Patent Publication Number: US-7710493-B2

Title: Image-pickup apparatus and focus control method

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to an image-pickup apparatus, such as a video camera and a digital still camera, and more particularly to focus control in the image-pickup apparatus. 
   In the autofocus (“AF”) control in a video camera and the like, a TV-AF method is mainstream, which generates an AF evaluation value signal indicative of sharpness or a contrast state of an image signal generated by using an image-pickup element, and searches for a focus lens position that maximizes the AF evaluation value signal level. 
   One AF method is an external ranging method or external ranging (or distance-measuring) phase (difference) detection method that provides a ranging sensor independent of an image-pickup lens, operates an in-focus position of a focus lens from a distance to the object detected by the ranging sensor, and moves the focus lens to the in-focus position. 
   The external phase difference detection method divides a luminous flux from the object into two luminous fluxes, receives a pair of divided rays through a pair of light-receiving element arrays (line sensors), and detects a shift amount between the images formed on the pair of line sensors or a phase difference. Then, this method calculates an object distance based on the phase difference by using the triangulation, and moves a focus lens to an in-focus position corresponding to the object distance. 
   An internal phase detection method is also known, which divides into two the luminous flux that has passed an exit pupil of an image-pickup lens, and receives the two divided rays through a pair of line sensor. Then, this method detects a phase difference between the two images on the pair of line sensors, calculates a defocus amount of the image-pickup lens from the phase difference, and moves the focus lens by an amount corresponding to the defocus amount. 
   In order to utilize the high focusing precision of the TV-AF method and the focusing speed of the phase difference detection method, Japanese Patent Laid-Open No. 2005-84426 proposes a hybrid AF method that combines these AF methods. The hybrid AF method proposed in Japanese Patent Laid-Open No. 2005-84426 obtains an in-focus state by using the phase difference detection method, when the TV-AF system does not provide the in-focus state due to low brightness or low contrast of the object. 
   Japanese Patent Laid-Open No. 05-346536 proposes an image-pickup apparatus that utilizes the phase difference detection method to find a coincidence between image patterns, i.e., the similarity between the two images on the line sensors, and to thereby determine the reliability of the distance measurement result. 
   However, the conventional hybrid AF method initially provides TV-AF focus control, and then determines whether phase detection focus control is necessary, depending upon a condition of the TV-AF focus control. Therefore, an advantage of the phase difference detection system, i.e., responsive and fast focus control, is unavailable, when a photographer desires. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is directed to an image-pickup apparatus and a focus control method which can provide focus control of the AF method fit for a user&#39;s (or photographer&#39;s) intension. 
   An image-pickup apparatus according to one aspect of the present invention includes a first detector configured to generate first information corresponding to a contrast state of a picked-up image, a second detector configured to detect second information that is used for focus control and different from the first information, a controller configured to provide the focus control, and a first operating member operable by a user, wherein the controller provides the focus control that uses the first information but does not use the second information when the first operating member is not operated, and provides the focus control that uses at least the second information when the operating member is operated. 
   A focus control method according to another aspect of the present invention includes the steps of obtaining first information relating to a contrast state of an picked-up image, obtaining second information that is used for focus control and different from the first information, detecting an operation of an first operating member operable by a user, and providing the focus control that uses the first information but does not use the second information when an operation of the first operating member is not detected, and providing the focus control that uses at least the second information when the operation of the first operating member is detected. 
   Other objects and further features of the present invention will become readily apparent from the following description of the preferred embodiments with reference to accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a video camera according to one embodiment of the present invention. 
       FIG. 2  is a flowchart of AF control according to one embodiment. 
       FIG. 3  is a view for explaining a minute-drive operation in the TV-AF. 
       FIG. 4  is a view for explaining a climbing-drive operation in the TV-AF. 
       FIG. 5  is a flowchart for explaining an input process according to one embodiment. 
       FIG. 6  is a view of a ranging principle in a passive phase difference method. 
       FIG. 7  is a view of an image signal in the passive phase difference method. 
       FIG. 8  is a view for explaining a coincidence between two images formed on a pair of light-receiving element arrays. 
       FIG. 9  is a view for explaining a coincidence between two images formed on a pair of light-receiving element arrays. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings, a description will be given of a preferred embodiment according to the present invention. 
     FIG. 1  shows a structure of a video camera (image-pickup apparatus) according to one embodiment of the present invention. While this embodiment discusses the video camera, the present invention is applicable to another image-pickup element, such as a digital still camera. 
   In  FIG. 1 ,  101  denotes a first fixed lens,  102  a magnification-varying lens that moves in the optical-axis direction and varies a magnification, and  103  a stop aperture.  104  denotes a second fixed lens,  105  denotes a focus compensator lens (referred to as a “focus lens” hereinafter) that serves not only to correct a movement of a focal plane caused by the magnification variance but also to provide focusing. The first fixed lens  101 , the magnification-varying lens  102 , the stop aperture  103 , the second fixed lens  104 , and the focus lens  105  constitute an image-pickup optical system. 
     106  denotes an image-pickup element as a photoelectric conversion element, such as a CCD sensor and a CMOS sensor.  107  denotes a CDS/AGC circuit that samples an output of the image-pickup element  106 , and adjusts a gain. 
     108  denotes a camera signal processing circuit, which provides various image processes to an output signal from the CDS/AGC circuit  107 , and generates a video signal.  109  denotes a monitor that includes an LCD or the like, and displays a video signal from the camera signal processing circuit  108 .  110  is a recorder, which records a video signal from the camera signal processing circuit  108  in a recording medium, such as a magnetic tape, an optical disc, and a semiconductor memory. 
     111  denotes a zoom driving source that is used to move the magnification-varying lens  102 .  112  denotes a focusing driving source that is used to move the focus lens  105 . The zoom driving source  111  and the focusing driving source  112  include an actuator, such as a stepping motor, a DC motor, a variation motor, and a voice coil motor. 
     113  denotes an AF gate that allows a signal in a region used for focus detections in an output signal of all pixels from the CDS/AGC circuit  107 .  114  is an AF signal processing circuit that serves as a first detector. The AF signal processing circuit  114  generates an AF evaluation value signal that serves as first information by extracting from the signal that has passed the AF gate  113 , a high-frequency component and a brightness difference component that is generated from the high-frequency signal and expresses a difference between a maximum value and a minimum value of a brightness level in the signal that has passed the AF gate  113 . The AF evaluation value signal is output to the camera/AF microcomputer  115 . The AF evaluation value signal indicates sharpness (or a contrast state) of an image generated based on an output signal from the image-pickup element  106 , but resultantly serves as a signal indicative of a focus state of the image-pickup optical system, because the sharpness depends upon the focusing state of the image-pickup optical system. 
   The camera/AF microcomputer as a controller (simply referred to as a “microcomputer” hereinafter)  115  governs controls of the entire operations of the video camera, and provides focus control that controls the focusing driving source  112 , and moves the focus lens  105 . The focus control of the microcomputer  115  includes focus control of the TV-AF method (simply referred to as “TV-AF” hereinafter), and focus control of the external phase difference detection system or external ranging system (simply referred to as “external AF” hereinafter). 
     116  denotes an external ranging unit that serves as a second detector, and outputs a signal (second information which is referred to as “object distance information” hereinafter) corresponding to a distance to the object. Various ranging methods are conventionally used, and  FIGS. 6 and 7  show a ranging principle of the passive phase difference method as one ranging method. The external ranging unit is provided different from the image-pickup optical system. In other words, a luminous flux from the object which does not pass the image-pickup optical system enters the external ranging unit. 
   In  FIG. 6 ,  201  denotes an object,  202  a first image-forming lens,  203  a light-receiving element array,  204  a second image-forming lens, and  205  a second light-receiving element array. Each of the first and second light-receiving element arrays  203  and  205  includes an array of plural light-receiving elements (pixels). The first and second light-receiving element arrays  203  and  205  are arranged part from each other by a base length B. 
   The light that has passed the first imaging lens  202  among the light from the object  201  images on the first light-receiving element array  203 , and the light that has passed the second imaging lens  204  images on the second light-receiving element array  205 . 
     FIG. 7  shows illustrative output signals (image signals) from the first and second light-receiving element arrays  203  and  205 . Since the first and second light-receiving element arrays  203  and  205  are separated from each other by the base length B, the image signal from the first light-receiving element array  203  and the image signal from the second light-receiving element array  205  shift by the number of pixels X. X can be operable when a correlation between the two image signals is operated by shifting the pixels, and a pixel shift amount is found that maximizes the correlation. A distance L to the object can be found by the following equation below using the triangulation principle and X, the base length B, and the focus lengths f of the image-forming lenses  202  and  204 :
   L=B·f/X    
   The present invention is not limited to the passive ranging method, but may use another ranging method. For example, an active ranging method may be used, such as a system that projects the infrared ray and finds a distance using the triangulation principle, and a system that measures a propagation speed using an ultrasonic sensor. In addition, a pixel shift amount (second information) X may be output from the external ranging unit, and an object distance may be found using the microcomputer based on X. 
   The object distance information from the external ranging unit  116  is input into the microcomputer  115 . The microcomputer  115 , in turn, calculates, based on the input object distance information, a focus lens position (referred to as an “external ranging in-focus position” hereinafter) which provides an in-focus state relative to the object of the distance. The term “calculates,” as used herein, means an operation using an equation as well as data reading of the in-focus position relative to the object distance stored in a memory (not shown). 
   The microcomputer  115  also calculates the reliability of the object distance information. The reliability is a coincidence (correlation) between two images formed on a pair of light-receiving element arrays by two luminance fluxes split by two image-forming lenses in the external ranging unit  116 . A calculation method of the reliability will be given with reference to  FIG. 8 . 
   First, Equation 1 below is calculated from intensity data of each of a first image (or image E in  FIG. 8 ) and a second image (image F in  FIG. 8 ) sampled by each light-receiving element array, where a j  and b j  are intensity data of an image, and N is the number of pixels included in the light-receiving element array: 
   
     
       
         
           
             
               
                 
                   U 
                   o 
                 
                 = 
                 
                   
                     ∑ 
                     
                       j 
                       = 
                       1 
                     
                     N 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                      
                     
                       
                         a 
                         j 
                       
                       - 
                       
                         b 
                         j 
                       
                     
                      
                   
                 
               
             
             
               
                 Equation 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 1 
               
             
           
         
       
     
   
   A value of U o  in Equation 1 or an area of the beveled part in  FIG. 9  becomes smaller, as the coincidence between two images increases, and minimum in the in-focus state. The calculation (that shifts sampling data of the image E relative to the image E by p pixels is performed for the image F, similar to a calculation of the value of U o  in Equation 1, to find a value of U p  defined in Equation 2 below, where p is an integer: 
   
     
       
         
           
             
               
                 
                   U 
                   p 
                 
                 = 
                 
                   
                     ∑ 
                     
                       j 
                       = 
                       1 
                     
                     
                       N 
                       - 
                       p 
                     
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                      
                     
                       
                         a 
                         
                           j 
                           + 
                           p 
                         
                       
                       - 
                       
                         b 
                         j 
                       
                     
                      
                   
                 
               
             
             
               
                 Equation 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 2 
               
             
           
         
       
     
   
   Since U p  becomes minimum at the shift amount that has the highest coincidence between the two images, a relative positional shift amount between two images can be found by finding the shift amount p as shown in  FIG. 9 . 
   However, a defocus amount corresponding to a shift of 1 pixel changes by 1 mm, and this value cannot be used as it is to detect the focal point. Accordingly, a displacement amount (h) of an image finer than the minimum size of one pixel is interpolated and operated from near the minimum value of U p  in  FIG. 9 . 
   Reliability FNCLVL is calculated, for example, by Equation 3 below based on the image displacement amount (h) found through this operation:
 
 FNCLVL=h× 32/MAXDER  Equation 3
 
where ‘MAXDER’ represents an element whose value becomes smaller as the coincidence of the shapes of the two images becomes higher.
 
   The above calculation method of the reliability of the object distance information is mere illustrative, and another calculation method may be used. 
   In  FIG. 1 ,  117  denotes an AF operation switch that serves as a first operating member, and is operated or pressed when a photographer needs the AF. This switch  117  is configured to return to the original position when the manipulation is stopped. In other words, only when the switch  117  is pressed, a signal indicative of the manipulation of the switch is input into the microcomputer  115 . 
     118  denotes an AF/MF switch that serves as a second operating member, and is manipulated when a photographer selects the AF or manual focus (“MF”). The switch  118  is configured to remain at its manipulated position even when the operation is stopped. 
   Referring now to  FIGS. 2A to 6 , a description will be given of the AF control performed by the microcomputer  115 . This AF control is executed in accordance with a computer program stored in the microcomputer  115 . 
   Referring now to  FIGS. 2A and 2B , the overall AF control flow will be described. Each circled numeral is connected in  FIGS. 2A and 2B . 
   At Step  301 , the microcomputer  115  starts the process. 
   At Step  302 , the microcomputer  115  takes in the AF evaluation value and external ranging in-focus position. 
   Step  303  provides processes corresponding to inputs of the AF operation switch  117  and the AF/MF switch  118 . This input process will be described in detail with reference to  FIG. 5 . 
   Step  304  determines whether or not the AF mode is set in the process of Step  303 , and the procedure moves to Step  305  when the AF mode is set. When the AF mode is not set, the procedure returns to Step  302  without performing the AF control. 
   Step  305  determines whether the TV-AF mode is a minute-drive mode. When the minute-drive mode is set, the procedure moves to Step  306 , and otherwise the procedure moves to Step  304 . 
   Step  306  provides the TV-AF minute-drive mode to determine whether or not the in-focus state is reached and to find a direction to the in-focus state (referred to as an “in-focus direction” hereinafter) when the in-focus state has not yet been reached. A detailed operation will be described later with reference to  FIG. 3 . 
   Control over a minute-drive operation of the focus lens  105  used to determine the in-focus direction from a change of the AF evaluation value can also be referred to as an in-focus direction determination control. Control over a minute-drive operation of the focus lens  105  used to determine, from a change of the AF evaluation value, whether or not the in-focus state is reached can also be referred to as an in-focus confirmation control. 
   Step  307  determines whether or not the AF evaluation value is smaller than a predetermined threshold value. When it is smaller than the threshold value, the procedure move to Step  308 , and when it is greater the procedure moves to Step  310 . The threshold value may be determined with reference to the AF evaluation value at which the object image is too blurred to be recognized. 
   Step  308  determines an immediate transfer to the TV-AV climbing drive (in-focus position detection control) so as to avoid a deterioration of the AF&#39;s responsiveness, because the AF evaluation value is so small that it is difficult to detect the in-focus direction, and the direction determination requires a long time. The microcomputer  115  sets to the climbing direction from the current focus lens a direction that is likely to include the in-focus position, and transfers the procedure to Step  309 . For instance, the climbing direction is set to the near direction when the current focus lens position is located at the infinite side, and the climbing direction is set to the infinite direction when the current focus lens position is located at the near side. 
   At Step  309 , the procedure moves to the climbing-drive mode that provides a climbing-drive operation. 
   Step  310  determines whether or not the in-focus determination is completed at Step  306 . When the in-focus determination is completed, the procedure moves to Step  312  to provide the restart determination mode. When the in-focus determination has not yet been completed, the procedure moves to Step  311 . 
   Step  311  determines whether or not the in-focus direction determination is completed at Step  306 . When the in-focus direction determination is completed, the procedure moves to Step  310  to provide the climbing-drive mode. When the in-focus direction determination has not yet been completed, the procedure moves to Step  302 . 
   Step  312  stores the AF evaluation value at the in-focus position in a memory (not shown). 
   At Step  313 , the procedure moves to the restart determination mode. 
   Step  314  determines whether or not the climbing-drive mode. When the climbing-drive mode is set, the procedure moves to Step  315 , and otherwise the procedure moves to Step  326 . 
   Step  315  determines whether or not the focus lens  105  is moving to the external ranging in-focus position. If so, the procedure moves to Step  321 , and if not the procedure moves to Step  316 . 
   At Step  316 , the focus lens  105  is climb-driven at a predetermined speed. A detailed description of the climb drive will be described later with reference to  FIG. 4 . 
   Step  317  determines, during the climb drive at Step  316 , whether or not focusing is determined unavailable in accordance with a predetermined out-of-focus condition. When it is determined that the in-focus is unavailable, the procedure moves to Step  321 . One out-of-focus condition is that no in-focus position is specified irrespective of a movement of the focus lens  105  in the overall stroke or in a predetermined range in the overall stroke from the infinite end to the near end. 
   Step  318  determines whether or not the AF evaluation value exceeds a peak in the climbing drive in Step  316 . When the AF evaluation value exceeds the peak, the procedure moves to Step  319 , and when the AF evaluation value does not exceed the peak, the procedure returns to Step  302  to continue the climbing drive. 
   Step  319  returns the focus lens  105  to a position that provides a peak AF evaluation value (referred to as a “peak position” hereinafter). 
   At Step  320 , the procedure moves to a stop mode. 
   Step  321  moves the focus lens  105  to an external ranging in-focus position calculated based on the object distance information from the external ranging unit  116 . 
   Step  322  determines whether or not the focus lens  105  reaches the external ranging in-focus position. When the focus lens  105  reaches the external ranging in-focus position, the procedure moves to Step  323 , and when the focus lens  105  does not reach the external ranging in-focus position, the procedure returns to Step  302  to continue driving to the external ranging in-focus position. 
   At Step  323 , the procedure moves to the minute-drive mode. 
   Step  324  determines whether or not the focus lens  105  has reached the external ranging in-focus position in accordance with a manipulation of the AF operation switch  117 . When the focus lens  105  has reached the external ranging in-focus position, the procedure returns to Step  302  to provide the minute-drive mode. Otherwise, the procedure moves to Step  325 . 
   Step  325  sets a value smaller than a normal value to a threshold value used for Step  307  so that the process of Step  307  cannot enter the climbing-drive mode. This embodiment changes the TV-AF characteristic (threshold value) and again searches for the in-focus position after moving the focus lens  105  to the external ranging in-focus position when the in-focus position cannot be detected in the climbing drive. Thereby, highly precise focusing is available to an object that cannot be focused by the TV-AF. 
   Step  326  determines the existence of the stop mode. When the stop mode exists, the procedure moves to Step  327 , and otherwise the procedure moves to Step  330 . 
   Step  327  determines whether or not the focus lens  105  has returned to the peak position. When it is returned to the peak position, the procedure moves to Step  328 , and otherwise the procedure moves to Step  302  to continue returning action to the peak position. 
   Step  328  sets a normal value to a threshold value used for Step  307 . 
   At Step  329 , the procedure moves to the minute-drive mode. 
   Step  330  is executed in the restart determination mode. This Step  330  compares the AF evaluation value stored in Step  312  with the latest AF evaluation value, and determines whether a difference between them or a fluctuation of the AF evaluation value is greater than a predetermined value. When the fluctuation of the AF evaluation value is greater than the predetermined value, the procedure moves to Step  331  or the minute-drive mode. When the fluctuation of the AF evaluation value is smaller than the predetermined value, the procedure moves to Step  302 . 
   At Step  331 , the procedure moves to the minute-drive mode. 
   Referring now to  FIG. 3 , the minute-drive operation will be described.  FIG. 3  shows a relationship between a movement of the focus lens  105  and a change of the AF evaluation value in the minute-drive operation, where an abscissa axis denotes time, and an ordinate axis denotes a focus lens position. A vertical synchronizing signal of a video signal is shown above the chart. 
   AF evaluation value EV A  for charges (beveled eclipse) accumulated in the image-pickup element  106  during period A is taken in at time T A . AF evaluation value EV B  for charges accumulated in the image-pickup element  106  during period B is taken in at time T B . At time T C , the AF evaluation values EV A  and EV B  are compared with each other, and a driving (oscillatory) center of the minute driving is moved when EV B &gt;EV A  (i.e., driving amplitude=oscillation amplitude+center-moving amplitude). On the other hand, when EV A &gt;EV B , the oscillatory center is not moved (i.e., driving amplitude=oscillatory amplitude). The minute-drive operation thus detects a direction in which the AF evaluation value increases while moving the focus lens  105 , and a focus lens position (peak position) that maximizes the AF evaluation value. 
   Referring now to  FIG. 4 , a description will be given of the climbing-drive operation that quickly drives the focus lens  105  and detects the peak position of the AF evaluation value or its vicinity.  FIG. 4  shows a relationship between a movement of the focus lens  105  and a change of the AF evaluation value in the climbing-drive operation. In a movement of C, the AF evaluation value decreases beyond the peak, the existence of the peak position (in-focus position) can be confirmed, and the climbing-drive operation is terminated and moved to the minute-drive operation. On the other hand, a movement of D monotonically decreases with no peak, and a driving direction of the focus lens  105  can be determined erroneous. In this case, the driving direction is inversed and the climbing-drive operation continues. 
   Referring now to  FIG. 5 , a description will be given of an input process in Step  303 . 
   At Step  601 , the microcomputer  115  starts processing. 
   At Step  602 , the microcomputer  115  determines whether or not the AF operation switch  117  is manipulated. If the AF operation switch  117  is manipulated, the procedure moves to Step  603 , and otherwise the procedure moves to Step  616 . 
   At Step  603 , the AF mode is set. 
   Step  604  determines whether or not the AF operation switch  117  was manipulated before Step  602 . If it has not been manipulated, the procedure moves to the process subsequent to Step  605 . If the AF operation switch  117  was manipulated before Step  602 , the procedure moves to Step  617 . 
   Step  605  determines whether or not the external ranging in-focus position is calculated or whether the external ranging unit  116  has detected the object distance. When the external ranging in-focus position is calculated, the procedure moves to Step  606 , and otherwise the procedure moves to Step  612 . 
   Step  606  determines whether or not the reliability of the object distance information obtained by the above method is higher than a predetermined level (or first value). When the reliability is higher than the predetermined level, the procedure moves to Step  607 , and otherwise the procedure moves to Step  610 . 
   Step  607  starts moving the focus lens  105  to the external ranging in-focus position calculated based on the object distance having the high reliability. The focus lens  105  is moved to the external ranging in-focus position in response to the manipulation of the AF operation switch  117 , only when the external ranging in-focus position is calculated based on the object distance having high reliability. The external ranging in-focus position calculated based on the object distance having low reliability is likely to contain an error. The above configuration surely prevents a movement of the focus lens  105  to the possibly erroneous external ranging in-focus position. 
   Step  608  sets the climbing-drive mode. 
   Step  610  sets a direction of the calculated external ranging in-focus position to a driving direction of the focus lens  105  in the climb driving. This is because the direction of the in-focus position is reliable, even when the reliability of the object distance information is determined low in Step  606 , and the precision of the calculated external ranging in-focus position is low. 
   Step  611  moves the procedure to the climbing-drive mode. Thus, when the reliability of the object distance information is low, only the information of the direction of the in-focus position calculated based on the object distance information is utilized to determine the climbing-drive direction without conducting the minute-drive operation. 
   This configuration can expedite the TV-AF operation because no minute-drive operation is performed to determine the in-focus direction. In addition, in that case, the focus lens  105  is climb-driven in the external ranging in-focus position while the AF evaluation value is monitored. Therefore, a continuation of the climb driving in a wrong direction can be prevented even when the reliability of the object distance information is low. 
   Step  612  determines whether the AF evaluation value is smaller than the threshold value when the external ranging in-focus position is not calculated in Step  605 . The procedure moves to Step  613  when the AF evaluation value is smaller than the threshold value, and otherwise the procedure moves to Step  615 . 
   Step  613  determines an immediate transfer to the climbing-drive mode due to the same reason as Step  308 , because the AF evaluation value is small. In addition, a direction that is likely to include the in-focus position from the current focus lens position is set to the climbing direction, and the procedure moves to Step  614 . The threshold value used herein may be determined like the threshold value of Step  307 . A direction that is likely to include the in-focus position is as described in Step  308 . 
   At Step  614 , the procedure moves to the climbing-drive mode. 
   When the external ranging in-focus position is not calculated and when the AF evaluation value is smaller than the threshold value, the climbing-drive operation is performed from the current focus lens position to the direction that is likely to include the in-focus position, in response to a manipulation of the AF operation switch  117 . Thereby, a good TV-AF responsiveness can be maintained even when it is difficult to detect the in-focus direction from the AF evaluation value. 
   At Step  615 , the procedure moves to the minute-drive mode. 
   When the external ranging in-focus position is not calculated, and when the focus evaluation value is higher than the threshold value, the minute-drive operation detects the in-focus direction in response to the manipulation of the AF operation switch  117 . In this case, the in-focus direction can be surely detected because the direction that is likely to include the in-focus position is detected by using the AF evaluation value. 
   Step  616  determines whether the AF/MF switch  118  selects the AF or the MF. When it selects the AF, the procedure moves to Step  617  to set the AF mode. When it selects the MF, the procedure moves to Step  618  to set the MF mode. No AF operation is performed in the MF mode, unless the AF operation switch  117  is manipulated. On the contrary, this embodiment executes the AF operation when the AF operation switch  117  is manipulated no matter whether the AF/MF switch  118  selects the AF or MF. This enables a photographer to temporarily or suddenly use the AF without switching the AF/MF switch  118 . 
   As discussed, this embodiment can maintain highly responsive focus control (TV-AF and external ranging AF) as one advantage of the phase difference detection method, in response to a photographer&#39;s manipulation of AF operation switch  117 , realizing the focus control fit for the photographer&#39;s intension. The focus control is varied in accordance with the reliability of the object distance information and the state of the AF evaluation value when the AF operation switch  117  is manipulated. Therefore, focus control having the best responsiveness and precision is available according to the circumstances. 
   The above embodiment provides TV-AF focus control that uses the first information, such as the AF evaluation value, when the first operating member is not operated. When the first operating member is operated, focus control (such as focus control by the phase difference detection method) other than the TV-AF method is performed which uses the second information, such as the object distance and the phase difference. This configuration provides focus control fit for the user&#39;s intension. The TV-AF focus control that uses the second information may start in response to an operation of the first operating member, so as to expedite the TV-AF focus control. 
   The above embodiment discusses the hybrid AF that combines the external phase difference detection (external ranging) method with the TV-AF method, although the embodiment of the present invention may include an image-pickup apparatus that adopts the hybrid AF that combines the internal phase difference detection method and the TV-AF method. The internal phase difference detection method detects a phase difference between one or more pairs of images formed by the light from an object which has passed an image-pickup optical system, calculates a defocus amount of the image-pickup optical system based on the phase difference, and then calculates a driving amount and direction to move a focus lens to the in-focus position. In this case, the AF control can be performed similar to the above embodiment by replacing the external ranging in-focus position in the above embodiment with the in-focus position corresponding to the driving amount. 
   While the above embodiment discusses the AF operation that starts in response to the manipulation of the AF operation switch  117  irrespective of the state of the AF/MF switch  118 , the present invention allows the AF operation to start in response to the manipulation of the AF operation switch  117  only when the AF/MF switch  118  selects the AF or MF. 
   While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass al modifications, equivalent structures and functions. 
   This application claims a benefit of priority based on Japanese Patent Application No. 2006-201996, filed on Jul. 25, 2006, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.