JP6659100B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging device that performs position control of a focus lens based on a signal from an imaging device.

  2. Description of the Related Art In recent years, advanced functions of an image sensor have been developed, and systems capable of detecting a so-called phase difference AF signal with the image sensor have been proposed. Conventionally, proposals have been made to utilize information on an imaging surface for focus detection, and Patent Literature 1 proposes to adjust an optical system (focus adjustment) by feeding back a focus state.

  On the other hand, proposals have been made to adjust the optical system according to changes in the zoom state of the optical system. Patent Literature 2 proposes maintaining a focused state by driving a focus lens according to a change in a zoom state of an optical system.

JP-A-55-40447 JP-A-52-114321

  However, Patent Literature 1 does not describe a process when an error such as a decrease in coincidence between two images in phase difference detection or a sudden occurrence of luminance saturation occurs in a case where the image is used in a field. Therefore, there is a problem that the system is likely to be unstable.

  Further, in Patent Literature 2, since the focus lens is driven according to a change in the zoom state without detecting the focus state of the image, there is a problem that errors are likely to be accumulated in the positioning of the lens.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an imaging apparatus capable of stably performing position control of a focus lens even when an error occurs in a signal for focus detection. To provide.

An imaging apparatus according to the present invention includes a focus detection unit that detects a focus state of a photographic optical system, a zoom position detection unit that detects a zoom position of the photographic optical system, and a position of a focus lens of the photographic optical system. Focus position detecting means, adjusting means for adjusting the position of the focus lens of the photographing optical system, and trajectory of the focus lens for keeping focusing on an object at the same distance according to the change of the zoom position. A storage unit for storing, a determination unit for determining the reliability of the output of the focus detection unit, and a control for controlling the position of the focus lens according to the change in the zoom position based on the output of the focus detection unit. 1 and the focus corresponding to a change in the zoom position based on the information on the trajectory of the focus lens stored in the storage means. A second operation for controlling the position of Surenzu, and a control means for switching in response to determination of said determination means, said control means, said determining means is reliable in the output of the focus detection unit When the determination is made, the first operation is performed. When the determination unit determines that the output of the focus detection unit is not reliable, the second operation is performed and the second operation is performed. In this case, the position of the subject is estimated based on a plurality of focus state detection results detected by the focus detection unit before the timing at which the determination unit determines that the output of the focus detection unit is unreliable. And controlling the position of the focus lens on the basis of the estimated position of the subject and the information of the trajectory of the focus lens stored in the storage means .

  According to the present invention, it is possible to provide an imaging apparatus capable of stably controlling the position of a focus lens even when an error occurs in a signal for focus detection.

FIG. 1 is a diagram illustrating a configuration of a camera system that is an embodiment of an imaging device of the present invention. FIG. 1 is a block diagram illustrating a main part of an imaging device according to an embodiment. FIG. 3 is a diagram illustrating a basic zoom tracking operation. FIG. 7 is a diagram illustrating a zoom tracking operation when an error occurs. The figure explaining another zoom tracking operation | movement. FIG. 3 is a diagram illustrating a focus detection unit. FIG. 4 is a diagram illustrating a scene in which an error in focus detection is likely to occur.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of a camera system which is an embodiment of the imaging apparatus of the present invention. FIG. 1 (a) is a central sectional view, and FIG. 1 (b) is a block diagram showing an electrical configuration. .

  In FIG. 1A, a camera system 100 includes a camera body 1 and a lens unit 2 that is detachably attached to the camera body 1. The camera body 1 includes an imaging element 6, a mechanical shutter 14, a rear display unit 9a, an electronic viewfinder 9b, and an electrical contact 11 with the lens unit 2. Further, the lens unit 2 is configured such that an imaging optical system 3 including a plurality of lenses is arranged along the optical axis 4. The lens unit 2 includes a lens position sensor 15 that detects a position of each lens group and outputs a position detection signal of each lens group.

  In FIG. 1B, the camera body 1 includes, as electrical blocks, a camera system control circuit 5, an image processing unit 7, a memory unit 8, an operation detection unit 10, a display unit 9 (a back display unit 9a, an electronic viewfinder 9b). Including). The lens unit 2 includes a lens system control circuit 12 and a lens driving unit 13 as electric blocks.

  The camera system 100 including the camera body 1 and the lens unit 2 is roughly composed of an imaging unit, an image processing unit, a recording / reproducing unit, and a control unit. The imaging unit includes a photographing optical system 3 and an imaging element 6, and the image processing unit includes an image processing unit 7. The recording / reproducing unit includes a memory unit 8 and a display unit 9, and the control unit includes a camera system control circuit 5, an operation detecting unit 10, a lens system control circuit 12, a lens driving unit 13, and a lens position sensor 15. . The camera system control circuit 5 controls the entire system based on signals obtained from the camera body 1 and the lens unit 2. The lens driving unit 13 drives the focus lens 31, the shake correction lens, the diaphragm, and the like. The lens position sensor 15 detects the position of each lens group, such as a zoom lens group and a focus lens group, that constitute the imaging optical system 3 (zoom position detection, focus position detection). The lens position sensor 15 has an accuracy suitable for performing zoom tracking described later.

  The imaging unit forms light from an object on the imaging surface of the imaging device 6 via the imaging optical system 3. Since the focus evaluation amount and the appropriate exposure amount can be obtained from the signal of the imaging device 6, the imaging optical system 3 is adjusted based on these signals, so that the imaging device 6 is exposed with an appropriate amount of object light. In addition, a subject image can be formed near the image sensor 6.

  The image processing unit 7 includes an A / D converter, a white balance adjustment circuit, a gamma correction circuit, an interpolation operation circuit, and the like, and generates an image for recording. The color interpolation processing unit is provided in the image processing unit 7, and performs color interpolation (demosaicing) processing on the signals in the Bayer array to generate a color image. Further, the image processing unit 7 compresses an image, a moving image, a sound, and the like by using a predetermined method. Further, the image processing unit 7 generates a blur detection signal based on a comparison between a plurality of images obtained from the image sensor 6. This operation will be described later. The memory unit 8 stores image data and the like. The camera system control circuit 5 outputs image data to the memory unit 8 and sends the image data to the display unit 9 to display an image to be presented to the user.

  The camera system control circuit 5 generates and outputs a timing signal at the time of imaging. The image pickup unit, the image processing unit, and the recording / reproducing unit are respectively controlled in response to an external operation. For example, the operation detection unit 10 detects pressing of a shutter release button (not shown), and controls driving of the image sensor 6, operation of the image processing unit 7, compression processing, and the like. Further, it controls display of an image by the display unit 9. The rear display unit 9a is a touch panel, and is connected to the operation detection unit 10. The camera body 1 has a mechanical shutter 14, and can control the exposure of the image sensor 6 according to a command from the camera system control circuit 5.

  Next, the adjustment operation of the photographing optical system 3 will be described. An image processing unit 7 is connected to the camera system control circuit 5, and obtains a focus position and an aperture position based on a signal from the image sensor 6. The camera system control circuit 5 issues a command to the lens system control circuit 12 via the electric contact 11, and the lens system control circuit 12 controls the lens driving unit 13. Further, in a mode in which camera shake correction is performed, the camera shake correction lens is controlled via the lens driving unit 13 based on a signal obtained from an image sensor described later.

  In the memory unit 8, a locus of the focus lens with respect to the zoom change (details will be described later) is recorded. Further, the camera system control circuit 5 calculates the distance of the subject from the information of the memory unit 8 and the information of the lens position sensor 15, and calculates an appropriate position of the focus lens when a zoom change occurs. This is called an electronic cam.

  Further, as described later, a plurality of images from different viewpoints necessary for the phase difference AF are output from the image sensor 6, and the image processing unit 7 performs a so-called correlation operation. That is, focus detection is performed by the image sensor 6 and the image processing unit 7. Then, the position control of the focus lens is performed by the camera system control circuit 5, the lens system control circuit 12, and the lens driving unit 13.

  FIG. 2 is a diagram illustrating a main part of the camera system according to the present embodiment. 2, the focus detection unit 21 is provided in the image processing unit 7, and the electronic cam calculation unit 22 and the changeover switch 23 are provided in the camera system control circuit 5. The reliability determination unit 24 controls the operation of the changeover switch 23. The focus detection unit 21 detects information about the focus (whether or not the area in which the main subject is present is in focus, and if not, the direction and amount thereof).

  The focus detection unit 21 in the image processing unit 7 obtains information on focus based on a signal output from the image sensor 6. If the reliability determination unit 24 determines that the information detected by the focus detection unit 21 is appropriate, the changeover switch is set to the state shown in FIG. Is performed. Specifically, feedback control is performed on the focus lens 31 so that the main subject is kept in focus. The lens system control circuit 12 outputs a command for performing this feedback control to the lens driving unit 13.

  On the other hand, when the reliability determination unit 24 determines that the signal obtained by the focus detection unit 21 is not appropriate, the changeover switch 23 is switched to be connected to the electronic cam calculation unit 22. Then, the position of the focus lens 31 is controlled based on a signal from the electronic cam calculation unit 22. Specifically, a command is issued from the lens system control circuit 12 to the lens driving unit 13 to maintain the focus state immediately before regardless of the state of the subject. When there is no change in the zoom state, the focus lens remains stopped, and when there is a change in the zoom state, control called zoom tracking is performed. The zoom tracking operation will be described later.

  The electronic cam calculation unit 22 acquires the positions of the focus lens and the zoom lens from the lens position sensor 15 and obtains information on the focus state and the zoom state. Further, with reference to the memory unit 8, the object distance corresponding to the case where the position of the focus lens and the position of the zoom lens are at the position indicated by the lens position sensor 15 is calculated. When the zoom state changes as described later, it is necessary to appropriately drive the focus lens in order to maintain the focus state on the subject at the same distance. This operation is called a zoom tracking operation.

  Next, a method in which the reliability determination unit 24 determines the suitability of the signal obtained by the focus detection unit 21 will be described. When a signal required for phase difference AF is obtained from the image sensor 6 as described later, the degree of coincidence of the two images in the correlation calculation can be used for determining reliability. As another method, when contrast AF is used, a signal in which the amount of change in contrast is made dimensionless by luminance can be used. As still another method, the position of the subject on the object side can be observed in time series, and its continuity can be used. In each of the above-described determination methods, when the degree of coincidence between the two images is low, when the change in the contrast signal is small, and when the moving speed of the subject is too fast (when the focus position fluctuates due to conflict between perspectives), focus is determined. It is determined that it is inappropriate to use the signal detected by the detection unit 21. Then, the control is switched to the control based on the signal of the electronic cam calculation unit 22. On the other hand, if it is determined that the focus detection unit 21 has properly performed the detection, the appropriate focus control that follows the movement of the subject can be performed by using the signal indicating the focus state from the image sensor 6. Done.

  Next, a basic operation of zoom tracking will be described with reference to FIG. FIG. 3A is a diagram for explaining the concept of the zoom tracking operation, FIG. 3B is a diagram showing how the zoom tracking is performed on a subject whose distance does not change, and FIG. 3C is a subject whose distance changes. FIG. 9 is a diagram illustrating a state in which zoom tracking is performed on the image.

  In FIG. 3, the horizontal axis indicates the zoom position, the left side indicates the wide angle (WIDE) side, and the right side indicates the telephoto (TELE) side. The vertical axis indicates the position of the focus lens, and the lower side indicates the direction in which the focus lens approaches the image plane, and the upper side indicates the direction in which the focus lens approaches the subject. A plurality of curves shown in FIGS. 3A, 3B, and 3C represent a zoom position and a focus for an object at an object distance of 0.5 m, 1.0 m, 3.0 m, and infinity, respectively. The correspondence of the lens position is shown.

  As shown in FIG. 3, in order to focus on an object at the same distance, it is necessary to move the position of the focus lens according to the zoom position. Information on this curve is stored in the memory unit 8. The electronic cam calculation unit 22 calculates the amount by which the focus lens 31 is moved so as not to change the distance of the photographing optical system 3 to the object-side surface at a position conjugate with the image sensor 6 with respect to a zoom change. .

  In FIG. 3, reference numeral 30 denotes a zoom start point, reference numeral 40 denotes a zoom end point, and reference numeral 31 denotes a point indicating a state in which a subject at a distance of 3.0 m at the zoom position 30 is in focus. Reference numeral 41 denotes a point indicating a state in which a subject at a distance of 3.0 m in the zoom state 40 is in focus.

  The basic operation of zoom tracking will be further described with reference to FIG. Consider a case where the zoom lens transitions from the zoom position 30 to the zoom position 40 when the subject is at a position 3.0 m from the imaging device. Although FIG. 3 does not express the concept of time, it is assumed here that the transition from the zoom position 30 to the zoom position 40 is made in a time series. When the object at 3.0 m is in focus at the zoom position 30, the focus lens exists at the position indicated by 31. Here, assuming that the zoom position is changed to 40 while the focus lens is stopped, the state changes along arrow 32 in FIG. Since the state 33 is located between the object distance of 3.0 m and infinity, the state is in focus on an object farther than 3.0 m. That is, the focus of the subject of 3.0 m is out of focus. In order to focus on a 3.0 m object at the zoom position 40, it is necessary to move the focus lens to the position indicated by 41.

  In the example of FIG. 3A, in order to make the description easy to understand, it has been described that the state is largely moved in the zoom direction, and the state is shifted to the state 41 after reaching the state 33. However, in practice, it is preferable to control the defocus amount generated in the state 33 and the state 41 to be equal to or less than the allowable value. Therefore, it is desirable that the lens position sensor 15 has a resolution such that the state 33 and the state 41 in FIG.

  In this embodiment, performing focus compensation accompanying a zoom operation by some method is called zoom tracking. As a first tracking method, there is a zoom tracking method in which a signal is fed back using a focus detection sensor to perform zoom tracking. As a second tracking method, there is a method of performing zoom tracking based on the positions of a focus lens and a zoom lens.

  In the present embodiment, a method of appropriately using the first tracking method and the second tracking method is used. Since the first tracking method feeds back a signal of the focus detection sensor (for example, a detection signal of the phase difference AF), there are advantages that errors do not accumulate and a moving subject can be easily followed. There are problems such as malfunctioning when improper. On the other hand, the second tracking method has an advantage that the system configuration is easy because it is based on the signal of the position sensor. However, since the focus position of the final image is not used, errors such as positioning of the sensor and the lens are required. There is a problem that tends to accumulate. In the present embodiment, in order to provide a high-quality image, while utilizing the advantages of the first tracking method, the disadvantages are compensated for by appropriately using the second tracking method.

  FIG. 3B is a diagram illustrating a state in which zoom tracking is appropriately performed on a subject whose distance does not change. In the first tracking method, the zoom operation is performed while the focus state is always in the in-focus state (transition from the zoom position 30 to the zoom position 40), so that the state changes from 31 → 34 → 35 →. , An appropriate zoom tracking operation is performed. On the other hand, in the second tracking method, a change in the zoom state is detected by the zoom sensor, and the current position of the focus lens is detected. In accordance with the change in the zoom position, the focus lens is controlled so as to focus on a subject at the same distance, that is, along a curve indicating that the subject at the same distance is in focus. As a result, an appropriate zoom tracking operation is performed.

  FIG. 3C is a diagram illustrating a state in which zoom tracking is performed on a subject whose distance changes. Since the subject distance changes as will be described later, this corresponds to a case where zoom tracking and focusing are performed simultaneously instead of simple zoom tracking. In the first tracking method, as in the example of FIG. 3B, the zoom operation is performed while always keeping the subject in focus (transition from the zoom position 30 to the zoom position 40). The state changes from 31 → 36 → 37 →... → 42, and an appropriate zoom tracking operation is performed. On the other hand, in the second tracking method, since an attempt is made to focus on an object at the same distance, if the method is simply applied, the state does not transition to the state 42 as shown in FIG. However, the control as shown in FIG. 3C is also possible by performing the AF (autofocus) at an appropriate timing during the zoom tracking to change the tracking curve. As a result, an appropriate zoom tracking operation is performed.

  As described with reference to FIG. 3, in the zoom tracking, if control is performed based on information regarding the image formation state of the optical system (focus detection information or the like), simple control (always in an in-focus state) is performed. An appropriate operation can be performed on a moving subject. On the other hand, an advanced process called focus detection needs to be performed, so that an error may occur. This embodiment solves this problem.

  The operation of the present embodiment and its effects will be described with reference to FIG. FIG. 4 is a graph using the same notation as FIG. In FIG. 4, components having the same meaning as in FIG. 3 are given the same numbers. FIG. 4 is a diagram illustrating a case where an error occurs during zoom tracking of a subject that is not moving. Although errors that are likely to occur will be described later, phase difference AF (autofocus) includes a case where the degree of coincidence between two images is reduced and image coincidence is determined between subjects that should not be dealt with. .

  In FIG. 4, reference numeral 50 denotes a zoom position at which focus detection becomes inappropriate, 51 denotes a focus detection signal obtained inappropriately, and 51a denotes a state used in place of 51. It is assumed that focus detection has failed at the zoom position 50 in FIG. 4A and data indicated by 51 is obtained. That is, it is assumed that a focus detection result indicating that the subject distance has moved to the position at infinity at the zoom position 50 even though the subject has not moved. If the position control of the focus lens is performed as it is, the state changes from 31 → 34 → 51 →... → 41, and the focus state changes drastically on the way, resulting in an image of low quality.

  When the focus detection result becomes unstable, results such as a low degree of coincidence between the two images, a small change in the contrast signal, and a too fast moving speed of the subject are obtained as described above. Therefore, when the reliability determination unit 24 determines that the calculation result 51 at the zoom position 50 is inappropriate, zoom tracking is performed based on the output of the electronic cam calculation unit 22. That is, with reference to the immediately preceding state 34, the subject distance is obtained from the focus position and zoom position at this time. Assuming that the subject distance has not changed even at the zoom position 50, the position of the focus lens is determined, and the state transits to the state 51a. That is, as shown in FIG. 4B, the state transits from 31 → 34 → 51a →. In this way, smooth focus control is performed. Even when an error occurs, appropriate lens control is performed, and a high-quality image can be stably obtained.

  Next, another example will be described with reference to FIG. FIG. 5 is a graph using the same notation as in FIGS. In FIG. 5, those having the same meanings as in FIGS. 3 and 4 are given the same numbers.

  FIG. 5A is a diagram showing a state of processing when the distance to the subject changes after an error has occurred, and FIG. 5B shows a state in which zoom tracking is performed on a moving subject. FIG. 6 is a diagram illustrating a case where an error has occurred. FIG. 5 illustrates what kind of control is performed using signals before and after the occurrence of an error. Here, although FIG. 5 is a graph that does not express the concept of time, description will be made assuming that the zoom operation is performed at a constant speed, and the horizontal axis in the zoom direction also corresponds to time.

  The example of FIG. 5A is a diagram illustrating a case where the subject moves to 1.0 m at the next timing after an error occurs in the zoom state 50. In FIG. 5 (a), in order to make the explanation easy to understand, the sampling is moved from 3.0 m to 1.0 m in one sampling. However, this can be said to be very fast as the moving speed of a general subject. . For the sake of simplicity, it is merely such a value that the description of the case where the distance to the subject has changed before and after the occurrence of the error is easy to understand.

  In FIG. 5A, it is assumed that the subject distance changes at the timing next to the occurrence of the error and the focus states 52 and 53 are obtained. In the operation of the present embodiment, as described with reference to FIG. 4, with reference to the state 34 immediately before the error, it is assumed that the subject distance has not changed even at the zoom position 50, and the position 51a of the focus lens is changed. Determine. Next, when the subject distance is correctly obtained, the subject distance has changed to 1.0 m. At this time, if the state is suddenly changed from 51a to 52, the focus change becomes too sharp, resulting in an image of low quality.

  Therefore, when the focus lens is controlled by the signal of the electronic cam calculation unit 22 at the time of occurrence of the error and then the control is switched to the control of the focus detection unit 21, the signal of the lens position sensor 15 is also added to the signal of the focus detection unit 21. To control the focus lens. More specifically, the difference from 51a to 52 is filled with several sampling times while referring to the lens position sensor 15. As another method, the movement amount per sampling may be limited. In the example of FIG. 5A, instead of transitioning to the state 52 after the state 51a, a point 52a that is not too far from the current focus lens position obtained from the output of the lens position sensor 15 is set, and the state transits to this state. I do. When the state 53 is detected, the state transits to the state 53a. In the example of FIG. 5A, the state changes from 31 to 34 to 51a to 52a to 53a to 41.

  The example of FIG. 5B is a case where the subject is moving from 3.0 m to 1.0 m when an error occurs at the zoom position 50. The fact that the subject is moving can be known from the state before the error occurred. Therefore, when the focus lens is controlled by the signal of the electronic cam calculation unit 22, the focus lens is controlled by using a plurality of signals of the immediately preceding focus detection unit 21 in addition to the signal of the electronic cam calculation unit 22. To Specifically, when the state changes from 31 to 54, it is understood that the subject is approaching. In order to determine the movement of the subject, a plurality of signals from the immediately preceding focus detection unit 21 may be used. Estimate the position of the subject at the zoom position 50 where the error occurred (for example, using a method of estimating the position assuming that the object is moving at a constant speed), and adjust the position of the focus lens so that the position is in focus. Control. In the example of FIG. 5B, the transition is performed in the order of 31 → 54 → 51b →.

  4 and 5 illustrate the case where an error occurs during the zoom operation, but there is no problem even if the operation of the present embodiment is performed when the zoom operation is not being performed. In other words, the same effect is obtained that the focus state does not change drastically on the way due to an error and a low-quality image is avoided only by not performing the zoom tracking operation. That is, there is no need to divide the case where the operation is performed only during the zoom operation.

  Next, the configuration of the image sensor 6 that supplies a signal to the focus detection unit 21 and the operation of the image processing unit 7 will be described with reference to FIG. The example of FIG. 6 shows a case where a so-called phase difference detection AF signal can be obtained by the image sensor 6.

  6A is a diagram for explaining the relationship between the image sensor 6 and the coordinate system, FIG. 6B is a diagram for explaining the state of division of the pupil plane of the photographing optical system 3, and FIG. FIG. 3 is a diagram illustrating an image from one viewpoint obtained from an imaging element. FIG. 6D is a diagram for explaining an image obtained from the other viewpoint from the image sensor and a method of phase difference AF, and FIG. 6E is a diagram schematically showing a detection state of the phase difference AF. is there.

  In FIG. 6A, reference numeral 60 denotes a microlens array provided on the image sensor 6, reference numerals 61 and 62 denote a plurality of pixels provided corresponding to one microlens, and reference numerals 71 and 72 denote pixels 61 on the pupil plane, respectively. , 62 are shown. Further, 81 is an image acquired by a pixel corresponding to the pupil region 71, 82 is a subject, 83 is a region of interest in the image 81, 84 is an image acquired by a pixel corresponding to the pupil region 72, and 85 is a region of interest 83 And the positions in the screen indicate the same area. Reference numeral 86 denotes an arrow schematically showing a search, 87 denotes an area in the image 84 corresponding to the area 83 of the image 81, 88 denotes an image obtained by superimposing images obtained from two viewpoints, and 89 denotes an image. Each vector detected in an area 83 in 81 is shown.

  As shown in FIG. 6A, a microlens array 60 is provided on the image sensor 6, and the front principal point of the microlens array 60 is arranged so as to be in the vicinity of the imaging plane of the imaging optical system 3. ing. FIG. 6A illustrates a state in which the microlens array 60 is viewed from the side and the front of the imaging device. When viewed from the front of the imaging device, the lenses of the microlens array 60 cover the pixels on the imaging element 6. Are located in In FIG. 6A, each microlens constituting the microlens array 60 is illustrated in a large size so as to make it easy to see. However, each microlens is actually large enough to cover two pixels.

  FIG. 6B is a diagram in which attention is paid to one micro lens of the image sensor 6 and a pixel below the image sensor 6, and the longitudinal direction of the image sensor 6 including the optical axis of the micro lens is cut in the horizontal direction in the drawing. is there. 6B indicate pixels (one photoelectric conversion unit) of the image sensor 6, respectively. On the other hand, the diagram shown above FIG. 6B shows the exit pupil plane of the imaging optical system 3. Actually, the exit pupil plane is in the direction perpendicular to the paper of FIG. 6B when the direction is matched with the direction of the image pickup device shown in the lower part of FIG. 6B. Is changing.

  The pixels 61 and 62 in FIG. 6B have a positional relationship corresponding to the regions 71 and 72 on the exit pupil plane which are conjugated by the microlens 60. As shown in FIG. 6B, each pixel is designed to be conjugate with a specific area on the exit pupil plane of the imaging optical system 3 by the micro lens 60. That is, only the light beam that has passed through the region 71 on the exit pupil plane of the imaging optical system 3 enters the pixel 61, and only the light beam that has passed through the region 72 on the exit pupil surface of the imaging optical system 3 enters the pixel 62. .

  An image in which only pixels having the same correspondence as the pixel 61 that captures only the light beam that has passed through the pupil region 71 is collected, and only pixels that have the same correspondence as the pixel 62 that captures only the light beam that has passed through the pupil region 72 are collected. Considering the images, the images have different viewpoints. An image obtained by collecting only the pixels having the same correspondence as the pixel 61 is an image as viewed from the pupil region 71, and an image obtained by collecting only the pixels having the same correspondence as the pixel 62 is obtained as viewed from the pupil region 72. It is an image. That is, if the exposure is performed once and the signals are appropriately arranged, images with different viewpoints exposed at the same timing can be obtained.

  Next, a method of performing focus detection (detection of a focus state) using two images acquired from different viewpoints will be described with reference to FIGS. 6C, 6D, and 6E. The optical system described with reference to FIGS. 6A and 6B acquires two images 81 and 84 acquired from different viewpoints. Attention is paid to an area 83 in one of the images 81 where the subject 82 exists. The size of this area can be arbitrarily set, but may be, for example, 8 × 8 pixels. In the example of FIG. 6, the frame is shown sufficiently large for easy understanding.

  The location of this area 83 in the image 84 may be searched based on the absolute difference value (= SAD) or the like. Specifically, the SAD may be calculated in a predetermined range around the area 85 corresponding to the position in the image 84 while shifting the area as indicated by an arrow 86. In this case, the arrow 86 indicating the direction in which the regions are shifted may be set in the direction connecting the centers of gravity of the two pupil regions shown in FIG. This is because there is a so-called epipolar constraint. When the SAD is used as a reference, the minimum position is the corresponding area 87. As a result, in the composite image 88 of the two images, it can be seen that the region 83 has moved like the vector 89. The direction of the vector 89 indicates the direction of the focus lens to be moved when focusing, and the length of the vector 89 indicates the amount of the focus lens to be moved when focusing.

  When focus detection is performed according to the principle described with reference to FIGS. 6C, 6D, and 6E, when specularly reflected light looks different depending on the viewpoint, when there is an object similar to a distant object and at a short distance, a repetitive pattern Errors tend to occur when observing In such a case, a phenomenon occurs in which the degree of coincidence between the two images is reduced, or a plurality of similar peaks are observed, and the judgment cannot be made.

  In FIG. 6, focus detection is performed based on the so-called phase difference AF principle. As another method, a method based on contrast AF can be considered. This is a method in which a focus lens is minutely driven in a time series to observe a change in contrast in a region of interest. This is a method of controlling the focus so that the contrast is maximized. In contrast AF, signals are generally extracted in chronological order. Therefore, errors tend to occur when there is a change in the illumination state, when there is a change in the camera shake state, or when the subject moves.

  Next, an example in which an error occurs in focus detection will be described with reference to FIG. In FIG. 7, reference numeral 91 denotes an example of an image in which a subject having a location similar to a distant place and a close distance exists, and 92 and 93 each denote a frame indicating a similar area. Further, reference numeral 94 denotes an example of an image in which a subject having regular reflection light exists, 95 denotes a subject, and 96 denotes regular reflection light on the subject.

  FIG. 7A is a diagram illustrating an image in which a subject having a location similar to a distant place and a close place exists. It is assumed that the area for focus detection described with reference to FIG. It is near the border between the hats and the brim of the hat. If the rear subject also wears a hat of the same color, the area 92 has a similar signal. If it is determined that the areas 93 and 92 correspond to each other due to the influence of noise or the like, the focus detection results in an error. However, in such a case, information is obtained that it is difficult to distinguish the case from the case in which the case is correctly handled. That is, there is obtained information that there are two local minimum values of the SAD and both of them seem to be almost the same. In the present embodiment, the reliability determination unit 24 determines that an error has occurred using this.

  FIG. 7B is a diagram illustrating an image in which a subject having specularly reflected light exists. When the light of a strong light source such as sunlight shines on the subject 95, the signal of the regular reflection light 96 appears strongly. In the case of a surface having a curvature such as a sphere, the specularly reflected light component is observed at another position on the subject 95 from the viewpoint. For this reason, if the phase difference AF is detected based on the specular reflected light component, the focus detection becomes an error. However, in such a case, since the position is observed differently between the contour portion of the subject and the specular reflection light, information indicating that the degree of coincidence between the two images is reduced is obtained. In the present embodiment, the reliability determination unit 24 determines that an error has occurred using this.

  In a situation where an error is likely to occur in the actual operating environment as described above, it is assumed that the AF becomes unstable. In such a case, the operation of the present embodiment is performed to control the position of the focus lens. It can be performed stably.

  As described above, according to the present embodiment, in a system that performs focus adjustment using a signal on an imaging surface, appropriate lens control can be performed even when a focus detection error occurs, and stable high quality It is possible to provide a perfect image.

(Other embodiments)
The present invention supplies a program for realizing one or more functions of the above-described embodiments to a system or an apparatus via a network or a storage medium, and one or more processors in a computer of the system or the apparatus read and execute the program. This processing can be realized. Further, it can be realized by a circuit (for example, an ASIC) that realizes one or more functions.

3: photographing optical system, 5: camera system control circuit, 6: image sensor, 7: image processing unit, 8: memory unit, 12: lens system control circuit, 13: lens drive unit, 15: lens position sensor, 21: Focus detection unit, 22: electronic cam calculation unit, 23: changeover switch, 24: reliability determination unit

Claims (8)

Focus detection means for detecting the focus state of the imaging optical system,
Zoom position detecting means for detecting a zoom position of the imaging optical system,
Focus position detection means for detecting the position of the focus lens of the imaging optical system,
Adjusting means for adjusting the position of the focus lens of the imaging optical system;
Storage means for storing a trajectory of the focus lens for keeping focusing on a subject at the same distance in accordance with a change in the zoom position;
Determining means for determining the reliability of the output of the focus detecting means;
A first operation for controlling the position of the focus lens in accordance with a change in the zoom position based on an output of the focus detection unit, and information on a trajectory of the focus lens stored in the storage unit Controlling means for controlling the position of the focus lens in accordance with the change in the zoom position, and a control means for switching in accordance with the determination of the determination means ,
The control means includes:
When the determination unit determines that the output of the focus detection unit is reliable, performs the first operation, when the determination unit determines that the output of the focus detection unit is unreliable, Performing the second operation,
When performing the second operation, based on detection results of a plurality of focus states detected by the focus detection unit before the timing at which the determination unit determines that the output of the focus detection unit is unreliable. An imaging apparatus for estimating a position of a subject based on the estimated position of the subject and controlling the position of the focus lens based on information of a locus of the focus lens stored in the storage unit. . The control unit controls the position of the focus lens by using an output of the focus position detection unit in addition to an output of the focus detection unit when performing the first operation. Item 2. The imaging device according to Item 1 . The determination means determines that the output of the focus detection means is unreliable if the degree of coincidence between the two images for detecting the phase difference is low when detecting the focus state of the imaging optical system by detecting the phase difference. the imaging apparatus according to claim 1 or 2, characterized in that. The determination means, when detecting the focus state of the imaging optical system by phase difference detection, when there is a plurality of peaks in the image for detecting the phase difference, if the output of the focus detection means is not reliable the imaging apparatus according to any one of claims 1 to 3, wherein the determining. Said determining means, when the regular reflection light subject is present in the image, according to any one of claims 1 to 4, characterized in that determining that there is no reliability in the output of the focus detection unit Imaging device. A method for controlling an imaging device, comprising:
A focus detection step of detecting a focus state of the imaging optical system,
A zoom position detecting step of detecting a zoom position of the imaging optical system,
A focus position detecting step of detecting a position of a focus lens of the imaging optical system,
An adjusting step of adjusting a position of a focus lens of the imaging optical system,
A storage step of storing a trajectory of the focus lens for keeping focusing on a subject at the same distance in accordance with the change in the zoom position;
A determination step of determining the reliability of the output of the focus detection step;
A first operation of controlling the position of the focus lens according to a change in the zoom position based on an output of the focus detection step, and information on a trajectory of the focus lens stored in the storage step and a second operation for control of the position of the focus lens in response to changes in the zoom position, have a, and a control step of switching in accordance with the determination of the determining step,
In the control step,
When it is determined in the determination step that the output of the focus detection step is reliable, the first operation is performed, and when it is determined that the output of the focus detection step is not reliable in the determination step, Performing the second operation,
When performing the second operation, based on the detection results of the plurality of focus states detected by the focus detection step before the timing at which the output of the focus detection step is determined to be unreliable in the determination step The position of the focus lens is controlled based on the estimated position of the subject and the information on the trajectory of the focus lens stored in the storage step . Control method. A program for causing a computer to execute each step of the control method according to claim 6 . A computer-readable storage medium storing a program for causing a computer to execute each step of the control method according to claim 6 .

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