Magnetic circuit type mirror drive unit

Abstract

To provide a magnetic circuit type mirror driving device capable of obtaining a uniform magnetic field with high magnetic flux density in a magnetic gap without arranging a magnet on an upper portion of a mirror.SOLUTION: A magnetic circuit type mirror driving device includes: a first magnet 12 arranged on a lower yoke 11 with a center pole 11a; a first upper yoke 13 provided on the first magnet; a second magnet 15 arranged on the lower yoke separately from the center pole farther than the first magnet and having higher magnetomotive force than that of the first magnet; and a second upper yoke 16 provided on the second magnet. A magnetic gap is formed between the first and second upper yokes and the center pole, and a mirror is driven by electromagnetic action of a coil portion 14 arranged in the magnetic gap.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic circuit type mirror driving device that generates a magnetic field for driving, for example, a MEMS mirror. [Background technology]

[0002] Patent document 1 describes a magnetic drive system in which two sets of magnets (yokes) are arranged above and below a silicon chip (MEMS mirror) on which a coil section and a mirror section are formed, so that magnetic flux repels each other, thereby obtaining a uniform magnetic flux. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2010 / 0141366 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration of Patent Document 1, the magnet is placed above the mirror section (placed inside the coil section), which blocks the incident light beam and restricts the optical path, which is a problem. In addition, there are problems such as the device becoming larger because the magnet is placed above the mirror section, and the upper magnet must be placed with the same polarity as the lower magnet, which generates a repulsive force and increases the size of the device for fixing.

[0005] The present invention was made in consideration of the above circumstances, and its purpose is to provide a magnetic circuit type mirror drive device that can obtain a uniform magnetic field with high magnetic flux density within the magnetic gap without placing a magnet above the mirror. [Means for solving the problem]

[0006] A magnetic circuit type mirror drive device according to one aspect of the present invention comprises a first magnet arranged on a lower yoke with a center pole, a first upper yoke provided on the first magnet, a second magnet arranged on the lower yoke at a greater distance from the center pole than the first magnet and having a stronger magnetomotive force than the first magnet, and a second upper yoke provided on the second magnet; The first upper yoke and the second upper yoke are in contact with each other. A magnetic gap is formed between the yoke and the center pole, and a coil is placed in the magnetic gap. Department The electromagnetic effect of the mirror Department The present invention is characterized by driving the [Effects of the Invention]

[0007] In this invention, a second magnet with a stronger magnetomotive force is placed outside the lower yoke with a center pole, and a second upper yoke is placed extending from the top surface of the second magnet to form a magnetic gap between the center pole. The high magnetic flux from the added second magnet is guided to the magnetic gap by the second upper yoke, where it is combined with the magnetic flux from the first upper yoke and guided to the magnetic gap. As a result, the magnetic flux in the magnetic gap is oriented substantially horizontally, and the magnetic flux density is also increased, making it possible to obtain a uniform magnetic field with high magnetic flux density in the magnetic gap. Therefore, according to the present invention, it is possible to provide a magnetic circuit type mirror driving device that can obtain a uniform magnetic field with a high magnetic flux density within the magnetic gap without placing a magnet above the mirror. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a main part of a magnetic circuit type mirror drive device according to an embodiment of the present invention. [Figure 2] 1 is a perspective view showing a schematic configuration of a magnetic circuit type mirror drive device according to a first embodiment of the present invention. [Figure 3] FIG. 3 is an exploded view of the magnetic circuit type mirror drive device shown in FIG. 2. [Figure 4] 3 is a perspective view of the magnetic circuit type mirror drive device shown in FIG. 2, cut along line X1-X1'. FIG. [Figure 5]3 is a perspective view of the magnetic circuit type mirror drive device shown in FIG. 2, cut along line X2-X2'. FIG. [Figure 6] 3 is a perspective view of the magnetic circuit type mirror drive device shown in FIG. 2, cut along line X3-X3'. FIG. [Figure 7] FIG. 10 is a perspective view showing a schematic configuration of a magnetic circuit type mirror drive device according to a second embodiment of the present invention. [Figure 8] FIG. 8 is an exploded view of the magnetic circuit type mirror drive device shown in FIG. [Figure 9] 8 is a perspective view of the magnetic circuit type mirror drive device shown in FIG. 7, cut along line Z1-Z1'. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of the main components of a magnetic circuit-type mirror drive device according to an embodiment of the present invention. In this invention, a magnet is added to a conventional magnetic circuit, and an overhead (above-chip) yoke is used to create a horizontal, uniform, and strong magnetic flux in the magnetic gap. Specifically, a first magnet 12 is disposed on a lower yoke 11 with its south pole facing downward and its north pole facing upward. A center pole 11a is erected on this lower yoke 11. A first upper yoke 13 is disposed on the north pole of the first magnet 12. The first upper yoke 13 has a rising portion 13a bent upward facing the center pole 11a, and a coil portion 14 is disposed in the magnetic gap formed between this rising portion 13a and the center pole 11a.

[0010] The second magnet 15, which has a stronger magnetomotive force than the first magnet 12, is positioned on the lower yoke 11 farther from the center pole 11a than the first magnet 12, with its magnetic poles oriented in the same direction as the first magnet 12. A second upper yoke 16 is provided on the second magnet 15. The second upper yoke 16 extends from the upper surface of the second magnet 15 to the top of a chip (part of the MEMS mirror) 17 and is positioned so as to contact the rising portion 13a of the first upper yoke 13. The chip 17 is provided at a position corresponding to the first magnet 12 between the first upper yoke 13 and the second upper yoke 16 and is connected by wire bonding or the like to a wiring layer formed on a flexible substrate. The chip 17 acts as a bridge, receiving a drive signal from the flexible substrate via a bonding wire and passing it to the coil portion 14 disposed in the magnetic gap. The MEMS mirror (not shown) is driven by the electromagnetic action of the coil portion 14.

[0011] Normally, it is desirable for the magnetic flux in the magnetic gap to be horizontal and uniform, and for the force obtained by the coil to be only a vertical force. If the magnetic flux is not horizontal, it means that the magnetic flux contains vertical components, which generates unnecessary horizontal forces (according to Fleming's left-hand rule).

[0012] In the above configuration, as shown by the arrows, a closed magnetic path is formed from the north pole of the first magnet 12 back to the south pole of the first upper yoke 13, the rising portion 13a, the center pole 11a, the lower yoke 11, and the first magnet 12. Also, a closed magnetic path is formed from the north pole of the second magnet 15 back to the second upper yoke 16, the rising portion 13a, the center pole 11a, the lower yoke 11, and the second magnet 15. Here, the high magnetic flux from the second magnet 15 is guided to the magnetic gap by the second upper yoke 16 and combined with the magnetic flux from the first upper yoke 13.

[0013] As a result, the magnetic flux in the magnetic gap is oriented substantially horizontally, and the magnetic flux density is also increased, making it possible to obtain a uniform magnetic field with high magnetic flux density in the magnetic gap. In addition, in the above configuration, blocking of the optical path (reducing restrictions on the angle of incidence, etc.) can be avoided because no magnet is placed above the chip 17. Furthermore, because there is no need to place a magnet above the mirror section, the device does not become larger, and the device for fixing it due to the repulsive force does not become larger.

[0014] [First embodiment] Fig. 2 shows the schematic configuration of a magnetic circuit type mirror drive device according to a first embodiment of the present invention, which is a type having four center poles. Fig. 3 is an exploded view of the magnetic circuit type mirror drive device shown in Fig. 2, Fig. 4 is a perspective view of the magnetic circuit type mirror drive device shown in Fig. 2 cut along line X1-X1', Fig. 5 is a perspective view cut along line X2-X2', and Fig. 6 is a perspective view cut along line X3-X3'. 1 corresponds to a cross section taken along line Y1-Y1' in FIG.

[0015] 2 to 6, lower yoke 11 is configured with first to fourth columnar members serving as center poles erected in a square shape in the center of a rectangular plate, with opening 11e formed between center poles 11a, 11b and center poles 11c, 11d. Center poles 11a and 11b are connected at their bases by connecting portion 11m, and center poles 11c and 11d are connected at their bases by connecting portion 11n. Circular through-holes 11f, 11g, and 11h, and through-holes 11i, 11j, and 11k, which serve as mounting holes, are provided at both ends of the rectangular plate.

[0016] The first magnet 12 is rectangular and has a width approximately equal to that of the lower yoke 11. The first magnet 12 is frame-shaped with an opening 12a formed in the center to surround the center poles 11a, 11b, 11c, and 11d. The bottom surface of the first magnet 12 has an S pole and the top surface has an N pole. The first upper yoke 13 is formed from a plate with a length and width approximately equal to that of the first magnet 12. The plate has an opening 13e in the center and rising portions 13a, 13b, 13c, and 13d that bend upward from the periphery of the opening 13e to face the center poles 11a, 11b, 11c, and 11d. Magnetic gaps are formed in the gaps between these rising portions 13a, 13b, 13c, and 13d and the center poles 11a, 11b, 11c, and 11d. Moreover, around the opening 13e of the first upper yoke 13, protrusions 13f, 13g, 13h, and 13i for mounting a MEMS mirror (chip) 17 are provided.

[0017] The second and third magnets 15-1 and 15-2 are arranged on the lower yoke 11, horizontally sandwiching the first magnet 12 and the first upper yoke 13. Here, the second magnet 15-1 corresponds to the second magnet 15 in FIG. 1 described above. The second and third magnets 15-1 and 15-2 have a stronger magnetomotive force than the first magnet 12, and have through holes 15a, 15b, 15c and through holes 15d, 15e, and 15f corresponding to the circular through holes 11f, 11g, and 11h and through holes 11i, 11j, and 11k of the lower yoke 11, respectively.

[0018] The MEMS mirror 17 is formed by forming metal coils 14a, 14b, 14c, and 14d and a mirror portion 17a on a single-crystal silicon chip using MEMS (Micro Electro Mechanical Systems) processing technology. While simplified in the figure, the MEMS mirror 17 is comprised of a fixed outer frame support, an outer rotating body also called a movable inner frame, and an inner rotating body called a movable plate. The coils 14a, 14b, 14c, and 14d are arranged to surround the center poles 11a, 11b, 11c, and 11d, respectively. The mirror portion 17a is configured to be biaxially scannable by being driven in the X-axis and Y-axis directions. The MEMS mirror 17 is attached to the protrusions 13f, 13g, 13h, and 13i of the first upper yoke 13 via mounting holes 17b, 17c, 17d, and 17e.

[0019] A driving device 18 is connected to the MEMS mirror 17. The driving device 18 is, for example, a flexible substrate, and a driving signal for the coil portions 14a, 14b, 14c, and 14d is supplied from another circuit through the driving device 18. When the driving signal is supplied, the mirror portion 17a is driven in the X-axis and Y-axis directions by electromagnetic action of the coil portions 14a, 14b, 14c, and 14d, which are arranged in the magnetic gaps between the rising portions 13a, 13b, 13c, and 13d and the center poles 11a, 11b, 11c, and 11d, thereby performing biaxial scanning. The driving device 18 may be a semiconductor integrated circuit device or the like, in which case the driving signal is generated directly by the driving device 18.

[0020] The second upper yoke 16 has a width approximately equal to that of the lower yoke 11 and a rectangular shape with a convex upward central portion. The second upper yoke 16 is installed so as to cover the second and third magnets 15-1 and 15-2, the first upper yoke 13, and the drive device 18. An opening 16a is formed in the center of the second upper yoke 16, surrounding the center poles 11a, 11b, 11c, and 11d. The opening 16a exposes the coil portions 14a, 14b, 14c, and 14d and the mirror portion 17a. Furthermore, through holes 16b, 16c, and 16d and through holes 16e, 16f, and 16g are formed at positions corresponding to the through holes 15a, 15b, and 15c and the through holes 15d, 15e, and 15f of the second and third magnets 15-1 and 15-2, respectively.

[0021] With the above configuration, second and third magnets 15-1 and 15-2, which have higher magnetomotive force, are placed outside lower yoke 11, and second upper yoke 16 is extended above them to rising portions 13a, 13b, 13c, and 13d of first upper yoke 13 to form a magnetic gap, which allows higher magnetic flux from second and third magnets 15-1 and 15-2 to be guided into the magnetic gap. As a result, the magnetic flux of coil portions 14a, 14b, 14c, and 14d in the magnetic gap is oriented horizontally, and the magnetic flux density is also high, making it possible to obtain a uniform (oriented horizontally, constant within the gap) magnetic field with high magnetic flux density within the magnetic gap without placing magnets above the mirror.

[0022] [Second embodiment] Fig. 7 shows the schematic configuration of a magnetic circuit type mirror drive device according to a second embodiment of the present invention, which is a type with a single center pole. Fig. 8 is an exploded view of the magnetic circuit type mirror drive device shown in Fig. 7, and Fig. 9 is a perspective view of the magnetic circuit type mirror drive device shown in Fig. 7 cut along line Z1-Z1'. The basic configuration of this second embodiment is the same as that of the first embodiment, with a second magnet with a stronger magnetomotive force than the first magnet positioned on the outside, and a second upper yoke placed above it to extend the upper part of the chip and form a magnetic gap. 1 corresponds to a cross section taken along line Y2-Y2' in FIG.

[0023] As shown in Figures 7 to 9, the lower yoke 21 is a rectangular plate material with a center pole 21a erected in the center and circular through holes 21b, 21c, 21d, 21e, 21f and through holes 21g, 21h, 21i, 21j, 21k at both ends, which serve as mounting holes.

[0024] The first magnet 22-1 and the third magnet 22-2 are each formed of an L-shaped member in a planar shape and are arranged so that the center pole 21a is sandwiched between their respective bent portions. The first magnet 22-1 corresponds to the first magnet 12 in FIG. 1 described above. The first magnet 22-1 has an S pole on the bottom side and an N pole on the top side, while the third magnet 22-2 has an N pole on the bottom side and an S pole on the top side. The first upper yokes 23-1 and 23-2 have planar shapes substantially identical to those of the first and third magnets 22-1 and 22-2 and have rising portions 23a and 23b that rise upward facing the center pole 21a. A magnetic gap is formed between the rising portions 23a and 23b and the center pole 11a. The first upper yokes 23-1 and 23-2 also have protruding portions 23c, 23d, 23e, and 23f, respectively, for mounting the MEMS mirror 27.

[0025] The second and fourth magnets 25-1 and 25-2 are arranged on the lower yoke 21, horizontally sandwiching the first and third magnets 22-1 and 22-2 and the first upper yokes 23-1 and 23-2. Here, the second magnet 25-1 corresponds to the second magnet 15 in Fig. 1 described above. The second magnet 25-1 has an S pole on the bottom surface and an N pole on the top surface, and the fourth magnet 25-2 has an N pole on the bottom surface and an S pole on the top surface. The second and fourth magnets 25-1 and 25-2 have higher magnetomotive forces than the first and third magnets 22-1 and 22-2, respectively, and have through holes 25a, 25b, 25c, 25d, 25e and through holes 25f, 25g, 25h, 25i, and 25j corresponding to the circular through holes 21b, 21c, 21d, 21e, and 21f and through holes 21g, 21h, 21i, 21j, and 21k of the lower yoke 21, respectively.

[0026] MEMS mirror 27 is formed by using MEMS processing technology to form metal coil portion 24a and mirror portion 27a on a single-crystal silicon chip. Coil portion 24a is formed to surround center pole 21a, and mirror portion 27a is formed to be capable of biaxial scanning by being driven in the X-axis and Y-axis directions. MEMS mirror 27 is attached to protrusions 23c, 23d, 23e, and 23f of first upper yokes 23-1 and 23-2 through mounting holes 27b, 27c, 27d, and 27e.

[0027] An external drive signal is input to the MEMS mirror 27. When a current flows through the coil portion 24a, the mirror portion 27a is driven to perform scanning by the electromagnetic action of the coil portion 24a, which is disposed in the magnetic gap between the rising portions 23a and 23b and the center pole 21a.

[0028] The second upper yoke is composed of a first member and a second member. The second upper yokes 26-1 and 26-2 are in contact with the upper surfaces of the second and fourth magnets 25-1 and 25-2, respectively, and are installed so as to cover the second and fourth magnets 25-1 and 25-2 and the first upper yokes 23-1 and 23-2. The center pole 21a is disposed in the gap between the second upper yokes 26-1 and 26-2. In addition, through holes 26a, 26b, 26c, 26d, and 26e and through holes 26f, 26g, 26h, 26i, and 26j are formed at positions corresponding to the through holes 25a, 25b, 25c, 25d, and 25e and through holes 25f, 25g, 25h, 25i, and 25j of the second and fourth magnets 25-1 and 25-2, respectively.

[0029] In the above configuration, a closed magnetic path is formed in which magnetic flux travels from the north pole of the first magnet 22-1 through the first upper yoke 23-1, the rising portion 23a, and the center pole 21a to the south pole of the third magnet 22-2, and then returns from the north pole of the third magnet 22-2 to the south pole of the first magnet 22-1 through the lower yoke 21. In addition, a closed magnetic path is formed in which magnetic flux travels from the north pole of the second magnet 25-1 through the second upper yoke 26-1 and the center pole 21a to the south pole of the fourth magnet 25-2, and then returns from the north pole of the fourth magnet 25-2 to the south pole of the second magnet 25-1 through the lower yoke 21.

[0030] At this time, the high magnetic flux from the second and fourth magnets 25-1 and 25-2 is guided into the magnetic gap and combined with the magnetic flux from the first upper yokes 23-1 and 23-2, causing the magnetic flux of the coil section 24a in the magnetic gap to be oriented horizontally and increasing the magnetic flux density, thereby enabling a uniform (oriented horizontally, constant within the gap) magnetic field with high magnetic flux density to be obtained within the magnetic gap without placing a magnet above the mirror.

[0031] Therefore, even with the above configuration, the operation is substantially the same as in the first embodiment, and the same effects can be obtained.

[0032] The configurations described in the first and second embodiments are merely schematic illustrations to enable the present invention to be understood and practiced. Therefore, the present invention is not limited to the described embodiments, and can be modified in various forms without departing from the scope of the technical idea set forth in the claims. For example, in the configurations according to the first and second embodiments described above, it goes without saying that the north and south poles of all the magnets may be reversed. [Explanation of symbols]

[0033] 11, 21...lower yoke, 11a, 11b, 11c, 11d, 21a...center pole, 12, 22-1...first magnet, 22-2...third magnet, 12a...opening, 13, 23-1, 23-2...first upper yoke, 13a, 13b, 13c, 13d, 23a, 23b...rising portion, 13e...opening, 13f, 13g, 13h, 13i...protruding portion, 14, 14a, 14b, 14c, 14d...coil portion, 15, 15-1...second magnet, 15-2...third magnet, 16, 26-1, 26-2...second upper yoke, 17, 27...MEMS mirror (chip), 18...drive device, 25-1...second magnet, 25-2...fourth magnet

Claims

1. a first magnet disposed on a lower yoke with a center pole; a first upper yoke provided on the first magnet; a second magnet disposed on the lower yoke at a greater distance from the center pole than the first magnet and having a stronger magnetomotive force than the first magnet; a second upper yoke provided on the second magnet, The first upper yoke and the second upper yoke are in contact with each other, forming a magnetic gap between the first upper yoke and the center pole, and the magnetic circuit type mirror drive device drives the mirror section by the electromagnetic action of the coil section arranged within the magnetic gap.

2. The coil portion is sandwiched between the first upper yoke and the second upper yoke arranged on the first upper yoke and arranged to surround the center pole, 2. The magnetic circuit type mirror driving device according to claim 1, wherein said mirror section is formed so as to be capable of being driven in the X-axis direction and the Y-axis direction for two-axis scanning.

3. the center pole is formed of first to fourth columnar members arranged in the center of the lower yoke so as to surround the mirror section, and coil sections are arranged around the first to fourth columnar members, respectively; the first magnet is a frame-like magnet having an opening formed at a position corresponding to the center pole, the lower yoke has first to fourth rising portions bent upward from above the first magnet to face the first to fourth columnar members, respectively, and the magnetic gaps are formed between the first to fourth rising portions and sidewall surfaces of the first to fourth columnar members, respectively; 3. The magnetic circuit type mirror drive device according to claim 1, further comprising a third magnet arranged on the lower yoke outside the first magnet, facing the second magnet across the center pole, and having a magnetomotive force equal to that of the second magnet.

4. the second and third magnets are thicker than the sum of the thickness of the first magnet and the first upper yoke; 4. The magnetic circuit type mirror drive device according to claim 3, wherein the second upper yoke is in contact with the second and third magnets and the first to fourth raised portions, and is positioned to cover the first to third magnets except for the mirror portion and the center pole.

5. a third magnet disposed on the lower yoke so as to face the first magnet across the center pole; a fourth magnet disposed on the lower yoke outside the third magnet and facing the second magnet across the center pole, 3. The magnetic circuit type mirror drive device according to claim 1, wherein the first magnet and the second magnet have magnetic poles oriented in the same direction, and the third magnet and the fourth magnet have magnetic poles oriented in the same direction but opposite to the magnetic poles of the first magnet and the second magnet.

6. the second and fourth magnets are each thicker than the sum of the first magnet and the first upper yoke or the third magnet and the first upper yoke; 6. The magnetic circuit type mirror drive device of claim 5, wherein the second upper yoke is composed of a first member that contacts the upper surface of the second magnet and is arranged covering the first and second magnets, and a second member that contacts the upper surface of the fourth magnet and is arranged covering the third and fourth magnets.

7. A magnetic circuit type mirror driving device as described in any one of claims 1 to 3, wherein the coil portion and the mirror portion are formed by forming a metal coil portion on a single crystal silicon chip using MEMS (Micro Electro Mechanical Systems) processing technology, and forming a mirror portion inside the coil portion.

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