JP7802591B2 - Control device, lens device, imaging device, control method, and program - Google Patents

Description

The present invention relates to a control device, a lens device, an imaging device, a control method, and a program.

Autofocusing (AF) processes are known that drive optical elements by obtaining a defocus amount based on the phase difference between a pair of image signals corresponding to light beams passing through different regions of the exit pupil of an imaging optical system. Furthermore, in video capture, so-called full-time AF, which performs continuous autofocusing, can sometimes result in undesirable situations, such as focusing on a subject that passes in front of the subject currently being focused on.

Patent document 1 discloses a control method that prevents the focus lens from being driven if the target position of the focus lens is outside the allowable range of movement (position) of the focus lens.

Patent No. 4850692

In the method disclosed in Patent Document 1, if the target position of the focus lens is outside the allowable range of the focus lens position, the focusing operation is not performed even if the target position corresponds to the subject intended by the user. The present invention aims to provide a control device that is advantageous, for example, in terms of automatic focusing on the subject intended by the user.

A control device as one aspect of the present invention has an acquisition unit that acquires a defocus amount of an imaging optical system including a focus lens unit, and a generation unit that generates a drive command for the focus lens unit based on the defocus amount, and the generation unit generates the drive command based on information regarding the amount of change per unit time in the object distance of the imaging optical system relative to the amount of movement of the focus lens unit.

Other objects and features of the present invention are described in the following examples.

The present invention can provide a control device that is advantageous, for example, in terms of automatically focusing on a subject intended by the user.

FIG. 1 is a block diagram of an imaging apparatus according to a first embodiment. 10 is a flowchart illustrating an automatic focus adjustment process in the first embodiment. 10 is a flowchart illustrating a process for generating a focus drive command in the first embodiment. 5 is an explanatory diagram of the relationship between the zoom lens drive state and the focus drive command value (drive speed) in the first embodiment. FIG. 5 is an explanatory diagram of the relationship between the zoom lens drive state and the focus drive command value (drive amount) in the first embodiment. FIG. 10 is a flowchart illustrating a process for generating a focus drive command in the second embodiment. 10 is an explanatory diagram of the relationship between the sensitivity change amount and the focus drive command value (drive speed) in the second embodiment. 11 is a flowchart illustrating a process for generating a focus drive command in the third embodiment. 10A and 10B are explanatory diagrams of a method for detecting a change in a subject in the third embodiment. 11A and 11B are explanatory diagrams of the relationship between the zoom lens driving state or sensitivity change amount and the method of detecting a change in a subject in the third embodiment. FIG. 10 is a block diagram of an imaging device as a modified example of each embodiment.

Embodiments of the present invention will now be described in detail with reference to the drawings. In each drawing, identical components will be designated by the same reference numerals, and duplicate descriptions will be omitted.

First, a first embodiment of the present invention will be described with reference to Figures 1 to 5. The control device of this embodiment changes the responsiveness (drive command including at least one of the drive amount or drive speed) of the focus lens during automatic focusing (AF) based on the drive state (drive speed, drive direction, or drive position) of the zoom lens used for magnification variation.

Figure 1 is a block diagram of an imaging device 10. The imaging device 10 has a lens device 100 and a camera body 200. Note that in the imaging device 10, the lens device 100 and the camera body 200 are configured as an integrated unit, but this is not limited to this, and the lens device 100 may be configured to be detachable from the camera body 200.

The lens device 100 has an imaging optical system 101 with multiple optical components. A light beam passing through the imaging optical system 101 is incident on an image sensor 107. The imaging optical system 101 includes a focus lens (focus lens unit) 102, a zoom lens (zoom lens unit) 103, an aperture stop (aperture stop) 104, a spectral prism 105, and a relay lens 106. The focus lens 102 is moved in a direction along the optical axis OA (optical axis direction) by a focus motor (not shown) to change the position of the image plane (object distance) of the lens device 100. The zoom lens 103 is moved in the optical axis direction by a zoom motor (not shown) to change the focal length of the lens device 100. The zoom lens 103 may also be manually operable using an operating member (not shown). The aperture 104 is driven by an iris motor (not shown) to limit the light beam incident on the image sensor 107. The spectral prism 105 splits the light beam that has passed through the focus lens 102 and zoom lens 103 into two light beams. One of the light beams that has passed through the spectral prism 105 passes through a relay lens 106 and enters an image sensor 107. The other light beam that has been reflected by the spectral prism 105 enters a focus detection unit 108.

The focus detection unit 108 has a glasses lens and a phase difference sensor. The glasses lens splits two light beams, and the phase sensor photoelectrically converts (captures; captures) a pair of images (two images) formed by the two light beams. The defocus calculation unit 109 calculates the phase difference based on a pair of image signals corresponding to a portion of the light beam photoelectrically converted by the focus detection unit 108, and calculates the defocus amount. The memory 110 is a non-volatile memory such as a flash ROM, and stores the amount of change (sensitivity) in the image plane (object distance) per unit movement of the focus lens 102, which changes depending on the positions of the focus lens 102 and zoom lens 103. The sensitivity calculation unit (calculation means) 111 calculates the current sensitivity based on the sensitivity stored in the memory 110, position information of the focus lens 102, position information of the zoom lens 103, and the defocus amount calculated by the defocus calculation unit 109.

The drive command unit 112 generates a drive command (control signal) for controlling the drive of the focus lens 102 based on the defocus amount calculated by the defocus calculation unit 109 and the sensitivity calculated by the sensitivity calculation unit 111. The drive command unit 112 is a control unit (control device) that has the functions of an acquisition unit 112a that acquires the defocus amount and a generation unit 112b that generates a drive command for the focus lens 102 that constitutes the imaging optical system 101 based on the defocus amount. In this embodiment, the drive command is, for example, one or both of the drive amount and drive speed of the focus lens 102 (at least one of the drive amount and drive speed).

The lens driving unit 113 controls the driving of the focus lens 102 based on the driving command calculated by the driving command unit 112. The lens driving unit 113 also receives driving commands for the zoom lens 103 and the diaphragm 104, and controls the driving of the zoom lens 103 and the diaphragm 104, respectively. The driving command for the zoom lens 103 or the driving command for the diaphragm 104 may be received from the camera body 200 or from a controller operated by the user.

The lens position detection unit 114 independently detects the positions of the focus lens 102, zoom lens 103, aperture 104, and relay lens 106. The lens position detection unit 114 has position detection means such as an encoder or potentiometer.

Figure 2 is a flowchart showing the automatic focus adjustment process (AF process) in this embodiment. First, in step S201, the focus detection unit 108 determines exposure conditions such as the photoelectric conversion time and gain of the phase difference sensor and activates the phase difference sensor. Here, the exposure conditions may be determined by feedback based on information from the previous activation of the phase difference sensor, or may be determined by an auto gain control function that stops the phase difference sensor when predetermined luminance information is obtained.

Next, in step S202, the defocus calculation unit 109 performs a phase difference calculation on the image signal obtained from the phase difference sensor to calculate the phase difference. The defocus calculation unit 109 also converts the calculated phase difference into a defocus amount. Note that the methods for calculating the phase difference and converting it into a defocus amount are well-known technologies, so their explanation will be omitted.

Next, in step S203, the drive command unit 112 generates a drive command (focus drive command) based on the defocus amount calculated by the defocus calculation unit 109. Here, the focus drive command is at least one of the drive speed and drive amount of the focus lens 102. Next, in step S204, the lens drive unit 113 controls the drive of the focus lens 102 based on the focus drive command generated in step S203.

Note that with the full-time AF function, control is performed so that automatic focus adjustment is always performed in accordance with the movement of the subject during shooting, so steps S201 to S204 are executed repeatedly. However, this embodiment is not limited to this, and may also be applied to a function that performs automatic focus adjustment only while the user is operating the camera (such as so-called one-shot AF).

Figure 3 is a flowchart showing the process of generating a focus drive command in this embodiment. First, in step S301, the drive command unit 112 acquires the defocus amount calculated by the defocus calculation unit 109. Next, in step S302, the drive command unit 112 acquires position information of the focus lens 102 and position information of the zoom lens 103 detected by the lens position detection unit 114. Next, in step S303, the drive command unit 112 acquires the sensitivity calculated by the sensitivity calculation unit 111.

Next, in step S304, the drive command unit 112 calculates the focus target position using the defocus amount, focus position information, and sensitivity acquired in steps S301 to S303. The focus target position can be calculated by adding the focus drive amount obtained by multiplying the defocus amount by the sensitivity to the current focus position information. Note that this method is a well-known technique, so its explanation will be omitted.

Next, in step S305, the drive command unit 112 calculates the drive speed and drive direction of the zoom lens 103 based on the history data (history information) of the zoom position information acquired in step S302 (zoom position information acquired multiple times). In this embodiment, the drive speed and drive direction of the zoom lens 103 are calculated based on the history data of the zoom position information, but this is not limited to this and calculations may be made by other means. For example, calculations may be made from the motor output value, or command values may be acquired from a controller.

Next, in step S306, the drive command unit 112 determines a focus drive command value (drive amount and drive speed of the focus lens 102) based on the focus target position calculated in step S304 and the drive state of the zoom lens 103 (zoom lens drive state). The zoom lens drive state is information related to at least one of the zoom lens position acquired in step S302 and the zoom lens drive speed and drive direction calculated in step S305. The reason for taking the zoom lens drive state into consideration when determining the focus drive command value is that zoom lens drive can cause changes in focus detection results and sensitivity, which can result in changes in the focus target position. There are cases where it is desirable for the focus lens 102 to respond sensitively to changes in such focus target position, and cases where it is not. In this embodiment, this can be switched depending on the zoom lens drive state. There are various possible methods for determining the focus drive command value, and examples of these will be described below with reference to Figures 4(a), (b), and 5.

Figures 4(a) and (b) are explanatory diagrams of the relationship between the zoom lens drive state and the focus drive command value (drive speed). Figure 4(a) shows an example where the zoom lens 103 is driven in the direction (TELE direction) from the wide-angle side (WIDE side) to the telephoto side (TELE side). Figure 4(b) shows an example where the zoom lens 103 is driven in the direction (WIDE direction) from the telephoto side to the wide-angle side. In Figures 4(a) and (b), the horizontal axis represents the zoom lens drive speed, and the vertical axis represents the focus drive command value (speed).

As shown in Figure 4(a), when driving the zoom lens 103 in the TELE direction, the drive command value is determined so that the drive speed in the focus drive command value becomes (relatively) faster as the zoom lens drive speed increases. Generally, the closer to the TELE side, the higher the sensitivity, and the sensitivity increases when driving the zoom lens in the TELE direction. The reason for determining the drive command value in this way is that as sensitivity increases, even a slight deviation in the focus target position results in a large defocus, so quickly controlling the focus target position reduces the sense of discomfort felt by the user. Furthermore, when sensitivity is high, even a small change in subject distance is detected as a large defocus, so changes in focus detection results due to changes in subject distance are larger relative to changes in focus detection results due to other factors (such as noise). This allows the focus target position to be calculated with high accuracy, and even if the focus lens is made to respond sensitively, it is less likely to lead to malfunctions (such as hunting or overshooting).

As shown in Figure 4(b), when the zoom lens 103 is driven in the WIDE direction, the drive command value is determined so that the drive speed in the focus drive command value becomes (relatively) slower as the zoom lens drive speed increases. Generally, the closer to the WIDE side, the lower the sensitivity, and when the zoom lens is driven in the WIDE direction, the sensitivity decreases. The reason for determining the drive command value in this way is that when sensitivity is low, even small changes in subject distance are detected as small defocus, so changes in the focus detection result due to changes in subject distance are relatively small compared to changes in the focus detection result due to other factors (noise, etc.). As a result, changes in the focus target position due to noise, etc. become larger, and making the focus lens respond sensitively can easily lead to hunting, etc.

This type of control is also effective when considering operations such as zooming out from the TELE side to the WIDE side on the same subject, and then immediately zooming back up to the TELE side. This is because, for the reasons mentioned above, the focus detection results on the TELE side are relatively accurate, so if the focus target position is immediately followed while driving to the WIDE side, defocusing may occur when driving back to the TELE side.

In this embodiment, an example has been described in which the focus drive speed is changed depending on the zoom lens drive speed and drive direction, but the focus drive speed may also be changed depending on the zoom lens drive position. Also, while an example has been described in which the focus drive speed is changed linearly depending on the zoom lens drive speed, it may also be changed non-linearly. Alternatively, a setting means may be provided that allows the user to set the focus drive speed, and the speed may be changed relatively based on the set speed, or the slower (or faster) of the set speed and the calculated speed may be used.

Figure 5 is an explanatory diagram of the relationship between the zoom lens drive state and the focus drive command value (drive amount). In Figure 5, the horizontal axis represents the zoom lens position, and the vertical axis represents the focus drive command value (drive amount). In this example, when the zoom lens drive position is on the WIDE side, the drive amount in the focus drive command value is small (smaller than the drive amount required to reach the focus target position), and when the zoom lens drive position is on the TELE side, the drive amount is large (the drive amount required to reach the focus target position).

The reason for this is that, as explained with reference to Figures 4(a) and (b), sensitivity generally increases toward the TELE side, so changes in focus detection results due to changes in subject distance are relatively large compared to changes in focus detection results due to other factors (noise, etc.). On the other hand, on the WIDE side, defocus changes due to noise, etc. cause large changes in the focus target position, so the actual drive amount is smaller than the detected drive amount.

In this embodiment, an example has been described in which the focus drive amount is changed according to the zoom lens position, but the focus drive amount may also be changed according to the zoom lens speed. Also, while an example has been described in which the focus drive amount is changed linearly, it may also be changed nonlinearly. Alternatively, if the zoom position is closer to the WIDE side than the predetermined position, the drive amount may be set to zero (no drive). For example, this type of processing is preferable in cases where the sensitivity is too low on the WIDE side of the predetermined position, causing the entire screen to be in focus without focus adjustment, or when changes in focus detection results due to noise or the like have a significant impact on operation. Note that the content described with reference to Figures 4(a), (b), or 5 may be applied to either or both of them.

In this embodiment, the drive command value (drive speed and drive amount) for the focus lens in the focus adjustment operation is changed depending on the zoom lens drive state. In other words, the focus adjustment process (AF operation) is performed while switching the responsiveness of the drive command value depending on whether or not a sharp response is required to changes in the focus detection result caused by movement of at least one optical member (e.g., zoom lens 103) that makes up the imaging optical system 101. This makes it possible to reduce the occurrence of defocus caused by movement of the optical member. Note that while this embodiment has been described as an example focusing on the drive state of the zoom lens, it can be similarly applied to any optical member (e.g., focus lens 102) that can cause changes in the focus detection result.

Next, a second embodiment of the present invention will be described with reference to Figures 6 and 7. This embodiment changes the responsiveness (drive amount or drive speed) of the focus lens during automatic focus adjustment based on the amount of change in sensitivity per unit time (direction or rate of change).

Figure 6 is a flowchart showing the focus drive command generation process in this embodiment. Note that steps S301 to S304 in Figure 6 are the same as those in Figure 3 described in Example 1, so their description will be omitted.

After performing step S304, the process proceeds to step S605. In step S605, the drive command unit 112 calculates the sensitivity variation, i.e., the variation in sensitivity per unit time (the direction or rate of change in sensitivity), based on the historical data (history information) of the sensitivity acquired in step S303 (sensitivity acquired multiple times).

Next, in step S606, the drive command unit 112 determines a focus drive command value (drive amount and drive speed of the focus lens 102) based on the focus target position calculated in step S304 and the sensitivity change amount calculated in step S605. The reason for taking the sensitivity change amount into consideration when determining the focus drive command value is that the focus detection results and sensitivity change when the zoom lens or focus lens is driven, which can result in a change in the focus target position. There are cases where it is desired for the focus lens 102 to respond sensitively to such changes in the focus target position, and cases where it is not. In this embodiment, this is switched depending on the change amount of sensitivity per time. Various patterns are possible for determining the focus drive command value, and one example will be described below with reference to Figures 7(a) and (b).

Figures 7(a) and (b) are diagrams illustrating the relationship between the amount of change in sensitivity per time and the focus drive command value (drive speed). Figure 7(a) shows an example where the sensitivity is changing in the direction of increasing. Figure 7(b) shows an example where the sensitivity is changing in the direction of decreasing. In Figures 7(a) and (b), the horizontal axis represents the amount of change in sensitivity per time, and the vertical axis represents the focus drive command value (speed).

When the sensitivity is changing in the direction of increasing sensitivity as shown in Figure 7(a), the drive command value is determined so that the drive speed in the focus drive command value becomes (relatively) faster as the amount of change in sensitivity per time increases. On the other hand, when the sensitivity is changing in the direction of decreasing sensitivity as shown in Figure 7(b), the drive command value is determined so that the drive speed in the focus drive command value becomes (relatively) slower as the amount of change in sensitivity per time increases. The reason for determining the focus drive command value in this way is the same as that explained in Example 1 with reference to Figures 4(a) and (b).

In Figures 7(a) and (b), an example is described in which the focus drive speed is changed in accordance with the amount of change in sensitivity, but this embodiment is not limited to this, and the focus drive amount may also be changed. Also, although an example is described in which the focus drive speed is changed linearly in accordance with the amount of change in sensitivity, it may also be changed non-linearly. Alternatively, a setting means may be provided that allows the user to set the focus drive speed, and the speed may be changed relatively based on the set speed, or the slower (or faster) of the set speed and the calculated speed may be used.

In this embodiment, the drive command value (drive speed and drive amount) for the focus lens 102 during focus adjustment operation is changed according to the amount of change in sensitivity per time. In Example 1, the drive command value for the focus lens was changed according to the drive state of a specific optical element such as the zoom lens 103, but this embodiment focuses on the amount of change in sensitivity that changes according to the drive state or drive position of multiple optical elements. This makes it possible to determine the drive command value for the focus lens 102 while taking into account the drive state of optical elements other than the zoom lens 103 (for example, the position or speed of the focus lens 102). Furthermore, even when focusing only on the zoom lens 103, because the optical design has areas where the change in sensitivity per unit drive amount is large and areas where it is small, the drive command value for the focus lens 102 can be determined appropriately for each area.

As described above, in this embodiment, the focus drive command value can be determined by taking into account the magnitude of the effect of the movement of each of the multiple optical components that constitute the imaging optical system 101 on the occurrence of defocus caused by the movement of the optical components. This makes it possible to reduce defocus caused by the movement of multiple optical components.

Next, a third embodiment of the present invention will be described with reference to Figures 8 to 10. In this embodiment, a method for maintaining focus on the user's intended subject when continuous autofocus adjustment is being performed, such as with a full-time AF function, and the focus target position is detected at a distant position due to a subject other than the main subject passing by, for example. To implement this method with a simple configuration, a threshold value is set to detect changes in the subject, and if the focus target position is detected at a position distant by more than the threshold value, it is determined that a change in the subject has occurred and focus driving is not performed immediately.

In Examples 1 and 2, a method for determining a focus drive command value according to the amount of change in the zoom lens drive state or sensitivity was described. In contrast, in this example, a method for changing the threshold for detecting changes in the subject according to the amount of change in the zoom lens drive state or sensitivity is described.

Figure 8 is a flowchart showing the focus drive command generation process in this embodiment. Steps S301 to S304 in Figure 8 are the same as those in Figure 3 described in Example 1, so their description will be omitted.

After performing step S304, the process proceeds to step S805. In step S805, the drive command unit 112 calculates the zoom lens drive speed based on the history data (history information) of the position of the zoom lens 103 (positions acquired multiple times) acquired in step S302. Alternatively, the drive command unit 112 calculates the amount of change in sensitivity per unit time based on the history data (history information) of the sensitivity (sensitivity acquired multiple times) acquired in step S303. The drive command unit 112 calculates either the zoom lens drive speed or the amount of change in sensitivity per unit time, or calculates both. In the subsequent processing, similar effects can be achieved regardless of whether the zoom lens drive speed or the amount of change in sensitivity per unit time is used. This is as described in Examples 1 and 2.

Next, in step S806, the drive command unit 112 determines a threshold value to be used for detecting a change in the subject, depending on the zoom lens drive speed or the amount of change in sensitivity per time calculated in step S805. Next, in step S807, the drive command unit 112 updates the reference focus target position to be used for detecting a change in the subject. The reference focus target position is, for example, a current focus target position predicted by polynomial approximation based on historical data of multiple focus target positions that were determined to be the same subject at the previous focus target positions. Alternatively, it may simply be the most recent focus target position that was determined to be the same subject at the previous focus target positions. Furthermore, when calculating the initial focus target position, the reference focus target position is set to the currently calculated focus target position.

Next, in step S808, the drive command unit 112 compares the focus target position calculated in step S304 with the reference focus target position calculated in step S807. If the difference between the focus target position and the reference focus target position is equal to or greater than the threshold, the process proceeds to step S809. On the other hand, if the difference between the focus target position and the reference focus target position is less than the threshold, the process proceeds to step S810. Here, a process is performed to determine whether the subject is the same or a different subject (subject change determination). Details of this process will be described later with reference to FIG. 9.

In step S809, the drive command unit 112 determines whether the subject change waiting time has elapsed. If the subject change waiting time has elapsed, the process proceeds to step S810. On the other hand, if the subject change waiting time has not elapsed, the process proceeds to step S812. The subject change waiting time will be explained in step S811, which will be described later.

In step S810, the drive command unit 112 determines a drive command value (drive speed and drive amount) for the focus lens 102 based on the current focus target position calculated in step S304. The focus drive command value determined here may or may not be changed depending on the amount of change in the zoom lens drive speed or sensitivity, as in Example 1 or Example 2.

Next, in step S811, the drive command unit 112 resets the subject change waiting time and ends this flow. In this embodiment, if a predetermined waiting time has elapsed even when the subject has changed, a focus drive command is output toward the detected new subject. This allows the user to intentionally change the subject and then perform a focusing operation on the changed subject after a predetermined time has elapsed without any special operation. The waiting time set here may be changeable by the user, or may be a predetermined fixed value. Alternatively, it may be changed depending on the usage conditions, such as full-time AF or one-shot AF.

In step S812, the drive command unit 112 determines the drive command value (drive speed and drive amount) for the focus lens 102 based on the reference focus target position calculated in step S807, and then ends this flow. This process is executed when a change in the subject is detected and the specified waiting time has not yet elapsed. In other words, when the subject changes, the focus is driven toward the subject that was detected previously.

In Figure 8 above, we have explained the process flow for changing the subject change detection threshold according to the amount of change per time in zoom lens drive speed and sensitivity. The reason for taking the amount of change in zoom lens drive speed and sensitivity into consideration when determining the subject change detection threshold is that focus detection results and sensitivity can change depending on zoom lens drive and focus lens drive, which can result in a change in the focus target position. Because a change in focus target position does not occur due to subject movement, detecting it as a subject change would be a false detection. On the other hand, if the subject is truly changing, it is necessary to correctly detect the subject change. To achieve both of these, in this embodiment, the subject change detection threshold is changed according to the amount of change in zoom lens drive speed and sensitivity. There are various possible methods for determining the subject change detection threshold, and one example will be described later with reference to Figure 10.

Figures 9(a) and (b) are explanatory diagrams of a subject change detection method. In Figures 9(a) and (b), the horizontal axis represents time (elapsed time), and the vertical axis represents focus target position. The plots in the figures represent historical information about focus target positions (determined to be the same subject) at each time, and the solid lines in the figures are approximation lines of the historical information. The dashed lines in the figures indicate the range of the threshold for subject change detection at the most recent time. Furthermore, at the most recent time, the reference focus target position described with reference to Figure 8 and the current focus target position are shown side by side. In this example, we will explain the case where the reference focus target position is calculated from the approximation line of the past focus target position.

Figure 9(a) is an explanatory diagram of a pattern that is determined to be the same subject (no change in subject). Figure 9(b) is an explanatory diagram of a pattern that is determined to be a different subject (change in subject). In Figure 9(a), the difference between the reference focus target position and the current focus target position is less than the threshold, so it is determined to be the same subject (no change in subject). On the other hand, in Figure 9(b), the difference between the reference focus target position and the current focus target position is greater than the threshold, so it is determined to be a different subject (change in subject).

Figures 10(a) and (b) are explanatory diagrams of the relationship between the amount of change in zoom lens drive state or sensitivity and the method of detecting changes in a subject. The notation in the figures is the same as in Figures 9(a) and (b), so its explanation will be omitted. Figure 10(a) shows an example where the amount of change per time in zoom lens drive speed or sensitivity is small. Figure 10(b) shows an example where the amount of change per time in zoom lens drive speed or sensitivity is large.

In Figure 10(a), the threshold for detecting changes in the subject is set smaller than in Figure 10(b). When the amount of change per unit time in the zoom lens drive speed or sensitivity is small, it is expected that the change in focus detection results (change in focus target position) due to movement of the optical components will be small. Therefore, it is expected that changes in the focus target position will be relatively strongly affected by changes in subject distance, so there is a high possibility that changes in the subject will be correctly determined even if the threshold is set smaller.

On the other hand, in Figure 10(b), the threshold for detecting changes in the subject is set higher than in Figure 10(a). If the amount of change per unit time in the zoom lens drive speed or sensitivity is large, it is expected that the change in focus detection results (change in focus target position) due to movement of the optical components will be large. Therefore, even for the same subject, the calculated focus target position may change, so a larger threshold is required.

Here, we have explained an example in which the threshold is changed depending on the magnitude of the change in zoom lens drive speed or sensitivity per time, but the threshold may also be changed depending on the drive direction of the zoom lens or the direction of change in sensitivity. The threshold may be changed linearly or discretely depending on the change in zoom lens drive speed or sensitivity. The magnitude of the threshold may also be changed depending on the user's settings or the usage status of functions such as full-time AF or one-shot AF, or it may be changed relatively from that value.

In this embodiment, the threshold for detecting changes in subject movement is changed according to the amount of change per unit time in the drive state or sensitivity of the zoom lens. This prevents the subject from being erroneously determined to have changed due to changes in focus detection results caused by movement of optical components such as the zoom lens or focus lens. This embodiment is particularly effective when the system has a function that prevents the focus lens from immediately adjusting focus when a change in subject is detected.

As described above, in each embodiment, the control device (drive command unit 112) has an acquisition unit 112a and a generation unit 112b. The acquisition unit acquires the defocus amount of the imaging optical system 101, which includes the focus lens unit (focus lens 102). The generation unit generates a drive command for the focus lens unit based on the defocus amount. The generation unit also generates a drive command based on information regarding the amount of change in the object distance of the imaging optical system relative to the amount of movement of the focus lens unit.

Preferably, the generation unit acquires information regarding at least one of the drive speed, drive direction, or position of an optical element in the imaging optical system as information regarding the amount of change in the object distance of the imaging optical system relative to the amount of movement of the focus lens unit. More preferably, the optical element includes at least one of a zoom lens unit and an aperture stop. Also preferably, the generation unit generates a drive command based on information regarding the amount of change per unit time in the amount of change in the object distance of the imaging optical system relative to the amount of movement of the focus lens unit.

Preferably, the generation unit generates at least one of a target drive speed or a target drive amount for the focus lens unit as the drive command. More preferably, the generation unit does not drive the focus lens unit when the target drive amount exceeds a threshold. More preferably, the generation unit drives the focus lens unit when the target drive amount continues to exceed the threshold for a specific period of time. More preferably, the generation unit sets the threshold based on information regarding the amount of change in object distance of the imaging optical system relative to the amount of movement of the focus lens unit. More preferably, the generation unit sets the threshold so that it is larger when the zoom lens unit in the imaging optical system moves from the wide-angle side to the telephoto side than when the zoom lens unit moves from the telephoto side to the wide-angle side.

Preferably, the generation unit sets the threshold value based on information regarding the amount of change in the object distance of the imaging optical system per unit movement amount of the focus lens unit. More preferably, the generation unit sets the threshold value to a larger value the greater the amount of change in the object distance of the imaging optical system per unit movement amount of the focus lens unit.

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

Each embodiment can provide a control device, lens device, imaging device, control method, and program that reduces the amount of defocus caused by movement of the imaging optical system and is advantageous in terms of automatic focusing on the subject intended by the user.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments and various modifications and variations are possible within the scope of the invention.

For example, Figure 11 is a block diagram of an image capture device 10a as a modified example of each embodiment. The image capture device 10a has a camera body 200a and a lens device 100a that is detachable from the camera body 200a. The image capture device 10a differs from the image capture device 10 in that the spectral prism 105, focus detection unit 108, and defocus calculation unit 109 are provided in the camera body 200a, whereas the image capture device 10 has these units provided in the lens device 100. In this way, functions related to focus detection may be provided in the camera body 200a or in another information processing device such as a PC.

In addition, in each embodiment, instead of providing a focus detection unit 108, the defocus amount may be calculated by performing focus detection using a phase difference detection method (image plane phase difference AF) using the image signal output from the image sensor 107.

112 Drive command unit (control device)
112a acquisition unit 112b generation unit

Claims (15)

an acquisition unit that acquires a defocus amount of an imaging optical system including a focus lens unit;
a generation unit that generates a drive command for the focus lens unit based on the defocus amount,
The control device, wherein the generation unit generates the drive command based on information regarding a change per unit time in an object distance of the imaging optical system relative to a movement amount of the focus lens unit. The control device described in claim 1, characterized in that the generation unit acquires information regarding at least one of the drive speed, drive direction, and position of an optical element in the imaging optical system as information regarding the amount of change in object distance of the imaging optical system relative to the amount of movement of the focus lens unit. The control device described in claim 2, characterized in that the optical element includes at least one of a zoom lens unit and an aperture diaphragm. 4. The control device according to claim 1 , wherein the generating unit generates at least one of a target drive speed and a target drive amount of the focus lens unit as the drive command. The control device according to claim 4, characterized in that the generation unit sets a threshold value based on information regarding a change in object distance of the imaging optical system relative to a movement amount of the focus lens unit, and if the target drive amount exceeds the threshold value, the control unit does not drive the focus lens unit. an acquisition unit that acquires a defocus amount of an imaging optical system including a focus lens unit;
a generation unit that generates at least one of a target drive speed or a target drive amount as a drive command for the focus lens unit based on the defocus amount,
The control device is characterized in that the generation unit generates the drive command and sets a threshold value based on information regarding the amount of change in object distance of the imaging optical system relative to the amount of movement of the focus lens unit, and does not drive the focus lens unit if the target drive amount exceeds the threshold value. The control device according to claim 4, characterized in that the generation unit sets a threshold value based on information regarding the amount of change in object distance of the imaging optical system per unit movement amount of the focus lens unit, and does not drive the focus lens unit if the target drive amount exceeds the threshold value. an acquisition unit that acquires a defocus amount of an imaging optical system including a focus lens unit;
a generation unit that generates at least one of a target drive speed or a target drive amount as a drive command for the focus lens unit based on the defocus amount,
The generation unit
generating the drive command based on information regarding a change in object distance of the imaging optical system relative to a movement amount of the focus lens unit;
setting a threshold value based on information regarding a change in object distance of the imaging optical system per unit movement amount of the focus lens unit;
A control device that prevents the focus lens unit from being driven when the target drive amount exceeds the threshold value. 9. The control device according to claim 5 , wherein the generation unit generates the drive command to drive the focus lens unit when the target drive amount exceeds the threshold value for a specific period of time. The control device according to any one of claims 5 to 9, characterized in that the generation unit sets the threshold value so that it is larger when the zoom lens unit in the imaging optical system moves from the wide-angle side to the telephoto side than when the zoom lens unit moves from the telephoto side to the wide- angle side . 11. The control device according to claim 5 , wherein the generation unit sets the threshold to a larger value as the amount of change in the object distance of the imaging optical system per unit movement amount of the focus lens unit increases. A lens device comprising the control device according to any one of claims 1 to 11 and an imaging optical system. An imaging device comprising the lens device described in claim 12 and an imaging element that captures an image formed by the lens device. an acquisition step of acquiring a defocus amount of an imaging optical system including a focus lens unit;
a generating step of generating a drive command for the focus lens unit based on the defocus amount,
A control method characterized in that the generating step generates the drive command based on information regarding a change per unit time in an object distance of the imaging optical system relative to a movement amount of the focus lens unit. A program causing a computer to execute the control method described in claim 14.