JP2006018250A - Mems mirror scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MEMS mirror scanner structure that can realize high-speed scanning equal to or more than a polygon mirror scanner, that aims for example to realize high precision scanning in use for laser printing, and that is in particular intended to optimize the shape, dimension, etc., of a scanning mirror itself. <P>SOLUTION: The high precision and miniaturization can be attained by necessarily enlarging the range of an optical path that needs more as an angle of incidence becomes lower (smaller). In other words, with the angle of incidence in the range of 25-90° in the direction orthogonal to the target surface of emission, the scanning mirror needs to have a ratio of the length (b) in the direction of the oscillation axis to the length (a) in the direction orthogonal to the axis as (a≥b, a:b=(1.0 to 2.0):1), or (a<b, a:b=1:(1.001 to 2)). In addition, a space around the mirror is made smaller in the incidence side and larger in the exiting side, with a light transmitting window shaped asymmetrically in the incidence/exiting sides with respect to the mirror. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a compact mirror scanner suitable for laser printer applications capable of high-speed scanning, and more specifically, a novel electrostatic scanner using a micro-electro-mechanical system (hereinafter referred to as MEMS) using a silicon substrate. The present invention relates to a drive type MEMS mirror scanner.

  Conventionally, polygon mirror scanners have been used as devices used as scanner engines in applications such as laser printers, which can rotate a polygonal column mirror around its axis at high speed, realizing high-speed scanning operation ( Patent Document 1).

  In recent years, using a micromachining technique such as etching or film formation on a semiconductor substrate such as silicon, for example, a scanning mirror formed by forming a required groove is supported by a suspension beam so as to be swingable, and around the mirror and the groove. Various electrostatically driven mirror scanners have been proposed in which an electrostatic force is generated by an electrode pair provided to swing the mirror (Patent Documents 2 and 3).

  The electrostatic drive type mirror scanner is literally driven by an electrostatic force, and can change the reflection path of incident light according to the rotation angle about the suspension beam, and can switch and scan laser light. Can be implemented. However, the driving speed is much lower than that of the polygon mirror scanner.

  On the other hand, an electromagnetically driven mirror scanner having a magnetic field generating means for generating a parallel magnetic field in a basic structure and a scanning mirror supported so as to be swingable by a rod-like torsion bar has a large electromagnetic driving force, deflection angle and operating frequency. There is an advantage that it is easy to improve.

In addition, the electromagnetically driven mirror scanner, which employs a gimbal structure optical deflector and has a deflection mirror element array in which a silicon substrate and a plurality of polyimide films and metal films are stacked and arranged in a parallel magnetic field, is elastic By using a polyimide film having a mesh-like portion as a member, for example, it has a resonance frequency of 4000 Hz with a mirror size of 4.5 mm × 3.3 mm and enables high-speed scanning (Patent Document 4).
JP 5-119279 A JP2002-311376 JP2003-015064 JP2003-270558

  The MEMS mirror scanner, which uses a silicon substrate to support a mirror with a size of several mm square so that it can be swung with a suspension beam, is easier to miniaturize than a polygon mirror scanner. In addition, there are no rotating bodies and dust generation is free. Furthermore, various advantages such as power saving, low noise, low vibration, and shortened start-up time can be obtained.

  To enable high-speed scanning comparable to or higher than that of polygon mirror scanners, especially for laser printer applications, a large-size scanning mirror is required to obtain the required printing resolution. It is necessary to operate at a high speed and with a large amplitude.

  However, there have been many proposals regarding the device configuration and manufacturing method for the scanning mirror of the MEMS mirror scanner, but no proposal has been made regarding the optimal design for the shape and size of the optical system.

  In addition, to increase the speed (high frequency) of a MEMS mirror scanner with a large scanning mirror, for example, it is necessary to increase the rigidity of the torsion bar. However, if the rigidity of the torsion bar is increased, the driving force is low particularly in the electrostatic type. There is a problem that the mirror cannot be driven with a sufficient operating amplitude.

  The present invention can achieve high-speed scanning equivalent to or higher than that of a polygon mirror scanner in a MEMS mirror scanner, for example, to achieve high-accuracy scanning in laser printer applications, and in particular, the optimum shape, dimensions, etc. of the scanning mirror itself The purpose is to provide a MEMS mirror scanner with a simplified structure.

  Furthermore, the present invention provides a structure having a flexible mirror support structure that can be driven by a driving force with a small electrostatic force, and an increase in driving force in an electrostatically driven MEMS mirror scanner in which the scanning mirror itself is optimized. An object is to provide a MEMS mirror scanner having a configuration capable of increasing and securing the capacitance.

  As a result of various studies on the incidence of light to the scanning mirror and the reflected light path for the purpose of realizing high-accuracy scanning in laser printer applications, the inventors have found that the incident angle is 25 ° with respect to the mirror surface. In the case of the 90 ° range, it is necessary to increase the range of the light path as the incident angle becomes shallower (smaller), and the scanning mirror swing axis direction length (b) and the direction length perpendicular to the swing axis ( It was found that the relationship of a) should be (a ≧ b, a: b = (1.0 to 2.0): 1) or (a <b, a: b = 1: (1.001 to 2)).

  In addition, as a result of various studies on the passage of incident / reflected light from a scanning mirror whose length in a direction perpendicular to the swing axis is not hindered, the inventors have taken a large space around the mirror to achieve the purpose. On the other hand, in order to reduce the size, it is necessary to make the minimum necessary. However, since the necessary range is small on the incident side and large on the output side, the necessary minimum is achieved by making the space between the incident side and the output side asymmetric. In addition, in the case where the scanning mirror is housed, the light transmission window has an asymmetric shape on the incident / exit side with respect to the mirror, thereby achieving high accuracy and downsizing. I found out.

  Further, the inventors have found that the configuration of the MEMS mirror scanner in which the shape and dimensions are optimized can be applied to any configuration of the MEMS mirror scanner regardless of the principle of the driving source.

  Therefore, the inventors of the present invention have provided a flexible mirror support structure that can be driven by a driving force with a small electrostatic force and a sufficient electrostatic capacity for the electrostatic drive type MEMS mirror scanner that has been optimized for the shape and dimensions described above. As a result of diligent investigation for the purpose of ensuring the capacity, when assuming a square scanning mirror of the required dimensions, the mirror is supported by a pair of (two) suspension beams in two opposing directions, and Combining and disposing comb-shaped electrodes in the suspension beam direction (oscillating axis direction) to provide a capacitance drive unit basically increases the resonance frequency of the mirror and increases the capacitance of the drive unit. It was found that it can be increased.

  In addition, the inventors of the present invention have a higher resonance frequency when the mirror supported by the pair of (two) suspension beams is a rectangular mirror rather than a square mirror and a longer suspension beam is provided on the long side. Further, the inventors have found that the resonance frequency can be further increased by dropping the mass of the outermost peripheral portion as an ellipse or a long ellipse from a rectangle, and the present invention has been completed.

  That is, the present invention is a MEMS mirror scanner configured by stacking with only a main substrate having a scanning mirror configured to be swingable and supported by a suspension beam formed on the substrate or with another substrate, and an incident angle of light is a surface to be emitted. The relationship between the mirror length (a) in the direction orthogonal to the scanning axis of the scanning mirror and the mirror width (b) in the direction of the scanning axis of the scanning mirror is A MEMS mirror scanner, wherein a ≧ b, a: b = (1.0 to 2.0): 1) or (a <b, a: b = 1: (1.001 to 2)).

  Further, according to the present invention, the scanning mirror separately formed by providing a gap in the substrate can be swingably supported by the suspension beam, and only the main substrate in which the inner periphery of the gap accommodating the mirror forms a light transmission window, or another substrate And a mirror in which the gap in the direction perpendicular to the swing axis of the scanning mirror is determined from the substrate thickness, the swing angle of the mirror, and the incident angle of light on the mirror The MEMS mirror scanner is characterized in that the reflection of light from the light is enlarged so that the light can pass through the light transmission window.

Further, the inventors of the MEMS mirror scanner configured to expand the light transmission window,
A configuration in which the incident angle of light is in the range of 25 ° to 90 ° with respect to the orthogonal direction of the surface to be emitted, and high-speed scanning can be realized,
The relationship between the mirror length (a) in the direction perpendicular to the swing axis of the scanning mirror and the mirror width (b) in the swing axis direction of the scanning mirror is (a ≧ b, a: b = (1.0 to 2.0): 1 ) Or (a <b, a: b = 1: (1.001 to 2)), a configuration capable of realizing high-speed scanning with various and various specifications,
The direction of the light transmission window perpendicular to the swing axis of the scanning mirror is the incidence and reflection direction of light, and the gap length is enlarged in the reflection direction or both the incidence and reflection directions. Asymmetric or symmetric, functional configuration,
The light transmission window formed in the inner periphery of the gap containing the scanning mirror has a passage or a slit extending from the inner periphery of the gap to the outer periphery of the substrate or the outer periphery of the substrate, and has a configuration excellent in manufacturability,
The gap length L from the enlarged oscillating shaft provided in the light reflection direction in the direction perpendicular to the oscillating axis of the scanning mirror is more than 1/2 of the scanning mirror length in the same direction, realizing high-speed scanning Possible configurations,
We propose together.

  The MEMS mirror scanner according to the present invention requires, for example, a necessary optical path and an outer diameter of the mirror of 3 mm or more and an optical amplitude by the mirror of 50 ° or more when realizing the performance of 600 dpi required for a laser printer. When light is incident in a direction parallel to the scanning drum, the light enters the scanning mirror surface in the range of 45 ° to 90 °. In addition, the incident light can pass through without any trouble, and the size of the substrate used for device fabrication can be optimized to the minimum necessary to achieve both high-precision scanning and device miniaturization technical issues.

  The MEMS mirror scanner according to the present invention is configured so that the incident angle of light on the mirror is in the range of 25 ° to 90 ° with respect to the surface to be emitted, that is, the direction orthogonal to the scanning drum, for example, a laser beam unit on the front side of the drum In this configuration, it is possible to arrange a mirror scanner that has an optimal optical path and achieves the above-described high-accuracy scanning and device miniaturization.

  The electrostatic drive type MEMS mirror scanner according to the present invention has a flexible scanning mirror support structure that can be driven even with a driving force with a small electrostatic force, and a capacitive drive unit is arranged along a longer suspension beam. Since a large electrostatic capacity is secured, it is possible to replace the polygon mirror scanner, and since there is no rotating body, it is dust-free and can be made smaller than before, and the optical system can be made smaller. Lens saving, power saving, noise reduction, shortening of startup time, etc. can be realized.

  The electrostatic drive type MEMS mirror scanner according to the present invention is a large scanning mirror having a mirror length of, for example, 4 mm or more, particularly a large mirror that matches an elliptical or oblong laser light shape used in a laser printer. It can be driven with a resonance frequency and an amplitude of ± 15 ° or more, and can achieve the 300 dpi and 600 dpi performance required by laser printers.

  The electrostatic drive type MEMS mirror scanner according to the present invention is formed on a semiconductor substrate such as silicon using a micromachining technique such as etching or film formation, and further includes a DC power source and an AC power source for electrostatic drive and control. Since it can be formed on a substrate and has a simpler and more manufacturable structure than a polygon mirror scanner or an electromagnetically driven MEMS mirror scanner, there is an advantage that it can be provided at low cost.

  The electrostatic drive type MEMS mirror scanner according to the present invention has a configuration in which a suspension beam of the same material formed on a semiconductor substrate such as silicon can be used without increasing its rigidity. For example, the conventional configuration uses a polyimide film for a torsion bar. Compared with the mirror operation stability (especially jitter).

  Fig. 1 is a conceptual diagram showing the optical path and scanning mirror outer diameter required to achieve A4 size and 600 dpi performance with a laser printer. The diameter (beam width) of optical path 2 required for 600 dpi is 3.1. mm. Here, it is assumed that the incident light to the scanning mirror 3 comes from the right side in the figure as a direction parallel to the scanning drum 1. When the outer diameter of the scanning mirror 3 is 3.1 mm, which is the same as that of the optical path 2, if the mirror 3 is driven with a large amplitude for high speed, the incident light cannot be reflected by the mirror 3 and emitted to the end of the drum 1. It is clear.

  As shown in FIG. 2A, assuming that the optical path 2 has a diameter of 3.1 mm and is incident on the scanning mirror 3 at an angle of 51 °, as shown in FIG. Since the amplitude is required to be 50 ° or more, it can be seen that the size of the scanning mirror 3 is much larger than the diameter of the optical path 2 in order to reflect all incident light to the drum.

That is, when the beam width is D, the incident angle is θ ₂ , the scanning mirror length is x, the half amplitude angle θ ₁ of the scanning mirror is θ _4, and the scanning mirror angle with respect to the normal of the beam is θ ₄ , the mirror angle θ ₄ is θ ₄ = 180− (θ ₂ +90) + θ ₁ and the scanning mirror length a is a = D / cos θ ₄ .

  Here, the length a required by the scanning mirror 3 is 4.98 mm when calculated by the above equation, which indicates that it is necessary to be 1.61 times the diameter of the optical path 2. Therefore, the outer diameter of the scanning mirror is at least equal to the optical path diameter, and at most twice the optical path diameter is required.

  FIG. 3 shows a scanning mirror and a light transmission window formed on the substrate according to the present invention. As shown in FIG. 3A, a scanning mirror 12, which is separately formed by providing a required gap 11 on the substrate 10, is swingably supported by a pair of suspension beams 13, 13, and inside the inner periphery of the gap 11 in which the mirror 12 is accommodated. Is a configuration in which the light transmission window 14 is formed.

As shown in FIG. 3B, when the mirror 12 is viewed in a cross-section in the direction X perpendicular to the swinging axis direction Y of the scanning mirror 12, if the incident angle θ ₂ to the mirror 12 is 45 °, Since the light amplitude by the scanning mirror 12 is required to be 50 ° or more, the reflected light does not hit the back surface of the substrate 10 and exit to the drum in the light transmission window 14 with the gap 11 set first.

  However, here, by making the gap 11 in the direction X orthogonal to the oscillation axis direction Y widened and the light transmission window 15 enlarged, all incident light within the range of light amplitude by the scanning mirror 12 can be obtained without any problem. Can be reflected.

  In this way, in order for incident / reflected light from the scanning mirror 12 to pass without hindrance, the space around the mirror 12 may be large, but as shown in FIG. In order to reduce the size of the required mirror outer diameter, it must be the minimum necessary.

  3A and 3B, since the necessary range is small on the incident side and large on the output side, it can be seen that the minimum necessary space can be obtained by making the space on the incident side and the output side asymmetric.

  When the number of suspension beams is 1, the mirror width in the swing axis direction of the scanning mirror is preferably shorter than the mirror length in the direction perpendicular to the swing axis of the scanning mirror, and is 50% or less of the mirror length (a) The reason is that the mirror length a is related to the resolution in the main scanning direction of the printer, the width dimension b is related to the resolution in the sub scanning direction of the printer, and the resolution in the main scanning direction is the mirror length. It depends on the frequency. Furthermore, since the resolution in the sub-scanning direction can be set lower than the resolution in the main scanning direction due to the function of the printer, the mirror width b is proportional to the extreme inertia ratio, so if this is 50% or less, the resolution requirement and natural frequency are reduced. It is desirable because both can be satisfied in a well-balanced manner. However, when a multi-beam having a plurality of suspension beams is used, it may be necessary to increase the dimension in the oscillation axis direction in accordance with the number of beams.

  More specifically, the relationship between the mirror length (a) perpendicular to the swing axis of the scanning mirror and the mirror width (b) in the swing axis direction of the scanning mirror is (a ≧ b, a: b = (1.0 -2.0): 1) or (a <b, a: b = 1: (1.001-2)).

  In the present invention, the shape of the scanning mirror may be any of a rectangle, a diamond, a polygon, a circle, and an ellipse. Further, the shape is preferably a polygon rather than a rectangle or rhombus, an ellipse rather than a circle, and a track shape.

  In this invention, the ratio of the length of the scanning mirror in the swing axis direction to the length in the direction perpendicular to the swing axis is within the above range, but the gap in the direction perpendicular to the swing axis of the scanning mirror is defined as The reflection of light from the mirror, which is determined from the swing angle of the mirror and the incident angle of light on the mirror, may be enlarged so that it can pass through the light transmission window.

More specifically, in FIG. 4, the dimensions to be enlarged are shown in FIG. 4 from the scanning mirror half amplitude angle θ ₁ , the incident angle θ ₂ , the exit angle θ ₃ , the scanning mirror length a, and the swing axis of the scanning mirror. When the distance to the end of the light transmission window is the gap length L, the emission angle θ ₃ is θ _{3 =} θ ₂ − (2θ ₁ ), and the gap length L is expressed by the following equation.
L = (a / 2) sinθ ₁ / tanθ ₃ + (a / 2) cosθ ₁

  In this invention, the shape of the light transmission window is such that the direction perpendicular to the oscillation axis of the scanning mirror is the incident and reflection direction of light, and the gap length is enlarged in both the incident and reflection directions, and the direction of the oscillation axis of the mirror In order to reduce the size, of course, the gap length is enlarged in the reflection direction, and an asymmetric shape in the direction of the swing axis of the mirror is desirable.

  In the present invention, the light transmission window formed in the inner periphery of the gap that accommodates the scanning mirror may have a path or a slit extending from the inner periphery of the gap to the outer periphery of the substrate or the outer periphery of the substrate.

  As shown in FIG. 5A, an electrostatically driven MEMS mirror scanner 20 according to the present invention forms a scanning mirror 21 between a pair of suspension beams 22 and 23 formed and arranged on the same straight line of a semiconductor substrate such as silicon. The basic structure is that the torsion bar portions 24 and 25 are provided with fixing portions via S-shaped hinges at the ends of the beams 22 and 23, and the mirror 21 is swingably supported using the straight line as a swing axis. And

  The S-shaped hinge 40 can be disposed in the suspension beam 22 as shown in FIG. 5B. The scanning mirror 21 and suspension beams 22 and 23 shown in the figure are formed in the substrate, but only the parts are illustrated in the drawing, and both ends of the beams 22 and 23 have hinges connected to the substrate. The structure is supported here, and the light transmission window is also omitted.

  In addition, the electrostatic drive type MEMS mirror scanner 20 according to the present invention displays only the parts without displaying the substrate. In the example of FIG. 5, the electrostatic capacity drive units 26 and 27 are arranged along the suspension beams 22 and 23. The capacitance driving units 26 and 27 are arranged so that the comb teeth extending from the suspension beams 22 and 23 are movable and mesh with the comb teeth 26a, 26b, 27a and 27b fixed to the substrate side. It is characterized by.

  FIG. 6 shows a configuration example in which the capacitance driving unit is arranged only on one side of the suspension beam, and shows a configuration of the substrate on which the scanning mirror and the suspension beam are formed.

  The MEMS device is configured by laminating two substrates. The upper substrate is provided with a circular scanning mirror 31 at the center of the substrate 30 as shown in FIG. The scanning mirror 31 is provided on the substrate 30 side via the hinges 34 and 35 at both ends thereof, and at the base of the connecting portion of the scanning mirror 31 via the hinges 36 and 37 of the S-shaped torsion bar structure. Supported.

  Swing-side comb teeth 38 extending in a direction orthogonal to the swing axis are formed on the longitudinal side surfaces of the suspension beams 32 and 33, and a capacitance driving source is formed by fixed-side comb teeth provided on a lower substrate (not shown). As a result, the scanning mirror 31 is driven to swing through the suspension beams 32 and 33.

  The suspension beams 32 and 33 can be supported by various bent hinges in addition to the linear and S (Z) -shaped hinges described above. Depending on the conditions such as when the teeth are on both sides, it can be configured to support the scanning mirror 31 by providing the hinges at multiple locations, and the movable side and fixed side for support according to the bent shape of the hinge etc. And can be configured.

  The lower substrate (not shown) is hollowed so that the scanning mirror 31 of the upper substrate plate 30 and the suspension beams 32, 33 can swing, and is paired with the upper swing-side comb teeth. Many fixed comb teeth that can constitute a capacitive drive source are arranged. Further, when the upper layer substrate and the lower layer substrate are laminated, the corresponding island portion is also formed on the lower layer side so that the fixing portion formed on the upper layer plate side is fixed.

  Although not shown, a large number of thin and deep grooves can be formed on the surface of the scanning mirror, and the plurality of grooves have a function of reducing the mass of the scanning mirror and reducing dynamic deformation. That is, the MEMS device improves optical resolution by minimizing all of its dynamic deformation.

  In addition, when forming each part of a scanning mirror upper layer part by an etching, many groove | channels are controlled so that the groove width and depth may become predetermined value simultaneously. Alternatively, a method of covering the surface other than the surface of the scanning mirror and forming grooves on the surface by etching can also be employed.

  Furthermore, in order to reduce the rigidity and weight of the scanning mirror, it is possible to have a structure in which the substrate and the beam member for weight reduction are bonded together, and the beam member can be of various types such as H type, I type, U type, and mountain type. It is advisable to optimize the arrangement and number by the finite element method.

  In the above, the MEMS mirror scanner having a structure in which the upper layer plate and the lower layer plate on which the scanning mirror and the suspension beam are provided is described. However, the electrodes are arranged on the comb-like structure in the same substrate on which the suspension beam and the scanning mirror are formed. As a matter of course, the MEMS mirror scanner can be configured with only the upper layer plate including the capacitance driving source, such as the configuration.

  In the present invention, applying mass reduction means to the non-reflecting back surface of the scanning mirror and / or each suspension beam is effective in controlling the resonance frequency of the movable part or in obtaining a dynamic balance. As mass reducing means, a large number of minute through holes and holes are provided, and a multi-rib structure, honeycomb structure, transverse H-shaped (I-beam) structure, T-shaped structure, and chevron structure are provided at the required location. For example, it may be selected appropriately according to the purpose and installation location. Furthermore, it is possible to provide means for reducing the inertia ratio. For example, by reducing the mass of a certain location and increasing the mass of another location at the same time, the mass does not change, but the inertial rate of the part is reduced, and the effect of increasing the frequency and swing angle can be obtained. .

  In the present invention, the substrate to be used is not particularly limited, but in order to realize high-speed scanning, the thickness is desirably 0.05 mm or more, and a single-layer substrate or a bonded substrate can be appropriately employed.

  Further, the scanning mirror can have a structure having a film formation or a bonding layer on the surface. A known silicon substrate, a silicon substrate having a bonding layer, a glass substrate, or the like can also be used.

  Further, when the MEMS mirror scanner is configured with one substrate, it is desirable that the thickness of the substrate on which the suspension beam and the scanning mirror are provided is equal to or greater than the thickness of the scanning mirror. In the case of adopting a laminated structure, it is desirable that the thickness of the substrate on which the suspension beam and the scanning mirror are provided is equal to or less than the thickness of the scanning mirror.

  In this invention, if the suspension beam, the scanning mirror, the entire movable part of the capacitance driving unit is arranged in a vacuum atmosphere, or the resistance reduction configuration for amplifying the amplitude angle of the mirror is adopted, the viscosity of the air is reduced. It is possible to design the shape of each part without consideration.

  In the present invention, an electrostatically driven MEMS mirror scanner in which a mirror that is swingably supported by a suspension beam is formed on a target semiconductor substrate is manufactured by patterning and laminating thin films of various materials on the substrate. Manufactured by surface micromachining, or bulk micromachining such as etching the substrate itself or further performing film formation.

  In the electrostatic drive type MEMS mirror scanner of the present invention, the comb-shaped electrode configuration has been described as the capacitive element of the drive source. However, the planar electrode configuration is used as an aid for mirror positioning and correction. Is possible.

  In the electrostatic drive type MEMS mirror scanner of the present invention, first, a DC voltage is applied to the comb electrode for electrostatic drive so as to match or approximate the resonance frequency of the micromirror. Then, an AC voltage can be applied between the driving electrodes in order to drive the mirror in a swinging manner.

  The specific resonance frequency of the scanning mirror is determined by the configuration of the suspension beam. Furthermore, the spring constant of the rotation axis of the mirror, the expected swing movement pattern of the mirror, the required mirror amplitude, that is, the rotation angle, etc. The DC voltage value may be determined in consideration of how much resonance should occur, whether the deflection angle should be maximized, or within a certain range.

Example 1
In the same configuration as in FIG. 5 described above, only one side of the electrostatic drive source is arranged on both sides of the suspension beam, and the S-shaped hinges provided at the connecting part of the scanning mirror are accordingly installed in the suspension beam end and the suspension beam. A plurality of electrostatically driven MEMS mirror scanners having the dimensions and characteristics shown in Table 1 were prepared by arranging a plurality at predetermined intervals. As a result, the scanning mirror has a resonance frequency of 1500 Hz and a deflection angle of ± 15 °.

Example 2
As the electrostatic drive type MEMS device, basically the same configuration as that of the first embodiment described above is adopted, and an elliptical shape is adopted for the scanning mirror formed on the upper layer substrate. Each suspension beam has 6 torsion bars including the S-shaped hinge at its end.

  Furthermore, here, the torsion bar close to the mirror has one S-shaped hinge through the fixed part, and the remaining torsion bars except for the hinge type at the end are two spirals with respect to one fixed part. Three components having springs were provided, and a configuration in which a total of eight torsion bars were provided was produced. As a result, the resonance frequency of the scanning mirror was 2000Hz and the deflection angle was ± 16.25 °.

Example 3
The electrostatic drive type MEMS device of Example 3 basically adopts the same configuration as that of the above-described Example, and the scanning mirror formed on the upper layer plate has a long oval shape in the direction of each suspension beam. Adopted. As a result, the scanning mirror had a resonance frequency of 3000 Hz and a deflection angle of ± 22 °.

a: Scanning mirror x-axis direction (vertical) dimension,
b: Scanning mirror y-axis direction (width) dimension,
c: torsion bar width,
L: Length of one torsion bar (expanded length)
n: number of torsion bars,
n _c : number of combs,
t: Substrate thickness (assuming t> c),
w: comb cutting depth,
δ: Gap between drive electrodes
K: Spring constant (overall),
I: Inertia rate around the swing axis

  The electrostatic drive type MEMS mirror scanner according to the present invention includes a digital copy, a barcode reader, a laser printer, a confocal microscope, an optical fiber network component, a projection display for a projector, a rear projection TV, a display that can be mounted, an in-vehicle laser Applications include radar and military laser tracking and guidance systems.

  The electrostatic drive type MEMS mirror scanner according to the present invention has a flexible scanning mirror support structure that can be driven even with a driving force with a small electrostatic force, and a capacitive drive unit is arranged along a longer suspension beam. The large mirror that matches the elliptical or oblong laser beam shape used in laser printers with a resonance frequency of 1.5 kHz or more is possible. It can be driven with an amplitude of ± 15 ° or more, and can achieve the 300 dpi and 600 dpi performance required by laser printers.

FIG. 5 is a conceptual explanatory diagram showing an optical path and a scanning mirror outer diameter required when a mirror scanner achieves a required performance in a laser printer. A and B are explanatory diagrams showing the relationship between the optical path of the mirror scanner and the scanning mirror. A and B are explanatory views showing the positional relationship between the incidence and emission of laser light and the substrate on the substrate on which the scanning mirror is formed. It is explanatory drawing which shows the relationship between the optical path | route of a mirror scanner, and a scanning mirror. It is explanatory drawing which shows one Example of the electrostatic drive type MEMS mirror scanner by this invention, A shows the whole part, B shows the other Example of a suspension beam. It is explanatory drawing which shows one Example of the electrostatic drive type MEMS mirror scanner by this invention.

Explanation of symbols

1 Scanning drum
2 Optical path 2
3 Scanning mirror
10 Board
11 Gap
12,21,31 Scanning mirror
13,22,23,32,33 Suspension beam
14 Light transmission window
20 MEMS mirror scanner
24,25 Torsion bar
26,27 Capacitance drive
26a, 26b, 27a, 27b, 38 comb teeth
40 S-shaped hinge

Claims (22)

This is a MEMS mirror scanner that consists only of a main substrate that has a scanning mirror that can be oscillated and supported by a suspension beam formed on the substrate, or that is laminated with another substrate, and the incident angle of light is perpendicular to the direction perpendicular to the surface to be emitted. In the range of 25 ° to 90 °, the relationship between the mirror length (a) perpendicular to the scanning mirror's swing axis and the mirror width (b) of the scanning mirror's swing axis is (a ≧ b, a : b = (1.0 to 2.0): 1) or MEMS mirror scanner that is (a <b, a: b = 1: (1.001 to 2)). The scanning mirror formed separately by providing a gap in the substrate can be swingably supported by the suspension beam, and the inside of the gap containing the mirror is formed only on the main substrate having a light transmission window or laminated with another substrate. This is a MEMS mirror scanner, and the gap in the direction perpendicular to the oscillation axis of the scanning mirror is a reflection of light from the mirror determined by the substrate thickness, the oscillation angle of the mirror, and the incident angle of light on the mirror. A MEMS mirror scanner that has been enlarged to allow light to pass through. 3. The MEMS mirror scanner according to claim 2, wherein the incident angle of light is in the range of 25 ° to 90 ° with respect to the orthogonal direction of the surface to be emitted. The relationship between the mirror length (a) in the direction perpendicular to the swing axis of the scanning mirror and the mirror width (b) in the swing axis direction of the scanning mirror is (a ≧ b, a: b = (1.0 to 2.0): 1 3. The MEMS mirror scanner according to claim 2, wherein (a <b, a: b = 1: (1.001 to 2)). The direction of the light transmission window perpendicular to the swing axis of the scanning mirror is the incidence and reflection direction of light, and the gap length is enlarged in the reflection direction or both the incidence and reflection directions. 3. The MEMS mirror scanner according to claim 2, wherein the MEMS mirror scanner is asymmetric or symmetric. 3. The MEMS mirror scanner according to claim 2, wherein the light transmission window formed in the inner periphery of the gap that accommodates the scanning mirror has a passage or a slit extending from the inner periphery of the gap to the outer periphery of the substrate or the outer periphery of the substrate. 3. The gap length L from the enlarged swinging shaft provided in the light reflection direction in a direction perpendicular to the swinging shaft of the scanning mirror is 1/2 or more of the length of the scanning mirror in the same direction. MEMS mirror scanner. 3. The electrostatic drive type MEMS mirror scanner according to claim 1, wherein the shape of the scanning mirror is a rectangle, a diamond, a polygon, a circle, or an ellipse. 3. The electrostatic drive type MEMS mirror scanner according to claim 1, further comprising a connecting portion having a hole between each suspension beam and the scanning mirror. 3. The electrostatic drive type MEMS mirror scanner according to claim 1 or 2, further comprising a torsion bar portion at each suspension beam end opposite to the scanning mirror. 3. The electrostatic drive type MEMS mirror scanner according to claim 1, further comprising at least one torsion bar portion in each suspension beam. 3. The electrostatic drive type MEMS mirror scanner according to claim 1, further comprising a plurality of torsion bar portions along one side of each suspension beam. 3. The electrostatic drive type MEMS mirror scanner according to claim 1, wherein mass reducing means or inertia ratio reducing means is applied to the non-reflecting back surface of the scanning mirror and / or each suspension beam. 14. The electrostatic drive type MEMS mirror scanner according to claim 13, wherein the mass reduction means is any one of a through hole, a hole, a multi-rib structure, or a combination thereof. 3. The electrostatic drive type MEMS mirror according to claim 1, wherein the electrostatic capacity drive unit has a comb-like structure formed in a direction orthogonal to the swing axis of the scanning mirror in the same substrate as the suspension beam. Scanner. 3. The electrostatic capacity driving unit according to claim 1, wherein the electrostatic capacity driving unit is configured in a comb-like structure in the same substrate on which the suspension beam and the scanning mirror are formed, and the electrode is disposed in the same structure. Drive type MEMS mirror scanner. Claim 1 or Claim 2 wherein the substrate on which the suspension beam and the scanning mirror are provided is the upper layer plate, the other substrate on which the pattern of the required shape is formed is stacked as the lower layer plate, and the mirror oscillation space is formed on the lower layer plate side. The electrostatic drive type MEMS mirror scanner described. The capacitance driving unit of the upper layer plate is configured with a comb-like structure formed in a direction orthogonal to the swing axis of the scanning mirror in the same substrate as the suspension beam, and the upper layer plate is paired with the comb-like structure of the upper layer plate. 18. The electrostatic drive type MEMS mirror scanner according to claim 17, wherein the electrostatic capacitance drive unit is disposed by providing a comb-like structure that forms the structure. 18. The electrostatic drive type MEMS mirror scanner according to claim 15, wherein the substrate on which the suspension beam and the scanning mirror are provided is a single layer substrate or a bonded substrate. 17. The electrostatic drive type MEMS mirror scanner according to claim 15 or 16, wherein the thickness of the substrate on which the suspension beam and the scanning mirror are provided is equal to or greater than the thickness of the scanning mirror. 18. The electrostatic drive type MEMS mirror scanner according to claim 1, wherein the scanning mirror has a film forming or bonding layer on a surface thereof. 3. The electrostatic drive type MEMS mirror scanner according to claim 1, wherein the entire movable part of the suspension beam, the scanning mirror, and the electrostatic capacity drive part is disposed in a vacuum atmosphere.

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