Lens control device, lens device, and lens control method

Abstract

To obtain good focusing accuracy even when AF is performed during zoom tracking.SOLUTION: A lens control device 105 controls the drive of a focus lens 104 by using control information related to the position of the focus lens according to the position of a magnification varying lens 102 and a subject distance, to reduce focus fluctuation occurring with the movement of the magnification varying lens. The lens control device acquires, at a first time point, information on the position of the magnification varying lens at a second time point subsequent to the first time point and information on the subject distance at the second time point, and acquires the position of the magnification varying lens at the second time point and a first target position according to the subject distance by using the control information. The lens control device controls the drive of the focus lens by using the first target position.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to lens control for performing autofocus (AF) and zoom tracking.

Background Art

[0002] In a zoom lens that controls the driving of a focus lens by AF, zoom tracking for controlling the driving of the focus lens is often performed in order to reduce focus fluctuations associated with zooming. In this case, driving of the focus lens by AF may occur during zoom tracking.

[0003] Patent Document 1 discloses a method of normalizing position information of a focus lens in order to correctly operate servo AF even when servo AF for following the focus of a moving subject is performed during zooming.

Prior Art Document

Patent Document

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the focus lens is driven by AF during zoom tracking, the control deviation of the focus lens may increase. For example, when AF drives the focus lens during continuous zooming while zoom tracking is being performed, sudden acceleration or deceleration of the focus lens is likely to occur at the moment AF starts. When sudden acceleration or deceleration occurs, a delay occurs in controlling the driving speed of the focus lens, increasing the control deviation. When the control deviation increases, a stationary image with out-of-focus may be captured, or a video with a long out-of-focus time may be captured. In particular, when the driving direction of the focus lens by zoom tracking and the driving direction of the focus lens by AF during zoom tracking are in opposite directions, a reverse drive occurs in which the driving direction of the focus lens suddenly switches. Reverse drive is likely to increase the control deviation.

[0006] However, Patent Document 1 does not disclose a method for suppressing the control deviation when the focus lens is driven by AF during zoom tracking as described above.

[0007] The present invention provides a lens control device and the like that can obtain good focusing accuracy even when AF is performed during zoom tracking.

Means for Solving the Problems

[0008] A lens control device according to an aspect of the present invention controls the driving of a focus lens using control information regarding the position of the focus lens corresponding to the position of a zoom lens and the subject distance in order to reduce focus variation accompanying the movement of the zoom lens. The lens control device includes an acquisition unit that, at a first time point, acquires information regarding the position of the zoom lens at a second time point after the first time point and information regarding the subject distance at the second time point, and acquires a first target position corresponding to the position of the zoom lens at the second time point and the subject distance at the second time point using the control information, and a control unit that controls the driving of the focus lens using the first target position. Note that a lens device and an imaging device having the above lens control device also constitute another aspect of the present invention.

[0009] As another aspect of the present invention, a lens control method reduces focus fluctuations associated with the movement of a zoom lens by controlling the driving of a focus lens using control information regarding the position of the focus lens according to the position of the zoom lens and the subject distance. The lens control method includes: at a first time point, obtaining information regarding the position of the zoom lens at a second time point after the first time point and information regarding the subject distance at the second time point; obtaining a first target position according to the position of the zoom lens and the subject distance at the second time point using the control information; and controlling the driving of the focus lens using the first target position. Note that a program for causing a computer to execute processing according to the above lens control method also constitutes another aspect of the present invention.

Advantages of the Invention

[0010] According to the present invention, even when AF is performed during zoom tracking, good focusing accuracy can be obtained.

Brief Description of the Drawings

[0011]

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Best Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment

[0013] FIG. 1 shows the configuration of the lens interchangeable camera system of this embodiment. The lens interchangeable camera system is composed of a lens device 100 and a camera body 200 as an imaging device to which the lens device 100 is detachably attached, and can perform still image imaging and moving image imaging.

[0014] The lens device 100 includes a zoom lens 101 as an imaging optical system capable of forming a subject image on the imaging element 201 in the camera body 200, and a lens control unit 105 capable of communicating with the camera control unit 207 in the camera body 200.

[0015] The zoom lens 101 includes a variable magnification lens 102, a diaphragm 103, and a focus lens 104. The variable magnification lens 102 is movable in the optical axis direction in response to the operation of a zoom operation ring (not shown) by the user. By moving the variable magnification lens 102, the focal length of the zoom lens 101 is changed, and zooming is performed. The variable magnification lens 102 may be driven by an actuator. The focus lens 104 moves in the optical axis direction during focusing.

[0016] The lens control unit 105 as a lens control device is a computer including a CPU, and is electrically connected to a memory 106, a zoom position detection unit 107, a diaphragm drive unit 108, and a focus drive unit 109. The lens control unit 105 receives a focus drive command including the drive amount of the focus lens 104 (hereinafter referred to as the focus drive amount) through communication with the camera control unit 207, and controls the focus drive unit 109 based on the focus drive command. Thereby, the focus lens 104 is driven. Further, the lens control unit 105 receives a diaphragm drive command from the camera control unit 207, and drives the diaphragm 103 by controlling the diaphragm drive unit 108 based on the diaphragm drive command. Furthermore, the lens control unit 105 receives a notification of the start of imaging from the camera control unit 207.

[0017] The zoom position detection unit 107 detects the position of the variable magnification lens 102 (hereinafter referred to as the zoom position) using a zoom position sensor such as a variable resistor, and outputs information on the zoom position to the lens control unit 105. At this time, the lens control unit 105 only needs to acquire information related to the zoom position, such as information convertible to the zoom position, rather than information indicating the zoom position itself. The information related to the zoom position includes information on the rotation operation position of the zoom operation ring, information converted from the zoom position to the focal length, and the like.

[0018] The aperture drive unit 108 includes an aperture actuator such as a stepping motor or a voice coil motor that drives the aperture 103, and an aperture sensor such as a hall element for detecting the drive position (aperture diameter) of the aperture 103. The focus drive unit 109 includes a focus actuator such as a stepping motor, a vibration type motor, or a voice coil motor, and a focus position sensor such as an encoder for detecting the position of the focus lens 104 in the optical axis direction (hereinafter referred to as the focus position).

[0019] The memory 106 is composed of a ROM, a RAM, etc., and stores electronic camera information as control information regarding the position of the focus lens 104 (hereinafter referred to as the in-focus position) that focuses on each subject distance for each zoom position. In the following description, it will be described as if the electronic camera information is information on a curve indicating the locus (drive locus) of the movement of the focus lens 104, but actually it is table data indicating the in-focus position for each zoom position and subject distance, information on a function capable of calculating the in-focus position, etc.

[0020] The zoom lens 101 in this embodiment is an inner focus (rear focus) type zoom lens, and the position of the image plane varies and the focus is shifted as the zooming progresses. Therefore, the lens control unit 105 performs zoom tracking to control the drive of the focus lens 104 using the electronic camera information stored in the memory 106 in order to reduce (compensate) the variation in the image plane position during zooming, that is, the focus variation.

[0021] The camera body 200 includes an imaging element 201, a signal processing unit 202, a recording processing unit 203, an electronic viewfinder 204, a display unit 205, a defocus detection unit 206, a camera control unit 207, and a memory 208.

[0022] The imaging device 201 is composed of a photoelectric conversion element such as a CCD sensor or a CMOS sensor, converts a subject image into an imaging signal as an electrical signal (i.e., images the subject), and outputs the imaging signal to the signal processing unit 202. The imaging device 201 in this embodiment has imaging pixels that output an imaging signal for generating an imaging image, and a pair of focus detection pixels that output a focus detection signal for AF, which are paired with a microlens that performs pupil division and a photoelectric conversion element.

[0023] The signal processing unit 202 performs various processes such as amplification, noise removal, and color correction on the input imaging signal to generate an image signal (image data), and outputs it to the recording processing unit 203.

[0024] The recording processing unit 203 records the input image data. The recorded image data is also displayed on the electronic viewfinder 204 and the display unit 205.

[0025] The defocus detection unit 206 detects the focus state of the zoom lens 101 with respect to the subject image using the pair of focus detection signals from the imaging device 201. Specifically, the defocus detection unit 206 detects the phase difference (image shift amount) in the pair of focus detection signals, obtains the defocus amount from the phase difference, and outputs this to the camera control unit 207.

[0026] The camera control unit 207 is a computer including a CPU, and is electrically connected to the recording processing unit 203, the defocus detection unit 206, and the memory 208. The camera control unit 207 reads and executes a program recorded in the memory 208, or communicates information necessary for AF with the lens control unit 105. Information necessary for AF is information regarding the subject distance (hereinafter referred to as subject distance information) obtained by converting the defocus amount using an equation or coefficient obtained from the imaging relationship of the zoom lens 101. The subject distance information may be information indicating the subject distance itself, or information convertible to the subject distance, such as the focus drive amount for obtaining the in-focus state calculated from the defocus amount and the focus position detected by the focus position sensor and received from the lens control unit 105.

[0027] Note that in this embodiment, the case of performing the imaging plane phase difference detection method AF will be described, but the contrast detection method AF may be performed instead.

[0028] FIG. 2 shows information indicating the relationship between the electronic camera information, that is, the focus position (in-focus position) for obtaining an in-focus state according to the zoom position and the subject distance. In FIG. 2, the horizontal axis represents the zoom position, and the vertical axis represents the focus position. The solid curves indicate the relationship between the zoom position and the focus position for each subject distance (1 m, 3 m, 5 m, and infinity). The memory 106 stores, as electronic camera information, the focus position for each zoom position (which may be a representative zoom position) on the curve corresponding to each of a plurality of representative subject distances.

[0029] When the subject distance matches a representative subject distance in the electronic camera information, the focus position can be obtained from the electronic camera information corresponding to the representative subject distance. The lens control unit 105 sets the focus position as the focus target position and controls the drive of the focus lens 104 to the focus target position.

[0030] On the other hand, when the subject distance is different from the representative subject distance, the focus position can be obtained by an operation such as linear interpolation using the electronic camera information corresponding to the representative subject distance in the vicinity of the subject distance.

[0031] FIGS. 3(a) and (b) show a method for calculating the focus position when the subject distance is different from the representative subject distance. In FIG. 3, the horizontal axis represents the zoom position, and the vertical axis represents the focus position. FIG. 3(a) shows the entire electronic camera information, and FIG. 3(b) shows an enlarged view of the portion surrounded by the frame in FIG. 3(a).

[0032] Here, a case of calculating the focus position at the zoom position y between the wide-side zoom position x and the tele-side zoom position z at the subject distance A' between the typical subject distances A and B will be described. First, the lens control unit 105 reads out the focus positions at the subject distances A and B at the wide-side zoom position x from the electronic camera information, and calculates the ratio b / a of the difference a between these and the difference b between the focus positions at the subject distances A and A'. Then, using the focus positions at the subject distances A and B and the ratio b / a, the focus position at the subject distance A' at the wide-side zoom position x is calculated.

[0033] Next, the lens control unit 105 reads out the focus positions at the subject distances A and B at the tele-side zoom position z from the electronic camera information. The ratio b' / a' of the difference a' between these and the difference b' between the focus positions at the subject distances A and A' is the same as the ratio b / a. Then, using the focus positions at the subject distances A and B and the ratio b' / a' (= b / a), the focus position at the subject distance A' at the tele-side zoom position z is calculated.

[0034] Finally, the lens control unit 105 calculates the zoom movement amount l, which is the difference between the wide-side zoom position x and the zoom position y, and the zoom movement amount m, which is the difference between the zoom position y and the tele-side zoom position z. Then, using the focus positions at the wide-side and tele-side zoom positions x and z at the subject distance A' and the ratio l / (l + m) of the movement amounts, the focus position at the zoom position y at the subject distance A' is calculated. The lens control unit 105 uses the focus position at the zoom position y at the subject distance A' calculated in this way as the focus target position, and performs control to drive the focus lens 104 to the focus target position.

[0035] Next, the lens control process when driving of the focus lens 104 by AF occurs during zoom tracking in this embodiment will be described.

[0036] FIG. 12 shows the driving trajectory of the focus lens (hereinafter referred to as the focus driving trajectory) when zooming is performed during still image continuous shooting (burst shooting) and the focus lens is driven by AF during zoom tracking. The broken line shows the focus driving trajectory for each subject distance based on the electronic camera information. The portion of the solid line with the arrow ZT attached shows the driving trajectory of the focus lens by zoom tracking. Also, the portion of the solid line with the arrow AF attached shows the driving trajectory of the focus lens due to the change in the subject distance acquired by AF. Further, I1, I2, and I3 indicate the time points when imaging is performed during burst shooting, and the black circles indicate the focus target positions at the time points when each imaging is performed.

[0037] As shown in the figure, while the focus lens is being driven by zoom tracking, the focus lens is driven by AF at time points I1, I2, and I3. In this figure, the driving direction of the focus lens by AF performed at time point I1 is opposite to the driving direction of the focus lens by zoom tracking before and after time point I1. That is, reverse driving of the focus lens occurs. As described above, reverse driving of the focus lens tends to increase the control deviation in the control of the driving of the focus lens. Therefore, it is preferable to avoid reverse driving of the focus lens even when the subject distance acquired by AF changes.

[0038] The flowchart of FIG. 4 shows a lens control process (lens control method) that can avoid reverse driving of the focus lens 104 due to AF (change in subject distance) during zoom tracking. The lens control unit 105 executes this process according to a program. In the following description, the driving of the focus lens 104 is referred to as focus driving, and the direction in which the focus lens 104 is driven is referred to as the focus driving direction. Also, the time point when each imaging is performed in burst shooting is referred to as the imaging time point.

[0039] First, as an acquisition unit, the lens control unit 105 acquires subject distance information at the next imaging time (the second time point) determined by AF from the camera control unit 207 at step S401 at the current time (the first time point). The lens control unit 105 may receive a notification of the next imaging time from the camera control unit 207, may estimate the next imaging time from the intervals between the previous imaging time points, or may estimate the next imaging time from the focus drive command for AF.

[0040] Also, the subject distance information at the next imaging time is determined and updated by AF, and is updated using the subject distance information communicated from the camera control unit 207 to the lens control unit 105 regardless of the timing of step S401. Also, the subject distance information at the next imaging time may be estimated and acquired from the current subject distance and the past subject distances.

[0041] Next, at step S402, the lens control unit 105 estimates (acquires) the zoom position at the next imaging time. The zoom position at the next imaging time can be estimated from the current zoom position and the past positions.

[0042] Next, at step S403, the lens control unit 105 calculates and acquires a focus target position A (the first target position) at the next imaging time based on the estimated zoom position at the next imaging time, the subject distance information, and the electronic camera information stored in the memory 106.

[0043] Next, at step S404, the lens control unit 105 calculates and acquires a focus target position B (the second target position) at the current time or after a predetermined time from the current time (both are the first time point) based on the position of the zoom lens 102 at the current time or after a predetermined time from the current time, the subject distance information at the next imaging time, and the trajectory information stored in the memory 106.

[0044] Next, in step S405, the lens control unit 105 as the control means determines whether the focus drive directions to the focus target position A and the focus target position B are the same or not. If they are the same, the process proceeds to step S406; if they are in the opposite direction, the process proceeds to step S407.

[0045] In step S406, the lens control unit 105 causes the focus control unit 109 to perform a focus drive to the focus target position B. Then, the process from step S401 is repeated while zooming is being performed.

[0046] In step S407, the lens control unit 105 causes the focus control unit 109 to stop the focus drive. Then, the process from step S401 is repeated while zooming is being performed.

[0047] The process shown in FIG. 4 is repeatedly executed at a predetermined control cycle. During non-imaging, the focus drive to the focus target position B is always performed. Note that the control cycle may always be constant or may change according to the processing state. Also, the estimation accuracy of the zoom position improves as the next imaging time approaches, and the calculation accuracy of the focus target position (the first target position) also improves. Therefore, by periodically repeating the process of FIG. 4, a higher-accuracy focus target position is updated while performing a focus drive to the focus target position.

[0048] Figure 5 shows, by a solid line, the focus drive locus by the lens control process of FIG. 4. I1, I2, and I3 indicate imaging time points during continuous shooting, as in FIG. 12. I2 is the next imaging time point with respect to I1, and I3 is the next imaging time point with respect to I2. The zoom positions at I1, I2, and I3 are shown as X, Y, and Z, respectively. The dashed lines indicate the focus drive loci for each subject distance (a to d) based on the electronic camera information. Hereinafter, each focus drive locus is referred to as the same distance locus. The black circles indicate the focus target position A at the next imaging time point calculated in step S403 of FIG. 4. The focus target position A at the next imaging time point is updated according to the subject distance information obtained by AF, and is the focus position at I2 when the zoom position is between X and Y, and the focus position at I3 when the zoom position is between Y and Z.

[0049] The black squares indicate the focus target position B corresponding to the zoom positions at I2' and I3' as the current time points calculated in step S404. Note that I2' and I3' may be at the same time as the imaging time points I1 and I2, respectively, or may be at a time point after a predetermined time (after AF is performed) from I1 and I2. The zoom position at I2' is X, and the zoom position at I3' is Y. Also, let X2 be the zoom position at which the focus drive is started after the stop of the focus drive ends between X and Y.

[0050] As shown in the figure, the focus drive direction to the focus target position B at I2' and the focus drive direction to the focus target position A at the next imaging time point I2 are opposite to each other. At this time, the focus drive is stopped in step S407 of FIG. 4. Between the zoom positions from X to X2, step S407 is executed for each control cycle of the focus drive, and the stop of the focus drive continues.

[0051] When the zoom position reaches X2 near the next imaging time point I2 at I2″, the focus drive direction to the focus target position B calculated at this time (the current time) and the focus drive direction to the focus target position A are in the same direction as each other. Therefore, between the zoom position from X2 to Y, the focus drive to the focus target position B is performed in step S406 of FIG. 4. Since the control of the focus drive is performed periodically, the focus lens 104 moves along the same distance trajectory of the subject distance b. As a result, the focus lens 104 reaches the focus target position A at the next imaging time point I2. The same focus drive is performed between the zoom position from Y to Z.

[0052] As described above, in this embodiment, when the direction of the focus target position with respect to the zoom position at a time point before the next imaging time point and the direction of the focus target position with respect to the estimated zoom position at the next imaging time point are opposite to each other, the focus drive is stopped. Then, when these directions become the same as each other, the focus drive is started. Thereby, even when AF is performed during zoom tracking (even if the subject distance changes), it is possible to avoid the reverse drive of the focus lens 104 and reduce the control deviation, and the focusing accuracy at each imaging time point can be improved.

Embodiment

[0053] Next, Embodiment 2 will be described. In Embodiment 2, the focus drive is performed at a speed that reaches the focus target position at the next imaging time point earlier than the next imaging time point. Components common to Embodiment 1 in this embodiment are denoted by the same reference numerals as in Embodiment 1.

[0054] The flowchart of FIG. 6 shows the lens control process in this embodiment. First, in step S601 at the current time (the first time point), the lens control unit 105 acquires the subject distance information at the next imaging time point determined by AF from the camera control unit 207 in the same manner as in step S401 of FIG. 4.

[0055] Next, in step S602, the lens control unit 105 estimates the zoom position at the next imaging time (second time) in the same manner as in step S402.

[0056] Next, in step S603, the lens control unit 105 calculates the focus target position (first target position) at the next imaging time based on the estimated zoom position at the next imaging time, the subject distance information at the next imaging time, and the electronic camera information in the same manner as in step S403.

[0057] Next, in step S604, the lens control unit 105 causes the focus control unit 109 to perform focus driving at a speed that reaches the focus target position calculated in step S603 earlier than the next imaging time. The speed at this time may be a predetermined speed (predetermined speed: for example, the maximum speed at which the focus lens 104 can be driven), or a speed calculated to reach earlier than the next imaging time. Then, this process ends.

[0058] FIG. 7 shows the focus driving locus in this embodiment by a solid line. The broken lines, I1, I2, I3, I2′, I3′, and the zoom positions X, Y, Z are the same as in FIG. 5.

[0059] As shown in the figure, the focus driving direction to the focus target position (black square) at I2′ and the focus driving direction to the focus target position (black circle) at the next imaging time I2 are opposite to each other. In this case, in this embodiment, the focus driving to the focus target position at I2′ is not performed, and the focus driving is performed from the time of the zoom position X to the focus target position at the next imaging time I2. After performing the focus driving to the focus target position at the next imaging time I2, the focus driving is stopped until the next imaging time I2 when the zoom position reaches Y. However, instead of stopping the focus driving, the focus driving may be performed in accordance with the update of the focus target position in accordance with the update of the estimated zoom position.

[0060] Regarding the focus drive from imaging time point I2 to the next imaging time point I3, it is the same as the focus drive from I1 to I2 described above.

[0061] FIG. 8 shows, by a solid line, a focus drive locus in a case where the focus drive direction to the focus target position at I2′ (I3′) and the focus drive direction to the focus target position at the next imaging time point I2 (I3) are in the same direction. Even in this case, if the drive amount of the focus drive to the focus target position at I2′ is larger than the drive amount of the focus drive to the focus target position at the next imaging time point I2, reverse drive occurs. However, in this embodiment, by performing the focus drive to the focus target position at I2 so as not to reach (or head towards) the focus target position at I2′ beyond the focus target position at I2, reverse drive is not performed.

[0062] In the first embodiment, when the focus drive direction to the focus target position at I2′ and the focus drive direction to the focus target position at the next imaging time point I2 are in the same direction, the focus drive to the focus target position at I2′ is performed without stopping the focus drive. Therefore, reverse drive cannot be avoided. In contrast, in this embodiment, reverse drive can be avoided even in the case shown in FIG. 8.

[0063] Both FIG. 7 and FIG. 8 show examples of focus drive in which reverse drive can occur. However, even when reverse drive does not occur, by performing the drive to the focus target position at the next imaging time as in this embodiment, the control deviation can be reduced.

[0064] Thus, in this embodiment, the focus drive is performed so as to reach the focus target position at the next imaging time earlier than the next imaging time without performing reverse drive. Thereby, even when AF is performed during zoom tracking, it becomes possible to avoid reverse drive of the focus lens 104 and reduce the control deviation, and the focusing accuracy at each imaging time can be improved. Furthermore, reverse drive in patterns that cannot be avoided by the lens control process of the first embodiment can also be avoided in the second embodiment.

[0065] Note that, in the first embodiment, the advantage is that the control deviation can be reduced because the acceleration and deceleration are small, and in the second embodiment, the advantage is that reverse driving can be avoided. Therefore, in a situation where reverse driving can be avoided even in the first embodiment, the focus drive may be performed by the method of the first embodiment, and in a situation where reverse driving can be avoided only in the second embodiment, the focus drive may be performed by the method of the second embodiment.

Embodiment

[0066] Next, a description will be given of a third embodiment. In the third embodiment, the focus drive is performed at a speed at which the focus target position at the next imaging time point is reached at the next imaging time point. Components common to the first embodiment in this embodiment are denoted by the same reference numerals as those in the first embodiment.

[0067] The flowchart of FIG. 9 shows the lens control process in this embodiment. First, in step S901 at the current time point (the first time point), the lens control unit 105 acquires, in the same manner as in step S401 of FIG. 4, the subject distance information at the next imaging time point determined by AF from the camera control unit 207.

[0068] Next, in step S902, the lens control unit 105 estimates the zoom position at the next imaging time point (the second time point) in the same manner as in step S402.

[0069] Next, in step S903, the lens control unit 105 calculates the focus target position (the first target position) at the next imaging time point based on the estimated zoom position at the next imaging time point, the subject distance information at the next imaging time point, and the electronic camera information, in the same manner as in step S403.

[0070] Next, in step S904, the lens control unit 105 calculates the driving speed of the focus lens 104 at which the focus lens 104 reaches the focus target position at the next imaging time point calculated in step S903 at the next imaging time point.

[0071] Next, in step S905, the lens control unit 105 causes the focus control unit 109 to perform focus driving at the driving speed calculated in step S904 to the focus target position at the next imaging time calculated in step S903.

[0072] FIG. 10 shows the focus driving locus in this embodiment by a solid line. The broken line, I1, I2, I3, I2′, I3′ and the zoom positions X, Y, Z are the same as those in FIG. 5.

[0073] As shown in the figure, the focus driving direction to the focus target position (black square) at I2′ and the focus driving direction to the focus target position (black circle) at the next imaging time I2 are opposite to each other. In the lens control process of FIG. 9, the focus driving to the focus target position at I2′ is not performed, and the focus driving to the focus target position at the next imaging time I2 is directly performed at the driving speed calculated in step S904 from the beginning.

[0074] The focus driving from the imaging time I2 to the next imaging time I3 is the same as the focus driving from I1 to I2 described above.

[0075] FIG. 11 shows the locus of the focus target position when the focus driving direction to the focus target position at I2′ (I3′) and the focus driving direction to the focus target position at the next imaging time I2 (I3) are in the same direction by a solid line. Even in this case, if the driving amount of the focus driving to the focus target position at I2′ is larger than the driving amount of the focus driving to the focus target position at the next imaging time I2, reverse driving occurs. However, also in this embodiment, similar to Embodiment 2, by performing the focus driving to the focus target position at I2 so as not to reach the focus target position at I2′ beyond the focus target position at I2, reverse driving is not performed. Moreover, since there is no sudden acceleration, deceleration or stop of the focus driving, the control deviation of the focus driving can be further reduced compared to Embodiment 2.

[0076] Although both FIGS. 10 and 11 show examples of focus driving in which reverse driving can occur, even when reverse driving does not occur, by driving to the focus target position at the next imaging time as in this embodiment, the control deviation can be reduced.

[0077] Thus, in this embodiment, without performing reverse driving, focus driving is performed at the speed at which the focus target position at the next imaging time is reached at the next imaging time. As a result, even when AF is performed during zoom tracking, it is possible to avoid reverse driving of the focus lens 104 and reduce the control deviation, and the focusing accuracy at each imaging time can be improved.

[0078] In Examples 1 to 3, the case where focus driving is performed to the focus target position at the next imaging time as the second time has been described. However, even when focus driving is performed to the focus target position at a second time other than the next imaging time, the focus driving of each of the above embodiments may be performed. As the second time other than the next imaging time, for example, it may be a time based on the time when subject distance information by AF is acquired (for example, after a predetermined time from that time). Thereby, even when imaging is not performed, the same focus driving as in each embodiment becomes possible.

[0079] When the second time is the next imaging time, as described also in step S401 of FIG. 4, a specific time may be estimated based on a signal notifying the imaging time transmitted from the camera control unit 207, or the next imaging time may be communicated from the camera control unit 207. Further, when AF for the next imaging is performed immediately after the end of the current imaging, it is ideal that the AF time for obtaining the in-focus state at the current imaging time and the next imaging time substantially coincide. When the current imaging time and the AF time for the next imaging substantially coincide, the next imaging time as the second time can also be estimated based on the cycle of AF.

[0080] Also, the second time is updated each time the second time is reached. AF may be performed at a time other than the second time, and it is sufficient to obtain subject distance information at that time.

[0081] Note that lens control processing combining the lens control processing of at least two of Examples 1 to 3 may be performed.

[0082] In Examples 1 to 3, the case where the lens control device is mounted on the lens device detachably attached to the imaging device has been described. However, the lens control device may be mounted on the imaging device to which the lens device is detached, or the lens control device may be mounted on the lens-integrated imaging device.

[0083] The above embodiments include the following configurations.

[0084] (Configuration 1) A lens control device that controls the driving of a focus lens using control information regarding the position of the focus lens according to the position of the variable magnification lens and the subject distance in order to reduce focus variation accompanying the movement of the variable magnification lens, At a first point in time, information regarding the position of the variable magnification lens at a second point in time after the first point in time and information regarding the subject distance at the second point in time are acquired, and a first target position corresponding to the position of the variable magnification lens at the second point in time and the subject distance at the second point in time is acquired using the control information; an acquisition means, A lens control device characterized by having control means for controlling the driving of the focus lens using the first target position. (Configuration 2) The control means controls the driving of the focus lens using the first target position so that the driving direction of the focus lens does not reverse when the subject distance obtained from the information regarding the subject distance between the first point in time and the second point in time changes. The lens control device according to Configuration 1. (Configuration 3) The acquisition means acquires a second target position corresponding to the position of the variable magnification lens at a point in time between the first point in time and a point in time before the second point in time and the subject distance at the second point in time using the control information, The control means, When the driving direction of the focus lens to the first target position and the driving direction of the focus lens to the second target position are opposite to each other, the driving of the focus lens is stopped. The lens control device according to Configuration 1 or 2, wherein the driving of the focus lens is started when the driving direction to the first target position and the driving direction to the second target position are the same as each other. (Configuration 4) The acquisition means uses the control information to acquire the position of the zoom lens at a time point between the first time point and a time point before the second time point, and a second target position corresponding to the subject distance at the second time point. The control means controls the driving of the focus lens so that when the driving direction of the focus lens to the first target position and the driving direction of the focus lens to the second target position are the same as each other, and the driving amount of the focus lens to the second target position is larger than the driving amount of the focus lens to the first target position, the focus lens does not reach the second target position beyond the first target position. The lens control device according to any one of Configurations 1 to 3. (Configuration 5) The lens control device according to any one of Configurations 1 to 4, wherein the control means controls the driving of the focus lens so that the focus lens reaches the first target position earlier than the second time point. (Configuration 6) The lens control device according to any one of Configurations 1 to 4, wherein the control means controls the driving of the focus lens so that the focus lens reaches the first target position at the second time point. (Configuration 7) The lens control device according to any one of Configurations 1 to 6, wherein the second time point is the time point when imaging is performed. (Configuration 8) The lens control device according to any one of Configurations 1 to 6, wherein the second time point is a time point based on the time point when information on the subject distance is obtained. (Configuration 9) An imaging optical system including the zoom lens and the focus lens, A lens device, comprising the lens control device according to any one of Configurations 1 to 8. (Configuration 10) The lens device is detachable from an imaging device that images a subject through the imaging optical system, The lens device according to Configuration 9, wherein the acquisition means acquires information on the subject distance from the imaging device. (Configuration 11) An image sensor that images a subject through an imaging optical system including the zoom lens and the focus lens, An imaging device, comprising the lens control device according to any one of Configurations 1 to 8.

[0085] (Other Embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0086] Each of the embodiments described above is merely a representative example, and various modifications and changes can be made to each embodiment when implementing the present invention.

Description of Reference Numerals

[0087] 100 Lens device 101 Zoom lens 102 Zoom lens 104 Focus lens 105 Lens control unit (control means) 200 Camera body

Claims

1. A lens control device that controls the driving of a focus lens using control information regarding the position of the focus lens according to the position of the zoom lens and the subject distance in order to reduce focus variation accompanying the movement of the zoom lens, at a first time point, acquires information regarding the position of the zoom lens at a second time point after the first time point and information regarding the subject distance at the second time point, and acquires, using the control information, a first target position according to the position of the zoom lens at the second time point and the subject distance at the second time point; an acquisition means; and a control means for controlling the driving of the focus lens using the first target position. The lens control device is characterized by having these.

2. The control means controls the driving of the focus lens using the first target position so that the driving direction of the focus lens does not reverse when the subject distance obtained from the information regarding the subject distance between the first time point and the second time point changes. The lens control device according to Claim 1, characterized by this.

3. The acquisition means acquires, using the control information, a second target position according to the position of the zoom lens at a time point between the first time point and a time point before the second time point and the subject distance at the second time point, The control means, when the driving direction of the focus lens to the first target position and the driving direction of the focus lens to the second target position are in opposite directions to each other, stops the driving of the focus lens, and starts the driving of the focus lens when the driving direction to the first target position and the driving direction to the second target position become the same direction to each other. The lens control device according to Claim 1, characterized by this.

4. The acquisition means acquires a second target position corresponding to the position of the zoom lens at a time point from the first time point to a time point before the second time point and the subject distance at the second time point by using the control information. The control means is characterized in that when the driving direction of the focus lens to the first target position and the driving direction of the focus lens to the second target position are the same, and the driving amount of the focus lens to the second target position is larger than the driving amount of the focus lens to the first target position, the control means controls the driving of the focus lens so that the focus lens does not reach the second target position beyond the first target position. The lens control device according to claim 1.

5. The control means is characterized in that the control means controls the driving of the focus lens so that the focus lens reaches the first target position earlier than the second time point. The lens control device according to claim 1.

6. The control means is characterized in that the control means controls the driving of the focus lens so that the focus lens reaches the first target position at the second time point. The lens control device according to claim 1.

7. The second time point is the time point when imaging is performed. The lens control device according to claim 1.

8. The second time point is a time point based on the time point when information regarding the subject distance is acquired. The lens control device according to claim 1.

9. An imaging optical system including the zoom lens and the focus lens, A lens device, characterized by comprising the lens control device according to claim 1.

10. The lens device is detachable from an imaging device that images a subject through the imaging optical system. The lens device according to claim 9, wherein the acquisition means acquires information regarding the subject distance from the imaging device.

11. An imaging element that images a subject through an imaging optical system including the zoom lens and the focus lens, An imaging device, comprising the lens control device according to claim 1.

12. A lens control method for controlling the driving of a focus lens using control information regarding the position of the focus lens according to the position of the zoom lens and the subject distance in order to reduce focus variation accompanying the movement of the zoom lens, At a first time point, a step of acquiring information regarding the position of the zoom lens at a second time point after the first time point and information regarding the subject distance at the second time point; A step of acquiring a first target position according to the position of the zoom lens at the second time point and the subject distance at the second time point using the control information; And a step of controlling the driving of the focus lens using the first target position. The lens control method is characterized by the above.

13. A program for causing a computer to execute processing according to the lens control method according to claim 12.

Images