The present disclosure relates to a lens apparatus and an imaging apparatus.
There is a configuration in which a lens barrel is held in a groove portion formed in a cam ring or a fixed barrel by a roller, and there is known a structure in which the lens barrel is biased by a biasing member, such as a spring, in order to control a positional shift of the lens barrel due to backlash between the groove portion and the roller. An engagement portion between the roller and the groove portion or the like can have a clearance in consideration of the tolerance of components. There is known a configuration in which a lens barrel held by a roller contains a different lens barrel, and the lens barrel on the inner side is hung from the lens barrel on the outer side using a roller.
Japanese Patent No. 6759281 discusses a configuration of a lens apparatus that uses a biasing member in order to eliminate backlash that a cam follower engaged in a straight groove and a cam groove has with respect to a groove portion.
However, in the lens apparatus discussed in Japanese Patent No. 6759281, in a case where a lens barrel located inside a lens barrel held by the cam follower needs to be hung using a roller, and backlash needs to be controlled, two sets of biasing members are necessary, which increases the size. The two sets of biasing members are necessary in order to control two types of backlash, specifically, the backlash of the cam follower with respect to the straight groove and the cam groove, and the backlash of the roller with respect to a base barrel.
According to an aspect of the present disclosure, a lens apparatus includes a lens holding member configured to hold a lens, a first movement member configured to hold the lens holding member and to move in an optical-axis direction together with the lens holding member, a guide member having a straight groove, and a cam member having a cam groove and configured to rotate with respect to the guide member, wherein the first movement member includes a cam follower configured to engage with the straight groove and the cam groove, and moves in the optical-axis direction by relative rotation of the cam member to the guide member, a second movement member configured to move in the optical-axis direction together with the lens holding member and the first movement member, and a biasing member configured to bias the lens holding member to the second movement member so that the cam follower is biased to the straight groove and the cam groove.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In the drawings, similar members are denoted by the same reference numerals, and the description thereof will not be repeated.
Exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. A configuration of an interchangeable lens 100 (an interchangeable lens for a single lens camera) that is a lens apparatus according to each exemplary embodiment of the present disclosure will be described with reference to
The interchangeable lens 100 of the present exemplary embodiment is a lens apparatus having a six-unit configuration consisting of a first lens unit L1 to a sixth lens unit L6. A focus lens unit that is the fourth lens unit L4 and a floating lens unit that is the fifth lens unit L5 are moved in an optical-axis direction by a focusing operation (in-focus operation) on the interchangeable lens 100. The second lens unit L2 in the optical-axis direction is moved along each predetermined course by a zooming operation (zoom/magnification operation) on the interchangeable lens 100.
In this process, a controller 122 serving as control means controls drive of the fourth lens unit L4 and the fifth lens unit L5 to maintain a focus position after a change through the zooming operation and maintain each aberration at a certain level or lower.
A camera body 400 illustrated in
A lens mount 111 has a bayonet portion for attachment to the camera body 400, and is fixed to an exterior ring 113 by a screw. The exterior ring 113 is fixed to a fixed barrel 112 by a screw. A zoom index and operation switches (not illustrated) are attached to the exterior ring 113.
A guide barrel 250 (a guide member) is fixed to the fixed barrel 112 by a screw. A straight groove for guiding each lens unit in a straight direction is formed in the guide barrel 250. A cam groove corresponding to the course of the second lens unit L2 in the zooming operation is formed in a cam barrel 260 (a cam member) rotatable at a fixed position with respect to the guide barrel 250.
A zoom operation barrel 119 is held by diameter fitting to the guide barrel 250, in a manner rotatable about the optical axis by a fixed-position rotation roller (not illustrated).
The zoom operation barrel 119 includes a zoom key (not illustrated) and a zoom sensor key 180 (see
By the action of the cam groove in the cam barrel 260, the cam follower of a second lens holding base 200 (a first movement member), and the straight groove in the guide barrel 250, the rotational force of the zoom operation barrel 119 is converted into a straight movement of the second lens holding base 200. Thus, a basic configuration in which the second lens holding base 200 is moved straight by the zooming operation is achieved.
Next, each lens unit of the lens apparatus will be described. A first lens holding frame 101 holds the first lens unit L1. The first lens holding frame 101 is fixed to the guide barrel 250 by a screw. A lens press ring 120 has threads in the outer surface, and has a role in fixing the first lens unit L1 by being fixed through threaded engagement between the screw and threads provided on the inner surface of the first lens holding frame 101.
A protection ring is fixed to the first lens holding frame 101 by a screw (not illustrated). A concave portion for hood attachment is provided on the outer periphery side of the protection ring, and screws are provided on the inner periphery side thereof, so that accessories, such as a hood, a cap, and a filter, are attachable.
A second lens holding frame 300 holds the second lens unit L2 (a lens). As described above, the rotation of the zoom operation barrel 119 and the cam barrel 260 is converted into the straight movement of the second lens holding frame 300, and the second lens holding frame 300 is moved straight by the zooming operation, so that the focal length of the interchangeable lens 100 can be changed.
A third lens A holding frame 103A holds the third lens unit L3A. The third lens A holding frame 103A is fixed with respect to the guide barrel 250 by a screw. A diaphragm unit 110 including a diaphragm drive unit and a diaphragm blade unit is held thereby.
A third lens B holding frame 103B holds the third lens unit L3B. The third lens B holding frame 103B is held with respect to the guide barrel 250 by a roller (not illustrated).
A third lens C holding frame 103C holds the third lens unit L3C. The third lens C holding frame 103C forms a part of a vibration correction unit 108.
The vibration correction unit 108 holds the third lens C holding frame 103C in a direction orthogonal to the optical axis (an optical axis orthogonal direction), and performs vibration correction by driving the third lens C holding frame 103C, using a vibration correction drive unit including a magnet and a coil. The vibration correction unit 108 is held by being hung from the fixed barrel 112 by a roller.
A third lens D holding frame 103D holds the third lens unit L3D. The third lens D holding frame 103D is fixed with respect to a rear unit base (not illustrated) serving as a base member by a screw.
A fourth lens holding frame 104 serving as a movable lens barrel holds the fourth lens unit L4 that is the focus lens unit. The fourth lens holding frame 104 is guided to move straight by a main guide bar and a sub guide bar serving as guide members. The fourth lens holding frame 104 is driven in the optical-axis direction with respect to the rear unit base by a drive (a drive unit).
Here, a driving force transmission mechanism includes a stator and a mover that form a motor, and a motor drive transmission portion that is a part of the mover. The driving force transmission mechanism further includes a rack mechanism which is a drive transmission member for transmitting a driving force from the motor drive transmission portion to the fourth lens holding frame 104, and a rack biasing spring that removes backlash of the rack mechanism and the motor drive transmission portion by biasing.
The fourth lens holding frame 104 serving as the movable lens barrel includes a scale for position detection in the optical-axis direction. An optical sensor corresponding to the scale is disposed at the rear unit base with a flexible printed circuit board (FPC) interposed therebetween. The scale and the optical sensor form a focus position detector.
A fifth lens holding frame 105 serving as a movable lens barrel holds the fifth lens unit L5 which is a floating unit. The fifth lens holding frame 105 is guided to move straight by a main guide bar and a sub guide bar which serve as guide members. The fifth lens holding frame 105 is driven in the optical-axis direction with respect to the rear unit base by a drive means (a drive unit).
Here, a driving force transmission mechanism is configured in a manner similar to the driving force transmission mechanism for driving the fourth lens holding frame 104 holding the fourth lens unit L4.
A sixth lens holding frame 106 holds the sixth lens unit L6. The sixth lens holding frame 106 is fixed with respect to the rear unit base by a screw.
In the present exemplary embodiment, a motor using a piezoelectric element is used in driving the fourth lens holding frame 104 and the fifth lens holding frame 105, and the mover is configured to be driven in the optical-axis direction with respect to the stator. However, the drive means is not limited to the motor using the piezoelectric element. For example, a stepping motor may be used as a drive mechanism, and a mechanism of connection to a rack by having a lead screw shaft and a screw thereof serving as the mover and the motor drive transmission portion may be adopted. In using the stepping motor, a detection system can be eliminated, and the stepping motor can be controlled as open driving.
The cam barrel 260 is provided with the zoom sensor key 180 fitting to a mover of a resistance type linear sensor (a potentiometer) which is a zoom position detector (not illustrated) fixed to the guide barrel 250, and the output of the resistance type linear sensor changes depending on the amount of rotation of the cam barrel 260. The cam barrel 260 rotates in conjunction with the rotation of the zoom operation barrel 119, so that zoom position information can be detected.
A focus operation barrel 114 is held to be rotatable at a fixed position on the outside of an intermediate exterior ring 115. The focus operation barrel 114 detects the amount and direction of rotation of the focus operation barrel 114, using a light detection element in the guide barrel 250, and a scale on the inner surface of the focus operation barrel 114. For example, monochrome light and dark are used for the scale on the inner surface of the focus operation barrel 114.
A multipurpose operation barrel 121 is held by a front exterior barrel 116 to be rotatable at a fixed position on the outside of the first lens holding frame 101. The multipurpose operation barrel 121 has a plurality of comb teeth.
A photo-interrupter in the first lens holding frame 101 detects the plurality of comb teeth, so that the amount and direction of rotation of the multipurpose operation barrel 121 with respect to the first lens holding frame 101 can be detected.
The controller 122 is responsible for control of the entire interchangeable lens 100 including focus drive control, the diaphragm unit 110, the vibration correction unit 108, and other units, and is fixed to the rear unit base by a screw.
Next, a configuration related to the present exemplary embodiment will be described with reference to
A first cam follower 220 is attached to the second lens holding base 200. The first cam follower 220 engages with a guide groove 251 (a straight groove) formed in the guide barrel 250 and a cam groove 261 formed in the cam barrel 260. The first cam follower 220 (the second lens holding base 200) is guided to move straight in the optical-axis direction by the guide groove 251, and can move back and forth in the optical-axis direction by the rotation of the cam barrel 260 relative to the guide barrel 250.
A second cam follower 221 is attached to a biasing barrel 210 (a second movement member). The second cam follower 221 engages with the guide groove 251 formed in the guide barrel 250 and the cam groove 261 formed in the cam barrel 260. The rotation of the guide barrel 250 about the optical axis with respect to the second lens holding base 200 is limited. As illustrated in
The configuration in which the cam barrel 260 is disposed inward from the guide barrel 250 as in the present exemplary embodiment facilitates arrangement of components, such as a sensor and an FPC arranged outward from the guide barrel 250. On the other hand, the peripheral groove 252 for allowing the zoom sensor key 180 for connecting the cam barrel 260 and the zoom operation barrel 119 to run therethrough is to be provided on the guide barrel 250. The guide groove 251 and the peripheral groove 252 cannot overlap. Thus, if the number of the guide grooves 251 is increased, the rotation angle of the zooming operation is limited. It is therefore desirable that the first cam follower 220 and the second cam follower 221 be disposed in the same phase to share the guide groove 251 as in the present exemplary embodiment.
The second lens holding base 200 and the biasing barrel 210 are biased by a biasing member 240 to be described below, so that forces for causing the second lens holding base 200 and the biasing barrel 210 to move away from each other in the optical-axis direction are generated. The second lens holding base 200 has a hook portion 204, and the biasing barrel 210 has a hook portion 212. These hook portions 204 and 212 abut on each other, so that a force for biasing in the optical-axis direction is receivable, thus enabling unitization before components, such as the second lens holding base 200, are incorporated into the guide barrel 250 and the cam barrel 260. Thus, ease of assembly improves. The hook portion 204 and the hook portion 212 are configured not to be in contact with each other when incorporated into the cam barrel 260 and the guide barrel 250.
Accordingly, the second lens holding base 200 moves along a subject-side wall surface 264 of the cam groove 261, and the biasing barrel 210 moves along an image-plane-side wall surface 263 of the cam groove 261.
Next, connection between the second lens holding base 200 and the second lens holding frame 300 of the present exemplary embodiment will be described with reference to
The second lens holding frame 300 is held on the second lens holding base 200 by the roller 230, as illustrated in
The second fitting portion 232 and the third fitting portion 233 of the roller 230 illustrated in
A sub roller 270 (see
Next, the biasing member in the present exemplary embodiment will be described with reference to
A nut back abutment surface 304 is formed on the second lens holding frame 300 as illustrated in
In this way, the second lens holding frame 300 is biased by the biasing member 240 to the subject side, so that the roller 230 abuts the second groove 202 formed in the second lens holding base 200 on the subject side. The second lens holding base 200 is biased to the object side along the optical axis by this biasing force. The first cam follower 220 in the second lens holding base 200 abuts the subject-side wall surface 264 of the cam groove 261. The first cam follower 220 has backlash with respect to the cam groove 261, but the backlash in a direction along the optical axis of the second lens holding base 200 is controlled by this biasing force.
In this manner, the biasing member 240 which generates the biasing force in the direction along the optical axis enables the control of both the backlash of the second lens holding frame 300 with respect to the second lens holding base 200 and the backlash of the second lens holding base 200 with respect to the guide groove 251 and the cam groove 261.
As described above, the biasing member receiving portion 211 of the biasing barrel 210 is formed with the slope having a predetermined angle from the optical axis.
The phase relationship between components related to the lens apparatus of the present exemplary embodiment will be described with reference to
The second lens holding frame 300 is held on the second lens holding base 200 by the roller 230, and biased by the biasing member 240. A force is received at the position of the biasing member 240 using the position of the roller 230 as a supporting point, and because of this relationship, deformation of the second lens holding frame 300 is also smaller as the roller 230 and the biasing member 240 are closer to each other when receiving the force.
The biasing barrel 210 is held on the guide groove 251 and the cam groove 261 by the second cam follower 221 attached to the cam follower attachment portion 213, and receives a biasing force from the biasing member 240 at the biasing member receiving portion 211. Thus, deformation due to the biasing is smaller as the phase of the biasing member 240 and the phase of the cam follower attachment portion 213, that is, the second cam follower 221, are closer to each other. The possibility of damaging the lens apparatus when the lens apparatus receives a shock due to a fall or the like can be reduced.
The roller 230 is configured so that the position of the second lens holding frame 300 is adjustable by the roller 230 being rotated after the second lens holding base 200 is incorporated into the guide barrel 250 and the cam barrel 260. Thus, an adjustment hole 265 (see
As described above, it is desirable to arrange the first cam follower 220, the biasing member 240, and the roller 230 close to each other in terms of placement phase, and the arrangement of the biasing member 240 between the second cam follower 221 and the roller 230 enables each component to be disposed with a minimum arrangement. When the lens apparatus is viewed in a direction along the optical-axis direction, it is desirable for the phase of the second cam follower 221 and the phase of the roller 230 to fall within 30 degrees. In other words, it is desirable that an angle formed by a line linking the second cam follower 221 and the optical axis and a line linking the roller 230 and the optical axis fall within 30 degrees when the lens apparatus is viewed in the direction along the optical-axis direction. If the second cam follower 221 and the biasing member 240 are disposed in the same phase, it is desirable to arrange these components not to overlap each other in the radial direction, and thus the size increases in the radial direction.
Thus, making the second cam follower 221 and the biasing member 240 different in terms of placement phase (different in the circumferential direction) can provide a configuration achieving a small size.
Next, a biasing force of the first cam follower 220 with respect to the guide groove 251 and the cam groove 261 will be described with reference to
In other words, the force F2 is greater with respect to the force F1 as the angle θ is smaller. The force F1 is greater with respect to the force F2 as the angle θ is larger. In a case where the force F1 is small, the first cam follower 220 easily floats from the guide groove 251, which may lead to a movement of the position of the second lens holding base 200 in the decentration direction. When the force F2 is small, the first cam follower 220 easily floats from the cam groove 261, which may make the second lens holding base 200 move in the optical-axis direction or incline with respect to the optical axis. When the ratio between the force F1 and the force F2 is excessively unbalanced, the spring force is to be increased to satisfy one of the forces, and the other becomes stronger than necessary. This may limit the spring design, and thus it is desirable that the force F1 and the force F2 be well balanced. In the present exemplary embodiment, the first cam follower 220 and the second cam follower 221 make rolling motion using the bearing. Thus, the influence of friction is ignored in the above-described calculation.
Next, the relationship between the biasing member receiving portion 211 of the biasing barrel 210 and the biasing force by the biasing member 240 will be described with reference to
In other words, the force with respect to the guide groove 251 of the first cam follower 220 is adjustable with adoption of the slope angle a of the biasing member receiving portion 211 to match with the angle θ (cam gradient angle) formed by the cam groove 261. In contrast to this, the force in the optical axis cannot be well adjusted. For example, when the coefficient μ is minute in the above-described formula expressing the force F4, F4≈F is determined. A biasing force to be applied to the cam groove 261 is a moment acting on the held unit, specifically, “unit mass×(barycentric position−position of supported component)”.
As this value increases, a force for moving the first cam follower 220 away from the groove when a force is applied by a shock or the like also increases.
In the present exemplary embodiment, the total mass of the second lens holding frame 300 and the second lens unit L2 is not greatly different from the total mass of the second lens holding base 200, the second lens holding frame 300, and the second lens unit L2. This is because only the second lens holding frame 300 holds the optical element. If the distance between the barycentric position of the second lens holding frame 300 including the component held thereby and the roller 230, and the distance between the barycentric position of these including the second lens holding base 200 and the first cam follower 220 are close, the biasing forces, in the optical-axis direction, to be applied are almost the same. In other words, there is no need to increase the force of the biasing member more than necessary because of the limitation by the one side, and thus the size of the biasing member can be reduced.
The structure in which the biasing pin 241 and the biasing spring 242 are used for the biasing member 240 and the biasing member receiving portion 211 formed in the biasing barrel 210 is used is described in the first exemplary embodiment. In a second exemplary embodiment, an example in which a helical extension spring is used will be described.
Thus, the second lens holding frame 300 is biased to the subject side in the direction along the optical axis, and the biasing barrel 210 is biased to the image plane side. The tensile spring 243 is disposed to generate a tension in a direction inclined with respect to the optical axis. Thus, as in the first exemplary embodiment described above, a biasing force is generated in the direction of rotation about the optical-axis direction or the optical axis in the biasing barrel 210 and the second lens holding frame 300. This biasing force makes it possible to hold the second lens holding base 200, the second lens holding frame 300, and the biasing barrel 210 in a cam barrel in which a cam groove is formed and a guide barrel in which a guide groove is formed, while controlling backlash, in a lens apparatus of the present exemplary embodiment as well.
The structure in which the biasing pin 241 and the biasing spring 242 are used for the biasing member 240 and the biasing member receiving portion 211 formed in the biasing barrel 210 is used is described in the first exemplary embodiment. In a third exemplary embodiment, an example in which the biasing direction of a biasing member 240 is different will be described.
The second lens holding frame 300 illustrated in
The interchangeable lens 100 houses an image-capturing optical system that forms an optical image of an object (a subject). An image-capturing light beam from the object passes through the image-capturing optical system and forms an image on a light receiving surface (an imaging plane) of an image sensor. The image sensor photoelectrically converts the optical image of the object formed by the image-capturing optical system.
According to the exemplary embodiments of the present disclosure, it is possible to control backlash between a plurality of components and reduce the size of the lens apparatus. While the exemplary embodiments of the present disclosure have been described, the present disclosure is not limited to these exemplary embodiments, and can be modified and changed in various manners within the scope of the spirit thereof.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2022-059448, filed Mar. 31, 2022, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2022-059448 | Mar 2022 | JP | national |