Control apparatus, lens apparatus, control method, and storage medium

A control apparatus for a lens apparatus to be detachably attached to an image pickup apparatus and including first and second focus lenses that are independently movable during focusing includes an acquisition unit for acquiring optical data that include information on a focus sensitivity of the first focus lens, and information on a focus sensitivity of the second focus lens, and a calculation unit for calculating a moving speed of the first focus lens using a target image plane speed acquired from the image pickup apparatus, target positions of the first and second focus lenses, current positions of the first and second focus lenses, and the optical data, and to calculate a moving speed of the second focus lens using the target positions of the first and second focus lenses, and the current positions of the first and second focus lenses.

BACKGROUND

Technical Field

The disclosure relates to a control apparatus for controlling a lens apparatus to be attached to an image pickup apparatus.

Description of the Related Art

There has conventionally been known a lens apparatus that includes a main lens unit for providing focusing and an auxiliary lens unit for correcting aberrations in order to reduce the shortest imaging distance. Japanese Patent Laid-Open No. 2021-67802 discloses a configuration that moves the main lens unit and the auxiliary lens within certain error ranges by correcting a driving trajectory of the auxiliary lens unit based on data representing a relationship among positions of the main lens unit and the auxiliary lens unit, their focal lengths, and an object distance. Japanese Patent No. 5688545 discloses a configuration that makes an actuator move at a constant speed until an in-focus position is determined in order to suppress driving noise of the actuator.

However, the configuration disclosed in Japanese Patent Laid-Open No. 2021-67802 needs to retain a large amount of data and to perform frequent communications. In addition, since the actuator is frequently operated, driving noise of the actuator becomes louder.

The configuration disclosed in Japanese Patent No. 5688545 premises contrast autofocus (AF), and accords the position of the main lens unit and the position of the auxiliary lens unit with each other near the in-focus position. However, phase difference AF performs focus detection even during search driving, and thus if a positional shift between the main lens unit and the auxiliary lens unit increases, an error in the focus detecting accuracy may occur due to the aberrational influence. In addition, if the positional shift between the main lens unit and the auxiliary lens unit increases, the image quality during recording of a moving image deteriorates due to the aberrational influence.

SUMMARY

The disclosure provides a control apparatus that can reduce a positional shift between two focus lenses while suppressing driving noise during driving of each focus lens.

A control apparatus according to one aspect of the disclosure is configured to control a lens apparatus that is attachable to and detachable from an image pickup apparatus and includes a first focus lens and a second focus lens that are independently movable during focusing. The control apparatus includes at least one processor, and a memory coupled to the at least one processor, the memory having instructions that, when executed by the processor, performs operations as an acquisition unit configured to acquire optical data that include information on a focus sensitivity of the first focus lens, and information on a focus sensitivity of the second focus lens, and a calculation unit configured to calculate a moving speed of the first focus lens using a target image plane speed acquired from the image pickup apparatus, target positions of the first focus lens and the second focus lens, current positions of the first focus lens and the second focus lens, and the optical data, and to calculate a moving speed of the second focus lens using the target positions of the first focus lens and the second focus lens, and the current positions of the first focus lens and the second focus lens.

A lens apparatus that includes the above control apparatus also constitutes another aspect of the disclosure. A control method corresponding to the control apparatus and a storage medium storing a program that causes a computer of a lens apparatus to execute the above control method also constitute another aspect of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

Referring now to the accompanying drawings, a detailed description will be given of embodiments according to the disclosure. Corresponding elements in respective figures will be designated by the same reference numerals, and a duplicate description thereof will be omitted.

First Embodiment

FIG.1Aschematically illustrates a camera system according to this embodiment. The camera system includes a lens apparatus100and a camera body (image pickup apparatus)200to which the lens apparatus100is to be detachably attached. The lens apparatus100and the camera body200are mechanically and electrically connectable to each other via an unillustrated mount, and power supply and mutual communication between the lens apparatus100and the camera body200are performed via terminals provided on the mount.

The lens apparatus100includes an optical system101, a lens control unit (control apparatus)106, a stop driving unit107, a first focus driving unit108, a second focus driving unit109, and a memory110. The optical system101forms an optical image of an object on an image sensor201in the camera body200. The optical system101includes an aperture stop (diaphragm)103, a first focus lens104, and a second focus lens105. The aperture stop103includes unillustrated stop blades, and the stop blades are moved by the stop driving unit107via an actuator to adjust a light amount. The first focus lens104is moved in an optical axis direction by the first focus driving unit108via an actuator to adjust an in-focus state and aberrations. The second focus lens105is moved in the optical axis direction by the second focus driving unit109via an actuator to adjust the in-focus state and aberrations. The first focus lens104and the second focus lens105are independently movable during focusing. In this embodiment, each of the first focus driving unit108and the second focus driving unit109includes a stepping motor as the actuator and a gear transmission mechanism that transmits a rotation of the stepping motor to each focus lens. The position of each focus lens may be feedback-controlled by using a detection signal from a position detecting unit by which the lens control unit106detects the position of each focus lens.

The lens control unit106includes a computer (control apparatus) equipped with a Central Processing Unit (CPU), and includes an acquisition unit106aand a calculation unit106bas illustrated inFIG.1B. The lens control unit106transmits a driving command value to each of the stop driving unit107, the first focus driving unit108, and the second focus driving unit109so as to control driving of the aperture stop103, the first focus lens104, and the second focus lens105.

The memory110includes a ROM, a RAM, or the like, and stores information (optical data) necessary to drive the aperture stop103, the first focus lens104, and the second focus lens105.FIG.2illustrates a focus sensitivity table that includes information on the first focus lens and the focus sensitivity of the first focus lens and information on the second focus lens and the focus sensitivity of the second focus lens, which are included in the optical data. More specifically, the information on the first focus lens104and the focus sensitivity of the first focus lens104includes information on the plurality of (first) zones according to the position of the first focus lens104and the focus sensitivity of the first focus lens104for each of the plurality of (first) zones. The information on the second focus lens105and the focus sensitivity of the second focus lens105includes information on a plurality of (second) zones according to the second focus lens105and the focus sensitivity of the second focus lens105for each of the plurality of (second) zones. The plurality of (first) zones according to the position of the first focus lens104and the plurality of (second) zones according to the position of the second focus lens105correspond to each other. The focus sensitivity table also includes a boundary position of each focus lens, which is a zone dividing position. The focus sensitivity is a moving amount of a focus position (image plane position) relative to a moving amount of each focus lens.

The camera body200includes the image sensor201, a signal processing unit202, a recording processing unit203, a defocus detecting unit204, a camera control unit205, a memory206, an electronic viewfinder207, and a display unit208. The image sensor201receives light from the optical system101, generates an electric signal by photoelectric conversion, and transmits a generated electric signal to the signal processing unit202. The image sensor201includes unillustrated focus detecting pixels in addition to imaging pixels. The signal processing unit202converts the electric signal from the image sensor201into a digital signal. The signal processing unit202performs various image processing such as noise removal and color correction for the digital signal, and transmits image data to the recording processing unit203. The recording processing unit203displays the input image data on the electronic viewfinder207and the display unit208. The defocus detecting unit204determines a defocus amount based on a phase difference between signals of the pair of object images acquired by the light incident on the focus detecting pixel in the image sensor201via a microlens that divides the pupil, and outputs the determined defocus amount to the camera control unit205. The camera control unit205includes a CPU and is electrically connected to the recording processing unit203, the defocus detecting unit204, and the memory206. The camera control unit205reads and executes a program recorded in the memory206, and communicates information necessary for AF control to the lens control unit106. The camera control unit205controls the camera body200in response to an input from a camera operation unit such as an unillustrated imaging switch or various setting switches.

FIGS.3A and3Billustrate a relationship between an object distance and a position of each focus lens in this embodiment. This embodiment sets five zones. This embodiment sets the number of zones to 5, but the number of zones is not limited to this example. In this embodiment, the moving speed of each focus lens is calculated by using the focus sensitivity, and thus steeply changes if a difference in the focus sensitivity between adjacent zones is large. Therefore, the number of zones may be set so as to reduce the focus sensitivity difference.

A description will now be given of the operation of the lens control unit106in a case where a command to move each focus lens is transmitted from the camera body200to the lens apparatus100. A description will now be given of a case where the lens control unit106receives a command to move the first focus lens104and the second focus lens105from close (short-distance) positions Pm6and Ps6inFIG.3Ato infinity positions Pm1and Ps1, respectively. Now assume that this command includes information on a target image plane speed V [mm/sec].

Upon receiving the command from the camera body200, the lens control unit106first calculates the moving amounts of the first focus lens104and the second focus lens105. The moving amounts of the first focus lens104and the second focus lens105are calculated as Pm1-Pm6and Ps1-Ps6, respectively. This embodiment sets the boundary position defined in the focus sensitivity table to the moving start position and the target position of the focus lens for simpler explanation, but may start moving the focus lens from a position in the zone as illustrated by a white dot inFIG.3B.

Next, the lens control unit106calculates the moving speed of each focus lens. As illustrated inFIGS.3A and3B, since the zone corresponds to the object distance, the first focus lens104and the second focus lens105belong to the same zone in principle. In a case where one of the first focus lens104and the second focus lens105is located at the boundary position, the other is also located at the boundary position of the same zone so as to secure the synchronism of the two focus lenses. For example, in a case where the first focus lens104is moved from the close position Pm6to a position Pm5, it is necessary to move the second focus lens105from the close position Ps6, which is the boundary position of the same zone, to a position Ps5in the same time period. An image plane moving amount caused by the movement of the first focus lens104in Zone5is calculated as Sm5(Pm5-Pm6) based on the focus sensitivity Sm5of the first focus lens104and the moving amount of the first focus lens104. Similarly, an image plane moving amount caused by the movement of the second focus lens105in Zone5is calculated as Ss5(Ps5-Ps6). Hence, an image plane moving amount x caused by the movements of the first focus lens104and the second focus lens105in Zone5is expressed by the following expression (1):
x=Sm5(Pm5−Pm6)+Ss5(Ps5−Ps6)  (1)

The expression (1) is expressed by the following expression (2) when the expression (1) is deformed based on the moving amount of the first focus lens104.

Underlined part of the expression (2) is expressed only by the variables defined by the focus sensitivity table, and means that the image plane moving amount can be calculated in which the moving amount of the second focus lens105is considered when the first focus lens104is moved. When the relationship of the expression (2) is considered, the target image plane speed V acquired from the camera body200is expressed by the following expression (3), where Vmis a moving speed of the first focus lens104.

The moving speed Vmof the first focus lens104can be calculated based on the expression (3). While this embodiment premises that each focus lens is moved in Zone5, the moving speed of the first focus lens104can be calculated in another zone according to the focus sensitivity and the boundary position of that zone.

After the moving speed of the first focus lens104is calculated, the lens control unit106calculates the moving speed Vsof the second focus lens105using the following expression (4) based on a moving amount ratio between these focus lenses.

The lens control unit106monitors the current position of each focus lens until each focus lens reaches the target position, and updates the moving speed of each focus lens when the zone is changed.

FIG.4is a flowchart illustrating processing by the lens control unit106in a case where the lens control unit106receives a command to move each focus lens from the camera body200in this embodiment.

In step S401, the lens control unit106calculates the moving amounts of the first focus lens104and the second focus lens105in response to the command from the camera body200.

In step S402, the lens control unit106(calculation unit106b) calculates the moving speed of each focus lens using the expressions (3) and (4). It is assumed that the acquisition unit106ahas acquired the optical data from the memory110before calculating the moving speed. Strictly speaking, an acceleration time is required to accelerate the stepping motor of each focus driving unit to a predetermined speed. For example, in a case where the acceleration of the second focus lens105is smaller than that of the first focus lens104, it is conceivable that the second focus lens105is moved later than the first focus lens104. In this case, it is considered that each focus lens is moved by constant speed motion and constant acceleration motion, and a delay caused by the difference in acceleration is calculated, and the speed of the second focus lens105may be corrected to be higher so that the delay can be eliminated at the boundary position of the zone. In a case where a ratio of the acceleration time to the moving time of the second focus lens105is large, the above delay cannot be reduced even if the speed of the second focus lens105is corrected to be higher. In that case, the speed of the first focus lens104may be corrected to be lower. The first focus lens104and the second focus lens105start moving at the moving speed calculated in this step.

In step S403, the lens control unit106determines whether to update the moving speed of each focus lens. If it is determined that the moving speed is to be updated, the flow returns to step S502, and otherwise, the flow proceeds to step S504.

As described above, the focus sensitivity changes according to the zone. Therefore, in a case where each focus lens is moved to a different zone, it is necessary to change its moving speed at a timing when it is moved to the different zone, that is, at a timing when the focus lens crosses the boundary position. The case where it is determined that the moving speed is to be updated in step S403is a case where it is determined that at least one of the two focus lenses crosses the boundary position. In a case where two focus lenses cross the boundary positions at almost the same time, the lens control unit106may calculate the moving speed of each focus lens using the expressions (3) and (4). However, as described above, the synchronism of the two focus lenses may not be secured depending on the acceleration condition of each focus lens and the like. The lens control unit106corrects the moving speed of at least one of the two focus lenses even if the synchronism of the two focus lenses is not secured when that focus lens crosses the boundary position. For example, in a case where an error (delay or distance on an optical axis) Δp between the position of the second focus lens105and a boundary position Po (which is a position of the second focus lens105corresponding to the boundary position Pm4) when the first focus lens104crosses (or is moved to) a boundary position Pm4(predetermined position), the lens control unit106can correct the moving speed using the following expression (5):

By making higher the moving speed of the second focus lens105using the expression (5), the error between the positions of the two focus lenses in Zone4can be reduced. On the other hand, in a case where the second focus lens105crosses the boundary position before the first focus lens104, the sign of the error Δp in the expression (5) may be reversed.

FIG.5is a configuration diagram of the second focus driving unit109according to this embodiment. In this embodiment, the second focus lens105is moved by a rotation of a cam ring26relative to the stepping motor20via the transmission mechanism using the gears21,22,23,24, and25.

FIGS.6A and6Bexplain the backlash (idleness) of the gears and illustrate the engagement state of the gears23and24.FIG.6Aillustrates the engagement state of the gears23and24in a case where the gear23is rotated in a clockwise (CW) direction. InFIG.6A, the gears23and24transmit the force via a contact point262.FIG.6Billustrates the engagement state of the gears23and24in a case where the gear23changes the rotation direction from the CW direction to a counterclockwise (CCW) direction (where the moving direction of the second focus lens105is reversed from the infinity direction to the close direction). There is a gap242in the transmission mechanism using the gears. Therefore, even if the stepping motor20operates and the gear23is rotated in the CCW direction, the second focus lens105is not moved until the gap242is filled and the gears23and24come into contact with each other. Accordingly, this embodiment corrects the moving amount of the second focus lens105is corrected so as to additionally operate the stepping motor20on the premise that the second focus lens105is not moved due to the gap242.

The gaps formed in the first focus driving unit108and the second focus driving unit109are not always the same. The first focus driving unit108and the second focus driving unit109may have different structures. Even in that case, the moving speed of the second focus lens105may be calculated by inputting a correction amount based on the gap formed in each focus driving unit into the error Δp in the expression (5). Thereby, a positional shift between the first focus lens104and the second focus lens105can be reduced.

In step S504, the lens control unit106determines whether or not each focus lens has reached the target position. If it is determined that each focus lens has reached the target position, this flow ends (movement of each focus lens is stopped), and if it is determined that each focus lens has not yet reached the target position, the flow returns to step S503.

As described above, the configuration according to this embodiment can suppress noise generation by reducing the changing times of the moving speeds of the first focus lens104and the second focus lens105. In addition, this embodiment simultaneously sets the moving speeds of the first focus lens104and the second focus lens105, and thereby secures the synchronism of the two focus lenses.

Second Embodiment

FIG.7schematically illustrates a camera system according to this embodiment. This embodiment will discuss a configuration different from that of the camera system of the first embodiment, and a detailed description of the same configuration will be omitted.

In addition to the configuration of the first embodiment, the lens apparatus100includes a magnification varying lens102, a zoom operation unit111, and a zoom position detecting unit112. The magnification varying lens102changes a focal length of the lens apparatus100. The zoom operation unit111may manually move the magnification varying lens102, for example, like a zoom ring, or may electrically move the magnification varying lens102using an actuator. The zoom position detecting unit112detects the position of the magnification varying lens102and transmits the position of the magnification varying lens102to the lens control unit106.

FIG.8illustrates a relationship between the object distance and the position of the focus lens for each zoom state (focal length) in the second embodiment.FIG.8illustrates a relationship between five zoom states from Zoom 0 to Zoom 4, but the number of zoom states is not limited to this example. Since the positions of the first focus lens104and the second focus lens105change depending on the zoom state, it is necessary to prepare a focus sensitivity table according to the zoom state.

FIG.9illustrates a focus sensitivity table according to this embodiment. If the zoom state is a zoom state defined in the focus sensitivity table, the moving speed of each focus lens can be easily calculated by the same method as that of the first embodiment, but as illustrated inFIG.10, the zoom state may be a zoom state between Zoom 0 and Zoom 1. In that case, the moving speed of each focus lens can be calculated using the same method as that of the first embodiment by data interpolation of the focus sensitivity table, which is linear interpolation or the like using information on the focus sensitivity table of Zoom 0 and Zoom 1. For example, when the first focus lens104is located at a position Pms, a position Pmethat satisfies a relationship of Pm12−Pms: Pms−Pm02=Pm13−Pme: Pme-Pm03can be calculated as the boundary position.

In the lens apparatus100according to this embodiment, each focus lens is electrically moved according to the operation of the zoom operation unit111. This embodiment can determine the moving conditions of the first focus lens104and the second focus lens105according to the position of the magnification varying lens102detected by the zoom position detecting unit112. For example, in a case where the zoom state changes from a state of Zoom 0 to a state of Zoom 1 when the first focus lens104is located at a position Pm02, the first focus lens104may be moved to a position Pm12. The second focus lens105may be moved from a position Ps02to a position Ps12.

Once the moving amount and the moving speed of the first focus lens104are determined according to a state in which the zoom operation unit111is operated, the moving amount and the moving speed of the second focus lens105are determined by using a moving amount ratio between the focus lenses. For example, in a case where a quick zoom operation is made, it is necessary to quickly move each focus lens in order to suppress defocus.

As described above, the configuration according to this embodiment can provide the same effect as that of the first embodiment, even if the lens apparatus100is a zoom lens.

Each embodiment can provide a control apparatus that can reduce a positional shift between two focus lenses while suppressing driving noise during driving of each focus lens.

OTHER EMBODIMENTS

This application claims the benefit of Japanese Patent Application No. 2021-158147, filed on Sep. 28, 2021, which is hereby incorporated by reference herein in its entirety.