FOCUS CONTROL DEVICE, OPTICAL DEVICE, IMAGING DEVICE, AND FOCUS CONTROL METHOD

Abstract

To control a first optical element and a second optical element to maintain the appropriate positional relationship with each other even when they are driven to target positions in focusing.SOLUTION: A focus control unit 105 has creation means 1053, 1055 that create target positions for respective control cycles of a first optical element 103 and a second optical element 104 in focusing, and control means 105 that performs control of moving the first and second optical elements toward the respective target positions for the control cycles. The creation means create a target position of the second optical element in a second control cycle subsequent to a first control cycle by using information on the position and information on the speed of at least one of the first optical element and the second optical element in the first control cycle, and first position data and second position data indicating respective focusing positions of the first optical element and the second optical element for each subject distance.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a technique for controlling the position of an optical element during focusing. [Background technology]

[0002] In some imaging devices, two optical elements move independently in the optical axis direction during focusing. Specifically, the first focus lens moves mainly for focusing, and the second focus lens (floating lens) corrects defocus and aberration caused by the movement of the first focus lens. The appropriate positional relationship between the first and second focus lenses is determined according to the focal length and subject distance, and the positions of the first and second focus lenses are controlled based on lens position data that indicates that positional relationship.

[0003] Patent Document 1 discloses a method for calculating target positions of the first and second focus lenses when the subject distance changes. Specifically, the target position of the first focus lens and the corresponding target position of the second focus lens are calculated from lens position data, and the first and second focus lenses are driven to their respective target positions to control them to have an optimal positional relationship at the target positions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5948645 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 does not mention a method for appropriately maintaining the positional relationship between the first and second focus lenses until they reach their respective target positions (during driving). If the positional relationship between the first and second focus lenses deviates from the appropriate one during driving to the target position, there is a risk that the defocus amount and aberration will increase before a focused state is obtained at the target position.

[0006] The present invention provides a focusing device and the like that can be controlled so that a suitable positional relationship between first and second optical elements is maintained even while the first and second optical elements are being driven to a target position during focusing. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a focus control device comprising: a generating unit for generating a target position for each control period of the first optical element and the second optical element during focusing; A first optical element and and a control unit for controlling the movement of the second optical element toward each of the target positions. The generating unit generates information on the position of at least one of the first optical element and the second optical element in the first control period. and in a first control period of either the first optical element or the second optical element. A target position of the second optical element in a second control period following the first control period is generated using information related to the speed and first position data and second position data indicating the focusing positions of the first optical element and the second optical element for each object distance. The speed information is obtained using information on the position of either one of the optical elements in the first control period and in a control period preceding the first control period. The present invention is characterized by the above.

[0008] A focus control method according to another aspect of the present invention includes the steps of: generating target positions for each control period of a first optical element and a second optical element during focusing; A first optical element and and performing a control step of moving the second optical element toward each of the target positions, the step of generating the target positions including information on the position of at least one of the first optical element and the second optical element in a first control period, In a first control period of either the first optical element or the second optical element,A target position of the second optical element in a second control period following the first control period is generated using information related to the speed and first position data and second position data indicating the focusing positions of the first optical element and the second optical element for each object distance. The speed information is obtained using information on the position of either one of the optical elements in the first control period and in a control period preceding the first control period. A program for causing a computer to execute processing according to the focus control method constitutes another aspect of the present invention. Effect of the Invention

[0009] According to the present invention, the first and second optical elements can be controlled so as to maintain an appropriate positional relationship even while they are being driven to a target position during focusing. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a configuration of a camera system according to an embodiment. [Diagram 2] FIG. 4 is a diagram showing lens position data in the embodiment. [Diagram 3] 6A and 6B are diagrams showing examples of a drive profile of a first focus lens in the embodiment. [Figure 4] 5A and 5B are diagrams showing profile loci of the first and second focus lenses and an ideal locus of the second focus lens in an embodiment. [Diagram 5] FIG. 2 is a block diagram showing the configuration of a lens control unit in the first embodiment. [Figure 6] 6 is a flowchart showing a process of generating a target position of a first focus lens in the first embodiment. [Figure 7] 5A to 5C are diagrams for explaining a process of generating a target position of a second focus lens in the first embodiment. [Figure 8] 6 is a flowchart showing a process of generating a target position of a second focus lens in the first embodiment. [Figure 9] FIG. 11 is a block diagram showing the configuration of a lens control unit in the second embodiment. [Figure 10] 13A to 13C are diagrams for explaining a process for generating a target position of a second focus lens in the second embodiment. [Figure 11] FIG. 11 is a block diagram showing the configuration of a camera system according to a third embodiment. [Figure 12] FIG. 13 is a diagram showing lens position data in the third embodiment. [Figure 13] FIG. 11 is a block diagram showing the configuration of a lens control unit in the third embodiment. [Figure 14] 11 is a flowchart showing a process for generating a target position of a second focus lens in the third embodiment. [Figure 15] 13 is a diagram showing a command speed of a first focus lens and an ideal speed of a second focus lens in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a camera system including a lens device 100 as an optical device according to an embodiment of the present invention, and a lens-interchangeable imaging device (hereinafter referred to as a camera body) 200 to which the lens device 100 is detachably attached. The lens device 100 and the camera body 200 are mechanically and electrically connected via a mount. Power is supplied from the camera body 200 to the lens device 100 and communication is performed between the camera body 200 and the lens device 100 via an electrical terminal provided on the mount.

[0012] The lens device 100 has an optical system 101 including a first focus lens 103 as a first optical element, a second focus lens 104 as a second optical element, and an aperture 102. The optical system 101 forms an image of light from a subject (not shown). The first focus lens 103 moves in the optical axis direction to mainly perform focusing. The second focus lens 104 moves in the optical axis direction during focusing to correct focus deviation and aberration fluctuations. In this embodiment, the sensitivity of the image plane position to the movement of the second focus lens 104 is lower than the sensitivity to the movement of the first focus lens.

[0013] The first focus lens 103 and the second focus lens 104 are driven by a first focus driver 107 and a second focus driver 109, respectively, which include an actuator such as a stepping motor or a vibration motor. The first focus driver 107 and the second focus driver 109 each correspond to a driving means. The positions of the first focus lens 103 and the second focus lens 104 are detected by a first focus position detector 108 and a second focus position detector 110, respectively, which are configured with an optical or magnetic encoder or the like.

[0014] The diaphragm 102 adjusts the amount of light by changing the diameter of the diaphragm opening by moving a plurality of diaphragm blades in the opening / closing direction. The diaphragm 102 is driven by an diaphragm driver 106 including an actuator such as a stepping motor. The lens device 100 of this embodiment is a fixed focal length lens.

[0015] The memory 206 is composed of a ROM, a RAM, etc. The memory 206 stores first lens position data and second lens position data indicating the positions (focusing positions) of the first focus lens 103 and the second focus lens 104 at which a focused state is obtained for each subject distance and aberration is corrected satisfactorily. The first lens position data and the second lens position data correspond to the first position data and the second position data, respectively.

[0016] Lens control unit 105 is a computer including a CPU and the like, and corresponds to a focus control device and functions as a control means. Lens control unit 105 communicates with camera body 200 according to a computer program, and controls aperture drive unit 106 and first focus drive unit 107 in response to commands received from camera body 200 to drive aperture 102 and first focus lens 103. Furthermore, lens control unit 105 drives first focus lens 103 and also controls second focus drive unit 109 to drive second focus lens 104.

[0017] The camera body 200 is composed of an image sensor 201, a signal processing unit 202, a recording processing unit 203, a defocus detection unit 204, a camera control unit 205, a memory 206, an electronic viewfinder 207, and a display unit 208. The image sensor 201 captures (photoelectrically converts) an optical subject image formed by the optical system 101 and outputs an analog image signal. The signal processing unit 202 converts the analog image signal output from the image sensor 201 into a digital image signal and performs various image processes on the digital image signal to generate image data. The recording processing unit 203 displays the generated image data on the electronic viewfinder 207 or the display unit 208, and records the image data for recording in a recording medium such as a semiconductor memory (not shown).

[0018] The defocus detection unit 204 detects the defocus amount by a phase difference detection method using output signals from a plurality of phase difference detection pixels provided in the image sensor 201. The camera control unit 205 is a computer configured with a CPU and the like, and is electrically connected to the recording processing unit 203, the defocus detection unit 204, and the memory 206. The camera control unit 205 reads and executes a computer program recorded in the memory 206, and receives information required for autofocus control from the lens control unit 105. The camera control unit 205 also controls the camera body 200 and the lens device 100 in response to input from a camera operation unit including an imaging switch and various setting switches (not shown).

[0019] Next, a process performed by the lens control unit 105 when a focus command is transmitted from the camera control unit 205 of the camera body 200 to the lens control unit 105 of the lens device 100 will be described. The lens control unit 105 that has received the focus command calculates a target position of the first focus lens 103 based on the focus drive amount included in the focus command, and further calculates a target position of the second focus lens 104 corresponding to the target position of the first focus lens 103. FIG. 2(a) shows the focusing positions of the first focus lens 103 at which a focused state is obtained for each subject distance from the closest distance (MOD) to the infinity distance (INF), and the first lens position data is the data format of this, such as table data. FIG. 2(b) shows the focusing positions of the second focus lens 104 at which a focused state and a good aberration correction state are obtained for the focusing positions of the first focus lens 103 at each subject distance from MOD to INF. The second lens position data is the data format of this, such as table data.

[0020] Here, a case will be described in which the current position of first focus lens 103 is the in-focus position for MOD, and lens control unit 105 receives a focus command from camera control unit 205 to drive first focus lens 103 to the in-focus position for INF. In FIG. 2(a), the current position of the first focus lens 103 is P1m, and the focus position for INF is P1i. In FIG. 2(b), the current position of the second focus lens 104 is P2m, and the focus position for INF is P2i. The lens control unit 105, which has received a focus command, causes the first focus driving unit 107 to drive the first focus lens 103 from P1m to P1i. The first focus lens 103 moves so as to trace the position (trajectory) shown by the curve in FIG. 2(a). At this time, the lens control unit 105 needs to move the second focus lens 104 to a position on the curve in FIG. 2(b) that corresponds to the subject distance and corresponds to the position of the moving first focus lens 103. That is, it is necessary to move the second focus lens 104 from P2m to P2i in synchronization with the first focus lens 103. In other words, the positional relationship between first focus lens 103 and second focus lens 104 is uniquely determined for each subject distance by the first and second lens position data. A method of driving second focus lens 104 in synchronization with the movement of first focus lens 103 will be described below.

[0021] First, the profile drive of the first focus lens 103 will be described. The profile drive is a drive method for driving the lens to trace a predetermined trajectory (position profile) and reach a target position. Fig. 3 shows the time changes in the position, velocity, and acceleration of the first focus lens 103 when the first focus lens 103 is profile driven from P1m to P1i.

[0022] The lens control unit 105 calculates the driving amount of the first focus lens 103 and the second focus lens 104. The driving amount D1 of the first focus lens 103 is expressed as follows: D1 = |P1m-P1i| (1) The drive amount D2 of the second focus lens 104 is calculated as follows: D2 = |P2m-P2i| (2) It is calculated as follows.

[0023] Next, the lens control unit 105 determines a speed V1 for driving the first focus lens 103, and accelerates the first focus lens 103 at a constant acceleration α1 until the speed of the first focus lens 103 reaches V1 at time T1 in FIG. 3. Then, when the speed of the first focus lens 103 reaches V1 at time T2, the acceleration is set to 0, and the speed V1 is maintained until the remaining drive amount reaches the deceleration drive amount. The deceleration drive amount is a distance required for the speed to become 0 when the current speed is decelerated from V1 at an acceleration -α1. When the remaining drive amount reaches the deceleration drive amount at time T3, the lens control unit 105 decelerates the first focus lens 103 at a constant deceleration -α1, and causes it to reach the target position P1i at time T4. The lens control unit 105 generates such a position profile for the drive amount D1.

[0024] Next, a case will be described in which the above-mentioned profile drive is also applied to the second focus lens 104. In Figs. 4(a) and 4(b), the positions of the first focus lens 103 and the second focus lens 104 when the lenses are profile driven are indicated by solid lines. MOD represents the time when the first focus lens 103 starts to be driven from the in-focus position P1m relative to the MOD. INF represents the time when the first focus lens 103 reaches the in-focus position P1i for INF.

[0025] The dashed line in Fig. 4(b) represents the ideal trajectory of the second focus lens 104. The ideal trajectory is calculated from the position of the first focus lens 103 and the first lens position data, and indicates the trajectory that the second focus lens 104 should follow, which is optically set so as to prevent focus deviation and aberration from occurring. However, if the second focus lens 104 is driven independently of the first focus lens 103 so as to follow a profile trajectory indicated by a solid line that is determined in advance by profile driving from P2m to P2i, the second focus lens 104 will move deviating from the ideal trajectory.

[0026] In this embodiment, in order to suppress deviation of the position of second focus lens 104 from the ideal trajectory, second focus lens 104 is not profile driven, but the position of first focus lens 103 is predicted and the position of second focus lens 104 is sequentially determined based on the prediction results.

[0027] In the above-described profile driving, the speed and acceleration are constant, but the speed and acceleration may be changed. EXAMPLES

[0028] FIG. 5 shows a detailed configuration of the lens control unit 105 in the first embodiment. The first position profile generation unit 1051 generates a position profile for profile driving the first focus lens 103. The target position in the position profile generated by the first position profile generation unit 1051 is sent to the first subtractor 1056 for each control period as a command position (information on position) of the first focus lens 103. The command position of the first focus lens 104 is a position obtained from the first lens position data. The first subtractor 1056 calculates the difference between the actual position (real position) of the first focus lens 103 detected by the first focus position detection unit 108 and the command position received from the first position profile generation unit 1051, and sends the difference to the first position controller 1052 as a position deviation.

[0029] The first position controller 1052 performs calculations for PID control. Specifically, the controller 1052 calculates a drive amount for moving the first focus lens 103 to a command position according to the position deviation received from the first subtractor 1056, and outputs the drive amount to the first focus driver 107. The first focus lens 103 is driven from P1m to P1i according to the command position from the first position profile generator 1051 by repeating the above calculations for each control period.

[0030] The first lens target position generation unit 1053 predicts (calculates) a command position of the first focus lens 103 in the next control cycle, and generates the predicted command position as a target position of the first focus lens 103 in the next control cycle. The first lens target position generation unit 1053 and a second lens target position generation unit 1055 described later constitute a generation means.

[0031] 6 is a flowchart showing the process (focus control method) executed by the first lens target position generation unit 1053. In step S301, the first lens target position generation unit 1053 acquires a current cycle command position, which is a command position in the current control cycle (first control cycle: hereinafter referred to as the current control cycle) of the first focus lens 103 generated by the first position profile generation unit 1051. The first lens target position generation unit 1053 overwrites and saves the current cycle command position at that time for each control cycle, and makes it possible to refer to this in the next control cycle as the command position of the previous control cycle (hereinafter referred to as the previous cycle command position).

[0032] Next, in step S302, the first lens target position generation unit 1053 calculates a current period command speed Vcom, which is a command speed (information about speed) in the current control period, by using the difference between the stored previous period command position COMPOSpre1 and the current period command position COMPOSnow1 acquired in step S301. p Then, Vcom is, Vcom=(COMPOSnow1―COMPOSpre1) / T p (2) It is calculated as follows.

[0033] Next, in step S303, the first lens target position generator 1053 calculates a predicted command position of the first focus lens 103 in the next control cycle (second control cycle). Specifically, the predicted command position is calculated on the assumption that the first focus lens 103 will be driven at the same speed (Vcom) in the next control cycle as in the current control cycle, unless there is a change in the driving direction of the first focus lens 103. The predicted command position COMPOSnext1 of the first focus lens 103 is COMPOSnext1 = (Vcom × T p )+COMPOSnow1 (3) It is calculated as follows.

[0034] If the predicted command position COMPOSnext1 calculated in step S303 exceeds the final target position P1i of the first focus lens 103, the first lens target position generation unit 1053 sets the target position P1next of the next control cycle of the first focus lens 103 to P1i. On the other hand, if COMPOSnext1 does not exceed P1i, it sets P1next to COMPOSnext1.

[0035] The second lens target position generation unit 1055 calculates a target position P2next in the next control cycle of the second focus lens 104. The target position of the second focus lens 104 is a position obtained from the second lens position data. Fig. 8 shows a flowchart of the process (focus control method) executed by the second lens target position generation unit 1055.

[0036] In step S401, the second lens target position generation unit 1055 calculates the subject distance for the next control cycle using the target position P1next of the first focus lens 103 generated by the first lens target position generation unit 1053 and the first lens position data shown in Fig. 2(a). The first lens position data is described as continuous data in Fig. 2(a), but is actually a set of finite data provided for a number of representative subject distances. If P1next is not included in the first lens position data, the subject distance corresponding to P1next is calculated by performing linear interpolation using the subject distances for the two positions of the first focus lens 103 adjacent to P1next.

[0037] Next, in step S402, the second lens target position generation unit 1055 calculates a predicted command position COMPOSnext2 in the next control cycle of the second focus lens 104 corresponding to the subject distance calculated in step S401, using the second lens position data shown in Fig. 2(b). Then, if there is no change in the drive direction of the second focus lens 104 and COMPOSnext2 exceeds P2i which is the final target position, the second lens target position generation unit 1055 sets the target position P2next in the next control cycle of the second focus lens 104 to P2i. On the other hand, if COMPOSnext2 does not exceed P2i, it sets P2next to COMPOSnext2.

[0038] 7(a) and (b) show the process of generating the target position P2next (=COMPOSnext2) of the second focus lens 104 described above. FIG. 7(a) shows each position of the first focus lens 103, and FIG. 7(b) shows each position of the second focus lens 104. COMPOSpre2 indicates the command position of the second focus lens 104 in the previous control cycle, and COMPOSnow2 indicates the command position of the second focus lens 104 in the current control cycle. pre , T now、 T next indicate the time of the previous control cycle, the time of the current control cycle, and the time of the next control cycle, respectively. The control cycle is T p It is.

[0039] The target position of second focus lens 104 generated by second lens target position generation unit 1055 is sent to second subtractor 1057. Second subtractor 1057 calculates the difference between the actual position of second focus lens 104 detected by second focus position detection unit 110 and the target position, and sends the difference to second position controller 1054 as the position deviation of second focus lens 104.

[0040] In order to perform PID control similarly to the first position controller 1052, the second position controller 1054 calculates a drive amount for moving the second focus lens 104 toward the target position and outputs the drive amount to the second focus driver 109. As a result, the second focus lens 104 is driven toward the target position.

[0041] As described above, according to this embodiment, the second focus lens 104 is driven to follow the second lens position data while synchronizing with the first focus lens 103. This makes it possible to suppress the occurrence of focus deviation and aberration fluctuations due to the synchronization deviation of the first and second focus lenses 103 and 104 when the subject distance changes. That is, during focusing, the first and second focus lenses 103 and 104 can be controlled to maintain an appropriate positional relationship even while they are driven to the final target position. Furthermore, in this embodiment, the position of the first focus lens 103 is predicted to calculate the target position of the second focus lens 104. Therefore, it is possible to reduce the tracking delay of the second focus lens 104 with respect to the second lens position data when the second focus lens 104 is driven by feedback control. EXAMPLES

[0042] Fig. 9 shows a detailed configuration of a lens control unit 105' in Example 2. In Fig. 9, components common to those in Fig. 5 are given the same reference numerals as in Fig. 5.

[0043] This embodiment differs from the first embodiment in that a first position profile generating unit 1051 generates a command position of the first focus lens 103, and a second lens ideal position generating unit 1058 generates an ideal position of the second focus lens 104 from the command position and the second lens position data. Also, this embodiment differs from the first embodiment in that a second lens target position generating unit 1059 calculates a target position of the second focus lens 104 in the next control cycle from an ideal position (information about the position) and an ideal speed (information about the speed) of the second focus lens 104 in the current control cycle. The ideal position, ideal speed, and target position of the second focus lens 104 are positions obtained from the second lens position data. The second lens target position generating unit 1059 constitutes a generating means together with a second lens target position generating unit 1059 described later.

[0044] Figures 10(a) and (b) show the process of generating a target position of the second focus lens 104 in this embodiment. Figure 10(a) shows each position of the first focus lens 103 also shown in Figure 7(a), and Figure 10(b) shows each position of the second focus lens 104. Idealpre indicates the ideal position of the second focus lens 104 in the previous control cycle (hereinafter referred to as the previous cycle ideal position), and Idealnow indicates the ideal position of the second focus lens 104 in the current control cycle (hereinafter referred to as the current cycle ideal position). Idealnext indicates the ideal position of the second focus lens 104 in the next control cycle (hereinafter referred to as the next cycle ideal position).

[0045] 8, the second lens ideal position generation unit 1058 calculates the subject distance in the current control cycle using the current cycle command position of the first focus lens 103 and the first lens position data. Furthermore, it calculates the current cycle ideal position Idealnow of the second focus lens 104 using the subject distance in the current control cycle and the second lens position data. Then, the second lens ideal position generation unit 1058 sends the calculated current cycle ideal position Idealnow to the second lens target position generation unit 1059.

[0046] 6, the second lens target position generation unit 1059 calculates a current cycle ideal velocity using the current cycle ideal position Idealnow and the previous cycle ideal position Idealpre of the second focus lens 104 from the second lens ideal position generation unit 1058. In addition, the second lens target position generation unit 1059 predicts a next cycle ideal position Idealnext of the second focus lens 104 from the current cycle ideal position Idealnow and the current cycle ideal velocity.

[0047] Then, if there is no change in the driving direction of the second focus lens 104 and Idealnext exceeds the final target position P2i of the second focus lens 104, the second lens target position generation unit 1059 sets the target position P2next in the next control cycle of the second focus lens 104 to P2i. On the other hand, if the next cycle ideal position Idealnext does not exceed P2i, the second lens target position generation unit 1059 sets the target position P2next to Idealnext.

[0048] While the first embodiment predicts the command position of the first focus lens 103 in the next control cycle, the present embodiment is characterized in that it predicts the ideal position of the second focus lens 104 in the next control cycle. This embodiment is preferably used when the variation in the ideal speed of the second focus lens 104 is smaller than the variation in the command speed of the first focus lens 103, such as when the change in the position of the first focus lens 103 in the first lens position data is large. This makes it possible to improve the accuracy of synchronization of the drive of the second focus lens 104 with the drive of the first focus lens 103. EXAMPLES

[0049] FIG. 11 shows the configuration of a camera system of the third embodiment. A lens device 100″ in this embodiment is a lens device capable of zooming, and an optical system 101″ includes a variable magnification lens 112. The lens device 100″ has a zoom operation unit 113 and a zoom position detection unit 114. In FIG. 11, components common to those in FIG. 1 are denoted by the same reference numerals as in FIG. 1.

[0050] The variable magnification lens 112 is driven in the optical axis direction in response to a user operation of a zoom operation unit 113, and changes the focal length of the optical system 101". A zoom position detection unit 114 detects the position (zoom position) of the variable magnification lens 112, and sends information on the zoom position to the lens control unit 105.

[0051] The first and second lens position data in this embodiment indicates the positions of the first and second focus lenses 103, 104 for each focal length and each subject distance, as shown in Figures 12(a) and (b). Figures 12(a) and (b) show the first and second lens position data for seven representative subject distances: MOD, 0.7 m, 1.0 m, 3.0 m, 5.0 m, and INF. By limiting the number of pieces of first and second lens position data in this way, it is possible to reduce the storage capacity required for the memory 111 that stores them.

[0052] When determining the position of each focus lens for a non-representative subject distance, for example, 2.0 m, an interpolation calculation is performed using lens position data for 1.0 m and 3.0 m. Similarly, when determining the position of each focus lens for 4.0 m, an interpolation calculation is performed using lens position data for 3.0 m and 5.0 m. Although the focal length is also shown as continuous lens position data in the figure, in reality, lens position data for a number of representative focal lengths is stored in the memory 111. To determine the position of each focus lens at a non-representative focal length, an interpolation calculation is performed using lens position data at focal lengths adjacent to that focal length.

[0053] FIG. 13 shows a detailed configuration of the lens control unit 105″ in this embodiment. In FIG. 13, components common to those in FIG. 5 are given the same reference numerals as in FIG. 5. The lens control unit 105″ has a prediction method selection unit 1060 and a second lens target position generation unit 1061.

[0054] The prediction method selection unit 1060 selects a prediction method using the zoom position in the current control cycle detected by the zoom position detection unit 114 and the prediction method data stored in the memory 111. There are a first prediction method for predicting a next cycle command position of the first focus lens 103 and a second prediction method for predicting a next cycle command position of the second focus lens 104. The prediction method data is data indicating which of the first and second prediction methods is to be selected for each zoom position. The prediction method selection unit 1060 sends information on the prediction method selected according to the prediction method data to the second lens target position generation unit 1061.

[0055] The flowchart in FIG. 14 shows the process executed by the second lens target position generation unit 1061. In step S501, the second lens target position generation unit 1061 determines whether the prediction method acquired from the prediction method selection unit 1060 is the first prediction method, and if it is the first prediction method, proceeds to steps S502 and S503. In steps S502 and S503, the second lens target position generation unit 1061 performs the same process as the process by the first lens target position generation unit 1053 and the second lens target position generation unit 1055 described in the first embodiment to calculate the target position of the second focus lens 104 in the next control cycle. On the other hand, if the prediction method acquired from the prediction method selection unit 1060 is the second prediction method, the second lens target position generation unit 1061 proceeds to steps S504 and S505. In steps S504 and S505, the two lens target position generation unit 1061 generates a target position for the second focus lens 104 by performing processing similar to the processing performed by the second lens ideal position generation unit 1058 and the second lens target position generation unit 1059 described in the second embodiment.

[0056] Hereinafter, a method of determining a prediction method for each zoom position in this embodiment will be described. Here, a case will be described in which the first focus lens 103 is driven to a command position when the subject distance changes from INF to MOD for each zoom position. The driving method of the first focus lens 103 here is not a driving method that keeps the maximum speed constant as described in the first embodiment, but a driving method that keeps the image plane speed (movement speed of the image plane position) specified by the camera body 200 constant, for example. In this case, the memory 111 holds sensitivity data that indicates the movement amount of the image plane position relative to the unit movement amount of the first and second focus lenses 103 and 104, and the specified image plane speed can be converted to a command speed of the first focus lens 103 by using the sensitivity data. If speed control is performed with this command speed as the target speed of the first focus lens 103, the speed of the first focus lens 103 will not be constant but will fluctuate.

[0057] FIG. 15(a) shows the command speed of the first focus lens 103 when the command position of the first focus lens 103 is profiled so as to keep the image plane speed constant when the zoom position is at the TELE end. FIG. 15(b) shows the ideal speed of the second focus lens 104 for each control period under the same conditions. INF is the time when the first focus lens 103 starts to be driven from the position corresponding to the object distance INF, and T MOD is the time when the first focus lens 103 reaches the position of the object distance MOD. INF From T MOD The start times of each control period up to the end of the control period are shown.

[0058] In the first prediction method, prediction is performed based on the command speed of the first focus lens 103. Therefore, the magnitude D1 of the variation in prediction accuracy in the first prediction method is basically the variation in the command speed of the second focus lens 104 in each control cycle. Therefore, the magnitude D A is the variation D of the command speed of the second focus lens 104 in the control period N (=a1 to a5). a1 ~Da5 Using D A =D a1 +…+D a5 (4) It is expressed as:

[0059] In the second prediction method, prediction is performed based on the ideal speed of the second focus lens 104. Therefore, the degree of variation in prediction accuracy in the second prediction method D B is the variation D of the ideal speed of the second focus lens 104 in the control period N (=b1 to b5). b1 ~D b5 Using D B =D b1 +…+D b4 (5) This is expressed as:

[0060] In this embodiment, at the TELE end, A and D B The command position and ideal position are determined to be the smaller prediction method of D1 and D2. The command position and ideal position can be obtained by a simulation using each lens position characteristic data and sensitivity data. This simulation is performed for all zoom positions, and the first prediction method or the second prediction method to be used at each zoom position is determined according to the rule that the smaller of D1 and D2 is used. Then, prediction method data indicating the determination result at each zoom position is stored in the memory 111.

[0061] According to this embodiment, by using an appropriate prediction method for each zoom position, the accuracy of synchronization of the drive of the second focus lens 104 with the drive of the first focus lens 103 due to changes in the subject distance at each zoom position is improved. This makes it possible to effectively reduce aberrations and shorten the time required to obtain a focused state.

[0062] In each of the above embodiments, a case has been described in which the second focus lens is driven in synchronization with the drive of the first focus lens, but an image sensor may be used as the second optical element, and the image sensor may be driven in the optical axis direction in synchronization with the drive of the first focus lens.

[0063] In the above embodiments, the focus control device (lens control unit) is provided in the lens device, but the focus control device may be provided in the camera body, and the camera body may control the driving of the first and second focus lenses in the lens device. Furthermore, the focus control device may be provided in a lens-integrated imaging device that has an optical system built in, or may be a focus control device that can be attached externally to the lens device or imaging device. (Other Examples) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0064] The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0065] 100,100″ lens system 103 First focus lens 104 Second Focus Lens 105,105′,105″ Lens control section 107 First focus drive unit 109 Second focus drive unit

Claims

1. a generating unit that generates a target position for each control period of the first optical element and the second optical element during focusing; a control unit that performs control to move the first optical element and the second optical element toward the respective target positions in each control cycle, The generating means includes: generating the target position of the second optical element in a second control period following the first control period using information on a position of at least one of the first optical element and the second optical element in a first control period, information on a speed of either one of the first optical element and the second optical element in the first control period, and first position data and second position data indicating focusing positions of the first optical element and the second optical element for each subject distance; A focus control device, characterized in that the speed information is acquired using information on the position of the either one of the optical elements in each of the first control period and a control period preceding the first control period.

2. The generating means includes: generating the target position of the first optical element in the second control period using information about the position of the first optical element in the first control period and information about the velocity obtained using information about the position of the first optical element in each of the first control period and a control period preceding the first control period; 2. The focus control device according to claim 1, further comprising: a focus control unit for controlling a focus of the first optical element in the second control cycle; a focus control unit for controlling the first optical element in the second control cycle; a focus control unit for controlling the second optical element in the second control cycle;

3. 3. The focus control device according to claim 2, wherein the information relating to the position and the information relating to the velocity of the first optical element indicate a command position and a command velocity, respectively, from the control means to a drive means that drives the first optical element.

4. The generating means includes: generating information about the speed of the second optical element in the first control period using information about the position of the first optical element in the first control period, the first position data, the second position data, and information about the position of the second optical element in the first control period and a control period preceding the first control period; The focus control device according to claim 1, characterized in that the target position of the second optical element in the second control cycle is generated using information regarding the position of the second optical element in the first control cycle and information regarding the speed of the second optical element in the first control cycle.

5. the information about the position of the first optical element indicates a command position from the control means to a driving means that drives the first optical element, 5. The focus control device according to claim 4, wherein the information regarding the position and the information regarding the velocity of the second optical element respectively indicate a position and a velocity obtained from the second position data.

6. an optical system including the first optical element and the second optical element is capable of zooming; the first position data and the second position data are data for each focal length of the optical system and each subject distance, The generating means, in response to the focal length, a first generation method for generating the target position of the first optical element in the second control period using information on the position of the first optical element in the first control period and information on the velocity obtained using information on the position of the first optical element in the first control period and a control period preceding the first control period, and for generating the target position of the second optical element in the second control period using the target position of the first optical element in the second control period, the first position data, and the second position data; The focus control device according to claim 1, characterized in that one of a second generation method is selected to generate information about the velocity of the second optical element in the first control cycle using information about the position of the first optical element in the first control cycle, the first position data, the second position data, and information about the position of the second optical element in the first control cycle and a control cycle prior to the first control cycle, and a target position of the second optical element in the second control cycle is generated using information about the position of the second optical element in the first control cycle and information about the velocity of the second optical element in the first control cycle.

7. 5. The focus control device according to claim 1, wherein a sensitivity of the image plane position to the movement of the second optical element is lower than the sensitivity to the movement of the first optical element.

8. A focus control device according to any one of claims 1 to 7, An optical device comprising the first optical element and the second optical element.

9. The focus control device according to any one of claims 1 to 7, An imaging device, comprising: an imaging device that performs imaging using the first optical element and the second optical element.

10. generating target positions for each control period of the first optical element and the second optical element during focusing; performing control for moving the first optical element and the second optical element toward the respective target positions for each control period; in the step of generating the target position, the target position of the second optical element in a second control period following the first control period is generated using information on a position of at least one of the first optical element and the second optical element in a first control period, information on a speed of either one of the first optical element and the second optical element in the first control period, and first position data and second position data indicating focusing positions of the first optical element and the second optical element for each subject distance, A focus control method comprising: acquiring the speed information using information on the position of the one of the optical elements in each of the first control period and a control period preceding the first control period.

11. A program for causing a computer to execute a process according to the focus control method according to claim 10.

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