Abstract:
A method and an apparatus for improving the image quality. The method comprises steps of producing image correcting information to decrease errors in the image to be produced by a camera module ( 109, 111, 112 ) by comparing the image taken by said camera module ( 109, 111, 112, 113 ) with a test image, storing the image correcting information produced and identifying information related to said image correcting information in the memory of an electronic peripheral device ( 104, 106 ), receiving the image produced by said camera module ( 109, 111, 112, 113 ) and a second piece of identifying information related to said image in the electronic peripheral device ( 104, 106 ), comparing said identifying information with said second piece of identifying information in said peripheral device, and performing an image improvement operation on said image in said peripheral device in response to the comparison carried out.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to utilization of camera properties in image processing. The invention especially, but not necessarily, relates to improvement of the quality of an image produced by a digital camera. 
       BACKGROUND OF THE INVENTION 
       [0002]    In digital cameras and digital video cameras an optical image is converted into an electronic format by an image sensor, which is typically a photosensitive semiconductor element (Charge Coupled Device CCD or Complementary Metal oxide Semiconductor CMOS). This element is a plate known as a detector matrix which consists of small and regular photosensitive and colour-sensitive picture elements, i.e. pixels. The resolution of the matrix varies according to its physical size and fineness. An image sensor typically comprises hundreds of thousands of pixels, e.g. 640×480=307 200 pixels are used in VGA resolution (video graphics array). Utilization of advanced CMOS technology in the production of image sensors has enabled integration of digital and analogue electronics and the image sensor into the same semiconductor element. The size and weight of the camera module have been reduced, which has made it possible to integrate it into smaller and smaller electronic devices, such as mobile imaging phones. 
         [0003]    The quality of an image produced by a camera module is usually proportioned to the display properties of the communication device, e.g. a mobile imaging phone. On a small screen the size of the picture elements that create an image, i.e. pixels, is smaller than in monitors used in offices, and thus at a certain resolution the sharpness of the image appears to be better to the human eye. The image quality on the screen of the communication device can be improved e.g. by providing the image with a greater contrast and more saturated colours. This makes the image seen on the screen of the communication device appear more natural to the viewer and improves its visibility. 
         [0004]    When an image produced by a mobile imaging phone is transferred e.g. onto a computer screen which has better display properties than the mobile imaging phone, errors will appear in the image on the computer screen, such as discoloration or distortions. Due to this the image quality may have to be adjusted or improved. Furthermore, since the computing capacity of computers is nowadays considerably greater, a better image quality can be achieved e.g. using a computer program intended for image improvement. However, the user may find computer program of this kind difficult to use, and thus the user must have basic knowledge about the function and properties of image processing software to achieve the desired result in image improvement. Furthermore, the image improvement operation has to be performed separately on each image, which the user may find troublesome and time consuming. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a method and an apparatus for improving the image quality and especially, but not necessarily, for improving the quality of an image produced in a mobile imaging phone in a peripheral device, such as a computer or a server. Properties resulting from the errors of the camera module used for taking images are stored as image correcting information either in the memory of the camera module or in the memory of the electronic device into which the camera module is integrated or to which it is otherwise connected. Alternatively, the correcting information can be stored in the memory of a peripheral device, such as a computer or a server, which is capable of processing the image information produced by the camera module. 
         [0006]    The image correcting information of the camera module is stored preferably during the manufacture of the camera module or the electronic device, such as a mobile imaging phone. The errors the camera module has caused in the image it has produced, such as optical distortions of the camera module lens, discoloration, and problems resulting from the quality of the camera module, such as noise and focus errors, can be reduced by comparing the image taken by the camera module and a test image. One or more image correcting parameters obtained as a result of the comparison are stored as image correcting information. The parameters are preferably stored in the memory of the server, but the image correcting information can also be stored in the memory of the camera module, mobile imaging phone or computer, for example. Storing of the image correcting information during the manufacturing process improves the usability of the device, for example. In that case image conversion does not require information on the properties of the device that has taken the image (camera module, mobile imaging phone) because this information has been stored in the device in advance. Thus image processing can be automated further and made faster. Transmission of the image in the original format e.g. from a mobile imaging phone reduces the amount of capacity required from the mobile imaging device because image processing is not carried out until in a peripheral device, such as a computer or a server. 
         [0007]    A first aspect of the invention relates to a method of improving the quality of an image produced by a camera module in an electronic peripheral device, which is capable of processing said image, characterized in that the method comprises: storing image correcting information related to said camera module in the memory of the electronic peripheral device, receiving the image produced by said camera module and identifying information related to said image correcting information in said electronic peripheral device, and performing an image improvement operation on said image in said peripheral device using the image correcting information to which said received identifying information relates. 
         [0008]    A second aspect of the invention provides an electronic peripheral device for improving the quality of an image produced by a camera module in said peripheral device, which is capable of processing said image, characterized in that said peripheral device comprises: a memory for storing image correcting information related to said camera module in the memory of said peripheral device, receiving means for receiving the image produced by said camera module and identifying information related to said camera module, and image improvement means for improving the quality of said image using in image improvement the image correcting information to which said received identifying information relates. 
         [0009]    A third aspect of the invention provides a system for improving the quality of an image produced by a camera module in an electronic peripheral device, the system comprising at least one camera module which can produce an image and at least one electronic device which can transmit said image and identifying information related to the image to an electronic peripheral device, characterized in that the system further comprises: a memory for storing the image correcting information related to said camera module for said peripheral device, means for transmitting the image produced by said camera module and the identifying information related to said image correcting information to a peripheral device, and image improvement means for performing an image improvement operation to improve the quality of said image using the image correcting information to which said identifying information relates. 
         [0010]    A fourth aspect of the invention provides a computer program product for improving the quality of an image produced by a camera module in an electronic peripheral device, which is capable of processing said image, characterized in that the computer program product comprises: computer program means for making said peripheral device store the image correcting information related to said camera module in the memory of said peripheral device, computer program means for making said peripheral receive the image produced by said camera module and identifying information related to said image correcting information, and computer program means for making said peripheral device perform image improvement to improve the quality of said image using the image correcting information to which said received identifying information relates. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    In the following, the invention will be described in greater detail with reference to the accompanying drawings, in which 
           [0012]      FIG. 1  illustrates a system according to an embodiment of the invention, 
           [0013]      FIG. 2  is a flow chart showing a method according to an embodiment of the invention, 
           [0014]      FIG. 3  illustrates a camera module according to an embodiment of the invention, 
           [0015]      FIG. 4  illustrates a communication device according to an embodiment of the invention, and 
           [0016]      FIG. 5  illustrates a peripheral device according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  illustrates a system according to an embodiment of the invention, the system comprising one or more mobile imaging phones  101 ,  102 , which comprise a camera module  111 ,  112 . The system further comprises a server  106  and a communication network  103 . An image produced by the mobile imaging phone  101 ,  102  can be transmitted over the network  103  to a server  106 , which can store the image in a storage medium  108 , or print the image by a printer  107 . The system may also comprise e.g. a communication device  110 , which can communicate over the network  103 , and a computer  104 , which can receive the image produced by the mobile imaging device  101 ,  102  e.g. over the network  103  and e.g. print the image by a printer  105 . A camera module (references  109 ,  113 ) can be connected to the communication device  110  and the computer  104  for transmitting the image produced over the communication network  103  to a server  106 , for example. 
         [0018]    The image correcting information of the camera module  109 ,  113  is stored in the memory of the server  106  preferably during the manufacture of the camera module. The image correcting information of the camera module  113  can also be stored in the memory of the computer  104 , for example, and the image correcting information of the camera module  109  in the memory of the communication device  110 , for example. The image correcting information of the camera module  111 , 112  is stored in the memory  108  of the server  106  preferably during the manufacture of the camera module or the mobile imaging phone  101 ,  102 . The image correcting information of the camera module  111 ,  112  can also be stored in the memory of the mobile imaging phone  101 ,  102  or the computer  104 . 
         [0019]    The mobile imaging phone  102  can receive and transmit images produced by the camera module to another mobile imaging phone  101 , computer  104 , or server  106  e.g. over a Bluetooth connection or a communication network  103 , such as a mobile communication network or the Internet. The image produced by the camera module  112  of the mobile imaging phone  102  can be transmitted to the server  106 , for example. The image to be transmitted is also provided with an identifier by means of which the server  106  can identify the mobile imaging phone  112  that has transmitted the image and perform an image improvement operation on the image received using the image correcting information that corresponds to the identifying information and is stored in the memory  108 . The server  106  can store the improved image in the memory  108 , or if the user of the mobile imaging device  112  so wishes, transmit the image to a printing service for printing by a printer  107 . The printing service can be implemented e.g. as follows: the user of the mobile imaging phone  112  informs the server  106  of his/her name and address when transmitting an image, after which the printed image can be mailed to the user of the mobile imaging phone  112 , for example. The user of the mobile imaging phone  102  can, if he/she so wishes, retrieve the improved image from the memory  108  for the computer  104  later e.g. via the Internet network and print the image by the printer  105 . 
         [0020]    The camera module  109  can be connected to the communication device  110  e.g. by a cable, a Bluetooth connection or an optical connection, such as an infrared connection. The image produced by the camera module  109  can be transmitted e.g. by the communication device  110  over the communication network  103  to the server  106 . The identifier of the camera module  109  is also transmitted at the same time so that the server  106  can perform an image improvement operation on the basis of the image correcting information related to the identifier of the camera module  109 . 
         [0021]    The camera module  113  can be connected to the computer e.g. by a cable, a Bluetooth connection or an optical connection, such as an infrared connection. The image produced by the camera module  113  can be transmitted e.g. by the computer  104  over the communication network  103  to the server  106 . The identifier of the camera module  113  is also transmitted at the same time so that the server  106  can perform an image improvement operation on the basis of the image correcting information related to the identifier of the camera module  113 . Alternatively, the image correcting information corresponding to the identifier of the camera module  113  can be retrieved for the computer  104 , and thus the computer  104  can perform an image improvement operation on the image produced by the camera module  113 . 
         [0022]    The computer  104  may be a portable computer or a workstation and it is capable of receiving images produced by the mobile imaging phone  102  either via a communication network  103 , e.g. the Internet, or on the Bluetooth connection or on a similar wireless connection, or over a cable connecting the devices. From the image information the computer  104  receives it can separate camera information which is associated with image information in the mobile imaging phone. The computer  104  can process the images to be displayed on the basis of the above-mentioned camera information. A printer  105  can also be connected to the computer  104  for printing the images. The computer can display the processed images by means of a monitor or the above-mentioned printer. 
         [0023]      FIG. 2  shows a method according to an embodiment of the invention. In step  201  image correcting information of the camera module is produced, preferably during the manufacture of the camera module. If the camera module is integrated into an electronic device, such as a mobile imaging phone, the image correcting information can be produced during the manufacture of said mobile imaging phone. Alternatively, said image correcting information can be produced e.g. when the camera module or the mobile imaging phone is used for the first time. 
         [0024]    The image correcting information is produced by comparing the image taken by the camera module with a test image, and image correcting parameters can be generated on the basis of this comparison according to the error type. The correcting information may include optical errors or image correcting parameters for correcting errors resulting from the quality of the camera module. Optical errors include faults the camera module lens causes in the image and colours. Errors resulting from the quality of the camera module include fixed pattern noise caused by the pixel structure, i.e. thermal noise, which increases as the amount of light decreases. Focus errors, i.e. crispening errors, occur particularly in connection with lenses with a fixed focus, e.g. the whole image is not focused. In that case the centre of the image, for example, can be sharp whereas the edges are fuzzy. Noise and sharpness are geometrical distortions that change radially from the centre of the optics, in which case the image correcting parameters are expressed as the centre of distortion and elliptic form for each colour component R, G and B (red, green and blue). The darkness of the image also changes radially towards the image edges. Darkness can be eliminated e.g. using a function of the 6 th  order having the form 1+ar 2 +br 4 +cr 6 , where r is the distance from the centre and constants a, b and c are numbers that are defined on the basis of the test image. 
         [0025]    In step  202  the correcting information is stored preferably in the memory of the peripheral device, such as a server, a mobile imaging phone or a computer, but it can also be stored in the memory of the camera module. The identifying information of the camera module is stored at the same time. Alternatively, the correcting information can be transferred from the memory of the camera module, mobile imaging phone or computer into the memory of the server e.g. by transmitting the correcting information and identifying information of the camera module, mobile imaging phone or computer to the server. The server stores the correcting information and identifying information and links these data with each other. The server can perform an image improvement operation on the image information it has received on the basis of the correcting information stored in advance and the identifier it has received. 
         [0026]    In step  203  an image is produced in the camera module or mobile imaging phone. The image can be a still image or a video image which can be stored e.g. in the memory of said mobile imaging phone. 
         [0027]    In step  204  the identifying information of the camera module or the mobile imaging phone and the image information are transmitted to a peripheral device, such as a server or a computer. The identifying information can alternatively be inserted into the above-mentioned image information in the mobile imaging phone, for example. 
         [0028]    In step  205  the image information and correcting information are received by a peripheral device, such as a server or a computer, and the image improvement operation is performed on the basis of the correcting information. 
         [0029]      FIG. 3  illustrates a camera module  300  according to an embodiment of the invention. The camera module comprises a memory or a similar dataslot  301  for the image correcting information, one or more optical lenses  302 , a photosensitive CMOS element or a CCD sensor element  303 , a control unit  304  for controlling the sensor element, a programmable analogue amplifier  305  (Programmable Gain Amplifier PGA). An analogue image signal is converted into a digital format by an AD converter  306 , after which it can be processed (reference  307 ) by different image processing operations e.g. by adjusting the colour balance and/or the white balance. Via the connection  308  the image signal is transmitted e.g. into the memory of the electronic device, such as the mobile imaging phone, or for display on the screen of the mobile imaging phone. 
         [0030]    The correcting information is stored in the memory  301  of the camera module, preferably during its manufacture. The memory  301  also comprises the identifier of the camera module, by means of which the peripheral device can identify the camera module and perform an image improvement operation on the image information corresponding to the identifying information. 
         [0031]      FIG. 4  illustrates a communication device  400  according to an embodiment of the invention, the communication device comprising a camera module  300  for producing an image onto a screen  406  or into a memory  404 , a transceiver  402  and an antenna  408  for transmitting and receiving data, e.g. image information, wirelessly, at least one application  405  for carrying out operations of the communication device, a processor  403  and a memory  404  for performing operations of the communication device  400  and the application  405 , a keyboard  407  for feeding commands into the communication device  400 . In addition, the communication device  400  comprises image correcting information stored in the memory or in a similar storage medium  409 . The memory  404  may further comprise the identifier of the communication device, by means of which the peripheral device can identify the image information transmitted by the communication device and associate the image information with the corresponding image correcting information. 
         [0032]    The image correcting information is stored in the memory  409  preferably during the manufacture of the communication device or it can be stored in a storage medium, such as a CD, a DVD, a floppy disk or the like, in advance in some other manner. Alternatively, the correcting information can be produced afterwards, e.g. when the communication device is used for the first time. The camera module of the communication device  400  is used for producing image information which is compared with the test image. The comparison can be performed and the image correcting information produced e.g. by a computer or a similar device. The result of the comparison is used for producing image correcting information, which comprises at least one parameter that describes the interference in the image. 
         [0033]    The image information produced by the communication device is transmitted together with the image correcting information to a peripheral device, such as a server or a computer, which performs an image improvement operation on said image information on the basis of said image correcting information. If the image correcting information is already stored in the peripheral device, the identifying information of the communication device can be optionally transmitted with the image information. 
         [0034]      FIG. 5  illustrates a peripheral device  500  according to an embodiment of the invention. The peripheral device is preferably a server, but it may also be a computer. The peripheral device  500  comprises a storage medium  501  for storing image correcting information, a processor  502  and a memory  504  for controlling the operations of the peripheral device, a network interface  507  for receiving the image information and the correcting information and for transmitting corrected image information. The peripheral device  500  also includes a storage interface for storing the received correcting information and the image information in a mass memory, such as a hard disk, and a printing interface  509  for printing the corrected image information received by a printer. The peripheral device  500  may also comprise a keyboard  506  for feeding commands into the peripheral device, a monitor  503  for displaying the image information in visual form and at least one application  505  e.g. for performing an image improvement operation on the received image information on the basis of the image correcting information that corresponds to the image information and is already stored in the memory  501  of the peripheral device. 
         [0035]    The peripheral device  500  receives the image correcting information of the camera module, which is preferably produced already during the manufacture of the camera module or an electronic device, such as a mobile imaging phone, into which the camera module is integrated. At the same time the peripheral device  500  also receives identifying information related to said camera module, electronic device or both. The identifying information can also be a serial number or another similar identifying code. 
         [0036]    The identifying information and image correcting information received are stored in the memory  501  of the peripheral device and linked with each other. When the peripheral device receives an image produced by the camera module, it also receives identifying information, which is preferably related to the camera module, for example. The peripheral device compares the identifying information it has received with the identifying information stored in the memory  501 , and if the identifying information received is found in the memory  501 , the peripheral device performs an image improvement operation on the image it has received based on the image correcting information to which said identifying information received and stored in the memory  501  relates. 
         [0037]    The implementation and embodiments of the invention were described by means of examples above. It is obvious to a person skilled in the art that the invention is not limited to the details of the embodiments described above and that the invention can be implemented otherwise without deviating from the characteristics of the invention. The embodiments shown should be regarded as illustrative only, i.e. the embodiments and applications of the invention are limited only by the appended claims. Consequently, different optional embodiments of the invention defined in the claims, including equivalent embodiments, fall within the scope of the invention.