Imaging device, imaging method, and program
阅读说明:本技术 摄像装置、摄像方法及程序 (Imaging device, imaging method, and program ) 是由 内田亮宏 田中康一 林健吉 藤木伸一郎 伊泽诚一 于 2018-10-02 设计创作,主要内容包括:摄像装置在执行自动聚焦时,根据伴随聚焦透镜的位置变化的像倍率变化量的基准值分别对多个光圈值导出分别与自动聚焦区域中的多个光圈值对应的像倍率变化量,并且在所导出的变化量中,将与所容许的像倍率变化量的阈值以下的变化量中的任一个对应的光圈值作为光圈极限值来确定,当由执行自动聚焦时的被摄体亮度求出的光圈值超过所确定的光圈极限值时,将光圈值设定为光圈极限值。(The imaging apparatus derives, for each of a plurality of aperture values, an image magnification variation amount corresponding to each of the plurality of aperture values in an autofocus area based on a reference value of an image magnification variation amount accompanying a change in a position of a focus lens when autofocus is performed, determines, as an aperture limit value, an aperture value corresponding to any one of variation amounts equal to or smaller than a threshold value of an allowable image magnification variation amount among the derived variation amounts, and sets the aperture value as the aperture limit value when the aperture value obtained from subject brightness when autofocus is performed exceeds the determined aperture limit value.)
1. An imaging device includes:
an image pickup lens including a focus lens;
an image pickup unit that picks up an optical image that has passed through the image pickup lens;
an acquisition unit that acquires a reference value of an amount of change in image magnification associated with a change in position of the focus lens for each of a plurality of aperture values;
a deriving unit that derives, when performing autofocus, an image magnification variation amount corresponding to each of the plurality of aperture values in the autofocus area, based on the reference value of the variation amount acquired by the acquiring unit;
a determination unit configured to determine, as a diaphragm limit value, a diaphragm value corresponding to any one of the variation amounts, among the variation amounts derived by the derivation unit, that is equal to or smaller than a threshold value of the allowable image magnification variation amount; and
and a setting unit that sets the aperture value as the aperture limit value determined by the determination unit when the aperture value obtained from the subject brightness at the time of performing the auto-focusing exceeds the aperture limit value.
2. The image pickup apparatus according to claim 1,
the larger the size of the autofocus area, the larger the value of the threshold.
3. The imaging device according to claim 1 or 2, further comprising:
a detection unit for detecting the amount of movement of the subject before execution of the auto-focusing,
the threshold value is a smaller value as the amount of movement of the object detected by the detection unit increases.
4. The image pickup apparatus according to any one of claims 1 to 3,
the higher the frame rate when searching for an in-focus position by autofocus, the larger the value of the threshold.
5. The image pickup apparatus according to claim 4,
when the operation mode of the auto-focusing is a mode in which focusing accuracy is prioritized, the threshold value is set to a larger value as the frame rate is higher.
6. The image pickup apparatus according to any one of claims 1 to 5,
the threshold value is a smaller value as the object distance when the autofocus is performed last time is shorter.
7. The image pickup apparatus according to claim 6,
in the range between the lower limit value and the upper limit value of the object distance, the lower limit value and the upper limit value are set to larger values as the focal length of the imaging lens is longer when the threshold value is set to a smaller value as the object distance is shorter.
8. The image pickup apparatus according to claim 6 or 7,
when the similarity between the result of execution of the automatic exposure when the automatic focusing was executed last time and the result of execution of the automatic exposure this time is equal to or greater than a predetermined degree, the threshold value is set to a smaller value as the object distance becomes shorter.
9. The image pickup apparatus according to any one of claims 1 to 8,
the specifying unit specifies, as a diaphragm limit value, an aperture value corresponding to the largest variation amount that is equal to or smaller than the threshold value, among the variation amounts derived by the deriving unit.
10. An imaging method performed by an imaging device including an imaging lens including a focusing lens and an imaging unit that captures an optical image passing through the imaging lens,
a reference value of an amount of change in image magnification accompanying a change in position of the focus lens is acquired for each of a plurality of aperture values,
deriving an image magnification variation amount corresponding respectively to each of the plurality of aperture values in the auto focusing area, based on the acquired reference value of the variation amount when performing auto focusing,
determining, as the aperture limit value, an aperture value corresponding to any one of the variation amounts equal to or smaller than the threshold value of the allowable image magnification variation amount among the derived variation amounts,
when the aperture value found from the subject luminance at the time of performing the auto focus exceeds the determined aperture limit value, the aperture value is set to the aperture limit value.
11. A program for causing a computer that controls an imaging device including an imaging lens including a focus lens and an imaging unit that captures an optical image that has passed through the imaging lens to execute:
acquiring a reference value of an image magnification variation amount accompanying a positional change of the focus lens for each of a plurality of aperture values;
deriving, when performing autofocus, an image magnification variation amount corresponding respectively to each of the plurality of aperture values in the autofocus area, based on the acquired reference value of the variation amount;
determining, as a diaphragm limit value, an aperture value corresponding to any one of the variation amounts equal to or smaller than a threshold value of the allowable image magnification variation amount, among the derived variation amounts; and
when the aperture value found from the subject luminance at the time of performing the auto focus exceeds the determined aperture limit value, the aperture value is set to the aperture limit value.
Technical Field
The invention relates to an imaging apparatus, an imaging method, and a program.
Background
Conventionally, there has been disclosed an imaging device in which, in order to obtain an appropriate blur at an out-of-focus position, an aperture value is changed to a constant reference aperture value or less according to a position of a focus lens or an image magnification (see japanese unexamined patent publication No. 2014/045913).
An image pickup apparatus is disclosed which calculates an image magnification of an object, obtains an aperture value from the calculated image magnification, and sets the aperture value calculated from the image magnification of the object as an exposure control aperture value when the image magnification exceeds a certain value (see japanese patent application laid-open No. 2-126245).
Disclosure of Invention
Technical problem to be solved by the invention
However, some lenses of the imaging apparatus change the image magnification of the subject (generate so-called breathing) with a change in the position of the focus lens. In an imaging apparatus including such a lens, if AutoFocus is performed by a method (for example, a contrast AF (auto focus) method) using an evaluation value in an AutoFocus area without considering an image magnification change amount, the object may be out of the AutoFocus area. In this case, the evaluation value in the autofocus area is not an accurate value, and as a result, the focusing accuracy is reduced.
However, in the techniques described in japanese unexamined patent publication No. 2014/045913 and japanese unexamined patent publication No. 2-126245, the magnification is considered, but the amount of change in the magnification is not considered.
The present invention has been made in view of the above circumstances, and provides an imaging apparatus, an imaging method, and a program that can suppress a decrease in focusing accuracy based on an imaging apparatus in which a lens whose image magnification changes with a change in the position of a focus lens is mounted.
Means for solving the technical problem
An imaging device of the present invention includes: an image pickup lens including a focus lens; an image pickup unit that picks up an optical image that has passed through an image pickup lens; an acquisition unit that acquires a reference value of an amount of change in image magnification associated with a change in position of the focus lens for each of the plurality of aperture values; a deriving unit that derives, when performing autofocus, image magnification variation amounts corresponding to the plurality of aperture values in the autofocus area, respectively, based on the reference value of the variation amount acquired by the acquiring unit; a determination unit that determines, as a diaphragm limit value, a diaphragm value corresponding to any one of the variation amounts that are equal to or less than a threshold value of the allowable image magnification variation amount, among the variation amounts derived by the derivation unit; and a setting unit that sets the aperture value as the aperture limit value when the aperture value obtained from the subject brightness at the time of performing the auto-focusing exceeds the aperture limit value determined by the determination unit.
In the imaging device of the present invention, the threshold may be set to a value that is larger as the size of the autofocus area is larger.
The image pickup apparatus of the present invention may further include a detection unit that detects a movement amount of the object before execution of the auto focus, and the threshold value may be set to a smaller value as the movement amount of the object detected by the detection unit is larger.
In the imaging apparatus of the present invention, the threshold value may be set to a value that increases as the frame rate when searching for the in-focus position by the autofocus becomes higher.
In the imaging apparatus of the present invention, when the operation mode of the auto focus is the mode in which the focusing accuracy is prioritized, the threshold may be set to a larger value as the frame rate is higher.
In the imaging apparatus of the present invention, the threshold value may be set to a smaller value as the object distance when the autofocus is executed last time is shorter.
In the imaging device of the present invention, the lower limit value and the upper limit value may be set to values that are larger as the focal length of the imaging lens is longer, when the threshold value is set to a smaller value as the object distance is shorter, within the range between the lower limit value and the upper limit value of the object distance.
In the imaging apparatus according to the present invention, the threshold may be set to a smaller value as the object distance becomes shorter when the similarity between the result of execution of the automatic exposure when the autofocus is executed last time and the result of execution of the automatic exposure this time becomes equal to or greater than the predetermined degree.
In the imaging device according to the present invention, the determination unit may determine, as the aperture limit value, an aperture value corresponding to the largest change amount that is equal to or smaller than the threshold value, among the change amounts derived by the derivation unit.
On the other hand, an image pickup method according to the present invention is performed by an image pickup apparatus including an image pickup lens including a focus lens and an image pickup unit that picks up an optical image passing through the image pickup lens, wherein a reference value of an amount of change in image magnification accompanying a change in position of the focus lens is acquired for each of a plurality of aperture values, when autofocusing is performed, the amount of change in image magnification corresponding to each of the plurality of aperture values in an autofocus area is derived from the acquired reference value of the amount of change, of the amount of change derived, an aperture value corresponding to any one of the amounts of change that are equal to or less than a threshold value of the allowable amount of change in image magnification is determined as an aperture limit value, and when the aperture value obtained from subject brightness when autofocusing is performed exceeds the determined aperture limit value, the aperture value is set as the aperture limit value.
Further, a program of the present invention is a program for causing a computer that controls an imaging device including an imaging lens including a focus lens and an imaging unit that captures an optical image that has passed through the imaging lens to execute: acquiring reference values of the image magnification variation amount accompanying the position variation of the focus lens for each of the plurality of aperture values; deriving, when performing autofocus, image magnification variation amounts respectively corresponding to a plurality of aperture values in an autofocus area, based on the obtained reference value of the variation amount; determining, as a diaphragm limit value, an aperture value corresponding to any one of the variation amounts equal to or smaller than a threshold value of the allowable image magnification variation amount, among the derived variation amounts; and setting the aperture value as the aperture limit value when the aperture value found from the subject luminance at the time of performing the auto focus exceeds the determined aperture limit value.
The imaging device of the present invention includes an imaging lens including a focus lens, an imaging unit for capturing an optical image passing through the imaging lens, a memory for storing commands to be executed by a computer, and a processor configured to execute the stored commands, wherein the processor acquires a reference value of an amount of change in image magnification associated with a change in position of the focus lens for each of a plurality of aperture values, and when performing auto focus, deriving image magnification variation amounts corresponding to a plurality of aperture values in the autofocus area, respectively, based on the acquired reference value of the variation amount, determining, as the aperture limit value, an aperture value corresponding to any one of the variation amounts equal to or smaller than the threshold value of the allowable image magnification variation amount among the derived variation amounts, when the aperture value found from the subject luminance at the time of performing the auto focus exceeds the determined aperture limit value, the aperture value is set as the aperture limit value.
Effects of the invention
According to the present invention, it is possible to suppress a decrease in focusing accuracy in an imaging apparatus including a lens in which the image magnification changes with a change in the position of a focus lens.
Drawings
Fig. 1 is a block diagram showing an example of a hardware configuration of an imaging apparatus according to each embodiment.
Fig. 2 is a block diagram showing an example of a hardware configuration of an imaging lens included in the imaging device according to each embodiment.
Fig. 3 is a graph for explaining autofocus according to each embodiment.
Fig. 4 is a diagram for explaining an autofocus area according to each embodiment.
Fig. 5 is a conceptual diagram illustrating an example of the storage content of the secondary storage unit of the lens-side main control unit included in the imaging lens according to each embodiment.
Fig. 6 is a diagram showing an example of the variation data according to each embodiment.
Fig. 7 is a conceptual diagram illustrating an example of the storage contents of the secondary storage unit of the main body side main control unit included in the imaging apparatus main body according to each embodiment.
Fig. 8 is a flowchart showing an example of the AF control processing according to each embodiment.
Fig. 9 is a flowchart showing an example of the diaphragm limit value determination processing according to
Fig. 10 is a diagram for explaining processing for deriving the image height according to each embodiment.
Fig. 11 is a diagram for explaining a process of deriving an image magnification variation amount according to each embodiment.
Fig. 12 is a diagram showing an example of the aperture limit value according to
Fig. 13 is a flowchart showing an example of the diaphragm limit value determination processing according to
Fig. 14 is a flowchart showing an example of the diaphragm limit value determination processing according to
Fig. 15 is an example of an AF program diagram when the operation mode of AF according to
Fig. 16 is an example of an AF program diagram when the operation mode of AF according to
Fig. 17 is a flowchart showing an example of the diaphragm limit value determination processing according to
Fig. 18 is a flowchart showing an example of the diaphragm limit value determination processing according to
Fig. 19 is a graph for explaining the process of deriving the threshold value according to
Detailed Description
Hereinafter, embodiments for carrying out the technique of the present invention will be described in detail with reference to the drawings.
[ embodiment 1 ]
First, the configuration of the
The
In the
In the autofocus mode, adjustment of imaging conditions is performed by setting a release button (not shown) provided in the imaging device
The
The imaging apparatus
The main body side main control Unit 28 is an example of a computer that controls the
The CPU60, the primary storage unit 62, and the
The 1
At the light receiving surface covering position α, the 1
The imaging element driver 32 is connected to the
The image signal processing circuit 34 reads an image signal of 1 frame from the
The image processing unit 38 acquires image signals from the image memory 36 at a predetermined frame rate for each frame, and performs various processes such as gamma correction, luminance and color difference conversion, and compression processing on the acquired image signals. The image processing unit 38 outputs the image signals obtained by performing various kinds of processing to the display control unit 40 at a predetermined frame rate for each frame. The image processing unit 38 outputs an image signal obtained by performing various processes to the CPU60 in accordance with a request from the CPU 60.
The display control section 40 is connected to a display 42, and controls the display 42 under the control of the CPU 60. The display control unit 40 outputs the image signal input from the image processing unit 38 to the display 42 at a predetermined frame rate for each frame. The display 42 displays an image represented by an image signal input at a predetermined frame rate from the display control unit 40 as a live view image. The display 42 also displays a still image, which is a single frame image obtained by shooting a single frame. In addition, a menu screen or the like is displayed on the display 42 in addition to the live view image.
The receiving device 46 has a dial, a release button, a cross key, a MENU key, a touch panel, and the like, which are not shown, and receives various commands from a user. The receiving device 46 is connected to the receiving I/F44, and outputs a command content signal indicating the content of the received command to the receiving I/F44. The reception I/F44 outputs a command content signal input from the reception device 46 to the CPU 60. The CPU60 executes processing corresponding to the command content signal input from the reception I/F44.
The media I/F48 is connected to the memory card 50, and records and reads image files on and from the memory card 50 under the control of the CPU 60. The image file read from the memory card 50 through the media I/F48 is decompressed by the image processing unit 38 under the control of the CPU60 and displayed on the display 42 as a playback image.
By connecting the
As an example, as shown in fig. 2, the
The subject light enters the
The
The
The
The lens-side
The CPU88, the
By connecting the
The
The focus
The
The
Then, the
As an example, as shown in fig. 5, the
As an example, as shown in fig. 6, the
In other words, the
The amount of change in image magnification of the
On the other hand, as shown in fig. 7, for example, the
Next, an operation of the
In step S10 of fig. 8, the CPU60 acquires reference values of the amount of change in image magnification associated with the change in position of the
In step S12, the CPU60 acquires the position of the AF area within the shooting angle of view (in the present embodiment, the center position of the AF area). In step S14, the diaphragm limit value determination process shown in fig. 9 is executed. In step S30 of fig. 9, the CPU60 derives the image height of the position of the AF area acquired by the process of step S12. Specifically, as shown in fig. 10, for example, the CPU60 derives the image height of the position of the AF area by dividing the distance from the center of the shooting angle of view to the center position of the AF area (D _ AF shown in fig. 10) by the distance from the center of the shooting angle of view to any one of the four corners of the shooting angle of view (lower right corner in the example of fig. 10) (D shown in fig. 10).
In step S32, the CPU60 derives image magnification variation amounts corresponding to a plurality of aperture values at the position of the AF area acquired by the processing of step S12, respectively, from the
The process of deriving the image magnification variation amount is expressed by the following formula (1).
The image magnification
(1) KD in the equation indicates that the focusing
Next, the CPU60 derives the coefficient K according to the following expression (2) using the image height ZP corresponding to the image magnification variation in the
K=(D_af÷D)÷ZP……(2)
Then, the CPU60 multiplies the derived coefficient K by the derived image magnification variation amount corresponding to 35 times the depth of field, thereby deriving image magnification variation amounts corresponding to a plurality of aperture values at the position of the AF area acquired by the processing of step S12. For example, when the image height at the position of the AF area acquired by the processing of step S12 is 40%, the CPU60 derives a value obtained by multiplying the derived image magnification variation amount corresponding to 35 times the depth of field by 0.5(═ 40% ÷ 80%), as shown on the right side of fig. 11, for example.
In step S34, the CPU60 determines, as a diaphragm limit value, a diaphragm value corresponding to the largest variation amount that is equal to or smaller than the threshold TH1 among the image magnification variation amounts corresponding to the plurality of diaphragm values at the position of the AF area derived by the processing of step S32. For example, in the example of fig. 11, when the image height of the position of the AF area is 80% and the threshold TH1 is 3.5%, the aperture limit value is determined to be F10. Further, for example, in the example of fig. 11, when the image height of the position of the AF area is 40% and the threshold TH1 is 3.5%, the diaphragm limit value is determined as F20. Therefore, in the present embodiment, as an example, as shown in fig. 12, the aperture limit value is determined based on the position of the AF area. Specifically, the closer the AF area is to the center of the photographing angle of view (the higher the image height), the smaller the aperture limit value is determined (the value on the open side).
As the threshold TH1, for example, an upper limit value of an allowable image magnification variation amount or the like can be applied. As a specific example, a value of half of the ratio of the horizontal length of the AF area to the horizontal length of the photographing angle of view is applied as the
In step S34, the CPU60 may determine, as the stop limit value, the aperture value corresponding to any one of the changes in the image magnification ratio corresponding to the plurality of aperture values at the position of the AF area within a predetermined range of the threshold TH1 having the threshold TH1 as the upper limit. When the process of step S34 ends, the diaphragm limit value determination process ends, and the process proceeds to step S16 of the AF control process shown in fig. 8.
In step S16 of fig. 8, the CPU60 determines the exposure state (aperture value, shutter speed, and sensitivity) in AF according to the subject luminance. Specifically, the CPU60 performs AE control by using the AF area, and determines the aperture value, shutter speed, and sensitivity from the subject luminance.
In step S18, the CPU60 determines whether the aperture value determined by the process of step S16 is equal to or less than the aperture limit value determined by the process of step S14. When the determination becomes an affirmative determination, the process proceeds to step S20. In step S20, the CPU60 sets the aperture value, the shutter speed, and the sensitivity determined by the processing of step S16 as the aperture value, the shutter speed, and the sensitivity when AF is performed. When the process at step S20 ends, the process proceeds to step S26.
On the other hand, when the determination at step S18 becomes a negative determination, the process proceeds to step S22. In step S22, the CPU60 sets the diaphragm limit value determined by the process of step S14 as the diaphragm value when AF is performed. In step S24, the CPU60 determines the shutter speed and sensitivity corresponding to the aperture value set by the processing of step S22 by performing AE control. Then, the CPU60 sets the determined shutter speed and sensitivity as the shutter speed and sensitivity when executing AF. When the process at step S24 ends, the process proceeds to step S26.
In step S26, the CPU60 executes AF in accordance with the aperture value, shutter speed, and sensitivity set by the above processing. When the process of step S26 ends, the AF control process ends.
As described above, according to the present embodiment, when AF is performed, the amount of change in image magnification corresponding to each of the plurality of aperture values in the AF area is derived from the reference value of the amount of change in image magnification associated with the change in position of the
[ 2 nd embodiment ]
Depending on the size of the AF area, the position of the
An operation of the
In step S33A of fig. 13, the CPU60 derives the threshold TH1 from the size of the AF area in accordance with the following expression (3).
TH1=TH_def×H÷H_def……(3)
(3) TH _ def in the formula represents a threshold value (threshold value TH1 in embodiment 1) for the default size of the AF area. In the formula (3), H represents the size (horizontal length in the present embodiment) of the AF area in the current AF, and H _ def represents the default size of the AF area. Therefore, in the present embodiment, the threshold TH1 has a larger value as the size of the AF area is larger. In the processing of the next step S34, the threshold TH1 derived in this step S33A is used to determine the diaphragm limit value.
As described above, according to the present embodiment, the threshold TH1 has a larger value as the size of the AF area is larger. Therefore, it is possible to suppress a decrease in focusing accuracy and to suppress unnecessary diaphragm limitation.
[ embodiment 3 ]
An operation of the
In step S33B of fig. 14, the CPU60 derives a movement vector of the object at a plurality of positions within the live view image using a plurality of pieces of image data of the live view image. As a method of deriving the motion vector of the subject, for example, the method described in japanese patent No. 5507014 can be applied. Then, the CPU60 detects the maximum value of the magnitudes of the derived movement vectors of the object at the plurality of positions as the movement amount of the object.
In step S33C, the CPU60 corrects the threshold TH1 according to the following expression (4) and the amount of movement of the object.
TH1=TH1×(1-K×X_max)……(4)
(4) TH1 on the right side of the equation indicates a threshold TH1 derived by the processing of step S33A, and X _ max indicates the amount of movement of the object detected by the processing of step S33B. K in the expression (4) is a coefficient set in advance, and is determined according to the upper limit value of the assumed movement amount of the object in the present embodiment. For example, when the upper limit of the assumed movement amount of the object is the same as the horizontal length of the AF area, the upper limit is set to a value of about 50% of the horizontal length of the AF area. Therefore, in the present embodiment, the threshold TH1 becomes smaller as the moving amount of the object before AF is performed increases. In the processing of the next step S34, the threshold TH1 derived in this step S33C is used to determine the diaphragm limit value. In step S34, when the threshold TH1 is smaller than the minimum value of the image magnification change amount derived by the processing in step S32, the stop limit value may be determined as the stop value (F2.0 in the example of fig. 11) corresponding to the minimum value of the image magnification change amount.
As described above, according to the present embodiment, the threshold TH1 becomes smaller as the moving amount of the object before AF is performed increases. Therefore, as the amount of movement of the object increases, the influence of the positional change of the
[ 4 th embodiment ]
As a method of determining an exposure state in AF, a method using an AF program diagram is known. In this method, an aperture value, a shutter speed, and sensitivity in AF are determined from a photometric value (EV (exposure) value) of an object using a program diagram. When the operation mode of AF is a mode in which the AF speed is prioritized, as an example, as shown in fig. 15, the shutter speed is maintained while the aperture is switched to the open side so as not to decrease the frame rate (hereinafter referred to as "AF frame rate") when searching for the focused position by AF as the EV value decreases. The AF frame rate here indicates a time interval at which an AF evaluation value at the time of searching for an in-focus position by AF is acquired. Fig. 15 shows an example in which the aperture value at the time of shooting is F8.
On the other hand, when the operation mode of AF is a mode in which focusing accuracy is prioritized (hereinafter referred to as "accuracy priority mode"), as an example, as shown in fig. 16, since it is desired to maintain the diaphragm as much as possible during shooting even when the EV value is small, the shutter speed is lowered while maintaining the same diaphragm, and the AF frame rate is also lowered. Fig. 16 also shows an example in which the aperture value at the time of shooting is F8. In the example shown in fig. 16, the AF frame rate is switched between 120fps (frameperssecond: frame rate) and 60fps with 13EV as a boundary, as shown by a broken line H1. In this case, as indicated by a broken line H2, the AF frame rate is switched between 60fps and 30fps with 12EV as a boundary.
When the object moves, the lower the AF frame rate, the easier it becomes for the object to leave the AF area. Therefore, in the present embodiment, when the operation mode of AF is the accuracy priority mode, the threshold TH1 is changed in accordance with the AF frame rate.
An operation of the
In step S33D of fig. 17, the CPU60 determines whether the operation mode of AF is the accuracy priority mode. When the determination is a negative determination, the process proceeds to step S34, and when the determination is an affirmative determination, the process proceeds to step S33E.
In step S33E, the CPU60 derives a threshold TH1 corresponding to the AF frame rate according to the following expression (5).
TH1 TH1 × AF frame rate ÷ reference frame rate … … (4)
As in
As described above, according to the present embodiment, when the operation mode of AF is the precision priority mode, the threshold TH1 has a larger value as the AF frame rate is higher. Therefore, the object is less likely to deviate from the AF area, and as a result, the reduction in focusing accuracy can be further suppressed.
[ 5 th embodiment ]
The operation of the
In step S33F of fig. 18, the CPU60 determines whether or not the elapsed period since the AF was last executed is within a predetermined period (for example, 10 seconds). When the determination is a negative determination, the process proceeds to step S34, and when the determination is an affirmative determination, the process proceeds to step S33G. This is because, when the elapsed period since AF was performed last time is short, the same subject as that at the time of AF was performed last time is regarded as being photographed in a state in which the subject distance hardly changes.
In step S33G, the CPU60 derives the threshold TH1 as a smaller value as the object distance when AF was performed last time is shorter. Specifically, as an example, as shown in fig. 19, the CPU60 sets the threshold TH1 to a value smaller than a default value (3.5% in the present embodiment) as the object distance becomes shorter within the range between the lower limit value and the upper limit value of the object distance. Note that, in fig. 19, the parenthesized description in the horizontal axis indicates the object distance when AF was performed last time. In the present embodiment, a standard lens (an imaging lens having a focal length of 50mm in terms of 35 mm) is used as a reference. When the process of step S33G ends, the process proceeds to step S34. When the elapsed period since the AF was performed last time is within the predetermined period, the threshold TH1 derived in step S33G is used to determine the diaphragm limit value in the processing of step S34. On the other hand, when the elapsed period since the AF was performed last time exceeds the predetermined period, the processing of step S34 determines the diaphragm limit value using the preset threshold TH1, as in
As described above, according to the present embodiment, the threshold TH1 is set to a smaller value as the object distance when AF was previously performed becomes shorter. Therefore, the object is less likely to deviate from the AF area, and as a result, the reduction in focusing accuracy can be further suppressed.
In the above-described
In the above-described
In the above embodiments, the AF control executed by the CPU by executing software (program) may be executed by various processors other than the CPU. The processor in this case may be, for example, a dedicated electric Circuit or the like having a Circuit configuration designed specifically for executing a Specific process, such as a PLD (Programmable logic device) or an ASIC (Application Specific Integrated Circuit) whose Circuit configuration can be changed after manufacture, such as an FPGA (Field-Programmable gate Array). The AF control process may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same kind or different kinds (for example, a plurality of FPGAs, a combination of a CPU and an FPGA, or the like). More specifically, the hardware configuration of these various processors is an electric circuit in which circuit elements such as semiconductor elements are combined.
In the above embodiments, the
The disclosure of the japanese patent application 2018-010738, filed on 25.1.2018, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards cited in the present specification are incorporated by reference into the present specification to the same extent as if each document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.
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