JP2007264299A - Focus adjustment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus adjustment device capable of obtaining high focusing accuracy even when a subject image has a periodical pattern. <P>SOLUTION: A digital camera 20 incorporating a focus adjustment device has: a phase difference AF sensor unit 9 detecting the phase difference of subject light in a detection area; a first focus detection part 12 performing focus detection based on output from the sensor unit; a second focus detection part 14 performing focus detection by imager AF based on output from an imaging device 7; and a control part 16 performing focus adjustment control, in order to perform focus adjustment of the focus lens 3 of an interchangeable lens 2, and performs the focus adjustment where phase difference AF and the imager AF are combined. It performs the focus adjustment by switching to only the imager AF when detecting that the periodical pattern is included in the subject image. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a focus adjustment device such as a digital still camera or a video camera.

  Conventionally, a TTL (Through The Lens) phase difference AF or the like is used as an AF mechanism of an autofocus (AF) single-lens reflex camera to which a silver salt film type or digital type interchangeable lens is applied. In this AF mechanism, a defocus detection mechanism for AF is provided in the camera body, and a focus adjustment operation is performed by driving the focus adjustment lens of the interchangeable lens in the lens or in the camera. In compact digital cameras, video cameras, and the like, so-called imager AF that performs contrast detection using a high-frequency component of a signal from an image sensor is performed. When the TTL phase difference AF and the imager AF are compared, for example, the TTL phase difference AF has a higher speed and the imager AF has a higher accuracy, and is used properly depending on the application. .

Patent Document 1 discloses a technique for performing focus adjustment by combining imager AF and TTL phase difference AF. In this focus adjustment, coarse adjustment is performed using phase difference AF, and then adjustment is performed using imager AF. Similarly, in Patent Document 2, in the configuration in which the coarse adjustment is performed by the phase difference AF and the adjustment is performed by the imager AF, when it is determined that the focus can be achieved by the TTL phase difference AF, the TTL position is higher than the imager AF. The phase difference AF is prioritized and executed to speed up the focus adjustment.
Japanese Patent Laid-Open No. 7-43605 JP 2003-302571 A

  However, the conventional example has the following problems. That is, the TTL phase difference AF has a drawback that accurate focus detection cannot be performed for a periodic pattern due to its configuration. In the conventional example, the processing when the subject is a periodic pattern is not mentioned. Therefore, accurate focus detection cannot be performed for the periodic pattern. In Patent Document 1, imager AF is performed at an incorrect focus lens position by rough adjustment of TTL phase difference AF, and as a result, there arises a problem that correct focus adjustment cannot be performed. In Patent Document 2, it is not determined that focusing is possible with TTL phase difference AF.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a focus adjustment device capable of obtaining high focusing accuracy even when a subject image has a periodic pattern. To do.

In order to achieve the above object, a focus adjustment apparatus according to claim 1 of the present invention includes a first focus detection unit that performs focus detection by a phase difference method and a second focus detection that performs focus detection by a contrast method. And a focus adjustment unit that adjusts the focus of the lens based on the focus adjustment information, and the reflected light from the subject is periodic based on the focus detection information from the first focus detection unit. A periodic pattern determining unit that determines whether or not the pattern has a pattern, and when the subject having the periodic pattern is determined by the periodic pattern determining unit, Control means for controlling the focus adjusting means based on focus detection information.

  The focus adjustment apparatus according to claim 2 of the present invention is the focus adjustment apparatus according to claim 1, wherein the periodic pattern determination means is calculated based on focus detection information from the first focus detection means. If the difference between the smallest first minimum value and the next smallest second minimum value is smaller than a predetermined value, it is determined that the reflected light from the subject has a periodic pattern. To do.

  The focus adjustment apparatus according to claim 3 of the present invention is the focus adjustment apparatus according to claim 1, wherein the control means is determined to be an object having no periodic pattern by the periodic pattern determination means. At this time, the focus adjustment operation is performed by combining the focus detection information from the first focus detection means and the focus detection information from the second focus detection means.

  According to a fourth aspect of the present invention, there is provided a focus adjustment apparatus comprising: a first focus detection unit that detects a focus state of a plurality of focus detection regions by a phase difference method; and a focus state of a region corresponding to the plurality of focus detection regions. A second focus detection means for detecting the image using a contrast method, a focus adjustment means for adjusting the focus of the lens based on the focus adjustment information, and the plurality of the plurality of focus detection information based on the focus detection information from the first focus detection means. A periodic pattern determination unit that determines whether or not all of the detectable focus detection regions have a periodic pattern, and the focus detection region that is detectable by the periodic pattern determination unit Are determined to have the periodic pattern, the focus adjusting means is controlled based on focus detection information from all areas output from the second focus detecting means. When it is determined that at least one of the detectable focus detection areas does not have a periodic pattern, the focus detection information from the first focus detection means and the second focus detection means Control means for controlling the focus adjusting means in combination with the focus detection information from.

  The focus adjustment apparatus according to claim 5 of the present invention is the focus adjustment apparatus according to claim 4, wherein the periodic pattern determination unit outputs the plurality of focus detection regions output from the first focus detection unit. Is calculated based on the focus detection information of each of the detectable focus detection areas, and the smallest first minimum value and the next smallest second minimum among the minimum values in the target area When the difference from the value is smaller than the predetermined value, it is determined that the region has a periodic pattern.

  According to the present invention, in a focus adjustment apparatus that performs a focus adjustment operation by combining focus detection by a phase difference method and focus detection by a contrast method, whether or not a subject has a periodic pattern is detected, and the periodic pattern is detected. In the case of having the periodic pattern, the weak phase difference method is not applied to the periodic pattern, and the focus adjustment is performed by the contrast method strong to the periodic pattern, so that high focus adjustment accuracy can be obtained even for an object having the periodic pattern. .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram of a digital camera incorporating a focus adjustment apparatus according to a first embodiment of the present invention.

  The digital camera 20 of the present embodiment includes a camera body 1 and an interchangeable lens 2 that can be attached to and detached from the camera body 1.

  The interchangeable lens 2 includes a focus lens 3 for performing focus adjustment, a photographing optical system having an optical axis O, a lens drive unit 4 for focus adjustment means for driving and adjusting the focus lens 3 in the optical axis direction, and a camera body. 1, and a lens control unit 5 of focus adjusting means for controlling the lens driving unit 4 while communicating with the camera 1.

  The camera body 1 receives subject light from a photographic optical system including a focus lens 3, and transmits a half mirror 6 that is transmitted to an image sensor 7 side, which will be described later, and reflected to a phase difference AF sensor unit 9 side. And an image sensor 7 that receives the transmitted light from the half mirror 6 and converts the formed subject image into an electrical signal, and a phase difference AF sensor unit 9 that receives the reflected light of the subject light from the half mirror 6. And built-in. Further, the camera body 1 includes an LCD panel 10 for an electronic view finder having a built-in backlight, a finder optical system 11 for observing the LCD panel 10, and a first focus detection unit that applies a phase difference AF method. A first focus detection unit 12, an image processing unit 13 that processes an output signal of the image sensor 7, an LCD panel 10 that displays an image based on finder image data generated by the image processing unit 13, and an LCD panel 10 A finder optical system 11 for observing a finder image displayed on the screen, a second focus detection unit 14 which is a second focus detection unit to which an imager AF (contrast AF) method is applied, and the entire camera body 1 are controlled. The release signal (1RSW of the first stage) by the control unit 16 composed of a CPU and the like and the release button depressing operation It incorporates a release switch 18 No.) and outputs an imaging instruction signal to the second stage of the release signal (2RSW signal).

  The image processing unit 13 processes the output signal of the image sensor 7 to extract image contrast information, and performs white balance processing, Y processing, color matrix processing, and the like to obtain captured image data and viewfinder image data. Generate.

  The first focus detection unit 12 detects the phase difference of the subject image from the output of the phase difference AF sensor unit 9 and calculates a defocus amount.

  The second focus detection unit 14 determines the history of contrast information obtained by the image processing unit 13 based on the imaging signal of the imaging device 7 and outputs a focus evaluation value.

  The control unit 16 further includes a focus adjustment control unit that controls the focus adjustment drive of the focus lens 3 via the lens control unit 5 and the periodicity of the subject image data based on the detection result of the first focus detection unit 12. It incorporates periodic pattern determination means for determining the pattern.

  In the digital camera 20 of the present embodiment having the above-described configuration, when the first stage of the release switch 18 is turned on in response to pressing of the release button after the power is turned on, the phase difference AF sensor unit 9 and the first focus detection unit 12 and the focusing process by the imager AF by the second focus detection unit 14 based on the subject image data taken in from the image sensor 7 is executed. When the second stage is turned on, an imaging signal of the subject is taken in via the imaging device 7, and the imaging signal is converted into imaging data of the subject and stored in a non-volatile memory (not shown) or the like. .

  The focusing process by the above-described phase difference AF and imager AF in the digital camera 20 is performed by a focus adjustment device. First, coarse adjustment of focus adjustment is performed by the phase difference AF, and then fine adjustment of final focus adjustment is performed by the imager AF. The object image has a periodic pattern by the phase difference AF. If it is determined that the pattern is a periodic pattern, focus adjustment is performed only by the imager AF.

  The focus detection areas (areas) on the field frame in the first focus detection unit 12 for phase difference AF and the second focus detection unit 14 for imager AF are set in advance so as to coincide with each other.

Here, the principle of phase difference detection in the phase difference AF by the first focus detection unit 12 and the periodic pattern determination method by phase difference detection will be described with reference to FIGS.
FIG. 2 is a block diagram showing the basic structure of the phase difference AF sensor unit built in the camera body of FIG. FIG. 3 is a block configuration diagram of a portion related to phase difference detection between the photoelectric conversion element array and the first focus detection unit of the phase difference AF sensor unit of FIG. FIG. 4 shows an output waveform (a) of the A image and B image on the photoelectric conversion element array, a waveform (b) in a state where the waveform is shifted by one bit at a time, and A, It is a figure which shows the waveform (c) in the state in which B image matched most. FIG. 5 is a diagram illustrating an example of the correlation between the phase difference amount i obtained by the first focus detection unit and the correlation function F (i). FIG. 6 is a diagram showing a striped subject image which is an ideal periodic pattern. FIG. 7 is a diagram illustrating a change in the correlation function F (i) with respect to the subject image in FIG. FIG. 8 is a diagram illustrating an example in the case where a plurality of minimum values exist in the correlation function F (i).

  As shown in FIG. 2, the basic configuration of the phase difference AF sensor unit 9 built in the camera body 1 is that a field mask 31 and a capacitor are provided in the vicinity of an assumed imaging plane on which a subject image is formed by a photographing lens including the focus lens 3. A lens 32 is disposed, and porous aperture masks 33A and B and secondary imaging lenses 34A and B are disposed behind the lens 32, and a plurality of photoelectric conversion element arrays 35A and B which are AF sensors 35 are disposed behind the lens 32. It is. With this configuration, two subject images formed by light beams that have passed through two different pupil regions 36A and B on the focus lens 3 are re-imaged on different photoelectric conversion element arrays 35A and B, respectively. Focus detection is performed using the fact that the positional relationship changes depending on the focus state of the focus lens 3.

  The photoelectric conversion element arrays 35A and 35B shown in FIG. 3 are the photoelectric conversion element arrays shown in FIG. 2, and are included in the phase difference AF sensor unit 9 (FIG. 1). The A / D converter 41 included in the first focus detection unit 12 (FIG. 1) converts an analog output from each pixel in the photoelectric conversion element arrays 35A and 35B into a digital signal. The calculation unit 42 performs various calculations described later based on the digital signal.

  The phase difference that is the relative positional relationship between the two subject images described above can be obtained by obtaining the correlation. The area S of the region where the two subject images (A image and B image) shown in the output waveform (a) of FIG. 4 do not overlap is the sum of the absolute values of the differences between the corresponding pixels of the A image and B image. The image (A image in this example) is shifted by one pixel (1 bit) of the photoelectric conversion element, and the minimum value of the area S is obtained. As shown in the output waveform (c) of FIG. 4, if the A image and the B image coincide with each other, the minimum value will inevitably become the minimum value. It becomes a certain phase difference. In these focus detection apparatuses, the distance between the centers of gravity of the two pupil regions becomes the base line length in triangulation, and the defocus amount of the photographing lens can be obtained based on the phase difference that is the relative shift amount on the photoelectric conversion element.

  Further, a phase difference between the two images is obtained by a calculation unit 42 including a microcomputer built in the first focus detection unit 12, and the focus lens 3 is controlled based on the phase difference.

で与えられる。 The output values of the A / D converted photoelectric conversion element arrays 35A and B are respectively L (1), L (2),..., L (n) and R (1), R (2),. Let R (n) be a correlation function F as an evaluation value indicating the degree of coincidence of images with respect to the relative shift amount (referred to as phase difference amount i) of two images as a phase difference on j pixel pitch (pixel × pitch p). (I)

Given in.

  If the two images on the photoelectric conversion element arrays 35A and 35B are relatively displaced by k pixel pitches, F (k) = 0. However, since the output value of each pixel column is hardly the same as the shape of the image signal from the two photoelectric conversion element columns due to the influence of pixel noise or the like, normally, F (k)> 0.

  As described above, the data of i and F (i) is discrete data, but FIG. 5 shows F (i) as a continuous graph for convenience. After obtaining the minimum value of F (i) within a predetermined range of i, interpolation calculation is performed using correlation function values before and after the minimum value in order to perform highly accurate detection.

  In the phase difference detection method described above, there are a plurality of minimum values when focus detection is performed on a subject having a periodic pattern such as a striped pattern. FIG. 6 shows an ideal striped pattern. When the correlation function F (i) given by the equation (1) is calculated for a subject having such a periodic pattern, i changes by the pitch of the striped pattern. The correlation function value is the same, and the correlation function itself becomes repeated data.

  Accordingly, as shown in FIG. 7, a plurality of minimum values k1, k2, k3, k4 appear, and it cannot be determined which of these corresponds to a true phase difference. Actually, numerical differences occur in multiple minimum values due to stripe pattern variations, pixel variations, noise, etc., so if you simply select the minimum value, it will be detected incorrectly, and the result will be in focus. End up with no photos.

  As a method of determining the periodic pattern in the focus adjustment apparatus of the present embodiment, when there are a plurality of minimum values, as shown in FIG. 8, the minimum value Fmin1 among the plurality of minimum values is The first minimum value Fmin2 is obtained, and the difference ΔFmin (= Fmin2−Fminl) is compared with a predetermined determination value Z. If ΔFmin <Z, the periodic pattern is determined.

The photographing processing operation including the focus adjustment in the digital camera 20 will be described with reference to the flowcharts of FIGS.
FIG. 9 is a flowchart of the photographing process in the digital camera 20. FIG. 10 is a flowchart of a periodic pattern determination process of a subroutine called during the phase difference detection process in the photographing process of FIG. FIG. 11 is a flowchart of the imager AF process of a subroutine called during the photographing process of FIG.

  In the digital camera 20, the photographing process shown in FIG. 9 is started under the control of the control unit 16 when the power is turned on. After the power switch (not shown) is turned on, the first-stage switch (1RSW) of the release switch 18 is turned on by half-pressing the release button in step S1, and waits for an instruction to prepare for photographing. When the first stage switch is turned on, the process proceeds to step S2.

  In step S2, the phase difference detection of the subject image signal by the phase difference AF sensor unit 9 is executed. Specifically, an output signal from the phase difference AF sensor unit 9 is acquired, and the defocus amount is calculated by the first focus detection unit 12. It is also determined at the same time whether or not the phase difference can be detected, whether the detection is reliable, whether the subject image is a periodic pattern (by a periodic pattern determination process in a subroutine of FIG. 10 described later), and the like.

  In step S3, it is determined with reference to a flag or the like whether or not a highly reliable defocus amount is obtained in the phase difference detection, in other words, whether or not detection is possible. If it is detectable, the process proceeds to step S4, and if not detectable, the process proceeds to step S8.

  In step S4, it is determined with reference to a flag whether or not the subject image is a periodic pattern. If it is a periodic pattern, the process proceeds to step S8, and if it is not a periodic pattern, the process proceeds to step S5.

  In step S5, it is determined whether or not the detected defocus amount is within a predetermined range. This predetermined range is a range of numerical values determined in advance so that the focusing operation is performed with sufficiently high accuracy and high speed by the imager AF within this range. If it is not within the predetermined range, the process proceeds to step S6, and if it is within the predetermined range, the process proceeds to step S8.

  In step S6, the driving amount of the focus lens 3 for obtaining the in-focus state is calculated from the obtained defocus amount. In step S7, lens driving is performed. That is, the calculated lens driving amount is transmitted to the lens control unit 5 in the interchangeable lens 2, and the lens control unit 5 controls the lens driving unit 4 to drive the focus lens 3 and returns to step S2.

  If the process proceeds to step S8, the subroutine imager AF process is called to execute the imager AF. The contents of the imager AF process will be described later in detail with reference to the flowchart of FIG.

  In step S9, it is determined with reference to a flag or the like whether or not an in-focus state has been obtained as a result of the imager AF operation. If the in-focus state is obtained, the process proceeds to step S10. If the in-focus state cannot be obtained, the process proceeds to step S11.

  In step S <b> 10, an in-focus display indicating that the in-focus state has been achieved is displayed on the LCD panel 10. In step S11, an out-of-focus display indicating the out-of-focus state is performed.

  In step S12, the second switch (2RSW on) of the release switch 18 is turned on by fully pressing the release button after focusing according to the above procedure, and when shooting is instructed, shooting according to a normal shooting sequence is performed. After photographing is completed, the process returns to step S1.

  Here, the periodic pattern determination process called and executed as a subroutine in the phase detection process of step S2 will be described with reference to the flowchart of FIG.

  First, in step S21, a periodic pattern determination flag is initialized. Subsequently, in step S22, it is determined whether or not there are a plurality of minimum values of the correlation function F (i) described above. If there are a plurality of minimum values, the process proceeds to step S23.

  In step S23, the value of ΔFmin (= Fmin2−Fminl) described above is checked. If ΔFmin <Z, the process proceeds to step S24. If ΔFmin <Z, the process ends.

  In step S24, it is determined that the subject image includes a periodic pattern, the periodic pattern flag is set, and this routine ends.

  Next, the imager AF process of the subroutine called in step S8 will be described with reference to the flowchart of FIG.

  First, in step S31, it is determined whether or not the phase difference AF has been executed. If phase difference AF is executed, the process proceeds to step S32. If not executed, that is, if the phase difference AF is not detectable as a result of executing phase difference AF (in the case of No in step S3 in FIG. 9) and periodicity If it is a pattern (Yes in step S4 in FIG. 9), the process proceeds to step S33.

  In step S32, the scan range of the imager AF is set. This scan range is set to ΔX before and after the current position of the focus lens 3 as the center position. ΔX is a scan range that is determined in advance so that the focusing operation is performed with sufficiently high accuracy and high speed by the imager AF, and is stored in the memory in the interchangeable lens 2 and read and used. This ΔX is appropriately changed according to parameters such as the focal length of the interchangeable lens 2, the position (distance) of the focus lens 3, and the reliability of phase difference detection.

  In step S33, the scan range is set to the entire focus lens movable range, that is, from the closest distance to infinity. This is because the phase difference AF has not been executed in advance, and therefore there is a high possibility that it is not located near the in-focus state. Thereafter, the process proceeds to step S34.

  In step S34, the focus lens 3 is moved by controlling the lens driving unit 4 via the lens control unit 5 from the current position to the side closer to the end of the scan range.

  In step S35, the evaluation value of the imager AF is taken in at the moved position. In step S36, the evaluation value acquired in step S35 and the position of the focus lens 3 are stored as an evaluation value history.

  In step S37, the evaluation value history is referred to, and it is confirmed whether the focal point (peak value of the evaluation value) has passed. If it has passed, the process proceeds to step S42, and if not, the process proceeds to step S38.

  In step S38, the entire scan range set in step S32 or S33 is scanned, and it is determined whether or not it is finished. If it is finished, the process proceeds to step S40. If there is an area to be scanned, the process proceeds to step S39. The position of the focus lens 3 is updated by controlling the lens driving unit 4. After the update, the process returns to step S35.

  The peak search of the imager AF is performed by repeating the processes in steps S35 to S39.

  When the process proceeds to step S42, the focus lens 3 is moved by the lens driving unit 4 to the position indicating the peak position from the evaluation value history. In step S43, the peak evaluation value, which is the result of the imager AF, is stored and the process is terminated, and then the process returns to the main routine.

  On the other hand, if it is determined in step S38 that the in-focus point (peak value) has not been obtained in the determination in step S38 as described above and the process in the scan range has been completed (NO in step S38), the process proceeds to step S40. The focus lens 3 is moved to the initial position of the scan range. In step S41, the fact that the imager AF cannot be detected is stored in a flag or the like, the process is terminated, and the process returns to the main routine.

  As described above, in the focus adjustment of the digital camera 20, the focus adjustment is roughly adjusted by the phase difference AF, and the focus adjustment is finely adjusted by the imager AF. When it is determined that the subject image has a periodic pattern, focus adjustment is performed by the imager AF.

  Whether or not the subject image is a periodic pattern is determined based on the state of the correlation function F (i) as shown in FIG. 7, but if it is determined simply that there are a plurality of minimum values, the following is determined. It is also possible to prevent a subject that can be detected from being judged undetectable. For example, there is a mixture of near and far subjects, but the main subject occupies most of the detection area, and other subjects have a small influence. In the present embodiment, as described above, when ΔFmin is smaller than the predetermined determination value Z, it is determined that the pattern is a periodic pattern.

  As described above, in the focus adjustment device that performs focus adjustment by combining the imager AF and the TTL phase difference AF, it is possible to detect erroneously when the subject has a periodic pattern by detecting whether or not the subject has the periodic pattern. Only the focus adjustment by the imager AF is performed without performing the TTL phase difference AF with high performance. Therefore, high focus adjustment accuracy can be obtained even for a subject having a periodic pattern.

  In this embodiment, when the pattern is not a periodic pattern, coarse adjustment is performed by phase difference AF and fine adjustment is performed by imager AF. However, the present invention is not limited to this, and focus adjustment is performed by phase difference AF. May be.

  Next, a digital camera incorporating the focus adjusting apparatus of the second embodiment of the present invention will be described with reference to FIGS.

  FIG. 12 is a schematic perspective view showing the configuration of the phase difference AF sensor unit applied to the digital camera of this embodiment. FIG. 13 is a flowchart of shooting processing in the digital camera of the present embodiment.

  The digital camera of the present embodiment has a configuration of a phase difference AF sensor unit 59 (FIG. 12) built in the camera body with respect to the digital camera 20 of the first embodiment and the focus by the first focus detection unit and the control unit. Adjustment action is different. Other configurations are the same as those of the digital camera 20 of the first embodiment.

  As shown in FIG. 12, the phase difference AF sensor unit 59 in the digital camera of this embodiment is focused on focus detection areas 56a, 56b, and 56c that are a plurality of detection areas set in the subject image shooting screen 56. Detect the adjustment status.

  The phase difference AF sensor unit 59 includes an AF sensor 55 and a focus detection optical system 50. The focus detection optical system 50 includes a field mask 51 disposed on the subject side, a plurality of condenser lenses 52, a diaphragm mask 53, and a plurality of sets of secondary imaging optical systems 54. The AF sensor 55 includes a plurality of photoelectric conversion element arrays 55a, 55b, and 55c, and its output data is input to the first focus detection unit 12.

  The light flux from the subject with respect to the plurality of focus detection areas set in the photographing screen is divided by the plurality of condenser lenses 52 and the secondary imaging optical system 54 corresponding to each focus detection area, and the photoelectric conversion element array 55a. , 55b, 55c, and focus detection is performed by the phase difference detection method.

  That is, the subject light in the focus detection area in the shooting screen passes through the shooting optical system including the focus lens 3 and enters the condenser lens 52 corresponding to each focus detection area. The light emitted from the contensor lens 52 passes through a pair of secondary imaging optical systems 54 arranged one by one corresponding to each focus detection area. Then, the two images formed by each pair of secondary imaging optical systems 54 are respectively formed on the corresponding photoelectric conversion element arrays 55a, 55b, and 55c.

  Image data for each photoelectric conversion element array is taken into the first focus detection unit 12 from the AF sensor 55.

  The first focus detection unit 12 calculates the phase difference amount from the light intensity distribution of the pair of images of each photoelectric conversion element array, calculates the defocus amount of each focus detection area, and outputs it to the control unit 16.

  Each area on the imaging area of the imaging element 7 corresponding to a plurality of focus detection areas in the imaging screen by the phase difference AF sensor unit 59 is adjusted and associated in advance in the manufacturing process.

  Then, the control unit 16 selects or processes one defocus amount by using a predetermined selection algorithm based on the defocus amount of the all focus detection area. For example, if the closest selection is made, the most defocus amount of the rear pin is adopted. Then, the control unit 16 transmits the defocus amount to the lens control unit 5.

  The lens control unit 5 calculates a lens driving amount based on the defocus amount, and the lens driving unit 4 drives the focus lens 3 in the interchangeable lens 2.

  Further, when a specific focus detection area is selected from the plurality of focus detection areas 56a, 56b, and 56c by operating an operation unit (not shown) by the photographer, the defocus amount can be obtained only for the selected focus detection area. That's fine.

  An imaging process including focus adjustment in the digital camera of this embodiment will be described with reference to the flowchart of FIG.

  The imaging process shown in FIG. 13 is started under the control of the control unit 16 when the power is turned on. When the power switch (not shown) is turned on, the first-stage switch (1RSW) of the release switch 18 is turned on by half-pressing the release button in step S51, and the process waits until an instruction for shooting preparation is instructed. When the first-stage switch is turned on, the process proceeds to step S52, and the phase difference detection in the all focus detection area is executed.

  Specifically, a signal is acquired from the phase difference AF sensor unit 59, and the defocus amount is calculated by the first focus detection unit 12. It is also determined whether or not the phase difference can be detected, whether the detection is reliable, whether the subject image is a periodic pattern, and the result is stored in a flag or the like for each detection area.

  In step S53, it is determined for all regions whether or not a highly reliable defocus amount is obtained in the phase difference detection, that is, whether or not it is detectable. If the entire area cannot be detected, the process proceeds to step S64. If there is a detectable region, the process proceeds to step S54.

  In step S54, it is determined for all regions where the phase difference can be detected by referring to a flag or the like as to whether or not the subject image is a periodic pattern. If the entire region in which the phase difference can be detected is a periodic pattern, the process proceeds to step S64. If there is an area that is not a periodic pattern, the process proceeds to step S55.

  In step S55, an area of the closest subject whose defocus amount is the rearmost pin is selected from an area that can be detected and is not a periodic pattern among all areas.

  In step S56, it is determined whether or not the selected defocus amount is within a predetermined range. The predetermined range is a numerical value determined in advance so that the focusing operation is performed with sufficiently high accuracy and high speed by the imager AF within this range. If it is not within the predetermined range, the process proceeds to step S57, and if it is within the predetermined range, the process proceeds to step S60.

  In step S57, the driving amount of the focus lens 3 for obtaining the in-focus state is calculated from the obtained defocus amount. In step S58, lens driving is performed. That is, the calculated lens driving amount is transmitted to the lens control unit 5 in the interchangeable lens 2, and the lens control unit 5 controls the lens driving unit 4 to drive the focus lens 3.

  In step S59, the phase difference is detected again for the selected region, and the process proceeds to step S57.

  As described above, the focus adjustment using the phase difference detection is performed until the region selected from the entire region falls within the predetermined defocus amount range.

  When the process proceeds to step S60, the subroutine imager AF is executed in the selected area, and the second focus detection unit 14 determines the focus evaluation value in the imaging area of the imaging device 7 corresponding to the selected focus detection area. Is calculated and output.

  The contents of the imager AF process in the subroutine are the same as those in the flowchart shown in FIG.

  In step S61, it is determined with reference to a flag or the like whether or not an in-focus state has been obtained as a result of the imager AF operation. If the in-focus state is obtained, the process proceeds to step S62.

  In step S62, an in-focus display indicating that the in-focus state is achieved is displayed on the LCD panel 10. In step S65, an out-of-focus display indicating non-focus is displayed on the LCD panel 10.

  After focusing in accordance with the above procedure in step S63, the second switch (2RSW on) of the release switch 18 is turned on by fully pressing the release button, and when shooting is instructed, shooting in the normal shooting sequence is performed. After shooting is completed, the process returns to step S51.

  When the process proceeds to step S64, imager AF is performed in the entire detection area. The content of the imager AF process is the same as the process of the flowchart of FIG. 3, and the lens position of the peak evaluation value is detected for all regions, and the peak evaluation value (lens position) on the closest side is selected. Set the focus lens position. In this way, the closest selection is performed.

  As described above, in the case of the digital camera according to the present embodiment, in the focus adjustment device that performs focus adjustment by combining the imager AF and the TTL phase difference AF, the subject has a periodic pattern when the subject has a plurality of focus detection areas. In the case of having a periodic pattern, the TTL phase difference AF is executed in a focus detection region that is not a periodic pattern, so that it is possible to avoid defocusing due to erroneous detection. When a periodic pattern is detected for the entire region, only the focus adjustment by the imager AF is performed for the entire region without performing the TTL phase difference AF that has a high possibility of erroneous detection. Therefore, high focus adjustment accuracy can be obtained even for a subject having a periodic pattern.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention at the stage of implementation. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  The focus adjustment device according to the present invention can be used as a focus adjustment device capable of obtaining high focusing accuracy even when the subject image has a periodic pattern.

It is a block block diagram of the digital camera which incorporates the focus adjustment apparatus of 1st embodiment of this invention. It is a block block diagram which shows the basic composition of the phase difference AF sensor unit incorporated in the camera body of FIG. It is a block block diagram of the part in connection with the phase difference detection of the photoelectric conversion element row | line | column of a phase difference AF sensor unit of FIG. 2, and a 1st focus detection part. The output waveform (a) of the A and B images on the photoelectric conversion element arrays 35A and 35B of the phase difference AF sensor unit of FIG. 2 and the waveform (b) and the A image in a state where the waveform is shifted by one bit at a time. It is a figure which shows the waveform (c) in the state in which A and B image matched most in the state which shifted. It is a figure which shows an example of the correlation of phase difference amount i calculated | required in the 1st focus detection part of FIG. 3, and correlation function F (i). It is a figure which shows the to-be-photographed subject image which is an ideal periodic pattern. It is a figure which shows the change of the correlation function F (i) in the 1st focus detection part of FIG. 3 with respect to the to-be-photographed object image of FIG. It is a figure which shows the example in case a some minimum value exists in the correlation function F (i) in the 1st focus detection part of FIG. It is a flowchart of the imaging | photography process in the digital camera of FIG. 10 is a flowchart of a periodic pattern determination process of a subroutine called during a phase difference detection process in the photographing process of FIG. 9. FIG. 10 is a flowchart of an imager AF process of a subroutine called during the photographing process of FIG. 9. FIG. It is a typical perspective view which shows the structure of the phase difference AF sensor unit applied to the digital camera of 2nd embodiment of this invention. It is a flowchart of the imaging | photography process in the digital camera of FIG.

Explanation of symbols

4 ... Lens drive unit (focus adjustment means)
5. Lens control unit (focus adjustment means)
12: First focus detection unit (first focus detection means)
14 ... second focus detection section (second focus detection means)
16: Control unit (control means, periodic pattern determination means)
56a, 56b, 56c
... Focus detection area (multiple detection areas)
F (i) ... correlation function (evaluation value)

Claims (5)

In a focus adjustment apparatus having a first focus detection unit that performs focus detection by a phase difference method and a second focus detection unit that performs focus detection by a contrast method,
Focus adjusting means for adjusting the focus of the lens based on the focus adjustment information;
A periodic pattern determination unit that determines whether or not the reflected light from the subject has a periodic pattern based on the focus detection information from the first focus detection unit;
Control means for controlling the focus adjustment means based on focus detection information from the second focus detection means when the periodic pattern determination means determines that the subject has a periodic pattern;
A focus adjusting apparatus comprising:   The periodic pattern determination means is a difference between the smallest first minimum value and the next smallest second minimum value among the minimum values calculated based on the focus detection information from the first focus detection means. 2. The focus adjustment apparatus according to claim 1, wherein when the value is smaller than a predetermined value, it is determined that the reflected light from the subject has a periodic pattern.   When the control unit determines that the subject does not have a periodic pattern by the periodic pattern determination unit, the control unit detects the focus detection information from the first focus detection unit and the second focus detection unit. The focus adjustment apparatus according to claim 1, wherein the focus adjustment operation is performed in combination with focus detection information. First focus detection means for detecting a focus state of a plurality of focus detection areas by a phase difference method;
Second focus detection means for detecting a focus state of a region corresponding to the plurality of focus detection regions by a contrast method;
Focus adjusting means for adjusting the focus of the lens based on the focus adjustment information;
A periodic pattern for determining whether all of the detectable focus detection areas of the plurality of focus detection areas have a periodic pattern based on focus detection information from the first focus detection means. A determination means;
When it is determined by the periodic pattern determination means that all of the detectable focus detection areas have a periodic pattern, the focus from all areas output from the second focus detection means The focus adjustment unit is controlled based on detection information, and when it is determined that at least one of the detectable focus detection regions does not have a periodic pattern, the focus from the first focus detection unit is Control means for controlling the focus adjustment means by combining detection information and focus detection information from the second focus detection means;
A focus adjusting apparatus comprising:   The periodic pattern determination unit is configured to perform calculation based on focus detection information of each focus detection region that can be detected from the plurality of focus detection regions output from the first focus detection unit, When the difference between the smallest first minimum value and the next smallest second minimum value in the region that has become smaller than the predetermined value, the region has a periodic pattern The focus adjustment apparatus according to claim 4, wherein the focus adjustment apparatus is determined.

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