Title:
Vehicle monitoring method, specific character pattern recognition device, and vehicle monitoring system
Kind Code:
A1


Abstract:
In a vehicle monitoring method, recognition processing of a specific character pattern of a vehicle is performed by extracting a specific character pattern area from a taken image data. When the specific character pattern cannot be recognized, a compression range is judged as being a vehicle area clipped from the taken image data, and image data of the clipped area is compressed at a low compression ratio. When the specific character pattern is partially recognized, the compression range is judged as being the specific character pattern area clipped from the taken image data, and image data of the clipped area is compressed at the low compression ratio. When the specific character pattern is fully recognized, the compression range is judged as being the specific character pattern area clipped from the taken image data, and image data of the clipped area is compressed at a high compression ratio.



Inventors:
Kanno, Hajime (Kawasaki, JP)
Application Number:
11/113263
Publication Date:
07/20/2006
Filing Date:
04/25/2005
Assignee:
FUJITSU LIMITED (Kawasaki, JP)
Primary Class:
International Classes:
F01L1/34
View Patent Images:
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Primary Examiner:
JOHNS, ANDREW W
Attorney, Agent or Firm:
STAAS & HALSEY LLP (WASHINGTON, DC, US)
Claims:
What is claimed is:

1. A vehicle monitoring method comprising the steps of: performing recognition processing of a specific character pattern of a vehicle by extracting a specific character pattern area from a taken image data in order to monitor the vehicle based on a recognized character pattern; determining, when a result of the recognition processing indicates that the specific character pattern cannot be recognized, a compression range as being a vehicle area clipped from the taken image data, wherein image data of the clipped area is compressed at a predetermined low compression ratio to store or transmit the compressed image data; determining, when the result indicates that the specific character pattern is partially recognized, the compression range as being the specific character pattern area clipped from the taken image data, wherein image data of the clipped area is compressed at the low compression ratio to store or transmit the compressed image data; and determining, when the result indicates that the specific character pattern is fully recognized, the compression range as being the specific character pattern area from the taken image data, wherein image data of the clipped area is compressed at a predetermined high compression ratio to store or transmit the compressed image data.

2. A specific character pattern recognition device comprising: a recognition processing unit having a frame memory, a character recognition processing unit and an image processing unit, the frame memory temporarily storing an image data of a vehicle taken by an image-taking unit, the character recognition processing unit performing recognition processing of a specific character pattern of the vehicle, and the image processing unit clipping a vehicle area containing the whole vehicle from the taken image data and clipping a specific character pattern area from the vehicle area; a compression range/ratio judging unit judging a compression range and a compression ratio based on a result of the recognition processing wherein, when the result of the recognition processing indicates that the specific character pattern cannot be recognized, the compression range and the compression ratio are judged as being the vehicle area and a predetermined low compression ratio, when the result indicates that the specific character pattern is partially recognized, the compression range and the compression ratio are judged as being the specific character pattern area and the low compression ratio, and when the result indicates that the specific character pattern is fully recognized, the compression range and the compression ratio are judged as being the specific character pattern area and a predetermined high compression ratio; an image compression unit which is responsive to a judgment result of the compression range/ratio judging unit, the image compression unit clipping a corresponding area of image data for the compression range from the taken image data of the frame memory, and performing compression processing of the image data of the clipped area at the compression ratio; and a transmitting/receiving unit transmitting the compressed image data from the image compression unit.

3. The specific character pattern recognition device according to claim 2 further comprising a data storing unit storing the compressed image data provided by the image compression unit, together with the result of the recognition processing of the specific character pattern of the vehicle.

4. The specific character pattern recognition device according to claim 3 further comprising a matching processing unit performing matching processing between an externally requested vehicle specific character pattern and the result of the recognition processing stored in the data storing unit, and, when a match occurs as a result of the matching processing, the compressed image data is read from the data storing unit and transmitted.

5. A vehicle monitoring system including a plurality of specific character pattern recognition devices and a center which are connected through a communication line, each specific character pattern recognition device comprising: a recognition processing unit performing recognition processing of a specific character pattern of a vehicle based on a taken image data, and the recognition processing unit clipping a vehicle area containing the whole vehicle from the taken image data, and clipping a specific character pattern area from the vehicle area; a compression range/ratio judging unit judging a compression range and a compression ratio based on a result of the recognition processing wherein, when the result of the recognition processing indicates that the specific character pattern cannot be recognized, the compression range and the compression ratio are judged as being the vehicle area and a predetermined low compression ratio, when the result indicates that the specific character pattern is partially recognized, the compression range and the compression ratio are judged as being the specific character pattern area and the low compression ratio, and when the result indicates that the specific character pattern is fully recognized, the compression range and the compression ratio are judged as being the specific character pattern area and a predetermined high compression ratio; an image compression unit which is responsive to a judgment result of the compression range/ratio judging unit, the image compression unit clipping a corresponding area of image data for the compression range from the taken image data, and performing compression processing of the image data of the clipped area at the compression ratio; and a transmitting/receiving unit transmitting the compressed image data from the image compression unit, and the center comprising: a data management table in which the compressed image data received from each specific character pattern recognition device through the communication line are stored; and a display unit displaying the compressed image data.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2005-012376, filed on Jan. 20, 2005, the entire contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the vehicle monitoring method, the specific character pattern recognition device, and the vehicle monitoring system in which the specific character pattern of a vehicle is recognized and monitored.

2. Description of the Related Art

Specific character patterns are given to various kinds of vehicles respectively such that the patterns may not overlap. Therefore, performing automatic reading of the specific character pattern to recognize the specific character pattern of the vehicle is possible.

There have been proposed various kinds of systems that are applicable to the automation of charge payment of the tollgates on the toll roads, the judgment of whether the parking vehicles of the parking lot are the contractors' own, and the detection of burglar vehicles or the like. In such systems, the image signal indicating the image of the vehicle specific character pattern has to be processed. It is demanded for such systems to carry out the image processing of the image signal efficiently.

FIG. 7 shows the composition of the conventional vehicle monitoring device.

In the vehicle monitoring device of FIG. 7, the vehicle detecting unit 70 detects that the passing vehicle arrives at the image-taking position, and outputs the detection signal to the recognition processing unit 72. The recognition processing unit 72 outputs the image-taking instruction to the image-taking unit 71 to take the image of the passing vehicle. The image-taking unit 71 takes the image of the vehicle according to the image-taking instruction, and transmits the resulting image signal to both the recognition processing unit 72 and the image transmission unit 74.

The recognition processing unit 72 extracts the specific character pattern area from the taken image of the vehicle, and recognizes the vehicle specific character pattern based on the characters or numbers included in the specific character pattern area. As for the recognition processing of the vehicle specific character pattern, there are known various kinds of means, such as means for clipping of one character, means for pattern matching of the clipped character, and means for matching through the feature extraction.

The vehicle monitoring device of FIG. 7 is configured so that, only when the passing vehicle passes through the image-taking position, the image-taking unit 71 takes the image of the passing vehicle.

Moreover, the vehicle specific character patterns are registered beforehand in the matching unit 73. The vehicle specific character pattern which is recognized by the recognition processing unit 72 is transmitted to the matching unit 73, and the matching unit 73 performs matching of the received vehicle specific character pattern with the recorded vehicle specific character patterns. And the matching unit 73 transmits the result of the matching to the recognition processing unit 72.

If the signal indicating the matching coincidence is received from the matching unit 73, the recognition processing unit 72 transmits the matched vehicle specific character pattern to the image transmission unit 74. The image transmission unit 74 transmits the vehicle specific character pattern and the taken image signal to the image recording/displaying unit 75. The image recording/displaying unit 75 adds the date information and the image-taking position information to the received pattern/image information and records the resulting information. In the image recording/displaying unit 75, the recorded information is searched and read out based on the information related to the vehicle specific character pattern, the date, the image-taking position, etc., when the necessity occurs. The read-out information is displayed on the monitor of the image recording/displaying unit 75, which enables the checking of the vehicle of concern by viewing the monitor. See Japanese Laid-Open Patent Application No. 09-282590.

Moreover, there is known another vehicle monitoring method (see Japanese Laid-Open Patent Application No. 09-261620). In this method, the vehicle specific character pattern on the specific character pattern is recognized based on the taken image signal, compression processing of the taken image signal is performed, and the recognized vehicle specific character pattern is added to the compressed image signal so that the resulting image information is recorded. The compressed image signal of the recorded information is read out based on the vehicle specific character pattern, and expansion processing (decompression processing) of the read compressed image signal is performed so that the expanded image is displayed on the monitor.

Moreover, there is known another vehicle monitoring device (see Japanese Laid-Open Patent Application No. 09-037232). In this device, a remote monitoring unit is provided in which one monitoring range is selected from among a plurality of monitoring ranges, the compression ratio of the image signal and the transmission time are changed corresponding to the selected monitoring range, and the transmission of the compressed image signal is performed.

For example, when the monitored object is moving at high speed in the selected monitoring range, the compression ratio is made high and the transmission of the image signal is performed at high speed in order to allow the monitoring screen to follow the change of the monitored object during the high-speed movement. When the monitored object is moving at low speed in the selected monitoring range, the compression ratio is made low and the transmission of the image signal is performed at low speed in order to make the resolution of the monitoring screen high, increasing the quality of the image being displayed.

As mentioned above, the image of the vehicle specific character pattern is taken, the specific character pattern is extracted from the taken image signal through the image processing, and the character recognition processing is performed, so that vehicle monitoring can be carried out based on the recognized character pattern.

However, the image-taking conditions are greatly different depending on the angle of attachment of the specific character pattern, the state of the dirt in the specific character pattern, and the weather condition. Therefore, in the case of a poor weather condition, it is difficult to recognize the specific character pattern through the image processing.

In the case where the recognition processing of the specific character pattern of the vehicle is difficult to perform, an improved recognition processing unit can be adopted to recognize the vehicle specific character pattern. In the improved recognition processing unit, the taken image signal is inputted to the display unit and the image of the vehicle is displayed on the display monitor. The area of the specific character pattern in the image of the vehicle can be identified by viewing the image on the display monitor.

However, when the display monitor is installed at a position that is distant from the installation position of the image transmission unit 74 as shown in FIG. 7, it is necessary to transmit the image data from the image transmission unit 74 to the monitor through the telephone line. Even if the compression processing of the image data is carried out, there is much amount of image data contained in one screen of the image, and the use of high-speed transmission path is required. Therefore, it has been difficult to carry out the vehicle monitoring remotely by connecting the center and the distributed image processing units through the existing communication network of low bit rate.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved vehicle monitoring method in which the above-mentioned problems are eliminated.

Another object of the present invention is to provide a vehicle monitoring method in which the compression range and compression ratio for the compression processing of the taken image signal are controlled in response to the result of recognition processing of the specific character pattern of the vehicle in order to reduce the amount of the transmission data.

In order to achieve the above-mentioned objects, the present invention provides a vehicle monitoring method comprising the steps of: performing recognition processing of a specific character pattern of a vehicle by extracting a specific character pattern area from a taken image data in order to monitor the vehicle based on a recognized character pattern; setting, when a result of the recognition processing indicates that the specific character pattern cannot be recognized, a compression range to a vehicle area containing the whole vehicle, clipped from the taken image data, wherein image data of the clipped area is compressed at a predetermined low compression ratio to store or transmit the compressed image data; setting, when the result indicates that the specific character pattern is partially recognized, the compression range to the specific character pattern area clipped from the taken image data, wherein image data of the clipped area is compressed at the low compression ratio to store or transmit the compressed image data; and setting, when the result indicates that the specific character pattern is fully recognized, the compression range to the specific character pattern area clipped from the taken image data, wherein image data of the clipped area is compressed at a predetermined high compression ratio to store or transmit the compressed image data.

According to the present invention, when the vehicle specific character pattern is fully recognized, the compressed image data in which the image of the vehicle specific character pattern having the comparatively small area is compressed at the high compression ratio can be transmitted. It is possible to easily transmit the compressed image data through the communication network of low bit rate.

Moreover, in order to achieve the above-mentioned objects, the present invention provides a specific character pattern recognition device comprising: a recognition processing unit having a frame memory, a character recognition processing unit and an image processing unit, the frame memory temporarily storing an image data of a vehicle taken by an image-taking unit, the character recognition processing unit performing recognition processing of a specific character pattern of the vehicle, and the image processing unit clipping a vehicle area containing the whole vehicle from the taken image data and clipping a specific character pattern area from the vehicle area; a compression range/ratio judging unit judging a compression range and a compression ratio based on a result of the recognition processing wherein, when the result of the recognition processing indicates that the specific character pattern cannot be recognized, the compression range and the compression ratio are judged as being the vehicle area and a predetermined low compression ratio, when the result indicates that the specific character pattern is partially recognized, the compression range and the compression ratio are judged as being the specific character pattern area and the low compression ratio, and when the result indicates that the specific character pattern is fully recognized, the compression range and the compression ratio are judged as being the specific character pattern area and a predetermined high compression ratio; an image compression unit which is responsive to a judgment result of the compression range/ratio judging unit, the image compression unit clipping a corresponding area of image data for the compression range from the taken image data of the frame memory, and performing compression processing of the image data of the clipped area at the compression ratio; and a transmitting/receiving unit transmitting the compressed image data from the image compression unit.

The above-mentioned specific character pattern recognition device may be configured so that the specific character pattern recognition device further comprises a data storing unit which stores the compressed image data provided by the image compression unit, together with the result of the recognition processing of the specific character pattern of the vehicle.

Moreover, the above-mentioned specific character pattern recognition device may be configured so that the specific character pattern recognition device further comprises a matching processing unit which performs matching processing between an externally requested vehicle specific character pattern and the result of the recognition processing stored in the data storing unit, and, when a match occurs as a result of the matching processing, the compressed image data is read from the data storing unit and transmitted.

Moreover, in order to achieve the above-mentioned objects, the present invention provides a vehicle monitoring system which includes a plurality of specific character pattern recognition devices and a center which are connected through a communication line, each specific character pattern recognition device comprising: a recognition processing unit performing recognition processing of a specific character pattern of a vehicle based on a taken image data, and the recognition processing unit clipping a vehicle area containing the whole vehicle from the taken image data, and clipping a specific character pattern area from the vehicle area; a compression range/ratio judging unit judging a compression range and a compression ratio based on a result of the recognition processing wherein, when the result of the recognition processing indicates that the specific character pattern cannot be recognized, the compression range and the compression ratio are judged as being the vehicle area and a predetermined low compression ratio, when the result indicates that the specific character pattern is partially recognized, the compression range and the compression ratio are judged as being the specific character pattern area and the low compression ratio, and when the result indicates that the specific character pattern is fully recognized, the compression range and the compression ratio are judged as being the specific character pattern area and a predetermined high compression ratio; an image compression unit which is responsive to a judgment result of the compression range/ratio judging unit, the image compression unit clipping a corresponding area of image data for the compression range from the taken image data, and performing compression processing of the image data of the clipped area at the compression ratio; and a transmitting/receiving unit transmitting the compressed image data from the image compression unit, and the center comprising: a data management table in which the compressed image data received from each specific character pattern recognition device through the communication line are stored; and a display unit displaying the compressed image data.

According to the present invention, the compression range and compression ratio of the taken image data are determined in response to the result of the automatic recognition processing of the vehicle specific character pattern. Even when the vehicle specific character pattern cannot be recognized, the compression processing of the vehicle area, not the full screen, is performed, and the amount of the transmission data can be reduced.

Moreover, the image data of the vehicle area can be displayed at the high compression ratio on the display unit at the center, the possibility of recognition of the vehicle specific character pattern can be increased by viewing the image with the high compression ratio on the display unit. Moreover, when the vehicle specific character pattern can be recognized, the compression processing of the specific character pattern with the further smaller area is performed. Reducing the amount of the transmission data further is possible, and it is possible to easily transmit the compressed image data through the communication network of low bit rate.

Since the ratio of recognition of the vehicle specific character pattern is comparatively high, even when the compressed image data is transmitted continuously, the transmission data in many cases is the highly compressed image data of the specific character pattern area. The amount of the transmission data, even if it includes the data of the recognized vehicle specific character pattern, is comparatively small. It is possible to easily transmit the compressed image data through the communication network of low bit rate.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.

FIG. 1 is a diagram for explaining the outline composition of the vehicle monitoring system in the preferred embodiment of the invention.

FIG. 2 is a block diagram showing the composition of the vehicle monitoring system in the preferred embodiment of the invention.

FIG. 3 is a flowchart for explaining the vehicle monitoring method in the preferred embodiment of the invention.

FIG. 4 is a diagram for explaining the compression range.

FIG. 5 is a block diagram showing the composition of the vehicle monitoring system in another preferred embodiment of the invention.

FIG. 6 is a block diagram showing the composition of the vehicle monitoring system in another preferred embodiment of the invention.

FIG. 7 is a block diagram showing the composition of the conventional vehicle monitoring system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A description will now be given of the preferred embodiments of the present invention with reference to the accompanying drawings.

FIG. 1 shows the outline composition of the vehicle monitoring system in the preferred embodiment of the invention.

In FIG. 1, reference numeral 1 denotes the center, 2 denotes the control processing unit, 3 denotes the display unit, 4 denotes the data management table, 5 denotes the switched network (network), 6 denotes the communication line, such as the telephone line, 7 denotes the recognition device, 8 denotes the camera, and 9 denotes the vehicle. The vehicle monitoring system shown in FIG. 1 is constituted when the connection between the center 1 and the recognition device 7 is established through the telephone line 6 which is accommodated in the switched network 5. A plurality of recognition devices 7 which constitute part of the vehicle monitoring system may be distributed in the highway, the general road or the parking lot, and each recognition device 7 can be connected with the center 10 through the telephone line.

The camera 8 may be arranged at the position where the image of the vehicle running on the highway or the general road is taken, or at the position where the image of the vehicle entering or exiting the parking lot, or the image of the vehicle under parking is taken.

The recognition device 7 is provided with the image processing function, the character pattern recognition processing function, the data transmitting/receiving function, etc. The recognition device 7 processes the taken image data from the camera 8 by using the image processing function, and extracts the specific character pattern area of the vehicle 9 from the processed image data. The recognition device 7 recognizes the vehicle specific character pattern by using the character recognition processing function. In response to the result of the recognition processing, the recognition device 7 clips the area containing the whole vehicle 9 or the specific character pattern area from the taken image data and determines the compression ratio. The recognition device 7 transmits the resulting data (or the transmission data) to the center 1 through the telephone line 6 by using the data transmitting/receiving function.

As shown in FIG. 1, the transmission data in this case comprises the specific character pattern information and the compression image data. The compression image data contains, for example, the compression range indicating the vehicle area or the specific character pattern area, the image quality, the compression data length, and the compressed image data. The specific character pattern information contains, for example, the header information, the position information, the time information, and the vehicle specific character pattern data with the recognition result, such as “12345”.

The control processing unit 2 of the center 1 is provided with the data management table 4, and this data management table 4 stores the transmission data received through the telephone line 6 from the recognition device 7. As shown in FIG. 1, the data management table 4 contains, for every item, the vehicle specific character pattern which is partially omitted, the image data in the compression range, the image quality, and the position/time information.

In the data management table 4 of FIG. 1, for example, “12345” of the specific character pattern column of the item number 1 indicates the case in which the vehicle specific character pattern is fully recognized, the image data thereof indicates the specific character pattern area (or the vehicle number plate region), and the image quality thereof indicates the low level. Namely, the compression range is set to the specific character pattern area, and the reproduction image quality is set to the low level since the compression ratio has been set to the high compression ratio.

Moreover, in the data management table 4 of FIG. 1, “?” of the specific character pattern column of the item number 3 indicates the case in which the vehicle specific character pattern cannot be recognized, the image data thereof indicates the whole vehicle, and the image quality thereof indicates the high level. Namely, the compression range is set to the vehicle area, and the reproduction image quality is set to the high level since the compression ratio has been set to the low compression ratio.

Moreover, in the data management table 4 of FIG. 1, “12?45” of the specific character pattern column of the item number 4 indicates the case in which the characters in the vehicle specific character pattern are partially recognized except for the character “?”, the image data thereof indicates the specific character pattern area, and the image quality thereof indicates the high level. Namely, the compression range is set to the specific character pattern area, and the reproduction image quality is set to the high level since the compression ratio has been set to the low compression ratio.

For example, the case in which the image data of the item number 3 in the data management table 4 is read and displayed on the display unit 3 under control of the control processing unit 2 is considered. In this case, the compressed image data of the vehicle area has been created at the low compression ratio, and such image data is decompressed and displayed. Thus, the image of the vehicle area can be displayed at the high reproduction image quality.

Accordingly, in this case, the specific character pattern area is checked by viewing the display screen, and this makes it possible to read the characters in the specific character pattern area by viewing. In such case, the column of the specific character pattern in the data management table 4 can be corrected to the vehicle specific character pattern currently checked by viewing.

In the vehicle monitoring system of the present embodiment, the compression processing of the vehicle area only is carried out, and the amount of the transmission data can be reduced as compared with the case in which the compression processing of the full screen is carried out.

Moreover, when the image data of the item number 4 in the data management table 4 is read and displayed on the display unit 3 under control of the control processing unit 2, the image of the specific character pattern area can be displayed at the high image quality level. This make it possible to easily check the character “?” which has not been recognized through the automatic recognition processing by viewing the display screen.

In such case, the column of the specific character pattern in the data management table 4 can also be corrected to the vehicle specific character pattern currently checked by viewing. In the vehicle monitoring system of the present embodiment, the compression processing of the specific character pattern area only is carried out, and the amount of the transmission data can be reduced further as compared with the case in which the compression processing of the full screen or the vehicle area is carried out.

In the case in which the vehicle specific character pattern is fully recognized through the automatic recognition like the item number 1, 2 or 6 in the data management table 4, the compression processing of the specific character pattern area is performed at the high compression ratio (which allows the reproduction image quality to be set to the low level), and the amount of the transmission data can be reduced further.

In such case, when the vehicle specific character pattern which is already recognized through the automatic recognition is displayed on the display unit 3, checking the vehicle specific character pattern again can be easily performed even if the reproduction image quality is at the low level.

FIG. 2 shows the composition of the vehicle monitoring system in the preferred embodiment of the invention.

In FIG. 2, reference numeral 10 denotes the center, 11 denotes the transmitting/receiving unit, 12 denotes the control processing unit, 13 denotes the display unit, 14 denotes the data management table, 20 denotes the specific character pattern recognition device, 21 denotes the recognition processing unit, 22 denotes the frame memory, 23 denotes the compression range/ratio judging unit, 24 denotes the image compression unit, 25 denotes the transmitting/receiving unit, 30 denotes the image-taking unit, and 40 denotes the telephone line.

The center 10 is equivalent to the center 1 in FIG. 1, the specific character pattern recognition device 20 is equivalent to the recognition device 7 in FIG. 1, the image-taking unit 30 is equivalent to the camera 8 in FIG. 1, and the telephone line 40 is equivalent to the telephone line 6 in FIG. 1.

Moreover, the control processing unit 12 corresponds to the control processing unit 2 in FIG. 1, the display unit 13 corresponds to the display unit 3 in FIG. 1, and the data management table 14 is equivalent to the data management table 4 in FIG. 1. In addition, in the composition of FIG. 2, the network 5 in FIG. 1 is omitted for the sake of convenience of illustration.

In the vehicle monitoring system of FIG. 2, the image-taking unit 30 continuously takes at a predetermined frame period the image of the vehicle passing position or parking position which is selected as the image-taking range, similar to a television camera. Alternatively, the image-taking unit 30 may be configured so that it takes the image of the vehicle only when the vehicle exists within the image-taking range.

In the specific character pattern recognition device 20, the taken image signal received from the image-taking unit 30 is digitized by the recognition processing unit 21, and stored into the frame memory 22 of the recognition processing unit 21.

In the case in which the image is taken continuously, the recognition processing unit 21 can recognize the difference between the background portion (such as the road) and the moving-vehicle portion of the taken image by taking the difference between the frames at the predetermined time interval. Thus, the recognition processing unit 21 clips the vehicle area containing the vehicle, from the taken image.

Further, the recognition processing unit 21 clips the specific character pattern area (e.g., the vehicle number plate) from the vehicle area, and performs the character recognition processing to recognize the characters or numbers in the specific character pattern area.

The compression range/ratio judging unit 23 controls the compression range and the compression ratio in response to the result of the recognition processing of the vehicle specific character pattern received from the recognition processing unit 21.

As mentioned above, the compression range/ratio judging unit 23 performs the judgment about the compression range and the compression ratio as follows. When the vehicle specific character pattern cannot be recognized, the compression range is determined as being the vehicle area, and the compression ratio is determined as being the predetermined low compression ratio. Moreover, when the vehicle specific character pattern is fully recognized, the compression range is determined as being the specific character pattern area, and the compression ratio is determined as being the predetermined high compression ratio. Furthermore, when the vehicle specific character pattern is partially recognized but the remainder cannot be recognized, the compression range is determined as being the specific character pattern area, and the compression ratio is determined as being the predetermined low compression ratio.

The image compression unit 24 performs clipping and compression processing of the area of the image data of the frame memory 22 according to the judgment signal from the compression range/ratio judging unit 23. The image compression unit 24 transmits the compressed image data to the transmitting/receiving unit 25 through the compression range/ratio judging unit 23, or transmits the compressed image data to the transmitting/receiving unit 25 directly. The transmitting/receiving unit 25 transmits the compressed image data from the specific character pattern recognition device 20 to the center 10 through the telephone line 40.

The center 10 temporarily stores in the data management table 14 the compression image data received at the transmitting/receiving unit 11 under control of the control processing unit 12.

The control processing unit 12 reads the compressed image data of the vehicle with which the vehicle specific character pattern cannot be recognized through the automatic recognition processing, from the data management table 14 automatically or in response to the instructions of the operator. The compressed image data is subjected to the expansion processing in accordance with the compression ratio specified therein, and the expanded image data is displayed on the display unit 13.

In this case, since the image of the vehicle area can be displayed at the high image-quality level, it is possible to increase the possibility that the vehicle specific character pattern be visually recognized by viewing the display screen.

FIG. 3 is a flowchart for explaining the vehicle monitoring method in the preferred embodiment of the invention.

As shown in FIG. 3, the taken image signal received from the image-taking unit 30 (see FIG. 2) is digitized and stored in the frame memory 22 (S1). The difference data (the outline of the vehicle) between the background image data and the taken image data is extracted (S2).

The difference data extracted at the step S2 takes the difference between the frames at the predetermined time interval and indicates the difference between the background portion (such as the road) and the moving-vehicle portion of the taken image. The vehicle area containing the vehicle is clipped from the taken image data using the difference data (S3).

And it is determined whether the vehicle can be recognized or not (S4). Vehicles generally have various kinds of form, but they have the size and the form different from the pedestrian etc. Thus, the vehicles and the other moving objects are distinguishable.

When the vehicle cannot be recognized using the difference data, the control is transferred to the step S1. On the other hand, when the vehicle has been recognized, the control is transferred to the next step S5.

In the step S5, extraction processing of the specific character pattern area from the clipped area is performed. For example, the histogram with respect to the horizontal direction and the vertical direction can be created, and the area of the rectangular specific character pattern can be extracted based on this histogram.

Alternatively, for example, the background color of the specific character pattern is set to white, and the generally rectangle area where the color of the background other than the characters is white can be extracted as the specific character pattern area.

Next, it is determined whether the specific character pattern has been recognized (S6). When the result at the step S6 is affirmative, the character area is clipped and the numeric values of the characters of the specific character pattern are determined by the pattern matching (S7). Namely, the character recognition is performed for the clipped character area through the pattern matching, the feature point extraction, etc.

Next, it is determined whether all the characters in the specific character pattern area have been recognized, or it is determined whether the vehicle specific character pattern has been fully recognized (S8).

When the result at the step S8 is affirmative, the image data of the vehicle specific character pattern area (which is the clipped area) is compressed at the high compression ratio (which is specified as the compression ratio in this case) (S9).

When the result at the step S8 is negative (i.e., when the vehicle specific character pattern has been recognized partially), only the characters in the specific character pattern which have been recognized are determined (S12). And the image data of the vehicle specific character pattern area (which is the clipped area) is compressed at the low compression ratio (which is specified as the compression ratio in this case) (S13).

On the other hand, when the specific character pattern cannot be recognized, or when the vehicle specific character pattern has not been recognized at all, the image data of the vehicle area (which is the clipped area) is compressed at the low compression ratio (which is specified as the compression ratio in this case) (S11).

Subsequently, the transmission data as shown in FIG. 1 is created, and the compressed image data with the specific character pattern is transmitted from the specific character pattern recognition device 20 to the center 10 (S10).

FIG. 4 is the diagram for explaining the compression range. In FIG. 4, (a) indicates the taken image created by the image-taking unit 30 (see FIG. 2). For example, the image data stored in the frame memory 22 is read out and displayed on the display screen.

And when the extraction of the specific character pattern cannot be performed, or when the automatic recognition of the vehicle specific character pattern cannot be performed at all, the vehicle area is clipped from the taken image data as shown by (b) in FIG. 4. The image data of the vehicle area is compressed at the low compression ratio by the image compression unit 24, allowing the image quality to be set at the high level.

Therefore, when the compressed image data in this case is received at the center 10, the image data is expanded and displayed on the display unit 13. In this case, the image of the vehicle with the high image quality level can be displayed, and the specific character pattern area can be checked by viewing the display screen, which increases the possibility that the vehicle specific character pattern be recognized by viewing.

Moreover, when the vehicle specific character pattern is partially recognized through the automatic recognition, the image data of the specific character pattern area is compressed at the low compression ratio.

Therefore, the specific character pattern area is clipped from the taken image data as shown by (c) or (d) in FIG. 4, and, when the compressed image data of the specific character pattern area with the low compression ratio is received at the center 10, the image data is expanded and displayed on the display unit 13. In this case, the image of the specific character pattern area with the high image quality level can be displayed, and the specific character pattern area can be checked by viewing the display screen, which increases the possibility that the vehicle specific character pattern be fully recognized by viewing.

Next, FIG. 5 shows the composition of the vehicle monitoring system in another preferred embodiment of the invention.

In FIG. 5, the elements which are the same as corresponding elements in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted.

In the specific character pattern recognition device 20 of FIG. 5, the data storing unit 26 is provided. This data storing unit 26 is formed by a semiconductor integrated circuit memory or a hard disk drive unit which is provided to accumulate the image data. The data storing unit 26 is provided to accumulate the image data, and to accumulate the compression data of the image compression unit 24, the recognition result of the vehicle specific character pattern by the recognition processing unit 21, and the judgment result of the compression range/ratio judging unit 23.

For example, the compression data are accumulated in the data storing unit 26 in the format equivalent to the format of the data management table 4 or the format of the transmission data shown in FIG. 1.

And the data storing unit 26 is searched from the center 10 in accordance with the time specified by the center 10 or in accordance with the vehicle specific character pattern specified by the center 10. The compression data which is retrieved and extracted is read out from the data storing unit 26. The compression data is transmitted from the transmitting/receiving unit 25 to the telephone line 40 in the format of the transmission data (which is, for example, shown in FIG. 1).

Therefore, it is possible for the present embodiment that, only when the necessity occurs in the center 10, the automatically recognized vehicle specific character pattern and the compression image data be collected from the specific character pattern recognition device 20.

FIG. 6 shows the composition of the vehicle monitoring system in another preferred embodiment of the invention.

In FIG. 6, the elements which are the same as corresponding elements in FIG. 2 or FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted.

In the specific character pattern recognition device 20 of FIG. 6, the matching processing unit 27 is provided. When the vehicle specific character pattern is specified by the center 10, the matching processing unit 27 searches the vehicle specific character pattern stored in the data storing unit 26, and carries out matching between the specified vehicle specific character pattern and the recognized vehicle specific character pattern. If the coincidence of the matching occurs, the compression image is read from the data storing unit 26, and the transmission data in the format shown in FIG. 1 is transmitted from the transmitting/receiving unit 25 to the center 10 through the telephone line 6.

The present invention is not limited to the above-described embodiments, and variations and modifications may be made without departing from the scope of the present invention. For example, the camera 8 or the image-taking unit 30 may be constituted by a digital camera, so that the image of the vehicle is taken using the digital camera at intervals of a fixed time period. Moreover, two frame memories 22 may be provided in order to perform the processing of creating the difference data more easily. Moreover, the vehicle monitoring system may be controlled to change the compression ratio to one of the multiple stages corresponding to the number in which the vehicle specific character pattern is recognized.