Patent Publication Number: US-9411128-B2

Title: Automatic focusing apparatus with cyclic pattern determination

Description:
This application is a division of application Ser. No. 13/510,978, filed on May 21, 2012, which is a national stage entry of International Application No. PCT/JP2011/051152, filed Jan. 18, 2011. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an automatic focusing apparatus for picking up of an image of an object. 
     BACKGROUND ART 
     Conventionally, as automatic focusing (AF) technologies in image pickup apparatus such as cameras and video cameras, various proposals have been made. For example, there is proposed phase difference autofocus using a through the lens (TTL) method in which a separating unit is provided in an optical path in an imaging optical system, and a focusing state is detected using a separated beam to perform autofocus control. In addition, there is also proposed external ranging autofocus using a non-TTL method in which a beam which does not enter nor pass through the imaging optical system is used. Further, there is proposed image autofocus using so-called hill climbing method in which an image signal output from an image pickup element is used to compute a focus evaluating value. Further, there is proposed a hybrid autofocus system in which the image autofocus is combined with the phase difference autofocus or the external ranging autofocus. 
     In focus detecting apparatus using the TTL method such as the phase difference autofocus or the non-TTL method such as the external ranging autofocus, a phase difference is determined by performing correlation computation using an image signal output from the focus detecting apparatus. In this case, a true focusing point is determined using a degree of coincidence between two images as a correlated evaluating value. In general, a defocus amount with respect to a focusing proposed point is determined based on a phase difference with which the correlated evaluating value takes an extreme and maximum value. However, in a case where data obtained from the focus detecting apparatus has a cyclic pattern, multiple focusing proposed points that have substantially identical correlated evaluating values are computed when focus detecting computation is performed. Consequently, it has been difficult to obtain a true focusing target position. 
     Patent Literature 1 proposes a method in which, when an object having a cyclic pattern is detected, a point where a contrast value of data output from a phase difference sensor takes a maximum value is assumed to be a true focusing point, and individual focusing proposed points are searched for the true focusing point. In addition, in each of the hybrid autofocus systems of Patent Literatures 2, 3 and 4, there is proposed a method involving searching for the focusing point at which contrast takes a maximum value by using only the image autofocus for an object having the cyclic pattern. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent Application Laid-open No. 563-262611 
         PTL 2: Japanese Patent Application Laid-Open No. 2006-301150 
         PTL 3: Japanese Patent Application Laid-Open No. 2007-264299 
         PTL 4: Japanese Patent Application Laid-Open No. 2009-063921 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, each of the methods proposed in Patent Literatures 1, 2, 3 and 4 is a method involving searching for the final focusing point by using so-called hill climbing method using a contrast evaluating value, and it is therefore difficult to quickly achieve an in-focus condition. Further, in the case of the method of searching for the focusing point by using only the contrast evaluating value, when a focus adjusting unit is operated at high speed during the search, a sampling interval of the contrast evaluating values in an optical axis direction is increased, so that the true focusing point may be passed over. Consequently, in the case of shooting especially for moving images, it is highly possible that a person who picks up a moving image may feel unpleasant about the image picked up before achieving an in-focus state. 
     In view of the foregoing, an object of the present invention is to solve the above-mentioned problem, and to provide an automatic focusing apparatus having excellent usability by properly performing automatic focusing control on an object having a cyclic pattern. 
     Solution to Problem 
     In order to attain the above-mentioned object, according to the present invention, there is provided an automatic focusing apparatus including: an image pickup optical system including a focus lens unit; a focus position detecting unit for detecting a position of the focus lens unit; a focus driving unit for driving the focus lens unit; an image pickup unit for picking up an image of an object through use of a beam having passed through the image pickup optical system; a focus detecting unit for detecting focus information by a phase difference method through use of the beam from the object; a contrast acquiring unit for acquiring contrast evaluating value using an image pickup signal obtained by the image pickup unit; a focusing determining unit for determining whether or not an in-focus state is achieved based on the contrast evaluating value; a cyclic pattern determining unit for determining whether or not the object has a cyclic pattern based on focus information provided by the focusing detecting unit; a target position setting unit for setting a target position of the focus lens unit; and a focusing direction determining unit for determining a direction of an in-focus point, in which, when the cyclic pattern determining unit determines that the object has the cyclic pattern, the focusing direction determining unit determines the direction of the in-focus point, the target position setting unit sets the target position of the focus lens unit in the direction of the in-focus point, the focus driving unit drives the focus lens unit toward the target position, and the focusing determining unit determines whether or not an in-focus state is achieved. 
     Advantageous Effects of Invention 
     According to the present invention, the effect of automatic focusing with excellent usability for an object having a cyclic pattern can be obtained by properly setting automatic focusing operations. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a structural view of a system in a first embodiment of the present invention. 
         FIG. 2A  is a structural view of an autofocus sensor in the first embodiment. 
         FIG. 2B  is a view illustrating an example of a shot image in the first embodiment. 
         FIG. 3  is Flowchart  1  of processes in the first embodiment. 
         FIG. 4  is a view illustrating an example of an output value of a phase difference sensor in the first embodiment. 
         FIG. 5  is a view illustrating an example of a correlated evaluating value in the first embodiment. 
         FIG. 6  is Flowchart  2  of processes in the first embodiment. 
         FIG. 7  is Flowchart  3  of processes in the first embodiment. 
         FIG. 8  is Flowchart  4  of processes in the first embodiment. 
         FIG. 9  is a view illustrating an example of a focusing proposed point in the first embodiment. 
         FIG. 10  is Flowchart  5  of processes in the first embodiment. 
         FIG. 11  is a view illustrating examples of the focusing proposed point and a contrast evaluating value in the first embodiment. 
         FIG. 12  is a view illustrating change in focus in the first embodiment. 
         FIG. 13  is Flowchart  1  of processes in a second embodiment of the present invention. 
         FIG. 14  is Flowchart  2  of processes in the second embodiment. 
         FIG. 15  is a view illustrating examples of a focusing proposed point and a contrast evaluating value in the second embodiment. 
         FIG. 16  is a view illustrating change in focus in the second embodiment. 
         FIG. 17  is Flowchart  1  of processes in a third embodiment of the present invention. 
         FIG. 18  is Flowchart  2  of processes in the third embodiment. 
         FIG. 19  is a view illustrating examples of a focusing proposed point and a contrast evaluating value in the third embodiment. 
         FIG. 20  is a view illustrating change in focus in the third embodiment. 
         FIG. 21  is Flowchart  1  of processes in a fourth embodiment of the present invention. 
         FIG. 22  is Flowchart  2  of processes in the fourth embodiment. 
         FIG. 23A  is a view illustrating an example of a contrast evaluating value in the fourth embodiment. 
         FIG. 23B  is a view illustrating an example of the contrast evaluating value in the fourth embodiment. 
         FIG. 23C  is a view illustrating an example of the contrast evaluating value in the fourth embodiment. 
         FIG. 24  is a view illustrating examples of a focusing proposed point and the contrast evaluating value in the fourth embodiment. 
         FIG. 25  is a view illustrating change in focus in the fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention are described in detail hereinbelow based on the accompanying drawings. 
     First Embodiment 
       FIG. 1  illustrates a structure of an automatic focusing apparatus  100  in a first embodiment of the present invention. 
     The automatic focusing apparatus  100  includes a focus lens unit  111  constituting an image pickup optical system, and a focus motor  112  as a focus driving unit is connected to the focus lens unit  111 . The focus motor  112  is driven by a focus driver  113  to move the focus lens unit  111  in an optical axis direction. The position of the focus lens unit  111  is detected by a focus position detecting unit  114 . 
     On an image plane side of the focus lens unit  111 , a half mirror  121  is disposed. A beam having entered the image pickup optical system passes through the focus lens unit  111 , and is divided into a beam passing through the half mirror  121  and a beam reflected by the half mirror  121 . The beam having passed through the half mirror  121  enters an image pickup element  140 . The image pickup element  140  is a charge storage type image sensor, and is constituted by a CMOS sensor or a CCD sensor. The beam reflected on the half mirror  121  enters a focus detecting unit  122  disposed at a position conjugate with the image pickup element  140 . 
     The focus detecting unit  122  includes multiple pairs of secondary imaging lenses (not shown), and an autofocus sensor as a phase difference sensor (not shown). Multiple area sensors are provided in the autofocus sensor. The beam having passed through the half mirror  121  is divided into two and forms a pair of object images (hereinafter, referred to as two images) on each of the multiple area sensors by each of the multiple pairs of secondary imaging lenses. Each of the multiple area sensors photoelectrically converts the two images, and outputs two image signals. From the two image signals, a phase difference according to a focus state of the automatic focusing apparatus  100  can be obtained. 
     When the automatic focusing apparatus  100  is in focus for a particular object at a specific distance, a phase difference corresponding to an interval between the two images indicates a specific value. When the focusing of the automatic focusing apparatus  100  is achieved on the side closer to the image plane with respect to the object, i.e., in the case of so-called front focus, the phase difference is smaller than the specific value. On the other hand, when the focusing thereof is achieved on the side farther from the image plane with respect to the object, i.e., in the case of so-called rear focus, the phase difference is larger than the specific value. In this manner, the focus detecting unit  122  has a function of detecting the phase difference between object images formed by the light entering the automatic focusing apparatus  100 . 
     A CPU  130  includes a phase difference focus computing unit  131 , a contrast focus computing unit (contrast acquiring unit)  132 , a defocus amount computing unit  133 , and a lens controlling unit  134 . The two image signals output from the focus detecting unit  122  are input to the phase difference focus computing unit  131 . In addition, an image pickup signal output from the image pickup element  140  is converted to an image signal by an image processing unit  141 , and the image signal is input to the contrast focus computing unit  132 . In this embodiment, a description is given assuming an update period of the image signal to be 16 milliseconds. 
     The phase difference focus computing unit  131  performs correlative computation on the two image signals output from the focus detecting unit  122  to compute the phase difference between the image signals. The degree of coincidence between two images is used as a correlated evaluating value. The phase differences with which the correlated evaluating values take extreme values are set as focusing proposed points. Further, among the individual focusing proposed points, the point at which the correlated evaluating value takes a maximum value is set as the most promising focusing proposed point. 
     The contrast focus computing unit  132  obtains the image signal output from the image processing unit  141 , and extracts a high frequency component from the image signal. Subsequently, the contrast focus computing unit  132  generates a contrast evaluating value indicating a contrast state of the object image from the high frequency component. The image signal output from the image processing unit  141  is periodically updated. The contrast focus computing unit  132  generates the contrast evaluating value in synchronization with the update period of the image signal. Then, the contrast focus computing unit  132  determines that the point at which the contrast evaluating value takes a maximum value is the focusing point. 
     The defocus amount computing unit  133  computes a defocus amount of the focus lens unit  111  based on the computation results of the phase difference focus computing unit  131  and the contrast focus computing unit  132 . 
     Thus, multiple defocus amounts are computed using the phase difference sensor provided in the focus detecting unit  122 . The computed defocus amounts are input to the lens controlling unit  134 . The lens controlling unit  134  obtains the position of the focus lens unit  111  using the focus position detecting unit  114 . Subsequently, the lens controlling unit  134  drives the focus lens unit  111  to a target position according to the defocus amounts computed by the defocus amount computing unit  133  (target position setting unit). At this point, the lens controlling unit  134  drives the focus motor  112  via the focus driver  113  to move the focus lens unit  111  so that the focus lens unit  111  is moved to the computed target position in the optical axis direction. In this manner, automatic focusing is performed. 
     Herein,  FIG. 2A  illustrates an example of focus detecting areas in an image taking screen. The individual focus detecting areas  501  to  527  are illustrated in  FIG. 2A .  FIG. 2A  illustrates an example in which 21 in total focus detecting areas are included with disposed seven focus detecting areas laterally arranged in each of an upper portion, a middle portion, and a lower portion of a photographing range, respectively. The focus detecting areas  501  to  507  are provided in the upper portion in order from the left side, the focus detecting areas  511  to  517  are provided in the middle portion in order from the left side, and the focus detecting areas  521  to  527  are provided in the lower portion in order from the left side. 
     The defocus amount computing unit  133  stores and retains positions (coordinates) of multiple focus detecting areas preset in the image taking range (image acquiring screen) in which an image can be taken, and shapes (sizes) of the focus detecting areas. By changing the settings, the positions of the focus detecting areas, the sizes thereof, and the like can be changed. In this embodiment, it is assumed that the focus detecting areas are selected by using a switch  201  of  FIG. 1 . 
       FIG. 2B  illustrates a shot image in which an object is photographed with the focus detecting area  514  illustrated in  FIG. 2A  being selected. As illustrated in  FIG. 2B , the object has a so-called stripe pattern and hence a cyclic pattern. In the first embodiment, an example in which focusing on an object having the cyclic pattern is performed in an image taking composition illustrated in  FIG. 2B  is described. 
       FIG. 3  is a flowchart illustrating a flow of automatic focusing processes in the automatic focusing apparatus  100 . The CPU  130  controls those processes according to a computer program stored in a memory (not shown). 
     When the power of the automatic focusing apparatus  100  is turned on, the processes of the CPU  130  are executed from Step S 101 . In Step S 101 , the lens controlling unit  134  obtains a position F( 0 ) of the focus lens unit  111  via the focus position detecting unit  114 . 
     Next, the CPU  130  proceeds to Step S 102  to select a focus detecting area selected by the switch  201 , and activate the phase difference sensor in the focus detecting unit  122 . Subsequently, the CPU  130  proceeds to Step S 103 . 
     In Step S 103 , the phase difference focus computing unit  131  obtains two image signals from the focus detecting unit  122 , and computes the phase difference in the focus detecting area  514  selected by the switch  201 .  FIGS. 4 and 5  illustrate examples of the two image signals, and the phase difference and the correlated evaluating value as computed focus information during the process described above, respectively. The object has the cyclic pattern as described above, and hence waveforms illustrated in  FIG. 4  are obtained from image data obtained from the focus detecting area  514 . In this case, the correlated evaluating values indicating the degree of coincidence between two images of each phase difference can be plotted as illustrated in  FIG. 5 . As illustrated in  FIG. 5 , focusing proposed points C( 1 ) to C( 5 ) each having the phase difference and its correlated evaluating value as parameters are obtained. The number of focusing proposed points and an index of each focusing proposed point are stored. 
     When the object has no cyclic pattern, differences among the correlated evaluating values at the respective individual focusing proposed points are produced, and hence the true focusing proposed point can be selected. However, the characteristic of the case where the object has the cyclic pattern is that the individual correlated evaluating values take substantially equal values, as illustrated in  FIG. 5 . Accordingly, even when C( 3 ) is a true focusing point, the correlated evaluating value of C( 3 ) is substantially equal to other correlated evaluating values, and hence it is difficult to determine which one of C( 1 ) to C( 5 ) is the true focusing proposed point. 
     The description returns to the flowchart of  FIG. 3 . Next, the process flow proceeds to Step S 120  in which the phase difference focus computing unit  131  (cyclic pattern determining unit) determines whether or not the object has the cyclic pattern. Herein, the description is given by taking, as an example, a method in which it is determined that the cyclic pattern is present when the difference among the respective correlated evaluating values of the above-mentioned focusing proposed points C( 1 ) to C( 5 ) fall within a predetermined range. 
       FIG. 6  illustrates a flowchart of a subroutine indicating an example of the cyclic pattern determination. First, in Step S 171 , it is determined whether or not the number of focusing proposed points computed in Step S 103  is 2 or more. When the number of focusing proposed points is 2 or more, the process flow proceeds to Step S 172 , while when the number thereof is less than 2, the process flow proceeds to Step S 177 . In Step S 172  and Step S 173 , the minimum value and the maximum value of the individual correlated evaluating values are searched for and stored. Next, the process flow proceeds to Step S 174  in which the difference between the minimum and maximum values of the correlated evaluating values obtained in Steps S 172  and S 173  is calculated, and the difference is stored as a correlated evaluating value range. Subsequently, the process flow proceeds to Step S 175  in which the correlated evaluating value range is compared with a predetermined threshold value β. In Step S 175 , in a case where the correlated evaluating value range is less than the threshold value β, the result is determined to be true, and the process flow proceeds to Step S 176 . When the evaluation result is false in Step S 175 , the process flow proceeds to Step S 177 . In Step S 176 , the result that the cyclic pattern is present is stored, and the subroutine for the cyclic pattern determination is ended. In Step S 177 , the result that a normal pattern is present is stored, and the subroutine for the cyclic pattern determination is ended. Note that, β is an arbitrary value, and a predetermined value may be written into a program for β in advance, or a structure may be adopted in which specification and selection of a value for β can be externally performed by providing a volume or a switch (not shown). 
     The description returns to the flowchart of  FIG. 3 . As the result of the determination in Step S 120 , when it is determined that the cyclic pattern is present, the process flow proceeds to Step S 121 . In Step S 120 , when it is determined that the cyclic pattern is not present, the process flow proceeds to Step S 150 . 
     In Step S 121 , a focusing direction determination is performed. Herein, the direction determination is performed by taking a flowchart of  FIG. 7  as an example. First, in Step S 181 , it is determined whether or not the position F ( 0 ) of the focus lens unit  111  detected in Step S 101  by the lens controlling unit  134  is located on an infinite side with respect to an entire focus area. When the determination result in Step S 181  is true, i.e., when the position F( 0 ) is located on the infinite side, the focusing direction is set to a close side in Step S 182 , and the process is ended. On the other hand, when the determination result in Step S 181  is false, i.e., when the position F( 0 ) is located on the close side, the focusing direction is set to the infinite direction in Step S 183 , and the process is ended. For example, the position F ( 0 ) of the focus lens unit is located further on the infinite side than a middle point in a movable range, the focusing direction may be set to the close side, while when the position F( 0 ) thereof is located further on the close side than the middle point in the movable range, the focusing direction may be set to the infinite direction. 
     The description returns to the flowchart of  FIG. 3 . Next, the process flow proceeds to Step S 122  in which the defocus amount computing unit  133  sets the closest focusing proposed point among the focusing proposed points corresponding to the focusing direction determined in Step S 121  in a variable i. 
       FIG. 8  illustrates a subroutine in Step S 122 . First, in Step S 191 , the focusing direction determined in Step S 121  is referred to. When the focusing direction is the infinite direction, the process flow proceeds to Step S 192 , while when the focusing direction is the close side, the process flow proceeds to Step S 196 . In Step S 192 , a value  1  is set to an index variable j, and the process flow proceeds to Step S 194 . In Step S 194 , the defocus amount computing unit  133  computes a focusing proposed position F (j) of the focus lens unit  111  corresponding to a focusing proposed point C(j). Subsequently, the positional relation between F( 0 ) and F(j) is determined. When F( 0 ) is closer than F(j), i.e., when the determination result is true, the process flow proceeds to Step S 195 . On the other hand, when the determination result in Step S 194  is false, the process flow proceeds to Step S 193 . In Step S 193 , the index variable j is incremented. Then the processes are executed again from Step S 194 . In Step S 196 , the number of focusing proposed points is set in the index variable j. That is, an index corresponding to the focusing proposed point having the last index among the focusing proposed points computed in Step S 103  of  FIG. 3  is set to the variable j. Subsequently, the process flow proceeds to Step S 197  in which, similarly to Step S 194 , F(j) is computed, and the positional relation between F( 0 ) and F(j) is determined. When F( 0 ) is located farther than F(j), i.e., when the determination result is true, the process flow proceeds to Step S 195 , while when the determination result is false, the process flow proceeds to Step S 198 . In Step S 198 , the index variable j is decremented, and the processes are executed again from Step S 197 . In Step S 195 , the index variable j is set to the variable i as a neighbor focusing proposed point, and the subroutine is ended. 
     Herein,  FIG. 9  illustrates each focusing proposed point C(i) and each position F(i) of the focus lens unit corresponding to C(i). For example, as illustrated in  FIG. 9 , when the position F( 0 ) of the focus lens unit  111  detected in Step S 101  is located at the position on the close side, the focusing direction determination in Step S 121  indicates the focusing direction being the infinite direction. Further, in Step S 122 , the index of the focusing proposed point closest to F( 0 ) is 1, and a value  1  is set to the variable i. 
     Next, in Step S 123 , the defocus amount computing unit  133  computes the defocus amount and a driving speed of the focus lens unit  111 , and computes the focusing proposed position F(i) of the focus lens unit  111  corresponding to the focusing proposed point C(i) as a target position. Each F(i) corresponding to each C(i) has a relation as illustrated in  FIG. 9 . Details of a method of determining the defocus amount and the driving speed are described later. Next, the process flow proceeds to Step S 124  in which the lens controlling unit  134  drives the focus lens unit  111  to the focusing proposed position F(i) at the above-described driving speed using the focus driver  113  and the focus motor  112 . Thereafter, in Step S 125 , the contrast focus computing unit  132  obtains the image signal from the image processing unit  141 , and computes the high frequency component and a contrast evaluating value V(i) of an area corresponding to the focus detecting area selected in Step S 102 . 
     Subsequently, the process flow proceeds to Step S 130  in which it is determined whether or not the contrast evaluating value V(i) obtained in Step S 125  is larger than a predetermined threshold value α. When V(i) is larger than the threshold value α, it is determined that an in-focus condition is achieved, and the process flow returns to Step S 101 , and the processes are executed again. On the other hand, when V(i) is equal to or smaller than the threshold value α, it is determined that an in-focus condition has not been achieved, and the process flow proceeds to Step S 140 . Note that, α is an arbitrary value, and a predetermined value may be written into a program for α in advance, or a structure may also be adopted in which specification and selection of a value for α can be externally performed by providing a volume or switch (not shown). A focusing determination method in Step S 130  is described later. 
     In Step S 140 , it is determined whether or not the focusing determinations has been carried out for a number of times that matches the number of focusing proposed points corresponding to the focusing direction determined in Step S 121 . When the determination result in Step S 140  is true, the processes are executed again from Step S 101 . When the determination result in Step S 140  is false, the process flow proceeds to Step S 141  in which the next focusing proposed point corresponding to the focusing direction determined in Step S 121  is set in the variable i. That is, the focusing proposed position that is located further in the focusing direction than the position of the current focus lens unit  111  and is closest to the current focus lens unit  111  is set as the target position of the focus lens unit. Then the processes are executed again from Step S 123 . 
     In Step S 150 , normal hybrid automatic focusing processes in a case where the object has no cyclic pattern are executed. Automatic focusing using a hybrid method of a phase difference method and a contrast method is well-known, and hence a flowchart of a subroutine is illustrated in  FIG. 10  as a simple example. First, in Step S 151 , among the focusing proposed points computed by the phase difference focus computing unit  131 , the focusing proposed point having the largest correlated evaluating value is selected. Subsequently, the target position of the focus lens unit  111  is computed by the defocus amount computing unit  133 . Next, in Step S 152 , the lens controlling unit  134  drives the focus lens unit  111  using the focus driver  113  and the focus motor  112 . Subsequently, in Step S 153 , the contrast focus computing unit  132  takes the image signal from the image processing unit  141 , and computes the contrast evaluating value. Then, in Step S 154 , the focusing determination is performed similarly to Steps S 110  and S 130 . When an in-focus condition is achieved, the present subroutine is ended. When an in-focus condition is not achieved, the process flow proceeds to Step S 155 . In Step S 155 , the defocus amount for performing so-called hill climbing determination using the contrast evaluating value is computed. Subsequently, the processes are repeatedly executed from Step S 152  until an in-focus condition is achieved. 
     Herein, the process from the computation of the defocus amount and the driving speed to the determination of the focus condition when the determination result is true in Step S 120  of the flowchart illustrated in  FIG. 3 , i.e., when it is determined that the cyclic pattern is present, is described.  FIG. 11  illustrates the process until an in-focus state is obtained when this embodiment is applied in the case where the initial position F( 0 ) of the focus lens unit  111  is positioned on the close side. The horizontal axis of  FIG. 11  indicates the focusing proposed point C(i) computed by the phase difference focus computing unit  131 , and the focusing proposed position F(i) of the focus lens unit  111  corresponding to each C(i). The vertical axis of  FIG. 11  indicates the correlated evaluating value of the focusing proposed point C(i) based on the phase difference, and the contrast evaluating value V(i) computed by the contrast focus computing unit  132 . F( 0 ) of  FIG. 11  denotes the position of the focus lens unit  111  detected by the lens controlling unit  134  in Step S 101 . When Step S 123  is executed, in a case where i=1 is assumed to be satisfied in Step S 122 , the target position of the focus lens unit  111  is set at F( 1 ). In addition, the lens controlling unit  134  determines the driving speed of the focus lens unit  111  such that the image output from the image processing unit  141  is updated when the focus lens unit  111  reaches the position F( 1 ), and drives the focus lens unit  111  in Step S 124 . As described above, when the update period of the image output from the image processing unit  141  is assumed to be 16 milliseconds, the driving is performed such that Step S 125  is executed after a lapse of an integral multiple of 16 milliseconds to obtain the contrast evaluating value V( 1 ). Then the focusing determination is performed based on the contrast evaluating value V( 1 ) in Step S 130 . The contrast evaluating value V( 1 ) is smaller than a, and hence F( 2 ) as the next focusing proposed position is set as the target position in Steps S 140  and S 141 , and the same processes are executed from Step S 123 . When i=3 is satisfied, the constant evaluating value V( 3 ) is larger than a, so that it is determined that focusing is achieved in Step S 130 , and the process is ended. 
       FIG. 12  illustrates the locus of the focus lens unit  111 . In  FIG. 12 , the horizontal axis indicates time, while the vertical axis indicates the position of the focus lens unit  111 . As illustrated in  FIG. 12 , from time T( 0 ) to time T( 3 ), the focus lens unit  111  is driven from the position F( 0 ) to the position F( 3 ), and the contrast evaluating values V( 0 ) to V( 3 ) are obtained. When it is determined that an in-focus condition is not achieved at a given focusing proposed point, the focus lens unit  111  can be immediately driven to the next focusing proposed point without reducing the driving speed of the focus lens unit  111  at the given focusing proposed point. In addition, according to the defocus amount (focusing evaluating value) at each of the focusing proposed points, the driving speed of the focus lens unit  111  is variable. That is, it is preferred to set the driving speed of the focus lens unit  111  faster as the defocus amount is larger (the focusing proposed point is farther from the in-focus position). 
     Thus, in this embodiment, in synchronization with the image update period of the image processing unit  141 , the focus lens unit  111  is driven to the focusing proposed position F(i) (focusing proposed point C(i)) while controlling the position and the velocity of the focus lens unit  111 , whereby contrast evaluating can be performed only on a focusing proposed point neighborhood. That is, it is not necessary to perform the contrast evaluation on areas between the individual focusing proposed points, and hence it is not necessary to reduce the driving speed of the focus lens unit in order to perform the contrast evaluation, so that time required to reach the true focusing point can be shortened. Consequently, the speed of the automatic focusing processes on the object having the cyclic pattern can be increased on comparison with conventional automatic focusing processes. Further, by setting the threshold value α, it is not necessary to search all focusing proposed points, so that focusing can be achieved at high speed. 
     Note that, the method of the focusing direction determination in this embodiment may adopt methods other than the method illustrated in  FIG. 7 . For example, the focusing direction may also be determined from the relation between the initial position F( 0 ) of the focus lens unit  111  and the set of the focusing proposed positions F(i). 
     Second Embodiment 
     In a case where the phase difference of the object having the cyclic pattern is computed, the phase difference interval between the focusing proposed points is two pixels or more in principle on an assumption that a pixel of the phase difference sensor is used as a unit. In addition, sensitivity differs according to the position of the focus lens unit, and hence the defocus amount differs for each area between the focusing proposed points, as illustrated in  FIG. 12 . Therefore, in a case where the defocus amount is large, even when the focus lens unit is driven at a maximum possible driving speed, there is a possibility that the image update period of the image processing unit  141  arrives before the focus lens unit is driven to the next focusing proposed point. That is, in some cases, it is difficult to perform the contrast evaluation at the position of the focus lens unit corresponding to the focusing proposed point. 
     With this being the situation, the utilization of the contrast evaluating value of the image updated in an area other than the focusing proposed point allows a determination of whether or not the neighbor focusing proposed point is a true focusing point. 
     In this embodiment, a method for automatic focusing suitable for such situation is described. 
     The structure of the automatic focusing apparatus, the structure of the autofocus sensor, and the arrangement of the focus detecting areas in a second embodiment are the same as those of  FIGS. 1 and 2A  in the first embodiment, and hence descriptions thereof are omitted. A description is given referring to  FIGS. 13 to 16  by taking the image taking scene of  FIG. 2B  as an example, similarly to the first embodiment. 
       FIG. 13  is a flowchart illustrating the flow of automatic focusing processes in the automatic focusing apparatus  100 . The CPU  130  controls those processes according to a computer program stored in the memory (not shown). 
     In Steps S 101  to S 103  of  FIG. 13 , similarly to the first embodiment, the position F( 0 ) of the focus lens unit  111  is detected. In addition, in the focus detecting unit  122 , the phase difference sensor selected by the switch  201  is activated. Next, the phase difference and the focusing proposed points of the focus detecting area  514  selected by the switch  201  are computed. 
     In Step S 120 , similarly to the first embodiment, the cyclic pattern determination is performed. When it is determined that the object has the cyclic pattern, the process flow proceeds to Step S 121 , while when it is determined that the object has no cyclic pattern, the process flow proceeds to Step S 150 . In Step S 150 , similarly to the first embodiment, the normal hybrid autofocus processes are performed, and the processes are repeated from Step S 101 . In Step S 121 , the determination of the focusing direction is performed, similarly to the first embodiment. 
     Subsequently, in Step S 210 , the defocus amount computing unit  133  performs the computation of the defocus amount.  FIG. 14  illustrates a subroutine in Step  210 . First, in Step S 211 , the lens controlling unit  134  detects the position of the focus lens unit  111 . Next, in Step S 212 , an in-focus neighborhood determination is performed using the contrast evaluating value. When the determination result indicates that the present focus position is in the neighborhood of the in-focus position, the process flow proceeds to Step S 122 , while when the determination result does not indicate that the present focus position is in the neighborhood of the in-focus position, the process flow proceeds to Step S 214 . Details of a determination method in Step S 212  are described later. 
     In Step S 122 , similarly to the first embodiment, a neighbor focusing proposed point i relative to the position of the focus lens unit  111  detected in Step S 211  is set. Next, the process flow proceeds to Step S 213  in which a neighbor focusing proposed position F(i) is set as the target position of the focus lens unit  111 , and the subroutine is ended. Further, in Step S 214 , a focusing direction end determined in Step S 121  is set as the target position, and the subroutine is ended. The focusing direction end refers to a limit of the position of the focus lens unit corresponding to the detected focus direction, i.e., the end thereof. 
     The description returns to the flowchart of  FIG. 13 . Next, the process flow proceeds to Step S 124  in which the focus lens unit  111  is driven to the target position, similarly to the first embodiment. Subsequently, the process flow proceeds to Step S 211  in which the previously computed contrast evaluating value is stored. The process flow proceeds to Step S 125  in which the contrast evaluating value is computed, similarly to the first embodiment. Further, the process flow proceeds to Step S 130  in which it is determined whether or not an in-focus condition is achieved, similarly to the first embodiment. When an in-focus condition is achieved, processes are executed again from Step S 101 , while when an in-focus condition is not achieved, the process flow returns to Step S 210 . The processes described above are repeatedly executed. 
     Herein, the process until an in-focus condition is achieved and the determination method in Step S 212  of  FIG. 14  when the flowchart of  FIG. 13  is executed are described with reference to  FIGS. 15 and 16 . Similarly to  FIG. 11  described in the first embodiment, in  FIG. 15 , the horizontal axis indicates the focusing proposed point C(i) and the focusing proposed position F(i) of the focus lens unit  111 . In addition, the vertical axis of  FIG. 15  similarly indicates the correlated evaluating value of the focusing proposed point C(i) and the contrast evaluating value V(i) thereof. In  FIG. 16 , the horizontal axis indicates time, and the vertical axis indicates the position of the focus lens unit  111 , similarly to  FIG. 12  described in the first embodiment. 
     Herein, at time T( 0 ) of  FIG. 16 , it is assumed that the position F( 0 ) of the focus lens unit  111  detected in Step S 101  is located at positions illustrated in  FIGS. 15 and 16 . In addition, the true focusing position is assumed to be F( 3 ). In this case, in Step S 121 , as the result of the focusing direction determination, it is determined that the focusing direction is the infinite direction. In Step S 212  of  FIG. 14  that is the subroutine in the next Step S 210 , it is determined whether or not the current position is in the neighborhood of the in-focus position by using the contrast evaluating value. In this process, the obtained latest contrast evaluating value V(i) is compared with the previous contrast evaluating value stored in Step S 211 . When the latest contrast evaluating value V(i) is larger than the previous contrast evaluating value, it is determined that the current position is in the neighborhood of the in-focus position. When the latest contrast evaluating value V(i) is the previous contrast evaluating value or less, it is determined that the current position is not in the neighborhood of the in-focus position. When i=0 is satisfied, the process flow proceeds to Step S 214  in which the target position is set at an infinite side end, and the defocus amount computation is ended. Next, in Step S 124 , the focus lens unit  111  is driven toward the infinite side. Subsequently, at time T( 1 ) of FIG.  16 , in Step S 125 , a contrast evaluating value V( 1 ) is computed. 
     Then, the focusing determination is performed in Step S 130 . As illustrated in  FIG. 15 , (the contrast evaluating value V( 1 ))&lt;(the threshold value α) is satisfied, and hence the process flow proceeds to Step S 210 . In the same manner, Steps S 210  to S 130  of  FIG. 13  are repeatedly executed. Then, when i=2 is satisfied, in Step S 212  of  FIG. 14 , the result that V( 2 )&gt;V( 1 ) is satisfied is obtained, and the process flow proceeds to Step S 213 . In Step S 213 , a neighbor focusing proposed position F(i) relative to the position of the focus lens unit  111  where V( 2 ) is obtained, i.e., the position of the focus lens unit  111  detected in Step S 211  is searched for. In other words, the focusing proposed position F(i) that is located further in the focusing direction than the position of the focus lens unit  111 , and is closest to the position of the focus lens unit  111  is searched for, and set as the target position. From  FIG. 15 , i=3 is obtained, and F( 3 ) is set as the target position. The process flow proceeds to Step S 124  of  FIG. 13  in which the focus lens unit  111  is driven to the target position F( 3 ). In Step S 124 , in order to quickly achieve an in-focus state, it is assumed that the focus lens unit  111  is driven to the target position F( 3 ) asynchronously with the image update period. Subsequently, the process flow proceeds to Step S 125  in which a contrast evaluating value V( 3 ) is obtained. Then, in the focusing determination in Step S 130 , (the contrast evaluating value V( 3 ))&gt;(the threshold value α) is satisfied, and it is determined that focusing is achieved. Herein, as illustrated in  FIG. 16 , when attention is paid to the locus of the focus lens unit  111  until focusing is achieved, it can be seen that the focus lens unit  111  is driven at a constant speed until an in-focus condition is achieved. Note that, the driving speed of the focus lens unit  111  from a position F( 2 ) to the position F( 3 ) may also be determined in synchronization with the update period of the image obtained from the image processing unit  141 , as described in the first embodiment. 
     Thus, by utilizing the contrast evaluating value of the image updated in the area other than the focusing proposed point, it is determined whether or not the previous or subsequent focusing proposed point is the true focusing point, and the focus lens unit  111  can be thereby driven quickly to the in-focus position. 
     Third Embodiment 
     In the first and second embodiments, the case where the initial position of the focus lens unit  111  is on the close side is described. In those embodiments, the set of focusing proposed points is present in one direction with respect to the initial position F( 0 ) of the focus lens unit  111 , and hence the direction of the in-focus position can be uniquely determined. On the other hand, when the initial position of the focus lens unit  111  is located within the range of the focusing proposed points, it is difficult to uniquely determine the direction of the in-focus position. With this being the situation, by obtaining the contrast evaluating value in the neighborhood of the initial position F( 0 ), the direction determination of the in-focus position can be performed. After the direction of the in-focus potion is determined, similarly to the first and second embodiments, focusing can be quickly achieved by using the contrast evaluating value at the focusing proposed point. In this embodiment, a method for automatic focusing suitable for such situation is described. 
     The structure of the automatic focusing apparatus, the structure of the autofocus sensor, and the arrangement of the focus detecting areas in a third embodiment are the same as those of  FIGS. 1 and 2A  in the first embodiment, and hence descriptions thereof are omitted. A description is given referring to  FIGS. 17 to 20  by the image taking scene of  FIG. 2B  as an example, similarly to the first embodiment. 
       FIG. 17  is a flowchart illustrating the flow of automatic focusing processes in the automatic focusing apparatus  100 . The CPU  130  controls those processes according to a computer program stored in the memory (not shown). 
     The Steps S 101  to S 103  of  FIG. 17  are the same as those in the first and second embodiments, and hence descriptions thereof are omitted. After Step S 103 , the process flow proceeds to Step S 120  in which the cyclic pattern determination is performed. When the determination result in Step S 120  is true, i.e., when it is determined that the cyclic pattern is present, the process flow proceeds to Step  310 . When the determination result in Step S 120  is false, i.e., when the object is a normal object, the process flow proceeds to Step S 150 . The same processes as those in the first embodiment are performed in Step S 150 , and hence a description thereof is omitted. 
     In Step S 310 , the focusing direction determination is performed.  FIG. 18  illustrates a subroutine in Step S 310 . First, in Step S 311 , the contrast focus computing unit  132  computes a contrast evaluating value V( 0 ). Next, the process flow proceeds to Step S 312  in which the defocus amount computing unit  133  computes the defocus amount for driving the focus lens by a predetermined amount. The defocus amount is an arbitrary amount, and the defocus amount may be written into a program or the like in advance, or may be computed based on optical conditions of the automatic focusing apparatus. Then, the focus lens unit  111  is driven in a forward direction by the lens controlling unit  134 . In this embodiment, as an example of the forward direction, the focus lens unit  111  is driven toward the close side. Next, the process flow proceeds to Step S 313  in which the contrast focus computing unit  132  computes a contrast evaluating value V( 0 )′. Subsequently, the process flow proceeds to Step S 314  in which the contrast evaluating values V( 0 ) and V( 0 )′ are compared with each other. When V( 0 )′&gt;V( 0 ) is satisfied, the process flow proceeds to Step S 315 , while when V( 0 )′≦V( 0 ) is satisfied, the process flow proceeds to Step S 316 . In this embodiment, in Step S 315 , a focusing direction  1  corresponds to the forward direction, i.e., the close side and, in Step S 316 , a focusing direction  2  corresponds to an opposite direction, i.e., the infinite direction. The focusing direction is determined in this manner, and the subroutine for the focusing direction determination is ended. Subsequently, the process flow proceeds to Step S 122  of the flowchart of  FIG. 17 . 
     The Steps S 122 , S 123 , S 124 , S 125 , S 130 , S 140 , and S 141  are the same as those in the first embodiment, and hence descriptions thereof are omitted. Those processes described above are repeatedly executed. 
     Herein, the process until an in-focus condition is achieved and the process of focusing direction determination in the flowchart of  FIG. 18  when the flowchart of  FIG. 17  is executed are described with reference to  FIGS. 19 and 20 . Similarly to  FIG. 11  described in the first embodiment, in  FIG. 19 , the horizontal axis indicates the focusing proposed point C(i) and the focusing proposed position F(i) of the focus lens unit  111 . In addition, the vertical axis of  FIG. 19  similarly indicates the correlated evaluating value of the focusing proposed point C(i) and the contrast evaluating value V(i) thereof. In  FIG. 20 , the horizontal axis indicates time, and the vertical axis indicates the position of the focus lens unit  111 , similarly to  FIG. 12  described in the first embodiment. 
     Herein, it is assumed that the position F( 0 ) of the focus lens unit  111  detected in Step S 101  is located at positions illustrated in  FIG. 19 . In addition, the true in-focus position is assumed to be F( 3 ). In Step S 312  of  FIG. 18 , when it is assumed that the focus lens is driven in the forward direction, i.e., toward the close side, the contrast evaluating value V( 0 )′ obtained in Step S 313  is obtained at a position as illustrated in  FIG. 19 . Next, in the determination of the focusing direction in Step S 314 , as illustrated in  FIGS. 19 and 20 , V( 0 )&gt;V( 0 )′ is satisfied, and hence the process flow proceeds to Step S 316  in which it is determined that the focusing direction corresponds to the opposite direction, i.e., the infinite direction. Then, the subroutine for the focusing direction determination is ended. Next, when the process flow proceeds to Step S 122  in which the process is executed similarly to the first embodiment, the index of the focusing proposed point closest to F( 0 ) is 3, and a value  3  is set in the variable i. In addition, in Steps S 123  and S 124 , the focus lens unit  111  is driven to F( 3 ), and a contrast evaluating value V( 3 ) in Step S 125  is obtained. Subsequently, in the focusing determination in Step S 130 , (the contrast evaluating value V( 3 ))&gt;(the threshold value α) is satisfied, and hence it is determined that focusing is achieved, and the flowchart of  FIG. 17  is ended. 
     Thus, in this embodiment, by obtaining the contrast evaluating value in the neighborhood of the initial position F( 0 ), the direction determination of the focusing point is performed, and by performing the focusing direction determination, the object having the cyclic pattern can be quickly focused on. 
     In this embodiment, although the description has been given of the case where the speed control of the focus lens unit  111  is performed in synchronization with the image update period from time T( 2 ) to time T( 3 ) of  FIG. 20 , when the focus lens unit  111  can reach the true focusing point in a time period shorter than integral multiples of the image update period, the focus lens unit  111  may be driven to the true focusing point at the maximum speed, as in the second embodiment. 
     In addition, in this embodiment, although it is assumed that the focus lens unit  111  is driven toward the close side as the forward direction in Step S 312  in the subroutine for the focusing direction determination of  FIG. 18 , the focus lens unit  111  may also be driven toward the infinite side as the forward direction. 
     Fourth Embodiment 
     Each of the first to third embodiments has described the example where the focusing determination is performed by comparing the contrast evaluating value and the threshold value α. Although it is described that the threshold value α is an arbitrary value, the peak value of the contrast evaluating value at an in-focus state fluctuates depending on an image taking environment and object conditions, and hence there are cases where it is difficult to uniquely determine the threshold value α. Accordingly, when the contrast autofocus using the image signal is performed, a method in which the focusing point is searched for by performing a so-called hill climbing determination is commonly used. It is described above that the focusing precision is improved by increasing the number of search points, while it takes time to obtain an in-focus state. With this being the situation, by performing the hill climbing determination on the neighborhood of the focusing proposed point computed as a phase difference target position, a quick and high-precision focusing operation can be obtained. In this embodiment, a method for automatic focusing suitable for such situation is described. 
     The structure of the automatic focusing apparatus, the structure of the autofocus sensor, and the arrangement of the focus detection areas in a fourth embodiment are the same as those of  FIGS. 1 and 2A  in the first embodiment, and hence descriptions thereof are omitted. A description is given referring to  FIGS. 21 to 25  by the image taking scene of  FIG. 2B  as an example, similarly to the first embodiment. 
       FIG. 21  is a flowchart illustrating the flow of automatic focusing processes in the automatic focusing apparatus  100 . The CPU  130  controls those processes according to a computer program stored in the memory (not shown). 
     In Steps S 101  to S 103 , S 120  to S 122 , and S 150  of  FIG. 21 , the same processes as those in the first embodiment are executed, and hence descriptions thereof are omitted. 
     After Step S 122 , the process flow proceeds to Step S 401 . In Step S 401 , the computation of the defocus amount is performed. At this time, the target position is set at a position F(i)−ΔF obtained by offsetting the focusing proposed position F(i) by a predetermined value. Similarly to the first embodiment, the defocus amount is determined so that time required for the focus lens unit to reach the target position matches time of an integral multiple of the image update period. Next, the process flow proceeds to Step S 402  in which the focus lens unit  111  is driven to the position F(i)−ΔF, similarly to Step S 124  of  FIG. 3  of the first embodiment. That is, after a lapse of time of an integral multiple of the image update period 16 milliseconds, the focus lens unit  111  reaches the target position. Herein, ΔF is an arbitrary value, and ΔF may be written into a program or the like in advance or may be computed based on optical conditions of the image taking apparatus, or a structure may also be adopted in which selection and switching of ΔF can be externally performed using a volume or switch (not shown). 
     Next, the process flow proceeds to Step S 410  in which the hill climbing determination using the contrast evaluating value is performed.  FIG. 22  illustrates a subroutine in Step S 410 . First, in Step S 411  of  FIG. 22 , the contrast focus computing unit  132  obtains the image from the image processing unit  141 , and computes a contrast evaluating value V(i)′ at the position F(i)−ΔF of the focus lens unit  111 . Subsequently, the process flow proceeds to Step S 412  in which the lens controlling unit  134  drives the focus lens unit  111  to the position F(i). Then the process flow proceeds to Step S 413  in which a contrast evaluating value V(i) at the position F(i) of the focus lens unit  111  is computed, similarly to Step S 411 . Further, the process flow proceeds to Step S 414  in which the focus lens unit  111  is driven to a position F(i)+ΔF obtained by offsetting the position F(i) by a predetermined value. Then the process flow proceeds to Step S 415  in which a contrast evaluating value V(i)″ at the position F(i)+ΔF of the focus lens unit  111  is computed, similarly to Steps S 411  and S 413 . 
     Next, the process flow proceeds to Step S 416  in which the contrast evaluating values V(i), V(i)′, and V(i)″ obtained in Steps S 411  to S 415  are compared with each other to perform the hill climbing determination. As illustrated in Step S 416 , when V(i)&gt;V(i)′ and V(i)&gt;V″ are true, it is determined that an in-focus condition is obtained, and the process flow proceeds to Step S 417  in which a focusing flag is turned ON. On the other hand, when the determination result in Step S 416  is false, it is determined that an in-focus condition is not obtained, and the process flow proceeds to Step S 418  in which the focusing flag is turned OFF. 
       FIGS. 23A, 23B, and 23C  illustrate relations of the contrast evaluating values V(i), V(i)′, and V(i)″ to the positions F(i), F(i)−ΔF, and F(i)+ΔF of the focus lens unit  111  when the determination in Step S 416  is performed. When the relation as illustrated in  FIG. 23A  is given, a so-called contrast peak is attained, and the determination result is true in Step S 416 . 
     On the other hand, when the relations illustrated in  FIGS. 23B and 23C  are given, the contrast peak is not attained yet, and hence the determination result is false in Step S 416 . 
     The description returns to the flowchart of  FIG. 22 . After Step S 417 , the process flow proceeds to Step S 419  in which the focus lens unit  111  is driven to the focusing proposed position F(i), and the subroutine for the hill climbing determination is ended. 
     The description returns to the flowchart of  FIG. 21 . After Step S 410 , the process flow proceeds to Step S 403  in which the determination of the focusing flags set in Steps S 417  and S 418  of  FIG. 22  is performed. When the determination result is true, the processes are repeated from Step S 101 . On the other hand, when the determination result in Step S 403  is false, the process flow proceeds to Step S 140 . In Steps S 140  and S 141 , similarly to the first embodiment, another focusing proposed point is set, the processes are repeated from Step S 401 , and another focusing proposed point is searched for. 
     Herein, the process until focusing is achieved when the flowchart of  FIG. 21  is executed, and the process of the so-called hill climbing determination in the flowchart of  FIG. 22  are described with reference to  FIGS. 24 and 25 . 
     In  FIG. 24 , similarly to  FIG. 11  described in the first embodiment, the horizontal axis indicates the focusing proposed point C(i) and the focusing proposed position F(i) of the focus lens unit  111 . In addition, the vertical axis of  FIG. 24  similarly indicates the correlated evaluating value of the focusing proposed point C(i) and the contrast evaluating value V(i) thereof. In  FIG. 25 , similarly to  FIG. 12  described in the first embodiment, the horizontal axis indicates time, while the vertical axis indicates the position of the focus lens unit  111 . 
     It is assumed that, at time T( 0 ) of  FIG. 25 , the position F( 0 ) of the focus lens unit  111  detected in Step S 101  of  FIG. 21  is at positions illustrated in  FIGS. 24 and 25 . In addition, similarly to the first to third embodiments, the true in-focus point is assumed to be F( 3 ). In Step S 121  of the flowchart of  FIG. 21 , similarly to the first embodiment, it is determined that the direction toward the in-focus point is the infinite direction. Next, in Step S 122 , a value  1  is set in the focusing proposed point number i. Then, Steps S 401  and S 402  are executed, and, as illustrated in  FIGS. 24 and 25 , a hill climbing evaluation is performed at positions of three points F( 1 )−ΔF, F( 1 ), and F( 1 )+ΔF, which are in the neighborhood of the position F( 1 ) of the focus lens unit  111  in Step S 410 . The contrast evaluating values V( 1 )′ and V( 1 )″ in the neighborhood of the contrast evaluating value V( 1 ) have the positional relation as illustrated in  FIG. 23B . Therefore, the result of the focusing determination in Step S 416  of the flowchart of  FIG. 22  is false, and the process flow proceeds to Step S 418 . When i=2 is satisfied, in the situation illustrated in  FIG. 25 , the same contrast evaluating value as that obtained when i=1 is satisfied is obtained. Consequently, the positional relation as illustrated in  FIG. 23B  is given, and the result of the focusing determination in Step S 416  of the flowchart of  FIG. 22  is false. Similarly, when i=3 is satisfied, the contrast evaluating values have the relation as illustrated in  FIG. 23A . Therefore, the result of the focusing determination in Step S 416  of the flowchart of  FIG. 22  is true. Then, in Step S 419 , the focus lens unit  111  is driven to the position F( 3 ). 
       FIG. 25  illustrates the locus of the focus lens unit  111 . As illustrated in  FIG. 25 , the driving speed of the focus lens unit  111  between the individual focusing proposed points is set so that the focus lens unit  111  is quickly driven, similarly to the first embodiment. However, the driving speed is reduced between the positions F(i)±ΔF, that is, in the neighborhood of the individual focusing proposed points, to obtain the contrast evaluating values. In addition to the reduction in driving speed, by driving the focus lens unit  111  in synchronization with the timing at which the individual contrast evaluating values are computed, the search can be effectively performed only in the neighborhood of the focusing proposed points. 
     Thus, in this embodiment, the driving speed of the focus lens unit  111  is increased between the focusing proposed points, and is reduced in the neighborhoods of the focusing proposed points, to thereby quickly detect the focusing point with high precision. 
     In this embodiment, although the example where the hill climbing determination is performed on the neighborhood of the focusing proposed point C(i) using the contrast evaluating value in the flowchart of  FIG. 21  has been described, by applying Steps S 152 , S 153 , S 154 , and S 155  of the flowchart of  FIG. 10 , the focusing point may be searched for in detail. 
     Although the exemplary embodiments of the present invention have been described thus far, it should be appreciated that the present invention is not limited to those embodiments, and various modifications and changes may be made without departing from the gist thereof. 
     For example, the processes described in the first to fourth embodiments may be combined and performed. Further, in order to support multiple image taking scenes, a switching unit may be provided to switch among the processes. 
     In the present invention, although the example where the separating unit is provided in the imaging optical system and the focus detecting unit using the separated beam is provided has been described, a structure may also be adopted in which the half mirror  121  is not provided, and the focus detecting unit  122  is provided outside the automatic focusing apparatus  100  to detect the focus by using the beam from outside light. 
     In addition, in the present invention, although the example where the separating unit is provided in the imaging optical system and the focus detecting unit using the separated beam is provided has been described, a structure may also be adopted in which the half mirror  121  is not provided, and the image pickup element  140  and the focus detecting unit  122  are provided as one unit. 
     Further, in the present invention, as illustrated in  FIG. 1 , although the components other than the switch  201  are provided in the automatic focusing apparatus  100 , the components may be separately provided in different units. Further, although the phase difference focus computing unit  131 , the contrast focus computing unit  132 , the defocus amount computing unit  133 , and the lens controlling unit  134  are provided in one CPU  150 , the components may be separately provided in different CPUs or arithmetic units, or may be provided outside the automatic focusing apparatus  100 . 
     Moreover, in the present invention, although the update period of the image signal is set to 16 milliseconds, it should be appreciated that the update period thereof is not limited to 16 milliseconds, and the present invention may be carried out according to various update periods of the image signal. 
     This application claims the benefit of Japanese Patent Application No. 2010-012093, filed Jan. 22, 2010, which is hereby incorporated by reference herein in its entirety.