KR102614491B1 - Tripod MEMS scanner using electromagnetic Force Drive - Google Patents

Abstract

A support plate including an opening, a mirror plate provided in the opening and reflecting input light, at least three springs provided around an edge of the mirror plate, and each end of which is connected to the support plate and the mirror plate, and the at least three A MEMS scanner can be provided that includes at least three conductive bands extending from each of the springs, passing through the mirror plate, to a spring provided adjacent to one direction of each spring.

Description

Tripod MEMS scanner using electromagnetic force drive}

The present invention relates to a Tripod MEMS (Micro Electro Mechanical Systems) scanner. More specifically, it relates to a Tripod MEMS scanner in which a scanning mirror that reflects a laser performs three-dimensional rotational movement through electromagnetic force driving.

With the recent development of optical device technology, various technologies that use light as a medium for input and output of various information and information transmission have been proposed. These technologies have been combined with MEMS (Micro Electro Mechanical Systems) technology to make them more compact and lightweight. The product is being developed.

MEMS scanners can project images when using red, blue, and green lasers, and when using infrared lasers, distance information can be obtained by sensing the laser reflected by a photo diode.

These MEMS scanners can be applied to confocal microscopy, barcode reading, fingerprint sensors, etc., and have recently been used in optical cross-connets (OXC) and optical interference. It is widely applied to optical coherence spectroscopy (OCT), retinal scanning display (RSD), laser printers, head-up display light detection and ranging (LIDAR) sensors, etc. .

MEMS scanners require scanning mirrors with various scanning speeds, scanning ranges, angular displacements, and tilting angles depending on the application case. A scanning mirror is a device that scans light coming from a light source into a one-dimensional or two-dimensional area to form an image or read data.

MEMS scanners can be classified into 1-axis, 2-axis, and rotation types depending on the type of movement of the scanning mirror, and can also use electromagnetic force, electrostatic force, piezo-electric, and thermal driving methods.

However, although various driving methods can be applied to existing 1-axis and 2-axis MEMS scanners, rotational MEMS scanners are limited to driving by electrostatic force.

In the case of a rotating MEMS scanner, it can be advantageous to form an image or read data through an omnidirectional lens. However, electrostatic force-type rotational MEMS scanners have problems in that it is difficult to implement relatively strong force compared to electromagnetic force, and there is a risk of short circuit due to contact due to its compact structure.

One embodiment of the present invention aims to provide a rotary MEMS scanner that three-dimensionally rotates a scanning mirror so that reflected incident light forms a circular pattern or spiral pattern.

In addition, an embodiment of the present invention aims to provide a structure in which a rotating MEMS scanner is driven by electromagnetic force using a circular magnetic field and a coil structure.

Additionally, an embodiment of the present invention aims to increase the driving angle of the scanning mirror through the structure of a spring connected to the scanning mirror.

In addition, the purpose of the present invention is to provide a rotational MEMS scanner that uses a current-carrying conductor in addition to a circular magnet as a method of forming a circular magnetic field.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

A MEMS scanner according to an embodiment of the present invention for solving the above problem includes a support plate including an opening, a mirror plate provided within the opening and reflecting input light, and a mirror plate provided around an edge of the mirror plate, each at both ends. At least three springs connected to the support plate and the mirror plate, and at least three conductive bands provided from each spring of the at least three springs through the steel mirror plate to a spring provided adjacent to one direction of each spring. It can be characterized as:

Additionally, the at least three springs may be formed along a circular orbit or a spiral orbit surrounding the edge of the mirror plate.

Additionally, the MEMS scanner is provided below the at least three springs and may include circular magnets or circular conductors that form a radial magnetic field in the at least three springs.

Additionally, the mirror plate is circular, and the at least three conductive bands may pass along an edge of the mirror plate.

Additionally, when a drive signal is sequentially applied to the at least three conductive strips, the at least three springs may sequentially move up and down through electromagnetic force generated in the conductive strips.

Additionally, the input light reflected by the mirror plate may form a circular pattern or a spiral pattern.

In addition, the MEMS scanner is provided spaced apart from the mirror plate and further includes a refractive lens that refracts the input light reflected by the mirror plate, and the refractive lens is an incident surface on which the reflected input light is incident or the The refracting surface through which the reflected granular light is refracted may be an omnidirectional lens having a dome shape.

In addition, the at least three springs are provided at a body portion surrounding the edge of the mirror plate, a clockwise end portion of the body portion, a first connection portion connecting the body and the mirror plate, and a counterclockwise end portion of the body portion. It is provided in and may include a second connection portion connecting the body portion and the support plate.

Additionally, the at least three springs may be provided along the edge of the 180° area of the body portion of the mirror plate.

Additionally, the at least three springs may be provided along the edge of the 360° area of the body portion of the mirror plate.

The effects of the rotary MEMS scanner of the present invention will be described as follows.

In the present invention, the scanning mirror is rotated in three dimensions so that the reflected incident light forms a circular pattern or a spiral pattern, and the method of scanning in a circular pattern or a spiral pattern is advantageous for omnidirectional scanning using a lens or the like.

The present invention uses an electromagnetic force method using a circular magnetic field and coil structure to drive the scanning mirror, and the strong electromagnetic force can expand the area that a rotary MEMS scanner can scan without a separate vacuum package.

The present invention can increase the angle at which the scanning mirror drives through a spring structure connected to the scanning mirror and expand the area that a rotary MEMS scanner can scan.

The present invention can provide a rotational MEMS scanner with strong heat resistance by using a circular conductor instead of a circular magnet that forms a circular magnetic field.

Further scope of applicability of the present invention will become apparent from the detailed description that follows. However, since various changes and modifications within the spirit and scope of the present invention may be clearly understood by those skilled in the art, the detailed description and specific embodiments such as preferred embodiments of the present invention should be understood as being given only as examples.

Figure 1 is a schematic diagram of a MEMS scanner using existing electromagnetic forces.
Figure 2 is a diagram explaining the driving principle of a MEMS scanner using existing electromagnetic force.
Figure 3 is a diagram showing an embodiment of forming a 2D image using an existing MEMS scanner.
Figure 4 is a diagram showing a scanning micro mirror of a MEMS scanner according to the present invention.
Figure 5 is a diagram showing a circular magnet of a MEMS scanner according to the present invention.
FIG. 6 is a view of the radial magnetic field formed by the circular magnet of the MEMS scanner according to the present invention viewed from cross-section A of FIG. 5 and a graph showing the strength of the magnetic field.
Figure 7 is a diagram showing the direction of electromagnetic force applied to a circular conductor in a radial magnetic field.
Figure 8 is a diagram showing the direction in which electromagnetic force is applied to the conductive wire provided on the scanning mirror of the MEMS scanner according to the present invention.
Figure 9 is a diagram showing the scanning mirror of the MEMS scanner according to the present invention forming a driving angle by receiving electromagnetic force.
Figure 10 is a graph showing an example of a driving signal applied to a conductive wire provided on a scanning mirror of a MEMS scanner according to the present invention.
Figure 11 is a diagram showing how a laser reflected by the scanning mirror of a MEMS scanner according to the present invention forms a circular pattern or a spiral pattern.
Figure 12 is a table showing the resonance frequency of the driving signal applied to the conductive wire provided on the scanning mirror of the MEMS scanner according to the present invention and the mode for each resonance frequency.
FIG. 13 is a diagram illustrating the feature in which the scanning mirror of the MEMS scanner according to the present invention changes movement depending on the mode of FIG. 12.
Figure 14 is a conceptual diagram showing a MEMS scanner according to the present invention reflecting input light using an omni-directional lens.
Figure 15 is a diagram showing another embodiment of a scanning mirror of a MEMS scanner according to the present invention.

Hereinafter, embodiments disclosed in the present specification will be described in detail with reference to the attached drawings. However, identical or similar components will be assigned the same reference numbers regardless of reference numerals, and duplicate descriptions thereof will be omitted. The suffixes “module” and “part” for components used in the following description are given or used interchangeably only for the ease of preparing the specification, and do not have distinct meanings or roles in themselves. Additionally, in describing the embodiments disclosed in this specification, if it is determined that detailed descriptions of related known technologies may obscure the gist of the embodiments disclosed in this specification, the detailed descriptions will be omitted. In addition, the attached drawings are only for easy understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the attached drawings, and all changes included in the spirit and technical scope of the present invention are not limited. , should be understood to include equivalents or substitutes.

Terms containing ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

MEMS (Micro Electro Mechanical Systems) scanners can be divided into 1-axis MEMS scanners, 2-axis MEMS scanners, and rotational MEMS scanners depending on the type of movement. In addition, various driving methods can exist, such as electromagnetic force, electrostatic force, piezo-electric, and thermal.

A 1-axis MEMS scanner can form an image by scanning a laser in a 1-dimensional area or read data along a 1-dimensional area. A two-axis MEMS scanner can scan a laser into a two-dimensional area to form an image or read data along a two-dimensional area.

However, existing 1-axis or 2-axis MEMS scanners have the disadvantage of not being easy to scan in all directions using a refractive lens because they scan the laser by rotating around one axis or intersecting axes.

Rotational MEMS can be driven so that the central axis of the scanning mirror rotates along the edges of a pair of cones whose vertices are symmetrically connected.

In other words, a laser scanned from a rotational MEMS forms a circular pattern or spiral pattern in a two-dimensional area. Rotational MEMS, in which a reflected laser forms a circular or spiral pattern, facilitates omnidirectional scanning using a refractive lens. This will be discussed in Figure 14.

The existing method of driving a MEMS scanner using electrostatic force prefers to use a comb drive. The comb drive method is equipped with a comb drive that moves up and down by electrostatic force at the edge of the scanning mirror, and the comb drive moves up and down to drive the scanning mirror. The comb drive type MEMS scanner has the advantage of being simple and can be made small. , the force that can be realized through electrostatic force is not strong, there is a lot of current loss, and the linearity is poor. Additionally, because the magnitude of the electrostatic force is weak, vacuum packaging is essential to obtain the driving angle of the scanning mirror.

Piezo-electric MEMS scanners prefer to use PZT (solid solution general term for zirconate PbZrO₃ and titanate PbTiO₃) film. The PZT film with the scanning mirror in between contracts and relaxes, allowing the scanning mirror to form a driving angle. Piezo-electric MEMS scanners have the disadvantage that it is difficult to increase the driving angle.

The existing MEMS scanner driving method using electromagnetic force prefers the method using a moving coil. The moving coil method provides a circular conductor between the magnetic fields and rotates the scanning mirror using the electromagnetic force acting on the circular conductor. The moving coil method is simple, the driving angle is large, and the electrostatic force that can be implemented is strong. Therefore, existing MEMS scanners using electromagnetic force are mainly used. Below, we will look at a two-axis MEMS scanner using existing electromagnetic force through Figures 1 and 2.

Figure 1 is a schematic diagram of a MEMS scanner using existing electromagnetic forces.

Figure 2 is a diagram explaining the driving principle of a MEMS scanner using existing electromagnetic force.

As shown in FIG. 1, a basic two-axis MEMS scanner reflects incident light (1) on a scanning mirror (2) that rotates vertically/horizontally to form an image (7) proportional to the driving angle or to generate data. It can be read.

A typical two-axis MEMS scanner may include a scanning mirror (2), a single-axis spring (3), a gimble (4), a two-axis spring (5), and a support end (6).

Here, the scanning mirror 2 may be supported at both ends by a single-axis spring 3 that serves as a rotation axis and provides restoring force when driven. Additionally, the uniaxial spring (3) may be connected to the gimble (4).

The gimble (4) is supported by a two-axis spring (5), which also serves as a rotation axis and provides restoring torque when driven, and may be connected to the support end (6).

A conductor (coil) through which a current flows is provided on the gimble 4, and as shown in Figure 2, the conductor receives electromagnetic force in a magnetic field and is driven to rotate around one or two axes.

Figure 2(a) is a diagram showing the driving principle of a 1-axis MEMS scanner. A circular conductor in a unidirectional magnetic field can rotate by changing the direction of current application.

Figure 2(b) is a diagram showing the driving principle of a two-axis MEMS scanner. A circular conductor in a radial magnetic field can rotate in two axes by varying the current application direction and axis.

Figure 3 is a diagram showing an embodiment of forming a 2D image using an existing MEMS scanner.

Figure 3 shows an embodiment of forming an image with incident light emitted through an RGB laser diode, but the same method of reading image data can also be applied.

Figure 3(a) shows an example of forming a 2D image using a 2-axis MEMS scanner. The laser emitted from the RGB laser diode is reflected by a fixed mirror and scanned by a 2-axis MEMS scanner, and the 2-axis MEMS scanner can drive a scanning mirror to create an image on the screen or read data.

Figure 3(b) shows an embodiment of forming a 2D image using two 1-axis MEMS scanners. The fixed mirror in Figure 3(a) is a 1-axis MEMS scanner, and the laser reflected by the 1-axis MEMS scanner is scanned to a 1-axis MEMS scanner with a different axis direction to create a 2D image or read data.

However, as seen in FIG. 3, 2D image imaging using a 2-axis MEMS scanner or two 1-axis MEMS scanners has the disadvantage that omnidirectional scanning is difficult even when using a refractive lens because the laser moves linearly in two defined directions.

Therefore, below, we will look at the structure of a rotary MEMS scanner using electromagnetic force, which is a feature of the present invention.

Figure 4 is a diagram showing the scanning micromirror 400 of the MEMS scanner according to the present invention.

The MEMS scanner according to the present invention includes a support plate 401 including an opening, a mirror plate 402 that is provided within the opening and reflects input light, and is provided surrounding the edge of the mirror plate 402, and both ends each have a support plate 401. ) and at least three springs 403 connected to the mirror plate 402, and from each spring of the at least three springs 403 through the mirror plate 402 to a spring provided adjacent to one direction of each spring. It may include at least three conductive bands 404.

That is, the MEMS scanner according to the present invention may include a scanning micro mirror 400 including a support plate 401, a mirror plate 402, at least three springs 403, and a conductive band 404. In some cases, the scanning micromirror 400 can be driven using two springs 403, but in order to implement a rotary MEMS scanner, it is desirable to have at least three springs. Figure 4 illustrates a scanning micromirror including three springs 4031, 4032, and 4033.

The conductive strip 404 may be connected to each spring 403 and the spring 403 and mirror plate 402 adjacent to each spring 403 in one direction. That is, each spring 403 may be provided with two conductive bands 404 connected to adjacent springs 403 in both directions.

Looking at the driving signal applied to the conductive strip 404, the driving signal may enter one spring 403, pass through the mirror plate 402, and come out to the adjacent spring 403 in one direction. That is, each spring 403 may be provided with two conductive bands 404, one for sending a drive signal to the adjacent spring and the other for receiving a drive signal from the adjacent spring 403.

At least three springs 403 may be formed along a circular or spiral orbit surrounding the edge of the mirror plate 402. Accordingly, the portion of the conductive band 404 provided on the spring 403 may also be formed along a circular orbit or a spiral orbit.

The conductive band 404 formed along a circular orbit or a spiral orbit can form an electromagnetic force in an upward and downward direction within a radial magnetic field. The electromagnetic force in the vertical direction formed on the conductive band 404 may act as an external force that drives the three springs 403 in the vertical direction.

In the MEMS scanner of the present invention, the spring 403 is provided on the same plane including the support plate 401 and the mirror plate 402, and the spring 403 moves up and down while the support plate 401 is fixed to the mirror plate ( 402), the driving angle can be formed.

The MEMS scanner of the present invention is provided with at least three springs 403 surrounding the edge of the mirror plate 402, and each spring 403 moves up and down independently to cause the mirror plate 402 to rotate in three dimensions. You can.

Below, we will look at the principle of three-dimensional rotation of the mirror plate 402 in a radial magnetic field.

Figure 5 is a diagram showing a circular magnet 405 of a MEMS scanner according to the present invention.

FIG. 6 is a diagram showing the radial magnetic field formed by the circular magnet 405 of the MEMS scanner according to the present invention viewed from the cross section A of FIG. 5 and a graph showing the magnetic field strength.

As shown in FIG. 5, the circular magnet 405 may include a ring-shaped external magnet 4051 and a circular internal magnet 4052 spaced apart from each other inside the external magnet 4051.

A magnetic field as shown in FIG. 6(a) may be formed between the circular internal magnet 4052 and the external magnet 4051 spaced apart by a predetermined distance. That is, the magnetic field in the space between the circular internal magnet 4052 and the external magnet 4051 and in front and behind the space may be formed in the radial direction, and as shown in FIG. 6(b), the circular internal magnet 4052 and the external magnet A strong magnetic field can be formed between (4051).

The scanning micromirror (400, see FIG. 4) according to the present invention is provided on a circular magnet 405, and can cause a radial magnetic field to pass through the conductive band 404 provided on the spring (403, see FIG. 4). there is. That is, the MEMS scanner according to the present invention is provided below at least three springs 403 and may include a circular magnet 405 that forms a radial magnetic field passing through the at least three springs 403.

Specifically, the spring 403 is preferably provided in the space between the circular internal magnet 4052 and the external magnet 4051. This is to allow a radial magnetic field to pass through at least three springs 403 including conductive bands 404 (see FIG. 4).

Since at least three springs 403 are provided in a radial magnetic field along a circular orbit or a spiral orbit, the conductive bands 404 provided on the at least three springs 403 can receive electromagnetic force in the front-back direction.

At this time, the mirror plate 402 (FIG. 2) is circular, and the conductive band 404 may pass along the edge of the mirror plate 402. That is, the portion of the conductive band 404 provided on the mirror plate 402 is provided along a circular orbit and can generate electromagnetic force in the vertical direction in a radial magnetic field.

Below, the direction of the radial magnetic field, the direction of the current flowing in the conductive band 404, and the direction of the electromagnetic force generated will be examined in detail with reference to FIG. 7.

Figure 7 is a diagram showing the direction of the electromagnetic force (F) acting on the circular conductor (I) on the radial magnetic field (B).

As shown in Figure 7(a), when the current (I) flows counterclockwise on the radial magnetic field (B), an electromagnetic force (F) can be formed in the upward direction, and as shown in Figure 7(b), the current (I) flows in a clockwise direction as shown in Figure 7(b). When I) flows, electromagnetic force (F) can be formed in the downward direction.

That is, the conductive band 404 (see FIG. 4) provided along a circular or spiral orbit within the radial magnetic field B can generate electromagnetic force in the vertical direction by the direction of the current flowing in the conductive band 404.

At this time, even if the conductive band 404 is provided along a spiral orbit, it can be divided into a component following a circular orbit flowing through the conductive band 404 and a component in the radial direction. Due to the component following the circular orbit, the electromagnetic force (F ) may occur.

Below, the direction of electromagnetic force acting on each spring 403 and mirror plate 402 when current is applied to the conductive strip 404 will be examined.

FIG. 8 is a diagram illustrating the direction in which electromagnetic force is applied to the conductive pattern 404 (see FIG. 4) provided on the scanning mirror 400 of the MEMS scanner according to the present invention.

Figure 9 is a diagram showing the scanning mirror 400 of the MEMS scanner according to the present invention forming a driving angle by receiving electromagnetic force.

Referring to FIG. 4, at least three springs 403 of the MEMS scanner according to the present invention are provided at the body portion 4031 surrounding the edge of the mirror plate 402 and at the clockwise end of the body portion 4031, , a first connection portion 4032 connecting the body portion and the mirror plate 402, and a second connection portion provided at the counterclockwise end of the body portion 4031 and connecting the body portion 4031 and the support plate 401 ( 4033) may be included.

At this time, the first connection portion 4032 may be provided at a counterclockwise end of the body portion 4031, and the second connection portion 4033 may be provided at a clockwise end of the body portion 4031. However, the first connection portion 4032 may be provided at a clockwise end of the body portion 4031, and the second connection portion 4033 may be provided at a counterclockwise end of the body portion 4031.

The first connection part 4032 and the second connection part 4033 are each provided at the end of the body part 4031 of the spring 403 in the same direction (clockwise or counterclockwise), so that one conductive band 404 is formed. When a drive signal is applied clockwise from one spring 403, a drive signal is applied counterclockwise from the adjacent spring 403. Accordingly, the direction of electromagnetic force acting on the spring 403 to which a clockwise driving signal is applied may be opposite to that of the spring 403 to which a counterclockwise driving signal is applied.

For convenience of explanation, with reference to FIG. 8, the spring corresponding to position ① is referred to as the first spring, the spring corresponding to position ② is referred to as the second spring, and the spring corresponding to position ③ is referred to as the third spring.

FIG. 8 illustrates a case where a drive signal is applied clockwise to the conductive strip 404 (see FIG. 4) on the first spring. The first spring receives an upward external force when a drive signal flows clockwise to the conductive strip 404. On the other hand, the second spring and the third spring receive a downward external force as a drive signal flows counterclockwise to the conductive band 404. Accordingly, the left portion of the mirror plate 402 rises and the right portion descends to form an inclination as shown in FIG. 9 .

At this time, if the mirror plate 402 is circular, electromagnetic force may also be applied to the conductive strip provided along the edge of the mirror plate 402, and the electromagnetic force applied to the spring 403 may be offset or reinforced depending on the direction in which the driving signal flows. can do.

Figure 8 shows an embodiment in which a drive signal (current) is applied only to the conductive strips on the first spring. When the drive signal is sequentially applied to the conductive strips on each spring, the mirror plate 402 can be rotated in three dimensions. You can.

Figure 10 is a graph showing an example of a driving signal applied to a conductive wire provided on a scanning mirror of a MEMS scanner according to the present invention.

Specifically, Figure 10 shows a drive signal applied along the first spring and the second spring, a drive signal applied along the second spring and the third spring, and a drive signal applied along the third spring and the first spring, respectively. I'm doing it. (For the first spring, second spring, and third spring, see the description of FIG. 8)

FIG. 10 is an example showing a case where there are three springs 403 (see FIG. 4). Based on the cycle of one rotation of the mirror plate 402, the drive signal is sequentially applied to each conductive band with a 1/3 phase difference. may be approved.

When there are n springs, a driving signal can be sequentially applied to each conductive band with a phase difference of 1/n.

That is, when a drive signal is sequentially applied to at least three conductive bands connected between the springs, the at least three springs sequentially move up and down through the electric force generated in the conductive bands, thereby rotating the mirror plate in three dimensions.

The driving signal may be a square or sine wave alternating current.

The part of the conductive band where (+) current flows clockwise can receive electromagnetic force in the backward direction, and the part where (+) current flows counterclockwise can receive electromagnetic force in the forward direction.

Conversely, the part of the conductive band where (-) current flows clockwise can receive electromagnetic force in the forward direction, and the part where (-) current flows counterclockwise can receive electromagnetic force in the backward direction.

The driving signal shown in FIG. 10 is not limited to one embodiment of three-dimensional rotational movement of the mirror plate.

Figure 11 is a diagram showing how the laser 3 reflected by the scanning mirror 400 of the MEMS scanner according to the present invention forms a circular pattern or a spiral pattern.

Looking at the three-dimensional rotational movement of the mirror plate 402 in detail, the mirror plate 402 can rotate along the edges of a pair of cones whose central axis is symmetrically connected to the vertices. That is, the mirror plate 402 can rotate in three dimensions so that the input light 3 reflected by the mirror plate 402 can form a circular pattern or a spiral pattern.

The size of the circular pattern formed by the input light 3 can be varied by adjusting the size of the driving signal. Referring to FIGS. 10 and 11(a), ^1st Cycle shows an embodiment of sending a driving signal with a large voltage, and ^2nd Cycle shows an embodiment of sending a driving signal with a small voltage.

When a driving signal is sent with a large voltage, the driving angle of the mirror plate increases and a circular pattern with a wide radius can be formed. On the other hand, when a driving signal is sent with a small voltage, the driving angle of the mirror plate becomes small and a circular pattern with a narrow radius can be formed.

Additionally, when the voltage magnitude of the driving signal is continuously varied, a spiral pattern can be formed as shown in FIG. 11(b).

Additionally, the mirror plate 402 (see FIG. 4) may vary in movement depending on the resonance frequency of the driving signal. Below, we will look at the movement of the mirror plate at each resonance frequency with reference to FIGS. 12 and 13.

Figure 12 is a table showing the resonance frequency of the driving signal applied to the conductive band provided on the scanning mirror of the MEMS scanner according to the present invention and the mode for each resonance frequency.

FIG. 13 is a diagram illustrating the feature in which the scanning mirror of the MEMS scanner according to the present invention changes movement depending on the mode of FIG. 12.

FIG. 13(a) shows the movement corresponding to mode 1 in FIG. 12, and the mirror plate 402 is entirely balanced and can move in the up and down directions. This is undesirable in that it does not form a driving angle.

FIG. 13(b) is a movement corresponding to mode 2 in FIG. 12, in which both ends of the mirror plate 402 intersect around the first axis and can move in the front-back direction. This can be used for one-dimensional scanning, but is not desirable in that it is no different from a one-axis MEMS scanner.

FIG. 13(c) shows the mirror plate 402 rotating around a second axis different from the first axis of FIG. 13(b), which corresponds to the three modes in FIG. 12. The mirror plate 402 can be rotated in three dimensions through both axes rotating simultaneously, and therefore, it is desirable that the MEMS scanner of the present invention uses three-mode resonance frequencies.

FIG. 13(d) shows the movement corresponding to mode 4 in FIG. 12, where at least three springs are distorted. In addition, although not shown in FIG. 13, the mirror plate may move distortedly in 5 modes or more, making it undesirable to use it in the MEMS scanner of the present invention.

That is, the MEMS scanner of the present invention preferably applies a drive signal at a resonance frequency corresponding to mode 3 so that the mirror plate 403 rotates in three dimensions.

However, the resonance frequency for each mode shown in FIG. 12 may vary depending on the size and thickness of the mirror plate and the material and number of springs.

The MEMS scanner of the present invention is easy to implement omnidirectional scanning through a lens in that incident light is reflected to form a circular pattern or spiral pattern. Hereinafter, we will look at an embodiment of implementing omnidirectional scanning through FIG. 14.

FIG. 14 is a conceptual diagram showing a MEMS scanner according to the present invention reflecting input light 3 using an omnidirectional lens 300.

The input light (3) scanned from the laser diode (2) is reflected by the scanning mirror (400) of the MEMS scanner and refracted by the omnidirectional lens (300) to form an image on the inner side of the sphere or read data from the inner side of the sphere. You can.

That is, the MEMS scanner according to the present invention is provided spaced apart on a mirror plate, and has an incident surface on which the input light 3 reflected by the mirror plate 402 is incident or a refraction surface on which the reflected input light 3 is refracted. It may be an omnidirectional lens 300 having a dome shape.

The refractive lens 300 of FIG. 14 is an example, and various lenses may be used to form an image or expand an area from which data can be read.

Below, we will look at the characteristics of varying the length of the spring as a method of increasing the driving angle of the mirror plate through FIG. 15.

Figure 15 is a diagram showing another embodiment of the scanning micromirror 400 of a MEMS scanner according to the present invention.

Figure 4 shows an embodiment in which at least three springs 403 make 0.5 turns in the spiral direction. Specifically, at least three springs 403 are rotated 0.5 times in the spiral direction so that the first connection part 4032 and the second connection part 4033 are provided in a straight line.

That is, at least three springs 403 may be provided along the edge of the 180° area of the body portion 4031 of the mirror plate 402.

If the spring 403 is long, the driving angle of the mirror plate 403 can be increased despite the same voltage level. Referring to FIG. 15, at least three springs 403 may be rotated in a spiral direction so that the first connection portion 4032 and the second connection portion 4033 are provided in a straight line.

That is, at least three springs 403 may be provided along the edge of the 360° area of the body portion 4031 of the mirror plate 402.

However, if at least three springs 403 are long, the mirror plate 403 may become relatively small or the size of the MEMS scanner may become large. Alternatively, the force supporting the mirror plate 403 may become weak, causing the mirror plate 403 to sag.

Therefore, it is important to set the length of at least three springs 402 so that the driving angle can be increased within a range where the mirror plate 403 does not sag.

In the above, an example of forming a radial magnetic field using a circular magnet was described.

However, circular magnets have the disadvantage of being irreversibly weak to heat. At approximately 120 degrees Celsius, circular magnets lose their magnetism and the MEMS scanner may lose its functionality. Therefore, there is a need to consider a MEMS scanner that has the above structure and does not lose scanning function under high temperature conditions.

The MEMS scanner may use circular conductors instead of circular magnets (405, see FIG. 5). The circular conductor is provided at the bottom of at least three springs and can form a radial magnetic field passing through at least three springs.

However, MEMS scanners using circular conductors may be disadvantageous in terms of power consumption. Therefore, it is preferable that the formation of a radial magnetic field by a circular conductor is used limited to high temperature conditions.

The above detailed description should not be construed as restrictive in any respect and should be considered illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

400: scanning micro mirror 401: support plate
402: Mirror plate 403: Spring
404: Challenge pattern 405: Circular magnet

Claims (10)

A support plate including an opening;
a mirror plate provided within the opening and reflecting input light;
At least three springs are provided around an edge of the mirror plate and have both ends connected to the support plate and the mirror plate, respectively; and
At least three conductive bands provided from each spring of the at least three springs through the mirror plate to a spring provided adjacent to one direction of each spring,
A MEMS (Micro Electro Mechanical Systems) scanner, wherein each spring has two conductive bands connected to adjacent springs in both directions. According to paragraph 1,
The at least three springs
A MEMS scanner, characterized in that it is formed along a circular orbit or a spiral orbit. According to paragraph 2,
The MEMS scanner is
A MEMS scanner comprising a circular magnet or a circular conductor provided below the at least three springs and forming a radial magnetic field passing through the at least three springs. According to paragraph 3,
The mirror plate is circular,
A MEMS scanner, wherein the at least three conductive bands pass along an edge of the mirror plate. According to paragraph 4,
The at least three springs
A MEMS scanner, characterized in that when a drive signal is sequentially applied to the at least three conductive bands, they move sequentially up and down through electromagnetic force generated in the conductive bands. According to clause 5,
A MEMS scanner, wherein the input light reflected by the mirror plate forms a circular pattern or a spiral pattern. According to clause 6,
The MEMS scanner is
It further includes a refractive lens that is spaced apart from the mirror plate and refracts the input light reflected by the mirror plate,
The refractive lens is
A MEMS scanner, wherein the incident surface on which the reflected incident light is incident or the refractive surface on which the reflected incident light is refracted is an omnidirectional lens having a dome shape. According to paragraph 1,
The at least three springs
a body portion provided around an edge of the mirror plate;
a first connection part provided at a clockwise end of the body and connecting the body and the mirror plate; and
A MEMS scanner comprising a second connection portion provided at a counterclockwise end of the body portion and connecting the body portion and the support plate. According to clause 8,
The at least three springs
A MEMS scanner, characterized in that the body portion is provided along an edge of the 180° area of the mirror plate. According to clause 8,
The at least three springs
A MEMS scanner, characterized in that the body portion is provided along an edge of the 360° area of the mirror plate.

Images