Abstract:
Whether a user of a video camera can discern an unnatural motion or the discernable unnatural motion is permissible is evaluated based on an taken image so as to make a change between mixing of still image shooting driving and maintaining of motion image shooting driving.

Description:
TECHNICAL FIELD 
     The present invention relates to an image pickup apparatus. 
     BACKGROUND ART 
     Recent image pickup apparatuses, such as a video camera, not only take and record motion images pursuant to the television standard but also take and record still images using pixels more than those for the television standard. In addition, as the number of pixels in the image sensor increases, it is necessary in the motion image shooting and recording to read out a two-dimensional image from the image sensor at least at a field period in accordance with the television standard. Therefore, in the motion image shooting and recording of the motion images, the number of readout pixels from the image sensor is reduced by cutting reading, thinning reading, and pixel adding reading, and the number of reading channels or the reading velocity is increased. However, the increased number of reading channels or a higher reading velocity will increase the cost and the consumption power, and thus a proposal to reduce the number of pixels to be read out of the image sensor is effective in the motion image shooting. Some video camera bodies may have a switch that switches between a motion image shooting mode and a still image shooting mode, a motion image shooting trigger, and a still image shooting trigger. 
     On the other hand, in order to keep the right timing to take a good image through simplified operations, it is proposed to eliminate switching between the motion image shooting mode and the still image shooting mode and to provide the still image shooting during the motion image shooting. See, for example, PLT1. PLT1 takes and records still images at a field timing that continues to a field timing used to generate a motion image, and supplements the field period in which the motion image is absent, by converting the still image into the motion image. 
     However, PLT1 poses a problem of an unnatural motion of a motion image when an absent motion image is format-converted from a still image during the still image shooting while the object is moving. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] 
         Patent No. 2001-352483 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The present invention provides an image pickup apparatus configured to prevent an unnatural output image as a result of a mixture of a still image into a motion image. 
     Solution to Problem 
     An image pickup apparatus according to one aspect of the present invention includes an image sensor configured to output an image signal by taking an object, a driver configured to drive the image sensor so as to take the object through interlace scanning or progressive scanning, a detector configured to detect a state of the object based on the image signal output from the image sensor, and a controller configured to control the driver to select one of interlace shooting used to take the object through the interlace scanning of the image sensor, and progressive shooting used to take the object through the progressive scanning of the image sensor, in accordance with the state of the object detected by the detector. 
     An image pickup apparatus according to another aspect of the present invention includes an image sensor configured to output an image signal by taking an object, a driver configured to drive the image sensor so as to take the object through interlace scanning or progressive scanning, and a controller configured to control the driver to drive the image sensor by the interlace scanning in taking and recording a still image during waiting to take and record a motion image or during taking and recording of the motion image, and to drive the image sensor by the progressive scanning in taking and recording the still image without taking or recording the motion image. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
     Advantageous Effects of Invention 
     The present invention can provide an image pickup apparatus configured to prevent an unnatural output image as a result of a mixture of a still image into a motion image. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a video camera (first embodiment). 
         FIG. 2  is a circuit diagram showing details of a structure of an image sensor shown in  FIG. 1 . 
         FIG. 3  is a timing chart of the image sensor shown in  FIG. 2 . 
         FIG. 4  is a timing chart of the image sensor shown in  FIG. 2 . 
         FIG. 5  is a timing chart of the image sensor shown in  FIG. 2 . 
         FIG. 6  is a timing chart of the image sensor shown in  FIG. 2 . 
         FIG. 7  is a block diagram showing details of a structure of an evaluation value generator shown in  FIG. 1 . 
         FIG. 8  is an illustrative image division of a motion vector detection (first embodiment). 
         FIG. 9  is an illustrative motion vector size histogram (first embodiment). 
         FIG. 10  is an illustrative motion vector direction histogram (first embodiment). 
         FIG. 11  is an illustrative motion vector size histogram by area (first embodiment). 
         FIG. 12A  is an example of a peripheral area histogram and  FIG. 12B  is an example of a central area histogram. 
         FIG. 13  is a block diagram of a video camera (second embodiment). 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Referring now to the accompanying drawings, a description will be given of embodiments according to the present invention. 
     Embodiment 1 
       FIG. 1  is a block diagram of a video camera (image pickup apparatus) according to this embodiment. 
     An image of an object is formed on an image sensor  2  through a lens  1 , and the image sensor  2  photographs the object and outputs a video output signal S 2 . A (first) selector  5  selects one of a vertical/horizontal (“V/H”) synchronization signal S 3  output from a first image sensor driving circuit  3  and a V/H synchronization signal S 4  output from a second image sensor driving circuit  4 . The selector  5  supplies, as its output signal S 5 , the V/H synchronization signal S 3  or S 4  to the image sensor  2 . 
     The first image sensor driving circuit  3  generates the V/H synchronization signal S 3  used to drive the image sensor  2  so as to convert an object image taken through interlace scanning of the image sensor  2  into an electric signal. The second image sensor driving circuit  4  generates the V/H synchronization signal S 4  used to drive the image sensor  2  so as to convert an object image taken through progressive scanning of the image sensor  2  into an electric signal. The video output signal S 2  corresponds to the interlace scanning when the V/H synchronization signal S 3  is supplied to the image sensor  2 , and to the progressive scanning when the V/H synchronization signal S 4  is supplied to the image sensor  2 . 
     The motion image signal processing circuit  6  receives, as input signals, the video output signal S 2  of the image sensor  2  and an output signal S 1  of the selector circuit  14 , performs motion-image signal processing for the video output signal S 2  of the image sensor  2 , and outputs, as an output signal S 6 , a motion image signal based on the interlace scanning. 
     The motion image recording processing circuit  7  receives, as input signals, the output signal S 6  of the motion image signal processing circuit  6  and an output signal S 131  of the CPU  13 , records the output signal S 6  of the motion image signal processing circuit  6  in a motion image recording medium  17  when the motion image is being recorded, and performs no process when the motion image is not being recorded. 
     The motion image display processing circuit  8  receives, as an input signal, the output signal S 6  of the motion image signal processing circuit  6 , and provides a process to display the output signal S 6  of the motion image signal processing circuit  6  in a display  18  attached to the image pickup apparatus. The motion image display processing circuit  8  performs the process to display the output signal S 6  of the motion image signal processing circuit  6  whether the selector  5  selects the first image sensor driving circuit  3  or the second image sensor driving circuit  4 . 
     The scan line interpolation circuit  9  receives, as an input signal, the output signal S 6  of the motion image signal processing circuit  6 . The scan line interpolation circuit  9  interpolates a scan line in the output signal S 6  of the motion image signal processing circuit  6  as a video signal of the interlace scanning, converts it into a video signal of the progressive scanning, and outputs the output signal S 9 . 
     The evaluation value generator  15  receives an input signal, the output signal S 6  of the motion image signal processing circuit  6 , and generates an evaluation value S 15  indicative of a state of a photographed motion image based on it. 
     The image evaluation part  16  receives, as an input signal, the evaluation value S 15  of the evaluation value generator  15 , and generates an image-sensor-driving determination signal S 16  indicative to the motion image driving determination and the still image driving determination based on it. The “motion image driving determination” is a determination that the image sensor  2  is to be driven for a motion image, and the “still image driving determination” is a determination that the image sensor  2  is to be driven for a still image. More specifically, the image evaluation part  16  determines (or evaluates) that the image sensor  2  is to be driven for a motion image, when a large motion of an object in a motion image is detected in a certain direction. In addition, the image evaluation part  16  determines that the image sensor  2  is to be driven for a still image, when no motion of an object is detected in a motion image. 
     The still image signal processing circuit  10  receives as an input signal the output signal S 2  of the image sensor  2 , performs still-image signal processing for this signal, and outputs as an output signal S 10  a video signal of the progressive scanning. 
     The selector  11  receives as input signals the output signal S 9  of the scan line interpolation circuit  9 , the output signal S 10  of the still image signal processing circuit  10 , and the output signal S 14  of the selector circuit  14 . The selector  11  selects one of the output signal S 9  of the scan line interpolation circuit  9  and the output signal S 10  of the still image signal processing circuit  10  based on the output signal S 14  of the selector circuit  14 , and outputs the selected signal as the output signal S 11 . More specifically, the selector  11  selects a third video signal of the scan line interpolation circuit  9  when the output signal S 14  of the selector circuit  14  is 0, and a second video signal of the still image signal processing circuit  10  when the output signal S 14  of the selector circuit  14  is 1. 
     The still image recording processing circuit  12  receives as input signals the output signal S 11  of the selector  11  and the output signal S 132  of the CPU  13 . The still image recording processing circuit  12  records the output signal S 11  of the selector  11  in a still image recording media  19  when a command to record a still image is issued, and performs no process when no command to record a still image is issued. 
     The CPU (controller)  13  outputs a signal S 131  indicating that a motion image is being recorded or that recording of a motion image recording is being waited, and a signal S 132  indicating that a command to record a still image is issued. More specifically, the CPU  13  outputs the output signal S 131  of 0 when no motion image is being recorded or that no recording of a motion image is being waited, and the output signal S 131  of 1 when a motion image is being recorded or that recording of a motion image is being waited. The CPU  13  outputs the output signal S 132  of 0 when no command to record a still image is issued, and the output signal S 131  of 1 when a command to record a still image is issued. 
     The operating part  20  includes a release button, an operation dial, a variety of buttons, a switch, and a lever, and informs the CPU  13  that a photographer has issued a command to take and record a motion or still image. The CPU  13  determines whether the command to take or record a motion or still image is issued, based on a notice from the operating part  20 . 
     The selector circuit  14  receives as input signals the output signal S 132  of the CPU  13  and the image-sensor-driving determination signal S 16 , and outputs as an output signal S 14  a synchronization signal provided to the image sensor  2  and an output signal that determines an operation of the motion image signal processing circuit  6 . The selector circuit  14  outputs an output signal S 14  of 0 (first state signal) when receiving the output signal S 16  form the image evaluation part  16  which indicates a determination signal that the image sensor  2  is to be driven for a motion image or when receiving the output signal S 132  from the CPU  13  which indicates that a command to take and record a motion image from a standby state or a command to take and record a still image is issued during the motion image shooting. The selector circuit  14  outputs an output signal S 14  of 1 (second state signal) when receiving the output signal S 16  form the image evaluation part  16  which indicates a determination that the image sensor  2  is to be driven for a still image or when receiving the output signal S 132  from the CPU  13  which indicates that a command to take and record a still image is issued from the standby state. 
     The selector  5  selects the first image sensor driving circuit  3  when the selector circuit  14  outputs the output signal S 14  of 0 (first stage signal). The selector  5  selects the second image sensor driving circuit  3  when the selector circuit  14  outputs the output signal S 14  of 1 (second stage signal). This configuration can prevent an unnatural output motion image as a result of a mixture of a still image into a motion image. 
       FIG. 2  is a circuit diagram showing a structure of the image sensor  2 , and shows only sixteen pixels of four vertical columns and four horizontal rows for description purposes, but actually there are more pixels of 1,080 vertical columns and horizontal 1,920 rows. 
     In  FIG. 2 , reference numeral  201  denotes a photoelectric conversion pixel part, including a photodiode  202 , a pixel readout switch  203 , and a charge voltage conversion buffer  204 . The image sensor  2  has a plurality of photoelectric conversion elements. Reference numerals  205 - 1  to  205 - 4  are column selection lines for the first to fourth columns, and column selection lines for the fifth to 1,080 th  are omitted. Reference numerals  206 - 1  to  206 - 4  are row selection lines for the first to fourth rows, and row selection lines for the fifth to 1,920 th  rows are omitted. Reference numerals  207 - 1  to  207 - 4  are row selection switches for first to fourth rows, and row selection switches for the fifth to 1,920 th  rows are omitted. 
     Reference numerals  208 - 1  to  208 - 4  are selection switches for first horizontal capacitors for the first to fourth rows, and selection switches for the fifth to 1,920 th  rows are omitted. Reference numerals  209 - 1  to  209 - 4  are selection switches for second horizontal capacitors for the first to fourth rows, and selection switches for the fifth to 1,920 th  rows are omitted. Reference numerals  210 - 1  to  210 - 4  are first horizontal capacitors for the first to fourth rows, and the first horizontal capacitors for the fifth to 1,920 th  rows are omitted. Reference numerals  211 - 1  to  211 - 4  are second horizontal capacitors for the first to fourth rows, and the second horizontal capacitors for the fifth to 1,920 th  rows are omitted. 
     Reference numerals  212 - 1  to  212 - 4  are horizontal driving switches for the first to fourth rows, and horizontal driving switches for the fifth to 1,920 th  rows are omitted. Reference numeral  213  denotes a vertical scanning circuit, and reference numeral  214  denotes a horizontal scanning circuit. Reference numeral  215  denotes a vertical synchronization signal input which is input from the first image sensor driving circuit  3  or the second image sensor driving circuit  4  via the selector  5 . Reference numeral  216  denotes a horizontal synchronization signal input which is input from the first image sensor driving circuit  3  or the second image sensor driving circuit  4  via the selector  5 . Reference numeral  217  denotes an output signal buffer, and reference numeral  218  denotes a video signal output. 
     The image sensor  2  operates as follows based on a synchronization signal provided by the first image sensor driving circuit  3  or the second image sensor driving circuit  4  via the selector  5 .  FIGS. 3 to 6  are timing charts of the image sensor  2 . 
     When the selector  5  selects the first image sensor driving circuit  3 , as shown in  FIG. 3 , the vertical synchronization signal is provided at a field driving period of 16.7 msec= 1/59.96 sec from the vertical synchronization signal input  215 , and a horizontal synchronization signal is provided at a field driving period of 29.78 microseconds=16.7 msec/560 H from the horizontal synchronization signal input  216 . Thereby, vertical driving for a vertical blanking period of 20H and a vertical effective period of 540H is provided. 
     In the first field shown in  FIG. 3 , the vertical scanning circuit  213  scans the column selection lines every two columns per one horizontal synchronization period after the vertical blanking period. In other words, the column selection lines  205 - 1  and  205 - 2  for the first and second columns, and the column selection lines  205 - 3  and  205 - 4  for the third and fourth columns, . . . the column selection lines for the 1079 th  and 1080 th  columns are scanned in these combinations. 
       FIG. 4  shows detailed operations of the column selection lines and the horizontal scanning circuit  214 . When the horizontal synchronization signal is asserted, in the subsequent time period t 1 -t 2 , the column selection line  205 - 1  for the first column is asserted, and the photoelectric conversion signals from 1920 photoelectric conversion elements connected to the column selection line  205 - 1  for the first column are simultaneously read out to the 1920 row signal lines. 
     As shown in  FIG. 4 , in the time period t 1 -t 2 , the row selection switch  207  and the selection switch  208  for the first horizontal capacitor are also simultaneously asserted. Assume that in  FIG. 4 , reference numeral  207  represents “ 207 - 1 ,” “ 207 - 2 ,” . . . , reference numeral  208  represents “ 208 - 1 ,” “ 208 - 2 ,” . . . , and reference numeral  209  represents “ 209 - 1 ,” “ 209 - 2 ,” . . . . The photoelectric conversion signals from the 1920 photoelectric conversion elements connected to the column selection line  205 - 1  for the first column are accumulated in the first horizontal capacitor (such as  210 - 1 ). 
     Next, in a time period t 3 -t 4 , the column selection line  205 - 2  for the second column is asserted, and the photoelectric conversion signal from the 1,920 photoelectric conversion elements connected to the column selection line  205 - 2  for the second column are read out. In the time period t 3 -t 4 , the row selection switches  207  and the selection switches  209  for the second horizontal capacitors are also simultaneously asserted. Therefore, the photoelectric conversion signals from the 1,920 photoelectric conversion elements connected to the column selection line  205 - 2  for the second column are accumulated in the second horizontal capacitor (such as  211 - 1 ). 
     Next, at the time t 5 , both the selection switches  208  for the first horizontal capacitors and the selection switches  209  for the second horizontal capacitors are asserted. As a result, the photoelectric conversion signals for the first column and the photoelectric conversion signals for the second column held by the first capacitors (such as  210 - 1 ) and the second horizontal capacitors (such as  211 - 1 ) are averaged. 
     Next, in a time period t 6 -t 7 , the horizontal driving switches (such as  212 - 1 ) for the 1,920 rows are sequentially asserted. Thus, the video signal made by vertically averaging the 1,920 photoelectric conversion element outputs for the first and second columns passes the output signal buffer  217 , and is output from the video signal  218 . At the time t 8  or later, an operation of the next horizontal synchronization period is performed (average reading of the photoelectric conversion signals for the third and fourth columns). 
     In the second field shown in  FIG. 3 , the vertical scanning circuit  213  scans the column selection lines every two columns per one horizontal synchronization period after the vertical blanking period. In other words, the column selection lines  205 - 2  and  205 - 3  for the second and third columns, and the column selection lines  205 - 4  for the fourth and fifth columns, . . . the column selection lines for the 1,080 th  and 1,081 th  columns are scanned (although the column selection line for the 1,081 th  column is a dummy). This configuration can change a combination of the averaging for two adjacent vertical lines. Thereby, the second field has an interlace-scanning relationship with the first field. 
     When the selector  5  selects the second image sensor driving circuit  4 , as shown in  FIG. 5 , a vertical synchronization signal is provided at a period of 33.4 msec= 1/29.97 sec that is twice as long as the field driving period from the vertical synchronization signal input  215 , and a horizontal synchronization signal is provided at a period of 29.78 microseconds=29.97 msec/1120 H from the horizontal synchronization signal input  216 . Thereby, vertical driving for a vertical blanking period of 20H, a vertical effective period of 1,080H, and a dummy period of 20H is provided. 
     The vertical scanning circuit  213  asserts every one column of the column selection line per one horizontal synchronization period after the vertical blanking period, and sequentially scans the column selection lines up to the column selection line for the 1,080 th  column. All the pixels are driven in a period of the two fields. 
       FIG. 6  shows detailed operations of the column selection lines and the horizontal scanning circuit  214 . When the horizontal synchronization signal is asserted, in the subsequent time period t 1 -t 2 , the column selection line  205 - 1  for the first column is asserted, and the row selection switches  207  and the selection switches  208  for the first horizontal capacitors are simultaneously asserted. Thereby, the photoelectric conversion signals from the 1,920 photoelectric conversion elements connected to the column selection line  205 - 1  for the first column are accumulated in the first horizontal capacitors (such as  210 - 1 ). 
     In the subsequent time period t 3 -t 5 , no action is performed because nothing is asserted. 
     Next, in the time period t 6 -t 7 , the horizontal driving switches (such as  212 - 1 ) for the 1,920 rows are sequentially asserted. Thus, the 1,920 photoelectric conversion signals for the first column pass the output signal buffer  217 , and are output from the video signal output  218 . At the time t 8  or later, the next horizontal synchronization period follows (reading of the photoelectric conversion signals for the second column). As a result, the video output as a result of progressive reading of all pixels is generated. 
     As described, when the selector  5  selects the V/H synchronization signal S 3  output from the first image sensor driving circuit  3 , the image sensor  2  outputs as the output signal S 2  the video signal of the interlace scanning at the field period. On the other hand, when the output signal S 5  from the selector  5  is the V/H synchronization signal S 4  output from the image sensor driving circuit  4 , the image sensor  2  outputs as the output signal S 2  the video signal of the progressive scanning at the frame period. 
     When the output signal S 14  from the selector circuit  14  is 0, the selector  5  outputs as the output signal S 5  the V/H synchronization signal S 3  output from the first image sensor driving circuit  3  so that the image sensor  2  can be driven by the interlace scanning at the field period. On the other hand, when the output signal S 14  from the selector circuit  14  is 1, the selector  5  outputs as the output signal S 5  the V/H synchronization signal S 4  output from the second image sensor driving circuit  4  so that the image sensor  2  can be driven by the progressive scanning at the frame period. 
     The motion signal processing circuit  6  receives, as input signals, the video output signal S 2  of the image sensor  2  and the output signal S 14  of the selector circuit  14 . When the output signal S 14  of the selector circuit  14  is 0, the motion image signal processing circuit  6  performs a variety of motion-image processes, such as an aperture correction, a gamma correction, a brightness adjustment, and a white balance, and a resize process to an angle of view of a format for the motion image recording, and outputs the resultant signal as the output signal S 6 . 
     On the other hand, when the output signal S 14  of the selector circuit  14  is 1, the output signal S 6  of the motion image signal processing circuit  6  is valid only to the motion image display processing circuit  8 . The motion image signal processing circuit  6  performs a resize process so that the output signal S 2  of the image sensor  2  can have the same angle of view as that of the motion image processing time, and outputs the output signal S 6  as the video signal of the interlace scanning. Alternatively, the motion image signal processing circuit  6  may output as the output signal S 6  the image signal indicating that a still image is recorded. 
     When the output signal S 131  of the CPU  13  is 1, the motion image recording processing circuit  7  records the output signal S 6  of the motion image signal processing circuit  6  in the motion image recording medium, because a motion image is being recorded. On the other hand, when the output signal S 131  of the CPU  13  is 0, the motion image recording processing circuit  7  does not perform any processes, because no motion image is being recorded. 
     The scan line interpolation circuit  9  performs a scan line interpolation process of the interlace scanning, and outputs as the output signal S 9  the video signal of the progressive scanning. For example, the scan line interpolation process utilizes a field memory to delay an input signal by one field, performs a motion determination and a gradient determination based on the information of the current field and one previous field, and generates an interpolation line signal. The video signal of the progressive scanning is output by outputting the interpolated line signal and the input signal. This scan line interpolation process is one example, and an interpolation signal may be generated using a plurality of fields. 
     The still image signal processing circuit  10  performs a variety of still-image processes, such as an aperture correction, a gamma correction, a brightness adjustment, and a white balance, and outputs the resultant signal as the output signal S 10 . 
     The selector  11  selects one of the output signal S 9  of the scan line interpolation circuit  9  and the output signal S 10  of the still image signal processing circuit  10 , and outputs the selected signal as the output signal S 11 . When the output signal S 14  of the selector circuit  14  is 0, the selector  11  outputs as the output signal S 11  the output signal S 9  of the scan line interpolation circuit  9 . On the other hand, when the output signal S 14  of the selector circuit  14  is 1, the selector  11  outputs as the output signal S 11  the output signal S 10  of the still image signal processing circuit  10 . 
     The still image recording processing circuit  12  receives, as input signals, the output signal S 11  of the selector  11  and the output signal S 132  of the CPU  13 . The output signal S 132  of the CPU  13  of 1 means that a command to record a still image is issued, and thus the still image recording processing circuit  12  records the output signal S 11  of the selector  11  in the still image recording medium. The output signal S 132  of the CPU  13  of 0 means that no command to record a still image is issued, and thus the still image recording processing circuit  12  performs no processes. 
     The evaluation value generator  15  generates an evaluation value S 15  indicative of a state of a photographed motion image.  FIG. 7  is a block diagram of a structure of the evaluation value generator  15 . In  FIG. 7 , reference numeral  701  denotes an input terminal that receives the output signal S 6  from the motion image signal processing circuit  6 . Reference numeral  702  denotes a frame memory. Reference numeral  703  denotes a motion vector detection circuit. Reference numeral  704  is a motion vector size histogram generation circuit. Reference  705  denotes a motion vector direction histogram generation circuit. 
     Reference numeral  706  denotes a motion vector size histogram generation circuit by area. Reference numeral  707  denotes a first histogram determination circuit. Reference numeral  708  denotes a second histogram determination circuit. Reference numeral  709  denotes a third histogram determination circuit. Reference numeral  710  is a specific object detection circuit. Reference numeral  711  is a main object determination part. Reference numeral  712  denotes a brightness level evaluation value detection circuit. Reference numeral  713  denotes an object brightness determination part. Reference numeral  714  a color evaluation value detection circuit. Reference numeral  715  denotes an object color determination part. 
     A description will now be given of an operation of the evaluation value generator  15 . The video signal S 6  that has undergone motion-image signal processing and been input from the input terminal  701  is input each of the frame memory  702 , the motion vector detection circuit  703 , the specific object detection circuit  710 , the brightness level evaluation value detection circuit  712 , and the color evaluation value detection circuit  714 . 
     The motion vector detection circuit  703  calculates a motion vector based on the video signal S 701  and the video signal S 702  that has been delayed by one frame by the frame memory  702 . The motion vector is calculated for each of small  256  blocks made by dividing the shooting angle of view by sixteen in length and sixteen in width, as shown in  FIG. 8 , and is separated into a size and a direction. As a result, size data S 703 - 1  and motion vector&#39;s direction data S 703 - 2  are generated for each of the 256 motion vectors. 
     The size data S 703 - 1  of the motion vector is input into the motion vector size histogram generation circuit  704  and the motion vector size histogram generation circuit by area  706 . The direction data S 703 - 2  of the motion vector is input into the motion vector direction histogram generation circuit  705 . 
     The motion vector size histogram generation circuit  704  generates motion vector histogram data S 704  based on size data S 703 - 1  of the 256 motion vectors, as shown in  FIG. 9 , and inputs it in the first histogram determination circuit  707 . 
     The first histogram determination circuit  707  also receives a first motion size detection threshold S 716  and a first motion size frequency threshold S 717 . The first histogram determination circuit  707  determines, as shown in  FIG. 9 , whether there are a predetermined number of blocks or more in each of which a motion having a predetermined size is detected, and outputs a first motion determination output S 707 . In a situation where the first motion determination output S 707  is asserted, it is determined that the object of the photographed motion image is moving with a predetermined size over a predetermined area. 
     The motion vector direction histogram generation circuit  705  generates motion vector direction histogram data S 705  based on the direction data S 703 - 2  of the 256 motion vectors, as shown in  FIG. 10 , and inputs it the second histogram determination circuit  708 . 
     The second histogram determination circuit  708  also receives the motion direction frequency threshold S 718 . The second histogram determination circuit  708  determines, as shown in  FIG. 10 , whether there are a predetermined number of blocks or more in each of which a motion in a predetermined direction is detected, and outputs the second motion determination output S 708 . In a situation where the second motion determination output S 708  is asserted, it is determined that the object of the photographed motion image is conspicuously moving in the specific direction. 
     The motion vector size histogram generation circuit by area  706  receives the size data S 703 - 1  of the 256 motion vectors. As shown in  FIG. 11 , the motion vector size histogram generation circuit by area  706  divides the 256 motion vectors into a screen central part and a screen peripheral part, generates the motion vector size histogram data S 706  for each area, and inputs it into the third histogram determination circuit  709 . 
     The third histogram determination circuit  709  also receives the second motion size detection threshold S 719  and the second motion size frequency threshold S 720 . The third histogram determination circuit  709  determines, as shown in  FIG. 12 , whether there are a predetermined number of blocks or more in each of which a motion having a predetermined size is detected for each of the screen central part and the screen periphery part, and outputs a third motion determination output S 709  when it is determined that the motion exits only in the peripheral part. 
       FIG. 12A  shows a peripheral area histogram, and  FIG. 12B  shows a central area histogram. In the situation where the third motion determination output S 709  is asserted, it is determined that the object of the photographed motion image is comparatively stationary, there is a motion in the background, and the object is panned. 
     The specific object detection circuit  710  detects, based on the input video signal S 701 , where an object having a specific feature, such as a human face, is located in the photographed motion image, and outputs a plurality of pieces of object position information S 710 . The main object determination part  711  determines one specific object based on the plurality of pieces of object position information S 710 , and outputs the main object position information S 711 . By referring to the main object position information S 711 , it can be determined whether a specific object exists in the photographed motion image. 
     The brightness level evaluation value detection circuit  712  generates a brightness level evaluation value S 712  based on the video signal S 701 , for example, by extracting a brightness signal, by dividing a screen into a plurality of blocks for the brightness signal of the photographed motion image, and by generating an integral value of a brightness signal for each of a plurality blocks. The brightness level evaluation value S 712  and the object brightness determination level S 721  are input into the object brightness determination part  713 . 
     The object brightness determination part  713 , for example, compares a brightness evaluation value in the screen central part with the object brightness determination level S 721 , and outputs the object&#39;s brightness level determination result S 713 . By referring to the object&#39;s brightness level determination result S 713 , a value of the object&#39;s brightness relative to the object brightness determination level S 721  can be determined. 
     The color evaluation value detection circuit  714 , generates a specific color evaluation value S 714  based on the video signal S 701 , for example, by extracting a color difference signal, by dividing a screen into a plurality of blocks for a color difference signal of the photographed motion image, and by integrating only color difference signals having specific values for each of a plurality blocks. The specific color evaluation value S 714  and the object color determination level S 722  are input into the object color determination part  715 . The object color determination part  715  determines, for example, whether a specific color concentrates on the screen central part, and outputs an object&#39;s color level determination result S 715 . By referring to the object&#39;s color level determination result S 715 , it is determined whether the color of the object is contained in a specific color difference signal range. 
     As described above, the evaluation value S 15  from the evaluation value generator  15  includes the first to third motion determination outputs S 707 , S 708 , and S 709 , the main object position information S 711 , the object&#39;s brightness level determination result S 713 , and the object&#39;s color level determination result S 715 . As a result, the evaluation value S 15  indicates one of motion information of the object, information indicating whether a specific portion exists, information identifying a specific object among a plurality of objects, object&#39;s brightness information, and object&#39;s color information. 
     The image evaluation part  16  provides a motion image driving determination and a still image driving determination based on the evaluation value S 15 , as described later. Initially, the image evaluation part  16  generates a motion-image-driving determination signal S 16  based on the first motion determination output S 707  and the second motion determination output S 708 , when a large motion having a predetermined size or larger in a predetermined direction in the photographed motion image is detected. This configuration can prevent unnaturalness of a large movement of the object that is likely to be visually detected. 
     In addition, the image evaluation part  16  generates, based on the third motion determination output S 709 , a determination signal S 16  that indicates that the image sensor  2  should be driven for a still image, when it is determined that a photographer is intentionally panning (when the peripheral part has a larger motion than the central part in the motion image). In addition, the image evaluation part  16  generates, based on the main object position information S 711 , a determination signal S 16  that indicates that the image sensor  2  should be driven for a still image on the premise that a photographer is taking a desired object, when it is determined that a specific portion, such as a face of an object, exits in the photographed motion image. Thereby, even when there is a large and unnatural movement of an object which is likely to be visually detected, this is pursuant to the photographer&#39;s intension. 
     In addition, when the image evaluation part  16  determines, based on the object&#39;s brightness level determination result S 713 , that the object&#39;s brightness is lower than the threshold, the image evaluation part  16  generates a still-image-driving determination signal S 16 . In addition, when the image evaluation part  16  determines, based on the object&#39;s color level determination result S 715 , that the object&#39;s color is close to yellow (or within a specific color difference range that has yellow at the center), the image generation part  16  generates a motion-image-driving determination signal S 16 . Thereby, the image evaluation part  16  can change controls over unnaturalness depending upon a level at which the large movement of the object is visually detected. 
     In some cases, the image evaluation part  16  cannot uniquely determine whether the determination signal S 16  determines motion image driving or still image driving based on S 707 , S 708 , S 709 , S 711 , S 713 , and S 715  in the evaluation value S 15 . In these cases, the image evaluation part  16  may use a predetermined priority order, a majority rule, a known multivariate analysis result, a known neural network determination result, etc. 
     The selector circuit  14  receives, as input signals, the output signal S 132  of the CPU  13  and the determination signal S 16  used to drive the image sensor. When the output signal S 132  of the CPU  13  is 1 and the determination signal S 16  determines motion image driving, the output signal S 14  of the selector circuit  14  becomes 0 and the image sensor  2  is controlled under field motion image driving of the interlace scanning. The motion image signal processing circuit  6  provides field motion image processing by the interlace scanning, and the field motion image is supplied to the motion image recording processing circuit  7  and the motion image display processing circuit  8 . In addition, the selector  11  communicates the output signal S 9  of the scan line interpolation circuit  9  to the still image recording processing circuit  12 . 
     When the output signal S 132  of the CPU  13  is 1 and the determination signal S 16  used to drive the image sensor determines still image driving, the output signal S 14  of the selector circuit  14  becomes 1 and the image sensor  2  is controlled under still image driving of the progressive scanning. The output signal S 6  of the motion image signal processing circuit  6  is valid only relative to the motion image display processing circuit  8 , the output signal S 2  of the image sensor  2  is resized so that it has the same angle of view as that for the motion image processing time, and is output as a video signal of the interlace scanning. Alternatively, an image indicating that the still image is recorded may be output as an output signal S 6 . The still image signal processing circuit  10  provides still image processing by the progressive scanning, and the selector  11  communicates the output signal S 10  of the still image signal processing circuit  10  to the still image recording processing circuit  12 . 
     Embodiment 2 
       FIG. 13  is a block diagram of a video camera (image pickup apparatus) according to a second embodiment. Those elements in  FIG. 13 , which are the same as corresponding elements in  FIG. 1 , are designated by the same reference numerals, and a duplicate description will be omitted. Since the structure and timing chart of the image sensor  2  in this embodiment are similar to those of  FIGS. 2-6  in the first embodiment, a description thereof will be omitted. 
     An image of the object is formed onto the image sensor  2  through the lens  1 , and the image sensor  2  photographs the object and outputs the video output signal S 2 . The (first) selector  5  selects one of the V/H synchronization signal S 3  output from the first image sensor driving circuit  3  and the V/H synchronization signal S 4  output from the second image sensor driving circuit  4 . The V/H synchronization signal S 3  or S 4  selected by the selector  5  is supplied as its output signal S 5  to the image sensor  2 . 
     The first image sensor driving circuit  3  generates the V/H synchronization signal S 3  configured to drive the image sensor  2  so as to convert the object image taken through the interlace scanning of the image sensor  2  into an electric signal. The second image sensor driving circuit  4  generates the V/H synchronization signal S 4  configured to drive the image sensor  2  so as to convert the object image taken through the progressive scanning of the image sensor  2  into an electric signal. The video output signal S 2  corresponds to the interlace scanning when the V/H synchronization signal S 3  is supplied to the image sensor  2 , and corresponds to the progressive scanning when the V/H synchronization signal S 4  is supplied to the image sensor  2 . 
     Reference numeral  30  denotes an analog front end (“AFE”) that includes a correlated double sampling (“CDS”) circuit and an analog-to-digital (A/D) conversion circuit. The CDS circuit is a circuit configured to remove a reset noise that is dominant in the noises contained in the video output signal S 2  of the image sensor  2 . The A/D conversion circuit is a circuit configured to convert an analogue image into a digital image. The AFE  30  is a circuit configured to convert an analogue signal into a digital signal that is processible by the motion image signal processing circuit  6 . 
     The motion signal processing circuit  6  receives, as input signals, the output signal S 30  of the AFE  30  and the output signal S 14  of the selector circuit  14 , performs motion-image signal processing for the output signal S 30  of the AFE  30 , and outputs as the output signal S 6  the motion image signal based on the interlace scanning. 
     The motion image recording processing circuit  7  receives, as input signals, the output signal S 6  of the motion image signal processing circuit  6  and the output signal S 131  of the CPU  13 , and records the output signal S 6  of the motion image signal processing circuit  6  in the motion image recording media  17  when the motion image is being recorded, and provides no process when the motion image is not being recorded. 
     The motion image display processing circuit  8  receives as an input signal the output signal S 6  of the motion image signal processing circuit  6 , and displays the output signal S 6  of the motion image signal processing circuit  6  in the display  18  attached to the image pickup apparatus. The motion image display processing circuit  8  displays the output signal S 6  of the motion image signal processing circuit  6  whether the selector  5  selects the first image sensor driving circuit  3  or the second image sensor driving circuit  4 . 
     The scan line interpolation circuit  9  receives as an input signal the output signal S 6  of the motion image signal processing circuit  6 . The scan line interpolation circuit  9  interpolates a scan line in the output signal S 6  of the motion image signal processing circuit  6  as the video signal of the interlace scanning, converts it into the video signal of the progressive scanning, and outputs the output signal S 9 . 
     The still image signal processing circuit  10  receives the output signal S 20  of the AFE  30  as an input signal, performs still image signal processing for that signal, and outputs the output signal S 10  as the video signal based on the progressive scanning. 
     The selector  11  receives as receiving signals the output signal S 9  of the scan line interpolation circuit  9 , the output signal S 10  of the still image signal processing circuit  10 , and the output signal S 131  of the CPU  13 . The selector  11  selects one of the output signal S 9  of the scan line interpolation circuit  9  and the output signal S 10  of the still image signal processing circuit  10 , based on a value of the output signal S 131  of the CPU  13 , and outputs the selected signal as the output signal S 11 . More specifically, the selector  11  selects the third video signal of the scan line interpolation circuit  9  when the output signal S 131  of the CPU  13  is 0, and selects the second video signal of the still image signal processing circuit  10  when the output signal S 131  of the CPU  13  is 1. 
     The still image recording processing circuit  12  receives, as input signals, the output signal S 11  of the selector  11  and the output signal S 132  of the CPU  13 . The still image recording processing circuit  12  records the output signal S 11  of the selector  11  in the still image recording media  19  when a command to record a still image is issued, and no process is performed when no command to record a still image is issued. 
     The CPU (controller)  13  outputs the (first identification) signal S 131  indicating whether the motion image is being recorded or recording of the motion image is waited, or the (second identification) signal S 132  indicating whether a command to record a still image is issued. In other words, the CPU  13  outputs the output signal S 131  of 0 when no motion image is being recorded or no recording of the motion image is waited, and outputs the output signal S 131  of 1 when a motion image is being recorded or recording of the motion image is waited. The CPU  13  outputs the output signal S 132  of 0 when no command to record a still image is issued, and outputs the output signal S 132  of 1 when a command to record a still image is issued. 
     The operating part  20  includes a release button, an operation dial, a variety of buttons, a switch, and a lever, and informs the CPU  13  that a photographer has instructed to take and record a motion or still image. The CPU  13  determines whether a command to take or record a motion or still image is issued, based on a notice from the operating part  20 . 
     The selector circuit  14  receives, as input signals, the output signals S 131  and S 132  of the CPU  13 , and outputs a synchronization signal to be provided to the image sensor  2  and an output signal S 14  that determines an operation of the motion image signal processing circuit  6 . When the output signal S 131  from the CPU  13  of 1 indicating that a motion image is being recorded or recording of a motion image is waited is output, and the output signal S 132  of 1 indicating that a command to record a still image is output, it is understood that a command to record a still image is issued when the motion image is being recorded or recording of the motion image is waited. When the output signal S 131  from the CPU  13  of 1 indicating that a motion image is being recorded or recording of a motion image is waited is output, and the output signal S 132  of 0 indicating that no command to record a still image is output, it is understood that a motion image is being recorded or recording of a motion image is waited. 
     In either case, the selector circuit  14  outputs as the output signal S 14  a (first state) signal  0  indicating one of the states where a shooting of a motion image is waited, a motion image is being photographed, a still image is recorded when a shooting of a motion image is waited, or a still image is recorded while a motion image is being photographed. 
     When the output signal S 131  from the CPU  13  of 0 indicating that no motion image is being recorded or no recording of the motion image is waited is output, and the output signal S 132  of 1 indicating that that a command to record a still image is output, it is understood that a command to record a still image is issued when no motion image is being recorded or no recording of a motion image is waited. In this case, the selector circuit  14  outputs as the output signal S 14  a (second state) signal  1  indicating that the still image is recorded. 
     The selector  5  selects the first image sensor driving circuit  3  when the selector circuit  14  outputs the first state signal  0  as the output signal S 14 . In addition, the selector selects the second image sensor driving circuit  4  when the selector circuit  14  outputs the second state signal  1  as the output signal S 14 . This configuration can prevent a still image from being mixed in a motion image, and an output image from being unnatural. 
     When the output signal S 14  of the selector circuit  14  is 0, the selector  5  outputs as the output signal S 5  the V/H synchronization signal S 3  output from the first image sensor driving circuit  3  so that the image sensor  2  can be driven by the interlace scanning at a field period. On the other hand, the output signal S 14  of the selector circuit  14  is 1, the selector  5  outputs as the output signal S 5  the V/H synchronization signal S 4  output from the second image sensor driving circuit  4  so that the image sensor  2  can be driven by the progressive scanning at a frame period. 
     The motion image signal processing circuit  6  receives as input signals the output signal S 30  of the AFE  30  and the output signal S 14  of the selector circuit  14 . When the output signal S 14  of the selector circuit  14  is 0, the motion image signal processing circuit  6  performs a variety of motion-image processes, such as an aperture correction, a gamma correction, a brightness adjustment, and a white balance, performs a resize process for the angle of view of the format for the motion image recording, and outputs the output signal S 6 . On the other hand, when the output signal S 14  of the selector circuit  14  is 1, the output signal S 6  of the motion image signal processing circuit  6  is valid only to the motion image display processing circuit  8 . The motion image signal processing circuit  6  provides a resize process for the output signal S 30  of the AFE  30  so that it can have the same angle of view as that for the motion image processing time, and outputs the output signal S 6  as the video signal of the interlace scanning. Alternatively, the motion image signal processing circuit  6  may output the output signal S 6  as an image signal that indicates that a still image is recorded. 
     When the output signal S 131  of the CPU  13  is 1, the motion image recording processing circuit  7  records the output signal S 6  of the motion image signal processing circuit  6  in the motion image recording medium, because a motion image is being recorded. When the output signal S 131  of the CPU  13  is 0, the motion image recording processing circuit  7  performs no processes because no motion image is being recorded. 
     The scan line interpolation circuit  9  performs a scan line interpolation process of the interlace scanning, and outputs as the output signal S 9  the video signal of the progressive scanning. The scan line interpolation process, for example, uses a field memory configured to delay an input signal by one field, performs a motion determination and a gradient determination based on the information of the current field and one previous field, and generates an interpolation line signal. The video signal of the progressive scanning is output by outputting this input signal and this interpolation line signal. This scan line interpolation process is illustrative, and the interpolation signal may be generated by using a plurality of fields. 
     The selector  11  selects one of the output signal S 9  of the scan line interpolation circuit  9  and the output signal S 10  of the still image signal processing circuit  10 , and outputs the selected signal as the output signal S 11 . When the output signal S 131  of the CPU  13  is 1, the selector  11  outputs as the output signal S 11  the output signal S 9  of the scan line interpolation circuit  9 . On the other hand, when the output signal S 131  of the CPU  13  is 0, the selector  11  outputs as the output signal S 11  the output signal S 10  of the still image signal processing circuit  10 . 
     The still image recording processing circuit  12  receives, as input signals, the output signal S 11  of the selector  11  and the output signal S 132  of the CPU  13 . The output signal S 132  of the CPU  13  is 1 means that a command to record a still image is issued, and thus the still image recording processing circuit  12  records the output signal S 11  of the selector  11  in the still image recording media. The output signal S 132  of the CPU  13  is 0 means that no command to record the still image is issued, and thus the still image recording processing circuit  12  performs no processes. 
     The selector circuit  14  receives as input signals the outputs S 131  and S 132  of the CPU  13 . When the output signal S 131  of the CPU  13  is 0 and the output signal S 132  of the CPU  13  is 1, the output signal S 14  of the selector circuit  14  becomes 1 and the image sensor  2  is controlled under still image driving of the progressive scanning. The output signal S 6  of the motion image signal processing circuit  6  is valid only to the motion image display processing circuit  8 , performs a resize process for the output signal S 30  of the AFE  30  so that it can have the same angle of view as that for the motion image processing time, and outputs as the output signal S 6  the video signal of the interlace scanning. Alternatively, an image that indicates that a still image is recorded may be output as the output signal S 6 . The still image signal processing circuit  10  performs image processing for a still image of the progressive scanning, and the selector  11  communicates the output signal S 10  of the still image signal processing circuit  10  to the still image recording processing circuit  12 . 
     In other cases, the output signal S 14  of the selector circuit  14  becomes 0, and the image sensor  2  is controlled under field motion image driving of the interlace scanning. In addition, the motion image signal processing circuit  6  performs field motion image processing of the interlace scanning, and the motion image recording processing circuit  7  and the motion image display processing circuit  8  are supplied with field motion images. Alternatively, the selector  11  communicates the output signal S 9  of the scan line interpolation circuit  9  to the still image recording processing circuit  12 . 
     According to this embodiment, both the motion image shooting operation and the still image shooting operation are made simple and a still image can be photographed while a motion image is being photographed so as to keep a right moment to take a good image. In this case, the deterioration of the resolution can be restrained in a recorded still image. In addition, an unnatural motion that would occur in a displayed or recorded motion image can be restrained so that it cannot be detected by a user of a video camera or it can be maintained at a permissible level. 
     INDUSTRIAL APPLICABILITY 
     The image pickup apparatus is applicable to a video camera. 
     This application claims a benefit of priority based on Japanese Patent Applications Nos. 2008-168493, filed on Jun. 27, 2008, and 2008-145333, filed on Jun. 3, 2008, each of which is hereby incorporated by reference herein in its entirety as if fully set forth herein. 
     REFERENCE SIGNS LIST 
     
         
           2  Image sensor 
           3  First image sensor driving circuit 
           4  Second image sensor driving circuit 
           13  CPU 
           15  Evaluation value generation part