JPH07296289A - License plate automatic reader - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a license plate automatic reading device that reduces the power consumption of the lighting device, prolongs the life of the lighting device, and does not require equipment dedicated to vehicle detection. [Structure] A television camera 10, a strobe device 14, a delay circuit 13, an image processing section 11, and a control section 12 for controlling the image processing section 11, and the delay circuit 13 is a vertical synchronization signal for the television camera 10. The light emission timing of the strobe device 14 is made in the next imaging period with reference to. [Effect] The power consumption of the lighting device is small and the life can be extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for automatically reading license plates of an automobile which is running or stopped.

[0002]

2. Description of the Related Art A conventional automatic license plate reader uses a lighting device that emits light constantly. Alternatively, a vehicle detection device such as an ultrasonic sensor is provided, and the strobe device is caused to emit light at the vehicle detection timing of the vehicle detection device to capture an image. FIG. 5 is a view of a conventional license plate automatic reading device, which is provided with a vehicle detection device 55 using ultrasonic waves on a pillar 56 beside a road, and when a vehicle passing on the road is detected, a pulse is emitted as a vehicle detection signal. The transmitted vehicle detection pulse is transmitted to the control device 5 by the signal transmission device 57.
It is transmitted to 3. The roadside support 54 is the strobe device 51.
The television camera 52 and the control device 53 are provided, and the flash device 51 emits light and the television camera 52 shoots at the timing of the vehicle detection pulse transmitted to the control device 53. FIG. 4 is a diagram of a conventional strobe light emission timing, in which a pulse is generated in the vehicle detection signal. When the image pickup timing signal of the television camera 52 is low level, it is a period during which an image is captured by the image pickup element, and when it is high level, it is a period when the image of the image pickup element is output as a television camera output signal. Therefore, it is necessary to cause the strobe device 51 to emit light when the image pickup timing signal is at a low level. The video signal for each scanning line is carried on the output signal of the television camera in synchronization with the vertical synchronizing signal and the horizontal synchronizing signal. The vertical sync signal generates a pulse at the start timing of the first scan line in one screen, and the horizontal sync signal generates a pulse at the start timing of each scan line. The television camera 52 needs to have a mechanism for resynchronizing with the vehicle detection signal.

As a conventional technique of this type, Japanese Patent Laid-Open No. 5-32509
The technology described in Japanese Patent Publication No. 1 is known, in which an image recognition device is used as a vehicle detection device, and a strobe light is emitted when a car arrives.

[0004]

However, the above-mentioned conventional license plate automatic reading device has a problem that the one having a constant light emitting illuminating device consumes a large amount of power and has a short life of the light emitting device. The device having the device has a problem that a dedicated vehicle detection device is required. The present invention has been made in view of the above circumstances, and an object thereof is to provide an automatic license plate reader including an illumination device that does not continuously emit light and does not require a dedicated vehicle detection device.

[0005]

The automatic license plate reading apparatus of the present invention includes a television camera, a delay circuit for delaying the vertical synchronizing signal of the television camera for a predetermined time, and an illuminating device at the timing of the signal delayed by the delay circuit. And an image processing unit that processes an image captured by the television camera and recognizes the presence or absence of a vehicle and the characters on the license plate.

As another means, the automatic license plate reading apparatus of the present invention is a television camera, a delay circuit for delaying a horizontal synchronizing signal of the television camera for a predetermined time, and an illuminating device at the timing of the signal delayed by the delay circuit. And an image processing unit that processes an image captured by the television camera and recognizes the presence or absence of a vehicle and the characters on the license plate.

[0007]

Since the strobe device emits light in the next image capturing period by waiting for a certain period of time based on the vertical sync signal or the horizontal sync signal of the television camera, a dedicated vehicle detection device is not required, and a constant light emission lighting device is provided. Compared to the automatic license plate reader, the power consumption is small and the life of the lighting device is extended.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the automatic license plate reading apparatus of the present invention will be described below with reference to FIG. The license plate automatic reading device in FIG. 1 includes a television camera 10, a strobe device 14, and a control device 15. The control device 15 includes an image processing unit 11 for detecting a vehicle and reading a license plate from an image that is output from a TV camera output signal from the TV camera 10, a control unit 12 for controlling the image processing unit 11, and a TV camera. 1
The delay circuit 13 delays the vertical synchronizing signal or the horizontal synchronizing signal output by 0 to generate the light emission timing of the strobe device 14. The image processing unit 11 and the control unit 12 can use the "image processing device" of JP-A-60-241387 and the "vehicle number recognition device" of Japanese Patent Application No. 5-6445. Delay circuit 13
Can be achieved with a TTL counter or the like because it is a delay of several tens of milliseconds.

FIG. 2 is a diagram showing strobe light emission timing of the automatic license plate reading apparatus of the present invention. Figure 2
In (a), the image pickup timing signal is the TV camera 1.
The period when the image is captured by the image sensor of 0 is low level, and when the image is high, the image of the image sensor is output as a television camera output signal. Therefore, it is necessary to cause the strobe device 14 to emit light when the imaging timing signal is at a low level. The video signal for each scanning line is carried on the output signal of the television camera in synchronization with the vertical synchronizing signal and the horizontal synchronizing signal. The vertical sync signal generates a pulse at the start timing of the first scan line in one screen, and the horizontal sync signal generates a pulse at the start timing of each scan line. The delay circuit 13 counts the pulses of the horizontal synchronizing signal, and produces the strobe light emission timing at the time when the pulses for one screen are counted.

FIG. 2B is a timing chart in the case of producing strobe light emission timing by using the vertical synchronizing signal. Each signal is the same as that in FIG. 2A, but the time scale of display is large, and in FIG. 2B, the imaging timing signal is low level four times, that is, four screens are captured.

In the automatic license plate reading apparatus of the present invention, an image is captured by emitting a strobe light regardless of whether or not there is a vehicle. The vehicle number recognition processing is performed only when the vehicle is detected by the image processing unit 11. The delay circuit 13 delays the vertical synchronizing signal for a certain period of time and creates a strobe light emission timing so that the strobe device 14 emits light at the next image capturing timing.

FIG. 3 is a view showing the license plate automatic reading apparatus of the present invention installed on a road. A strut 31 provided with a TV camera 10, a strobe device 14, and a control device 15 is set up beside the road, and a region 32 which is the field of view of the TV camera 10 is set to the strobe device 1 every time the TV camera 10 captures an image.
Illuminate at 4. As described above, the automatic license plate reading device of the present invention has an effect that the vehicle detection device is not required, as compared with the conventional strobe device. Further, the license plate automatic reading device of the present invention has the effects that the lighting device consumes less power and the lighting device has a longer life as compared with the conventional device provided with the lighting device of constant light emission. If a light emitting diode is used for the strobe device 14 of the automatic license plate reading apparatus of the present invention, an automatic license plate reading apparatus which consumes less power and has a long life can be obtained.

[0013]

The license plate automatic reading device of the present invention has the effect that the vehicle detection device is not required, as compared with the device having the conventional strobe device. Further, the license plate automatic reading device of the present invention has the effects that the lighting device consumes less power and the lighting device has a longer life as compared with the conventional device provided with the lighting device of constant light emission.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a license plate automatic reading device of the present invention.

FIG. 2 is a diagram showing a strobe light emission timing of the automatic license plate reading apparatus of the present invention.

FIG. 3 is a diagram in which a license plate automatic reading device of the present invention is installed on a road.

FIG. 4 is a diagram showing strobe emission timing of a license plate automatic reading device equipped with a conventional strobe device.

FIG. 5 is a view of a license plate automatic reading device equipped with a conventional strobe device.

[Explanation of symbols]

10 ... Television camera, 11 ... Image processing part, 12 ... Control part, 13 ... Delay circuit, 14 ... Strobe device, 15 ... Control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Sato 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Plant, Inc. (72) Inventor Kazuka Asada 5-chome, Omika-cho, Hitachi City, Ibaraki Prefecture 2-1 Hitachi Ltd. Omika factory

Claims (4)

[Claims] 1. A number plate automatic reading device comprising a strobe device, a television camera, and an image processing unit for recognizing the presence of a vehicle from the image of the television camera and recognizing the characters on the number plate. An automatic license plate reading device, characterized in that the strobe device emits light at a timing delayed by a certain time from a synchronization signal. 2. The automatic license plate reader according to claim 1, wherein a light emitting diode is used in the strobe device. 3. A license plate automatic reading device comprising a strobe device, a television camera, and an image processing unit for recognizing the presence of a vehicle from the image of the television camera and recognizing the characters on the license plate. An automatic license plate reading device, characterized in that the strobe device emits light at a timing delayed by a certain time from a synchronization signal. 4. The automatic license plate reader according to claim 3, wherein a light emitting diode is used in the strobe device.