Abstract:
Concerning increasingly downsized electronic devices equipped with cameras, an object of the present invention is to achieve easy adaptability of parts. A camera module includes an image sensor and a flash memory, and a main module includes an image processing unit and an SDRAM, and the two modules are connected through a flexible cable. The flash memory stores an image processing program for controlling the image processing unit. The image processing program is a program adapted for the camera module. The flash memory also stores adjustment data that is peculiar to the camera module. When the camera function is turned on, the program is downloaded to the main module and image processing is performed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electronic device having a camera function in addition to its original functions.  
         [0003]     2. Description of the Background Art  
         [0004]     The size and cost reductions of image processing circuits and image sensors such as CCDs are promoting the production of electronic devices that are equipped with camera functions in addition to their original functions. For example, such electronic devices include mobile phone devices equipped with cameras and personal digital assistants (PDAs) equipped with cameras.  
         [0005]     However, the camera function is a function that is not originally intended for the mobile phone devices and personal digital assistants. Accordingly, in general, camera modules for realizing the camera function are produced not in the factories that manufacture the electronic devices but in other factories, and the electronic device manufacturers acquire the produced camera modules and assemble the electronic devices. That is, since the camera modules include parts like lenses and image sensors for realizing the photographing function, it is natural that these parts should be adjusted and assembled in factories specialized in these techniques so that mobile phone factories, for example, can concentrate on works for enhancing the quality of mobile phones&#39; original functions.  
         [0006]     Thus, in the manufacture of electronic devices having an additional camera function, the main modules for realizing original functions of the electronic devices and the camera modules for realizing the additional camera function are produced as separate parts as independently as possible, and are assembled together in the final stage.  
         [0007]     Now, the size of mobile phone devices and personal digital assistants is decreasing. This requires higher degrees of integration of parts in the main modules and camera modules in order to add the camera function while promoting the size reduction of the electronic devices.  
         [0008]      FIG. 4  is a block diagram of an electronic device with a camera according to a background art. This electronic device includes a camera module  5  and a main module  6 . The camera module  5  includes a camera board  50  and parts mounted on the camera board  50 , and the main module  6  includes a main board  60  and parts mounted on the main board  60 .  
         [0009]     The camera module  5  includes a lens  51  for leading images of subjects, an image sensor  52  for converting into an image signal the subjects&#39; images led through the lens  51 , an EPROM  53  for storing adjustment data for the camera module  5 , and an A/D converter circuit  54  for digital-converting the image signal outputted from the image sensor  52 .  
         [0010]     The main module  6  includes an image processing unit  61  for applying image processing to the image signal provided from the camera module  5 , an SDRAM  62  used as a work area for the execution of a program for controlling the image processing unit  61 , a main processing unit  63  for executing original functions of the electronic device, and a flash memory  64  for storing the program for controlling the image processing unit  61 .  
         [0011]     Thus, the electronic device with a camera shown in  FIG. 4  includes separated parts, where the camera module  5  is produced in a camera manufacturing factory and the main module  6  is produced in an electronic device manufacturing factory, and the parts are assembled together in the final stage. In this structure, the program stored in the flash memory  64 , i.e., the program for controlling the image processing unit  61 , is adapted for the camera module  5 . That is, it is necessary to prepare different programs for different types of camera modules  5 . Accordingly, when the structure of the camera module  5  is changed, e.g., when the image sensor  52  is changed to another model, it is then necessary to rewrite the program stored in the flash memory  64 . Thus, a change of the camera module  5  requires a change of the main module  6 , which results in additional manufacturing process and increased manufacturing costs. This problem is particularly serious when a large number of main modules  6  are in stock.  
         [0012]     In order to solve this problem, an electronic device with a camera may be configured as shown in  FIG. 5 . This electronic device can be divided into a camera module  5 A and a main module  6 A. This electronic device differs from that shown in  FIG. 4  in that the camera module  5 A includes an image processing unit  55 , an SDRAM  56 , and a flash memory  57 . That is, while the electronic device shown in  FIG. 4  incorporates the image processing unit, SDRAM, and flash memory in the main module, the electronic device of  FIG. 5  incorporates these components in the camera module  5 A.  
         [0013]     The flash memory  57  stores a program for controlling the image processing unit  55 . Also, the flash memory  57  stores adjustment data for the camera module  5 A. In this configuration, because the programs that must be changed according to a change of the camera module  5  are stored in the flash memory  57 , the parts related to the camera function can all be separated from the main module  6 A, which is advantageous in that a change of the camera module  5 A does not affect the main module  6 A.  
         [0014]     However, as mentioned above, because of the downsizing of the electronic device to which the camera function is added, the configuration shown in  FIG. 5  requires a higher degree of integration of a large number of parts in the small camera module  5 A. This leads to the problem that the image sensor  52  suffers from increased noise because of a temperature rise. When a large number of electronic parts are mounted in the camera module  5 A and these electronic parts operate to raise the temperature of the camera module  5 A, then the amount of generated charge in the charge accumulation part of the image sensor  52  increases to produce increased noise, which deteriorates the quality of the output image signal. Particularly, the provision of a relatively high-power consuming part, such as the image processing unit  55 , considerably increases the temperature and more seriously affects the image sensor  52 .  
         [0015]     Also, in the configuration shown in  FIG. 5 , the image signal processed in the image processing unit  55  is transferred to the main module  6 A through a YUV interface. This is because the camera module  5 A and the main module  6 A are generally connected through a flexible cable and so it is difficult to connect the modules through a host interface.  
         [0016]     Thus, JPEG image data generated in the image processing unit  55 , for example, is transferred to the main module  6 A through the YUV interface. At this time, if an interrupt for the electronic device&#39;s original operation occurs in the main module  6 A, the data reception may fail because the rate of data transfer through the YUV interface is low. For example, when the electronic device is a mobile phone device and a telephone call is received in the main module  6 A during the transfer of JPEG image data, some data may be properly recieved.  
         [0017]     Also, providing the image processing unit in the camera module involves CPU processing and other hardware processing on the camera module side. Accordingly, the camera module produces more switching noise than that shown in  FIG. 4 , which also adversely affects the image sensor.  
         [0018]     Japanese Patent Application Laid-Open No. 2004-312433 discloses an image processing system having a camera section and a main body separated from each other. However, in this system, the IC for executing the image processing is provided in the camera section, so that, as in the structure shown in  FIG. 5 , the parts in the camera section are highly integrated in the downsized electronic device. Thus, the problem that the temperature rise increases the noise of the image sensor remains unsolved.  
       SUMMARY OF THE INVENTION  
       [0019]     Concerning electronic devices that are increasingly downsized and that are equipped with a camera function, an object of the present invention is to provide a technique for constructing such electronic devices without requiring additional manufacturing process and increased costs for the parts, and without deteriorating image quality.  
         [0020]     According to the present invention, an electronic device includes: a camera module; and a main module including a component for realizing an original function of the electronic device, where the camera module includes: a lens that leads an image of a subject; an image sensor that converts into an image signal the image of the subject led through the lens; and a nonvolatile memory, and the main module includes: an image processing unit that applies image processing to the image signal provided from the camera module; and a volatile memory, and wherein the image processing unit is controlled according to a program that is adapted for the camera module, and the program is stored in the nonvolatile memory; an interface is provided between the camera module and the main module in order to transfer the program; and the program is transferred from the camera module to the main module through the interface and then executed with the volatile memory used as a work area.  
         [0021]     The present invention relates also to a main module that is incorporated in an electronic device equipped with a camera function and that includes a component for realizing an original function of the electronic device.  
         [0022]     According to the present invention, the main module includes an image processing unit, and a program for controlling the image processing unit is stored in the camera module. Therefore, when the camera module is modified or changed, it is not necessary to modify the main module, which makes it possible to use the main module as a common module. Also, since the image processing unit is not disposed in the camera module, the influence of increased noise of the image sensor is alleviated.  
         [0023]     These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a block diagram of a mobile camera phone device according to a preferred embodiment;  
         [0025]      FIG. 2  is a diagram showing the appearance of the camera module and the main module;  
         [0026]      FIG. 3  is a diagram showing another preferred embodiment of the mobile camera phone device;  
         [0027]      FIG. 4  is a block diagram of an electronic device equipped with a camera according to a background art; and  
         [0028]      FIG. 5  is a block diagram of an electronic device equipped with a camera according to a background art.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     Preferred embodiments of the present invention will now be described referring to the drawings. The preferred embodiments will describe examples in which the inventive electronic device equipped with a camera is applied to a mobile camera phone device  4 .  
         [0030]     As shown in  FIG. 1 , the mobile camera phone device  4  includes a camera module  1  and a main module  2 . The camera module  1  includes a camera board  10  and various parts mounted on the camera board  10 . The main module  2  includes a main board  20  and various parts mounted on the main board  20 . As shown in  FIG. 2 , the camera module  1  and the main module  2  are connected through a flexible cable  3 . The camera module  1  and the main module  2  thus connected are accommodated in the housing of the mobile phone device to form the mobile camera phone device  4 .  
         [0031]     Referring to  FIG. 1  again, the camera module  1  includes a lens  11  that leads images of subjects, an image sensor  12  that converts into an image signal the images of subjects led by the lens  11 , and a flash memory  13 . The image sensor  12  is a CCD sensor or a CMOS sensor, for example. The image sensor  12  includes analog signal processing circuits such as a CDS (Correlated Double Sampling) circuit and an AGC (Automatic Gain Control) circuit, and an A/D converter circuit, and the image sensor  12  converts an analog-processed image signal into a digital signal and outputs it. The flash memory  13  contains an image processing program  40  and adjustment data  41 .  
         [0032]     While this preferred embodiment uses a flash memory (flash ROM) having a serial interface in order to store the image processing program  40  etc., any rewritable nonvolatile memory may be used. For example, other EEPROM or EPROM may be used. Also, a flash memory having a parallel interface may be used.  
         [0033]     The main module  2  includes an image processing unit  21  that applies image processing to the image signal provided from the camera module  1 , an SDRAM  22  that is used as a work area for the execution of the image processing program  40  for controlling the image processing unit  21 , and a main processing unit  23  that controls the entirety of the mobile camera phone device  4 . While an SDRAM is used as the program executing area, other volatile memory may be used.  
         [0034]     The image processing unit  21  is configured as an LSI having a CPU for executing the image processing program  40  and hardware circuitry for performing various image processings. The hardware circuitry for performing various image processings includes a color space converter circuit, a pixel interpolation circuit, a shading correction circuit, and the like. The main processing unit  23  is configured as an LSI having a CPU for controlling the entirety of the mobile camera phone device  4  and hardware circuitry for performing various processings.  
         [0035]     The image processing unit  21 , the main processing unit  23 , and the SDRAM  22  are mounted on the main board  20  and connected through signal lines. As shown in the diagram, the image processing unit  21  and the main processing unit  23  are connected through a YUV interface and a host interface.  
         [0036]     The main module  2  further includes various other parts. For example, the main module  2  includes parts for performing the original function of the mobile camera phone device  4 , i.e., telephoning function, and parts for processing the communication. The main module  2  is connected to various parts including operating buttons, a microphone, speaker, LCD, etc. Thus, the main module  2  includes various kinds of parts that realize original functions as a mobile phone device.  
         [0037]     Operations of the mobile camera phone device  4  thus structured will be described. When the mobile camera phone device  4  is performing its original function as a mobile phone device, e.g., when the mobile camera phone device  4  is processing a call, no power is supplied to the camera module  1 , the image processing unit  21 , and the SDRAM  22 . Then, when the user operates the mobile camera phone device  4  to turn on the camera function, power is supplied to the camera module  1 , the image processing unit  21 , and the SDRAM  22 .  
         [0038]     When power is thus supplied to the parts related to the camera function, a download circuit  211  included in the image processing unit  21  starts downloading of the image processing program  40 . The image processing program  40  is a program that controls the image processing unit  21  and is adapted for the camera module  1 . That is, it is necessary to prepare the image processing program  40  in correspondence with the structure of the camera module  1  or the model of the image sensor  12 . In this preferred embodiment, the image processing program  40  is stored in the flash memory  13  that is provided in the camera module  1 .  
         [0039]     As shown in  FIG. 1 , the flexible cable  3 , connecting the camera module  1  and the main module  2 , includes a parallel signal line  31  for transferring the image signal outputted from the image sensor  12  and a serial signal line  32  for transferring the image processing program  40  stored in the flash memory  13 . The signal line  31 , for transferring the image signal, is a 10-bit-wide or 12-bit-wide signal line, for example. When the download circuit  211  transfers a download command through the serial signal line  32 , the image processing program  40  is transferred to the main module  2  through the serial signal line  32  and stored in the SDRAM  22 . In this way, the camera module  1  and the main module  2  of this preferred embodiment have a dedicated interface for the transfer of the program. The flash memory  13  may be formed of a memory having a parallel interface, with a program downloading interface formed of a parallel interface.  
         [0040]     Then, the CPU in the image processing unit  21  executes the image processing program  40  while using the SDRAM  22  as a work area. In this way, the image signal outputted from the camera module  1  is transferred to the image processing unit  21  through the signal line  31 , and the image processing unit  21  performs various image processings.  
         [0041]     The flash memory  13  further stores the adjustment data  41  peculiar to the camera module  1 . The adjustment data  41  is data that is peculiar to various parts of the camera module  1 . For example, the adjustment data  41  includes defect pixel data about the image sensor  12 , characteristic data about output level caused by variations among individual optical system components such as IIR filters and sensors, R, G, B output level variation characteristic data obtained when a reference light source is used, optical shading characteristic data about the lens, and the like.  
         [0042]     When the camera function is turned on, the download circuit  211  downloads the adjustment data  41  through the signal line  32  and stores the adjustment data  41  in the SDRAM  22 . Then, the image processing unit  21  performs image processing according to the adjustment data  41  or by using the adjustment data  41  as parameters. For example, defect pixel correction processing is performed on the basis of the defect pixel data. Also, shading correction processing is performed on the basis of the optical shading characteristic data. Thus, the image processing program  40 , adapted for the camera module  1 , is executed while considering information peculiar to the camera module  1 .  
         [0043]     The mobile camera phone device  4  according to this preferred embodiment is configured as described so far, and offers the effects shown below. Firstly, the image processing program  40  adapted for the camera module  1  is stored within the camera module  1 . Accordingly, even when the structure of the camera module  1  is changed and the contents of the image processing program  40  must be changed accordingly, the change requires only changing the camera module  1 . That is, it is not necessary to change the main module  2  when the structure of the camera module  1  is changed. This allows the main module  2  to be used as a common module, regardless of the model of the camera module  1 . The use of the main module  2  as a common module reduces the risk of overstocking when the main module  2  is mass-produced, which will allow reduction of costs. The first effect solves the problem of the structure according to the background art described referring to  FIG. 4 . Also, this allows the omission of the EPROM that is used in the configuration of  FIG. 4 , which is advantageous in both of the cost reduction and size reduction of the device.  
         [0044]     Secondly, the number of parts of the camera module  1  is reduced since it does not include the image processing unit. Particularly, the absence of the image processing unit, whose CPU processing causes temperature rise, alleviates the influence of increased noise of the image sensor  12 , thus enhancing the quality of the outputted image signal. The second effect solves the problem of the configuration according to the background art described referring to  FIG. 5 . Thus, in the mobile camera phone device  4  of this preferred embodiment, the parts mounted in the camera module  1  and the main module  2  are arranged in a well-balanced manner, without excessive concentration in either module, and the problems of both of the electronic devices according to the background art shown in  FIGS. 4 and 5  are solved.  
         [0045]     Also, in this preferred embodiment, the adjustment data  41  for the camera module  1  is stored in the flash memory  13  of the camera module  1 . Accordingly, adjustments of parts mounted in the camera module  1  are performed during the manufacturing process of the camera module  1 , and the results of adjustments are stored in the camera module  1  itself, so that the manufacturing process can be independently completed just with the camera module  1 .  
         [0046]     Furthermore, this preferred embodiment has the advantage that, because the image processing unit  21  is provided in the main module  2 , data can be transferred through the host interface to and from the main processing unit  23  that controls the entire mobile camera phone device  4 . More specifically, mounting the image processing unit  21  and the main processing unit  23  on the same main board  20  allows the units to be readily connected through the host interface.  
         [0047]     It is thus possible to transfer data, e.g., JPEG image data generated in the image processing unit  21 , to the main processing unit  23  through the host interface. Even when an interrupt like arrival of a phone call occurs in the main processing unit  23  during an operation of the camera function, the data transfer is certainly carried out without loss of data. It is also possible to transfer an image, inputted from the camera module  1 , to the main processing unit  23  through the YUV interface and cause the main processing unit  23  to make a display of moving picture on the LCD, in parallel with a JPEG image data transfer through the host interface.  
         [0048]     Mounting the image processing unit  21  in the main module  2  produces another effect. In most cases, display control to the LCD of the mobile camera phone device  4  is performed on the main processing unit  23  side, and the main processing unit  23  has a display controller for the LCD. Accordingly, in the mobile camera phone device  4  according to this preferred embodiment, a display controller is added also to the image processing unit  21 . Then, a selector is connected to the two display controllers so that one of the signals is outputted to the LCD. That is, this configuration is made possible by the provision of the image processing unit  21  and the main processing unit  23  on the same board  20 . When the selector is connected to the display controller provided for the image processing unit  21 , images transferred from the camera module  1  can be displayed directly on the LCD without being controlled by the main processing unit  23 . This configuration makes it possible to make a live view display on the LCD without applying loads on the main processing unit  23 .  
         [0049]      FIG. 3  is a diagram showing another preferred embodiment of the present invention. While the image sensor  12  of the preferred embodiment of  FIG. 1  contains an A/D converter circuit, the image sensor  12 A of this preferred embodiment does not contain an A/D converter circuit. Accordingly, the camera module  1 A includes an A/D converter circuit  14  separately from the image sensor  12 A. In other respects, the configuration is the same as that shown in  FIG. 1 .  
         [0050]     While the preferred embodiments of the present invention have described a mobile phone device equipped with a camera as an example, the present invention offers the corresponding effects also when applied to other electronic devices having a camera function in addition to their original functions, such as personal digital assistants equipped with cameras. The effects are more significant especially with electronic devices whose downsizing is in growing demand.  
         [0051]     While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention.