate reader.

A criminal vehicle detection system for detecting a stolen vehicle or a criminal vehicle by sending license plate information obtained by the license plate reader to a computer and collating it with license plate information of a stolen vehicle registered in advance. .

A vehicle entrance / exit management system which includes the license plate reader in a parking lot of a hotel or a department store and collects and manages license plate information of vehicles entering and exiting.

Various systems to which the present invention is applied will not be described in further detail, but it will be apparent that the application system of the present invention is not limited to the above two examples.

[0029]

According to the license plate reader of the present invention, at least when the license plate is within the image-capturable area of the image-capturing means, the image-capturing means captures images n times, and m times (m <n) are performed. It is characterized in that imaging is performed by turning on the illuminating unit, and imaging is performed without turning on the illuminating unit for the remaining nm times.

With this configuration, it is possible to read not only the information on the normal license plate but also the information on the character-type license plate, and it is extremely simpler than the above-described conventional character-type license plate reader. This can be realized with a simple configuration.

Therefore, by using the crime vehicle detection system using the present invention, it is possible to read the license plate information whether the crime vehicle is equipped with a normal license plate or a character-type license plate. Therefore, the criminal vehicle can be more reliably found, and the arrest rate of criminal is improved.

If the vehicle entry / exit management system using the present invention is installed in a hotel or a parking lot of a department store, the system can be used regardless of whether the vehicle is equipped with a normal license plate or a character-light type license plate. Since it becomes possible to read the license plate information, the reading of the license plate information is assured accordingly, and the effect of improving the accuracy of the warehouse management is achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of a license plate reading device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a temporal relationship between a shutter timing of an imaging unit and a lighting timing of an illumination unit of the license plate reading device according to the embodiment of the present invention.

FIG. 3 is a diagram showing the installation state of a conventional license plate reader on a road.

FIG. 4 is a diagram showing a system configuration of a conventional license plate reader.

FIG. 5 is a diagram illustrating a relationship between a shutter timing of an imaging unit and a lighting timing of an illumination unit in a conventional license plate reading device.

FIG. 6 is a diagram showing a state in which a lighting device is turned on in a conventional license plate reading apparatus and an image of a normal license plate is taken.

FIG. 7 is a diagram showing a state in which the illuminating means is turned on in the conventional license plate reading apparatus and an image is taken when the character-type license plate is turned on.

[Explanation of symbols]

 1. Lighting means 2. Signal selection means 3. Imaging means 4. Image recognition means 5. Computer 6. Prop 7. Vehicle 8. Road 9. Mounting base A. Lighting timing of lighting means B. Shutter timing of imaging means C1. Control signal C2. Control signal C3. Control signal I. Image data D. License plate data

Claims (1)

[Claims] An image pickup means for picking up an image of a license plate of a vehicle, an illuminating means for illuminating the license plate which can be turned on in synchronization with a shutter signal from the image pickup means, and an image recognizing means for reading an image picked up by the image pickup means. A license plate reading device comprising: when at least a license plate is within an image-capturable area of the image-capturing means, perform image-capturing by the image-capturing means n times, and light the light-emitting means m times (m <n). A license plate reader, wherein the image is taken without turning on the illumination means for the remaining nm times.