Optical filter switching device and imaging device

Abstract

To provide an optical filter switching device capable of suppressing strength decrease, while reducing a thickness in an optical axis direction.SOLUTION: The optical filter switching device capable of switching a plurality of optical filters arranged on the optical path of an optical system includes a first holding frame in which a first optical filter is arranged and a second holding frame in which a second optical filter is arranged. The first holding frame has an opening through which light passes and the second holding frame is arranged in a position where a part of the second holding frame is overlapped with the opening, when viewed from a direction orthogonal to the optical axis direction of the optical system.SELECTED DRAWING: Figure 5

Description

Technical Field

[0005]

[0001] The present invention relates to an optical filter switching device and an imaging device.

Background Art

[0002] Conventionally, for example, there has been an imaging device provided with a plurality of ND filters having different densities and an optical filter switching mechanism for selectively inserting an ND filter having a desired density onto an optical path by switching the positions of each ND filter. In particular, since it is necessary to arrange the filter switching mechanism in a narrow region between the photographing lens and the imaging element, it has been desired to further reduce the thickness of the optical filter switching mechanism.

[0003] Therefore, in Patent Document 1, the optical filter device has a configuration including a first optical filter, a first holding frame, two first supports, a first electric motor, a first transmission mechanism, a second optical filter, a second holding frame, two second supports, a second electric motor, and a second transmission mechanism.

[0004] At this time, the distance from one of the two first supports that supports the first side portion of the first holding frame to the optical axis is made different from the distance from one of the two second supports that supports the first side portion of the second holding frame to the optical axis. Further, the distance from the other first support that supports the second side portion of the first holding frame among the two first supports to the optical axis is made different from the distance from the other second support that supports the second side portion of the second holding frame among the two second supports to the optical axis. By adopting such a configuration, the thickness of the optical filter switching mechanism in the optical axis direction is reduced.

Prior Art Documents

Patent Documents

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the conventional technology described in Patent Document 1, if the optical filter switching mechanism is to be placed in a narrower area, the filter and the holder that holds the filter must be made thinner, which may lead to a decrease in strength.

[0007] Therefore, the present invention aims to provide an optical filter switching device that reduces the thickness in the optical axis direction while suppressing a decrease in intensity. [Means for solving the problem]

[0008] To achieve the above objective, an optical filter switching device as one aspect of the present invention is an optical filter switching device capable of switching a plurality of optical filters arranged on the optical path of an optical system, comprising a first retaining frame on which a first optical filter is arranged and , the A second retaining frame in which two optical filters are placed, A light-shielding member is positioned between the first optical filter and the first retaining frame, The first retaining frame has an opening through which light passes, and the second retaining frame is positioned such that a portion of the second retaining frame overlaps with the opening when viewed from a direction perpendicular to the optical axis of the optical system. be It is characterized by the following: [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an optical filter switching device that reduces the thickness in the optical axis direction while suppressing a decrease in intensity. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of the imaging device according to Embodiment 1. [Figure 2] This is an exploded perspective view of the imaging device according to Embodiment 1. [Figure 3] This is a cross-sectional view of the imaging device according to Embodiment 1. [Figure 4] This is an exploded perspective view of the optical filter switching unit according to Embodiment 1. [Figure 5] This is a cross-sectional view of an optical filter switching unit according to Embodiment 1. [Figure 6] This is an enlarged view of the vicinity of the optical filter in a cross-sectional view of the optical filter switching unit according to Embodiment 1. [Figure 7] This is a front view of the IR cut filter holding frame according to Embodiment 1. [Figure 8] This is a cross-sectional view of the IR cut filter holding frame according to Embodiment 1. [Figure 9] This is a rear view of the ND filter holding frame according to Embodiment 1. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the attached drawings. The embodiments described below are examples of means for realizing the present invention and should be modified or changed as appropriate depending on the configuration of the apparatus to which the present invention is applied and various conditions, and the present invention is not limited to the embodiments described below.

[0012] <Embodiment 1> Figure 1 is a perspective view of the imaging device 1 according to this embodiment. Figure 2 is an exploded perspective view of the imaging device 1 according to this embodiment. Figure 3 is a cross-sectional view of the imaging device 1 according to this embodiment. Note that OA in the imaging device 1 shown in Figure 3 indicates the optical axis direction (direction along the optical axis) in an optical system not shown.

[0013] The imaging device 1 includes a camera mount 2, an optical filter switching unit (optical filter switching device) 3, an image sensor unit 4, a printed circuit board 5, and a housing 6.

[0014] The camera mount 2 is formed in an annular shape and can detachably secure a photographic lens (optical element), which is an optical system not shown. The camera mount 2 is held in the housing 6.

[0015] The optical filter switching unit 3 can selectively move an optical filter such as an IR cut filter 14 and an ND filter 23 into or out of the optical path by driving a drive mechanism (drive device) such as motors 29 and 30. That is, the IR cut filter 14 and the ND filter 23 can be switched by moving them in a direction orthogonal to the optical axis OA of the optical system so as to be inserted into and retracted from the optical path of the optical system. The IR cut filter (first optical filter) 14 functions as a filter that transmits visible wavelength light and blocks near-infrared wavelength light, and the ND filter (second optical filter) 23 functions as a filter that attenuates visible wavelength light. The optical filter switching unit 3 in the present embodiment is disposed between the camera mount 2 and the imaging element unit 4. Details of the optical filter switching unit 3 will be described later.

[0016] The imaging element unit 4 converts light that has passed through a photographing lens (not shown) into an electronic signal. The imaging element unit 4 in the present embodiment is disposed between the optical filter switching unit 3 and the printed circuit board 5.

[0017] The printed circuit board 5 is provided with a video processing engine, a communication processing engine, a memory, a power supply system IC, etc., and is connected to the camera mount 2, the optical filter switching unit 3, the imaging element unit 4, and an input / output connector (not shown) via lines. The printed circuit board 5 in the present embodiment is disposed inside the housing 6.

[0018] The housing 6 houses the optical filter switching unit 3, the imaging element unit 4, and the printed circuit board 5 inside, and the camera mount 2 is held by being assembled to the housing 6.

[0019] The optical filter switching unit 3 of this embodiment will be described below with reference to Figures 4 to 9. Figure 4 is an example of an exploded perspective view of the optical filter switching unit 3 according to this embodiment. Figure 5 is an example of a cross-sectional view of the optical filter switching unit 3 according to this embodiment. Figure 6 is an enlarged view of the vicinity of each optical filter shown in Figure 5. Figure 7 is an example of a front view of the IR cut filter holding frame 13 according to this embodiment. Figure 8 is an example of a cross-sectional view of the IR cut filter holding frame 13 according to this embodiment.

[0020] The base member 11 and the cover member 12 are members that hold the guide bar (first support member) 20 and the guide bar (second support member) 26, which will be described later. Specifically, the guide bar 20 and the guide bar 26 are held and fixed by being sandwiched between the base member 11 and the cover member 12 in the direction of the optical axis OA. Furthermore, the base member 11 is configured to hold the motor 29 and the motor 30, which will be described later.

[0021] The IR cut filter holding frame (first holding frame) 13 has a sleeve portion 18 and an IR cut filter holding portion 34. The IR cut filter holding portion 34 fixes the IR cut filter 14 and the dummy glass 15 by holding them. The IR cut filter holding portion 34 is provided on the IR cut filter holding frame 13 in a direction parallel to the direction SA, which is the switching direction of each optical filter (IR cut filter 14, ND filter 23), that is, in a direction perpendicular to the optical axis OA.

[0022] The sleeve portion 18 engages with the guide bar 20, which is a support member that supports the IR cut filter holding frame 13 in a direction perpendicular to the optical axis OA. The engagement of the sleeve portion 18 with the guide bar 20 allows the IR cut filter holding frame 13 to be supported so as to be movable in a direction perpendicular to the optical axis OA. The IR cut filter holding frame 13 is also provided with a U-groove 19. The U-groove 19 is a groove configured such that its cross-section in the direction of the optical axis OA is U-shaped. The U-groove 19 engages with the guide bar 26, which supports the ND filter holding frame 22 (described later) in a direction perpendicular to the optical axis OA. The engagement of the U-groove 19 with the guide bar 26 restricts the rotation of the IR cut filter holding frame 13 around the guide bar 20.

[0023] The IR cut filter holding portion (first filter holding portion) 34 is formed on the IR cut filter holding frame 13 so as to have a predetermined width in the optical axis direction OA. The IR cut filter 14 and the dummy glass 15 are held by the IR cut filter holding portion 34 at a position closer to the subject side than to the imaging plane side in the optical axis direction OA of the IR cut filter holding portion, as shown in Figure 5.

[0024] The aperture 35 is formed in the IR cut filter holding portion 34. That is, the aperture 35 is configured to have a predetermined dimension toward the imaging surface in the optical axis OA direction from the imaging surface side of the IR cut filter 14 and the dummy glass 15. Furthermore, as shown in Figure 6 and other figures, the aperture 35 is configured as an aperture region with a concave cross-section in the optical axis OA direction.

[0025] The incident light that has passed through the IR cut filter 14 or the dummy glass 15 passes through the aperture 35 to the imaging surface. Furthermore, both the IR cut filter 14 and the dummy glass 15 are held by the IR cut filter holder 34, thereby restricting their position in the optical axis direction OA. In other words, the movement of the IR cut filter 14 and the dummy glass 15 in the optical axis direction OA is restricted by being held by the IR cut filter holder 34.

[0026] The IR cut filter mask 16 is held in place by being sandwiched between the IR cut filter holding frame 13 and the IR cut filter 14. The dummy glass mask 17 is held in place by being sandwiched between the IR cut filter holding frame 13 and the dummy glass 15. The IR cut filter mask 16 and the dummy glass mask 17 are light-shielding members that cut out unwanted light incident on the image sensor unit 4.

[0027] The rack member 21 is fixed to the IR cut filter holding frame 13 while biased by a rack spring (not shown) in a direction perpendicular to the optical axis OA and in a rotational direction around the center of the optical axis OA. The rack member 21 is engaged with a screw portion (not shown) of the motor 30, and the rotation of the screw portion causes it to move together with the IR cut filter holding frame 13 in a direction perpendicular to the optical axis OA.

[0028] Figure 9 is an example of a rear view of the ND filter holding frame 22. The ND filter holding frame (second holding frame) 22 has a sleeve portion 25, an ND filter holding portion 36, and an ND filter fixing portion 37.

[0029] The sleeve portion 25 engages with the guide bar 26, which is a support member that supports the ND filter holding frame 22 in a direction perpendicular to the optical axis OA. By engaging the sleeve portion 25 with the guide bar 26, the ND filter holding frame 22 is supported so as to be movable in a direction perpendicular to the optical axis OA. The ND filter holding frame 22 is also provided with a U-groove 27. The U-groove 27 is a groove portion configured so that its cross-section in the direction of the optical axis OA is U-shaped. The U-groove 27 engages with the guide bar 20, which is a support member that supports the IR cut filter holding frame 13 in a direction perpendicular to the optical axis OA. By engaging the U-groove 27 with the guide bar 20, the rotation of the ND filter holding frame 22 around the guide bar 26 is restricted.

[0030] The ND filter holder (second filter holder) 36 holds the ND filter 23 and the dummy glass 24. The ND filter holder 36 holds the ND filter 23 and the dummy glass 24, thereby restricting their position in the direction along the optical axis OA. That is, by being held by the ND filter holder 36, the movement of the ND filter 23 and the dummy glass 24 in the direction of the optical axis OA is restricted. The ND filter 23 and the dummy glass 24, held by the ND filter holder 36, are both fixed to the ND filter holder frame 22 by the ND filter fixing part 37.

[0031] The rack member 28 is fixed to the ND filter holding frame 22 while biased by a rack spring (not shown) in a direction perpendicular to the optical axis OA and in a rotational direction around the center of the optical axis OA. The rack member 28 is engaged with the screw portion of the motor 29, and the rotation of the screw portion causes it to move together with the ND filter holding frame 22 in a direction perpendicular to the optical axis OA.

[0032] As described above, the guide bar 20 that engages with the sleeve portion 18 and the guide bar 26 that engages with the sleeve portion 25 are held and fixed by being sandwiched between the base member 11 and the cover member 12.

[0033] Motors 29 and 30 are each fixed to the base member 11. In this embodiment, motors 29 and 30 are configured as, for example, stepping motors, but are not limited to this, and may be configured as, for example, servo motors.

[0034] The cover glass 31 is fixed to the cover member 12 by the cover glass holding member 32. This cover glass 31 prevents dust and other foreign matter from entering the inside of the optical filter switching unit 3 from the camera mount 2 side (subject side).

[0035] In this embodiment, the ND filter holding frame 22 in the optical filter switching unit 3 is positioned on the image plane side of the IR cut filter holding frame 13 in the optical axis OA direction, as described above. In addition, a portion of the ND filter holding frame 22 is positioned to extend into the aperture 35. That is, when viewed from a direction perpendicular to the optical axis direction of the optical system, the ND filter holding frame 22 is positioned such that a portion of it overlaps with a portion of the aperture 35. By arranging the ND filter holding frame 22 in this way, the distance between the IR cut filter 14 and dummy glass 15 and the ND filter holding frame 22 in the optical axis OA direction can be shortened.

[0036] This makes it possible to reduce the thickness of the optical filter switching unit 3 near the optical axis OA without reducing the thickness of the IR cut filter 14 and ND filter 23, the IR cut filter retaining frame 13, and the ND filter retaining frame 22. As a result, a decrease in the strength of the optical filter switching unit 3 can be suppressed.

[0037] Furthermore, in the optical filter switching unit 3 of this embodiment, the incident light that passes through the photographic lens is incident on the image sensor unit 4 at an angle, so the diameter of the light rays passing through the IR cut filter 14 is larger than the diameter of the light rays passing through the ND filter 23. Therefore, by positioning the ND filter holding frame 22 closer to the image plane in the optical axis OA direction than the IR cut filter holding frame 13, the size of the ND filter 23 in the direction perpendicular to the optical axis OA can be reduced. This makes it possible to suppress the enlargement of the imaging device 1 in the direction perpendicular to the optical axis OA.

[0038] Furthermore, in the optical filter switching unit 3 of this embodiment, the IR cut filter holding section 34 and the ND filter holding section 36 are arranged opposite each other in the direction of the optical axis OA. This arrangement makes it possible to suppress the generation of unwanted light due to reflection at the ND filter fixing section 37.

[0039] Furthermore, in the optical filter switching unit 3 of this embodiment, guide bars 20 and 26 are positioned closer to the image plane than the ND filter 23 in the optical axis direction OA. This arrangement allows for effective use of the space around the image sensor unit 4, thereby suppressing the need to increase the size of the imaging device 1.

[0040] By adopting the above configuration, it is possible to suppress the decrease in strength of the optical filter switching unit 3 and provide an imaging device 1 equipped with an optical filter switching unit 3 with reduced thickness in the optical axis direction OA.

[0041] In this embodiment, the filter holding frame driven by motors 29 and 30 consists of two frames: an IR cut filter holding frame 13 and an ND filter holding frame 22. Furthermore, the optical filter consists of a total of four filters: an IR cut filter 14, an ND filter 23, and two dummy glass pieces (dummy glass 15 and dummy glass 24). However, the number of filter holding frames and filters is not limited to this and can be any number.

[0042] This embodiment includes the following configuration. (Composition 1) An optical filter switching device capable of switching between a plurality of optical filters arranged on the optical path of an optical system, comprising a first holding frame on which a first optical filter is arranged, and a second holding frame on which a second optical filter is arranged, wherein the first holding frame has an opening through which light passes, and the second holding frame is positioned such that a part of the second holding frame overlaps with the opening when viewed from a direction perpendicular to the optical axis of the optical system.

[0043] (Configuration 2) The optical filter switching device according to configuration 1, characterized in that the first retaining frame has a first filter retaining portion for holding a first optical filter, and the first filter retaining portion is provided on the first retaining frame along the switching direction of the first optical filter and the second optical filter.

[0044] (Composition 3) The optical filter switching device according to configuration 2, characterized in that the first optical filter is held by a first filter holding part, thereby restricting its movement in the optical axis direction.

[0045] (Composition 4) The optical filter switching device according to configuration 2, characterized in that the second retaining frame has a second filter retaining portion, and the first filter retaining portion and the second filter retaining portion are arranged to face each other in a direction along the optical axis.

[0046] (Composition 5) The optical filter switching device according to configuration 4, characterized in that the movement of the second optical filter in the optical axis direction is restricted by being held by the second filter holding part.

[0047] (Composition 6) An optical filter switching device according to any one of configurations 1 to 5, characterized by having a light-shielding member disposed between a first optical filter and a first retaining frame.

[0048] (Composition 7) The optical filter switching device according to any one of configurations 1 to 6, characterized in that the second retaining frame is positioned on the image plane side of the first retaining frame.

[0049] (Composition 8) An optical filter switching device according to any one of configurations 1 to 5, characterized by having a first support member that supports a first retaining frame in a direction perpendicular to the optical axis, and a second support member that supports a second retaining frame in a direction perpendicular to the optical axis.

[0050] (Composition 9) The optical filter switching device according to configuration 8, characterized in that the first support member and the second support member are arranged on the image plane side of the first optical filter and the second optical filter.

[0051] (Composition 10) An optical filter switching device according to any one of configurations 1 to 9, further comprising a drive mechanism that enables switching between a first optical filter and a second optical filter by moving the first optical filter or the second optical filter in a direction perpendicular to the optical axis of the optical system so as to insert and retract the first optical filter relative to the optical path of the optical system.

[0052] (Composition 11) The optical filter switching device according to any one of configurations 1 to 10, characterized in that the first optical filter is an IR cut filter that transmits visible wavelength light and blocks near-infrared wavelength light.

[0053] (Composition 12) The optical filter switching device according to any one of configurations 1 to 10, characterized in that the second optical filter is an ND filter that attenuates visible wavelength light.

[0054] (Composition 13) Optical system and An imaging apparatus characterized by having an optical filter switching device described in any one of configurations 1 to 12.

[0055] 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 gist. [Explanation of Symbols]

[0056] 1. Imaging device 2 Camera Mounts 3. Optical filter switching unit 4 Image sensor unit 5 Printed circuit boards 6 cabinets 11 Base member 12 Cover component 13 IR cut filter holding frame 14 IR cut filter 15, 24 Dummy glass 16 IR Cut Filter Mask 17 Dummy glass mask 18, 25 Sleeve section 19, 27 U-groove 20, 26 Guide bars 21, 28 Rack components 22 ND filter holder frame 23 ND filter 29, 30 motors 31 Cover glass 32 Cover glass retaining member

Claims

1. An optical filter switching device capable of switching between multiple optical filters arranged on the optical path of an optical system, A first retaining frame on which the first optical filter is placed, A second retaining frame in which a second optical filter is positioned, The device comprises a light-shielding member disposed between the first optical filter and the first retaining frame, The first retaining frame has an opening through which light passes, The second retaining frame is positioned such that, when viewed from a direction perpendicular to the optical axis of the optical system, a portion of the second retaining frame overlaps with the opening. An optical filter switching device characterized by the following features.

2. The first retaining frame has a first filter retaining portion for holding the first optical filter, The optical filter switching device according to claim 1, characterized in that the first filter holding portion is provided on the first holding frame along the switching direction of the first optical filter and the second optical filter.

3. The optical filter switching device according to claim 2, characterized in that the movement of the first optical filter in the optical axis direction is restricted by being held by the first filter holding part.

4. The second retaining frame has a second filter retaining portion, The optical filter switching device according to claim 2, characterized in that the first filter holding portion and the second filter holding portion are arranged to face each other in a direction along the optical axis.

5. The optical filter switching device according to claim 4, characterized in that the second optical filter is held by the second filter holding part, thereby restricting its movement in the optical axis direction.

6. A first support member that supports the first retaining frame in a direction perpendicular to the optical axis, The optical filter switching device according to claim 1, further comprising a second support member that supports the second retaining frame in a direction perpendicular to the optical axis.

7. The optical filter switching device according to claim 6, characterized in that the first support member and the second support member are arranged on the image plane side of the first optical filter and the second optical filter.

8. The optical filter switching device according to claim 1, further comprising a drive mechanism that enables switching between the first optical filter and the second optical filter by moving the first optical filter or the second optical filter in a direction perpendicular to the optical axis of the optical system so as to insert and retract the first optical filter or the second optical filter relative to the optical path of the optical system.

9. The optical filter switching device according to claim 1, characterized in that the first optical filter is an IR cut filter that transmits visible wavelength light and blocks near-infrared wavelength light.

10. The optical filter switching device according to claim 1, characterized in that the second optical filter is an ND filter that attenuates visible wavelength light.

11. Optical system and An imaging apparatus characterized by having an optical filter switching device according to any one of claims 1 to 10.

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