JP2014074804A - Reflection optical element, reflection optical element array and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection optical element of a simple structure with a variable focal length, a reflection optical element array with a variable focal length in an arbitrary part within a reflection surface, and an imaging apparatus including the reflection optical element array.SOLUTION: A reflection optical element comprises: a mirror part 22; a frame part 23; a pair of hinge parts 24, 25 for rotatably supporting one end side of the mirror part 22 at the frame part 23; a movable mirror layer 2 having a pair of arm parts 26, 27 connected to two sides of the mirror part 22, respectively; and a substrate 3 arranged opposing to the movable mirror layer 2 across a space. The mirror part 22 rotates towards the substrate 3 by an external force with the same straight line extending the pair of hinge parts 24, 25 as a rotary shaft, and is deformed in concave through receiving, from the pair of arm parts 26, 27, a pulling force acting in a direction away from the substrate 3 at a movable end side.

Description

  The present invention relates to a reflective optical element having a variable focal length, a reflective optical element array in which a plurality of reflective optical elements are arranged, and an imaging apparatus including the reflective optical element array.

  In recent years, there has been proposed a light field camera (Light Field Camera) that can reconstruct an image at a different image plane position designated by a user from an image shot at a certain image plane position using a technique called light field photography (for example, , See Patent Document 1).

  In light field photography, a special optical system is disposed between an imaging optical system and a photoelectric conversion element. In one form of the light field camera, a microlens array is used as a special optical system, and light that passes through different areas of the aperture of the imaging optical system and converges on each microlens of the microlens array is a photoelectric conversion element. Are formed on different pixels.

  Since the direction of the light detected by each pixel of the photoelectric conversion element is known from the parameter information of the imaging optical system that is already known, an arbitrary focus image at the virtual image plane position set by the user is reproduced from the obtained imaging data. It is possible to configure. The range of the virtual image plane position that can be set by the user becomes wider as the number of pixels of the photoelectric conversion element for one microlens increases.

  However, in the conventional light field camera, the number of pixels (resolution) of the generated arbitrary focus image is equal to the number of microlenses of the microlens array, so the number of pixels of the arbitrary focus image is smaller than the number of pixels of the photoelectric conversion element. There was a problem that it was greatly reduced.

  On the other hand, if the number of microlenses is increased in order to suppress the decrease in the number of pixels (resolution) of the arbitrary focus image, the number of pixels (that is, the number of parallaxes) of the photoelectric conversion elements for one microlens decreases, so that a virtual that can be set There is a problem that the range of the image plane position becomes narrow.

  Therefore, coded imaging has been proposed as a method that does not use a microlens array as a special optical system (see, for example, Non-Patent Document 1). In coded imaging, as a special optical system, a diaphragm (coded diaphragm, coded aperture) in which a plurality of openings are opened according to a certain rule is used. When the coded aperture is used, the number of pixels does not decrease as in the case of using a microlens array, but the amount of light decreases because incident light passes through the aperture, and the SN ratio of the image deteriorates. Resulting in.

  Therefore, as a special optical system, a lattice focus lens has been proposed in which lenses each partially cut out from a plurality of lenses having different focal lengths are aligned (see, for example, Non-Patent Document 2).

  However, in a refocus camera using a conventional lattice focus lens disclosed in Non-Patent Document 2 or the like, an appropriate combination of lattice focus lenses must be used depending on the distance range of an object to be photographed. There were many combinations of lattice focus lenses, and they had to be changed according to the shooting scene, which was troublesome. Furthermore, since the refocus camera disclosed in Non-Patent Document 2 and the like has a mechanism for replacing the lattice focus lens, there is a problem that it is difficult to reduce the size of the apparatus.

  Therefore, instead of the lattice focus lens, a configuration using a reflective optical element that can partially change the optical characteristics of the reflecting surface is conceivable. As such an optical element, there is an adaptive optical element conventionally used in astronomy and the like, and in particular, a compact adaptive optical element using MEMS (Micro Electro Mechanical Systems) has been proposed in recent years.

  However, the conventional compensation optical element performs the shaping of the light wavefront by controlling the minute irregularities in the reflection surface of the plane reflecting mirror, and the focal distance is partially different from that of other places like a lattice focus lens. It does not take a very different state.

  On the other hand, the mirror element which rotates a plane reflective mirror centering | focusing on the hinge (torsion spring) provided in parallel with one side of the plane reflective mirror is proposed (for example, refer patent document 2). In this mirror element, the angle of the plane reflecting mirror can be arbitrarily displaced using electrostatic attraction or the like. Furthermore, it is conceivable to form a reflector array by closely arranging the mirror elements described above. Such a reflector array can take the structure of a Fresnel mirror, for example, by adjusting the angle of the reflector of each mirror element, and can also partially change the focal length.

  However, in the reflecting mirror array having the above configuration, the reflecting mirrors of the individual mirror elements are plane mirrors. Therefore, a large number of mirror elements are required to form a concave mirror with good characteristics as a whole, and the reflecting mirror array is large. There is a problem that it becomes complicated.

  The present invention has been made in view of the above problems, and includes a reflective optical element having a simple configuration and a variable focal length, a reflective optical element array having a variable focal length at an arbitrary portion within a reflective surface, and a reflective optical element. An object of the present invention is to provide an imaging device including an optical element array.

  In order to solve the above problems, a reflective optical element according to the present invention has a mirror part, a frame part, and a pair of hinge parts that pivotally support one end side of the mirror part on the frame part, and the mirror A reflective optical element comprising: a movable mirror layer that rotates about the same straight line in which the pair of hinge portions extend; and a substrate that is provided to face the movable mirror layer across a space. The movable mirror layer further includes a pair of arm portions respectively connected to both sides of the mirror portion between the outer edge of the mirror portion and the inner edge of the frame portion, and each of the arm portions includes: An extension part formed along a gap between an outer edge of the mirror part and an inner edge of the frame part, and an inner edge of the extension part and the frame part formed on the other end side of the mirror part with respect to the pair of hinge parts Connecting the first A connecting portion; and a second connecting portion that is formed on the other end side of the mirror portion with respect to the first connecting portion, and connects the extending portion and an outer edge of the mirror portion. Is rotated around the rotation axis toward the substrate side by an external force, and has a concave shape by receiving a pulling force acting on the other end side in a direction away from the substrate from the pair of arm portions. It is characterized by being deformed.

  With this configuration, the mirror portion rotates toward the substrate side by an external force, and is deformed into a concave shape by receiving a pulling force acting in a direction away from the substrate from the pair of arm portions. Can be realized.

  The present invention provides a reflective optical element having a simple configuration and a variable focal length, a reflective optical element array having a variable focal length of an arbitrary portion in a reflective surface, and an imaging apparatus including the reflective optical element array. It is.

The perspective view which shows the structure of the reflective optical element as the 1st Embodiment of this invention. 1 is an exploded perspective view showing a configuration of a reflective optical element as a first embodiment of the present invention. The top view which shows the structure of the movable mirror layer of the reflective optical element as the 1st Embodiment of this invention (A) is a perspective view for demonstrating operation | movement of the reflective optical element as the 1st Embodiment of this invention, (b) is AA sectional drawing of (a). (A) is a perspective view which shows the structural example of the electrode of the reflective optical element as the 1st Embodiment of this invention, (b) is a perspective view which shows the other structural example of an electrode. Sectional drawing which shows the manufacturing process of the reflective optical element as the 1st Embodiment of this invention (the 1) Sectional drawing which shows the manufacturing process of the reflective optical element as the 1st Embodiment of this invention (the 2) Sectional drawing which shows the manufacturing process of the reflective optical element as the 1st Embodiment of this invention (the 3) The perspective view which shows the structure of the reflective optical element array as the 2nd Embodiment of this invention. The partial perspective view which shows the structure of the reflective optical element array as the 2nd Embodiment of this invention. Sectional drawing which shows the structure of the imaging device as the 3rd Embodiment of this invention.

  Hereinafter, embodiments of a reflective optical element, a reflective optical element array, and an imaging apparatus according to the present invention will be described with reference to the drawings. In addition, the dimensional ratio of each structure on each drawing does not necessarily correspond with an actual dimensional ratio.

(First embodiment)
First, the configuration of the reflective optical element 1 as the first embodiment of the invention will be described. As shown in FIGS. 1 and 2, the reflective optical element 1 is provided so as to be opposed to the movable mirror layer 2 integrally formed by a micro electro mechanical systems (MEMS) technique with a space therebetween. A substrate 3 is mainly provided.

  Further, the reflective optical element 1 includes an insulating layer 4 made of a silicon oxide film and a conductive silicon layer 5 between the movable mirror layer 2 and the substrate 3. For example, the movable mirror layer 2, the insulating layer 4, and the silicon layer 5 made of a conductive silicon layer are configured by a three-layer SOI (Silicon on Insulator) substrate. The silicon layer 5 has a recess 6 (gap) for securing a movable space of the mirror portion 22 of the movable mirror layer 2. The movable mirror layer 2 and the silicon layer 5 are insulated from each other by the insulating layer 4.

  As shown in FIGS. 1 to 3, etc., the movable mirror layer 2 is formed with a reflective film 21 (not shown in FIG. 3) for reflecting light on at least one surface side, and a conductive substrate (for example, a silicon substrate). ) Comprising a mirror part 22, a frame part 23, and a pair of hinge parts 24, 25 for pivotally supporting one end side of the mirror part 22 on the frame part 23. The mirror unit 22 is configured to rotate about the same straight line from which the pair of hinge units 24 and 25 extend in accordance with the applied external force.

  In addition, the movable mirror layer 2 is located between the outer edge of the mirror part 22 and the inner edge of the frame part 23 on the other end side (hereinafter also referred to as a movable end) from the connecting part of the mirror part 22 and the pair of hinge parts 24 and 25. In this position, a pair of arm portions 26 and 27 are respectively connected to both sides of the mirror portion 22.

  As shown in FIG. 3, the frame portion 23 is formed in a trapezoidal frame shape, and includes a first horizontal plate 23a as an upper base, a second horizontal plate 23b as a lower base, and a first vertical plate as a leg. It consists of a plate 23c and a second vertical plate 23d.

  The hinge portion 24 is configured to connect the first vertical plate 23c and the mirror portion 22 closer to the second horizontal plate 23b than to the first horizontal plate 23a. On the other hand, the hinge portion 25 connects the second vertical plate 23d and the mirror portion 22 on the side closer to the second horizontal plate 23b than to the first horizontal plate 23a.

  The arm portion 26 has a first extending portion 26 a extending from the second horizontal plate 23 b side to the first horizontal plate 23 a side along the gap between the first vertical plate 23 c and the mirror portion 22, and is first than the hinge portion 24. Formed on the side closer to the horizontal plate 23a, the first connecting portion 26b connecting the extending portion 26a and the first vertical plate 23c, and closer to the first horizontal plate 23a than the first connecting portion 26b. And a second connecting portion 26 c that is formed and connects the extending portion 26 a and the mirror portion 22.

  On the other hand, the arm portion 27 has an extending portion 27 a extending from the second horizontal plate 23 b side to the first horizontal plate 23 a side along the gap between the second vertical plate 23 d and the mirror portion 22, and the hinge portion 25. Formed on the side closer to the first horizontal plate 23a, a first connecting portion 27b that connects the extending portion 27a and the second vertical plate 23d, and closer to the first horizontal plate 23a than the first connecting portion 27b And a second connecting portion 27 c that is formed on the side and connects the extending portion 27 a and the mirror portion 22.

  As already described, the pair of hinge portions 24 and 25 are formed so as to be aligned in a straight line (along the length direction of the second horizontal plate 23b). Similarly, the first connecting portions 26b and 27b are formed so as to be aligned on a straight line (along the length direction of the second horizontal plate 23b). The second connecting portions 26c and 27c are formed so as to be aligned on a straight line (along the length direction of the second horizontal plate 23b).

  Here, the pair of hinge portions 24, 25, the first connecting portions 26b, 27b, and the second connecting portions 26c, 27c function as torsion springs that themselves are torsionally deformed along their longitudinal directions, It has a width and a length so as to generate a restoring force for returning to its original state with respect to the deformation.

  When the mirror unit 22 is rotated toward the substrate 3 with the same straight line extending the pair of hinges 24 and 25 as a rotation axis in accordance with the applied external force, the movable end side of the mirror unit 22 is moved to the substrate. The pair of arm portions 26 and 27 receive a pulling force acting in a direction away from 3. As shown in FIG. 4A, the entire mirror portion 22 warps in a concave shape (convex downward) due to the balance of the restoring force, the external force, and the pulling force.

  Hereinafter, the configuration and operation when electrostatic attraction is used as the external force applied to the mirror unit 22 will be described. As shown in FIG. 4B, the reflective optical element 1 is connected to a mirror driving device 10 that applies electrostatic attraction to the mirror portion 22 of the movable mirror layer 2.

  Here, as shown in FIG. 4B, the angle formed by the one end side of the mirror portion 22 with respect to the vertical direction is defined as θ. The rotation angle θ (displacement amount) of the mirror part 22 is determined by the magnitude of the external force, the torsion spring constant of the pair of hinge parts 24 and 25, and the torsion spring constant of each connecting part of the pair of arm parts 26 and 27.

  Note that the curvature of the mirror portion 22 at a certain rotation angle θ adjusts, for example, the joining position between the first and second connecting portions 26b, 26c, 27b, and 27c of the pair of arm portions 26 and 27 and the frame portion 23. Therefore, it can be set arbitrarily.

  As shown in FIG. 5, an electrode 31 for applying an electrostatic attractive force as an external force to the movable mirror layer 2 is formed on the upper surface of the substrate 3 via an insulating film (not shown). The electrode 31 may be made of a single metal film, or may be made of a plurality of divided electrodes.

  FIG. 5A shows an example in which the electrode 31 is a single electrode. The electrode 31 has an extraction wiring 32 for electrically connecting the mirror driving device 10 and the electrode 31. FIG. 5B illustrates an example in which the electrode 31 includes a plurality of divided electrodes 31a to 31d divided in a direction orthogonal to the rotation axis. The divided electrodes 31a to 31d have lead wires 32a to 32d for being electrically connected to the mirror driving device 10, respectively.

  Here, the lead wires 32a to 32d shown in FIG. 5B are electrically separated by other lead wires and divided electrodes other than the corresponding divided electrodes 31a to 31d by an insulating layer (not shown). Has been. With this configuration, each of the divided electrodes 31a to 31d can be energized independently.

  FIG. 5B shows an example in which the number of divisions (the number of divided electrodes) when the electrode 31 is divided into a plurality of parts is four, but the number of divisions is not limited to four. Any number of 2 or more may be used as necessary.

  The mirror driving device 10 shown in FIG. 4B applies the voltage between the electrode 31 formed on the upper surface of the substrate 3 and the mirror part 22 of the movable mirror layer 2, thereby causing the electrode 31 and the mirror part to be applied. The mirror portion 22 is displaced by generating an electrostatic attractive force between the mirror portion 22 and the mirror portion 22 toward the substrate 3 on which the electrode 31 is formed.

  FIG. 4B shows an example in which the mirror driving device 10 applies a negative potential to the electrode 31 and applies a positive potential to the mirror unit 22. On the contrary, the mirror driving device 10 may apply a positive potential to the electrode 31 and apply a negative potential to the mirror unit 22. Alternatively, the mirror driving device 10 may apply a positive potential or a negative potential to the electrode 31 with the potential of the mirror unit 22 as a reference potential (ground potential).

  Generally, the voltage applied between the opposing electrodes is large, and the electrostatic attraction force increases as the opposing electrode area increases. For this reason, in the initial state where the applied voltage is zero and the mirror portion 22 and the electrode 31 are largely separated (for example, the state where the reflective optical element 1 is a plane mirror), the area of the electrode 31 is increased in order to generate a large electrostatic attraction. It is advantageous to do so. Therefore, when the electrode 31 includes a plurality of divided electrodes 31a to 31d, it is preferable that a voltage is applied to as many divided electrodes 31a to 31d as possible.

Next, the operation of the reflective optical element 1 of the present embodiment will be described.
When a voltage is applied between the mirror unit 22 of the movable mirror layer 2 and the electrode 31 formed on the upper surface of the substrate 3 by the mirror driving device 10 via a wiring (not shown), the mirror unit 22 and the electrode Due to the electrostatic attractive force generated between the mirror portions 22, the mirror portion 22 is rotated around the rotation axis of the pair of hinge portions 24, 25 and is pulled toward the substrate 3 side.

  In order to continue to displace the mirror unit 22, a voltage is continuously applied from the mirror driving device 10. However, if the displacement of the mirror unit 22 increases and the distance between the mirror unit 22 and the electrode 31 decreases, the mirror unit 22 The electrostatic attractive force for maintaining the displacement may be smaller than the initial displacement. Therefore, when the electrode 31 includes a plurality of divided electrodes 31a to 31d, it is necessary to hold the displacement of the mirror portion 22 by stopping the voltage application to some of the divided electrodes 31a to 31d. It is possible to reduce energy.

  When the mirror part 22 rotates as described above, the movable end side of the mirror part 22 receives a pulling force acting in a direction away from the substrate 3 from the pair of arm parts 26 and 27. The mirror portion 22 warps in a concave shape (convex downward) by the electrostatic attraction and the pulling force.

  Here, by adjusting the magnitude of the voltage applied between the mirror unit 22 and the electrode 31 by the mirror driving device 10, a desired rotation angle θ (displacement amount) and curvature of the mirror unit 22 can be obtained. It becomes possible.

  Furthermore, when the electrode 31 includes a plurality of divided electrodes 31a to 31d, the voltage applied to the plurality of divided electrodes 31a to 31d is appropriately set for each divided electrode, thereby controlling the curvature of the mirror unit 22. It is possible. Further, by adjusting the joining position of the first and second connecting portions 26b, 26c, 27b, 27c of the pair of arm portions 26, 27 and the frame portion 23, the mirror portion 22 at a certain tilt angle (rotation angle). It is possible to set the curvature.

  In addition, when the displacement of the mirror part 22 becomes large, it is possible that the movable end of the mirror part 22 contacts the electrode 31 or the substrate 3. When the mirror unit 22 and the electrode 31 are in contact with each other when a voltage is applied, the electrical circuit of the mirror driving device 10 is short-circuited and the mirror unit 22 is damaged. In order to prevent such contact between the mirror portion 22 and the electrode 31, it is conceivable to make the movable electrode 31 small. In this case, there is a concern that the electrostatic attractive force is insufficient in the initial stage of the movement.

  Therefore, if the electrode 31 is composed of a plurality of divided electrodes 31a to 31d as in the present embodiment, all the divided electrodes 31a to 31d are used when a large electrostatic attraction is required, and the displacement of the mirror portion 22 is changed. When becomes sufficiently large, for example, energization to the divided electrode (for example, divided electrode 31d) in the vicinity of the movable end of the mirror portion 22 can be stopped, and the other divided electrodes can be used. Thereby, the mirror part 22 can be continuously displaced safely with little energy.

Hereinafter, a method for manufacturing the reflective optical element 1 configured as described above will be described.
The movable mirror layer 2 is formed by etching a silicon substrate or the like, but the manufacturing method is arbitrary. First, a three-layer substrate such as an SOI substrate 40 as shown in FIG. The SOI substrate 40 used here has two silicon layers 42 and 45 sandwiching an insulating layer 44 and has a trapezoidal columnar shape. For example, the silicon layers 42 and 45 are made of single crystal silicon having thicknesses of 40 μm and 210 μm, respectively. The insulating layer 44 is made of silicon oxide (for example, SiO ₂ ) having a thickness of 0.2 μm.

  Next, as shown in FIG. 6B, the reflective film 21 is formed at a predetermined position on the upper surface of one silicon layer 42 (generally called an active layer) of the SOI substrate 40. As the reflective film 21, a metal such as gold or aluminum is generally used.

  Next, as shown in FIG. 6C, an etching mask 41 is formed on the upper surface of the silicon layer 42 by photolithography. The mask 41 includes a pattern for forming the frame portion 23, the pair of hinge portions 24 and 25, and the pair of arm portions 26 and 27 in addition to the pattern for forming the mirror portion 22.

  Next, as shown in FIG. 6D, processing along the mask 41 is performed by dry etching. Etching proceeds to the insulating layer 44 which is a silicon oxide layer, where the insulating layer 44 becomes an etching stop layer and the etching stops. By this etching, the movable mirror layer 2 having the mirror part 22, the frame part 23, the pair of hinge parts 24 and 25, and the pair of arm parts 26 and 27 is formed.

  Next, as shown in FIG. 7 (5), the SOI substrate 40 is turned upside down, and a mask for forming a gap in the silicon layer 45 which is a thick silicon single crystal (generally called a support substrate) having a thickness of 210 μm. 43 is formed.

  Next, as shown in FIG. 7 (6), processing along the mask 43 is performed by dry etching. Since the insulating layer 44 that is a silicon oxide layer functions as an etching stop layer, the etching stops at the insulating layer 44. By this etching, the silicon layer 5 having a gap for securing the movable space of the mirror portion 22 is formed.

  Next, as shown in FIG. 7 (7), using buffered hydrofluoric acid or the like, the insulating layer 44 that is a silicon oxide layer is removed except for the portion sandwiched between the movable mirror layer 2 and the silicon layer 5. . By this etching, the insulating layer 4 that insulates the movable mirror layer 2 and the silicon layer 5 from each other is formed, and the concave portion 6 for securing the movable space of the mirror portion 22 is formed.

  Next, as shown in FIG. 8 (8), an insulating film (not shown) is formed on the substrate 3 which is a single crystal silicon wafer having a thickness of 500 μm, for example, and then a driving electrode 31 is formed.

  Finally, as shown in FIG. 8 (9), the reflective optical element 1 is completed by bonding the SOI substrate shown in FIG. 7 (7) and the substrate shown in FIG. 8 (8).

  In the above description, the manufacturing process has been described with one reflecting optical element 1 shown in the figure. However, in practice, a plurality of reflecting optical elements are formed in a single process using a photolithography mask on which a plurality of reflecting optical element patterns are formed. The reflective optical elements can be formed simultaneously. That is, the reflective optical element array described in the second embodiment can be formed in a single process.

  As described above, in the reflective optical element 1 according to the present embodiment, the mirror unit 22 rotates toward the substrate 3 side by an external force, and the pulling force acting in the direction away from the substrate 3 is applied to the pair of arm units. Since it is deformed into a concave shape by receiving from 26 and 27, the focal length can be made variable with a simple configuration.

  Further, in the reflective optical element 1 according to the present embodiment, the movable mirror layer 2 (the mirror part 22, the frame part 23, the pair of hinge parts 24 and 25, and the pair of arm parts 26 and 27) is provided on the SOI substrate 40 with the MEMS technology. Therefore, the shape of the pair of hinge portions 24 and 25 and the pair of arm portions 26 and 27 can be accurately formed, and the pair of hinge portions 24 and 25 and the pair of arm portions 26 and 27 can be formed accurately. It is possible to arbitrarily set the position of each connecting part.

  In the above description, the movable mirror layer 2 is integrally formed by the MEMS technique. However, the mirror part 22, the frame part 23, the pair of hinge parts 24 and 25, and the pair of arm parts 26 and 27 are separately provided. It may be formed.

  In the above description, the movable mirror layer 2 is conductive. However, the movable mirror layer 2 may be made of a material having no conductivity. In this case, if the reflective film 21 is a conductive metal film, an electrostatic attractive force between the electrode 31 and the mirror part 22 can be secured.

  In the above description, the external force applied to the mirror unit 22 is electrostatic attraction. However, when the movable mirror layer 2 is made of a magnetic material, the external force applied to the mirror unit 22 is magnetic. It may be power. For example, an electromagnet having an electromagnet core, a spiral thin film coil, and a lead wire drawn from the thin film coil is formed on the substrate 3 instead of the electrode 31 as a configuration for applying the magnetic force to the mirror portion 22. Thus, a configuration in which the mirror driving device 10 supplies a current for generating a magnetic field to the electromagnet through the lead wiring is conceivable.

  In the above description, the shape of the reflective optical element 1 is a trapezoidal column, but the shape of the reflective optical element 1 is, for example, the first horizontal plate 23a and the second horizontal plate 23b are arcuate. A fan-like shape may be used.

(Second Embodiment)
Next, a reflective optical element array as a second embodiment of the present invention will be described with reference to the drawings. Note that the description of the same configuration and operation as in the first embodiment will be omitted as appropriate.

  The reflective optical element array 100 of the present embodiment is formed by arranging a plurality of reflective optical elements 1 of the first embodiment in an array. As shown in FIG. 9, the reflective optical element array 100 is configured by arranging trapezoidal columnar reflective optical elements 1 in, for example, concentric circles. In addition, it is desirable that the center mirror 7 on a planar or concave surface is disposed at the center of the reflective optical element array 100 so as to contact the first horizontal plate 23a of the reflective optical element 1 closest to the center.

  FIG. 9A shows a state where all the reflective optical elements 1 constituting the reflective optical element array 100 are parallel to the surface of the substrate 3. In this state, the focal lengths of all the reflective optical elements 1 are infinite, and the reflective optical element array 100 functions as a plane mirror as a whole.

  FIG. 9B shows a configuration in which the reflecting surface of each reflecting optical element 1 (the surface on which the reflecting film 21 of the mirror portion 22 is formed) is deformed into a concave shape with an arbitrary curvature by an external force. For example, among the plurality of reflective optical elements 1 shown in FIG. 9B, two reflective optical elements indicated by arrows correspond to part of concave mirrors having different focal lengths A and B, respectively.

  As described above, since the mirror portion 22 of each reflective optical element 1 constituting the reflective optical element array 100 is formed of a part of a concave mirror having a different focal length, the reflective optical element array 100 has a partial focal length. It functions as a variable concave mirror. As an example, the reflective optical element array 100 may be configured as a Fresnel mirror.

  FIG. 10 is a partial perspective view showing a part of FIG. 9B in an enlarged manner. As described above, the pivoting about the pair of hinge parts 24 and 25 and the pulling of the pair of arm parts 26 and 27 cause the concave deformation in the mirror part 22 of each reflective optical element 1. The mirror part 22 constitutes a part of the concave mirror. As a result, it is possible to form a reflective optical element array with higher accuracy with a smaller number of reflective optical elements than in the conventional configuration in which each mirror section 22 is a plane mirror.

  The reflective optical element array 100 of the present embodiment configured as described above can arbitrarily change the focal length of the reflective optical element 1 at an arbitrary position. Therefore, the reflective optical element array 100 according to the present embodiment is applied to the refocus camera described in the third embodiment instead of the lattice focus lens disclosed in Non-Patent Document 2, so that a conventional lattice can be obtained. In addition to exhibiting the same optical function as that of the focus lens, it is possible to configure an optical system suitable for image processing corresponding to changes in the shooting scene.

  Furthermore, by applying the reflective optical element array 100 of this embodiment to a refocus camera, a lens replacement mechanism or the like in a conventional refocus camera using a lattice focus lens becomes unnecessary, and thus the refocus camera is downsized. It becomes possible to do.

(Third embodiment)
Next, an imaging apparatus as a third embodiment of the present invention will be described with reference to the drawings. Note that description of the configuration and operation similar to those of the first and second embodiments will be omitted as appropriate.

  As shown in FIG. 11, the imaging apparatus 200 according to the present embodiment is a refocus camera such as a light field camera, and the imaging element 51 and light rays from an imaging target (object) are captured in the casing 50 by the imaging element 51. Lens groups 52 and 53 as imaging lenses for condensing and forming an image on the light receiving surface, the reflective optical element array 100 of the second embodiment, and the light from the lens group 52 toward the reflective optical element array 100 A half mirror 54 that reflects the reflected light modulated by the reflective optical element array 100 toward the lens group 53, and a control unit 55.

  The reflective optical element array 100 functions as an optical element that transmits light from the lens group 52 to the imaging element 51. The image pickup device 51 includes an imager such as a CCD sensor or a CMOS sensor having a plurality of pixels that receive light from the lens groups 52 and 53.

  The control unit 55 includes, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), and a CPU (Central Processing Unit), and performs image stabilization, zoom, exposure and focus control, noise reduction, image Functions such as configuration are implemented. Furthermore, the control unit 55 controls the focal length of each reflective optical element 1 constituting the reflective optical element array 100.

Next, the operation of the imaging apparatus 200 of this embodiment will be described.
Light emitted from an imaging target (not shown) is collected by the lens group 52 and guided to the half mirror 54. The light that has passed through the half mirror 54 is guided to the reflective optical element array 100, and the reflected light that has been modulated by the reflective optical element array 100 is guided to the half mirror 54 again.

  At this time, when the control unit 55 sets the focal length of each reflective optical element 1 of the reflective optical element array 100 to infinity, and causes the reflective optical element array 100 to function as a plane mirror, the imaging apparatus 200 has a normal camera optical system. Become. On the other hand, when the control unit 55 changes the focal length of each reflective optical element 1 of the reflective optical element array 100 according to the shooting scene, the reflective optical element array 100 has an optical function equivalent to that of the lattice focus lens. The imaging apparatus 200 is a light field optical system suitable for a shooting scene.

  The light reflected by the half mirror 54 is received by the image sensor 51 and converted into image information. The control unit 55 acquires light field information to be imaged from this image information and modulation information of the reflective optical element array 100 (information such as the focal length of each reflective optical element 1).

  The control unit 55 may generate a plurality of focus images from the acquired light field information, or may output the acquired light field information to an external processing device.

  As described above, the imaging apparatus 200 according to the present embodiment is a reflection mirror according to the present invention in which a part of a surface that receives light from the imaging lens (lens groups 52 and 53) is a concave mirror whose focal length can be arbitrarily changed. Since the optical element array 100 is provided, arbitrary-focus images with different image plane positions can be obtained with high resolution.

  Therefore, the imaging apparatus 200 of the present embodiment not only exhibits the same function as a refocus camera having a lattice focus lens as disclosed in Non-Patent Document 2, but also performs image processing corresponding to changes in the shooting scene. Can be performed.

  Furthermore, the imaging apparatus 200 of the present embodiment does not require a lens replacement mechanism or the like in a refocus camera using a conventional lattice focus lens, and thus the entire apparatus can be reduced in size.

DESCRIPTION OF SYMBOLS 1 Reflective optical element 2 Movable mirror layer 3 Substrate 4 Insulating layer 5 Silicon layer 6 Concave part 7 Center mirror 10 Mirror drive device 21 Reflecting film 22 Mirror part 23 Frame part 23a 1st horizontal board 23b 2nd horizontal board 23c 1st Vertical plate 23d Second vertical plate 24, 25 (Pair) Hinge part 26, 27 (Pair) Arm part 26a, 27a Extension part 26b, 27b First connection part 26c, 27c Second connection part 31 Electrode 31a -31d Divided electrode 32, 32a-32d Lead wiring 40 SOI substrate 41 Mask 42, 45 Silicon layer 43 Mask 44 Insulating layer 50 Housing 51 Imaging element 52, 53 Lens group (imaging lens)
54 Half mirror 55 Control unit 100 Reflective optical element array 200 Imaging device

JP 2009-244661 A JP-T-2006-526806

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Claims (7)

The mirror portion, the frame portion, and the frame portion have a pair of hinge portions that pivotally support one end side of the mirror portion, and the mirror portion rotates on the same straight line on which the pair of hinge portions extend. A movable mirror layer that rotates as
A reflective optical element comprising a substrate provided opposite to the movable mirror layer with a space therebetween,
The movable mirror layer further includes a pair of arm portions respectively connected to both sides of the mirror portion between the outer edge of the mirror portion and the inner edge of the frame portion,
Each said arm part is
An extending portion formed along the gap between the outer edge of the mirror portion and the inner edge of the frame portion;
A first connecting part that is formed on the other end side of the mirror part from the pair of hinge parts, and connects the extending part and the inner edge of the frame part;
A second connecting part that is formed on the other end side of the mirror part from the first connecting part, and connects the extending part and an outer edge of the mirror part;
The mirror portion rotates about the rotation axis toward the substrate side by an external force, and receives a pulling force acting in a direction away from the substrate on the other end side from the pair of arm portions. A reflective optical element that is deformed into a concave shape. The movable mirror layer has conductivity, and an electrode electrically insulated from the movable mirror layer is formed on the substrate.
The external force is an electrostatic attractive force generated between the electrode and the movable mirror layer when a voltage is applied between the electrode and the movable mirror layer. Reflective optical element.   The reflective optical element according to claim 2, wherein the electrode includes a plurality of divided electrodes divided in a direction orthogonal to the rotation axis. The movable mirror layer has magnetism,
The reflective optical element according to claim 1, wherein the external force is a magnetic force applied to the movable mirror layer.   The reflective optical element according to any one of claims 1 to 4, wherein the mirror part, the frame part, the pair of hinge parts, and the pair of arm parts are integrally formed.   A plurality of reflective optical elements according to any one of claims 1 to 5 are arranged in an array, and the mirror portion of each reflective optical element is deformed into a concave shape with an arbitrary curvature by the external force. Thus, the reflective optical element array functions as a concave mirror whose focal length is partially variable. An imaging device that captures an image for generating a plurality of focus images of an object,
An imaging lens for condensing light from the object;
An imaging device including a plurality of pixels that receive light from the imaging lens;
An optical element that transmits light from the imaging lens to the imaging element,
The imaging apparatus according to claim 6, wherein the optical element is a reflective optical element array according to claim 6.