JP2024011140A - Optical filter unit, imaging apparatus, and optical device - Google Patents

Abstract

To provide an optical filter unit that comprises both an ND filter and a polarization filter which can be inserted into and withdrawn from an optical path without enlarging and complicating a device.SOLUTION: An optical filter unit 100 has first filter switching means 140 and second filter switching means 150 arranged in series along an axial direction parallel to an optical axis. The first filter switching means is provided with a polarization filter area A1 and a non-polarization filter area A2. The first filter switching means rotates around a rotation axis parallel to the optical axis to allow either one of the polarization filter area or the non-polarization filter area to be inserted into the optical path. The second filter switching means is provided with a plurality of optical filters 152, 153, 154, one of which is a polarization filter. The second filter switching means allows any one of the plurality of optical filters to be inserted into the optical path.SELECTED DRAWING: Figure 6

Description

The present invention relates to an optical filter unit, and particularly to an optical filter unit that includes both a polarizing filter and an ND filter.

Imaging devices such as surveillance cameras are required to have the ability to obtain good image quality regardless of day or night. On the other hand, since the photographing conditions differ greatly during the day and at night, the performance required of the imaging device differs greatly between the day and night.

During the daytime when the influence of sunlight is strong, optical filters such as polarizing filters and ND (neutral density) filters are generally used to improve image quality. For example, under conditions where strong light from sunlight is reflected on window glass, water surfaces, etc., a polarizing filter (PL filter) is used to suppress glare caused by the reflected light. Thereby, it is possible to remove a specific polarized light component that is included in a large amount in the reflected light. Furthermore, a polarizing filter has an optimal polarization angle depending on photographing conditions. Therefore, it is important for the user to adjust the polarization angle of the polarizing filter to obtain the optimum polarization angle according to the shooting conditions.

Furthermore, in situations where exposure is excessive due to sunlight or the like, an ND (neutral density) filter is used. Thereby, it is possible to reduce the amount of light incident on the image sensor and prevent overexposure of the photographed image.

On the other hand, when photographing at night, while there is no adverse effect from sunlight as described above, there may be a problem that a bright and clear image cannot be obtained due to insufficient light around the subject. Both ND filters and polarizing filters have the effect of reducing incident light, so when photographing at night, it is important to remove these optical filters to increase the amount of light incident on the image sensor.

Therefore, while it is desirable to use polarizing filters and ND filters during the day to suppress glare caused by reflected light and to prevent overexposure, there is a desire to remove these filters at night to photograph as brightly as possible. Further, since the ND filter and the polarizing filter are used in different use cases, it is convenient if they can be easily switched.

Patent Document 1 and Patent Document 2 disclose techniques related to imaging devices incorporating these optical filters.

In Patent Document 1, a filter turret in which a plurality of infrared cut filters are arranged in the circumferential direction is built into an imaging device, and by rotating the filter turret, it is possible to switch the filters inserted into the optical path. Furthermore, by providing a rotatable polarizing filter for any one of the infrared cut filters, it is possible to insert/remove the polarizing filter into the optical path and adjust the polarization angle.

In Patent Document 2, two filter turrets each having two optical filters (ND filters) on the same surface are arranged so as to overlap on the optical path, and are inserted into the optical path by rotating each turret. A technique is disclosed in which optical filters can be individually switched.

JP2017-067865A Japanese Patent Application Publication No. 2016-095451

However, with the technique shown in Patent Document 1, while it is possible to insert and remove the polarizing filter and rotate it, the effect of the ND filter cannot be obtained. If an attempt is made to add ND filters with various light attenuation rates, additional filter holders for the number of ND filters to be added will be required, which may cause the device to become more complicated and larger.

In the technique disclosed in Patent Document 2, it is possible to arrange ND filters having different light attenuation rates in two of the three openings arranged in the circumferential direction of each turret. However, the configuration described in Patent Document 2 does not include a polarizing filter. If a polarizing filter were to be added, a separate mechanism for inserting and removing the polarizing filter and a mechanism for adjusting the polarization angle would be required, which could lead to the device becoming more complicated and larger.

The present invention provides an optical filter unit that includes both an ND filter and a polarizing filter that can be inserted into and removed from an optical path without increasing the size and complexity of the device.

An optical filter unit as one aspect of the present invention is an optical filter unit having a first filter switching means and a second filter switching means arranged in series along an axial direction parallel to the optical axis, The first filter switching means is provided with a polarizing filter region and a non-polarizing filter region, and the first filter switching means rotates around a rotation axis parallel to the optical axis to Either the polarizing filter region or the non-polarizing filter region can be inserted into the optical path, and the second filter switching means is provided with a plurality of optical filters, one of which is a polarizing filter, and the second filter switching means is provided with a plurality of optical filters, one of which is a polarizing filter, and The second filter switching means is characterized in that any one of the plurality of optical filters can be inserted into the optical path.

Other objects and features of the invention are explained in the following embodiments.

According to the present invention, an optical filter unit is provided that includes both an ND filter and a polarizing filter that can be inserted into and removed from an optical path without increasing the size and complexity of the device.

FIG. 3 is a perspective view showing the imaging device before and after an interchangeable lens is attached. FIG. 3 is an exploded perspective view of the image unit. FIG. 3 is an exploded perspective view of the optical filter unit seen from the front and rear. FIG. 3 is a front view of the first filter switching means, showing the relationship between the rotation of the first filter holding frame and the imaging area. FIG. 7 is a front perspective view showing the first filter switching means and the second filter switching means when the non-polarizing filter region is inserted into the photographing region. FIG. 6 is a front perspective view showing the first filter switching means and the second filter switching means when the polarizing filter region is inserted into the photographing region. FIG. 3 is a front view of the optical filter unit 100, showing the relationship between the rotation of the first filter holding frame and the imaging area in a state where the polarizing filter of the second filter switching means is inserted into the optical path. FIG. 7 is a front perspective view showing the first filter switching means and the third filter switching means when the non-polarizing filter region is inserted into the photographing region. FIG. 3 is a front perspective view of the front filter holding frame. FIG. 7 is a front perspective view showing the state of the first filter switching means and the third filter switching means when the polarizing filter region is inserted into the photographing region.

Embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same reference numerals are given to the same members, and duplicate explanations will be omitted.
(First embodiment)
FIG. 1A shows a perspective view of an interchangeable lens type imaging device 10 (hereinafter referred to as an imaging device) according to the present embodiment. FIG. 1(b) shows a perspective view when the interchangeable lens 50 is attached to the imaging device 10. In the following description, the interchangeable lens 50 side will be referred to as the front, and the imaging device 10 side will be referred to as the rear. Further, the vertically upper side of the imaging device 10 is referred to as the upper side, and the vertically lower side of the imaging device 10 is referred to as the lower side. Furthermore, as shown in FIG. 1, three-dimensional coordinates are set. Here, the X, Y, and Z directions correspond to the front-back direction, the left-right direction, and the up-down direction, respectively.

As shown in FIG. 1(a), a mount 11, which is a mounting portion for an interchangeable lens 50, is provided in front of the imaging device 10. A contact portion 14 is provided inside the mount 11 . Furthermore, when the interchangeable lens 50 is attached, the contact portion 14 and a lens-side contact portion (not shown) at the rear end of the interchangeable lens 50 are electrically connected. This allows various types of communication between the interchangeable lens 50 and the imaging device 10.

The light along the optical axis L that is focused by the interchangeable lens 50 shown in FIG. do. In addition, in the mount 11 in this embodiment, the mount ring 12 rotates counterclockwise about the optical axis L when viewed from the front. As a result, the mount claw 13, which rotates in conjunction with the mount ring 12, engages with a claw portion (not shown) at the rear end of the interchangeable lens 50. As a result, the interchangeable lens 50 is drawn toward the image sensor 30 in the optical axis direction and is fixed to the mount 11. However, this embodiment is not limited to this. For example, a known "bayonet type" may be used in which the interchangeable lens 50 is fixed to the mount 11 by rotating the interchangeable lens 50 relative to the imaging device 10 around the optical axis L. The imaging device 10 is also equipped with an image unit 60, which will be described later, in a range from the mount 11 to the image sensor 30.

FIG. 2 shows an exploded perspective view of the image unit 60. As shown in FIG. 2, the image unit 60 includes a mount unit 400, an optical filter unit 100, and a sensor unit 500, which are arranged in this order from the front. Hereinafter, each unit will be explained.

The mount unit 400 mainly includes a mount 11, a glass lid member 19, a cover glass 18, a glass holding member 17, and a front base 15, which are arranged in this order from the front. The cover glass 18 is held between the glass holding member 17 and the glass lid member 19 and is fixed to the front base 15 by fixing screws 20a to 20d. Furthermore, the mount 11, the mount ring 12, and the contact portion 14 are fixed to the front base 15 from the front with screws (not shown). Here, the glass holding member 17 is made of an elastic member such as rubber or elastomer.

The optical filter unit 100 includes a first filter switching means 140 and a second filter switching means 150. The optical filter unit 100 is integrated by a front cover 110, a rear cover 120, and side covers 130a and 130b so as to seal them. The first filter switching means 140 and the second filter switching means 150 each have a plurality of optical members. The first filter switching means 140 can selectively insert each of the plurality of optical members one by one into the optical path of the incident light. The second filter switching means 150 can also selectively insert a plurality of optical members one by one into the optical path of the incident light. Note that the details of each optical member and the method of inserting them into the optical path will be described later. Further, the front cover 110 and the rear cover 120 are provided with an opening H0 and an opening H3 (described in FIG. 3) at positions overlapping with the optical path, respectively. The optical filter unit 100 is fixed to the front base 15 from the front by fixing screws 16a to 16d.

Here, the glass holding member 17 is held in a compressed state by the glass lid member 19, the cover glass 18, and the optical filter unit 100. As a result, the optical filter unit 100 exhibits a dust-proof structure in the front thereof.

The sensor unit 500 includes an image sensor 30, a sensor substrate 31, and a sensor holding plate 33, which are arranged in order from the front. The image sensor 30 mounted on the sensor substrate 31 is adhered to the sensor holding metal plate 33. Thereafter, the sensor unit 500 is fixed to the front base 15 from the rear using the sheet metal fixing screws 34a to 34c. At this time, washers 35a to 35c are arranged at each screw fastening location between the sensor holding metal plate 33 and the front base 15, respectively. In the imaging device 10, by adjusting the thickness and number of washers 35a to 35c, it is possible to adjust the tilt of the imaging surface and the distance from the mount 11 to the imaging surface, that is, the flange back. Furthermore, a sealing member 32 is held between the sensor unit 500 and the optical filter unit 100 in a compressed state in the front-rear direction. Thereby, the optical filter unit 100 exhibits a dust-proof structure at the rear thereof.

As described above, the space between the glass lid member 19 and the optical filter unit 100 and the space between the optical filter unit 100 and the image sensor 30 are each in a sealed state. Therefore, in the image unit 60 in its integrated state, it is possible to prevent dust from entering the inside of the optical filter unit 100 and the imaging surface.

Furthermore, in the integrated state of the image unit 60, the light focused by the interchangeable lens 50 passes through two optical members inserted into the optical path by the first filter switching means 140 and the second filter switching means 150. After that, an image is formed on the image sensor 30.

Next, the optical filter unit 100 will be explained in detail. FIG. 3A is an exploded perspective view of the optical filter unit 100 when viewed from the front. FIG. 3(b) is an exploded perspective view of the optical filter unit 100 when viewed from the rear. Note that side covers 130a and 130b, which are unnecessary for explanation, are not shown in FIG.

The optical filter unit 100 mainly includes a lock unit 170, a front cover 110, a first filter switching means 140, a second filter switching means 150, and a rear cover 120, which are arranged in order from the front.

The first filter holding frame 141 of the first filter switching means 140 and the second filter holding frame 151 of the second filter switching means 150 have substantially the same shape, and both have a disk shape. ing. Furthermore, the first filter holding frame 141 is provided with an opening H1 at its center. The second filter holding frame 151 is provided with an opening H2 at its center. Note that a first shaft 145 and a rotating shaft portion 161, which will be described later, are inserted through the opening H1 and the opening H2, respectively.

A glass member serving as a filter member is fixed to the first filter holding frame 141 and has a substantially fan-shaped polarizing filter area A1 and a non-polarizing filter area A2 centered on a rotation axis O1 parallel to the optical axis L. . The glass member is a filter member manufactured by, for example, sandwiching and bonding a polarizing curtain in the shape of the polarizing filter area A1 between two pieces of glass. The polarizing filter area A1 has a light blocking function of transmitting only light rays of a predetermined polarized light component and blocking other unnecessary light rays. On the other hand, the non-polarizing filter area A2 is an area to which the polarizing curtain is not adhered, and does not have the above-mentioned light shielding function. The polarizing filter area A1 and the non-polarizing filter area A2 are provided on substantially the same plane.

Further, the second filter holding frame 151 of the second filter switching means 150 has three substantially rectangular openings at substantially equal intervals in the circumferential direction on the substantially same plane perpendicular to the optical axis L. is formed. Furthermore, a plurality of optical members (polarizing filter 152, infrared cut filter 153, and transmission filter 154) are fixed so as to seal each opening.

Here, like the polarizing filter area A1, the polarizing filter 152 is an optical member that transmits only light rays of a predetermined polarized light component and blocks other unnecessary light rays. Further, the infrared cut filter 153 is an optical member that absorbs or reflects infrared rays to obtain a photographed image of the same color as that seen by humans. The transmission filter 154 is so-called raw glass and can transmit all light.

As shown in FIG. 3(b), the front cover 110 is provided with a first shaft 145. The first shaft 145 is inserted into the opening H1 with sliding washers 144a and 144b arranged before and after the first filter holding frame 141. Thereby, the first filter holding frame 141 is assembled to the front cover 110. Here, the sliding washers 144a and 144b are, for example, self-lubricating resin washers. Further, the second shaft 160 having a flange portion 162 is fixed to the front cover 110 from the rear (in the negative direction of the X-axis) by a rotation shaft fixing screw 163. The flange portion 162 functions as a retainer to prevent the first filter holding frame 141 from falling off the first shaft 145. As described above, the first filter holding frame 141 is held rotatably about the rotation axis O1 with respect to the front cover 110.

The rotation shaft portion 161 of the second shaft 160 is inserted into the opening H2 of the second filter holding frame 151. Thereby, the second filter holding frame 151 is assembled to the second shaft 160 from the rear. Thereafter, the rear cover 120 is fixed to the front cover 110 with cover fastening screws 121. Therefore, the second filter holding frame 151 is sandwiched between the flange portion 162 and the rear cover 120 with the rotation shaft portion 161 inserted through the opening H2. As described above, the second filter switching means 150, like the first filter switching means 140, is held rotatably about the rotation axis O1.

Further, the flange portion 162 of the second shaft 160 also functions as a partition that separates the first filter holding frame 141 and the second filter holding frame 151. This prevents interference between the first filter holding frame 141 and the second filter holding frame 151, and allows the first filter holding frame 141 and the second filter holding frame 151 to rotate independently and smoothly. It is now possible.

A lock unit 170 is attached to the front cover 110 from the front. The lock unit 170 includes a motor M3 and a lock member 171. The motor M3 is electrically connected to a circuit board by a flexible board (both the flexible board and the circuit board are not shown). In the lock unit 170, it is possible to rotate the lock claws 172a and 172b of the lock member 171 about the lock member rotation axis O3 by transmitting the power of the motor M3 to a transmission mechanism (not shown). . This allows the lock claws 172a and 172b to be switched between a state in which they are engaged with a first outer gear portion G11 and a second outer gear portion G21, which will be described later, and a state in which they are separated. That is, it is possible to fix the first filter holding frame 141 and the second filter holding frame 151 at desired positions.

Next, a mechanism for rotating the first filter holding frame 141 and the second filter holding frame 151 will be explained. A first outer gear portion G11 and a second outer gear portion G21 are formed on the outer peripheries of the first filter holding frame 141 and the second filter holding frame 151, respectively. Furthermore, a first transmission gear G12 and a second transmission gear G22 are provided at positions that mesh with the first outer peripheral gear part G11 and the second outer peripheral gear part G21, respectively. The first transmission gear G12 and the second transmission gear G22 are press-fitted into shafts of the motor M1 and the motor M2, respectively, which are fixed to the front cover 110. The motor M1 and the motor M2, like the motor M3, are electrically connected to a circuit board by a flexible board (both the flexible board and the circuit board are not shown). Therefore, the first filter holding frame 141 can be rotated by the power of the motor M1 via the first transmission gear G12. Similarly, the second filter holding frame 151 can be rotated by the motor M2 via the second transmission gear G22.

As described above, in the optical filter unit 100, different powers (power from the motor M1 and power from the motor M2) are provided to rotate the first filter holding frame 141 and the second filter holding frame 151. It is being Therefore, in the optical filter unit 100, the first filter holding frame 141 and the second filter holding frame 151 can be electrically rotated independently. Furthermore, by using a motor as a power source for each, even when the user is away from the camera, it is possible to change the insertion/removal state of the optical filter by remote control.

Next, a method of switching the optical filters inserted into the optical path by the first filter switching means 140 and the second filter switching means 150 will be described.

The first filter switching means 140 rotates the first filter holding frame 141 about the rotation axis O1. This makes it possible to switch between the polarizing filter area A1 and the non-polarizing filter area A2, which are inserted into the optical path that overlaps the opening H0 and the opening H3 in front view. Furthermore, when the polarizing filter area A1 is inserted in the optical path, by finely adjusting the rotation angle of the first filter holding frame 141, the polarization angle of the polarizing filter area A1 in the optical path can be adjusted continuously and arbitrarily. It is possible to change it (described later using FIG. 4). By configuring the first filter switching means 140 as described above, it is possible to insert and remove the polarizing filter (polarizing filter area A1) into and out of the optical path and adjust the polarization angle using a common mechanism. Therefore, the apparatus can be simplified and downsized compared to the case where the polarizing filter insertion/extraction mechanism and the polarization angle adjustment mechanism are provided separately.

The second filter switching means 150 selectively switches any one of the plurality of optical members provided on the second filter holding frame 151 to the optical path by rotating the second filter holding frame 151. It is possible to insert it inside. Note that the optical members in this embodiment are a polarizing filter 152, an infrared cut filter 153, and a transmission filter 154.

In the optical path, either the polarizing filter area A1 or the non-polarizing filter area A2 of the first filter switching means 140 and any one of the plurality of optical members of the second filter switching means 150 are always inserted. becomes. For example, in FIGS. 3A and 3B, the non-polarizing filter area A2 and the transmission filter 154 are arranged in an overlapping manner in the optical path from the front. Note that, as described above, the first filter holding frame 141 and the second filter holding frame 151 can be rotated independently. Therefore, by combining the switching of the optical filter by the first filter switching means 140 and the switching of the optical filter by the second filter switching means 150, it becomes possible to take pictures according to the shooting situation.

Note that after the desired optical member is inserted into the optical path by the first filter switching means 140 and the second filter switching means 150, the lock unit 170 switches the first filter holding frame 141 and the second filter holding frame. 151 can be fixed at the same time. Therefore, even when an unexpected shock or the like is applied to the imaging device 10, the position of the optical member inserted into the optical path is maintained.

Next, the rotating operation of the first filter holding frame 141 of the first filter switching means 140 will be described in detail. 4(a) to 4(f) show front views of the first filter switching means 140 when the first filter holding frame 141 is sequentially moved. The incident light collected by the interchangeable lens 50 shown in FIG. 1(b) passes through the photographing area A0, and is eventually imaged on the image sensor 30.

First, when the rotation angle of the first filter holding frame 141 is the angle shown in FIG. 4(a), the non-polarizing filter area A2 overlaps the entire imaging area A0. At this time, the incident light passes only through the non-polarizing filter area A2 in the first filter switching means 140.

Next, when the first filter holding frame 141 is rotated in the CCW direction in the figure from the state shown in FIG. The filter area A1 completely overlaps the imaging area A0 (FIG. 4(b)). That is, the polarizing filter area A1 is inserted into the optical path. At this time, the incident light passes only through the polarizing filter area A1 in the first filter switching means 140. Note that the polarization angle of the polarization filter area A1 at this time is parallel to the Y axis. Therefore, in this case, it is possible to transmit only the light parallel to the Y-axis among the incident light.

Thereafter, by sequentially moving the first filter holding frame 141 in the CCW direction, it is possible to continuously change the polarization angle of the polarizing filter area A1 as shown in FIGS. 4(c) to 4(f). It has become. Note that the polarization angle of the polarizing filter area A1 in FIG. 4(f) is parallel to the Y axis, and is optically equivalent to the case in FIG. 4(b). That is, the polarizing filter region A1 in this embodiment can be inserted into and removed from the optical path, and its polarization angle can be continuously and arbitrarily changed from 0 degrees or more to 180 degrees or less.

Note that although an example of rotation in the CCW direction has been shown above, it goes without saying that the same effect can be obtained even if the rotation is in the opposite direction. Further, in the present embodiment, the polarizing filter area A1 and the non-polarizing filter area A2 have substantially fan-shaped shapes, but the shapes of the polarizing filter area A1 and the non-polarizing filter area A2 are not limited to this. For example, for a circular glass member, a half-moon-shaped area larger than the imaging area A0 may be used as a non-polarizing part, and the other area may be used as a polarizing part.

Next, a description will be given of the difference in the imaging mode depending on the combination of optical filters respectively included in the first filter switching means 140 and the second filter switching means 150 inserted into the optical path. As mentioned above, in the optical filter unit 100, by rotating the first filter holding frame 141 of the first filter switching means 140, either the non-polarizing filter area A2 or the polarizing filter area A1 can be placed in the optical path. Insertable.

First, the state in which the non-polarizing filter region A2 is inserted into the optical path will be explained using FIGS. 5(a) and 5(b). FIG. 5 is a front perspective view showing the first filter switching means 140 and the second filter switching means 150 when the non-polarizing filter area A2 is inserted into the imaging area A0. Here, the difference between FIG. 5(a) and FIG. 5(b) is the difference in the optical member inserted into the optical path by the second filter switching means 150. In FIG. 5(a), a transmission filter 154 is inserted into the optical path, and in FIG. 5(b), an infrared cut filter 153 is inserted into the optical path.

FIG. 5A shows the states of the first filter switching means 140 and the second filter switching means 150 when the non-polarizing filter region A2 and the transmission filter 154 are inserted into the optical path. The light beam incident from the front passes through the non-polarizing filter area A2 in the imaging area A0, passes through the transmission filter 154, and forms an image on the image sensor 30 (not shown). Here, both the non-polarizing filter area A2 and the transmission filter 154 transmit all of the incident light. That is, infrared photography that can guide a larger amount of light to the image sensor 30 is possible. This photographing mode is suitable under conditions such as nighttime when a sufficient amount of light cannot be obtained around the subject.

FIG. 5B shows a state in which the infrared cut filter 153 is inserted into the optical path by rotating the second filter holding frame 151 in the CW direction from the state shown in FIG. 5A. At this time, the incident light passes through the non-polarizing filter area A2, passes through the infrared cut filter 153, and forms an image on the image sensor 30. Therefore, in this state, infrared cut photography is possible. In this photography mode, it is possible to image only visible light, so it is possible to obtain a photographed image with the same color as that seen by humans.

Next, the first filter switching means 140 and the second filter switching means 150 in a state where the polarizing filter region A1 is inserted into the optical path will be explained using FIGS. 6(a) and 6(b). FIG. 6 is a front perspective view showing the first filter switching means 140 and the second filter switching means 150 when the polarizing filter area A1 is inserted into the imaging area A0. The difference between FIGS. 6A and 6B is the optical member inserted into the optical path by the second filter switching means 150. In FIG. 6(a), an infrared cut filter 153 is inserted into the optical path, and in FIG. 6(b), a polarizing filter 152 is inserted into the optical path.

FIG. 6A shows the states of the first filter switching means 140 and the second filter switching means 150 when the polarizing filter region A1 and the infrared cut filter 153 are inserted into the optical path. In the state shown in FIG. 6A, light incident from the front passes through the polarizing filter area A1, passes through the infrared cut filter 153, and forms an image on the image sensor 30. The polarizing filter area A1 transmits only light having a predetermined polarization angle among the incident light. Therefore, in this photography mode, it is possible to perform polarized photography in which infrared rays contained in incident light are removed and unnecessary light such as reflected light is blocked. That is, it is possible to remove reflected light caused by strong light such as sunlight reflecting off window glass, water surfaces, etc., thereby improving the quality of captured images. As described above, by rotating the first filter holding frame 141 in the CW direction or the CCW direction, the user can continuously and arbitrarily change the polarization angle of the polarizing filter area A1 in the optical path. It is. Therefore, the user can adjust the polarization angle of the polarization filter area A1 to obtain the optimum polarization angle for reducing reflected light.

Note that among the optical filters included in the second filter switching means 150, the infrared cut filter 153 is inserted into the optical path, but a transmission filter 154 is inserted instead. It is also possible. In that case, the incident light passes through the polarizing filter area A1, passes through the transmission filter 154, and forms an image on the image sensor 30. Therefore, unnecessary light having a specific polarization component contained in the incident light is cut, while infrared rays are transmitted. As a result, unnecessary light such as reflected light can be removed without reducing the amount of incident light guided to the image sensor 30 as much as possible.

Next, FIG. 6(b) shows the states of the first filter switching means 140 and the second filter switching means 150 when the polarizing filter region A1 and the polarizing filter 152 are inserted into the optical path. In the state shown in FIG. 6B, the incident light passes through the polarizing filter area A1, passes through the polarizing filter 152, and forms an image on the image sensor 30. Generally, two polarizing filters having a predetermined polarization angle are stacked on the optical path and function as a variable ND filter whose light attenuation rate can be continuously changed by rotating one of the polarizing filters. It is known that In the optical filter unit 100 in the state shown in FIG. 6(b), while the polarization angle of the polarization filter 152 is fixed, it is possible to rotate the first filter holding frame 141 to adjust the polarization angle of the polarization filter area A1. It is possible. This makes it possible to obtain the effect of a variable ND filter. That is, by rotating the first filter holding frame 141, it is possible to perform light reduction photography in which the light reduction rate can be adjusted.

Here, a method for adjusting the light attenuation rate will be described in detail using FIGS. 7(a) to 7(f). FIGS. 7(a) to 7(f) show optical properties when the first filter holding frame 141 is sequentially moved in a state in which the polarizing filter 152 of the second filter switching means 150 is inserted into the optical path. 1 is a front view of a filter unit 100. FIG. For simplicity, regarding the polarizing filter 152 in FIG. 7, only the area within the imaging area A0 is shown by a broken line.

First, when the rotation angle of the first filter holding frame 141 is as shown in FIG. ing. That is, in this state, the polarizing filter area A1 and the polarizing filter 152 do not overlap within the photographing area A0. Therefore, in this state, the function of the variable ND filter cannot be obtained, and only the effect of the polarizing filter 152 in transmitting light having a predetermined polarization angle is obtained.

When the first filter holding frame 141 is rotated in the CCW direction in the figure from the state shown in FIG. 7(a), the polarizing filter area A1 gradually begins to overlap the photographing area A0, and completely overlaps the imaging area A0 (the state shown in FIG. 7(b)). That is, the polarizing filter area A1 and the polarizing filter 152 are arranged in series within the optical path. Therefore, both function as a variable ND filter that can continuously change the light attenuation rate by changing the polarization angle of the polarization filter area A1. Note that in FIG. 7B, the polarization angle of the polarization filter area A1 and the polarization angle of the polarization filter 152 are equal to each other. Therefore, the state shown in FIG. 7(b) represents a state where the light attenuation rate is the smallest (bright) in the function of the variable ND filter.

Thereafter, by further rotating the first filter holding frame 141 in the CCW direction, the light attenuation rate becomes larger (darker) continuously, resulting in the state shown in FIG. 7(c) (FIG. 6(b) ). When the first filter holding frame 141 is further rotated, the state shown in FIG. 7(d) will be reached. At this time, the polarization angle of the polarization filter area A1 and the polarization angle of the polarization filter 152 are perpendicular to each other. Therefore, the state shown in FIG. 7(d) is a state in which the light attenuation rate is the highest (dark) in the function of the variable ND filter.

Thereafter, by further rotating the first filter holding frame 141 in the CCW direction, the light attenuation rate gradually becomes smaller (brighter), and the state shown in FIG. 7(e) is reached, and then the state shown in FIG. 7(f) is reached. The state will be as follows. In the state of FIG. 7(f), the polarization angle of the polarizing filter area A1 and the polarization angle of the polarizing filter 152 are equal to each other, and at this time, the light attenuation rate is equivalent to the state of FIG. 7(b). .

As described above, with the polarizing filter 152 inserted into the optical path, the user can adjust the polarization angle of the polarizing filter area A1 and set the optimum light attenuation rate according to the shooting situation. This makes it possible to prevent deterioration of photographed image quality due to overexposure and the like.

Note that the polarizing filter 152 may be configured to have an infrared cut function in addition to a function of transmitting only light beams of a predetermined polarized light component. For example, by sandwiching a polarizing curtain between an infrared cut glass and base glass and then bonding the two glasses together, it is possible to provide an infrared cut function in addition to the function of transmitting only light of a predetermined polarized component. is possible. With this configuration, in the state shown in FIG. 6(b), the function of the variable ND filter can achieve both the function of attenuating the incident light and the function of blocking the infrared rays contained in the incident light. It becomes possible.

As explained above, according to the optical filter unit 100 of the present embodiment, in addition to inserting and removing a polarizing filter and adjusting the polarization angle, the same mechanism realizes insertion and removal of a variable ND filter and adjustment of its light attenuation rate. be able to. Therefore, according to the present embodiment, it is possible to provide an optical filter unit 100 that includes both an ND filter and a polarizing filter that can be inserted into and removed from the optical path, and an imaging device that includes the same, without increasing the size and complexity of the device. It is possible.
(Second embodiment)
In the first embodiment, in the second filter switching means 150, as a structure for inserting each optical member into the optical path, the optical member is switched by rotating a substantially circular filter holding frame (a so-called filter turret). method). In this embodiment, as another method of the switching means, a method is shown in which the optical members inserted into the optical path are switched by sliding a plurality of filter holding frames in a direction orthogonal to the optical axis L, respectively.

The difference between this embodiment and the first embodiment is that the second filter switching means 150 in the optical filter unit 100 is replaced by the third filter switching means 300. Hereinafter, differences in imaging modes depending on the combination of optical filters respectively included in the first filter switching means 140 and the third filter switching means 300 inserted into the optical path will be explained.

First, the state in which the non-polarizing filter region A2 is inserted into the optical path will be explained using FIG. 8. Note that the same components as in the first embodiment are given the same reference numerals, and their description will be omitted. FIG. 8 is a front perspective view showing the first filter switching means 140 and the third filter switching means 300 when the non-polarizing filter area A2 is inserted into the imaging area A0. As shown in FIG. 8, a third filter switching means 300 is arranged behind the first filter switching means 140.

The third filter switching means 300 includes a front filter holding frame 310 and a rear filter holding frame 320, each of which is movable independently in a direction perpendicular to the optical axis L (Z direction in this embodiment). There is. Further, a polarizing filter 311 and an infrared cut filter 321 are fixed to the front filter holding frame 310 and the rear filter holding frame 320, respectively. The optical functions of both filters are similar to the polarizing filter 152 and the infrared cut filter 153 shown in the first embodiment. In the third filter switching means 300, when one of the filters is inserted into the optical path, the other filter is retracted out of the optical path. The holding metal plates 301a and 301b are each attached to a not-shown rear cover (corresponding to the rear cover 120 in the first embodiment). Further, a front guide shaft 303a and a rear guide shaft 304b are each fixed to the cover. Further, a rear guide shaft 304a and a front guide shaft 303b are fixed to the holding metal plates 301a and 301b, respectively.

Furthermore, a motor M31 and a motor M32 are attached to the holding metal plates 301a and 301b, respectively. Further, lead screws 302a and 302b are rotatably provided on the motor shafts of the motor M31 and the motor M32, respectively.

Next, a method of holding the front filter holding frame 310 in the third filter switching means 300 and a method of inserting the optical member into the optical path will be explained. Note that the structure of the rear filter holding frame 320 is substantially the same as that of the front filter holding frame 310, and the holding method and the method of inserting the optical member into the optical path are also the same, so a description thereof will be omitted.

FIG. 9 shows a perspective view of the front filter holding frame 310 viewed from the front. The front filter holding frame 310 has arm portions 312a and 312b extending in the negative direction and the positive direction of the Y-axis, respectively. The arm portions 312a and 312b are provided with holes and slits through which the front guide shafts 303a and 303b shown in FIG. 8 can be inserted, respectively. Furthermore, a nut holder 313 extends from the tip of the arm 312a, into which a nut 314 is inserted.

As shown in FIG. 8, in the front filter holding frame 310, the two holes of the arm 312a and the slit of the arm 312b are inserted into the front guide shafts 303a and 303b, respectively. Furthermore, the nut 314 inserted and held by the nut holding portion 313 is in a state of meshing with the lead screw 302a. As described above, the front filter holding frame 310 is held by the front guide shafts 303a, 303b and the lead screw 302a. Furthermore, since the nut 314 and the lead screw 302a are engaged, the front filter holding frame 310 can be moved in the Z direction by rotating the lead screw 302a with the motor M31. Therefore, it is possible to insert and remove the polarizing filter 311 into the optical path. Note that the infrared cut filter 321 can be similarly inserted into and removed from the optical path by rotating the lead screw 302b using the motor M32.

In the state shown in FIG. 8, the non-polarizing filter area A2 and the infrared cut filter 321 are arranged in an overlapping manner on the optical path. Therefore, the light incident from the front of the imaging device 10 passes through the non-polarizing filter area A2, passes through the infrared cut filter 321, and is imaged by the imaging device 30. Therefore, in this photography mode, it is possible to obtain a photographed image with the same color as that seen by humans. In other words, it is possible to carry out photography similar to the infrared cut photography shown in FIG. 5(b).

Next, using FIGS. 10(a) and 10(b), in the optical filter unit 100 of this embodiment, when the polarizing filter area A1 of the first filter switching means 140 is inserted into the optical path, Explain the condition. FIG. 10 is a front perspective view showing the first filter switching means 140 and the third filter switching means 300 when the polarizing filter area A1 is inserted into the imaging area A0. The difference between FIGS. 10(a) and 10(b) is the optical member inserted into the optical path by the third filter switching means 300. In FIG. 10(a), an infrared cut filter 321 is inserted into the optical path, and in FIG. 10(b), a polarizing filter 311 is inserted into the optical path.

FIG. 10A shows a state when the infrared cut filter 321 of the third filter switching means 300 is inserted into the optical path. On the optical path, a polarizing filter area A1 and an infrared cut filter 321 are arranged in an overlapping manner. The light incident from the front passes through the polarizing filter area A1, passes through the infrared cut filter 321, and forms an image on the image sensor 30 (not shown). The polarizing filter area A1 transmits only light having a predetermined polarization angle among the incident light. Note that, as described in the first embodiment, the deflection angle of the polarizing filter area A1 can be changed continuously and arbitrarily by rotating the first filter holding frame 141 about the rotation axis O1. ing. Therefore, the user can adjust the polarizing filter area A1 to obtain the optimum deflection angle according to the shooting situation. This makes it possible to effectively block unnecessary light. Therefore, in this embodiment as well, polarized light photography similar to that shown in FIG. 6(a) can be performed.

Next, FIG. 10(b) shows a state when the polarizing filter 311 included in the third filter switching means 300 is inserted into the optical path. At this time, the polarizing filter area A1 and the polarizing filter 311 are arranged in an overlapping manner on the optical path. As shown in the first embodiment, the polarizing filter area A1 and the polarizing filter 311 overlapped on the optical path function as a variable ND filter. The light incident from the front is attenuated by passing through the polarizing filter area A1 and the polarizing filter 311, and forms an image on the image sensor 30.

Note that, as described in the first embodiment, by rotating the first filter holding frame 141 around the rotation axis O1, it is possible to continuously and arbitrarily change the light attenuation rate of the ND filter. ing. As described above, in this embodiment as well, it is possible to perform dimming photography similar to that shown in FIG. 6(b).

In the present embodiment, a case has been described in which, in the third filter switching means 300, when one of the filters is in a position inserted into the optical path, the other filter is in a state of being retracted out of the optical path. However, this embodiment is not limited to this. When one filter is inserted into the optical path, the other filter may also be inserted into the optical path.

For example, in the third filter switching means 300, if both the polarizing filter 311 and the infrared cut filter 321 are inserted into the optical path, in addition to the function of the polarizing filter 311 that transmits only the light of a predetermined polarized component, the infrared cut filter Functions can be added. With this configuration, the function of the variable ND filter enables both the function of attenuating incident light and the function of blocking infrared rays contained in the incident light.

Although the preferred embodiments of the present invention have been described above, the configuration of the present invention is not limited to those exemplified in each of the above embodiments, and the material, shape, size, form, number, arrangement location, etc. Appropriate changes can be made without departing from the gist of the present invention.

For example, in the first and second embodiments, the optical filter unit 100 is built into the imaging device 10, but the present invention is not limited thereto. The optical filter unit 100 may be provided in an optical device such as an interchangeable lens 50 or an adapter. For example, the optical filter unit 100 may be provided within an accessory such as an adapter inserted between the interchangeable lens 50 and the imaging device 10, within the interchangeable lens 50, or in front of the interchangeable lens 50. Incidentally, the size of the luminous flux of light condensed by the lens becomes smaller as it approaches the image sensor 30. Therefore, from the viewpoint of downsizing the device, it is desirable that the optical filter unit 100 be built in between the interchangeable lens 50 and the image sensor 30.

Further, although a configuration in which a motor is used as a method for switching each optical filter in the first filter switching means 140, the second filter switching means 150, and the third filter switching means 300 has been shown, it is possible to use a motor by hand. A manual method may also be used.

Further, although the first filter switching means 140 is arranged in front of the second filter switching means 150 or the third filter switching means 300, the arrangement may be reversed.

Moreover, the optical filters provided in each of the second filter switching means 150 and the third filter switching means 300 may be one polarizing filter and one other optical filter. That is, it is sufficient that one or more optical filters are provided in addition to one polarizing filter, and the types of these optical filters are not limited to specific ones.

The disclosure of each of the above embodiments includes the following configurations and methods.

(Configuration 1)
An optical filter unit comprising a first filter switching means and a second filter switching means arranged in series along an axial direction parallel to the optical axis,
The first filter switching means is provided with a polarizing filter area and a non-polarizing filter area,
The first filter switching means can insert either the polarizing filter region or the non-polarizing filter region into the optical path by rotating around a rotation axis parallel to the optical axis,
The second filter switching means is provided with a plurality of optical filters, one of which is a polarizing filter,
The optical filter unit is characterized in that the second filter switching means is capable of inserting any one of the plurality of optical filters into the optical path.
(Configuration 2)
The optical filter unit according to configuration 1, wherein the polarizing filter area and the non-polarizing filter area are provided on substantially the same plane.
(Configuration 3)
The first filter switching means has a filter holding frame that holds a filter member provided with the polarizing filter area and the non-polarizing filter area,
By rotating the filter holding frame around the rotation axis, the first filter switching means can insert either the polarizing filter region or the non-polarizing filter region into the optical path. The optical filter unit according to configuration 1 or 2.
(Configuration 4)
In the second filter switching means, when the polarizing filter is in a position retracted from the optical path,
The first filter switching means can continuously change the polarization angle of the polarizing filter region with respect to the optical path by rotating the polarizing filter region around the rotation axis while the polarizing filter region is inserted into the optical path. The optical filter unit according to any one of configurations 1 to 3, characterized in that:
(Configuration 5)
4. The optical filter unit according to configuration 4, wherein the first filter switching means is capable of continuously and arbitrarily changing the polarization angle from 0 degrees or more to 180 degrees or less.
(Configuration 6)
6. The optical filter unit according to any one of configurations 1 to 5, wherein the shape of the polarizing filter region and the shape of the non-polarizing filter region are substantially fan-shaped.
(Configuration 7)
In the second filter switching means, when the polarizing filter is in an inserted position with respect to the optical path,
The first filter switching means can continuously change the attenuation rate of light passing through the optical path by rotating the polarizing filter region around the rotation axis while inserting the polarizing filter region into the optical path. 7. The optical filter unit according to any one of configurations 1 to 6, characterized in that:
(Configuration 8)
8. The optical filter unit according to any one of configurations 1 to 7, wherein the plurality of optical filters include at least one of an infrared cut filter and plain glass in addition to the polarizing filter.
(Configuration 9)
The second filter switching means is a disc-shaped turret in which the plurality of optical filters are arranged in a circumferential direction,
Any one of configurations 1 to 8, wherein the second filter switching means is capable of inserting any one of the plurality of optical filters into the optical path by rotating around the rotation axis. The optical filter unit described in the above.
(Configuration 10)
The second filter switching means includes a plurality of filter holding frames each movable independently in a direction perpendicular to the optical axis,
Each of the plurality of filter holding frames is provided with one of the plurality of optical filters,
By moving the plurality of filter holding frames in a direction perpendicular to the optical axis, the second filter switching means can insert any one of the plurality of optical filters into the optical path. 9. The optical filter unit according to any one of features 1 to 8.
(Configuration 11)
An optical filter unit comprising a first filter switching means and a second filter switching means arranged in series along an axial direction parallel to the optical axis,
The first filter switching means is provided with a polarizing filter area and a non-polarizing filter area,
The first filter switching means can insert either the polarizing filter region or the non-polarizing filter region into the optical path by rotating around a rotation axis parallel to the optical axis,
The second filter switching means is provided with a plurality of optical filters, one of which is a polarizing filter,
The second filter switching means includes a plurality of filter holding frames, each of which is movable independently in a direction perpendicular to the optical axis,
Each of the plurality of filter holding frames is provided with one of the plurality of optical filters,
The second filter switching means is capable of inserting at least one of the plurality of optical filters into the optical path by moving the plurality of filter holding frames in a direction perpendicular to the optical axis. An optical filter unit featuring:
(Configuration 12)
An imaging device comprising an imaging element and an optical filter unit according to any one of Configurations 1 to 11.
(Configuration 13)
An optical device comprising the optical filter unit according to any one of Structures 1 to 11.

100 Optical filter unit 140 First filter switching means 150 Second filter switching means A1 Polarizing filter area A2 Non-polarizing filter area 152 Polarizing filter 153 Infrared cut filter 154 Transmission filter

Claims (13)

An optical filter unit comprising a first filter switching means and a second filter switching means arranged in series along an axial direction parallel to the optical axis,
The first filter switching means is provided with a polarizing filter area and a non-polarizing filter area,
The first filter switching means can insert either the polarizing filter region or the non-polarizing filter region into the optical path by rotating around a rotation axis parallel to the optical axis,
The second filter switching means is provided with a plurality of optical filters, one of which is a polarizing filter,
The optical filter unit is characterized in that the second filter switching means is capable of inserting any one of the plurality of optical filters into the optical path. The optical filter unit according to claim 1, wherein the polarizing filter area and the non-polarizing filter area are provided on substantially the same plane. The first filter switching means has a filter holding frame that holds a filter member provided with the polarizing filter area and the non-polarizing filter area,
By rotating the filter holding frame around the rotation axis, the first filter switching means can insert either the polarizing filter region or the non-polarizing filter region into the optical path. The optical filter unit according to claim 1. In the second filter switching means, when the polarizing filter is in a position retracted from the optical path,
The first filter switching means can continuously change the polarization angle of the polarizing filter region with respect to the optical path by rotating the polarizing filter region around the rotation axis while the polarizing filter region is inserted into the optical path. The optical filter unit according to claim 1, characterized in that: 5. The optical filter unit according to claim 4, wherein the first filter switching means is capable of continuously and arbitrarily changing the polarization angle from 0 degrees or more to 180 degrees or less. The optical filter unit according to claim 1, wherein the shape of the polarizing filter region and the shape of the non-polarizing filter region are substantially fan-shaped. In the second filter switching means, when the polarizing filter is in an inserted position with respect to the optical path,
The first filter switching means can continuously change the attenuation rate of light passing through the optical path by rotating the polarizing filter region around the rotation axis while inserting the polarizing filter region into the optical path. The optical filter unit according to claim 1, characterized in that: The optical filter unit according to claim 1, wherein the plurality of optical filters include at least one of an infrared cut filter and plain glass in addition to the polarizing filter. The second filter switching means is a disc-shaped turret in which the plurality of optical filters are arranged in a circumferential direction,
2. The second filter switching means is capable of inserting any one of the plurality of optical filters into the optical path by rotating around the rotation axis. optical filter unit. The second filter switching means includes a plurality of filter holding frames each movable independently in a direction perpendicular to the optical axis,
Each of the plurality of filter holding frames is provided with one of the plurality of optical filters,
By moving the plurality of filter holding frames in a direction perpendicular to the optical axis, the second filter switching means can insert any one of the plurality of optical filters into the optical path. The optical filter unit according to claim 1. An optical filter unit comprising a first filter switching means and a second filter switching means arranged in series along an axial direction parallel to the optical axis,
The first filter switching means is provided with a polarizing filter area and a non-polarizing filter area,
The first filter switching means can insert either the polarizing filter region or the non-polarizing filter region into the optical path by rotating around a rotation axis parallel to the optical axis,
The second filter switching means is provided with a plurality of optical filters, one of which is a polarizing filter,
The second filter switching means includes a plurality of filter holding frames, each of which is movable independently in a direction perpendicular to the optical axis,
Each of the plurality of filter holding frames is provided with one of the plurality of optical filters,
The second filter switching means is capable of inserting at least one of the plurality of optical filters into the optical path by moving the plurality of filter holding frames in a direction perpendicular to the optical axis. An optical filter unit featuring: An imaging device comprising an imaging element and the optical filter unit according to claim 1. An optical device comprising the optical filter unit according to claim 1.