Patent Publication Number: US-2013235193-A1

Title: License Plate Image-Pickup Device and Image White Balance Adjustment Method Thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Taiwan Patent Application No. 101107981, filed on Mar. 9, 2012, in the Taiwan Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a license plate image-pickup device and an image white balance adjustment method, and more particularly to the license plate image-pickup device and the image white balance adjustment method that use a license plate color to perform a white balance adjustment. 
     2. Description of Related Art 
     As science and technology advance, and their applications become popular, our life is improved by science and technology to give us tremendous convenience and even assure our safety. For example, automobile equipments of modern motor vehicles generally come with many electronic functions such as driving recording, abnormal car condition recording, automatic braking, reverse radar warning, and car condition communication, etc, wherein driving recorders are the most popular. 
     Most driving recorders have the real-time imaging function, and users can use a display device to review a recorded situation from a driving recorder. To optimize the recording effect, some of driving recorders are equipped with an image white balance mechanism to provide a better real and actual situation of the recorded image. However, most white balance mechanisms of the conventional driving recorder use the whole image color as reference data to categorize a neutral color and a non-neutral color to perform a white balance adjustment of an image according to the category. Since the driving speed is fast, even two consecutive images have a significant difference. When the neutral color and non-neutral color are categorized, there is no color reference value provided as a reference, so that it is difficult to perform an accurate white balance adjustment of the image. 
     It is an important subject for related designers or manufacturers to design a license plate image-pickup device and an image white balance adjustment method to achieve the effect of showing images of the actual road condition accurately, so that the inventor of the present invention have designed a license plate image-pickup device and an image white balance adjustment method to overcome the aforementioned drawbacks. 
     SUMMARY OF THE INVENTION 
     In view of the aforementioned problems of the prior art, it is a primary objective of the invention to provide a license plate image-pickup device and an image white balance adjustment method to achieve the effects of capturing an image and performing a white balance adjustment of the image. 
     To achieve the foregoing objective, the present invention provides a license plate image-pickup device applied in a mobile vehicle, and the license plate image-pickup device comprises: an image-sensing module, a recognition module, a database and a processing module. The image-sensing module senses a scene to produce an image. The recognition module recognizes an object contained in the image and a license plate color feature contained in the object to produce a recognition parameter set. The database stores parameter sets of reference objects and reference license plate color features respectively corresponding to the reference objects. The processing module searches the reference objects in the database according to the recognition parameter set, to obtain a corresponding reference license plate color feature, and adjusts the white balance of the image according to the corresponding reference license plate color feature. 
     Wherein, the recognition module further recognizes a road surface contained in the image and the processing module determines the road surface according to a reference road surface color feature. 
     Wherein, the processing module adjusts the white balance of the image according to the corresponding reference license plate color feature and the reference road surface color feature. 
     Wherein, the license plate image-pickup device further comprises a positioning module for detecting a position of the license plate image-pickup device to produce a position data. 
     Wherein, the database further comprises parameter sets of reference position data respectively corresponding to the reference objects and the processing module compares the corresponding reference position data in the database according to the position data, and obtains the reference object and license plate color feature in the database according to the reference position data, and the processing module adjust the white balance of the image according to the reference license plate color feature corresponding to the position data. 
     Wherein, the license plate image-pickup device further comprises a calibrating module provided for a user to set a user parameter, so that the processing module adjusts the white balance of the image according to the user parameter and the corresponding reference license plate color feature. 
     To achieve the foregoing objective, the present invention further provides an image white balance adjustment method comprising steps of: providing an image-sensing module to sense a scene to produce an image; using a recognition module to recognize an object contained in the image and a license plate color feature contained in the object to produce a recognition parameter set; providing a database to stores parameter sets of reference objects and reference license plate color features respectively corresponding to reference objects; and using a processing module to search the reference objects and reference license plate color features in the database according to the recognition parameter set, and adjust the white balance of the image according to the corresponding reference license plate color feature. 
     Wherein, the method further comprises steps of: using the recognition module to recognize a road surface contained in the image; using the processing module to determine the road surface according to a reference road surface color feature ; and using the processing module to adjust the white balance of the image according to the corresponding reference license plate color feature and the reference road surface color feature. 
     Wherein, the method further comprises the step of providing a positioning module to detect a position of the license plate image-pickup device to produce a position data. 
     Wherein, the database further comprises parameter sets of reference position data respectively corresponding to the reference objects, and the image white balance adjustment method further comprises the steps of: using the processing module to compare the corresponding reference position data in the database according to the position data, and obtaining the corresponding the reference object and the license plate color feature in the database according to the reference position data; and using the processing module to adjust the white balance of the image according to the reference license plate color feature corresponding to the position data. 
     Wherein, the method further comprises the step of using a calibrating module provided for a user to set a user parameter, such that the processing module adjusts the white balance of the image according to the user parameter and the corresponding reference license plate color feature. 
     To achieve the foregoing objective, the present invention further provides a license plate image-pickup device applied in a mobile vehicle and comprising: an image-sensing module, for sensing a scene to produce an image; a recognition module, for recognizing an object contained in the image and a license plate color feature contained in the object to produce a recognition parameter set; a database, for storing parameter sets of reference objects and reference license plate color features respectively corresponding to the reference objects; a processing module, for searching the reference objects in the database according to the recognition parameter set, and determining the license plate color feature according to the reference license plate color feature; and a white balance adjustment module, for adjusting the white balance of the image according to the reference license plate color feature. 
     Wherein, the recognition module further recognizes a road surface contained in the image and the processing module determines a reference road surface according to the road surface color feature. 
     Wherein, the processing module adjusts the white balance of the image according to the corresponding reference license plate color feature and the reference road surface color feature. 
     Wherein, the license plate image-pickup device further comprises a positioning module for detecting a position of the license plate image-pickup device to produce a position data. 
     Wherein, the database further comprises parameter sets of reference position data respectively corresponding to the reference objects, and the processing module compares the corresponding reference position data in the database according to the position data, and obtains the corresponding the reference object and the license plate color feature in the database according to the reference position data, and the processing module adjust the white balance of the image according to the reference license plate color feature corresponding to the position data. 
     Wherein, the license plate image-pickup device further comprises a calibrating module provided for a user to set a user parameter, and the processing module adjusts the white balance of the image according to the user parameter and the reference license plate color feature. 
     In summation, the license plate image-pickup device and the image white balance adjustment method of the present invention have one or more of the following advantages: 
     (1) The license plate image-pickup device and the image white balance adjustment method of the present invention create files of the present existing license plate colors to serve as reference colors of the white balance adjustment to achieve a more accurate white balance adjustment. 
     (2) The license plate image-pickup device and the image white balance adjustment method of the present invention provide users a way of calibrating related colors for the image processed after the white balance adjustment in order to obtain the users&#39; desired image. 
     (3) The license plate image-pickup device and the image white balance adjustment method of the present invention further create the present existing license plate color in each country and combine with the global positioning system to achieve the effect of a global application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a license plate image-pickup device of the present invention. 
         FIG. 2  is a first schematic view of a license plate image-pickup device in accordance with a first preferred embodiment of the present invention. 
         FIG. 3  is a second schematic view of a license plate image-pickup device in accordance with the first preferred embodiment of the present invention. 
         FIG. 4  is a block diagram of a license plate image-pickup device in accordance with the first preferred embodiment of the present invention. 
         FIG. 5  is a flow chart of an image white balance adjustment method of the present invention. 
         FIG. 6  is a schematic view of an image white balance adjustment method in accordance with a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The technical contents and characteristics of the present invention will be apparent with the detailed description of a preferred embodiment accompanied with related drawings as follows. For simplicity, same numerals are used in the following preferred embodiment to represent respective same elements. 
     With reference to  FIG. 1  for a block diagram of a license plate image-pickup device of the present invention, the license plate image-pickup device  10  comprises: an image-sensing module  11 , a recognition module  12 , a database  13  and a processing module  14 . The image-sensing module  11  senses a scene  20  to produce an image  111 . Wherein, the image-sensing module  11  comprises a camera lens, a photo sensor such as a complementary metal oxide semiconductor (CMOS) or charge coupled device (CCD) sensor, an analog/digital circuit, and an image processor. The recognition module  12  recognizes an object  112  contained in the image  111  and a license plate color feature  113  contained in the object  112 , to produce a recognition parameter set  121 . The database  13  stores parameter sets of reference objects  131  and reference license plate color features  132  respectively corresponding to reference objects  131 . Wherein, the database  13  can be a flash Memory. The processing module  14  searches the corresponding reference object  131  and reference license plate color feature  132  in the database  13 , according to the recognition parameter set  121 , and adjusts the white balance of the image  111  according to the corresponding reference license plate color feature  132 . Wherein, the recognition module  12  can be a digital signal processor (DSP), and the processing module  14  can be a microprocessor with the architecture of an advanced RISC machine (ARM) such as the common ARMv7 or ARMv8. 
     With reference to  FIGS. 2 to 4  for a block diagram and first and second schematic views of a license plate image-pickup device in accordance with the first preferred embodiment of the present invention respectively, the license plate image-pickup device  10  is applied in a mobile vehicle  40  and used as a driving recorder  30 . In  FIGS. 2 and 3 , the driving recorder  30  comprises a license plate image-pickup device  10  and a display device  21 . The license plate image-pickup device  10  is electrically coupled to the display device  21 . The license plate image-pickup device  10  comprises: an image-sensing module  11 , a recognition module  12 , a database  13 , a processing module  14 , a positioning module  15  and a calibrating module  16 . Wherein, the display device  21  can be integrally formed with the license plate image-pickup device  10  according to the actual requirement, and the setup button  212  can be a physical button or a touch screen. The setup button  212  is coupled to the calibrating module  16 . The driving recorder  30  senses a scene  20  through the license plate image-pickup device  10  and the image processed after the white balance adjustment is displayed on the display device  21 . 
     With reference to  FIG. 4  together, the image-sensing module  11  senses a scene  20  to produce an image  111 . The recognition module  12  recognizes an object  112  and a license plate color feature  113  contained in the object  112  from the image  111  to produce a recognition parameter set  121 . The positioning module  15  detects the position of the mobile vehicle  40  to produce position data  151 . Wherein, the positioning module  15  can be a global positioning system (GPS). The processing module  14  compares the reference position data  133  in the database  13  according to the position data  151  and searches the corresponding reference object  131  and the corresponding reference license plate color feature  132  in the database  13  according to the recognition parameter set  121 . Wherein, the database  13  stores parameter sets of reference objects  131 , parameter sets of reference license plate color features  132  and parameter sets of reference position data  133 , and the reference license plate color feature  132  corresponds to the reference object  131 , and the reference object  131  corresponds to the reference position data  133 . More specifically, the database  13  stores reference objects corresponding to different country license plate (such as a green license plate for large vehicles in Country A or a white license plate for small vehicles in Country B). The display device  21  comprises a display screen  211  and a plurality of control buttons (setup button  212 ). 
     The processing module  14  determines the license plate color feature  113  according to the reference license plate color feature  132 , so as to adjust the white balance of the image  111  to produce an image signal  101 . To speed up the image processing, a white balance module (not shown in the figure) can be installed, so that the processing module  14  is provided for the function of replacing the license plate color feature  113  only, and the white balance module further to adjust the white balance of the whole image. The display device  21  receives and displays the image signal  101  on the display screen  211 . The users can set the image signal  101  in the display screen  211  according to their personal preference through the setup button  212  of the display device  21 . More specifically, the setup button  212  is coupled to the calibrating module  16 , and the setup button  212  senses a press operation made by the users to produce the corresponding user parameter, and the processing module  14  adjust the color of the image  111  which has been adjusted the white balance according to the user parameter. 
     In short, the license plate image-pickup device  10  is combined a display device  21  to serve as a driving recorder  30 . The license plate image-pickup device  10  senses a road condition (the scene  20 ) of an image-sensing module  11  to produce an image  111 . The recognition module  12  recognizes the car (the object  112 ), the license plate color (the license plate color feature  113 ) from the image  111  to produce a recognition parameter set  121  (such as Large Vehicle—Green License Plate). The positioning module  15  detects the current position of the mobile vehicle  40  to produce position data  151  (such as Country A—District B). The processing module  14  searches the corresponding reference object  131 , the reference license plate color feature  132  and the reference position data  133  in the database  13  according to the position data  151  (Country A—District B) and the recognition parameter set  121  (Large Vehicle—Green License Plate) and further determines the license plate color feature  113  according to the reference license plate color feature  132  to adjust the white balance of the image  111 . In other words, the processing module  14  searches the corresponding reference license plate color (or the reference green color) in the database  13  according to the detected Country A—District B—Large Vehicle—Green License Plate, and determines the originally detected green license plate by the reference license plate color (or the reference green color) to adjust the white balance of the image  111  and display the processed image on the display screen  211 . The user can perform a color related calibration (such as a color temperature calibration) of the display screen from the setup button  212 . 
     With reference to  FIG. 5  for a schematic view of an image white balance adjustment method of the present invention, the image white balance adjustment method can be applied to a license plate image-pickup device  10  and comprises the following steps: 
     S 51 : Provide an image-sensing module to sense a scene to produce an image. 
     S 52 : Use a recognition module to recognize an object contained in the image and a license plate color feature contained in the object to produce a recognition parameter set. 
     S 53 : Provide a database to store parameter sets of reference objects and reference license plate color features respectively corresponding to the reference objects. 
     S 54 : Use a processing module to search the reference objects and the reference license plate color features in the database according to the recognition parameter set, and adjust the white balance of the image according to the corresponding reference license plate color feature. 
     The details and implementation method of the image white balance adjustment method of the present invention have been described in the section of the license plate image-pickup device of the present invention, and thus will not be described again. 
     With reference to  FIG. 6  for a schematic view of an image white balance adjustment method in accordance with a preferred embodiment of the present invention, the image white balance adjustment can be applied to a license plate image-pickup device  10 , and comprises the following steps: 
     S 61 : Provide an image-sensing module to sense a scene to produce an image. 
     S 62 : Use a color preference recognition module to recognize parameter sets of sample color features contained in the image to produce positive sample recognition parameter set and negative sample recognition parameter set. 
     S 63 : Use the color preference recognition module to recognize an object contained in the image and a license plate color feature contained in the object to produce a recognition parameter set. 
     S 64 : Use the color preference recognition module to recognize a road surface contained in the image to produce a road surface recognition parameter set. 
     S 65 : Provide a database to stores parameter sets of reference objects, reference license plate color features and reference road surface color features. 
     S 66 : Use a processing module to search the reference objects and reference license plate color feature in the database according to the recognition parameter set, and determines the license plate color feature according to the reference license plate color feature. 
     S 67 : Use the processing module to search the corresponding reference road surface color feature in the database according to the road surface recognition parameter set. 
     S 68 : Use the processing module to receive the positive and negative sample preference recognition parameter set, the reference license plate color feature, and the reference road surface color feature to produce positive color (such as neutral color) data and negative color (such as non-neutral color) data. 
     S 69 : Use the processing module to adjust the white balance of the image according to the positive color data and the negative color data. 
     The details of the image white balance adjustment of this preferred embodiment are similar to those described in the section of the license plate image-pickup device of the present invention, and thus will not be repeated.