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 that controls the driving of the focus lens is often also performed in order to reduce focus variation 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 the position information of a focus lens in order to correctly operate servo AF even when servo AF for following focus with respect to a moving subject is performed during zooming.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When autofocus (AF) drives the focus lens during zoom tracking, there is a risk of large control deviations in the focus lens. For example, when zoom tracking is performed during continuous zooming, if AF drives the focus lens, rapid acceleration or deceleration of the focus lens is likely to occur at the moment AF starts. Rapid acceleration or deceleration causes a delay in controlling the drive speed of the focus lens, resulting in large control deviations. Large control deviations can result in still images being captured that are out of focus, or videos being captured with long periods of out-of-focus. In particular, if the drive direction of the focus lens due to zoom tracking and the drive direction of the focus lens due to AF during zoom tracking are in opposite directions, a reverse drive occurs where the drive direction of the focus lens switches abruptly. Reverse drive is prone to large control deviations.

[0006] However, Patent Document 1 does not disclose a method for suppressing control deviations 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 enable good focusing accuracy even when autofocus is performed during zoom tracking. [Means for solving the problem]

[0008] As one aspect of the present invention, the lens control device moves the variable magnification lens. depending on, The lens control device controls the drive of the focus lens using control information relating to the position of the variable magnification lens and the position of the focus lens according to the subject distance. The lens control device controls the position of the variable magnification lens at a second time point after the first time point, at a first time point. and subject distance at the second time point in accordance with Focus lens First target position The position of the variable magnification lens at the first time point and the second target position of the focusing lens corresponding to the subject distance at the second time point are determined using control information. The means of acquisition, When the subject distance changes from the first time point to the second time point, and the direction of driving the focus lens to the second target position and the direction of driving it to the first target position are opposite to each other, the focus lens is driven to the first target position without being driven to the second target position. It is characterized by having control means. Furthermore, a lens device or imaging device having the above-mentioned lens control device also constitutes another aspect of the present invention.

[0009] Another aspect of the present invention is a lens control method that involves moving the variable magnification lens. depending on, The drive of the focus lens is controlled using control information relating to the position of the variable magnification lens and the position of the focus lens according to the subject distance. The lens control method controls the position of the variable magnification lens at a second time point after the first time point, at a first time point. and subject distance at the second time point in accordance with Focus lens First target position The position of the variable magnification lens at the first time point and the second target position of the focusing lens corresponding to the subject distance at the second time point are determined using control information. Steps to obtain, When the subject distance changes from the first time point to the second time point, and the direction of driving the focusing lens to the second target position and the direction of driving it to the first target position are opposite to each other, the focusing lens is driven to the first target position without being driven to the second target position. The present invention is characterized by having a step. Furthermore, a program that causes a computer to execute a process according to the above lens control method also constitutes another aspect of the present invention. [Effects of the Invention]

[0010] According to the present invention, good focusing accuracy can be obtained even when autofocus is performed during zoom tracking. [Brief explanation of the drawing]

[0011] [Figure 1] A diagram showing the configuration of the interchangeable lens camera system in Example 1. [Figure 2] A diagram showing electronic camera information. [Figure 3] A diagram illustrating the method for calculating the focus position. [Figure 4] A flowchart showing the lens control process in Example 1. [Figure 5] A diagram showing the focus drive trajectory in Example 1. [Figure 6] A flowchart illustrating the lens control process in Example 2. [Figure 7] This figure shows the focus drive when the focus drive direction by zoom tracking and the focus drive direction by AF are different in Example 2. [Figure 8] This figure shows the focus drive in Example 2 when the focus drive direction by zoom tracking and the focus drive direction by AF are the same. [Figure 9] A flowchart showing the lens control process in Example 3. [Figure 10] A diagram showing focus drive when the focus drive direction by zoom tracking and the focus drive direction by AF are different from each other in Embodiment 3. [Figure 11] A diagram showing focus drive when the focus drive direction by zoom tracking and the focus drive direction by AF are the same as each other in Embodiment 3. [Figure 12] A diagram for explaining reverse drive of a focus lens by AF during zoom tracking.

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 an interchangeable-lens camera system according to this embodiment. The interchangeable-lens camera system includes 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 that can form a subject image on an imaging element 201 in the camera body 200, and a lens control unit 105 that can communicate with a camera control unit 207 in the camera body 200.

[0015] The zoom lens 101 includes a variable magnification lens 102, an aperture 103, and a focus lens 104. The variable magnification lens 102 is movable in the optical axis direction in response to operation of a zoom operation ring (not shown) by the user. The focal length of the zoom lens 101 is changed by the movement of the variable magnification lens 102, 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, acting as a lens control device, is a computer including a CPU and is electrically connected to the memory 106, zoom position detection unit 107, aperture drive unit 108, and focus drive unit 109. The lens control unit 105 receives a focus drive command, including the amount of drive 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. This drives the focus lens 104. The lens control unit 105 also receives an aperture drive command from the camera control unit 207 and drives the aperture 103 by controlling the aperture drive unit 108 based on the aperture drive command. Furthermore, the lens control unit 105 receives notification from the camera control unit 207 that imaging has started.

[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 the zoom position information 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 that can be converted to a zoom position, rather than information that indicates the zoom position itself. Information related to the zoom position includes information on the rotation position of the zoom operation ring and information converted from the zoom position to the focal length.

[0018] The aperture drive unit 108 includes an aperture actuator such as a stepping motor or a voice coil motor for driving 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 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] Memory 106 consists of ROM, RAM, etc., and stores electronic cam information as control information regarding the position of the focus lens 104 that focuses on each subject distance for each zoom position (hereinafter referred to as the focus position). In the following explanation, the electronic cam information is described as information of a curve that shows the trajectory (drive trajectory) of the movement of the focus lens 104, but in reality it is table data showing the focus position for each zoom position and subject distance, or information of a function that can calculate the focus position, etc.

[0020] In this embodiment, the zoom lens 101 is an inner-focus (rear-focus) type zoom lens, and the position of the image plane changes as zooming occurs, causing a shift in focus. Therefore, the lens control unit 105 performs zoom tracking, which controls the drive of the focus lens 104 using electronic cam information stored in the memory 106, in order to reduce (compensate for) the change in the image plane position, i.e., the focus shift, during zooming.

[0021] The camera body 200 includes an image sensor 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 image sensor 201 is composed of photoelectric conversion elements such as a CCD sensor or a CMOS sensor, and converts the 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. In this embodiment, the image sensor 201 has imaging pixels that output an imaging signal for generating an image, and a pair of focus detection pixels that have a microlens for pupil division and a pair of photoelectric conversion elements and output a focus detection signal for autofocus.

[0023] The signal processing unit 202 performs various processes on the input imaging signal, such as amplification, noise reduction, and color correction, 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 relative to the subject image using a pair of focus detection signals from the image sensor 201. Specifically, the defocus detection unit 206 detects the phase difference (amount of image shift) between the pair of focus detection signals, calculates the amount of defocus 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 programs recorded in the memory 208 and communicates information necessary for autofocus with the lens control unit 105. The information necessary for autofocus is information about the subject distance (hereinafter referred to as subject distance information) obtained by converting the defocus amount using formulas and coefficients obtained from the imaging relationship of the zoom lens 101. The subject distance information may be information indicating the subject distance itself, or it may be information that can be converted to 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] In this embodiment, the case of using image plane phase-detection autofocus is described, but contrast-detection autofocus may also be used.

[0028] Figure 2 shows electronic cam information, specifically the relationship between the zoom position and the focus position (focus position) required to achieve focus according to the subject distance. In Figure 2, the horizontal axis represents the zoom position, and the vertical axis represents the focus position. The solid curves show the relationship between the zoom position and the focus position for each subject distance (1m, 3m, 5m, and infinity). Memory 106 stores the focus position for each zoom position (or representative zoom position) on the curve corresponding to several representative subject distances as electronic cam information.

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

[0030] On the other hand, if the subject distance differs from a typical subject distance, the focus position can be obtained by calculations such as linear interpolation using electronic camera information corresponding to a typical subject distance in the vicinity of that subject distance.

[0031] Figures 3(a) and 3(b) show a method for calculating the focus position when the subject distance differs from the typical subject distance. In Figure 3, the horizontal axis represents the zoom position and the vertical axis represents the focus position. Figure 3(a) shows the entire electronic camera information, and Figure 3(b) shows a magnified view of the area enclosed in the frame in Figure 3(a).

[0032] This section describes how to calculate the focus position at zoom position y between the wide-angle zoom position x and the telephoto zoom position z at subject distance A', which is a typical distance between subject distances A and B. First, the lens control unit 105 reads the focus positions at subject distances A and B at the wide-angle zoom position x from the electronic cam information and calculates the ratio b / a between the difference a between these and the difference b between the focus positions at subject distances A and A'. Then, using the focus positions at subject distances A and B and the ratio b / a, it calculates the focus position at subject distance A' at the wide-angle zoom position x.

[0033] Next, the lens control unit 105 reads the focus positions at subject distances A and B at the telephoto zoom position z from the electronic cam information. The ratio b' / a' of the difference a' between these two positions and the difference b' between the focus positions at subject distances A and A' is the same as the ratio b / a. Then, using the focus positions at subject distances A and B and the ratio b' / a' (=b / a), the focus position at subject distance A' at the telephoto 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 telephoto-side zoom position z. Then, using the ratio l / (l+m) of the focus position and movement amount at the wide-side and telephoto-side zoom positions x and z at subject distance A', it calculates the focus position at zoom position y at subject distance A'. The lens control unit 105 sets the focus position at zoom position y at subject distance A' calculated in this way as the focus target position and controls the focus lens 104 to drive to this focus target position.

[0035] Next, we will describe the lens control process when the focus lens 104 is driven by AF during zoom tracking in this embodiment.

[0036] Figure 12 shows the focus lens drive trajectory (hereinafter referred to as the focus drive trajectory) when zooming is performed during continuous still image capture (burst shooting) and the focus lens is driven by AF during zoom tracking. The dashed lines show the focus drive trajectory for each subject distance based on electronic cam information. The parts of the solid lines with arrows ZT indicate the focus lens drive trajectory due to zoom tracking. The parts of the solid lines with arrows AF indicate the focus lens drive trajectory due to changes in subject distance acquired by AF. I1, I2, and I3 indicate the points in time when images are taken during burst shooting, and the black circles indicate the focus target position at each point in time when the image is taken.

[0037] As shown in the figure, while the focus lens is driven by zoom tracking, the focus lens is driven by autofocus (AF) at time points I1, I2, and I3. In this figure, the direction of the focus lens drive by AF at time point I1 is opposite to the direction of the focus lens drive by zoom tracking before and after time point I1. In other words, reverse drive of the focus lens occurs. As mentioned above, reverse drive of the focus lens tends to increase the control deviation in the control of the focus lens drive. For this reason, it is preferable to avoid reverse drive of the focus lens even when the subject distance acquired by AF changes.

[0038] The flowchart in Figure 4 shows a lens control process (lens control method) that prevents the reversal drive 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 the program. In the following description, the drive of the focus lens 104 is called focus drive, and the direction in which the focus lens 104 is driven is called the focus drive direction. Also, the point in time when each image is taken in continuous shooting is called the imaging point.

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

[0040] Furthermore, the subject distance information at the next imaging point 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. Alternatively, the subject distance information at the next imaging point may be estimated and obtained from the current subject distance and past subject distances.

[0041] Next, in 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 position.

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

[0043] Next, in step S404, the lens control unit 105 checks the position of the variable magnification lens 102 at the current time or a predetermined time after the current time (both first time points), the subject distance information at the next imaging time, and the information stored in the memory 106. Electronic cam Based on the information, the focus target position B (second target position) at the current time or after a predetermined time is calculated and obtained.

[0044] Next, in step S405, the lens control unit 105, acting as a control means, determines whether the focus drive direction to focus target position A and the focus drive direction to focus target position B are in the same direction. If they are in the same direction, the process proceeds to step S406; otherwise, it proceeds to step S407.

[0045] In step S406, the lens control unit 105 instructs the focus control unit 109 to perform focus drive to the focus target position B. The process from step S401 is then repeated while zooming is in progress.

[0046] In step S407, the lens control unit 105 instructs the focus control unit 109 to stop the focus drive. The process from step S401 is then repeated while zooming is in progress.

[0047] The process shown in Figure 4 is repeatedly executed at a predetermined control cycle. When not imaging, focus is always driven to the focus target position B. The control cycle may always be constant or may change depending on the processing state. Furthermore, as the next imaging time approaches, the estimation accuracy of the zoom position improves, and the calculation accuracy of the focus target position (first target position) also improves. Therefore, by periodically repeating the process in Figure 4, a more accurate focus target position is updated, and focus is driven to that focus target position.

[0048] Figure 5 shows the focus drive trajectory due to the lens control processing in Figure 4, represented by a solid line. I1, I2, and I3 indicate the imaging time during continuous shooting, similar to Figure 12. I2 is the next imaging time after I1, and I3 is the next imaging time after I2. The zoom positions at I1, I2, and I3 are shown as X, Y, and Z, respectively. The dashed lines show the focus drive trajectory for each subject distance (a to d) based on electronic cam information, and hereafter, each focus drive trajectory is referred to as the same distance trajectory. The black circles indicate the focus target position A at the next imaging time, calculated in step S403 of Figure 4. The focus target position A at the next imaging time 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', respectively, calculated in step S404. Note that I2' and I3' may be the same time as the imaging time I1 and I2, or a predetermined time after I1 and I2 (after AF has been performed). The zoom position at I2' is X, and the zoom position at I3' is Y. Furthermore, X2 is the zoom position at which focus drive resumes after the focus drive has stopped between the zoom positions of X and Y.

[0050] As shown in the figure, the focus drive direction to focus target position B at I2' and the focus drive direction to focus target position A at the next imaging time I2 are in opposite directions. In this case, the focus drive is stopped in step S407 in Figure 4. While the zoom position is from X to X2, step S407 is executed for each control cycle of the focus drive, and the focus drive remains stopped.

[0051] When the zoom position reaches X2 at I2″ near the next imaging time I2, the focus drive direction to the focus target position B and the focus drive direction to the focus target position A, calculated at this time (the current time), become the same direction. Therefore, between zoom positions X2 and Y, focus drive to focus target position B is performed in step S406 of Figure 4. Since the focus drive control 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 I2. The same focus drive occurs between zoom positions Y and Z.

[0052] In this embodiment, if the direction of the focus target position relative to the zoom position at a point before the next imaging point and the direction of the focus target position relative to the estimated zoom position at the next imaging point are opposite, the focus drive is stopped. The focus drive is then started when these directions become the same. This makes it possible to avoid reverse drive of the focus lens 104 and reduce control deviation even when AF is performed during zoom tracking (even when the subject distance changes), thereby improving the focusing accuracy at each imaging point. [Examples]

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

[0054] The flowchart in Figure 6 shows the lens control process in this embodiment. First, in step S601 at the present time (first time point), the lens control unit 105 acquires subject distance information for the next imaging time determined by AF from the camera control unit 207, similar to step S401 in Figure 4.

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

[0056] Next, in step S603, the lens control unit 105 calculates the focus target position (first target position) for 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 cam information, similar to step S403.

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

[0058] Figure 7 shows the focus drive trajectory in this embodiment with a solid line. The dashed line, I1, I2, I3, I2', I3', and zoom positions X, Y, Z are the same as in Figure 5.

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

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

[0061] Figure 8 shows the focus drive trajectory with a solid line when 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 I2 (I3) are in the same direction. Even in this case, if the amount of focus drive to the focus target position at I2' is greater than the amount of focus drive to the focus target position at the next imaging time I2, a reverse drive will occur. However, in this embodiment, a reverse drive is not performed by performing the focus drive to the focus target position at I2 in such a way that it does not go beyond the focus target position at I2 to reach (or move toward) the focus target position at I2'.

[0062] In Example 1, if 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 I2 are the same, the focus drive to the focus target position at I2' will be performed without stopping the focus drive. Therefore, reverse drive cannot be avoided. In contrast, in this embodiment, reverse drive can be avoided even in cases like those shown in Figure 8.

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

[0064] Thus, in this embodiment, focus drive is performed without performing reverse drive, so that the focus target position at the next imaging time is reached earlier than the next imaging time. As a result, even if AF is performed during zoom tracking, reverse drive of the focus lens 104 can be avoided and control deviation can be reduced, improving the focusing accuracy at each imaging time. Furthermore, reverse drive patterns that cannot be avoided with the lens control processing in Embodiment 1 can also be avoided in Embodiment 2.

[0065] Furthermore, the advantage of Example 1 is that the control deviation can be reduced due to the small acceleration and deceleration, while the advantage of Example 2 is that reverse drive can be avoided. Therefore, in situations where reverse drive can be avoided in Example 1, focus drive may be performed using the method of Example 1, and in situations where reverse drive can be avoided only in Example 2, focus drive may be performed using the method of Example 2. [Examples]

[0066] Next, Example 3 will be described. In Example 3, focus driving is performed at a speed that reaches the focus target position at the next imaging time. Components common to Example 1 in this example are denoted by the same reference numerals as in Example 1.

[0067] The flowchart in Figure 9 shows the lens control process in this embodiment. First, in step S901 at the present time (first time point), the lens control unit 105 acquires subject distance information for the next imaging time determined by AF from the camera control unit 207, similar to step S401 in Figure 4.

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

[0069] Next, in step S903, the lens control unit 105 calculates the focus target position (first target position) for 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 cam information, similar to step S403.

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

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

[0072] Figure 10 shows the focus drive trajectory in this embodiment with a solid line. The dashed line, I1, I2, I3, I2', I3', and zoom positions X, Y, Z are the same as in Figure 5.

[0073] As shown in the figure, the focus drive direction to the focus target position (black square) at I2' and the focus drive direction to the focus target position (black circle) at the next imaging time I2 are in opposite directions. In the lens control process in Figure 9, focus drive to the focus target position at I2' is not performed, and focus drive to the focus target position at the next imaging time I2 is performed from the beginning at the drive speed calculated in step S904.

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

[0075] Figure 11 shows the trajectory of the focus target position as a solid line when 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 I2 (I3) are in the same direction. Even in this case, if the amount of focus drive to the focus target position at I2' is greater than the amount of focus drive to the focus target position at the next imaging time I2, a reverse drive will occur. However, in this embodiment as well, similar to Embodiment 2, a reverse drive is avoided by performing the focus drive to the focus target position at I2 so as not to exceed the focus target position at I2 and reach the focus target position at I2'. Moreover, since there is no sudden acceleration, deceleration, or stopping of the focus drive, the control deviation of the focus drive can be reduced even more than in Embodiment 2.

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

[0077] In this embodiment, focus drive is performed at a speed that allows the focus target position at the next imaging time to be reached at the next imaging time, without performing reverse drive. As a result, even when AF is performed during zoom tracking, reverse drive of the focus lens 104 is avoided and control deviation is reduced, improving the focusing accuracy at each imaging time.

[0078] Examples 1 to 3 describe the case where focus drive is performed to the focus target position at the next imaging time, which is the second time point in time. However, the focus drive described in each of the above examples may also be performed when focusing to the focus target position at a second time point other than the next imaging time. The second time point other than the next imaging time may be, for example, a time based on the time when subject distance information is acquired by AF (for example, a predetermined time after that time). This makes it possible to perform focus drive in the same way as in each example even when imaging is not performed.

[0079] If the second point in time is the next imaging point, as explained in step S401 of Figure 4, the specific point in time may be estimated based on a signal notifying the imaging point transmitted from the camera control unit 207, or the next imaging point may be communicated from the camera control unit 207. Furthermore, if AF for the next imaging is performed immediately after the completion of the current imaging, it is ideal that the current imaging point and the AF point for achieving focus at the next imaging point approximately coincide. If the current imaging point and the AF point for the next imaging point approximately coincide, the next imaging point as the second point in time can also be estimated based on the AF cycle.

[0080] Furthermore, the second time point is updated each time the camera reaches that second time point. AF may also be performed at time points other than the second time point, as long as subject distance information at that time is obtained.

[0081] Furthermore, a lens control process may be performed by combining the lens control processes of at least two of the embodiments from Examples 1 to 3.

[0082] Furthermore, while Examples 1 to 3 described a case where a lens control device is mounted on a lens device that is detachably attached to an imaging device, the lens control device may also be mounted on an imaging device from which the lens device can be attached or detached, or on an imaging device with an integrated lens.

[0083] The above embodiments include the following configuration.

[0084] (Composition 1) A lens control device that controls the drive of a focus lens using control information relating to the position of the focus lens and the position of the focus lens according to the distance to the subject, in order to reduce focus fluctuations associated with the movement of the variable magnification lens, Acquisition means that, at a first time point, acquires information regarding the position of the variable magnification lens at a second time point after the first time point and information regarding the subject distance at the second time point, and uses the control information to acquire a first target position corresponding to the position of the variable magnification lens at the second time point and the subject distance at the second time point, A lens control device comprising control means for controlling the drive of the focus lens using the first target position. (Configuration 2) The lens control device according to Configuration 1, characterized in that the control means controls the drive of the focus lens using the first target position so that the drive direction of the focus lens does not reverse when the subject distance obtained from the subject distance information changes from the first time point to the second time point. (Composition 3) The acquisition means uses the control information to acquire the position of the variable magnification lens at a time between the first time point and a time point prior to the second time point, and a second target position corresponding to the subject distance at the second time point. The control means is 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, characterized in that the drive of the focus lens is started when the drive direction to the first target position and the drive direction to the second target position are in the same direction. (Composition 4) The acquisition means uses the control information to acquire the position of the variable magnification lens at a time between the first time point and a time point prior to the second time point, and a second target position corresponding to the subject distance at the second time point. The lens control device according to any one of configurations 1 to 3, characterized in that the control means controls the drive of the focus lens so as not to exceed the first target position and reach the second target position if the drive direction of the focus lens to the first target position is the same direction as the drive direction of the focus lens to the second target position and the drive amount of the focus lens to the second target position is greater than the drive amount of the focus lens to the first target position. (Composition 5) The lens control device according to any one of configurations 1 to 4, 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. (Composition 6) The lens control device according to any one of configurations 1 to 4, 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. (Composition 7) The lens control device according to any one of configurations 1 to 6, characterized in that the second time point is the time when imaging is performed. (Composition 8) The lens control device according to any one of configurations 1 to 6, characterized in that the second time point is a time point based on the time point at which information regarding the subject distance is obtained. (Composition 9) An imaging optical system including the variable magnification lens and the focusing lens, A lens device characterized by having a lens control device described in any one of configurations 1 to 8. (Composition 10) The lens device is detachable from the imaging device that images a subject through the imaging optical system. The lens device according to configuration 9, characterized in that the acquisition means acquires information regarding the subject distance from the imaging device. (Composition 11) An image sensor that captures an image of a subject through an imaging optical system including the variable magnification lens and the focusing lens, An imaging apparatus characterized by having a lens control device described in any one of configurations 1 to 8.

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

[0086] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of symbols]

[0087] 100 Lens device 101 Zoom Lens 102 Variable Magnification 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 in accordance with the movement of a variable magnification lens, using control information relating to the position of the variable magnification lens and the position of the focus lens according to the distance to the subject, An acquisition means that, at a first time point, acquires, using the control information, the position of the variable magnification lens at a second time point after the first time point and a first target position of the focus lens corresponding to the subject distance at the second time point, and the position of the variable magnification lens at the first time point and a second target position of the focus lens corresponding to the subject distance at the second time point. A lens control device characterized by having a control means for driving the focus lens to the first target position without driving it to the second target position when the subject distance changes from the first time point to the second time point and the driving direction of the focus lens to the second target position and the driving direction to the first target position are in opposite directions.

2. The control means is If the subject distance changes from the first time point to the second time point, the driving direction of the focus lens toward the first target position and the driving direction toward the second target position are opposite to each other, the driving of the focus lens is stopped. The lens control device according to claim 1, characterized in that the driving of the focus lens to the first target position is started when the driving direction to the first target position and the driving direction to the second target position are in the same direction.

3. The lens control device according to claim 1, characterized in that, when the subject distance changes from the first time point to the second time point, the driving direction of the focus lens toward the first target position and the driving direction of the focus lens toward the second target position are in the same direction, and the amount of driving of the focus lens toward the second target position is greater than the amount of driving toward the first target position, the drive of the focus lens is controlled so as not to move the focus lens beyond the first target position toward the second target position.

4. The lens control device according to claim 1, 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.

5. The lens control device according to claim 1, 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.

6. The lens control device according to claim 1, characterized in that the second time point is the time when imaging is performed.

7. The lens control device according to claim 1, characterized in that the second time point is a time point based on the time point at which the information regarding the subject distance is acquired.

8. An imaging optical system including the variable magnification lens and the focusing lens, A lens device characterized by having the lens control device described in claim 1.

9. The lens device is detachable from the imaging device that images a subject through the imaging optical system. The lens device according to claim 8, characterized in that the acquisition means acquires information regarding the subject distance from the imaging device.

10. An image sensor that captures an image of a subject through an imaging optical system including the variable magnification lens and the focusing lens, An imaging apparatus characterized by having the lens control device described in claim 1.

11. A lens control method that controls the driving of a focus lens using control information relating to the position of the variable magnification lens and the position of the focus lens according to the distance to the subject, in accordance with the movement of the variable magnification lens, Steps include: at a first time point, acquiring a first target position of the focusing lens corresponding to the position of the variable magnification lens at a second time point after the first time point and the subject distance at the second time point, and a second target position of the focusing lens corresponding to the position of the variable magnification lens at the first time point and the subject distance at the second time point, using the control information; A control method characterized by having the step of driving the focus lens to the first target position without driving it to the second target position when the subject distance changes from the first time point to the second time point and the driving direction of the focus lens to the second target position and the driving direction to the first target position are in opposite directions.

12. A program characterized by causing a computer to perform processing according to the lens control method described in claim 11.

Images