Patent Publication Number: US-7221393-B2

Title: Color imaging device and method

Description:
This application is a continuation of U.S. patent application Ser. No. 08/823,160 filed Mar. 25, 1997 now U.S. Pat. No. 6,421,083. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a color imaging device and method for adjusting color balance of an imaged still picture. 
   2. Description of the Related Art 
   In a camera device, pre-set color reproducibility is achieved by effecting white balance adjustment and black balance adjustment, even though the color temperature of an object differs from one light source to another. 
   In effecting white balance adjustment, a white object is imaged, and level adjustment is performed so that the signal levels of color signals in the white luminance point will be equal to one another. In effecting black balance adjustment, the black level of imaging signals is sampled by closing a lens shutter once, and adjusting the signal level so that the black levels of the respective color signals will be equal to one another. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a color imaging device and a color imaging method whereby it is possible to effect color balance in a grey area intermediate between the black and white which has not been possible with conventional white balance adjustment. 
   It is another object of the present invention to provide a color imaging device and a color imaging method whereby it is possible to perform color balance adjustment in all grey areas including the black and white. 
   In one aspect, the present invention provides a color imaging apparatus including imaging means for imaging an object for generating a color imaging signal made up of a plurality of color signals, level balance control data generating means for generating level balance control data based on the relative relation between signal levels of the color signals, light exposure volume adjustment means for adjusting the light exposure volume of the imaging means, memory means for storing, in each light exposure volume adjusted by the light exposure adjustment means, the level balance control data generated by the level balance control data generating means, in association with signal levels of the color signals in each light exposure volume, and level balance control means for reading out the level balance control data associated with the color signals from the storage means, based on the signal level of each of the color signals, for controlling the signal level of each color signal. This enables color balance adjustment in a entire grey area between black and white which has not been possible to perform in conventional white balance adjustment. 
   In another aspect, the present invention provides a color imaging apparatus including imaging means for imaging an object for generating a color imaging signal made up of a plurality of color signals, pre-set area extraction means for sequentially extracting color imaging signals of portions representing images in a plurality of pre-set areas in a picture represented by the color imaging signals, level balance control data generating means for generating level balance control data based on the relative relation between signal levels of the color signals contained in the pre-set areas, storage means for storing the level balance control data in association with the relative relation of the signal levels of the color signals contained in the preset areas, and level balance control means for reading out the level balance control data from the storage means in association with the color signals based on the signal levels of the color signals for controlling the signal levels of the color signals. This enables automatic color balance adjustment in a entire grey area between black and white. 
   In still another aspect, the present invention provides a color imaging apparatus including imaging means for imaging an object for generating color imaging signals made up of a plurality of color signals, display means for displaying an image based on the color imaging signals, area designation means for designating a desired area in the image displayed by the display means, level balance control data generating means for generating level balance control data based on the relative relation between signal levels of the color signals constituting the color imaging signals corresponding to the area designated by the area designating means, storage means for storing the level balance control data in association with the signal levels of the color signals in the area designated by the area designating means, and level balance control means for reading out the level balance control data associated with respective color signals from the storage means based on the signal levels of the color signals for controlling the signal levels of the color signals. This enables color balance adjustment in a entire grey area between black and white by a simplified operation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic block diagram showing the configuration of an imaging system embodying the present invention. 
       FIG. 2  is a block diagram showing an illustrative structure of a color imaging device in the imaging system of  FIG. 1 . 
       FIG. 3  is a schematic block diagram showing an illustrative configuration of a digital processor of the color imaging device shown in  FIG. 2 . 
       FIG. 4  is a block diagram showing the configuration of a LUT provided in the digital processor of  FIG. 3 . 
       FIG. 5  is a flowchart showing the method for adjusting the color balance in the imaging system of  FIG. 2 . 
       FIG. 6  illustrates the display contents of a display of an information processing apparatus in the imaging system of  FIG. 2 . 
       FIG. 7  illustrates the display contents of a display of the information processing apparatus shown in  FIG. 6 . 
       FIG. 8  is a flowchart showing the sequence of automatic adjustment of color balance in the imaging system of  FIG. 2 . 
       FIG. 9  is a flowchart showing the sequence of automatic adjustment of color balance in the imaging system of  FIG. 2 . 
       FIG. 10  illustrates the display contents of the display of the information processing apparatus shown in  FIG. 6 . 
       FIG. 11  similarly illustrates the display contents of the display of the information processing apparatus shown in  FIG. 6 . 
       FIG. 12  is a graph showing characteristics of the usual LUT in the imaging system of  FIG. 2 . 
       FIG. 13  is a graph showing characteristics of the LUT with negative-positive inversion in the imaging system of  FIG. 2 . 
       FIG. 14  is a flowchart showing another method for adjustment of the color balance in the imaging system of  FIG. 2 . 
       FIG. 15  is a flowchart for illustrating the sequence of formulating color balance correction data. 
       FIG. 16  is a flowchart for illustrating the sequence of white luminance level setting. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the drawings, preferred embodiments of the present invention will be explained in detail. The present imaging system has the function of performing fine adjustment in white balance adjustment (grey balance adjustment) at the time of fine gamma adjustment for color imaging signals of red (R), green (G) and blue (B) obtained on imaging an object by a color imaging device  1  for effecting level balance adjustment for color signals for all intermediate colors from white to black. 
   The color imaging device  1  of the present imaging system includes a camera head  3  for imaging an object via an imaging lens  2  for outputting imaging signals, and a digital processor  4  for converting the color imaging signals from the camera head  3 , storing the converted imaging data, supplying the stored picture data to an information processing device  5  and for effecting color signal level balance adjustment for the stored imaging data. 
   The imaging system also includes an information processing device  5  for controlling data processing by the digital processor  4 , a printer  6  for outputting an image of the object based on the imaging data transmitted from the color imaging device  1 . The imaging system further includes a personal computer  7  for performing a control similar to that performed by the information processing device  5  and a monitoring device  8  for displaying an image of the object imaged by the camera head  3 . 
   The imaging system also includes a remote controller  9  for performing flash synchronized imaging, and a liquid crystal display (LCD) view finder  10  for displaying the image of the object imaged by the camera head  3 . The imaging system also includes a strobo generator  11  and a strobo light emitting device  12  which emits flash light if, in case of necessity, a release button  9 A of the remote controller  9  is pressed. 
   Specifically, the camera head  3  includes a charge coupled device (CCD) image sensor  21 , a correlated double sampling (CDS) circuit  22 , a pre-amplifier  23 , a gain control circuit  24 , a white balance circuit  25 , a pre-knee circuit  26 , a gamma correction circuit  27  and an output driver  28 , as shown for example in  FIG. 2 . 
   The CCD image sensor  21  is of a progressive scan type three CCD plate system designed for reading out color imaging signals of red (R), green (G) and blue (B) responsive to three prime color components separated by a color separation prism  37  from the imaging light incident thereon from the imaging lens  2  via an optical low-pass filter  36 . 
   The CDS circuit  22  performs correlated double sampling on the color imaging signals R, G and B read out from the CCD image sensor  21  to send color imaging signals R, G and B, reduced in random noise, to the pre-amplifier circuit  23 . 
   Each of the color imaging signals of R, G and B, amplified by the pre-amplifier circuit  23 , has its gain controlled by the gain control circuit  24  controlled by the CPU  30 . The gain-controlled color imaging signals are routed to the white balance circuit  25 . 
   The white balance circuit  25  performs white clip on the color imaging signals, if need be, and routes the processed color imaging signals R, G and B to the pre-knee circuit  26 . 
   The pre-knee circuit  26  compresses the signal level of the color imaging signals R, G and B higher than a pre-set knee level and routes the compressed signals to the gamma correction circuit  27 . This gamma correction circuit  27  performs signal level conversion based on, for example, a 0.45 γ non-linear curve in order to route the color imaging signals R, G and B via output driver  28  and terminals  29 R,  29 G and  29 B to the digital processor  4 . 
   The camera head  3  includes a micro-computer (CPU)  30  for controlling the gain control circuit  24 , white balance circuit  25 , pre-knee circuit  26  and the gamma correction circuit  27 , an electrically erasable programmable ROM (EEPROM)  31  for holding in memory a control program for the CPU  30 , and a sync generator  33  for generating synchronization signals. The camera head  3  also includes a timing generator  34  for generating CCD readout pulses based on the synchronization signals from the sync generator  33  and a CCD driver  35  for amplifying CCD readout pulses from the timing generator  34 . 
   The CPU  30  controls gamma correction, generation of synchronization signals by the sync generator  33  or the diaphragm of the imaging lens  2  based on the control signals supplied from the digital processor  4  via terminal  32  and the control program stored in the EEPROM  31 . 
   The sync generator  33  generates vertical and horizontal synchronization signals and routes these synchronization signals to the timing generator  34 . The timing generator  34  generates CCD readout pulses, vertical transfer pulses and horizontal transfer pulses based on these synchronization signals. The CCD driver  35  drives the CCD image sensor  21  by these CCD readout pulses. The CCD image sensor  21  thus outputs color imaging signals R, G and B at a rate of 24 frames per second. 
   Referring to  FIG. 3 , the digital processor  4  includes amplifiers  42 R,  42 G and  42 B for amplifying the color imaging signals R, G and B supplied from the camera head  3  and cable compensators  43 R,  43 G and  43 B for compensating the cable length for the color imaging signals from the amplifiers  42 R,  42 G and  42 B. The digital processor  4  also includes analog/digital (A/D) converters  44 R,  44 G and  44 B for converting the color imaging signals R G and B from the cable compensators  43 R,  43 G and  43 B and lookup tables (LUTs)  45 R,  45 G and  45 B for converting the gradation of the color imaging data from the A/D converters  44 R,  44 G and  44 B. 
   The cable compensators  42 R,  42 G and  42 B are fed with color imaging signals R, G and B from the camera head  3  via terminals  41 R,  41 G and  41 B and amplify these color imaging signals R, G and B to supply the amplified signals to the cable compensators  43 R,  43 G and  43 B. 
   The cable compensators  43 R,  43 G and  43 B compensate for deterioration in frequency characteristics responsive to the cable length for the amplified color imaging signals and route the respective produced color imaging signals to the A/D converters  44 R,  44 G and  44 B. 
   The A/D converters  44 R,  44 G and  44 B convert the color imaging signals into color imaging data composed of 10-bit samples, using sampling clocks, not shown, based on the synchronization signals from the camera head  3 , and route the color imaging data to the LUTs  45 R,  45 G and  45 B. 
   The LUTs  45 R,  45 G and  45 B store level conversion data as table data in order to perform grey balance correction of color imaging data gamma-corrected by the gamma correction circuit  27 . The LUTs  45 R,  45 G and  45 B are made up of level detectors  451 R,  451 G and  451 B fed with 10-bit color imaging data from the A/D converters  44 R,  44 G and  44 B and table memories  452 R,  452 G and  452 B, from which table data are read, using the detection outputs by the level detectors  451 R,  451 G and  451 B as readout addresses, as shown in  FIG. 4 . As the table memories  452 R,  452 G and  452 B, a 512K 8 bit static random access memory (SRAM) is used for each of the table memories  452 R,  452 G and  452 B. In this SRAM is stored, as table data, 8-bit level conversion data supplied from a random access memory (RAM)  67  via a buffer memory  65 . 
   The LUTs  45 R,  45 G and  45 B convert the 10-bit color imaging data supplied from the A/D converters  44 R,  44 G and  44 B into 8-bit color imaging data which are supplied to a write control circuit  46  and a dynamic random access memory (DRAM) controller  55 . 
   The digital processor  4  includes a write control circuit  46  for controlling the writing of the color imaging data R, G and B from the LUTs  45 R,  45 G and  45 B and a video random access memory (RAM)  47  for storing the color imaging data under control by the write control circuit  46 . The digital processor  4  also includes a readout control circuit  48  for controlling readout of the color imaging data read out from the VRAM  47  and LUTs  49 R,  49 G and  49 B for converting the gradation of the color imaging data read out from the readout control circuit  48 . The digital processor  4  further includes converters  51 R,  51 G and  51 B for converting the color imaging data R, G and B from the LUTs  49 R,  49 G and  49 B into color imaging signals  51 R,  51 G and  51 B, low-pass filters (LPFs)  52 R,  52 G and  52 B for allowing passage only of color imaging signals of a specified band, and a matrix encoder  53 . 
   The write control circuit  46  transmits readout clocks of 30 MHZ to the VRAM  47 , while reading out color imaging data R, G and B at a rate of 30 frames per second in synchronism with the readout clocks for supplying the color imaging data to the LUTs  49 R,  49 G and  49 B. The readout control circuit  48  routes the 30 MHZ write clocks to the VRAM  47 , while reading out the color imaging data from the VRAM  47  at a rate of 30 frames per second in synchronism with the readout clocks for supplying the color imaging data R, G and B to the LUTs  49 R,  49 G and  49 B. 
   The LUTs  49 R,  49 G and  49 B are each made up of a 512K 8 bit SRAM for storing LUT data supplied from the RAM  67  via buffer memory  66 . Specifically, the LUTs  49 R,  49 G and  49 B hold in memory as table data such characteristic data in which color regeneration of the monitoring device  8  and gradation regeneration (picture quality) will be equal to the picture quality displayed on a CRT of a display of the information processing device  5  or with the picture quality of the picture printed out by the printer  6 , and perform level correction of color imaging data by these characteristic data. The LUTs  49 R,  49 G and  49 B convert the gradation of the color imaging data R, G and B independently of one another in order to route the resulting color imaging data to the D/A converters  51 R,  51 G and  51 B, respectively. 
   The D/A converters  51 R,  51 G and  51 B convert the color imaging data, made up of 8-bit samples, into color imaging signals R, G and B which are then supplied to the LPFs  52 R,  52 G and  52 B, respectively. In the upstream stage of the D/A converters  51 R,  51 G and  51 B are provided adders  50 R,  50 G and  50 B supplied with menu data read out from the ROM  68  in which is pre-stored a program designed to control the overall system. 
   The LPFs  52 R,  52 G and  52 B allow for passage only of a pre-set band of the color imaging signals R, G and B to eliminate unneeded band components and routes the resulting color imaging signals to the matrix encoder  53 . 
   The matrix encoder  53  converts the color imaging signals R, G and B into, for example, luminance signals Y and chroma signals C and processes these signals Y and C into composite color video signals of, for example, the NTSC system, in order to supply the color signals via terminal  54  to the monitor device  8 . The matrix encoder  53  can also output the color imaging signals R, G and B directly. This enables an image corresponding to the signals from the color imaging device to be displayed on the monitor device  8 . 
   The digital processor  4  includes a frame memory  56 , a frame memory  57 , as a spare for this frame memory, and a DRAM controller  55  for writing color imaging data on the frame memories  56 ,  57  for reading out color imaging data from the frame memories  56 ,  57 . 
   The frame memory  58  includes a DRAM  56 R for storing the color imaging data R in memory, a DRAM  56 G for storing the color imaging data G in memory and a DRAM  56 B for storing the color imaging data B in memory. Each of the DRAMs  56 R,  56 G and  56 B can store in memory color imaging data of, for example, 1280×960 pixels. The color imaging data R, G and B from the DRAMs  56 R,  56 G and  56 B are read out from or written in the frame memory  56  under control by the DRAM controller  55 . 
   The DRAM controller  55  is configured for writing the color imaging data R, G and B from the LUTs  45 R,  45 G and  45 B in the frame memory  56 , or for reading stored color imaging data from the frame memory  56 . The DRAM controller  55  is configured for selecting the color imaging data stored in the frame memory  56  by reading out 640×480 pixels of color imaging data. 
   The frame memory  57  is configured similarly to the frame memory  56  and is provided as a spare for the frame memory  56 . 
   The digital processor  4  includes an averaging circuit  58  for removing redundant high frequency range of the color imaging data from the DRAM controller  55 , and an interpolation circuit  59  for interpolating the color imaging data from the DRAM controller  55  for outputting luminance data Y. The digital processor  4  also includes a picture quality adjustment and contrast adjustment circuit  60  for increasing the acuteness of picture quality of the luminance data Y from the interpolation circuit  59  and for adjusting the contrast, and a matrix circuit  61 . The digital processor  4  further includes a masking circuit  62  for broadening the frequency width of respective color imaging data from the matrix circuit  61  and a SCSI (small computer system interface) protocol controller (SPC)  63  operating as an interface for signal transmission/reception over an SCSI bus. 
   The averaging circuit  58  removes unneeded high frequency band components of the color imaging data R, G and B, for preventing aliasing of the high frequency band signal components to the signal components of the low frequency band and routes the color imaging data R, G and B to the matrix circuit  61 . 
   The interpolation circuit  59  interpolates the color imaging data for improving resolution and converts the interpolated color imaging data R, G and B into image data Y, U and V. The interpolation circuit  59  also transmits the luminance data Y to the picture quality adjustment and contrast adjustment circuit  60 , while routing the chroma data U and V to the matrix circuit  61 . 
   The picture quality adjustment and contrast adjustment circuit  60  acquires contour signals by a high-pass filter from, for example, luminance data Y, and removes the noise contained in the contour signals by a core ring. After amplitude adjustment, the circuit  60  sums the resulting signal to the main signal for adjusting the picture quality. The picture quality adjustment and contrast adjustment circuit  60  varies the gain of the luminance data Y and moderately varies the amplitude for contrast adjustment. The contrast-adjusted luminance data Y is fed to the matrix circuit  61 . 
   The matrix circuit  61  can output one of the supplied color imaging data R, G and B and picture data Y, U and V. For example, the matrix circuit  61  outputs the color imaging data R, G and B to the masking circuit  62 . 
   The masking circuit  62  widens the band of the supplied color imaging data R, G and B for increasing the saturation for enhancing flashiness of the colors. In addition, the masking circuit  62  transmits the resulting color imaging data R, G and B via SPC  63  to, for example, the information processing device  5 . 
   The digital processor  4  includes a buffer memory  65  for writing level conversion data in the LUTs  45 R,  45 G and  45 B and a buffer memory  66  for writing level conversion data in the LUTs  49 R,  49 G and  49 B. The digital processor  4  also includes a RAM  67  for storing in memory the data of the LUTs  45  and  49 , a ROM  68  in which a program for controlling the overall system is stored, and a CPU  69  for executing the program written in the ROM  68 . 
   With the above-described imaging system, a picture corresponding to the object is displayed on the monitor device  8 . If the user presses a release button  9 A as he or she views the monitor device  8 , the color imaging data is stored in the frame memory  56 . The color imaging data stored in the frame memory  56  is transferred over an SCSI bus to the information processing device  5  which can perform color balance adjustment thereon. The printer  6  is adapted for printing out a still picture based on the color imaging data. 
   Specifically, with the present imaging system, the user prepares the object at step S 1  and adjusts the focusing or the angle of field as he or she views a moving picture displayed on the viewfinder  10  or on the monitor device  8 , while checking the light stop value. On the other hand, menu data is read out from the ROM  68  in which the program for controlling the overall system is read out and sent to the adders  50 R,  50 G and  50 B, so that the user can actuate a button of the remote controller  9  for setting the imaging conditions as he or she views the menu representation, not shown, of the camera sensitivity or the light exposure system. 
   With the present imaging system, the user presses at step S 2  the release button  9 A of the remote controller  9  for supplying a release signal to the CPU  30  of the camera head  3  for imaging an object. The imaging signals produced by the camera head  3  are fed to the digital processor  4  which then writes the color imaging signal converted by the digital processor  4  into digital signals via DRAM controller  55  in the frame memory  56 . 
   In the next step S 3 , the color imaging data written in the frame memory  56  are read out and imaging signals are supplied to the monitor device  8  from the matrix encoder  53  via terminal  54 . The user views an image displayed on the monitor device  8  and transfers the image to the information processing device  5 . 
   At the next step S 4 , the user clicks a ‘transfer’ button  9 C on the remote controller  8  or a ‘transfer’ button  75  on a display screen of the information processing device  5 . This routes the transfer command signal to the CPU  30  of the camera head  3 . The transfer command signal is sent via terminal  32  to the CPU  69  of the digital processor  4 . Under control by the CPU  69 , the DRAM controller  55  selects and reads out color imaging data stored in the frame memory  56 . For example, 1280×960 pixel color imaging data have been written in the DRAMs  56 R,  56 G and  56 B of the frame memory  56 . These color imaging data R, G and B are selected by the DRAM controller  555  reading out 640×960 pixel color imaging data. The read-out color imaging data R, G and B are directly outputted by the matrix circuit  61  so as to be transferred via masking circuit  62  and SPC  63  to the information processing device  5 . 
   When the color imaging data R, G and B have been transferred from the digital processor  4  to the information processing device  5 , the device  5  is in a stand-by state in readiness for auto/manual selection setting, with the picture derived from these color imaging data R, G and B being displayed on the display  5 A. 
   That is, the present imaging system is configured for adjusting color balance of the color imaging data R, G and B based on the color balance adjustment control from the information processing device  5 . 
   The color balance adjustment by the information processing device  5  is classified into standard object correction of doing color balance adjustment at an optional intermediate level from black to white, and general object correction of doing color balance adjustment at an optional point of an image being formed. 
   In the case of the standard object correction, a grey scale is imaged by the camera head  3 . At this time, there are displayed, on the display  5 A of the information processing device  5 , a display portion  71  displaying the grey scale consisting of  11  areas gradually changed from black to white, an iris registration portion  72 , having registered therein pre-set values of iris of the imaging lens  2 , an iris adjustment portion  73 , an iris setting portion  74 , an adjustment data transfer portion  75  for transferring adjustment data to the color imaging device  1  after color balance adjustment, a release portion  76 , a level/memory selection portion  77  for switching between a level image and a stored image, a coordinate display portion  78  for displaying the coordinate of a side of the display portion  71  pointed by a mouse  5 C, a level display portion  79  for displaying level values of the color signals R, G and B, and an auto-manual selection portion  80  for selecting whether color balance adjustment is to be performed automatically or manually, as shown for example in  FIG. 6 . 
   In the case of general object correction, a selected object image is displayed on the display portion  71 , as shown for example in  FIG. 7 . Switching between the standard object correction and the general object correction may be achieved using, for example, the remote controller  9 . 
   The user can designate a point of a picture displayed on the display portion  71  of the display  5 A using, for example, the mouse  5 C, as shown for example in  FIG. 6 . 
   In the standard object correction, if the user clicks an optional point of the display portion  71  to designate the grey level for grey balance adjustment, the information processing device  5  can display respective signal levels of the color imaging signals R, G and B at the designated positions on the level display portion in terms of values from 0h to FFh. 
   Similarly, in the general object correction, if the user clicks an optional point of the display portion  71  to designate the grey level for grey balance adjustment, the information processing device  5  can display respective signal levels of the color imaging signals R, G and B at the designated positions on the level display portion in terms of values from 0h to FFh. 
   If the user clicks a mark in the iris registration portion  72 , a previously registered iris value is displayed. If the user re-clicks a desired one of the registered iris values, the information processing device  5  transmits data of the clicked iris values to the CPU  30  of the camera head  3  for adjusting the iris of the imaging lens  2 . The user may similarly drag a short crossbar of the iris adjustment portion  73  towards the left or right for performing iris adjustment. 
   Referring to the flowchart of  FIG. 8 , if, in the above-mentioned stand-by state, the user clicks the auto/manual selection portion  80  at step S 11 , the information processing device  5  proceeds to step S 12  in order to judge whether or not auto has been selected. 
   If auto is selected, the information processing device  5  transfers to step S 13  for doing automatic grey balance adjustment. Conversely, if manual is selected, the information processing device  5  transfers to step S 14  to await designation of the correction point. 
   The processing for automatic grey balance adjustment at step S 13  takes place in case of imaging a standard object which gives the grey scale comprised of  11  areas exhibiting gradual transition from black to white, as displayed on the display portion  71  shown in  FIG. 6 . Specifically, the processing occurs in accordance with the flowchart shown in  FIG. 9 . 
   The black area and the white area in the grey scale are denoted by area numbers A=1 and A=11, with the intermediate grey areas being denoted as A=2 to 10. 
   At the first step S 21 , an area number is initialized (A=1) and, at the second step S 22 , G-R and G-B are calculated, based on the color imaging data R, G and B of an area denoted by area number A. At the next step S 23 , correction data is found, based on the results of the calculations. The correction data is stored in association with the area number A. Such association with the area number A is equivalent to association with the signal level values of the color imaging signals R, G and B. 
   At the next step S 24 , it is judged whether or not the area number is equal to ‘11’. If A≠11, the information processing device  5  transfers to step S 25  to increment the area number A (A=A+1). The information processing device  5  then reverts to step S 22  to process the next area. The correction data is sequentially found for each of areas of the grey scale. If it is found at step S 24  that A=11, the information processing device  5  reverts to step S 26  to generate LUT table data. The information processing device  5  then transfers to step S 16  in the flowchart of  FIG. 8 . 
   At step S 26 , the information processing device  5  sends a command for re-writing the LUT table data via SPC  63  to the CPU  69  of the digital processor  4 . If fed with the above-mentioned table data via SPC  63  from the information processing device  5 , the CPU  69  of the digital processor  4  routes the table data via buffer memory  65  to the LUTs  45 R,  45 G and  45 B. The data in the table memories  452 R,  452 G and  452 B in the LUTs  45 R,  45 G and  45 B are re-written, based on the data supplied from the buffer memory  65 , to implement optimum color balance adjustment. 
   If decision at step S 12  is for ‘manual’, the information processing device  5  awaits instructions at step S 14  as to the correction point and is actuated on user actuation. 
   At steps S 14  and S 15 , grey balance is adjusted based on an image displayed on the display unit  71  shown in  FIG. 7 . First, at step S 14 , the user designates, using the mouse  5 A or the like, an area in the displayed image on the display portion  71  in which to effect grey balance. The information processing device  5  generates color balance correction data based on an image of the designated area. The correction data is sent at step S 16  from the information processing device  5  to the digital processor  4 . The correction data is stored via buffer memory  65  in the LUTs  45 R,  45 G and  45 B in association with the designated area, that is in association with the signal level of the image in the designated area. 
   Referring to  FIG. 10 , there can be displayed, on the display  5 A of the information processing device  5 , a camera/monitor selection unit  81  for selecting which of the LUT values on the camera or the LUT value on the monitor device  8  should be changed; a table editor portion  82  for displaying LUT data prior to adjustment as a graph; a color signal selection portion  83  for selecting which of the color imaging signals R, G and B should be used for the graph displayed on the table editor portion  82 ; a resetting portion  84  for resetting the data being adjusted for colors by the table editing portion  82 ; a registration portion  85  for registering the color-adjusted correction values; an inversion portion  86  of negative/positive inversion; a user table for displaying the current LUT data (pre-correction LUT data); a call-out portion  88  for calling out the past correction value registered by the user; and a return portion  89  for reversion to the original picture. 
   In this case, the user can drag two black points on the table editing portion  82  using a mouse for performing signal level adjustment of the color imaging data B displayed on the color signal selection portion  83 . Thus the user can obtain color imaging data adjusted to the desired color balance as he or she views the display of the information processing device  5 . 
   If the user clicks the inversion portion  8 , the CPU  69  of the imaging device reverses the characteristics of the LUTs  45 R,  45 G and  45 B and the LUTs  49 R,  49 G and  49 B based on the control signal from the information processing device  5 . That is, the CPU  69  can reverse the usual right upward sloping LUT characteristics shown in  FIG. 12  into right downward sloping LUT characteristics shown in  FIG. 13  for realizing negative-positive converted color imaging data. 
   The user then sets the color imaging data B, for example, to a desired value, and clicks the registration portion  85 . This causes the information processing device  5  to send data of the thus set value to the digital processor  4 . Since the data in the LUTs  45 R,  45 G and  45 B are re-written, these LUTs can vary the levels of the color imaging data R, G and B supplied from the A/D converters  44 R,  44 G and  44 B for realizing optimum color balance adjustment. 
   Thus it is possible with the present imaging system to make color balance adjustment even in a grey area intermediate between the black and the white which has not been possible with the conventional white balance adjustment. 
   Also, with the above-described imaging system, the color balance can be adjusted easily and simply by designating an optional point of a graph of the LUT characteristics displayed on the display of the information processing device and by modifying the designated point according to the taste of the user. 
   In addition, with the above-described imaging system, in which color imaging data to the monitor device can be corrected by the LUT, the color balance adjustment can be realized as a whole in consideration of color variation between the monitoring device and the display of the information processing device. 
   With the imaging system, in which a particular object can be pre-arranged for setting the pickup point, color balance adjustment can be automatically realized for the grey area from black to white. 
   With the present imaging system, the following sequence may be used for adjusting the table data controlling the level of the color imaging data responsive to the color imaging signals. The table data are generated by the grey balance adjustment now explained. 
   The grey balance adjustment is performed in accordance with the flowchart shown in  FIGS. 14 to 16 . 
   First, the user prepares a white paper sheet at step S 31 , as shown in  FIG. 14 . At step S 32 , the user opens the diaphragm in order to permit the grey balance adjustment to be started at step S 33 . The processing for grey balance adjustment is executed by the CPU  30  of the camera head  3  and the CPU  69  of the digital processor  4 . 
   In the grey balance adjustment, the white level is set to a pre-set luminance level at step S 41  in the flowchart of  FIG. 15 . The white level setting is performed in accordance with the flowchart shown in  FIG. 16 . 
   That is, at step S 32 , the diaphragm is opened. Then, at step S 51 , it is checked whether or not the grey balance switch  9 D is pressed. If the grey balance switch  9 D is pressed, processing transfers to the next step S 52 . 
   In the steps S 52  to step S 55 , the imaging output of the white paper sheet is adjusted to a pre-set luminance level by changing one of the gain of the control circuit  24 , diaphragm of the imaging lens  2 , or the signal charge accumulation time of the CCD image sensor  21 , that is an electronic shutter. 
   The pre-set luminance level is set so that, if the signal level of the color imaging signals R, G and B for the white paper sheet with the diaphragm opened can be divided into 256 gradations, and the signal level of the green-colored imaging signal G corresponds to the 256th gradation, the green imaging data G outputted by the gain control circuit  24  corresponds to the 210th gradation. 
   That is, the white paper sheet is imaged by the camera head  3  with the diaphragm opened. An imaging output of the CCD image sensor  21  of the camera head  3  is supplied via pre-amplification circuit  23  to the gain control circuit  24 . An output of the gain control circuit  24 , that is green imaging data G, is supplied as a luminance level to the CPU  30 . 
   At step S 52 , the CPU  30  checks if the luminance level of the imaging output of the white paper sheet is smaller than a pre-set luminance level. If the luminance level is smaller than the pre-set luminance level, the CPU  30  transfers to step S 53  to increase the gain of the gain control circuit  24  in order to increase the luminance level. The CPU  30  then reverts to step S 52  in order to check the luminance level of the imaging output repeatedly. 
   If it is found at step S 54  that the luminance level of the imaging output is not smaller than the pre-set luminance level, the CPU  30  transfers to step S 54 . If the luminance level of the imaging output is larger than the pre-set luminance level, the CPU  30  transfers to step S 55  in order to control the diaphragm of the imaging lens  2  or the signal charge accumulation time of the CCD image sensor  21 , that is the electronic shutter, for decreasing the luminance level. The CPU  30  then reverts to step S 52  in order to check the luminance level of the imaging output repeatedly. 
   The above-mentioned control of the electronic shutter is performed by the CPU  30  changing the signal charge accumulation time of the CCD image sensor  21  via timing generator  34  and CCD driver  35 . 
   If the white level is set at step S 41  in the flowchart of  FIG. 15  to a pre-set luminance level, the CPU  30  of the camera head  3  transfers to step S 42  to instruct the digital processor  4  to capture the imaging data R, G and B into the frame memory  56 . The imaging data R, G and B, once captured by the frame memory  56 , are read from the frame memory  56  so as to be captured by the information processing device  5 . 
   At step S 43 , color balance correction data is formulated by the information processing device  5 . Such correction amounts R′ and B′, that will give R=G=B based on imaging color data G of the color imaging data R, G and B, are calculated. R′ and B′ are found from R′=R-G and B′=B-G, respectively. Based on the calculated correction amount data R′ and B′ and the color imaging data R, G and B, table data in the table memories  452 R,  452 G and  452 B in the LUTs  45 R,  45 G and  45 B are re-written at step S 44  by the CPU  69  of the digital processor  4 . 
   That is, if the correction data R′ and B are fed from the information processing device  5  to the SPC  63 , the CPU  69  of the digital processor  4  writes table data in the table memories  452 R,  452 G and  452 B in the LUTs  45 R,  45 G and  45 B via buffer memories  65 . 
   At step S 45 , it is checked whether or not the color imaging data R, G and B captured by the information processing device  5  via frame memory  56  are of the black luminance level. If the color imaging data are judged at this step S 45  not to be of the black luminance level, processing transfers to step S 46  in order to control the light exposure volume. At this step S 46 , a command is sent from the information processing device  5  to the CPU  30  of the camera head  3  in order for the CPU  30  to control the charge accumulation time of the CCD image sensor  21  or the light stop value of the imaging lens  2 . For light exposure volume control, a system of controlling the signal charge accumulation time under constant light stop value or a system of controlling the light stop under constant signal charge accumulation time may be selectively used such that the light exposure volume control as selected by the user is executed by the system. 
   In the light exposure volume control under constant light stop, the signal charge accumulation time of the CCD image sensor  21  is varied for lowering the effective light exposure volume. In the light exposure volume control under constant signal charge accumulation time of the electronic shutter, the light stop value of the imaging lens  2  is changed for lowering the light exposure volume at the time of imaging. 
   After lowering the light exposure volume, processing transfers to step S 43  again for calculating the correction amounts R′ and B′ based on the color imaging data R, G and B. The color imaging data R, G and B and the correction amounts R′ and B′ are written at step S 44  from the information processing device  5  via buffer memory  69  in the table memories  452 R,  452 G and  451 B of the LUTs  45 R,  45 G and  45 B. 
   The processing from step S 41  to step S 46  in the flowchart of  FIG. 15  is continued until the luminance level reaches the black level at step S 45 . This gives adjustment data for each grey level. When the luminance level reaches the black level, table data formulation by grey balance adjustment at step S 33  shown in  FIG. 14  comes to a close. 
   If the diaphragm or the signal charge accumulation time of the electronic shutter is controlled so as to be changed at a pre-set value, gradation control from the white level to the black level, executed in grey balance adjustment, can be changed continuously. This gives a desired number of samples from the white level to the black level. 
   With the table data, thus adjusted for grey balance, can be used for performing optimum color balance adjustment on subsequently inputted color imaging signals of the object, that is on color imaging data R, G and B supplied from the A/D converters  44 R,  44 G and  44 B. In this manner, color-balance adjusted camera side color imaging data R, G and B are outputted via D/A converter. 
   In this manner, with the present imaging system, color balance adjustment can be achieved even in a grey area intermediate between the black and white, which has not been possible with the conventional white balance adjustment. 
   Also, with the imaging system, color balance can be adjusted easily and simply by designating an optional point of the image displayed on a display of the information processing device and by modifying the designated point depending on the liking of the user. 
   In addition, with the imaging system, color balance adjustment in the grey area from black to white can be achieved automatically by arranging a specified object for setting a pickup point.