KR20090091610A - Mems mirror and scanning actuator employing the same - Google Patents

Abstract

An MEMS(Micro Electro-mechanical System) mirror and a scanning actuator employing the same are provided to reduce deterioration of the performance by reducing the sensitivity about the manufacturing tolerance using a plurality of hinge bars. An MEMS mirror(200) includes a blade(230), a plurality of hinge bars(221,222,223,224), a first anchor(211), and a second anchor(212). A permanent magnet is attached to one surface of a blade and the rear is a reflective surface. The first and second anchors are separately formed on both sides of the blade. The plurality of hinge bars support the rotation of the blade and connect the blade and the first and second anchors. An electronic magnet includes a yoke and a coil surrounding the yoke and provides the rotation force to the permanent magnet.

Description

MEMS mirror and scanning actuator employing the same

The present invention relates to a MEMS mirror that reflects incident light and a scanning actuator that scans light by rotationally driving the MEMS mirror.

Beam scanning technology that scans a beam emitted from a light source to a predetermined area is applied in various fields such as a laser printer and a scanning display.

Recently, as the trend of the printer market progresses in the direction of increasing the printing speed, it is required to speed up the polygon mirror operation that determines the printing speed for high speed printing.

1 is a general schematic diagram of a scanning apparatus using a polygon mirror. Referring to the drawings, light emitted from the light source 1 passes through the optical system 2 and is incident on the polygon mirror 3 and reflected by the polygon mirror 3. The polygon mirror 3 is mounted on the spindle motor 4 to be driven in rotation. As the polygon mirror 3 is driven to rotate in the direction of arrow A, the light reflected from the polygon mirror 3 is scanned in the direction of arrow B. As shown in FIG.

Such a scanning device has a polygon mirror 3 mounted on a spindle motor 4 that rotates at a high speed, and thus has a limitation in increasing scanning speed due to problems such as vibration and noise of the spindle motor 3. There is also a limit to the volume reduction.

Thus, to achieve higher beam scanning speeds, new mechanisms are needed that can replace spindle motors and polygon mirrors.

Scanning apparatus using MEMS (micro electro-mechanical system) structure can be bidirectional scanning and high-speed scanning, and can be manufactured in a small size by the semiconductor process, it can replace the scanning apparatus using polygon mirror As an alternative, a MEMS scanning apparatus having various structures has been developed. Scanning structures that rotate around the axis of rotation require a design that ensures tolerances because it is dynamically important to match the center of mass and the center of rotation of the rotor. In addition, there is a need for a design that can maintain linearity with rotation.

The present invention has been made in accordance with the above-described needs, and an object of the present invention is to provide a MEMS mirror capable of implementing high-speed scanning and excellent rotation characteristics and a scanning actuator using the same.

MEMS mirror according to an embodiment of the present invention is a permanent magnet is attached to one surface, the rear surface of the one surface is formed of a reflective surface; First and second anchors spaced apart from each other on both sides of the blade; Supporting the rotation of the blade, comprising a plurality of hinge bars connecting the blade and the first and second anchors, respectively, wherein the plurality of hinge bars are formed in pairs of two facing each other in a zigzag form It is characterized in that connected to the first and second anchors, respectively.

A plurality of rigid reinforcement ribs may be formed on one surface of the blade.

The plurality of rigid reinforcement ribs may include a first rib formed in a direction perpendicular to the rotation axis of the blade and / or a plurality of second ribs and / or the permanent magnet provided in a form of a leaf vein together with the first rib. It may include a third rib provided in a form surrounding the periphery of the permanent magnet to fix the.

Scanning actuator according to the invention is provided with a permanent magnet on one surface, the back surface of the one surface is formed of a reflective surface; First and second anchors spaced apart from each other on both sides of the blade; Supporting the rotation of the blade, a plurality of hinge bars for connecting the blade and the first and second anchors, respectively; It is provided to provide a rotational force to the permanent magnet, including an electromagnet portion including a yoke and a coil surrounding the yoke, wherein the shape of the portion of the yoke facing the permanent magnet is formed along the shape of the permanent magnet It is characterized by.

The permanent magnet may have a cylindrical shape, and the shape of the portion where the yoke faces the permanent magnet may have a coaxial cylindrical surface shape with the cylinder.

The plurality of hinge bars may be connected to the first and second anchors in a pair of two zigzag facing each other.

A plurality of rigid reinforcement ribs may be formed on one surface of the blade, wherein the plurality of rigid reinforcement ribs form a leaf vein shape together with the first rib and / or the first rib formed in a direction perpendicular to the rotation axis of the blade. It may include a plurality of second ribs and / or the third rib provided in a form surrounding the periphery of the permanent magnet to fix the position of the permanent magnet.

MEMS mirror assembly method according to an embodiment of the present invention comprises the steps of preparing a jig in which a hole is formed therein, a plurality of protruding boss is formed; Connecting the MEMS mirror and the jig by inserting first and second holes formed in the MEMS mirror according to an embodiment of the present invention into the plurality of bosses; And separating the notch portion and the inner surface of the frame.

The MEMS mirror according to the embodiment of the present invention employs a plurality of hinge bars to reduce sensitivity to manufacturing tolerances, and thus has a structure capable of reducing performance degradation due to manufacturing tolerances. In addition, the increase in stress caused by the increase in the hinge bar is mitigated by forming the shape of the hinge bar in a zigzag shape.

MEMS mirror according to an embodiment of the present invention, also has an advantageous structure in terms of assembling, thereby providing a MEMS mirror assembly method of the assembly mass production is improved.

The scanning actuator according to the embodiment of the present invention has the advantage that torque characteristics and linearity are improved by employing the MEMS mirror according to the embodiment of the present invention and having an improved yoke shape.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of description.

2 is a perspective view schematically illustrating a structure of a scanning actuator 300 according to an embodiment of the present invention, and FIGS. 3A and 3B are front views of the MEMS mirror 200 employed in the scanning actuator 300 of FIG. 2, respectively. And a rear perspective view.

Referring to the drawings, the scanning actuator 300 includes a MEMS mirror 200 forming a rotor and an electromagnet portion 100 forming a stator. The MEMS mirror 200 has a structure including the permanent magnet 240 and is disposed such that the permanent magnet 240 is located in the magnetic field formed by the electromagnet part 100.

The MEMS mirror 200 includes a blade 230, a plurality of hinge bars 221, 222, 223, and 224, a first anchor 211, and a second anchor 212. A permanent magnet 240 is attached to one surface of the blade 230, and the rear surface of the blade 230 is formed of a reflective surface 230a capable of reflecting light. The first and second anchors 211 and 212 are provided to be spaced apart from both sides of the blade 230, respectively.

A plurality of hinge bars 211, 212, 213, and 214 are provided between the first and second anchors 211, 212 and the blades 230 to support the rotation of the blades 230. For example, two hinge bars 211 and 212 formed symmetrically with respect to the rotation axis R form a pair to connect one side of the blade 230 and the first anchor 211, and also to the rotation axis R. Two hinge bars 213 and 214 symmetrically formed with respect to each other form a pair to connect the other side of the blade 230 and the second anchor 212. The hinge bars 211, 213 and the hinge bars 212, 214, which are symmetric about the rotation axis, rotate the blades 230 by receiving the force in opposite directions when the permanent magnet 240 receives the rotational force in the magnetic field. The hinge bars 211, 212, 213, and 214 may have a zigzag shape, for example. This zigzag shape serves to reduce the stress generated during the rotation of the blade 230 to maximize the dispersion in a limited space.

 First and second holes 213 and 214 may be formed in the first and second anchors 211 and 212, respectively, and the first and second holes 213 and 214 facilitate assembly of the MEMS mirror 200 to another structure. It is to. In addition, first and second notches 215 and 216 may be provided at one end of the first and second anchors 211 and 212, respectively.

A plurality of rigid reinforcing ribs may be formed on one surface of the blade 230 to which the permanent magnet 240 is attached to reinforce the rigidity of the blade 230. Rigidity reinforcement ribs are provided to ensure high frequency characteristics by increasing the rigidity of the blade 230 while lowering the rotational moment of inertia. For example, the first rib 231 may be formed in a direction perpendicular to the rotation axis of the blade 230. The first rib 231 of this type serves to prevent the blade 230 from bending in the rotation direction when the blade 230 rotates. In addition, a plurality of second ribs 232 may be further formed to form a leaf vein together with the first ribs 231. The second rib 232 of this type serves to reinforce rigidity in a direction perpendicular to the rotation direction. In addition, the third rib 233 may be formed to surround the periphery of the permanent magnet 240 to fix the position of the permanent magnet 240. This structure improves the rigidity of the blade 230, so that the resonance mode of the hinge bar (221, 222, 223, 224) is about several kHz, the resonance mode of the blade 230 is raised to several hundred kHz. That is, the hinge bar (221, 222, 223, 224) mode and the blade 230 mode can be sufficiently separated, the coupling that may occur during the scanning operation can be prevented.

The electromagnet unit 100 includes a yoke 120 and a coil unit 150 surrounding the yoke 120. The yoke 120 forms a magnetic path of the magnetic field formed by the current when the current is applied to the coil unit 150. The yoke 120 may be formed of, for example, a magnetic material. Both ends of the yoke 120 are spaced apart by a predetermined distance to face each other. At both ends of the yoke 120, in particular, the first and second ends 120a and 120b facing the permanent magnet 240 are formed along the shape of the permanent magnet 240. For example, as shown, the permanent magnet 240 has a cylindrical shape and the first and second ends 120a and 120b of the yoke 120 facing the permanent magnet 240 are the permanent magnet 240. It has a coaxial cylindrical surface shape.

4A and 4B are cross-sectional views taken along line VI-VI 'of FIG. 2, and are conceptual views illustrating a driving principle of the scanning actuator 300. When a current is applied to the coil unit 150, both ends of the yoke 120 may have S / N polarities as shown in FIG. 4A or N / S as shown in FIG. 4B according to the direction of the current. That is, when a current is applied to the coil unit 150, a magnetic field is formed between the first and second ends 120a and 120b of the yoke 120 in a direction from the N pole to the S pole. The magnetic moment lying in the magnetic field is subjected to torque in the direction that causes the magnetic moment to align along the direction of the magnetic field. In the drawings, the permanent magnet 240 shows a case in which the lower side is formed as the N pole, and therefore, the blade 230 rotates in the direction of the arrow shown in FIGS. 4A and 4B.

As such, the magnetic field distribution formed between the first and second ends 120a and 120b of the yoke 120 is an element directly affecting the rotational characteristics of the blade 230 to which the permanent magnet 240 is attached. In the present invention, as described in the drawings of FIGS. 2, 3A and 3B, the shape of the first and second ends 120a and 120b in which the yoke 120 faces the permanent magnet 240 may be defined as that of the permanent magnet 240. It is intended to have the same shape as the shape, which is proposed as a design to form a magnetic field distribution while increasing the generated torque while reducing the amount of change in torque. That is, the magnetic field distribution is affected not only by the physical properties and the shape of the yoke 120 but also by the magnetic flux distribution generated in the permanent magnet 240, and the magnetic flux generated in the permanent magnet 240 is the permanent magnet 240. According to the present invention, the magnetic field distribution is formed between the first and second ends 120a and 120b of the yoke 120 by a change in magnetic flux distribution due to a change in position due to rotation of the permanent magnet 240. It adopts a design that keeps changes to a minimum. This design improves linearity and thrust, and this effect will be described later in the graphs of FIGS. 6 and 7.

On the other hand, the hinge bar (221, 222, 223, 224) is fixed to the anchor (211,212) during the rotational drive to support the rotation of the blade 230, the present invention has two hinge bars (221, 222 symmetrically spaced apart from the rotation axis by a predetermined distance) A structure in which one side of the blade 230 and the first anchor 211 are connected, and two hinge bars 223 and 224 symmetrically spaced apart from each other by a rotation axis connect the other side of the blade 230 and the second anchor 212. Has Adopting such a configuration is intended to reduce the deterioration of characteristics due to the center of mass and the rotation center does not coincide with the blade 230 in the rotation drive.

5A and 5B illustrate the case where one hinge is placed on the rotating shaft and two hinges spaced apart from the rotating shaft, respectively, to explain the effect on driving characteristics when the center of mass and the rotating center do not coincide. This is a conceptual diagram.

Referring to FIG. 5A, there is a deviation by e in the center of rotation G of the blade b and the center of mass M of the permanent magnet pm placed on the blade b. In this case, its own torque T = mg * e (T is torque, m is mass, g is gravity acceleration) may occur, thereby increasing the fatigue of the structure. Similarly, FIG. 5B is a case where the center of rotation G of the blade 230 and the center of mass M of the permanent magnet 240 placed on the blade 230 have a deviation of e. In this case, however, two hinge bars 221 and 222 spaced apart at a distance r are formed at positions symmetrical to the axis of rotation, and therefore, when the deviation e is within the distance r, T = 0, i.e., torque is generated. I never do that.

The deviation between the center of mass and the rotational center is due to the manufacturing tolerance of the permanent magnet 240 and the tolerance occurring when attaching it to the blade 230, and is known to be 50um or more on one side. When the plurality of hinge bars (221, 222, 223, 224) is adopted as in the present invention, it can be seen that the sensitivity of the characteristic when the center of rotation and the center of mass do not coincide can be reduced.

6 and 7 are graphs showing the torque characteristics of the scanning actuator in the case of the embodiment of the present invention and the comparative example, Figure 8 is a view showing the yoke shape of the embodiment and the comparative example, the dotted line is shown in the comparative example Corresponding.

Referring to FIG. 6, the horizontal axis of the graph represents a current ([A]) applied to the coil unit 150, and the vertical axis represents a generated generation torque (Nm / A). The graph shown is a graph in which the measured points (■, ◆) are fitted to a straight line. In the embodiment, the fitting points of the measured points (■) and the straight line are better than those of the comparative example. It can be seen that the size itself is large.

FIG. 7 is a graph showing generation torque per unit current [Nm / A] versus time. In the case of the embodiment it can be seen that the torque characteristics are superior to the case of the comparative example.

 9A to 9D are views for explaining a MEMS mirror assembly method according to an embodiment of the present invention. MEMS mirror assembly method of the present invention is to propose a method for safely handling a very small MEMS mirror and attach to the desired position without damage.

Referring to FIG. 9A, the MEMS mirror 200 ′ has a structure further including a frame 250 as compared to the MEMS mirror 200 of FIG. 2A, and includes a first formed at one end of the first and second anchors 211 and 212. And the second notches 215 and 216 are connected to the inner surface of the frame 200. This structure is adapted for ease of handling of the MEMS mirror 200 'during assembly or transportation.

Next, as shown in FIG. 9B, a hole 262 is formed thereinto, and a jig 260 having first and second bosses 263 and 264 is prepared. At this time, the hole 262 formed in the jig 260 is a rotation space of the blade 230 and is provided to allow the reflected light to pass.

Next, as shown in FIG. 9C, the first boss 263 is inserted into the first hole 213, and the second boss 264 is inserted into the second hole 214, thereby forming the MEMS mirror 200 in the jig 260. Install it.

Next, as illustrated in FIG. 9D, the frame 250 is separated by removing the first and second notches 215 and 216 from the inner surface of the frame 250.

By this process, the MEMS mirror can be assembled at a desired position.

The shape of the jig 260 presented in the description is exemplary and may have a form in which a structure serving as a driving source for driving the MEMS mirror 200, for example, the electromagnet portion 100 of FIG. 2 may be mounted. .

The present invention has been described with reference to the embodiments shown in the drawings for ease of understanding, but this is merely exemplary, those skilled in the art that various modifications and equivalent other embodiments are possible from this. I will understand. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

1 is a general schematic diagram of a scanning apparatus using a polygon mirror.

2 is a perspective view schematically showing the structure of a scanning actuator according to an embodiment of the present invention.

3A and 3B are front and rear perspective views, respectively, of a MEMS mirror employed in the scanning actuator of FIG. 2.

4A and 4B are cross-sectional views taken along line VI-VI 'of FIG. 2, and are conceptual views illustrating the driving principle of the scanning actuator.

5A and 5B illustrate the case where one hinge is placed on the rotation axis and two hinges symmetrically spaced from the rotation axis, respectively, to explain the effect on driving characteristics when the center of mass and the rotation center do not coincide. Conceptual diagram.

6 and 7 are graphs showing torque characteristics of scanning actuators in the case of the examples and comparative examples of the present invention.

8 is a view showing a comparison of the yoke shape of the embodiment of the present invention and the comparative example.

9A to 9D are views for explaining a MEMS mirror assembly method according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100 Electromagnet 120 York

150 ... coil part 200,200 '.. Memes mirror

211,212 ... 1st, 2nd anchor 213,214 ... 1st, 2nd hole

215,216 ... 1st, 2nd notch 221,222,223,224 ... 1st ~ 4th hinge bars

230 ... blades 231,232,233 ... 1st ~ 3rd rib

240 Permanent Magnet 250 Frame

260 ... Jig 262 ... Hole

263,264 ... First and second boss

Claims (16)

A blade having a permanent magnet attached to one surface thereof, and a rear surface of the one surface formed of a reflective surface; First and second anchors spaced apart from each other on both sides of the blade; It includes a plurality of hinge bars for supporting the rotation of the blade, connecting the blade and the first and second anchors, respectively, The plurality of hinge bars is a pair of two facing each other in a zigzag form a pair of MEMS mirrors, characterized in that connected to the first and second anchors. The method of claim 1, MEMS mirror, characterized in that a plurality of rigid reinforcing ribs are formed on the one surface. The method of claim 2, The plurality of rigid reinforcing ribs MEMS mirror, characterized in that it comprises a first rib formed in a direction perpendicular to the axis of rotation of the blade. The method of claim 3, The plurality of rigid reinforcement ribs further comprises a plurality of second ribs provided in the form of a leaf vein shape with the first ribs MEMS mirror. The method of claim 4, wherein The plurality of rigid reinforcing ribs MEMS mirror, characterized in that further comprises a third rib provided in a form surrounding the periphery of the permanent magnet to fix the position of the permanent magnet. The method according to any one of claims 1 to 5, And a notch provided at one end of the frame and the first and second anchors surrounding the MEMS mirror, MEMS mirror, characterized in that the notch is connected to the inner surface of the frame. The method of claim 6, MEMS mirrors, characterized in that the first and second anchors are formed with first and second holes, respectively. A blade provided with a permanent magnet on one surface and a rear surface of the one surface as a reflective surface; First and second anchors spaced apart from each other on both sides of the blade; A plurality of hinge bars for supporting rotation of the blades and connecting the blades to the first and second anchors, respectively; It is provided to provide a rotational force to the permanent magnet, including an electromagnet portion including a yoke and a coil surrounding the yoke; Scanning actuator, characterized in that the shape of the portion of the yoke facing the permanent magnet is formed along the shape of the permanent magnet. The method of claim 8, The permanent magnet is a cylindrical shape, The shape of the part in which the yoke faces the permanent magnet is in the shape of a coaxial cylindrical surface with the cylinder. The method of claim 8, Scanning actuators, characterized in that the plurality of hinge bars are connected to the first and the second anchor in a pair of two zigzag facing each other. The method according to any one of claims 8 to 10, Scanning actuator, characterized in that a plurality of rigid reinforcing ribs are formed on the one surface. The method of claim 11, And the plurality of rigid reinforcement ribs include a first rib formed in a direction perpendicular to the rotation axis of the blade. The method of claim 12, The plurality of rigid reinforcement ribs further comprises a plurality of second ribs provided in the form of a leaf vein shape with the first ribs. The method of claim 13, The plurality of rigid reinforcing ribs further comprises a third rib provided in a form surrounding the periphery of the permanent magnet to fix the position of the permanent magnet. Preparing a jig having a hole formed therein and a plurality of protruding bosses formed therein; Connecting the MEMS mirror to the jig by inserting first and second holes formed in the MEMS mirror of claim 7 into the plurality of bosses, respectively; Separating the notch and the inner surface of the frame; MEMS mirror assembly method comprising a. The method of claim 15, The jig is characterized in that the electromagnet portion for providing a rotational force to the MEMS mirror can be mounted.

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