Lens device and imaging device

Abstract

To provide a lens device advantageous in detecting insertion / removal of a lens group, for example.SOLUTION: A lens device includes: a housing; a lens group that is inserted into and removed from an optical path to change a focal distance of the lens device; a holding member that holds the lens group and causes the lens group to be inserted into and removed from the optical path by rotating around a rotation axis; a magnet that is fixed to one of the holding member and the housing; and a detector that is fixed to the other of the holding member and the housing and detects magnetic flux by the magnet. The magnet and the detector are arranged so that a magnetization direction of the magnet and a detection direction of the detector in which the detector has maximum detection sensitivity are nonparallel to each other in a first state where a distance between the magnet and the detector is minimum and are parallel to each other in a second state where the distance between the magnet and the detector is different from that in the first state.SELECTED DRAWING: Figure 5

Description

Technical Field

[0005]

[0001] The present invention relates to a lens device and an imaging device.

Background Art

[0002] There is known a lens device incorporating an extender lens group that is inserted on an optical path to increase the focal length. The focal length and F-number change depending on whether the extender lens group is on the optical axis. A lens device having a built-in extender structure detects whether the extender lens group is on the optical axis. Based on the result of this detection, the state of the lens device (such as focal length and F-number) is displayed on a viewfinder of a camera or the like.

[0003] A sensor such as a Hall IC can be installed inside the lens device to detect whether the extender lens group is located on the optical path. In Patent Document 1, when the extender lens group is on the optical path, a magnet installed on the lens frame of the extender lens group is detected by the Hall IC. In Patent Document 2, when the extender lens group retreats from the optical path, the magnet is detected by the Hall IC.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the configurations of Patent Documents 1 and 2, the lens frame rotates to insert into and remove from the optical path, and when the lens frame rotates to near the insertion or removal position, the magnetic flux density detected by the Hall IC increases sharply. In Patent Document 1, because the distance from the axis of rotation to the magnet is large, the amount of movement of the magnet with respect to the rotation angle of the lens frame is large. Since the magnet and Hall IC face each other only in the range of small sector rotation angles where the extender lens group is located near the optical path, the magnetic flux density detected by the Hall IC increases sharply. When using a Hall IC that switches between ON and OFF when the magnetic flux density exceeds a threshold, the rotation angle at which ON and OFF switches will vary due to placement errors of the magnet and Hall IC.

[0006] The present invention aims to provide a lens device that is advantageous for detecting the insertion and removal of lens groups, for example. [Means for solving the problem]

[0007] To achieve the above objective, a lens device according to one aspect of the present invention comprises a housing, a group of lenses that change the focal length of the lens device by being inserted into and removed from an optical path, a holding member that holds the group of lenses and rotates around a rotation axis to insert and remove the group of lenses from the optical path, a magnet fixed to one of the holding member and the housing, and a detection unit fixed to the other of the holding member and the housing, which detects the magnetic flux from the magnet, wherein the magnetization direction of the magnet and the detection direction of the detection unit, which has the maximum detection sensitivity, are non-parallel to each other in a first state where the distance between the magnet and the detection unit is minimized, and are parallel to each other in a second state where the distance between the magnet and the detection unit is different from the first state. [Effects of the Invention]

[0008] According to the present invention, for example, a lens device advantageous for detecting the insertion and removal of lens groups can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of a lens device according to an embodiment. [Figure 2] This is a cross-sectional view of the lens device according to the embodiment in its first state. [Figure 3] This is a cross-sectional view of the lens device according to the embodiment in its second state. [Figure 4] This is a cross-sectional view of the lens device according to the embodiment in its third state. [Figure 5] This is a partially enlarged cross-sectional view of the lens device according to the embodiment in its first state. [Figure 6] This is a partially enlarged cross-sectional view of the lens device according to the embodiment in its first state. [Figure 7] This diagram shows the relationship between magnetic flux density and the rotation angle of the rotating support part in the lens device according to the embodiment. [Figure 8] This diagram shows the relationship between magnetic flux density and the rotation angle of the rotating support part in the lens device according to the embodiment. [Figure 9] This diagram shows the relationship between magnetic flux density and the rotation angle of the rotating support part in the lens device according to the embodiment. [Figure 10] This is a schematic diagram of the imaging device of the present invention. [Figure 11] This is a cross-sectional view of a conventional lens device in its first state. [Modes for carrying out the invention]

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail based on the examples shown in Figures 1 to 11. [Examples]

[0011] Figure 1 shows a partial perspective view of the lens device 1 in this embodiment. The lens device 1 has an extender mechanism inside the housing 2 that switches (shifts) the magnification (focal length) of the lens device 1 by inserting and removing it from the optical path, and the magnification is switched by rotating the lever 3. Figure 2 is a cross-sectional view of the state in which the extender lens group 4 is retracted from the optical path (first state) in this embodiment.

[0012] The extender lens group 4 is fixed to the lens barrel 5 by a pressing ring or the like (not shown). The lens barrel 5 is fixed to the cylindrical portion 6a of the rotation support portion (holding member) 6 by screws (not shown). A rotation shaft 7 is provided on the arm portion 6b of the rotation support portion 6. The rotation support portion 6 is engaged with the housing 2 in a rotatable (movable) state around the rotation shaft 7 and is installed in the housing 2. By rotating the lever 3 connected via the connection mechanism, it is inserted into and removed from the optical path. The insertion and removal of the rotation support portion 6 will be described in detail later.

[0013] A circuit board 9 on which a Hall IC 8 is mounted is installed in the housing portion 2a of the housing 2. A relay unit 11 that holds a relay lens group (not shown) is fixed to the imaging surface side of the housing 2, and a mount 12 is fixed to the relay unit 11. The Hall IC 8 detects the magnetic flux generated by the magnet 10 installed on the rotation support portion 6. When the magnetic flux density is low, the Hall IC 8 outputs an OFF signal. When the magnetic flux density exceeds the threshold value, the Hall IC 8 outputs an ON signal. The output signal is transmitted to a camera device (not shown) to which the lens device 1 is attached via a cable (not shown) connected to the circuit board 9 and a contact 13 installed on the mount 12, and the lens state is notified to the user through a viewfinder or the like.

[0014] FIG. 3 is a cross-sectional view of the state (second state) in which the lever 3 is rotated by half from the first state, and FIG. 4 is a cross-sectional view of the state (third state) when the extender lens group 4 is on the optical path. The extender switching structure will be described with reference to FIGS. 2, 3, and 4.

[0015] A gear 14 is fixed to the rotation support portion 6. The gear 14 meshes with a gear 15 fixed to the lever 3. When the lever 3 is rotated counterclockwise as viewed from the imaging surface side from the first state, the rotation support portion 6 moves to the second state and the third state. When the lever 3 is rotated clockwise as viewed from the imaging surface side from the third state, the rotation support portion 6 moves to the second state and the first state.

[0016] A spring 16 is installed on the rotary support portion 6. When the rotary support portion 6 moves between the first state and the second state, the spring 16 biases the rotary support portion 6 in the direction of arrow 17. If the force for operating the lever 3 is smaller than the biasing force, the rotary support portion 6 maintains the first state by the biasing force of the spring 16. On the other hand, when the rotary support portion 6 moves between the second state and the third state, the spring 16 biases the rotary support portion 6 in the direction 18. If the force for operating the lever 3 is smaller than the biasing force, the rotary support portion 6 maintains the third state by the biasing force of the spring 16.

[0017] Next, the positions of the Hall IC 8 and the magnet 10 will be described with reference to FIG. 5. FIG. 5 is a partial cross-sectional view in the first state. The rotary support portion 6 is divided into four spaces by a locus L1 drawn by the optical axis O of the extender lens group 4 when rotating around the rotation axis 7 and a straight line L2 passing through the rotation center O' of the optical axis O and the rotation axis 7. When viewed from the imaging surface side so that the rotation axis 7 exists between the first space and the second space, the first space, the second space, the third space, and the fourth space are defined counterclockwise.

[0018] The magnet 10 is installed in the first space on the outer periphery of the cylindrical portion 6a. The magnet 10 and the Hall IC 8 are in the closest state to each other (the state where the distance between the magnet 10 and the Hall IC 8 is minimized) in the first state. In the first state, the direction parallel to the magnetization direction of the magnet 10 and passing through the center of gravity of the magnet 10 (hereinafter also referred to as the magnetization direction L3) is installed so as to be in an inclined positional relationship with respect to the detection direction L4 of the Hall IC 8. That is, in the first state, the magnetization direction L3 of the magnet 10 and the detection direction L4 of the Hall IC 8 are in a non-parallel relationship in a cross-section perpendicular to the optical axis. In the first state, when the intersection points in the plane perpendicular to the optical axis between the straight line L2 passing through the rotation center O' of the optical axis O of the lens and the rotation axis 7 and the magnetization direction L3 and the detection direction L4 are P3 and P4, the intersection point P4 is located closer to the rotation axis side than the intersection point P3 (FIG. 5). Here, the detection direction L4 of the Hall IC 8 is the direction in which the Hall IC 8 has the highest detection sensitivity. Note that the detection direction of the detection portion having the maximum detection sensitivity of the detection portion may be a direction perpendicular to the detection surface of the detection portion.

[0019] Furthermore, during the transition from the third state to the first state (direction of arrow 17 in the figure), the magnetization direction L3 and the detection direction L4 go from being at an angle to being parallel to each other, and the angle between them increases until they reach a predetermined angle θ in the first state. The predetermined angle θ is preferably between 10 degrees and 45 degrees, more preferably between 20 degrees and 35 degrees, and more preferably between 24 degrees and 30 degrees. In this embodiment, the predetermined angle θ in the first state is 27 degrees.

[0020] If the predetermined angle θ is too small, the magnetization direction L3 and the detection direction L4 become nearly parallel, causing the detected value of the Hall IC to change rapidly when approaching the detection position. This leads to significant variations in the detection angle due to assembly errors of the Hall IC 8, which is undesirable. Conversely, if the predetermined angle θ is too large, the detected value by the Hall IC does not increase easily even when approaching the detection position, reducing the accuracy of the ON / OFF determination based on comparison with the threshold value of the detected value, which is also undesirable.

[0021] As described above, during the transition from the third state to the first state (at a position separated from both the third and first states), there exists a rotation angle of the rotation support 6 in which the magnetization direction L3 and the detection direction L4 are parallel to each other. In the state during the transition from the third state to the first state in which the magnetization direction L3 and the detection direction L4 are parallel to each other, the straight line of the detection direction L4 is closer to the rotation axis 7 than the straight line of the magnetization direction L3.

[0022] Furthermore, in the embodiment, the magnet 10 is fixed to the cylindrical portion 6a of the rotating support portion 6 such that the magnetization direction L3 passes through the optical axis O of the extender lens group 4, but the present invention is not limited to this configuration.

[0023] In the first state, the Hall IC 8 and the magnet 10 are configured such that the projection of the shape of the magnet 10 onto a plane perpendicular to the magnetization direction L3 overlaps with at least a portion of the detection unit 8a of the Hall IC 8. More preferably, in the first state, the Hall IC 8 and the magnet 10 are configured such that a straight line in the magnetization direction L3 passes through the detection unit 8a of the Hall IC 8. In a cross section perpendicular to the magnetization direction L3, the magnetic flux density due to the magnet 10 is high in the magnetization direction L3, and this configuration makes it possible to increase the magnetic flux detected by the detection unit 8a in the first state.

[0024] The magnet 10 is positioned on the cylindrical portion 6a on the side of the rotation center O' (towards the rotation axis 7) of the trajectory L1 traced by the optical axis O of the extender lens group 4, which is caused by the rotation of the rotation support portion 6 around the rotation center O' of the rotation axis 7. In other words, the distance from the rotation axis 7 to the magnet 10 is shorter than the distance from the rotation axis 7 to the optical axis O of the extender lens group 4. This suppresses the amount of movement of the magnet 10 relative to the Hall IC 8 per rotation angle, thereby suppressing abrupt changes in magnetic flux density.

[0025] Furthermore, as shown in Figure 6, the Hall IC 8 is positioned on the side of the rotation axis 7 (direction 19) of the magnet 10 in the direction passing through the optical axis O of the lens and the rotation center O' of the rotation axis 7 in the first state within a plane perpendicular to the optical axis. That is, as shown in Figure 6, in the direction connecting the optical axis O of the lens and the rotation center O' of the rotation axis 7 in the first state, the distance D1 between the Hall IC 8 and the rotation center O' is shorter than the distance D2 between the magnet 10 and the rotation center O'. In other words, in the first state, the magnetization direction L3 of the magnet 10 is positioned so that it passes from the cylindrical part 6a through the inside of the housing part 2a without passing through the side wall of the housing part 2a. As a result, compared to the conventional arrangement illustrated in Figure 11, the Hall IC 8 can be positioned at a distance from the outer wall 2b of the housing part 2a, making it less likely for false detections to occur due to the influence of magnetic flux from magnets approaching from the outside.

[0026] Figure 11 is a partial cross-sectional view of the state in which the extender lens group 4 is retracted from the optical path (first state) in the conventional example. In the first state, the Hall IC 8 and the magnet 10 face each other at a position where the magnetic flux density detected by the Hall IC 8 is the same as in the embodiment, and the magnetization direction L3 of the magnet 10 and the detection direction L4 of the Hall IC coincide.

[0027] Figure 7 is a graph showing the relationship between the rotation angle of the rotation support unit 6 and the magnetic flux density of the magnet 10 input to the Hall IC 8 when the lever 3 is operated from the second state to the first state in this embodiment (Figure 5) and the conventional example (Figure 11). If 20% of the maximum magnetic flux density detected by the Hall IC 8 in the first state is used as the threshold for the Hall IC 8 to switch between ON and OFF, in this embodiment, the rotation support unit 6 exceeds the threshold at 7.8 degrees to the first state, and an ON signal is transmitted to the camera. On the other hand, in the conventional example, the rotation support unit 6 exceeds the threshold at 6.6 degrees to the first state, and an ON signal is transmitted to the camera. Next, referring to Figures 8 and 9, we will explain the effects of assembly errors in Hall ICs.

[0028] Figure 8 is a graph showing the relationship between the rotation angle of the rotation support part 6 and the magnetic flux density detected by the Hall IC 8 when the Hall IC 8 is shifted in direction 19, in the present invention shown in Figure 5 and the conventional example shown in Figure 11. The solid line represents the design value in this embodiment, and the dashed line represents the case where the Hall IC 8 is shifted by 0.5 mm in direction 19 from the design value in the embodiment. Furthermore, the dashed line represents the case where the conventional example is installed at the design position, and the dashed line represents the case where the conventional example is shifted by 0.5 mm in direction 19 from the design position. When the detection threshold is set to 20%, it can be seen that the detection angle in the conventional example changes from 6.6 degrees to 5.7 degrees, while in this embodiment it hardly changes.

[0029] Figure 9 is a graph showing the relationship between the rotation angle of the rotation support 6 and the input magnetic flux density when the Hall IC 8 is shifted in direction 19 in Figure 5. The solid line represents the case where the device is installed at the design position in this embodiment, and the dashed line represents the case where the device is shifted by 0.5 mm in direction 20 relative to the design position in this embodiment. The dashed line represents the case where the device is installed at the design position in the conventional example, and the dashed line represents the case where the device is shifted by 0.5 mm in direction 20 relative to the design position in the conventional example. It can be seen that the detection angle changes from 6.6 degrees to 6 degrees in the conventional example, while it changes from 7.8 degrees to 8.1 degrees in this embodiment.

[0030] As described above, if the Hall IC is installed in a position deviating from the design position, this embodiment can suppress the change in magnetic flux density detected by the Hall IC 8 to a smaller extent than in the conventional example. As a result, even if there is an assembly error (assembly variation) in the Hall IC 8, the rotation angle of the rotation support part 6 can be detected at an angle closer to the design value.

[0031] As described above, in the lens device of this embodiment, when the extender lens group 4 is retracted from the optical path (first state), the magnetization direction L3 of the magnet 10 and the detection direction L4 of the Hall IC 8 are set to be tilted in the rotational direction (direction of arrow 17). This increases the rotation angle of the rotation support part 6 in which the Hall IC 8 detects a magnetic flux density above a threshold, and suppresses changes in the detection angle due to assembly variations of the Hall IC 8, enabling stable detection.

[0032] In this embodiment, the position where the extender lens group 4 is retracted from the optical path is detected, but this is not limited to this. For example, the magnet 10 may be placed in the second space of the rotating support part 6, and the Hall IC 8 may be installed to detect when it is in the optical path.

[0033] Furthermore, although the embodiment illustrates a configuration in which a magnet 10 is installed on a rotating support 6 that holds the extender lens group 4 and a Hall IC 8 is fixed to the housing 2a of the housing 2, the present invention is not limited to this. The magnet can be fixed to either the rotating support 6 or the housing 2, and the Hall IC that detects the proximity of the magnet when the rotating support 6 is in either the optical path position or the retracted position can be fixed to the other of the rotating support 6 and the housing 2. In other words, the Hall IC can be installed on the rotating support 6 that holds the extender lens group 4 and a magnet can be fixed to the housing 2a of the housing 2. In that case, the installation positions of the magnet and the Hall IC are swapped compared to the illustrated embodiment, and the magnetization direction and detection direction are swapped, but the same effect can be achieved.

[0034] Figure 10 shows a schematic diagram of an imaging device 300, which includes a lens device 1 of the present invention and a camera device 200 having an image sensor 201 that captures the image formed by the lens device 1. The lens device 1 includes an extender lens group 4, indicated by the optical path position (solid line) and retracted position (dashed line) as described in the above embodiment, and other optical systems G1, and is connected to the camera device 200 via a mount 12. With such a configuration, an imaging device that enjoys the effects of the present invention can be realized.

[0035] This embodiment includes the following configuration. (Composition 1) The casing and A group of lenses that change the focal length of the lens device by being inserted into or removed from the optical path, A holding member that holds the lens group and rotates around a rotation axis to insert and remove the lens group from the optical path, A magnet fixed to one of the holding member and the housing, A lens device having a detection unit fixed to the other of the holding member and the housing, which detects the magnetic flux produced by the magnet, A lens device characterized in that the magnet and the detection unit are arranged such that the magnetization direction of the magnet and the detection direction of the detection unit having the maximum detection sensitivity are non-parallel to each other in a first state where the distance between the magnet and the detection unit is minimized, and are parallel to each other in a second state where the distance between the magnet and the detection unit is different from the first state. (Configuration 2) The lens device according to configuration 1, characterized in that, in the first state, in a plane perpendicular to the optical axis of the lens group, the detection unit is positioned closer to the rotation axis than the magnet with respect to the direction connecting the rotation axis and the optical axis. (Composition 3) The lens device according to configuration 2, characterized in that the distance from the rotation axis to the magnet is shorter than the distance from the rotation axis to the optical axis. (Composition 4) The housing has a housing section for housing the detection unit, The lens device according to configuration 3, characterized in that, in the first state, the magnet is arranged such that a straight line parallel to the magnetization direction and passing through the center of gravity of the magnet passes through the inside of the housing. (Composition 5) The lens device according to configuration 4, characterized in that, in the first state, the magnet and the detection unit are arranged such that the projection of the magnet in the magnetization direction overlaps with at least a part of the detection unit. (Composition 6) The lens device according to configuration 5, characterized in that, in the first state, the magnet and the detection unit are arranged such that a straight line parallel to the magnetization direction of the magnet and passing through the center of gravity of the magnet passes through the detection unit. (Composition 7) The lens device according to any one of configurations 1 to 5, characterized in that the holding member has a cylindrical portion for holding the lens group and an arm portion engaged with the rotation axis, and the magnet is fixed to the cylindrical portion. (Composition 8) An imaging device characterized by including a lens device described in any one of configurations 1 to 7, and an image sensor for capturing an image formed by the lens device.

[0036] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its essence. [Explanation of Symbols]

[0037] 1: Lens device 4: Extender lens group 6: Rotating support part (lens frame) 7: Rotation axis 8: Hall IC (detection unit) 10: Magnet

Claims

1. The casing and A group of lenses that change the focal length of the lens device by being inserted into or removed from the optical path, A holding member that holds the lens group and rotates around a rotation axis to insert and remove the lens group from the optical path, A magnet fixed to one of the holding member and the housing, A lens device having a detection unit fixed to the other of the holding member and the housing, which detects the magnetic flux produced by the magnet, A lens device characterized in that the magnet and the detection unit are arranged such that the magnetization direction of the magnet and the detection direction of the detection unit having the maximum detection sensitivity are non-parallel to each other in a first state where the distance between the magnet and the detection unit is minimized, and are parallel to each other in a second state where the distance between the magnet and the detection unit is different from the first state.

2. The lens device according to claim 1, characterized in that, in the first state, in a plane perpendicular to the optical axis of the lens group, the detection unit is positioned closer to the rotation axis than the magnet with respect to the direction connecting the rotation axis and the optical axis.

3. The lens device according to claim 2, characterized in that the distance from the rotation axis to the magnet is shorter than the distance from the rotation axis to the optical axis.

4. The housing has a housing section for housing the detection unit, The lens device according to claim 3, characterized in that, in the first state, the magnet is arranged such that a straight line parallel to the magnetization direction and passing through the center of gravity of the magnet passes through the inside of the housing.

5. The lens device according to claim 4, characterized in that, in the first state, the magnet and the detection unit are arranged such that the projection of the magnet in the magnetization direction overlaps with at least a part of the detection unit.

6. The lens device according to claim 5, characterized in that, in the first state, the magnet and the detection unit are arranged such that a straight line parallel to the magnetization direction of the magnet and passing through the center of gravity of the magnet passes through the detection unit.

7. The lens device according to claim 1, characterized in that the holding member has a cylindrical portion for holding the lens group and an arm portion engaged with the rotation axis, and the magnet is fixed to the cylindrical portion.

8. An imaging device comprising a lens device according to any one of claims 1 to 7, and an image sensor for capturing an image formed by the lens device.

Images