JP2005173265A - Optical element, optical filter device, and optical instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmittance variable ND filter using a light shielding liquid.
SOLUTION: First and second optical members having first and second optical members arranged in an optical axis direction and a liquid layer formed between the first and second optical members. The optical element is characterized in that the thickness of the liquid layer in the optical axis direction changes as a result of relative movement in the direction orthogonal to the optical axis.
[Selection] Figure 1

Description

  The present invention relates to an optical filter and a light amount adjusting device used in an optical apparatus such as a camera.

  An imaging optical system used in an optical apparatus such as a camera generally includes a light amount adjusting device that adjusts the amount of incident light, that is, a so-called diaphragm device. In the diaphragm device, a plurality of diaphragm blades having light shielding properties are used, and an outer edge portion of the diaphragm blade forms an opening having a predetermined shape.

  Then, the amount of the light beam passing through the aperture opening is adjusted by driving the aperture blade by the actuator to change the aperture area of the aperture. However, as the aperture area of the aperture is reduced, the influence of diffraction generated at the outer edge of the aperture blade increases, and the imaging performance of the imaging optical system decreases.

  In order to avoid this drawback, a technique is disclosed in which a neutral density filter (hereinafter abbreviated as ND filter) using a light-shielding liquid or an optical wedge is provided, and the amount of light is attenuated by the ND filter instead of reducing the aperture diameter. ing.

  For example, Patent Document 1 includes a first optical element in which a first opaque fluid is sealed between two transparent plates, and a second optical element in which a second opaque fluid is sealed between two transparent plates. A light amount adjusting device that changes the amount of transmitted light while keeping the optical path length constant by appropriately adjusting the interval between the transparent plates of the optical elements is disclosed.

  Further, in Patent Document 2, a transparent elastic body and a light shielding liquid are sealed between two transparent plates, and the distance between the two transparent plates is changed by a piezoelectric element, so that the transparent elastic body transmits the light shielding liquid in the optical path to the optical path. A light amount adjusting device that changes the amount of transmitted light is disclosed.

  In Patent Document 3, a transparent liquid and a light-shielding liquid that are insoluble in each other are sealed in a liquid storage part, and an interface shape between both liquids is formed by applying a voltage between an electrode provided in the liquid storage part and the liquid. An optical element that changes the amount of transmitted light is disclosed.

Also, in Patent Document 4, two similar optical wedges having predetermined light attenuation characteristics are overlapped symmetrically, and one optical wedge is moved in a direction perpendicular to the optical axis, whereby the amount of transmitted light is reduced. A varying filter device is disclosed.
JP-A-5-313076 (paragraph numbers 0034 and 0035, FIG. 1 and FIG. 2) Japanese Patent Laid-Open No. 11-174522 (paragraph numbers 0011 and 0012, FIGS. 3 and 4) JP 2001-228307 A (paragraph number 0008) JP-A-6-194585 (paragraph numbers 0007 and 0008)

  However, the above prior art has the following drawbacks. First, in the prior art disclosed in Patent Document 1, an elastic film that connects two transparent plates is provided, and the film constitutes a liquid chamber that contains liquid that has been removed as the transparent plate approaches. However, if the volume of the liquid chamber is small, there is a drawback that the driving resistance of the transparent plate increases or the film is broken to leak the liquid.

  Further, since the two sets of optical elements are arranged in series on the optical axis, there is also a drawback that the entire length of the lens system that occupies a large space in the optical axis direction and that incorporates the light amount adjusting device becomes long.

  In the prior art disclosed in Patent Document 2, the optical path length changes as the distance between the two transparent plates changes, and the transparent plate may be deformed by the repulsive force of the transparent elastic plate.

  The prior art disclosed in Patent Document 3 has a drawback in that the interface between the transparent liquid and the light-shielding liquid is spherical and the transmittance varies depending on the location, that is, the transmittance for incident light is not constant.

  The prior art disclosed in Patent Document 4 has a drawback that the optical path length changes as the optical wedge moves.

    Accordingly, an object of the present invention is to provide an optical filter using an optical wedge and a light shielding liquid, in which the optical path length remains unchanged even when the transmittance is changed and the transmittance with respect to the incident height is constant. Yes.

  According to the first configuration of the optical element of the present invention, the optical element includes the first and second optical members arranged in the optical axis direction, and the liquid layer formed between the first and second optical members. In addition, the thickness of the liquid layer in the optical axis direction is changed by the relative movement of the first and second optical members in the direction orthogonal to the optical axis.

  Here, the optical axis thickness of the first optical member continuously increases in a specific direction among the orthogonal directions of the optical axis, and the optical axis thickness of the second optical member continuously increases in the specific direction. Decrease.

  In addition, it is preferable that the distance between the light incident surface and the light exit surface in the optical element in the optical axis direction is unchanged.

  It is preferable that the first optical member is fixed in the direction orthogonal to the optical axis and the second optical member is movable in the direction orthogonal to the optical axis.

  It is preferable to form a liquid storage part in which the liquid forming the liquid layer is stored in the first optical member, and to dispose the second optical member in the liquid storage part.

  Two first optical members are disposed on both sides of the second optical member in the optical axis direction, and the first optical member between the first optical member and the second optical member of the two first optical members is first. May be formed, and the second liquid layer may be formed between the other first optical member and the second optical member.

  The light transmittance of the optical element changes due to the change in the thickness of the liquid layer in the optical axis direction.

  An optical filter device comprising: the above-described optical element; and a driving unit that relatively drives the first and second optical members in a direction orthogonal to the optical axis.

  An optical apparatus comprising an imaging optical system that includes an optical filter device and forms an object image.

  An optical apparatus comprising an image sensor that photoelectrically converts an object image.

  According to the first configuration of the optical element of the present invention, the thickness of the liquid layer in the optical axis direction changes and the optical characteristics change only by relatively moving the first and second optical members in the direction orthogonal to the optical axis. be able to.

  Further, the first optical member is configured such that the optical axis direction thickness continuously increases in a specific direction among the optical axis orthogonal directions, and the second optical member is configured to have an optical axis direction thickness in the specific direction. Is configured such that the thickness of the first optical member and the second optical member in the optical axis direction is continuously changed in a specific direction in the direction orthogonal to the optical axis. Thus, the optical characteristics can be changed.

  In addition, since the distance between the light incident surface and the light exit surface in the optical element in the optical axis direction is unchanged, the optical characteristics can be changed without changing the optical path length.

  By forming a liquid storage portion in which the liquid forming the liquid layer is stored in the first optical member, and arranging the second optical member in the liquid storage portion, the liquid layer can be reliably configured with a simple configuration. The thickness in the optical axis direction can be changed.

By changing the light transmittance of the optical element due to the change in the thickness of the liquid layer in the optical axis direction, the optical element can be used for light amount adjustment.
According to an imaging device that is one of optical devices having an optical filter device, an imaging optical system that forms an object image, and an imaging device that photoelectrically converts the object image, this occurs when adjusting the amount of light using a conventional iris diaphragm. In addition to avoiding small-aperture diffraction, there is no bias in image plane illuminance, and focus movement and optical aberration fluctuations can be suppressed, so that a high-definition image can be obtained.

  This example is shown below.

  1A and 1B are diagrams showing the structure of a light amount adjusting device 100 including an optical filter that is Embodiment 1 of the present invention, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view. First, the configuration of the main part of the optical filter will be described with reference to FIG.

  C is an optical axis of the optical filter, L1 is a light beam incident on the optical filter, and L2 is a light beam emitted from the optical filter. 101 is a fixed first optical wedge (first optical member), 102 is a fixed first optical wedge (first optical member), and 103 is a movable second optical wedge (second optical member). Optical members) (both are transparent optical resins such as acrylic or wedge-shaped optical elements molded with a glass mold. Note that the first optical wedges 101 and 102 are movable, and the second optical wedge 103 is A fixed type may be used, and a second optical wedge 103 that is split may be used.

  Here, both of the fixed first optical wedges 101 and 102 have a shape in which the thickness continuously increases in the left direction (specific direction) in the figure in a plane orthogonal to the optical axis C. The second optical wedge 103 and a light-shielding liquid described later are accommodated in a wedge-shaped region (hereinafter referred to as “liquid storage portion”) formed inside by integrating these optical wedges. . Further, as shown in the figure, the upper surface of the first optical wedge 101 is the entrance surface, and the lower surface of the first optical wedge 102 is the exit surface. The distance from the surface is unchanged in this embodiment in order to keep the optical path length constant.

  On the other hand, the movable second optical wedge 103 has a shape in which the thickness continuously decreases in the same way toward the left.

  The opposing surfaces of the first optical wedge 101 and the second optical wedge 103 are parallel and are inclined with respect to the optical axis C by a predetermined angle. The opposing surfaces of the first optical wedge 102 and the second optical wedge 103 are also parallel and inclined with respect to the optical axis C by a predetermined angle.

  Reference numeral 104 denotes a light-shielding liquid that fills the liquid container. For example, a liquid in which black dye is dissolved in silicone oil is used. Here, it is preferable that the first optical wedges 101 and 102, the second optical wedge 103, and the light shielding liquid 104 are made of materials having substantially the same refractive index.

  The light-shielding liquid 104 forms a liquid layer 104a having a uniform thickness between the opposing surfaces of the first optical wedge 101 and the second optical wedge 103, and similarly, the second optical wedge 103 and the first optical wedge 103 are formed. A liquid layer 104 b having a uniform thickness is also formed between the opposing surfaces of the wedge 102.

  Reference numeral 105 denotes a drive shaft attached to the proximal end portion of the second optical wedge 103, and the right distal end portion 105a is bent 90 degrees. Reference numeral 106 denotes a cylindrical liquid sealing member made of an elastic material such as rubber. The drive shaft 105 is mounted in a central hole so as to be in close contact with and slidable. Nipped by the optical wedge 102.

  The three-dimensional shape of each member described above is shown in the exploded perspective view of FIG. In the figure, first optical wedges 101 and 102 are optical members for keeping the optical path length constant, and as a container for accommodating a second optical wedge 103 and a light shielding liquid 104 (not shown in FIG. 2). It also has a role.

  The drive shaft 105 is an intermediate member for driving the second optical wedge 103 from the outside, and the sealing member 106 serves to seal the light-shielding liquid 104 in the liquid storage portion.

  Furthermore, since the width dimension in the front-rear direction of the paper surface in the liquid storage portion is slightly larger than the width dimension of the second optical wedge 103 (front-rear direction dimension of the paper surface), driving the drive shaft 104 from the outside allows The two optical wedges 103 can be moved in the horizontal direction of the drawing within the liquid container (can be moved within the plane orthogonal to the optical axis). These 101 to 106 constitute an optical filter 120.

  Subsequently, returning to FIG. 1B, the description of the light amount adjusting device will be continued. Reference numeral 111 denotes a ground plate for fixing and holding the optical filter 120 and a driving mechanism, which will be described later. The first optical wedge 102 is bonded and fixed, and a light beam L1 incident on the optical filter 120 is passed through the central portion. A circular opening 111c, which is a passing optical path, is provided.

  Therefore, the light beam L1 incident on the optical filter 120 is attenuated by the liquid layers 104a and 104b and is emitted from the opening 111c as an emitted light beam L2. Here, since the first optical wedges 101 and 102, the second optical wedge 103, and the liquid layers 104a and 104b located in the optical path of the light beam L1 incident on the optical filter 120 have substantially the same refractive index, the incident light beam L1 goes straight without being refracted in the optical filter 120, and only the amount of light is reduced.

  Then, by driving the second optical wedge 103 in the optical axis orthogonal plane via the drive shaft 105, the thickness of the two liquid layers 104a and 104b in the optical axis direction is adjusted, and the transmittance for the incident light beam L1 is adjusted. can do.

  Also, when adjusting the transmittance, the optical path length of the optical filter 120 does not change, so that even if it is applied to a photographing optical system or the like, focus movement and fluctuation of optical aberration do not occur.

  Next, the drive mechanism of the second optical wedge 103 will be described with reference to FIG. In FIG. 2A, the first optical wedge 101 and the light shielding liquid 104 are not shown. A step motor 112 is a drive source for the second optical wedge 103 and is fixed to the main plate 111.

  A lead screw 113 is directly connected to the rotor of the step motor 112, and the right end is fitted in a hole provided in the bent portion 111a of the base plate 111, thereby preventing the tip from shaking. Reference numeral 114 denotes a nut that is screwed to the lead screw 113, and a driving pin 114a of a driving lever to be described later is attached to the upper surface of the nut. Reference numeral 115 denotes a rotation stop shaft of the nut 114, the left end is fixed to the main body of the step motor 112, and the right end is fixed to the bent portion 111 a of the main plate 111.

  Reference numeral 116 denotes a drive lever, 117 denotes a drive lever support shaft, and the drive lever 116 is supported so as to be rotatable about the drive lever support shaft 117.

  A U-shaped notch groove portion is provided at one end of the drive lever 116, a bent portion 105a of the drive shaft 105 is fitted, and a U-shaped notch groove portion is provided at the other end. The pin 114a is fitted.

  In the above configuration, when the step motor 112 is driven, the lead screw 113 rotates and the nut 114 is driven in the left-right direction. When the drive lever 116 starts rotating, the second optical wedge 103 moves in the direction perpendicular to the optical axis via the drive shaft 105, and the transmittance of the optical filter 120 can be adjusted. The state of the transmittance control will be described with reference to FIGS.

  FIG. 3 shows a state where the transmittance of the optical filter 120 is maximum. When the step motor 112 is driven, the nut 114 moves to the right along the lead screw 113. Here, as described above, the drive pin 114a that engages with a U-shaped groove formed at one end of the drive lever 116 is provided on the upper surface of the nut 114, so that the nut 114 moves in the right direction. As a result, the drive lever 116 is rotated in the clockwise direction, the second optical wedge 103 moves to the left end in the liquid storage portion, and the liquid storage portions of the first optical wedge 101 and the second optical wedge 102 are moved. Stops in close contact with the peripheral surface. Therefore, the thickness of the liquid layer 104a and the liquid layer 104b becomes zero, and the light is not attenuated by the light-shielding liquid, so that the transmittance is a value close to 100%.

  When the step motor 112 is driven from the state of FIG. 3 to move the nut 114 in the left direction, the drive lever 116 rotates counterclockwise, and the second optical wedge 103 that is in close contact with the left end of the liquid container is formed. Leave from there.

  Then, as shown in FIG. 4, since the light shielding liquid 104 enters the optical path of the light beam L1 incident on the optical filter 120 (the same state as FIG. 1), the transmittance of the optical filter 120 is lower than the state of FIG. .

  When the nut 114 further moves to the left by the rotation of the lead screw 113, the second optical wedge 103 moves to the right end of the liquid container, and the state shown in FIG. At this time, the thickness of the liquid layer 104a and the liquid layer 104b is maximized, and the transmittance of the optical filter 120 is minimized.

  FIG. 6 is a diagram for explaining the optical superiority of the optical filter of the present embodiment. Previously, in the optical filter 120 of the present embodiment, it has been described that the thickness of the liquid layers 104a and 104b of the light shielding liquid 104 is constant regardless of the location. Therefore, the transmittance of the optical filter 120 of this embodiment is constant regardless of the incident height of the light beam to the filter.

  FIG. 6A shows the incident angle dependence of the transmittance of the optical filter 120. In the figure, when the transmittances for the oblique incident lights L12 and L13 are different, asymmetry occurs in the brightness of the image on the image plane. However, in the optical filter 120 of the present embodiment, since the total thickness values of the liquid layers 104a and 104b in the optical paths of the incident light L12 and L13 are equal, the transmittance with respect to the normal incident light L11 is maximum, and the transmittance with respect to the oblique incident light is The image is symmetrical with respect to the normal incident light L11, so that the image does not appear unnatural.

  FIG. 6B is a diagram for explaining a change in transmittance when the position of the second optical wedge 103 is shifted in the optical axis direction. In the figure, a case where the second optical wedge 103 is displaced downward is shown. At this time, the thickness of the liquid layer 104a increases and the thickness of the liquid layer 104b decreases, but the total value of both is unchanged. Accordingly, the transmittances for the light beams L14, L15, and L16 are all equal and unchanged. That is, in the optical filter of the present embodiment, even if the second optical wedge is displaced in the optical axis direction, the transmittance is not affected.

  FIG. 7 is a diagram in which the light amount adjusting device 100 described with reference to FIGS. In the present embodiment, a digital still camera will be described as an example in which the photographing apparatus photoelectrically converts reflected light from a subject into an electrical signal and records this as digital data. However, the present invention is not limited to a digital still camera, and the same effect can be obtained when applied to photographing apparatuses such as a silver salt film camera, a video camera, an industrial tool camera, a surveillance camera, and a robot image input means.

  An imaging optical system 400 includes a plurality of lens groups, and includes a front lens group 401, a zoom lens group 402, a focusing lens group 403, and an optical low-pass filter 404.

  Reference numeral 100 denotes the light amount adjusting device shown in FIG. 1, but in the following description, it is referred to as an ND filter. A shutter mechanism 433 adjusts the exposure time. In addition, a CCD 411 serving as an image sensor is disposed at the focal position (scheduled imaging plane) of the photographing optical system 400. The CCD 411 includes a photoelectric conversion unit such as a two-dimensional CCD that includes a plurality of photoelectric conversion units that convert irradiated light energy into charges, a charge storage unit that stores the charges, and a charge transfer unit that transfers the charges and sends them to the outside. Conversion means are used. A CMOS image sensor may be used instead of the CCD.

  The subject image formed on the CCD 411 is converted into an electric signal as a charge amount for each pixel corresponding to the intensity of the brightness, amplified by the amplifier circuit 441, and then a predetermined γ by the camera signal processing circuit 442. Processing such as correction is performed. This processing may be performed by digital signal processing after A / D conversion.

  The video signal generated in this way is recorded in the memory 443. As the memory 443, various kinds of devices such as a semiconductor memory such as a flash ROM, an optical memory such as a magneto-optical disk, and a magnetic memory such as a magnetic tape can be used.

  A display 421 such as a liquid crystal display displays a subject image acquired by the CCD 411, a shooting mode, and the like. A group of operation switches 422 includes a zoom switch, a shooting preparation switch, a shooting start switch, and shooting condition switches for setting an exposure control mode, an AF mode, and the like.

  A zoom actuator 423 drives the zoom lens group 402 and changes the focal length of the photographing optical system 400. Reference numeral 424 denotes a focus actuator that drives the focusing lens group 403 to adjust the focus state of the photographing optical system 400.

  A CPU 431 controls the operation of the entire photographing apparatus. Reference numeral 432 denotes an ND filter driving circuit that drives the step motor 112 of FIG. 1 and adjusts the transmittance of the ND filter 100. A shutter mechanism 433 includes a plurality of light shielding blades and an actuator for driving the light shielding blades. A shutter drive circuit 434 drives the shutter mechanism, drives the shutter mechanism 433, and controls the exposure time to the CCD 411.

  FIG. 8 is a control flowchart of the CPU 431 included in the photographing apparatus shown in FIG. Hereinafter, the control flow of the photographing apparatus will be described with reference to FIG.

  Through step 101, in step 102, it is determined whether or not the main switch is turned on by the photographer. If it is determined in step 102 that the main switch is turned on, the CPU 431 exits the sleep state and executes step 111 and subsequent steps.

  In step 111, the photographing apparatus is initialized. Specifically, the photographic optical system in the retracted state is driven out to a shootable state, or setting of shooting conditions by the photographer is accepted.

  In step 112, the CCD 411 and the camera signal processing circuit 442 are driven to obtain a preview image, and in step 113, the preview image is displayed on the display unit 421.

  In step 114, it is determined whether or not the photographer has turned on a photographing preparation switch (denoted as SW1 in the flowchart) linked to the first stroke of the release button. When the on operation is not performed, the process returns to step 112 and the preview image display is repeatedly executed. If it is determined in step 114 that the shooting preparation switch has been turned on, step 114 is skipped and step 121 and subsequent steps are executed.

  In steps 121 to 122, the focus of the photographing optical system 400 is adjusted. This is so-called hill-climbing servo AF, which is focus adjustment control for finding a focus position based on an AF evaluation value signal in which the high-frequency component of the image signal has a maximum value and stopping the focus lens. In step 123, it is determined whether or not the subject is in focus. If the subject is not in focus, step 121 and step 122 are repeatedly executed. When the in-focus state is obtained, the driving of the focusing lens is stopped, and the routine proceeds to step 131.

  In step 131, photometric calculation is performed. Specifically, the light amount of the subject light beam received by the CCD 411 is determined, and the transmittance of the ND filter and the shutter time for calculating the light amount at the time of photographing are calculated.

  In step 132, the drive amount of the movable optical wedge 103 in FIG. 1 is calculated based on the transmittance control value calculated in step 131. In step 133, the step motor 112 in FIG. 1 is driven so that the transmittance calculated in step 132 is obtained.

  In step 134, it is determined whether or not the shooting trigger switch (denoted as SW2 in the flowchart) linked to the second stroke of the release button is turned on. If not, steps 131 to 133 are performed. Run repeatedly. On the other hand, if it is turned on, the process jumps from step 134 to step 141 to execute the photographing operation.

  In step 141, image signal accumulation in the CCD 411 is started. In step 142, based on the shutter time calculated in step 131, the shutter is closed. In step 143, the charge accumulated in the CCD 411 is read out through the charge transfer line and input to the camera signal processing circuit 442. In step 144, the input analog image signal is A / D converted in the camera signal processing circuit 442, image processing such as AGC control, white balance, γ correction, and edge enhancement is performed, and further stored in the CPU 431 as necessary. JPEG compression or the like is performed with the image compression program. In step 145, the image signal obtained in step 144 is recorded in the memory 443, and in step 146, the photographing operation ends.

  As described above, when the photographing apparatus incorporating the light amount adjusting device of the present embodiment is used, the light amount is adjusted by the light amount adjusting device, that is, the ND filter's dimming action, so that the small aperture diffraction by the conventional iris diaphragm is avoided. High-definition images can be obtained. Also, when adjusting the amount of light of the ND filter, since the optical path length in the ND filter is not changed, focus movement and aberration fluctuation do not occur, and image degradation does not occur.

  The present embodiment differs from the first embodiment in the configuration of the driving means of the second optical wedge 103, and all other members are the same. FIGS. 9A and 9B are diagrams showing the structure of the light amount adjusting device 200 provided with the optical filter of the present embodiment. FIG. 9A is a plan view and FIG. First, the configuration of the main part of the optical filter will be described with reference to FIG.

  201 is a fixed first optical wedge, 202 is a fixed first optical wedge, 203 is a movable second optical wedge, and 204 is a light-shielding liquid that fills the space surrounded by these three optical wedges. As in Example 1, a silicone oil in which a black dye is dissolved is used. The liquid forms a liquid layer 204 a having a uniform thickness between the opposing surfaces of the first optical wedge 201 and the second optical wedge 202, and similarly, the second optical wedge 203 and the first optical wedge 202. A liquid layer 204b having a uniform thickness is also formed between the opposing surfaces. Since the shapes and optical characteristics of these optical wedges and the liquid layer are all the same as those of the first embodiment, detailed description thereof is omitted.

  Subsequently, a drive mechanism of the second optical wedge 203 will be described with reference to FIG. In FIG. 5A, the first optical wedge 201 and the light shielding liquid 204 are not shown. Reference numeral 211 denotes a ground plate for fixing and holding an optical filter and a driving mechanism, which will be described later. The first optical wedge 202 is bonded and fixed, and a circular portion for allowing the light beam L1 entering the optical filter to pass through the center. An opening 211c is provided.

  205 and 206 are permanent magnets, which are fixed to the side surface of the second optical wedge 203. 212 is a coil, 213 is a yoke, and the coil is bonded and fixed to the surface of the yoke. Further, the yoke 213 is bonded and fixed to the outer concave portion 202 a of the first optical wedge 202. The surface of the permanent magnet 205 facing the coil 212 is magnetized to the N pole, and the surface of the permanent magnet 206 facing the coil 212 is magnetized to the S pole.

  The three-dimensional shape of each member described above is shown in the exploded perspective view of FIG. In the figure, first optical wedges 201 and 202 are fixed optical members, and also serve as a container for storing a second optical wedge 203 and a light-shielding liquid 204 (not shown in FIG. 10).

  The yoke 213 and the coil 212 are fixed to the recess 202a of the first optical wedge 202. On the other hand, the two permanent magnets 205 to 206 are mounted on the second optical wedge 203, and these are sealed together with a light-shielding liquid (not shown) in a liquid storage portion formed by the first optical wedges 201 and 202. Is done. In other words, the second optical wedge 203 having a permanent magnet is accommodated in the liquid accommodating portion, an electromagnet is disposed outside the liquid accommodating portion, and the permanent magnet and the electromagnet face each other across the wall of the liquid chamber. .

  In addition, a guide groove portion 202b when the permanent magnets 205 to 206 move is provided inside the first optical wedge 202, and a guide groove 201b is also provided inside the first optical wedge 201. Therefore, the second optical wedge 203 and the permanent magnets 205 to 206 are integrally held so as to be movable in the left-right direction in the liquid storage portion (moves in the plane orthogonal to the optical axis). That is, the guide groove portions 201b and 202b serve as holding means.

  In the above configuration, when a current in a predetermined direction is applied to the coil 212, an electromagnetic force is generated between the permanent magnets 205 and 206, and the second optical wedge 203 moves in a predetermined direction. On the other hand, when the energization direction to the coil 212 is reversed, the moving direction of the second optical wedge 203 is also reversed. Then, the position of the permanent magnet 205 or 206 is detected by a known magnetoresistive element (not shown), and the current supplied to the coil 212 is controlled based on the detection result, whereby the second optical wedge 203 is moved to a desired position. Can be controlled. That is, also in this embodiment, by controlling the position of the second optical wedge 203, in FIG. 9B, the ratio of the emitted light beam L2 to the incident light beam L1, that is, the transmittance can be freely adjusted.

  The light quantity adjusting device 200 described above has the same effects as those of the first embodiment and has a feature that the drive mechanism can be further reduced in size. Similarly to the first embodiment, the light amount adjusting device is incorporated in the photographing device of FIG. 7 and is controlled according to the flow diagram of FIG. 8 to adjust the light amount by the dimming action of the light amount adjusting device, that is, the ND filter. Small aperture diffraction by the conventional iris diaphragm is avoided, and a high-definition image can be obtained. Also, when adjusting the amount of light of the ND filter, since the optical path length in the ND filter is not changed, focus movement and aberration fluctuation do not occur, and image degradation does not occur.

  The present embodiment differs from the first and second embodiments in the shapes of the fixed optical wedge and the movable optical wedge, and the driving means of the movable optical wedge and the sealing structure of the light shielding liquid. FIGS. 11A and 11B are diagrams showing the structure of a light amount adjusting device 300 provided with the optical filter of the present embodiment. FIG. 11A is a plan view and FIG. First, the configuration of the main part of the optical filter will be described with reference to FIG.

  C is an optical axis of the optical filter, L1 is a light beam incident on the optical filter, and L2 is a light beam emitted from the optical filter. Reference numeral 301 denotes a fixed first optical wedge (first optical member), and 302 denotes a movable second optical wedge (second optical member), both of which are molded with an optical transparent resin such as acrylic or a glass mold. Wedge-shaped optical element.

  Here, the first optical wedge 301 has a shape in which the thickness continuously increases toward the left in the figure within a plane orthogonal to the optical axis C. On the other hand, the movable second optical wedge 302 has a shape in which the thickness continuously decreases toward the left. The opposing surfaces of the first optical wedge 301 and the second optical wedge 302 are parallel to each other and inclined at a predetermined angle with respect to the optical axis of the incident light beam.

  Reference numeral 307 denotes a sealing plate made of a soft magnetic material such as iron, which is fixed to the outer periphery of the first optical wedge 301, and has a circular opening 307c at the center. A protrusion 302a is formed on the entire circumference of the upper surface of the second optical wedge 302, and a strip magnet 305 is fixed to the inside thereof. A magnetic fluid 306 is applied on the magnetic pole on the upper surface of the strip magnet 305.

  According to the above-described configuration, the band-shaped magnet 305 is attracted to the sealing plate 307 via the magnetic fluid 306, so that the second optical wedge 302 is also attracted upward and the protrusion 302 a comes into contact with the sealing plate 307. .

  With the above-described configuration and operation, the two optical wedges (301, 302) and the sealing plate 307 form a sealed space, that is, a liquid storage portion, and the liquid storage portion is filled with the light-shielding liquid 304. As the light-shielding liquid 304, a solution obtained by dissolving a black dye in silicone oil is used as in the first embodiment.

  Here, it is preferable that the first optical wedge 301, the second optical wedge 302, and the light shielding liquid 304 are all made of materials having substantially the same refractive index. The light shielding liquid 304 forms a liquid layer 304 a having a uniform thickness between the opposing surfaces of the first optical wedge 301 and the second optical wedge 302. The optical filter 320 is composed of the above members. In FIG. 11A, the sealing plate 307 and the light shielding liquid 304 are not shown.

  Next, the drive mechanism of the second optical wedge 302 will be described with reference to FIG. Reference numeral 311 denotes a ground plate for fixing and holding the optical filter 320. The first optical wedge 301 is bonded and fixed, and a circular opening 311c through which the light beam L1 incident on the optical filter 320 passes is provided at the center. It is done.

  Reference numerals 312 and 313 denote coils, which are fixed to the upper surface of the sealing plate 307. Here, when the coil 312 is energized, an attractive force is generated between the coil 312, the permanent magnet 305, and the magnetic fluid 306, and the second optical wedge 302 moves to the left in FIG.

  On the other hand, when the coil 313 is energized, an attractive force is generated between the coil 313, the permanent magnet 305, and the magnetic fluid 306, and the second optical wedge 302 moves to the right in FIG. At this time, since the magnetic fluid 306 is interposed in the contact portion between the second optical wedge 302 and the sealing plate 307, the light shielding liquid 304 is sealed without leaking out of the liquid chamber.

  The three-dimensional shape of each member described above is shown in the exploded perspective view of FIG. In the figure, a first optical wedge 301 is a fixed optical member, and also serves as a container for accommodating a second optical wedge 302 and a light shielding liquid 304 (not shown in FIG. 12). A protrusion 302a is formed on the entire circumference of the upper surface of the second optical wedge 302, and the above-described band magnet 305 and magnetic fluid 306 are accommodated inside the protrusion. Further, a sealing plate 307 corresponding to the lid of the liquid storage unit is placed to seal the light-shielding liquid 304, and two coils 312 and 313 are fixed to the upper surface thereof.

  Then, the second optical wedge 302 comes into contact with the sealing plate with an attractive force acting between the sealing plate 307 and the strip magnet 305. That is, in this embodiment, the inner surface (liquid chamber) of the first optical wedge 301 and the sealing plate 307 serve as a holding unit for the movable optical wedge 302.

  In the above configuration, when a current in a predetermined direction is applied to the coil 312, the strip magnet 305 and the magnetic fluid 306 are attracted and the second optical wedge 302 moves to the left. On the other hand, when a current in a predetermined direction is applied to the coil 313, the strip magnet 305 and the magnetic fluid 306 are attracted and the second optical wedge 302 moves to the right. The position of the second optical wedge 302 can be controlled by detecting the position of the strip magnet 305 with a magnetic resistance (not shown) and controlling the ratio of the current flowing to the coils 312 and 313 based on the detection result. It is.

  Therefore, in FIG. 11B, the light beam L1 incident on the optical filter is attenuated by the liquid layer 304a and is emitted as an emitted light beam L2 from the opening 311c. Here, the refractive index of the two optical wedges (301, 302) positioned in the optical path of the light beam L 1 incident on the optical filter 320 and the liquid layer 304 a therebetween is approximately equal, so that the light beam L 1 is refracted in the optical filter 320. Go straight without reducing the amount of light. Even when the transmittance is adjusted, the optical path length of the optical filter 320 is unchanged, so that even if it is applied to a photographic optical system or the like, focus movement and fluctuation of optical aberration do not occur.

  Since the optical filter 320 of the present embodiment requires fewer optical wedges than the optical filter 120 of the first embodiment, the apparatus can be reduced in size and cost.

  Further, since the light shielding liquid is sealed and the movable optical wedge is driven using the magnetic fluid, the sealing reliability of the liquid is improved. Similarly to the first embodiment, the light amount adjusting device 300 is incorporated in the photographing device of FIG. 7 and is controlled according to the flow diagram of FIG. 8 to adjust the light amount by the dimming action of the light amount adjusting device, that is, the ND filter. Small aperture diffraction by the conventional iris diaphragm is avoided, and a high-definition image can be obtained. Also, when adjusting the amount of light of the ND filter, since the optical path length in the ND filter is not changed, focus movement and aberration fluctuation do not occur, and image degradation does not occur.

  According to each of the above-described embodiments, according to the optical filter, the light shielding liquid layer having a uniform thickness is provided between the fixed optical wedge and the movable optical wedge, and the position of the movable optical wedge is changed by changing the position of the movable optical wedge. The transmittance can be controlled to a desired value by changing the thickness. At this time, the optical characteristics are less dependent on incident light and incident angle, and the optical path length does not change. Therefore, if this optical filter is applied to an imaging device, it avoids the small aperture diffraction that occurs when adjusting the amount of light with the conventional iris diaphragm, and there is no bias in the image plane illuminance, suppressing focus movement and fluctuations in optical aberrations. Therefore, a high-definition image can be obtained.

It is principal part explanatory drawing of the light quantity adjustment apparatus in Example 1. FIG. 2 is an exploded perspective view of an optical filter in Embodiment 1. FIG. It is explanatory drawing of the transmittance | permeability control mechanism of the light quantity adjustment apparatus in Example 1. FIG. It is explanatory drawing of the transmittance | permeability control mechanism of the light quantity adjustment apparatus in Example 1. FIG. It is explanatory drawing of the transmittance | permeability control mechanism of the light quantity adjustment apparatus in Example 1. FIG. FIG. 3 is a diagram for explaining optical superiority of the optical filter according to the first embodiment. It is a block diagram of an imaging device. It is a control flowchart of an imaging device. It is principal part explanatory drawing of the light quantity adjustment apparatus in Example 2. FIG. 6 is an exploded perspective view of an optical filter according to Embodiment 2. FIG. It is principal part explanatory drawing of the light quantity adjustment apparatus in Example 2. FIG. 6 is an exploded perspective view of an optical filter according to Embodiment 2. FIG.

Explanation of symbols

C: Optical axis L1: Incident light beam L2: Emission light beam 100, 200, 300: Light amount adjusting device (ND filter)
120, 220, 320 ... optical filters 101, 102, 201, 202, 301 ... first optical wedges 103, 203, 302 ... second optical wedges 104, 204, 304 ... light shielding properties Liquid 104a, 104b, 204a, 204b, 304a ... Liquid layer 105 ... Drive shaft 106 ... Liquid sealing member 111, 211, 311 ... Base plate 112 ... Step motor 116 ... Drive lever 205, 206 ... Permanent magnet 212 ... Coil 213 ... Yoke
305 ... strip-shaped permanent magnet 306 ... magnetic fluid 307 ... sealing plate
312, 313 ... Coil 213 ... Yoke 400 ... Shooting optical system 411 ... CCD 431 ... CPU
432: ND filter drive circuit 433 ... Shutter mechanism 434 ... Shutter drive circuit

Claims (10)

First and second optical members arranged in the optical axis direction;
A liquid layer formed between the first and second optical members,
An optical element characterized in that the thickness of the liquid layer in the optical axis direction changes as the first and second optical members move relative to each other in the direction perpendicular to the optical axis.   The optical axis thickness of the first optical member continuously increases in a specific direction among the orthogonal directions of the optical axis, and the optical axis thickness of the second optical member is continuous in the specific direction. The optical element according to claim 1, wherein   The optical element according to claim 1, wherein an optical axis direction interval between the light incident surface and the light exit surface of the optical element is unchanged. The first optical member is fixed in the optical axis orthogonal direction,
The optical element according to any one of claims 1 to 3, wherein the second optical member is movable in the direction perpendicular to the optical axis. In the first optical member, a liquid storage portion in which a liquid forming the liquid layer is stored is formed,
The optical element according to claim 1, wherein the second optical member is disposed in the liquid container. Two first optical members are arranged on both sides of the second optical member in the optical axis direction;
A first liquid layer is formed between one of the two first optical members and the second optical member, and the other first optical member and the second optical member are formed. The optical element according to any one of claims 1 to 5, wherein a second liquid layer is formed between the member and the member.   The optical element according to any one of claims 1 to 6, wherein the optical transmittance of the optical element changes due to a change in the thickness of the liquid layer in the optical axis direction. An optical element according to any one of claims 1 to 7,
An optical filter device comprising drive means for relatively driving the first and second optical members in the direction perpendicular to the optical axis.   An optical apparatus comprising the optical filter device according to claim 8 and comprising an imaging optical system for forming an object image. The optical apparatus according to claim 8, further comprising an image sensor that photoelectrically converts the object image.