JPH02193266A - Number plate reader - Google Patents

Abstract

PURPOSE:To improve cost performance by executing a simultaneous image fetching from plural lanes and a sequential recognition of a fetching image. CONSTITUTION:In the case of executing read of number plates to three lanes by one set of image processor, the simultaneous fetching of original images from three cameras 18-20 is executed against simultaneous vehicle passing of three lanes. Subsequently, an image processing is executed by an image arithmetic part 3 successively in order of an original image input, a size discrimination of the number plate, and the read recognition of a car kind number and consecutive numbers are executed, and its result is outputted successively to car kind discrimination control parts 24-26 corresponding to each lane. In such a manner, an image processor whose cost performance is excellent can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a license plate reading device that is applied to toll road vehicle type identification devices, parking lot systems, entrance/exit management systems, and the like.

[Conventional technology]

FIG. 4 is a diagram showing the configuration of a vehicle type discrimination device using a conventional license plate reading device. 10 in Figure 4
1 is a vehicle approach road; 102 is a pair of optical sensors that detect vehicle entry; 103 is a camera that captures an image of the front of the vehicle;
4 is an image processing device that reads and recognizes license plates based on image signals from the camera 103; 105 is a step board for measuring the number of axles, wheel pressure, number of wheels, etc. of passing vehicles; 106;
107 is a vehicle height detection sensor for detecting the vehicle height, and 107 is a vehicle type discrimination control unit that discriminates the vehicle type based on signals from the footboard 105, the optical sensor 102, the vehicle height detection sensor 106, and the image processing bag device 104.

FIG. 5 is a diagram showing the configuration of a conventional image processing device. In FIG. 5, 108 is a control section consisting of a microprocessor, memory, etc., which controls the overall operation. 10
Reference numeral 9 denotes an arithmetic circuit dedicated to image processing, which performs arithmetic operations on the image in the image memory 110 according to instructions from the control section 108. Reference numeral 111 denotes a camera I/F circuit, which includes an imaging command signal 1/F circuit for the camera 103, an image signal A/D conversion circuit, and the like. 112 is an I/F circuit for outputting the license plate reading result to the vehicle type discrimination control unit 107; 113;
1 is a vehicle detection signal I/F circuit from a vehicle entry detection sensor such as a light sensor, and 114 is a bus signal line connecting the control unit 108 and each circuit.

The operation will be explained with reference to FIGS. 4 and 5. When a vehicle enters the approach road 101, the optical sensor]02 is blocked from light, and a vehicle detection signal is output to the image processing device]04. When the image processing device 1, 04 receives the vehicle detection signal, the control unit]0
8 outputs an imaging command signal to the camera 103 through the camera I/F circuit 111. When the camera 103 receives the imaging command, it performs a shutter operation, captures an image of the front of the vehicle at that time, and outputs the image signal to the image processing device 104. The image processing device 104 A/D converts the image signal using the camera 1/F circuit 111 and imports it into the image memory 110 .
performs image calculation processing, determines the size of the license plate, reads and recognizes the vehicle type number and serial number, and transmits the results to the vehicle type discrimination control section 107 via the I/F circuit 112. The vehicle type discrimination control unit 107 measures the vehicle height, the number of axles, the wheelbase, the number of wheels, etc. based on the signal from the footboard 105 obtained when the vehicle passes, the signal from the vehicle height detection sensor 106, etc. Combined with the received license plate reading result, the vehicle type is comprehensively determined, and the result is output to an automatic pass ticket issuing machine, an automatic toll collection machine, etc.

[Problem to be solved by the invention]

On normal toll roads, each interchange or toll booth has multiple lanes, so multiple vehicle type identification devices are required. However, image processing devices usually have high-speed image memory,
Since a high-speed image processing circuit and the like are used, it is expensive to install one image processing device having the configuration shown in FIG. 5 for each lane, and the cost performance is poor.

An object of the present invention is to provide a license plate reading device that can solve the above-mentioned conventional problems.

[Means to solve the problem]

The license plate reading device according to the present invention includes a plurality of vehicle entry detection sensors, a plurality of camera devices that take images of the front part of each vehicle in response to each vehicle entry detection by these detection sensors, and a plurality of camera devices that take images of the front part of each vehicle in response to each vehicle entry detection by the plurality of vehicle entry detection sensors. A sensor I/F circuit, a plurality of camera I/Fs corresponding to the plurality of camera devices.
It is characterized by comprising a circuit, a plurality of original image memories, a plurality of image memories for calculation corresponding to these original image memories, and one image processing device having one image processing calculation section. That is, in the present invention, one control unit, an image calculation unit, a calculation image memory, a plurality of camera I/F circuits corresponding to cameras in each lane, an original image memory, and a vehicle entry detection sensor in each lane. The image processing device includes a plurality of same sensor I/F circuits corresponding to the vehicle type identification control section and a plurality of discrimination result output 1/F circuits corresponding to the vehicle type discrimination control section of each lane.

[For production]

According to the present invention, the image processing bag holder having the above configuration enables the following operations. In other words, when vehicles pass simultaneously in multiple lanes, it is possible to capture original images from multiple cameras at the same time, and the image processing unit sequentially processes the images in the order in which the original images are captured to determine the size of the license plate, It becomes possible to read and recognize the vehicle type number and serial number and output the results sequentially to the vehicle type discrimination control section corresponding to each line, thereby providing an image processing device with good cost performance.

〔Example〕

FIG. 1 is a diagram showing the configuration of an image processing device according to an embodiment of the present invention, and this embodiment is an example in which one image processing device reads license plates for three lanes. This is also an example in which one set of image memory for calculation is provided.

In FIG. 1, reference numeral 1 denotes a control section which is composed of a microprocessor, its peripheral circuits, programs, data memory, etc. and performs overall control; 2 is an image calculation section 3; an image for calculation that can be read and written by the control section 1; Memory, 3 is an image calculation unit that performs dedicated high-speed calculations for image processing, and 4 to 6 are I/Fs for optical sensors installed in each lane to detect vehicle entry.
Circuits 7 to 9 are camera I/Is that have the function of outputting an imaging command to the cameras installed in each lane, A/D converting the vehicle front image signal output from the camera, and storing it in the original image memory. F circuit, 10 to 12 are original image memories that store images of the front of the vehicle taken by each camera, and 13 to 15 are vehicle type discrimination control units for each lane that read the license plate from the front image of the vehicle in each lane. I/
F circuit, 16 is a bus signal line for transferring and controlling data with each circuit, 17 is a high-speed data bus for transferring data from the original image memory corresponding to each lane to the image memory for calculation, 18 to 20 21 to 2B are camera devices installed in each lane, optical sensors 21 to 2B are installed in each lane to detect vehicle entry, and 24 to 26 are vehicle type discrimination control units installed in each lane.

FIG. 2 is a diagram showing an example of a timing chart of processing of the image processing apparatus having the configuration shown in FIG.

In FIG. 2, the horizontal axis represents the passage of time.

21 to 23 represent the states of each of the optical sensors a to C, and the on state represents that the optical sensor is blocked from light. 7～
9 represents the timing from when each of the camera I/F circuits a to C receives an imaging command from the control unit until the time when each of the corresponding cameras completes capturing the original image, as a solid line. 27, 28
．． 31 represents the processing of the program executed by the microprocessor of the control unit, and the execution timing of each process is represented by a solid line. The control unit 1 normally performs constant recognition processing 3.
0, and this process is executed in an interrupt-enabled state, so that the interrupt process at 27.28 can be interrupted and processed preferentially while the process is being executed. In the recognition process 30, one solid line represents the loop state when the recognition process is requested, and two solid lines represent the actual execution of the recognition process.

Further, the symbols a, b, and c attached to the solid line of each process indicate that image processing is performed for the optical sensor or camera corresponding to each symbol.

29 in FIG. 2 is a first-in, first-out queue table that indicates that there is a recognition processing request generated in the memory of the control unit, and symbols such as ■, ■ are the original images from the optical sensor and camera corresponding to each symbol. Represents the registration (enqueue) or retrieval (dequeue) of a recognition processing request for.

FIG. 3 is a flowchart of the recognition process executed by the microprocessor of the control unit 1.

After the microprocessor of the control unit 1 completes the initialization process required when the power is turned on, it starts executing the recognition process shown in FIG. 3. The recognition process first checks the contents of the recognition process request queue table, and if there is no requested data, waits in a loop until the requested data arrives. When a request arrives, the oldest request data is taken out from the queue table, and the contents (original image) of any of the original image memories a to C corresponding to the contents of the request data (request lanes a to c) are first calculated. After transferring the license plate to the image memory 2, the image calculation unit is controlled to extract the license plate from the original image, and read and recognize whether it is a large plate or medium plate, vehicle model number, and serial number.

Next, after outputting the read result to one of the vehicle type discrimination control units a to c corresponding to the requested lanes a to c through the I/F circuit, the process returns to checking the next recognition processing request.

The operation will be explained with reference to FIGS. 1, 2, and 3. After the microprocessor of the control unit 1 completes the initialization process necessary when the power is turned on, it starts executing the recognition process (FIG. 3). In the initial state, there is no request data in the recognition processing request queue table, so the recognition processing is in a loop state at the time of a request.

When the vehicle now enters lane al:, each sensor a21 is turned on, and the optical sensor I/F circuit a4 outputs an interrupt signal to the control unit 1. The control unit 1 activates the first interrupt processing 27 by an interrupt operation.

The tip interrupt processing 27 outputs an imaging command to the camera I/F circuit a7 corresponding to the lane where the interruption occurred. The camera I/F circuit a7 outputs an imaging command signal to the camera a8, and also A/D converts the image signal output from the camera a7 and stores it in the corresponding original image memory 10. The camera 1/F circuits 7 to 9 can be configured so that they can capture image signals into the original image memory without the help of the control unit 1 by simply receiving an imaging command from the control unit 1. The unit 1 sends the imaging command to the camera I/F circuits 7 to 9.
After outputting to , you can continue executing the process that was previously executed.

Note that the time required for one interrupt processing 27 is at most several hundred μSee, which is sufficiently smaller than the time required for the camera I/F circuits 7 to 9 to capture an image (several tens of m5ec).

When a vehicle enters lane b while the camera I/F circuit a4 is capturing images, the optical sensor b22
The controller 1 executes the interrupt process 27, and outputs an imaging command to the camera I/F circuit b5, so that the camera 1/F circuit b5 starts capturing an image. In this way, it is possible to simultaneously capture images of up to three lanes.

Next, when the camera I/F circuit a4 finishes capturing the image from the camera into the original image memory alo, the camera I/F circuit a4
outputs an interrupt signal indicating completion of image capture to the control unit 1. When the control unit 1 receives an interrupt signal indicating the completion of image capture, the control unit 1 executes an image capture completion interrupt process 28 by an interrupt operation. In the image capture completion interrupt process 28, by checking any of the camera 1/F circuits a to C that caused the interrupt,
Register one of the identification symbols a to c (a in this case) as request data in the recognition processing request queue table 29 (
After enqueuing), the process is terminated and the process returns to the previously executed process, that is, the recognition process 30. Recognition processing 3
Since request data a has been registered in the recognition process request queue, 0 is taken out of the request waiting state and starts the license plate reading process from the original image stored in the original image memory alO according to the flowchart shown in FIG. .

Thereafter, when the camera I/F circuit b5 finishes capturing the image from the camera into the original image memory bll, the image capture completion interrupt process 28 is similarly executed and the recognition process request is registered in the recognition process request queue table 29. Ru. On the other hand, recognition processing 30
transmits the license plate reading result of the image taken from camera a to the corresponding vehicle type discrimination control unit a24 through the I/F circuit al.
After outputting through B, recognition processing request queue table 2
Return to check 9. Since the request data b has already been registered in the recognition process request queue table 29, the recognition process 3
0 continues to execute the recognition process on the original image stored in the original image memory b11 without going into a waiting state.

The time required for recognition processing for one image is several hundred meters.
sec, which is sufficiently long compared to the time required for each interrupt process.

In addition, the average passing interval of vehicles in each lane A - C, and the service time limit for automatic ticket issuance, toll collection, etc., is about 6 seconds or more, so when dealing with 3 lanes, the average passing interval is about 1 every 2 seconds. It is only necessary to be able to recognize the machine, and sufficient processing power can be achieved. As described above, it is possible to simultaneously capture images from a plurality of lanes and to sequentially read captured images.

Further, in the configuration shown in FIG. 1, it is also possible to share the image memory for calculation with the original image memories a to c. In that case, the image memory for calculation is placed in the same device as the original image memory,
It is also possible to use a plurality of formulas, and the image calculation section 3 can directly perform calculations on the calculation image memories of the people.

〔Effect of the invention〕

According to the present invention, the present invention includes a control unit, an image processing calculation unit, a plurality of camera I/F circuits, an original image memory, and a vehicle entry detection sensor I/F circuit, and is capable of simultaneously capturing images from multiple lanes, and By sequentially recognizing captured images, it is possible to provide an inexpensive license plate reading device that is compatible with multiple lanes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a license plate reading device as an embodiment of the present invention, FIG. 2 is a diagram showing a timing chart of processing in an embodiment of the present invention, and FIG. 3 is a diagram showing a timing chart of a process in an embodiment of the present invention. FIG. 4 is a diagram showing a conventional vehicle type discriminating device 4, and FIG. 5 is a diagram showing an image processing device in FIG. 4. 1... Control unit, 2... Image memory for calculation, 3...
Image calculation unit, 4-6... Optical sensor I/F circuit, 7-9
...Camera I/F circuit, 10-12...Original image memory, 13-15...I/F circuit, 18-20...Camera device, 24-26...Vehicle type discrimination control unit.

Claims (1)

[Claims] a plurality of vehicle entry detection sensors; a plurality of camera devices that take images of the front portion of each vehicle in response to each vehicle entry detection by these detection sensors; an I/F circuit for the plurality of vehicle entry detection sensors; One image processing unit including a plurality of camera I/F circuits and multiple original image memories corresponding to a plurality of camera devices, a plurality of image memories for calculation corresponding to these original image memories, and one image processing calculation unit. A license plate reading device comprising: