JP2011095523A - Optical reflecting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve highly-accurate self-excited driving of an optical reflecting element. <P>SOLUTION: This element includes a mirror part 9 and a connected vibrator 10. The vibrator 10 has a drive element 16 and a monitor element 17 arranged separately by a splitting groove 30A formed on a substrate 19, and lower electrode layers 21 of the drive element 16 and the monitor element 17 are connected to a common external electrode, and the shortest conduction route between the lower electrode layer 21 of the monitor element 17 and the lower electrode layer 21 of the drive element 16 is set to be longer than a distance from the lower electrode layer 21 of the monitor element 17 to the common external electrode by the splitting groove 30A at an optional point where the monitor element 17 and the drive element 16 are arranged adjacently. Hereby, detection accuracy of monitor elements 17, 18 can be heightened, and highly-accurate self-excited driving of the optical reflecting element 8 becomes possible. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical reflection element used in a display device or the like.

  FIG. 9 shows a conventional optical reflecting element 1. This optical reflection element 1 is connected to a mirror part 2, a pair of vibrators 3, 4 connected to the end of the mirror part 2, and these vibrators 3, 4. And a frame 5 that surrounds the outer periphery of the mirror unit 2, and a pair of vibrators 6 and 7 that are connected to the ends of the frame 5.

  The vibrators 3 and 4 have a meander shape with the S1 axis parallel to the Y axis as the central axis, and the vibrators 6 and 7 have the S2 axis parallel to the X axis as the central axis.

  If a drive element composed of a lower electrode layer, a piezoelectric layer, and an upper electrode layer is arranged on these vibrators 3, 4, 6, and 7, and a voltage is applied, the mirror unit 2 rotates about the S1 axis and the S2 axis. Can be made. And if light enters into the rotating mirror part 2, the reflected light can be scanned to the XY plane on a screen, for example, an image can be projected on a wall or a screen.

  Here, a monitor element comprising a lower electrode layer, a piezoelectric layer, and an upper electrode layer is provided on the vibrators 3, 4, 6, 7 and the mirror unit 2, and an electric signal detected by the monitor element is driven via a feedback circuit. If input to the upper electrode layer of the element, the optical reflection element 1 can theoretically be driven at the resonance frequency in theory, and a large amplitude can be maintained. Such a method is called a self-excited drive method.

  As prior art document information similar to this application, for example, Patent Document 1 is known.

JP 2008-040240 A

  Here, the self-excited drive may become substantially impossible as the drive frequency increases.

  The reason is considered that when the wiring distance of the ground electrode is increased, the resistance is increased, and a leak current flows between the adjacent monitor element and the upper electrode layer of the drive element.

  As a result, the detection accuracy of the monitor element is lowered, and self-excited drive cannot be performed.

  Therefore, an object of the present invention is to improve the detection accuracy of the monitor element and realize high-accuracy self-excited driving of the optical reflection element.

  And in order to achieve this object, the present invention comprises a mirror part and a vibrator coupled to the mirror part, the vibrator comprising a base material, an insulating layer formed on the base material, A drive element and a monitor element are disposed on the insulating layer separately by a dividing groove, and a concave groove having a bottom surface is formed on the base material immediately below the dividing groove between the drive element and the monitoring element. The bottom surface of the concave groove is composed of the base material, and the drive element and the monitor element are respectively laminated with a lower electrode layer, a piezoelectric layer, and an upper electrode layer. The lower electrode of the element is connected to a common external electrode, and at any point where the monitor element and the drive element are disposed adjacent to each other, the dividing groove causes the lower electrode of the monitor element to Shortest conduction path between the lower electrode of the live element was from the lower electrode of the monitoring element and longer than the distance to the common external electrode.

  As a result, the present invention can improve the detection accuracy of the monitor element and drive the optical reflection element with high accuracy by self-excitation.

  This is because the ground resistance of the lower electrode of the monitor element can be relatively lowered from the conduction resistance between the lower electrode of the monitor element and the lower electrode of the drive element by the above structure.

  Therefore, even if the wiring distance of the lower electrode layer is long, the leakage current can be suppressed from flowing between the upper electrode layers of the monitor element and the drive element.

  As a result, the detection accuracy of the monitor element can be improved, and the optical reflection element can be self-excited and driven with high accuracy.

The perspective view of the optical reflective element in Embodiment 1 of this invention (A) The perspective view of the 1st vibrator | oscillator of the optical reflection element, (b) Sectional drawing of the 1st vibrator | oscillator of the optical reflection element (S1-axis cross section of Fig.2 (a)) Sectional drawing of one 2nd vibrator | oscillator of the same optical reflective element (S2-axis cross section of FIG. 1) Sectional drawing of the other 2nd vibrator | oscillator of the optical reflection element (S2-axis cross section of FIG. 1) Block diagram for explaining a drive circuit of the optical reflection element Schematic diagram showing the operation of the first vibrator of the optical reflection element Sectional drawing of the principal part of the optical reflective element of another example in Embodiment 1 of this invention Sectional drawing of the principal part of the optical reflective element of another example in Embodiment 1 of this invention A perspective view of a conventional optical reflecting element

(Embodiment 1)
As shown in FIG. 1, the optical reflecting element 8 in the present embodiment is opposed to the mirror portion 9 through the mirror portion 9 and is connected to an end portion of the mirror portion 9. The vibrators 10 and 11 are connected to the first vibrators 10 and 11 and are opposed to the frame body 12 surrounding the outer circumferences of the first vibrators 10 and 11 and the mirror portion 9 with the frame body 12 therebetween. In addition, a pair of second vibrators 13 and 14 respectively connected to the frame body 12 and the second vibrators 13 and 14 and the second vibrators 13 and 14 and the frame body are connected. 12 and a frame-shaped support body 15 surrounding the outer periphery of 12.

  The first vibrators 10 and 11 and the second vibrators 13 and 14 have different resonance driving frequencies, and the frequency ratio is about 10 to 100 times. For example, in the present embodiment, the resonance frequency of the first vibrators 10 and 11 is 10 kHz, and the resonance frequency of the second vibrators 13 and 14 is about 200 Hz.

  Furthermore, the center axis S1 of the first vibrators 10 and 11 and the center axis S2 of the second vibrators 13 and 14 intersect, and in the present embodiment, they are in a relationship orthogonal to each other at the center of gravity of the mirror unit 9. The paired first vibrators 10 and 11 are line symmetric with respect to the central axis S2 of the second vibrators 13 and 14, and the paired second vibrators 13 and 14 are the first vibrator 10. , 11 with respect to the central axis S1.

  Furthermore, the first vibrators 10 and 11 according to the present embodiment have meander shapes in which a plurality of diaphragms 10A to 10D and 11A to 11D that are parallel to the X axis (perpendicular to the central axis S1) are connected in a folded manner on the same plane. It is. The second vibrators 13 and 14 have a meander shape in which a plurality of diaphragms 13A to 13E and 14A to 14E parallel to the Y-axis direction (perpendicular to the central axis S2) are connected in a folded manner on the same plane.

  Further, as shown in FIG. 2B, a drive element 16 and a monitor element 17 are arranged on the plurality of diaphragms 10A to 10D and 11A to 11D constituting the first vibrators 10 and 11, respectively. Yes.

  Further, as shown in FIG. 3, the first vibrators 10 and 11 and the second vibrators 13 and 14 are also provided on the plurality of diaphragms 13A to 13E constituting one of the second vibrators (13 in FIG. 1). Drive element 16 and monitor element 17 for detecting the vibration of the first vibrators 10 and 11 are arranged, and as shown in FIG. 4, the other second vibrator (14 in FIG. 1) is configured. On the plurality of diaphragms 14A to 14E, the drive elements 16 common to the first vibrators 10 and 11 and the second vibrators 13 and 14 and the monitor elements 18 for detecting vibrations of the second vibrator 14 are respectively provided. Is arranged.

  As shown in FIGS. 2B, 3, and 4, the drive element 16 is disposed on the base material 19, the insulating layer 20 formed on the base material 19, and the insulating layer 20. A lower electrode layer 21, a piezoelectric layer 22 stacked on the lower electrode layer 21, and an upper electrode layer 23 stacked on the piezoelectric layer 22 are provided.

  Similarly, the monitor elements 17 and 18 also include a base material 19, an insulating layer 20 formed on the base material 19, a lower electrode layer 21 disposed on the insulating layer 20, and the lower electrode layer 21. And the upper electrode layers 24 and 25 stacked on the piezoelectric layer 22.

  Further, in the present embodiment, the upper electrode layer 23 of the drive element 16 arranged on the first vibrators 10 and 11 and the second vibrators 13 and 14 is formed on the lead electrode 26 on the support 15 shown in FIG. Pulled out. Further, the upper electrode layer 24 of the monitor element (17 in FIG. 2B) disposed on the first vibrators 10 and 11 is drawn around the second vibrator 13 and drawn out to the lead electrode 27. Furthermore, the upper electrode layer (25 in FIG. 4) of the monitor element (18 in FIG. 4) disposed on the other second vibrator 14 is extracted to the extraction electrode 28. Furthermore, the lower electrode layer 21 of the drive element 16 and the monitor elements 17 and 18 shown in FIGS. 2B, 3 and 4 is drawn out to a common lead electrode 29 as shown in FIG.

  In addition, a common external electrode layer (not shown) to which the lower electrode layers of the monitor elements 17 and 18 and the drive element 16 are connected is laminated almost integrally with the support body 15, and the extraction electrode 29 is connected to the outside. Used for extracting the electrode layer.

  Further, as shown in FIGS. 2A, 2B, 3, and 4, on each of the diaphragms 10A to 10D, 11A to 11D, 13A to 13E, and 14A to 14E, a drive element 16 and a monitor element 17, Alternatively, the drive element 16 and the monitor element 18 are adjacently arranged in parallel, but are separated by a dividing groove 30 </ b> A formed on the common base material 19.

  Furthermore, a groove 30B is formed in the base material 19 between the drive element 16 and the monitor element 17 or between the drive element 16 and the monitor element 18 immediately below the dividing groove 30A, and the bottom surface of the groove 30B is A base material 19 is used. That is, the lower layer portion between the adjacent drive element 16 and the monitor element 17 or between the drive element 16 and the monitor element 18 is not completely separated but is connected by a part of the base material 19.

  In the present embodiment, a silicon wafer is used as the base material 19, but MgO or stainless steel may be used in addition to silicon.

The insulating layer 20 is silicon dioxide, the lower electrode layer 21 is platinum, the upper electrode layers 23, 24, 25 are gold, and the piezoelectric layer 22 is lead zirconate titanate (Pb (Zr _x , Ti _1-x ) O ₃ , x = 0.525), and the like. These can be thinned by vapor deposition, sol-gel, CVD, sputtering, or the like.

  The dividing groove 30A and the recessed groove 30B are patterned by dry etching or sequentially etching the piezoelectric layer 22, the lower electrode layer 21, and the insulating layer 20 after the upper electrode layers 23, 24, and 25 are patterned by dry etching or wet etching. Can be formed.

  Below, the drive method of the optical reflection element 8 in this Embodiment is demonstrated using the schematic diagram of a circuit block.

  First, as shown in FIG. 5, an electric signal (AC voltage) for driving the first vibrators 10 and 11 is input to the amplifier 31 and amplified. An electric signal (alternating voltage) for driving the second vibrators 13 and 14 is input to the amplifier 32 arranged in parallel with the amplifier 31 and amplified.

  In the present embodiment, an electric signal having a vibration frequency specific to the first vibrators 10 and 11 is input to the first vibrators 10 and 11, and the first vibrators 10 and 11 are driven to resonate. ing. In addition, the second vibrators 13 and 14 are inputted with an electric signal having a vibration frequency inherent to the second vibrators 13 and 14 to drive the second vibrators 13 and 14 to resonate. As a result, since it is always possible to drive at the resonance frequency, the first vibrators 10 and 11 and the second vibrators 13 and 14 can be driven efficiently and can be displaced greatly.

  The electrical signals described above are combined via impedance elements 33 and 34 such as resistors, and supplied to the extraction electrode 26.

  The synthesized electric signal is extracted from the extraction electrode 26 and flows to the upper electrode layer 23 common to the second vibrators 13 and 14 and the first vibrators 10 and 11 to drive the drive elements 16.

  The upper electrode layer 24 of the monitor element 17 disposed on the first vibrators 10 and 11 detects the displacement of the first vibrators 10 and 11 as an electric signal, and the electric signal is detected on the second vibrator 13. The lead electrode 27 is led out through the upper electrode layer 24 routed to the top. Further, the upper electrode layer 25 of the monitor element 18 disposed on the second vibrator 14 detects the displacement of the second vibrator 14 as an electric signal, and the electric signal is drawn out to the lead electrode 28.

  Then, the electrical signal drawn out to the lead electrode 27 is taken out via the filter 35 and inputted to the amplifier 31 again as shown in FIG.

  The electric signal drawn out to the lead electrode 28 is taken out through the filter 36 and inputted to the amplifier 32 again.

  In this way, the electrical signals output from the upper electrode layers 24 and 25 (monitor electrodes) of the monitor elements 17 and 18 are transmitted to the drive elements 16 of the first vibrators 10 and 11 and the second vibrators 13 and 14, respectively. By feeding back to the upper electrode layer 23 (drive electrode), the optical reflecting element 8 can be driven by self-excitation.

  As the impedance elements 33 and 34, in addition to the above-described resistors, reactance elements such as capacitors and coils, or combinations thereof may be used.

  Further, in the present embodiment, the common upper electrode layer 23 is routed to the drive elements 16 of the first vibrators 10 and 11 and the second vibrators 13 and 14 in order to apply the synthesized electric signal. The optical reflection element 8 can also be driven by the circuit configuration of FIG. 10. For example, the upper electrode layers 23 of the drive elements 16 of the first vibrators 10 and 11 and the second vibrators 13 and 14 can be electrically independent. Good.

  Next, the operation of the optical reflecting element 8 in the present embodiment will be described.

  In the present embodiment, as shown in FIGS. 2A and 2B, on the diaphragms 10A to 10D and 11A to 11D of the first vibrators 10 and 11, wide drive elements 16 are formed every other line. Has been. Accordingly, by applying an alternating voltage (electric signal) having a resonance frequency of the first vibrators 10 and 11 to the upper electrode layer 23 of the drive element 16, the diaphragms 10B and 10D on which the wide drive element 16 is formed. , 11B and 11D cause flexural vibration in the thickness direction. The diaphragms 10A, 10C, 11A, and 11C adjacent to the diaphragms 10B, 10D, 11B, and 11D cause flexural vibrations in the opposite direction due to the principle of resonance. Accordingly, the diaphragms 10A to 10D and 11A to 11D alternately vibrate in opposite phases, and the displacement is accumulated around the central axis S1, as shown in FIG. It can be repeatedly rotated and oscillated. A narrow drive element 16 is formed on the diaphragms 10A, 10C, 11A, and 11C adjacent to the diaphragms 10B, 10D, 11B, and 11D on which the wide drive element 16 is formed. 10C, 11A, and 11C are substantially impressed with a voltage. Therefore, the diaphragms 10B, 10D, 11B, and 11D on which the wide drive element 16 is formed are displaced in opposite phases.

  Similarly, as shown in FIGS. 3 and 4, wide drive elements 16 are formed on every other diaphragm 13 </ b> A to 13 </ b> E and 14 </ b> A to 14 </ b> E of the second vibrators 13 and 14. Therefore, the vibration plates 13A to 13E and 14A to 14E of the second vibrators 13 and 14 are applied to the upper electrode layer 23 of the drive element 16 by applying an AC voltage having the resonance frequency of the second vibrators 13 and 14. It is possible to alternately bend and vibrate in the opposite phase, and the frame body 12 and the mirror part 9 can be largely repetitively rotationally oscillated around the central axis S2.

  Thereby, in this Embodiment, the mirror part 9 can be rotated to a biaxial direction, making the center the fixed point.

  Next, the effect in this Embodiment is demonstrated.

  In the present embodiment, the detection accuracy of the monitor elements 17 and 18 can be increased, and the optical reflection element 8 can be self-excited and driven with high accuracy.

  That is, in the present embodiment, the lower electrode layer 21 of the monitor elements 17 and 18 and the lower electrode layer of the drive element 16 at any point where the monitor elements 17 and 18 and the drive element 16 are arranged adjacently in parallel. 21 is formed such that the shortest conduction path to the electrode 21 is longer than the distance from the lower electrode layer 21 of the monitor elements 17 and 18 to the extraction electrode 29.

  As a result, even if the wiring length of the lower electrode layer 21 of the monitor elements 17 and 18 is increased, the ground resistance of the lower electrode layer 21 of the monitor elements 17 and 18 is reduced to the lower electrode layer 21 of the monitor elements 17 and 18 and the drive element 16. It is possible to relatively lower the conduction resistance between the lower electrode layer 21 and the lower electrode layer 21.

  Therefore, an electric signal input to the upper electrode of the drive element 16 between the monitor element 17 and the upper electrode layers 23 and 24 of the drive element 16 or between the monitor element 18 and the upper electrode layers 23 and 25 of the drive element 16 is driven. The upper electrode layer of the monitor elements 17, 18 through the piezoelectric layer 22 of the element 16, the lower electrode layer 21 of the drive element, the lower electrode layer 21 of the monitor elements 17, 18, and the piezoelectric layer 22 of the monitor elements 17, 18. Leakage to 24 and 25 can be suppressed.

  Furthermore, since etching is performed until the bottom surface of the concave groove 30B is composed of the base material 19, the surface of the dense base material 19 can be exposed, and it becomes difficult for the conductor or the dielectric substance to adhere, and the leak is further increased. Can be reduced.

  As the drive frequency is increased, the impedance due to the capacitance is reduced, and the leakage current that is a problem is increased. Therefore, the structure of this embodiment particularly monitors the first vibrators 10 and 11 that are driven at a high frequency. This is useful for increasing the detection accuracy of the element 17.

  Note that at least at any point where the monitor element 17 and the drive element 16 are arranged adjacent to each other in parallel, the shortest conduction path between the lower electrode layer 21 of the monitor element 17 and the lower electrode layer 21 of the drive element 16 is By forming the monitor element 17 so as to be longer than the distance from the lower electrode layer 21 to the extraction electrode 29, the same effect can be obtained.

  Further, in the present embodiment, in each of the first vibrators 10 and 11 and the second vibrators 13 and 14, the substrate 19 and the monitor are partially etched until the concave groove 30B is formed. The lower electrode layer 21 can be separated almost certainly so that the elements 17 and 18 are not capacitively coupled or conducted by the residue of the lower electrode layer 21. Therefore, even if the wiring distance of the lower electrode layer 21 is long, a leakage current between the upper electrode layers 23 and 24 of the drive element 16 and the monitor element 17 or between the drive element 16 and the upper electrode layers 23 and 25 of the monitor element 18 is reduced. Can be reduced. As a result, the detection accuracy of the monitor elements 17 and 18 can be increased, and the optical reflection element 8 can be self-excited and driven with high accuracy.

  Here, in the optical reflective element 8 that requires a large amplitude, the first vibrators 10 and 11 and the second vibrators 13 and 14 may have a meander shape as in the present embodiment, and the vibration The beam length of the child becomes very long. In this case, since the wiring distance of the lower electrode layer 21 becomes longer, it is considered that the grounding of the lower electrode layer 21 is not sufficient. However, even if the lower electrode layer 21 is not sufficiently grounded, this embodiment that can reduce the leakage current between the monitor elements 17 and 18 and the drive element 16 realizes highly accurate self-excited drive. Useful for.

  Further, since the upper electrode layer 23 of the monitor element 17 of the first vibrators 10 and 11 is also routed on the second vibrators 13 and 14, the wiring distance of the lower electrode layer 21 is further increased. Therefore, the configuration of the present embodiment is very useful for realizing high-precision detection accuracy of the monitor elements 17 of the first vibrators 10 and 11.

  Furthermore, in the present embodiment, the insulating layer 20 is made of silicon dioxide having a low dielectric constant compared to a material used as the piezoelectric layer 22. Therefore, for example, even when a conductor component adheres to the bottom surface of the concave groove 30B at the time of etching processing or the like, leakage due to capacitive coupling can be reduced, and even if a dielectric component adheres, it is difficult to cause noise. As a result, the detection accuracy of the monitor elements 17 and 18 can be improved.

  In the present embodiment, since the upper electrode layer 23 that is the drive electrode of the drive elements 16 of the first vibrators 10 and 11 and the second vibrators 13 and 14 is used in common, the wiring of the electrodes routed on the optical reflective element 8 The number can be reduced, the production efficiency can be increased, and the interference between the electrodes can also be reduced.

  In the present embodiment, the two electric signals are synthesized via the impedance element, but may be synthesized via, for example, a preamplifier, a saturation amplifier, a bandpass filter, and an addition synthesis circuit. In this case, since the circuit is composed of active elements, these can be formed into IC chips, and rationalization in the mounting process can be achieved.

  In addition, the first vibrators 10 and 11 and the second vibrators 13 and 14 respectively use the principle of resonance and the diaphragms 10A to 10D and 11A to 11D and the diaphragms 13A to 13E and 14A with one upper electrode layer. ˜14E can be alternately oscillated in opposite phases to accumulate displacement, so that the number of electrode wires can be reduced while maintaining high driving efficiency.

  In the present embodiment, the bottom surface of the concave groove 30B is formed flat. However, as shown in FIG. 7, the concave groove 30B may be configured to become deeper from the outer periphery toward the center. As a result, the insulation distance between the lower electrode layer 21 of the drive element 16 and the lower electrode layer 21 of the monitor element 17 is increased, and leakage can be reduced. Even if a conductor component or a dielectric component adheres to the concave groove 30B, the actual distance becomes longer than when the bottom surface is flat. Therefore, the upper electrode layers 23 and 24 of the drive element 16 and the monitor elements 17 and 18 are further increased. Leakage between the upper electrode layers 23 and 25 can be reduced.

  Further, as shown in FIG. 8, the same effect can be obtained even when the concave groove 30 </ b> B is configured to become deeper from the center toward the outer periphery.

  In the present embodiment, the shapes of the first vibrators 10 and 11 and the second vibrators 13 and 14 are meander shapes. However, the present invention is not limited to this, and other shapes such as cantilever shapes and cross shapes can also be applied. Is possible. In the present embodiment, the biaxially driven optical reflection element 8 in which the first vibrators 10 and 11 and the second vibrators 13 and 14 are connected to the mirror unit 9 is taken as an example, but uniaxial drive may be used. .

  The optical reflecting element 8 of the present invention is useful for a small image projector such as a small projector, a head-up display, and a head mounted display.

DESCRIPTION OF SYMBOLS 9 Mirror part 10 1st vibrator 10A-10D Diaphragm 11 1st vibrator 11A-11D Diaphragm 12 Frame 13 2nd vibrator 13A-13E Diaphragm 14 2nd vibrator 14A-14E Diaphragm 15 Support body 16 Drive element 17 Monitor element 18 Monitor element 19 Base material 20 Insulating layer 21 Lower electrode layer 22 Piezoelectric layer 23 Upper electrode layer 24 Upper electrode layer 25 Upper electrode layer 26 Lead electrode 27 Lead electrode 28 Lead electrode 29 Lead electrode 30A Dividing groove 30B Groove 31 Amplifier 32 Amplifier 33 Impedance element 34 Impedance element 35 Filter 36 Filter S1 Central axis S2 Central axis

Claims (3)

A mirror unit and a vibrator coupled to the mirror unit;
This oscillator
A drive element and a monitor element respectively disposed on an insulating layer formed by separating a base material and a dividing groove on the base material;
In the base material immediately below the dividing groove between the drive element and the monitor element, a concave groove having a bottom surface is formed,
The bottom surface of the groove is composed of the base material,
These drive elements and monitor elements are each laminated with a lower electrode layer, a piezoelectric layer, and an upper electrode layer.
The lower electrode of the drive element and the monitor element is connected to a common external electrode,
At an arbitrary point where the monitor element and the drive element are disposed adjacent to each other, the shortest conduction path between the lower electrode of the monitor element and the lower electrode of the drive element is lower than the monitor element by the dividing groove. An optical reflecting element that is longer than a distance from an electrode to the common external electrode. The groove is
The optical reflection element according to claim 1, wherein the optical reflection element is formed so as to become deeper from the outer periphery toward the center. The groove is
The optical reflecting element according to claim 1, wherein the optical reflecting element is formed so as to become deeper from the center toward the outer periphery.

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