JP2011077627A - Imaging unit and image capturing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the need for a complicated operation to attach or detach an optical low pass filter. <P>SOLUTION: An imaging unit 10 includes: an image sensor 101; a low pass filter 102 that is arranged before the image sensor 101 and has a pair of birefringent optical element 102FWD and 102AFT; a motor 103a that relatively rotates the pair of birefringent optical element 102FWD and 102AFT; and a drive means 103 that is composed of a base 103b and transmission unit 103c. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging unit and an imaging apparatus.

  Conventionally, a digital camera in which an optical low-pass filter is detachable is known (for example, Patent Document 1).

JP 2006-171149 A

  However, there is a problem that a complicated operation for attaching and detaching the optical low-pass filter is required and dust or the like adheres to the optical member.

  An imaging unit according to a first aspect of the present invention includes an imaging device, a low-pass filter member disposed in front of the imaging device and including a pair of birefringent optical members, and a drive for relatively rotating the pair of birefringent optical members. Means.

  According to the present invention, the optical characteristics of the low-pass filter member can be switched by relatively rotating the pair of birefringent optical members.

The figure explaining the principal part structure of the digital camera of this Embodiment The figure explaining the structure of the imaging unit of 1st Embodiment The figure explaining the optical characteristic of the optical low-pass filter in 1st Embodiment The figure explaining the structure of the imaging unit of 2nd Embodiment The figure explaining the optical characteristic of the optical low-pass filter in 3rd Embodiment

-First embodiment-
A camera according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a main configuration of the electronic camera 100. An interchangeable lens 200 including a photographing lens L1 is detachably attached to the body 10 of the electronic camera 100. On the body side of the electronic camera 100, an image pickup unit 110 having an image pickup element 101, an optical low-pass filter 102, and a drive unit 103, an operation member 109, and a control circuit 111 are provided. In addition, illustration and description are omitted for general devices and apparatuses of cameras other than the devices and apparatuses related to the present invention.

  The image sensor 101 has a two-dimensional array of photoelectric conversion elements such as a CCD and a CMOS that convert subject light received via the photographing lens L1 into an image signal corresponding to the intensity thereof. An optical low-pass filter 102 is provided on the entire surface (subject side) of the image sensor 101 to remove light with high spatial frequency from subject light. The optical low-pass filter 102 includes a pair of optical members having birefringence. The pair of optical members of the optical low-pass filter 102 is driven by the drive unit 103 according to a control signal from the control circuit 111 according to the operation of the operation member 109 by the user. The optical low-pass filter 102 is a variable optical low-pass filter that can generate different optical characteristics (optical low-pass filter characteristics). Details of the optical low-pass filter 102 will be described later.

  The operation member 109 is operated by the user to switch the characteristic of the optical low-pass filter 102 between the first mode and the second mode. The operation member 109 outputs an operation signal indicating whether the first mode or the second mode is set to the control circuit 111 according to a user operation. The first mode is a mode in which the optical low-pass filter 102 functions as an optical low-pass filter, and the second mode is a mode in which the optical low-pass filter 102 does not function as an optical low-pass filter.

  The drive unit 103 is configured by, for example, a stepping motor, and a pair of birefringent optical members configuring the optical low-pass filter 102 based on a drive signal output from the control circuit 111 in response to an operation of the operation member 109 by the user. Rotate relative. Details of the drive unit 103 will be described later. The control circuit 111 includes a CPU, a ROM, a RAM, and the like (not shown), and is an arithmetic circuit that controls each component of the electronic camera 100 and executes various data processing. The control circuit 111 performs image processing such as interpolation processing, color conversion processing, and white balance processing on the image signal input from the image sensor 101 to generate image data (RAW data). Further, the control circuit 111 outputs a drive signal (pulse signal) to the drive unit 103 based on the operation signal input from the operation member 109.

  Next, details of the optical low-pass filter 102 and the drive unit 103 will be described. As shown in the configuration diagram of FIG. 2, the optical low-pass filter 102 is provided on the optical path of subject light from the photographing lens L <b> 1 to the image sensor 101, and guides the subject light incident from the photographing lens L <b> 1 to the image sensor 101. In FIG. 2, the description will be made assuming that the optical axis direction of the taking lens L1 is the z-axis and the plane substantially perpendicular to the z-axis is the xy plane. The optical low-pass filter 102 includes a pair of front filter 102FWD and rear filter 102AFT. The front filter 102FWD has a birefringence characteristic, and the rear filter 102AFT has a similar birefringence characteristic on the imaging lens L1 side in the optical path of the subject light, and is arranged on the imaging element 101 side. The rear filter 102AFT is provided on a base member 103b that constitutes a drive unit 103 described later. The rear filter 102AFT is rotationally driven on a plane substantially perpendicular to the optical axis of the photographic lens L1 (on the xy plane in FIG. 2) in conjunction with the rotational driving of the base member 103b.

  The front filter 102FWD and the rear filter 102AFT are made of the same material (for example, crystal or lithium niobate) and are formed as thin plates having a cut surface in a predetermined direction with respect to the crystal axis. Therefore, the front filter 102FWD and the rear filter 102AFT separate the subject light incident from the photographing lens L1 through the above-described cut surface into an ordinary ray and an extraordinary ray having different polarization states, and send them to the image sensor 101. Lead. 2 shows a case where the cut surfaces of the front filter 102FWD and the rear filter 102AFT are formed in a rectangular shape having substantially the same size as that of the image sensor 101, the front filter 102FWD and the rear filter Each cut surface of the filter 102AFT is not limited to the shape shown in FIG.

  The drive unit 103 includes a motor 103a, a base 103b, and a transmission unit 103c. The motor 103a is driven in accordance with a drive signal from the control circuit 111. The base 103b is, for example, a disk-shaped plate material provided with the above-described rear filter 102AFT. An opening is provided in the central portion of the base 103b in a shape that substantially matches the rectangular shape of the rear filter 102AFT. Then, the rear filter 102AFT is joined so as to be embedded in the opening. The transmission part 103c is a disk-shaped board | plate material, and transmits the rotational drive of the motor 103a to the base 103b. For example, a gear or the like is formed along each circumference so that the base 103b and the transmission portion 103c can be engaged with each other on the circumferential side surface. As a result, when the transmission unit 103c rotates in accordance with the rotational drive of the motor 103a, the base 103b is rotationally driven in conjunction.

  In the present embodiment, the center of the base 103b and the center of the rear filter 102AFT are formed to substantially coincide. That is, when the motor 103a is rotationally driven, the rear filter 102AFT is rotationally driven on a plane (xy plane) orthogonal to the z axis with the optical axis (z axis) of the photographing lens L1 as the center. In other words, the motor 103a rotates the rear filter 102AFT so that the crystal axis direction of the front filter 102FWD and the crystal axis direction of the rear filter 102AFT are relatively two different directions. Note that the driving unit 103 may rotate the front filter 102FWD instead of rotating the rear filter 102AFT.

  FIG. 3 shows a cross section of the front filter 102FWD, the rear filter 102AFT, and the image sensor 101. 3 is a cross-sectional view in a plane parallel to the yz plane of FIG. 2 including the optical axis of the photographic lens L1. In FIG. 3, t represents the thickness of the optical low-pass filter 102, and d represents the amount of separation between ordinary light and extraordinary light separated by the optical low-pass filter 102. The separation amount d is set so as to be a value that is substantially equal to or slightly smaller than the interval (pixel pitch) p between the pixels constituting the image sensor 101. Further, since the separation amount d is proportional to the thickness t, when the separation amount d is determined, the thickness t is determined.

  As shown in FIG. 3, the length in the z-axis direction (optical axis direction) of the front filter 102FWD and the rear filter 102AFT, that is, the thickness, is both t / 2. Therefore, since the front filter 102FWD and the rear filter 102AFT have the same material and the same thickness t / 2, they have the same birefringence characteristics. Since the front filter 102FWD and the rear filter 102AFT have the same birefringence characteristics, the amount of separation between the ordinary ray and the extraordinary ray by the front filter 102FWD and the rear filter 102AFT is both d / 2. The thickness t / 2 and the separation amount d / 2 described above are determined based on the pixel pitch p of the image sensor 101 as described above. Note that the front filter 102FWD and the rear filter 102AFT may have an interval in the z-axis direction as shown in FIG. 3, or the front filter 102FWD and the rear filter 102AFT are in close contact with each other. More than that.

  FIG. 3A shows the relationship between an ordinary ray and an extraordinary ray when the direction of subject light separation by the front filter 102FWD, that is, the crystal axis direction, and the crystal axis direction of the rear filter 102AFT are substantially matched. That is, the case where the angle between the subject light separation direction by the front filter 102FWD and the subject light separation direction by the rear filter 102AFT is approximately 0 degrees (hereinafter, the shift angle θ = 0 degrees). In FIG. 3A, the crystal axis directions of the front filter 102FWD and the rear filter 102AFT are indicated by arrows AR1 and AR2, respectively. Since the subject light incident from the photographing lens L1 is circularly polarized light, it is separated into linearly polarized ordinary ray L1 and linearly polarized extraordinary ray L2 by the front filter 102FWD, and is emitted toward the rear filter 102AFT. In other words, the subject light travels in the front filter 102FWD in parallel with the z-axis direction and is emitted, and the subject light travels in the front filter 102FWD in parallel with the crystal axis direction (AR1) to be in the z-axis. It is separated into an extraordinary ray L2 emitted in a parallel direction. As described above, the amount of separation between the ordinary ray L1 and the extraordinary ray L2 is d / 2.

  The ordinary ray L1 that has passed through the front filter 102FWD travels in the rear filter 102AFT in a direction parallel to the z-axis, and is emitted to the image sensor 101 as an ordinary ray L1 '. The extraordinary ray L2 that has passed through the front filter 102FWD travels in the rear filter 102AFT in parallel with the crystal axis direction (AR2), and is emitted to the image sensor 101 as extraordinary ray L2 'in a direction parallel to the z axis. The ordinary ray L1 and the extraordinary ray L2 are separated by the separation amount d / 2 and are incident on the rear filter 102AFT. Since the separation amount of the rear filter 102AFT is d / 2, the ordinary ray emitted from the rear filter 102AFT. The amount of separation between L1 ′ and extraordinary ray L2 ′ is d. Therefore, the ordinary ray L1 'and the extraordinary ray L2' are incident on the image sensor 101 with the separation amount d. That is, since the front filter 102FWD and the rear filter 102AFT have the same separation characteristics, the amount separated by the front filter 102FWD is doubled when it is emitted from the rear filter 102AFT. In other words, it has a function equivalent to that of an optical low-pass filter having a thickness t and a separation amount d.

  FIG. 3B shows the relationship between the ordinary ray and the extraordinary ray when the subject light separation direction by the front filter 102FWD and the separation direction of the rear filter 102AFT are almost opposite directions. That is, the case where the angle formed by the subject light separation direction by the front filter 102FWD and the subject light separation direction by the rear filter 102AFT is approximately 180 degrees (hereinafter referred to as a shift angle θ = 180 degrees). The incident circularly polarized subject light from the photographing lens L1 is separated into a linearly polarized ordinary ray L1 and a linearly polarized extraordinary ray L2 by the front filter 102FWD, and is emitted toward the rear filter 102AFT. In other words, the subject light travels in the front filter 102FWD in parallel with the z-axis direction and is emitted, and the subject light travels in the front filter 102FWD in parallel with the crystal axis direction (AR1) to be in the z-axis. It is separated into an extraordinary ray L2 emitted in a parallel direction. As described above, the amount of separation between the ordinary ray L1 and the extraordinary ray L2 is d / 2.

  The ordinary ray L1 that has passed through the front filter 102FWD travels in the rear filter 102AFT in a direction parallel to the z-axis and is emitted. The extraordinary ray L2 transmitted through the front filter 102FWD travels in the rear filter 102AFT in parallel with the crystal axis direction (AR2), and the extraordinary ray L2 is emitted from the same position as the ordinary ray. This is because the crystal axis direction (AR2) of the rear filter 102AFT differs from the crystal axis direction (AR1) of the front filter 102FWD by approximately 180 degrees, and the thicknesses of the front filter 102FWD and the rear filter 102AFT are both This is because it is t / 2. That is, since the birefringence characteristic of the front filter 102FWD and the birefringence characteristic of the rear filter 102AFT are canceled out, the separation amount d / 2 of the extraordinary ray L2 by the front filter 102FWD is canceled out by the separation characteristic of the rear filter 102AFT. . As a result, the circularly polarized subject light incident on the front filter 102FWD is guided to the image sensor 101 without separating extraordinary rays. In other words, it has the same function as when the optical low-pass filter 102 is not provided.

  When the first mode is set by the user and an operation signal is input from the operation member 109, the control circuit 111 outputs a drive signal to the drive unit 103. Then, the rear filter 102AFT is rotationally driven by the drive unit 103, and as shown in FIG. 3A, the separation direction of the front filter 102FWD and the separation direction of the rear filter 102AFT coincide, that is, the shift angle θ = 0 degrees. Become. As a result, in the first mode, it is possible to improve the characteristic of removing light with a high spatial frequency by the optical low-pass filter 102. In addition, when the second mode is set by the user and an operation signal is input from the operation member 109, the control circuit 111 outputs a drive signal to the drive unit 103. The rear filter 102AFT is rotationally driven by the drive unit 103 in the direction opposite to that in the case where the first mode is set. As shown in FIG. 3B, the separation direction of the front filter 102FWD and the separation direction of the rear filter 102AFT are opposite to each other on the xy plane, that is, the shift angle θ = 180 degrees. As a result, in the second mode, the characteristic of removing light having a high spatial frequency by the optical low-pass filter 102 is weakened, and the optical low-pass filter characteristic can be invalidated.

According to the first embodiment described above, the following operational effects can be obtained.
The optical low-pass filter 102 is disposed in front of the image sensor 101 and includes a front filter 102FWD and a rear filter 102AFT that are a pair of birefringent optical members. Then, the drive unit 103 rotates the rear filter 102AFT relative to the front filter 102FWD. Specifically, the optical low-pass filter 102 is disposed in the optical path between the photographing lens L1 and the image sensor 101, and includes a front filter 102FWD having birefringence characteristics and a rear filter 102AFT having birefringence characteristics. It is out. The drive unit 103 is configured to rotate the rear filter 102AFT between two different positions relative to the front filter 102FWD on a plane substantially orthogonal to the optical axis of the photographic lens L1. In other words, the drive unit 103 rotationally drives the rear filter 102AFT so that the shift angle θ is approximately 0 degrees in the first mode and the shift angle θ is approximately 180 degrees in the second mode. In the case of the first mode, the optical low-pass filter 102 validates the optical low-pass filter characteristic based on the birefringence characteristic of the front filter 102FWD and the birefringence characteristic of the rear filter 102AFT. In this case, the birefringence characteristic of the front filter 102FWD and the birefringence characteristic of the rear filter 102AFT are canceled out to invalidate the optical low-pass filter characteristic. Therefore, it is possible to obtain either a state in which the optical low-pass filter characteristic is validated or a state in which the optical low-pass filter characteristic is invalidated without attaching or detaching the optical low-pass filter 102. Furthermore, since the optical low-pass filter characteristic can be invalidated with the optical low-pass filter 102 attached, it is possible to prevent dust and the like from adhering to the image sensor 101 in the electronic camera 100 when the optical low-pass filter 102 is attached or detached. .

-Second Embodiment-
A second embodiment according to the present invention will be described with reference to the drawings. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and different points will be mainly described. Points that are not particularly described are the same as those in the first embodiment. This embodiment is different from the first embodiment in that two optical low-pass filters having a pair of front filters and rear filters are provided.

  FIG. 4 shows the configuration of the imaging unit 110 in the second embodiment. The imaging unit 110 includes a first optical low-pass filter 102_F, a second optical low-pass filter 102_S, a ¼ wavelength plate 104, a first driving unit 103_F, a second driving unit 103_S, and an imaging element 101. As shown in the configuration diagram of FIG. 4, the first optical low-pass filter 102_F, the second optical low-pass filter 102_S, and the quarter-wave plate 104 are provided on the optical path of the subject light from the photographing lens L1 to the image sensor 101. . The subject light incident from the photographing lens L1 passes through the respective members in the order of the first optical low-pass filter 102_F, the quarter-wave plate 104, and the second optical low-pass filter 102_S, and is guided to the image sensor 101. In FIG. 4 also, the optical axis direction of the photographic lens L1 is described as the z axis, and the plane substantially perpendicular to the z axis is described as the xy plane.

  The first optical low-pass filter 102_F includes a pair of first front filters 102FWD_F and first rear filters 102AFT_F. The first front filter 102FWD_F and the first rear filter 102AFT_F correspond to the front filter 102FWD and the rear filter 102AFT of the first embodiment, respectively. In other words, the first rear filter 102AFT_F is driven by the first drive unit 103_F and rotates on a plane substantially perpendicular to the optical axis of the photographic lens L1 (on the xy plane in FIG. 4).

  The first drive unit 103_F includes a first motor 103a_F, a first base 103b_F, and a first transmission unit 103c_F. The first drive unit 103_F is assumed to have the same configuration as the drive unit 103 of the first embodiment. That is, the first motor 103a_F, the first base 103b_F, and the first transmission unit 103c_F correspond to the motor 103a, the base 103b, and the transmission unit 103c of the first embodiment, respectively. As a result, the first motor 103a_F rotates the first base 103b_F via the first transmission unit 103c_F, thereby rotating the first rear filter 102AFT_F on the xy plane.

  The second optical low-pass filter 102_S also includes a pair of second front filters 102FWD_S and a second rear filter 102AFT_S. The second front filter 102FWD_S and the second rear filter 102AFT_S correspond to the front filter 102FWD and the rear filter 102AFT of the first embodiment, respectively. In other words, the second rear filter 102AFT_S is driven by the second drive unit 103_S and rotates on a plane substantially perpendicular to the optical axis of the photographic lens L1 (on the xy plane in FIG. 4). Note that the separation direction of the first optical low-pass filter 102_F when the first mode or the second mode is set is different from the separation direction of the second optical low-pass filter 102_S.

  The second drive unit 103_S includes a second motor 103a_S, a second base 103b_S, and a second transmission unit 103c_S. The second drive unit 103_S has the same configuration as the drive unit 103 of the first embodiment. That is, the second motor 103a_S, the second base 103b_S, and the second transmission unit 103c_S correspond to the motor 103a, the base 103b, and the transmission unit 103c of the first embodiment, respectively. As a result, the second motor 103a_S rotates the second base 103b_S via the second transmission unit 103c_S, thereby rotating the second rear filter 102AFT_S on the xy plane.

  The quarter-wave plate 104 is on the optical path of the subject light and is provided between the first optical low-pass filter 102_F and the second optical low-pass filter 102_S. The quarter-wave plate 104 changes the polarization direction of the subject light emitted from the first optical low-pass filter 102_F and guides it to the second optical low-pass filter 102_S.

  When the first mode is set by the user, the relationship between the separation direction of the first front filter 102FWD_F of the first optical low-pass filter 102_F and the separation direction of the first rear filter 102AFT_F is a shift angle θ = 0 degree. The first rear filter 102AFT_F is rotationally driven so as to satisfy the above. Further, the second rear filter 102AFT_S is set so that the separation direction of the second front filter 102FWD_S of the second optical low-pass filter 102_S and the separation direction of the second rear filter 102AFT_S satisfy the relationship of the shift angle θ = 0 degrees. Driven by rotation. That is, when the first mode is set, each of the first optical low-pass filter 102_F and the second optical low-pass filter 102_S can improve the characteristic of removing light having a high spatial frequency. As described above, the separation direction of the first optical low-pass filter 102_F when the first mode is set is different from the separation direction of the second optical low-pass filter 102_S. Therefore, the separation direction of the first front filter 102FWD_F and the separation direction of the second front filter 102FWD_S, and the separation direction of the first rear filter 102AFT_F and the separation direction of the second rear filter 102AFT_S are different from each other.

  In the first mode, circularly polarized subject light enters the first optical low-pass filter 102_F, and in the same way as the optical low-pass filter 102 described in the first embodiment, linearly polarized ordinary light and linearly polarized light And are incident on the quarter-wave plate 104. Each of the ordinary ray and the extraordinary ray emitted from the first optical low-pass filter 102_F is changed in polarization direction by the quarter-wave plate 104 and enters the second optical low-pass filter 102_S.

  The ordinary ray incident on the second optical low-pass filter 102_S is separated into a linearly polarized ordinary ray and a line-changing extraordinary ray in the same manner as the optical low-pass filter 102 described in the first embodiment, and the imaging element 101. Is incident on. Further, the extraordinary ray incident on the second optical low-pass filter 102_S is separated into a linearly polarized ordinary ray and a linearly polarized extraordinary ray and is incident on the image sensor 101. That is, the subject light from the photographic lens L1 is separated into four linearly polarized light by the first optical low-pass filter 102_F and the second optical low-pass filter 102_S and is incident on the image sensor 101. In this case, subject light is incident on the image sensor 101 such that each light beam forms a square vertex.

  When the second mode is set by the user, the relationship between the separation direction of the first front filter 102FWD_F of the first optical low-pass filter 102_F and the separation direction of the first rear filter 102AFT_F is a shift angle θ = 180 degrees. The first rear filter 102AFT_F is rotationally driven so as to satisfy the above. Further, the second rear filter 102AFT_S is set so that the separation direction of the second front filter 102FWD_S of the second optical low-pass filter 102_S and the separation direction of the second rear filter 102AFT_S satisfy the relationship of the shift angle θ = 180 degrees. Driven by rotation. That is, when the second mode is set, each of the first optical low-pass filter 102_F and the second optical low-pass filter 102_S can weaken the characteristic of removing light having a high spatial frequency and invalidate the optical low-pass filter characteristic. .

  In the second mode, the circularly polarized subject light enters the first optical low-pass filter 102_F and is separated into an ordinary ray and an extraordinary ray as in the optical low-pass filter 102 described in the first embodiment. Without being incident on the quarter-wave plate 104. The subject light that has entered the second optical low-pass filter 102_S via the first optical low-pass filter 102_F and the quarter-wave plate 104 is an ordinary ray as in the optical low-pass filter 102 described in the first embodiment. And incident on the image sensor 101 without being separated into extraordinary rays. That is, the subject light from the photographing lens L1 is incident on the image sensor 101 without changing its optical characteristics by the first optical low-pass filter 102_F and the second optical low-pass filter 102_S.

According to the second embodiment described above, the following operational effects can be obtained.
The first optical low-pass filter 102_F and the second optical low-pass filter 102_S having the same configuration as the optical low-pass filter 102 in the first embodiment are arranged on the optical path of the subject light so that the separation directions thereof are different from each other. Provided. Then, the first optical low-pass filter 102_F is driven by the first driving unit 103_F having the same configuration as that of the driving unit 103 of the first embodiment, and the second optical low-pass filter 102_S is driven by the second driving unit 103_S. I made it. In the case of the first mode, the first optical low-pass filter 102_F is rotationally driven so that the shift angle θ is approximately 0 degrees, and the second optical low-pass filter 102_S is approximately 0 degrees. Driven by rotation. Further, in the case of the second mode, the first optical low-pass filter 102_F is rotationally driven so that the shift angle θ is approximately 180 degrees, and the second optical low-pass filter 102_S is approximately 180 degrees. Driven by rotation. Therefore, even when the subject light is separated into four polarization components by the two first optical low-pass filters 102_F and the second optical low-pass filter 102_S, the optical low-pass filter characteristics are the same as in the first embodiment. One of a state in which is enabled and a state in which the optical low-pass filter characteristic is disabled can be obtained. Furthermore, since the optical low-pass filter characteristic can be invalidated while the first optical low-pass filter 102_F and the second optical low-pass filter 102_S are attached, the attachment of the first optical low-pass filter 102_F to the second optical low-pass filter 102_S It is possible to prevent dust and the like from adhering to the image sensor 101 and the like inside the camera 100.

-Third embodiment-
With reference to the drawings, a third embodiment of the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and different points will be mainly described. Points that are not particularly described are the same as those in the first embodiment. This embodiment is different from the first embodiment in that driving is performed such that the separation direction of the front filter and the separation direction of the rear filter can be other than 0 degrees and 180 degrees.

  FIG. 5 shows the subject after passing through the front filter 102FWD, after passing through the rear filter 102AFT, and when entering the image sensor 101 when the shift angle θ is 0 degree, 45 degrees, 90 degrees, 135 degrees, and 180 degrees. The light separation state is shown. Note that FIG. 5 shows a state in which subject light is separated on a plane parallel to the xy plane. Each of FIGS. 5A, 5B, and 5C shows subject light after passing through the front filter 102FWD, after passing through the rear filter 102AFT, and when entering the image sensor 101 when the shift angle θ = 0 °. The separation state is shown.

  When the shift angle θ = 0 degrees, as described in the first embodiment, the incident subject light is separated into the ordinary ray L1 and the extraordinary ray L2 by the front filter 102FWD by the separation amount d / 2. (FIG. 5A). Then, the ordinary ray L1 and the extraordinary ray L2 separated by the front filter 102FWD are the ordinary ray L1 ′ and the extraordinary ray L2 ′ separated by the separation amount d, as described in the first embodiment. And emitted from the rear filter 102AFT (FIG. 5B). As a result, as shown in FIG. 5C, the subject light incident on the optical low-pass filter 102 is separated into two light beams and enters the image sensor 101.

  FIGS. 5D, 5E, and 5F show subject light after passing through the front filter 102FWD, after passing through the rear filter 102AFT, and when incident on the image sensor 101 when the shift angle θ is 45 degrees. The separation state is shown. Separation of incident subject light by the front filter 102FWD is the same as in the case of FIG. Then, as shown in FIG. 5E, the ordinary ray L1 separated by the front filter 102FWD is emitted from the rear filter 102AFT as an ordinary ray L1 'and an extraordinary ray L1' '. At this time, the extraordinary ray L1 ″ is separated from the ordinary ray L1 ′ by the separation amount d / 2 in the direction of the shift angle θ = 45 degrees. The extraordinary ray L2 separated by the front filter 102FWD is emitted from the rear filter 102AFT as an ordinary ray L2 'and an extraordinary ray L2 ". At this time, the extraordinary ray L2 ″ is separated from the ordinary ray L2 ′ by the separation amount d / 2 in the direction of the shift angle θ = 45 degrees. As a result, as shown in FIG. 5 (f), the subject light incident on the optical low-pass filter 102 is separated into four light beams and enters the image sensor 101. In this case, as shown in FIG. 5 (f), subject light is incident on the image sensor 101 such that each light ray forms a vertex of a rhombus shape.

  Each of FIGS. 5G, 5H, and 5I shows subject light after passing through the front filter 102FWD, after passing through the rear filter 102AFT, and when entering the image sensor 101 when the shift angle θ is 90 degrees. The separation state is shown. Separation of incident subject light by the front filter 102FWD is the same as in FIGS. 5 (a) and 5 (d). Then, as shown in FIG. 5H, the ordinary ray L1 separated by the front filter 102FWD becomes an ordinary ray L1 'and is emitted from the rear filter 102AFT. At this time, the ordinary ray L1 'is emitted from a position shifted by a distance d / 2 in the direction of the shift angle θ = 90 degrees with respect to the position where the ordinary ray L1 is incident on the rear filter 102AFT.

  The extraordinary ray L2 separated by the front filter 102FWD becomes an extraordinary ray L2 'and is emitted from the rear filter 102AFT. As a result, as shown in FIG. 5 (i), the subject light incident on the optical low-pass filter 102 is separated into two light beams and enters the image sensor 101.

  5 (j), (k), and (l) show subject light after passing through the front filter 102FWD, after passing through the rear filter 102AFT, and when entering the image sensor 101 when the shift angle θ = 135 degrees. The separation state is shown. Separation of incident subject light by the front filter 102FWD is the same as in FIGS. 5A, 5D, and 5G. Then, as shown in FIG. 5 (k), the ordinary ray L1 separated by the front filter 102FWD is emitted from the rear filter 102AFT as an ordinary ray L1 ′ and an extraordinary ray L1 ″. At this time, the extraordinary ray L1 ″ is separated from the ordinary ray L1 ′ by the separation amount d / 2 in the direction of the shift angle θ = 135 degrees.

  The extraordinary ray L2 separated by the front filter 102FWD is emitted from the rear filter 102AFT as an ordinary ray L2 'and an extraordinary ray L2 ". At this time, the extraordinary ray L2 ″ is separated from the ordinary ray L2 ′ by the separation amount d / 2 in the direction of the shift angle θ = 135 degrees. That is, extraordinary rays L1 "and L2" whose separation directions differ by 90 degrees as compared with the case shown in FIG. 5F are emitted from the rear filter 120AFT. As a result, as shown in FIG. 5L, the subject light incident on the optical low-pass filter 102 is separated into four light beams and enters the image sensor 101. In this case, as shown in FIG. 5 (l), subject light is incident on the image pickup device 101 so that each light ray forms each apex of a rhombus.

  Each of FIGS. 5 (m), (n), and (o) shows subject light after passing through the front filter 102FWD, after passing through the rear filter 102AFT, and when entering the image sensor 101 when the shift angle θ = 180 degrees. The separation state is shown. When the shift angle θ = 180 degrees, as described in the first embodiment, the incident subject light is separated into the ordinary ray L1 and the extraordinary ray L2 by the front filter 102FWD by the separation amount d / 2. (FIG. 5 (m)). Then, the separation amount d / 2 of the extraordinary ray L2 separated by the front filter 102FWD is canceled by the rear filter 102AFT as described in the first embodiment (FIG. 5 (n)). Therefore, as shown in FIG. 5 (o), the circularly polarized subject light incident on the front filter 102FWD is guided to the image sensor 101 without extraordinary rays being separated.

  In the third embodiment, when the first mode is set by the user, the shift angle θ is configured to be approximately 135 degrees (or approximately 45 degrees) as described above, and the second mode is set. Is configured such that the shift angle θ is 180 degrees. The setting of the first mode and the second mode and the rotational drive of the rear filter 102AFT by the drive unit 103 are the same as in the case of the first embodiment. In the first mode, for example, the shift angle θ can be selected to be either approximately 0 degrees or approximately 135 degrees (or approximately 45 degrees). In the second mode, the shift angle θ is approximately 180 degrees. You may be comprised so that it may become.

According to the third embodiment described above, the following operational effects can be obtained.
The front filter 102FWD and the rear filter 102AFT are configured to have the same birefringence characteristic, and the drive unit 103 places the rear filter 102AFT on the front filter 102FWD on a plane substantially orthogonal to the optical axis of the photographing lens L1. On the other hand, it was driven to rotate between two relatively different positions. In other words, the drive unit 103 rotationally drives the rear filter 102AFT so that the shift angle θ is approximately 135 degrees (or approximately 45 degrees) in the first mode and the shift angle θ is approximately 180 degrees in the second mode. Therefore, the object light in the first mode is not provided in the first mode without the two optical low-pass filters 102_F and 102_S and the quarter-wave plate 104 as in the second embodiment. Can be separated into four polarization components. As a result, this contributes to reduction in size and weight of the apparatus.

The first to third embodiments described above can be modified as follows.
(1) The front filter 102FWD and the rear filter 102AFT may be made of different materials instead of being made of the same material. In this case, for example, the front filter 102FWD may be made of quartz, and the rear filter 102AFT may be made of lithium niobate. In this case, the front filter 102FWD and the rear filter 102AFT may be configured to have different thicknesses so that the separation amount d of the optical low-pass filter 102 becomes a value corresponding to the pixel pitch p.

(2) An operation signal is input from the operation member 109 instead of the one in which the drive unit 103 is driven to switch the shift angle θ between the front filter 102FWD and the rear filter 102AFT between the first mode and the second mode. During this time, the drive unit 103 may continue to drive. In this case, while the operation signal is input from the operation member 109, the control circuit 111 continues to output the drive signal to the drive unit 103. As a result, the rear filter 102AFT continues to rotate in conjunction with the rotation of the drive unit 103. When no operation signal is input from the operation member 109, the control circuit 111 stops outputting the drive signal and stops the rotation drive of the drive unit 103. As a result, in conjunction with the drive stop of the drive unit 103, the rotational drive of the rear filter 102AFT is also stopped. Therefore, since the rear filter 102AFT is driven to rotate according to the amount of operation of the operation member 109 by the user, the optical low-pass filter characteristic desired by the user can be obtained.

  In addition, the present invention is not limited to the above-described embodiment as long as the characteristics of the present invention are not impaired, and other forms conceivable within the scope of the technical idea of the present invention are also within the scope of the present invention. included. The embodiments and modifications used in the description may be configured by appropriately combining them.

101: Image sensor, 102: Optical low-pass filter,
102FWD ... front filter, 102AFT ... rear filter,
102_F ... 1st optical low-pass filter,
102FWD_F: first front filter,
102AFT_F: first rear filter,
102_S ... 2nd optical low-pass filter,
102FWD_S ... 2nd front filter,
102AFT_S ... second rear filter,
103 ... driving unit, 103_F ... first driving unit,
103_S ... 2nd drive part

Claims (8)

An image sensor;
A low-pass filter member disposed in front of the imaging element and including a pair of birefringent optical members;
An image pickup unit comprising: a driving unit that relatively rotates the pair of birefringent optical members. The imaging unit according to claim 1,
One birefringent optical member of the pair of birefringent optical members separates the extraordinary ray by shifting it by a predetermined distance in the first separation direction, and the other birefringent optical member separates the extraordinary ray in the second separation direction. Separated by a predetermined distance,
The driving means has a first position at which an angle between the first separation direction and the second separation direction is approximately 180 degrees, and an angle between the first separation direction and the second separation direction is approximately 0 degrees. An imaging unit, wherein the pair of birefringent optical members are relatively rotated with respect to a second position. The imaging unit according to claim 1,
A second low-pass filter member disposed in front of the image sensor and including a pair of birefringent optical members;
Second driving means for relatively rotating the pair of birefringent optical members included in the second low-pass filter member;
One birefringent optical member of the pair of birefringent optical members included in the second low-pass filter member separates extraordinary rays by shifting a predetermined distance in the third separation direction, and the other birefringent optical member. Separates extraordinary rays by shifting them by a predetermined distance in the fourth separation direction,
The second driving means has a third position at which an angle between the third separation direction and the fourth separation direction is approximately 180 degrees, and an angle between the third separation direction and the fourth separation direction. Relative rotation between the pair of birefringent optical members between the fourth position of 0 degrees,
The first position and the third position, and the second position and the fourth position are different from each other,
When the pair of birefringent optical members included in the low-pass filter member are relatively rotated to the first position by the driving means, the pair of birefringent optical members included in the second low-pass filter member Is relatively rotated to the third position by the second driving means, and the pair of birefringent optical members included in the low-pass filter member are relatively rotated to the second position by the driving means, 2. The imaging unit according to claim 1, wherein the pair of birefringent optical members included in the second low-pass filter member are relatively rotated to the fourth position by the second driving unit. The imaging unit according to claim 2,
The pair of birefringent optical members have the same birefringence characteristics;
The driving means relatively rotates the pair of birefringent optical members between the first position and a fifth position different from the second position,
The imaging unit according to claim 5, wherein the fifth position has an angle formed by the first direction and the second direction of approximately 135 degrees or 45 degrees. The imaging unit according to claim 2,
The pair of birefringent optical members have the same birefringence characteristics;
The driving means relatively rotates the pair of birefringent optical members between the first position, the second position, and the fifth position,
The imaging unit according to claim 5, wherein the fifth position has an angle formed by the first direction and the second direction of approximately 135 degrees or 45 degrees. The imaging unit according to claim 4 or 5,
The pair of birefringent optical members have substantially the same thickness with respect to the optical axis direction. The imaging unit according to claim 3,
An imaging unit, further comprising a quarter-wave plate between the low-pass filter member and the second low-pass filter member. Optical system,
The imaging unit according to any one of claims 1 to 7,
An image pickup apparatus comprising: an image generation unit configured to generate image data using an image signal output from the image pickup element.

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