WO2009081858A1

WO2009081858A1 - Micro scanner and method for controlling micro scanner

Info

Publication number: WO2009081858A1
Application number: PCT/JP2008/073181
Authority: WO
Inventors: Utako Takahashi
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2007-12-20
Filing date: 2008-12-19
Publication date: 2009-07-02

Abstract

A light scanner (LS) includes a fixed frame (FF), a frame axis portion (FA), a movable frame portion (FM), a mirror axis portion (MA), a mirror portion (MR), a holding portion (HD), and a piezoelectric element (PE). When the light scanner (LS) resonates, the frequency of a voltage applied to the piezoelectric element (PE) generates a vibration mode in which a phase of vibration at the time when the movable frame portion (FM) swings relative to the mirror axis portion (MA) and a phase of vibration at the time when the mirror portion (MR) swings relative to the mirror axis portion (MA) are made opposite to each other.

Description

Micro scanner device and control method of micro scanner device

The present invention relates to a micro scanner device equipped with a micro scanner such as an optical scanner, and a control method of the micro scanner device.

Conventionally, various compact optical scanners (micro scanners) using MEMS (Micro Electro Mechanical Systems) technology have been developed. For example, the optical scanner ls of Patent Document 1 as shown in FIG. 12A includes a fixed frame ff, a double-line beam 140 extending inward of the fixed frame ff, a mirror shaft ma connected to the beam 140, and a mirror. The mirror part (variation part) mr clamped by the axial part ma is included. In the optical scanner ls, piezoelectric bodies (drive units) pe1 to pe4 are attached to the beam pieces 141 to 144 in the beam unit 140, thereby forming a unimorph.

In this optical scanner ls, when voltages having different phases are applied to the piezoelectric bodies pe1 and pe2, the piezoelectric bodies pe1 and pe2 bend in opposite directions, and the mirror shaft is caused by the bending. One of the parts ma is twisted. As a result, the mirror part mr swings (rotates) with respect to the mirror shaft part ma.

Furthermore, in this optical scanner ls, the vibrating body 150 including the mirror part mr, the mirror shaft part ma, and the beam part 140 shown in FIG. 12B, which is a partially enlarged view of FIG. 12A, resonates and uses the resonance. The mirror part mr swings at a larger angle.
JP 2005-181477 A

However, as shown in FIG. 12B, in the vibrating body 150 in the optical scanner ls, the phase that the mirror part mr vibrates and the phase that the beam part 140 vibrates are the same (as indicated by arrows 1 and 2). In addition, the mirror part mr and the beam part 140 are displaced in the same direction). The frequency causing such in-phase resonance is usually relatively low. Therefore, the oscillation speed of the mirror part mr depending on this frequency is also relatively slow. Then, a micro-scanner device equipped with such an optical scanner ls, such as a projector, cannot project a high-resolution image.

The present invention has been made in view of the above situation. An object of the present invention is to provide a micro-scanner device having a micro-scanner including a mirror unit that can operate at high speed.

The micro scanner device includes a micro scanner and a drive circuit.

The microscanner is connected to the fixed frame that is an outer frame, the first shaft portion, the movable frame portion that is sandwiched between the first shaft portion and swingable with respect to the first shaft portion, A second shaft portion that intersects the one shaft portion, a variation portion that is held by the second shaft portion, is held in the movable frame portion, and can swing with respect to the second shaft portion, and one end is A holding portion having a cantilever structure connected to one shaft portion and having the other end fixed to a fixed frame; and a driving portion that deforms the holding portion by applying a force generated according to an applied voltage to the holding portion, Including.

The drive circuit includes a vibration phase when the movable frame portion swings with respect to the second shaft portion relative to the drive portion of the micro scanner, and a vibration when the variable portion swings with respect to the second shaft portion. A voltage having a frequency that causes the microscanner to resonate is applied so that the phase of the microscanner is reversed.

In this case, when the microscanner resonates according to the frequency of the applied voltage of the drive unit, for example, the operation of the variable unit and the movable frame unit is regarded as a two-degree-of-freedom non-damped vibration system. Therefore, when the microscanner resonates according to the frequency of the applied voltage, the frequency causing the resonance is the phase of vibration when the movable frame portion swings with respect to the second shaft portion and the fluctuation portion is the second axis. A vibration mode is generated in which the phase of vibration when swinging with respect to the section is opposite to the phase.

In such a vibration mode, the frequency of the applied voltage is usually relatively high (in contrast, in the case of the same phase, the frequency is relatively low). And if a drive part drives with the applied voltage of such a frequency, a holding | maintenance part will deform | transform at high speed, and the movable frame part clamped by the deformation | transformation holding | maintenance part via a 1st axial part will also incline at high speed.

Further, when the variable portion swings with respect to the second shaft portion due to the inclination of the movable frame portion (that is, when the frequency of the applied voltage that causes resonance swings the variable portion with reference to the second shaft portion). , The movement of the variable part becomes faster. Therefore, this micro scanner swings the variable part at high speed.

Further, it is desirable that the frequency of the applied voltage causing resonance causes a vibration mode in which the phase of the movable frame portion vibrates and the phase of the system including the holding portion and the drive portion (for example, unimorph) vibrate.

If this is the case, the displacement between the movable frame portion and the system including the holding portion and the drive portion is relatively small. Therefore, a member located between the movable frame portion and the system including the holding portion and the drive portion, for example, the second shaft portion, is subjected to relatively little stress due to the displacement. Therefore, the second shaft portion and the like are not easily damaged.

When the holding unit and the driving unit are separated from each other, for example, when the driving unit is an electrostatic unit composed of two electrodes, the frequency of the applied voltage that causes resonance vibrates the movable frame unit. It is desirable to generate a vibration mode in which the phase and the phase in which the holding portion vibrates are the same. If it becomes like this, the 2nd axial part etc. which are the members located between a movable frame part and a holding | maintenance part will be hard to damage like the above.

In addition, the method for controlling the micro scanner device as described above is based on the phase of vibration when the movable frame portion swings with reference to the second shaft portion, and when the fluctuation portion swings with reference to the second shaft portion. A voltage having a frequency for causing the microscanner to resonate is applied to the driving unit by the driving circuit so that the phase of the vibration is reversed.

Further, the micro scanner control method generates a vibration mode in which the frequency of the applied voltage causing resonance is the same as the phase of the movable frame and the phase of the system including the holding unit and the drive unit. A frequency is desirable.

Also, the control method of the microscanner is preferably such that the frequency of the applied voltage that causes resonance is a frequency that generates a vibration mode in which the phase of vibration of the movable frame portion and the phase of vibration of the holding portion are in phase.

According to the microscanner apparatus of the present invention, the microscanner resonates due to a relatively high frequency applied voltage to the drive unit, and the fluctuation of the variable part in the microscanner becomes high speed corresponding to the frequency of the applied voltage. .

FIG. 3 is a plan view of the optical scanner. FIG. 2 is a partially enlarged view of the optical scanner shown in FIG. 1. FIG. 1 is a cross-sectional view taken along the line A-A ′ of FIG. FIG. 3 is a cross-sectional view taken along the line B-B ′ of FIG. FIG. 3 is a cross-sectional view taken along the line A-A ′ of FIG. FIG. 3 is a cross-sectional view taken along the line B-B ′ of FIG. FIG. 3 is a model diagram of a non-damped vibration system having two degrees of freedom. These are explanatory drawings showing a primary vibration mode and a secondary vibration mode. These are the perspective views of the optical scanner which show the state which the mirror part and the movable frame part vibrate with the same phase. These are the perspective views of the optical scanner which show the state which the mirror part and the movable frame part are vibrating with a different phase. FIG. 2 is a cross-sectional view taken along the line A-A ′ in FIG. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. FIG. 8 is a perspective view of an optical scanner different from those in FIGS. 6 and 7. These are the top views of the optical scanner which employ | adopted the electromagnetic system. FIG. 3 is a block diagram showing a projector. FIG. 3 is a perspective view of a conventional optical scanner. FIG. 12B is a partially enlarged view of FIG. 12A.

Explanation of symbols

MR mirror part (fluctuating part)
MA mirror shaft (second shaft)
FM Movable frame part FA Frame shaft part (first shaft part)
HD holding unit HD1 first holding unit HD2 second holding unit PE piezoelectric element (drive unit)
TB torsion bar ST slit FF fixed frame LS optical scanner (micro scanner)
10 Projector (micro scanner device)
DESCRIPTION OF SYMBOLS 11 Input image processing part 12 Drive control part 13 Optical scanner drive circuit (drive circuit)
DESCRIPTION OF SYMBOLS 14 Light source drive circuit 15 Optical mechanism part 16 Light source unit 17 Projection optical system

[Embodiment 1]
The following describes one embodiment with reference to the drawings. Here, a mirror part is taken as an example of a member (fluctuating part) that fluctuates, and an optical scanner is taken as an example of a micro scanner that performs a scanning operation by reflecting light by changing the mirror part.

In order to facilitate understanding, even plan views are hatched. In addition, for convenience, member codes and hatching may be omitted. In such a case, other drawings are referred to. Moreover, the black circle on the drawing means a direction perpendicular to the paper surface.

FIG. 1 is a plan view of the optical scanner LS, and FIG. 2 is a partially enlarged view of FIG. As shown in FIG. 1, the optical scanner LS includes a mirror part MR, a mirror shaft part MA, a movable frame part FM, a frame shaft part FA, a holding part HD, a piezoelectric element PE, a torsion bar TB, and a fixed frame FF. These members are formed by etching a deformable silicon substrate or the like that becomes the base BS.

Mirror portion (variable portion, reflecting portion) MR reflects light from a light source or the like, and is formed by attaching a reflective film such as gold or aluminum to a part of the base BS. For example, as shown in FIG. 1, the opening H (the first opening H1 and the second opening H2) including a semicircular constricted portion and a sandwiching portion that sandwiches the semicircular constricted portion from both ends face each other. Thus, the remainder of the base BS including a circle is generated. And the mirror part MR is completed by affixing a reflecting film on a part of this remaining part.

The direction in which the first opening H1 and the second opening H2 are arranged is referred to as the X direction, the X direction on the second opening H2 side is the plus X of the X direction {X (+)}, and the direction opposite to the + direction. Is minus X in the X direction {X (−)}. Further, a direction extending in the X direction from the center of the mirror part MR is referred to as an X axis.

The mirror shaft portion (second shaft portion) MA is an axis generated so as to be connected to one end and the other end of the mirror portion MR when the sandwiching portion of the first opening H1 and the sandwiching portion of the second opening H2 face each other. It is a shaped part. One of the mirror shaft portions MA connected to one end of the mirror portion MR (first mirror shaft portion MA1) and the other of the mirror shaft portions MA connected to the other end of the mirror portion MR (second mirror shaft portion MA2) are: The mirror portion MR extends in different directions (however, the first mirror shaft portion MA1 and the second mirror shaft portion MA2 are parallel).

Further, the extending direction of the mirror shaft part MA is orthogonal to (crosses) the X direction. Therefore, the direction in which the mirror shaft portion MA extends is referred to as the Y direction, the Y direction on the first mirror shaft portion MA1 side is plus Y direction (Y (+)), and the opposite direction to the + direction is minus direction in the Y direction. Let {Y (-)}. Further, a direction extending in the Y direction from the center of the mirror part MR is referred to as a Y axis.

Further, the direction orthogonal to the X direction and the Y direction is defined as the Z direction (deflection direction). The direction is minus Z direction (Z (−)). Furthermore, the direction extending in the Z direction from the intersection of the X axis and the Y axis is referred to as the Z axis.

The movable frame portion FM is a frame surrounding the mirror portion MR and the mirror shaft portion MA. For example, of the two openings H in a bracket shape (] shape), the third opening H3 that is one opening H is formed so as to surround the first mirror shaft portion MA1, and is the other opening H. When the fourth aperture H4 is formed so as to surround the second mirror shaft portion MA2, the remaining portion of the base BS sandwiched between the third aperture H3 and the first aperture H1 and the second aperture H2, The remaining part of the base BS sandwiched between the four openings H4 and the first openings H1 and the second openings H2 is generated. Then, both remaining parts become a part of the frame-shaped base body BS surrounding the mirror part MR and the mirror shaft part MA, that is, the movable frame part FM.

The frame shaft portion (first shaft portion) FA extends outward from one end and the other end that overlap and face the X axis at the outer edge of the movable frame portion FM, thereby sandwiching the movable frame portion FM. For example, when the third opening H3 and the fourth opening H4 in a bracket shape face each other and both ends of the third opening H3 and both ends of the fourth opening H4 face each other, a part of the base BS sandwiched between the both ends becomes a rod shape The rod-shaped part becomes the frame shaft part FA. In the following, one of the frame shaft portions FA extending toward the X (−) side is referred to as a first frame shaft portion FA1, and the other of the frame shaft portions extending toward the X (+) side is referred to as a second frame shaft portion FA2. To do.

The holding portion HD holds the movable frame portion FM by holding the frame shaft portion FA (connected to the frame shaft portion FA). The holding portion HD is formed by the remaining portion of the base BS generated between the opening H (the fifth opening H5 and the sixth opening H6) extending in the Y direction and the third opening H3 and the fourth opening H4. Is done.

More specifically, the fifth opening H5 and the sixth opening H6 are arranged along the X direction and sandwich the third opening H3 and the fourth opening H4. Then, the remaining portion of the base BS extending in the Y direction located between the fifth opening H5 and the third opening H3 / fourth opening H4 becomes the first holding portion HD1, and the sixth opening H6 and the third opening are formed. The remaining portion of the base body BS extending in the Y direction located between the hole H3 and the fourth opening H4 becomes the second holding part HD2. In addition, the holding part HD having such a shape (linear shape) extending in the Y direction is easily bent.

The piezoelectric elements PE (PEa to PEd) are elements that convert voltage into force. The piezoelectric body PB (PBa to PBd) subjected to the polarization process and the electrodes EE1 and EE2 (EE1a to EE1d EE2a to EE2d) (see FIGS. 3 and 8 to be described later). The piezoelectric element (driving unit) PE is affixed on the surface of the holding unit HD to form a unimorph unit (actuator) YM. More specifically, the unimorph part YM (YMa to YMd) is formed by bonding one electrode (first electrode) EE1 of the piezoelectric element PE and one surface of the holding part HD.

Then, a ± voltage (AC voltage) is applied between the first electrode EE1 and the second electrode EE2 within a range that does not cause polarization reversal, so that the piezoelectric body PB expands and contracts, and the unimorph portion according to the expansion and contraction YM bends.

The piezoelectric elements PEa and PEb are attached to the first holding portion HD1 so as to sandwich the first frame shaft portion FA1, and the piezoelectric elements PEc and PEd are sandwiched between the second frame shaft portion FA2. The second holding part HD2 is attached. Therefore, the holding portion HD is also deformed (flexible deformation / bending deformation) in accordance with the expansion and contraction of the piezoelectric bodies PB (PBa to PBd) in the piezoelectric elements PEa and PEb and the piezoelectric elements PEc and PEd.

In the following, one piece of the first holding portion HD1 to which the piezoelectric element PEa is attached is referred to as a holding piece HD1a, and one piece of the first holding portion HD1 to which the piezoelectric element PEb is attached is referred to as a holding piece HD1b. A piece of the second holding portion HD2 attached is referred to as a holding piece HD2c, and a piece of the second holding portion HD2 attached with the piezoelectric element PEd is referred to as a holding piece HD2d.

The torsion bar TB is a member that changes the deformation (bending deformation, etc.) of the holding portion HD into a torsional deformation (rotational torque) and transmits it to the frame shaft portion FA (see the dotted line portions in FIGS. 1 and 2). Such a torsion bar TB is formed in the holding portion HD.

For example, as shown in FIG. 2, the first slits ST1 and ST1 extending in the X direction from the ends of the third opening H3 and the fourth opening H4, and the same direction as the first slits ST1 and ST1 (X A portion of the base body BS located between the second slits ST2 and ST2 extending in the direction (Y direction) and juxtaposed along the Y direction becomes the torsion bar TB.

The third slit ST3 connected to the fifth hole H5, more specifically, between the second slit ST2 and the third slit ST3 extending in the X direction and aligned with the first slit ST1 along the X direction. A part of the base body BS located becomes a torsion bar TB.

Note that the presence of the torsion bar TB generated by the slit ST in the holding portion HD causes a gap in the holding portion HD. Therefore, the strength of the holding portion HD decreases due to the presence of this gap. As a result, the holding portion HD is easily bent.

In particular, these torsion bars TB extend in a direction (for example, X direction) intersecting the extending direction (Y direction) of the holding portion HD. In this case, the torsion bar TB is easily twisted when the holding portion HD is bent.

A portion BS1 of the base BS positioned between the first slits ST1 and ST1 is connected to the frame shaft portion FA, and a portion BS3 of the base BS positioned between the third slits ST3 and ST3 is connected to the frame shaft portion FA. Line up along the axial direction. Therefore, these two parts BS1 · BS3, may be referred to as a frame shaft portion FA including a portion BS _M of the substrate BS located between the two parts BS1 · BS3. Further, a part of the base body BS positioned between the portion BSM and the second slit ST2 connects the torsion bar TB and the frame shaft portion MA. Therefore, this portion is referred to as a coupling portion CB.

The fixed frame FF is an outer frame of the optical scanner LS. That is, the fixed frame FF is a frame-like member that surrounds the mirror part MR, the mirror axis MA, the movable frame part FM, the frame axis part FA, the holding part HD, the piezoelectric element PE, and the torsion bar TB.

Here, the deflection operation of the mirror part MR in the above optical scanner LS will be described with reference to FIG. 1 and FIGS. 3A to 3D. 3A and 3C are cross-sectional views taken along line A-A 'in FIG. 1, and FIGS. 3B and 3D are cross-sectional views taken along line B-B' in FIG.

1 oscillates (rotates) the mirror portion MR with reference to the mirror shaft portion MA (Y-axis). Therefore, one direction around the axis of the mirror shaft portion MA {clockwise rotation from Y (+) to Y (-)} is forward rotation P, and rotation in the opposite direction to the normal rotation (counterclockwise rotation). 3A and 3B show the deformation of the first holding part HD1 and the second holding part HD2 when the mirror part MR rotates forward, and FIGS. 3C and 3D show the mirror part MR reversely rotating. The deformation | transformation of 1st holding | maintenance part HD1 and 2nd holding | maintenance part HD2 in the case of doing is shown.

When the mirror part MR rotates forward with respect to the mirror shaft part MA, as shown in FIG. 3A, a voltage for extending the piezoelectric bodies PBa and PBb in the piezoelectric elements PEa and PEb is applied to the first holding part HD1. When such a voltage is applied, the holding piece HD1a of the first holding portion HD1 to which the first electrode EE1a is attached and the first electrode EE1b to which the first electrode EE1b is attached are attached by the extending piezoelectric bodies PBa and PBb. Both the holding piece HD1b of the holding portion HD1 bends with the Z (+) side protruding. As a result, the first frame shaft portion FA1 side of the holding piece HD1a and the holding piece HD1b hangs down to Z (−), and the first frame shaft portion FA1 is also displaced toward Z (−).

On the other hand, as shown in FIG. 3B, in the second holding unit HD2, a voltage for contracting the piezoelectric bodies PBc and PBd in the piezoelectric elements PEc and PEd is applied. When such a voltage is applied, the holding piece HD2c of the second holding portion HD2 to which the first electrode EE1c is attached and the second electrode to which the first electrode EE1d is attached are contracted by the contracting piezoelectric bodies PBc and PBd. Both the holding piece HD2d of the holding portion HD2 bends with the Z (−) side convex. As a result, the second frame shaft portion FA2 side of the holding piece HD2c and the holding piece HD2d jumps up to Z (+), and the second frame shaft portion FA2 is also displaced toward Z (+).

As described above, when the first holding portion HD1 displaces the first frame shaft portion FA1 toward Z (−) and the second holding portion HD2 displaces the second frame shaft portion FA2 toward Z (+). The movable frame FM sandwiched between the first frame shaft portion FA1 and the second frame shaft portion FA2 is inclined. When the movable frame FM is tilted in this way, the mirror portion MR included in the movable frame FM is also tilted with respect to the mirror shaft portion MA. This inclination is an inclination generated by the displacement of the first frame axis part FA1 and the second frame axis part FA2 that are separated from the mirror axis part MA at substantially equal intervals. Therefore, considering the mirror shaft portion MA as a reference, the mirror portion MR rotates forward with respect to the mirror shaft portion MA.

Next, when the mirror part MR rotates in reverse with respect to the mirror shaft part MA, as shown in FIG. 3C, a voltage for contracting the piezoelectric bodies PBa and PBb of the piezoelectric elements PEa and PEb is applied. When such a voltage is applied, the contracting piezoelectric bodies PBa and PBb cause the holding piece HD1a and the holding piece HD1b in the first holding portion HD1 to bend with the Z (−) side convex. As a result, the first frame shaft portion FA1 side of the holding piece HD1a and the holding piece HD1b jumps up to Z (+), and the first frame shaft portion FA1 is also displaced toward Z (+).

On the other hand, as shown in FIG. 3D, a voltage for extending the piezoelectric bodies PBc and PBd of the piezoelectric elements PEc and PEd is applied. When such a voltage is applied, the holding pieces HD2c and the holding pieces HD2d in the second holding portion HD2 bend with the Z (+) side projecting by the extending piezoelectric bodies PBc and PBd. As a result, the second frame shaft portion FA2 side of the holding piece HD2c and the holding piece HD2d hangs down to Z (−), and the second frame shaft portion FA2 is also displaced toward Z (−).

As described above, when the first holding portion HD1 displaces the first frame shaft portion FA1 toward Z (+) and the second holding portion HD2 displaces the second frame shaft portion FA2 toward Z (−). Similarly to the forward rotation, the movable frame portion FM is inclined, and as a result, the mirror portion MR rotates reversely with respect to the mirror shaft portion MA.

However, the rotation angle θ (deflection angle θ) of forward / reverse rotation of the mirror MR with respect to the mirror shaft MA that is the Y axis as described above is relatively small. Therefore, in the optical scanner LS, the frequency of the voltage applied to the piezoelectric elements PE (PEa to PEd) used to tilt the movable frame FM is close to the resonance frequency of the rotational vibration of the mirror MR with respect to the mirror shaft MA. It becomes the frequency of. This is because, even if the tilt amount of the movable frame FM is relatively small, the mirror MR resonates with the frequency of the voltage applied to the piezoelectric element PE and swings relatively large.

Note that the resonance frequency of the optical scanner LS can be obtained as long as the Young's modulus, Poisson's ratio, density in the base BS, the shape of the mirror part MR, the fixing conditions, the piezoelectric constant of the piezoelectric element PE, etc. are known. It can be calculated by simulation software.

Here, the frequency of the voltage applied to the piezoelectric element PE that also causes the optical scanner LS to resonate will be described. In particular, the vibration mode at resonance will be described. In this description, the unimorph part YM, the torsion bar TB, the first frame shaft part FA1, the movable frame part FM, the first mirror shaft part MA1, the mirror part MR, and the second mirror shaft part MA2 in the optical scanner LS are shown in FIG. A vibration mode of the mirror part MR and the movable frame part FM will be described by comparing with a model system as shown in FIG.

The first wall WL1, the first spring SPG1, the first weight OM1, the second spring SPG2, the second weight OM2, the third spring SPG3, the second wall WL2 and the unimorph portion in the optical scanner LS in the model system of FIG. The relationship among YM, torsion bar TB, first frame shaft portion FA1, movable frame portion FM, first mirror shaft portion MA1, mirror portion MR, and second mirror shaft portion MA2 is as follows.
1st wall WL1 = Unimorph part YM,
1st spring SPG1 = torsion bar TB and 1st frame axial part FA1
1st weight OM1 = movable frame part FM
Second spring SPG2 = first mirror shaft portion MA1
2nd weight OM2 = mirror part MR
Third spring SPG3 = second mirror shaft part MA2
2nd wall WL2 = movable frame part FM
For convenience, the second frame shaft portion FA2, the torsion bar TB and the unimorph portion YM close to the second frame shaft portion are omitted. However, in the case of modeling, it is preferable to include the second frame shaft portion FA2 in the second wall WL2.

Before that, first, assuming that the mass m of the weight, the spring constant k, and the moving distance x of the weight, the equation of motion of the two-degree-of-freedom non-damped vibration system is expressed by the following equations (1) and (2). Note that the number of dots above the head of the variable means the rank of time differentiation.

Here, the spring constant is replaced as shown in equations (3) to (5).

And if a periodic motion is assumed, a solution can be put like the following formula (6). Note that x is displacement, u is amplitude, ω is angular frequency, t is time, and φ is initial phase.

If this equation (6) is substituted into equations (1) and (2), the following equations (7) and (8) are obtained.

In order to have an effective solution, the coefficient determinant needs to be “0”. Therefore, the following equation (9) is used.

Then, by solving the equation (9), the natural angular frequency ω ₁ and the natural angular frequency ω ₂ are obtained {see formula (10)}.

The natural angular frequency ω ₁ and the natural angular frequency ω ₂ satisfy the relationship “ω ₁ <ω ₂ ”. The natural angular frequency ω ₁ is called a primary natural frequency, and the natural angular frequency ω ₂ is called a secondary natural frequency.

Next, an eigenvector is obtained. When the natural angular frequency ω ₁ and the natural angular frequency ω ₂ are determined, the ratio between u ₁ and u ₂ is determined from the above equations (7) and (8). When this ratio is r _i (i = 1, 2; i means the first order and second order), the following expressions (11) and (12) are obtained, and r ₁ and r ₂ Is determined as a function of the coefficients.

The eigenmode is an expression of the amplitude ratio at the time of harmonic vibration in a vector format, and can be expressed by the following equations (13) and (14).

The following matrix (15) in equation (13) and the following matrix (16) in equation (14) are the eigenvectors of the natural angular frequency ω ₁ and the natural angular frequency ω ₂ .

Based on the above, the spring constants k ₁ and k ₂ in the model system of FIG. 4 are k (k ₁ = k ₂ = k), the mass m ₁ of the first weight OM1 is m (m ₁ = m), If the mass m ₁ of the two weights OM2 is 2 m (m ₂ = m) and the natural frequency and the natural mode are to be obtained, the equations of motion are as shown in the following equations (17) and (18).

Here, matrix expression is made using the following equation (19).

Then, the following equation (20) is obtained.

Here, the following equation (21) is substituted into equation (20).

Then, the following equation (22) is obtained.

Then, when the natural vibration equation is obtained from this equation (22), the following equation (23) is obtained, and the equation (23) is solved.

Then, the natural angular frequency ω ₁ and the natural angular frequency ω ₂ are expressed by the following equations (24) and (25).

Thus, when the ratio r ₁ and the ratio r ₂ are obtained, the following expressions (26) and (27) are obtained.

Therefore, the natural vector of the natural angular frequency ω ₁ and the natural vector of the natural angular frequency ω ₂ are as shown in the following matrix (28) and matrix (29).

FIG. 5 shows a vibration mode (primary vibration mode) based on the natural angular frequency ω ₁ and a vibration mode (secondary vibration mode) based on the natural angular frequency ω ₂ from the obtained eigenvector. Shown in The natural angular frequency ω ₂ is higher than the natural angular frequency ω ₁ (ω ₂ > ω ₁ ). In addition, the tip of the arrow in FIG. 5 shows the position of the weight OM1 and the weight OM2 in each vibration mode, and the numerical value means an eigenvector.

Considering these, assuming that the mirror part MR corresponds to the second weight OM2 and the movable frame part FM corresponds to the first weight OM1, the phase of vibration of the mirror part MR and the phase of vibration of the movable frame part FM are opposite in phase. The natural angular frequency ω ₂ that causes the vibration mode to be generated is greater than the natural angular frequency ω ₁ that generates the vibration mode in which the phase of the vibration of the mirror portion MR and the phase of the vibration of the movable frame portion FM are the same. It becomes clear that it becomes a high frequency.

Further, for verification, the optical scanner LS shown in FIG 1, the natural frequency corresponding to ₂ natural frequency (or resonance frequency) 4.8 kHz, natural angular frequency ω corresponding to the natural angular frequency .omega.1 29. The mirror part MR and the movable frame part FM were made to resonate at 4 KHz. Then, if the natural angular frequency omega _1, as shown in the perspective view of FIG. 6, the mirror MR and the movable frame section FM becomes clear that vibrates in the same direction, the natural angular frequency omega ₂ In this case, as shown in the perspective view of FIG. 7, it became clear that the mirror part MR and the movable frame part FM vibrate in different directions.

More specifically, a part of the mirror part MR and a part of the movable frame part FM adjacent to the first opening H1 (a part of the mirror part MR adjacent to the second opening H2 and a part of the movable frame part FM). It has become clear that they vibrate in the same direction or in different directions.

In addition, the rotation angle of the mirror MR is ± 1.7 ° in resonance at the natural angular frequency ω ₁ in proportion to the natural frequency, and the resonance of the mirror MR in resonance at the natural angular frequency ω ₂ . The deflection angle was ± 4.1 °. Note that the rotation angle θ is an angle generated between the mirror portion MR that is in an immobile state without being affected by the unimorph portion YM and the mirror portion MR that fluctuates.

To summarize the above, an optical scanner LS that can support a model system as shown in FIG. 4, for example, a fixed frame FF, a frame shaft part FA, a movable frame part FM, a mirror shaft part MA, a mirror part MR, a holding part HD, And an optical scanner LS including the piezoelectric element PE (that is, the unimorph part YM including the holding part HD and the piezoelectric element PE).

This is because when such an optical scanner LS resonates according to the frequency of the voltage applied to the piezoelectric element PE, the phase of vibration when the movable frame portion FM swings with respect to the mirror shaft portion MA, and the mirror portion MR This is because a vibration mode in which the phase of the vibration when swinging with respect to the mirror shaft MA is an opposite phase always occurs, and the frequency causing the vibration mode is extremely high. With such a high frequency, the mirror part MR realizes an extremely high-speed scanning operation.

[Embodiment 2]
A second embodiment will be described. In addition, about the member which has the same function as the member used in Embodiment 1, the same code | symbol is attached and the description is abbreviate | omitted.

In the optical scanner LS in the first embodiment, the mirror portion MR is swung with respect to the mirror shaft portion MA. However, the present invention is not limited to this, and the optical scanner LS can also swing the mirror part MR with respect to the frame shaft part FA. That is, the optical scanner LS shown in FIG. 1 can be a one-dimensional optical scanner or a two-dimensional optical scanner.

Therefore, in the second embodiment, the optical scanner LS of FIG. 1 will be described as a two-dimensional optical scanner. However, since the swing of the mirror part MR with respect to the mirror axis MA is the same as that described in the first embodiment, it will be omitted, and the swing of the mirror part MR with respect to the frame shaft part FA will be described.

It should be noted that one direction around the axis of the frame shaft part FA {clockwise rotation from X (+) to X (-)} is forward rotation P, rotation in the opposite direction to the normal rotation (counterclockwise rotation). ) Is the reverse rotation R, FIG. 8A shows the deformation of the first holding unit HD1 when forwardly rotating, and FIG. 8B shows the deformation of the first holding unit HD1 when the mirror MR is reversely rotated (note that FIG. 8A and FIG. 8B are cross-sectional views taken along line AA ′ in FIG.

Hereinafter, only the first holding unit HD1 which is one of the two holding units HD will be described, but when the one first holding unit HD1 attempts to rotate the mirror unit MR forward or backward, The remaining second holding portion HD2 is similarly modified, and the mirror portion MR is rotated forward or backward.

As shown in FIG. 8A, when the mirror portion MR rotates forward with respect to the frame shaft portion FA, a voltage for extending the piezoelectric body PBa is applied and a voltage for contracting the piezoelectric body PBb (applied to the piezoelectric body PBa). Applied).

When such a voltage is applied, the piezoelectric body PBa extends, so that the holding piece HD1a of the first holding portion HD1 to which the first electrode EE1a is attached is bent with the Z (+) side convex. As a result, the first frame shaft portion FA1 side of the holding piece HD1a hangs down to Z (−). On the other hand, when the piezoelectric body PBb contracts, the holding piece HD1b of the first holding portion HD1 to which the first electrode EE1b is attached is bent with the Z (−) side convex. As a result, the first frame shaft portion FA1 side of the holding piece HD1b jumps up to Z (+).

When such bending of the holding piece HD1a and the holding piece HD1b occurs, the Y (+) side of the first frame shaft portion FA1 is pushed down via the torsion bar TB (TBa) and also via the torsion bar TB (TBb). The Y (−) side of the first frame shaft portion FA1 is pushed up. In such a case, the torsion bars TBa and TBb are simply twisted with reference to their own axial directions (bar axis directions), and the first frame shaft portion FA1 is displaced. As a result, the mirror part MR rotates forward with respect to the frame shaft part FA.

On the other hand, when the mirror part MR rotates in the reverse direction, as shown in FIG. 8B, a voltage for contracting the piezoelectric body PBa and a voltage for extending the piezoelectric body PBb are applied.

When such a voltage is applied, the piezoelectric body PBa contracts, so that the holding piece HD1a attached with the first electrode EE1a bends with the Z (−) side convex. As a result, the first frame shaft portion FA1 side of the holding piece HD1a jumps up to Z (+). On the other hand, when the piezoelectric body PBb extends, the holding piece HD1b to which the first electrode EE1b is attached is bent with the Z (+) side convex. As a result, the first frame shaft portion FA1 side of the holding piece HD1b hangs down to Z (−).

When such bending of the holding pieces HD1a and HD1b occurs, the Y (+) side of the first frame shaft portion FA1 is pushed up via the torsion bar TBa, and the Y of the first frame shaft portion FA1 is pushed through the torsion bar TBb. The (−) side is pushed down, and the first frame shaft portion FA1 is displaced in reverse to the displacement in the case of forward rotation. Therefore, the mirror part MR rotates reversely with respect to the frame shaft part FA.

As described above, the mirror portion MR is swung (forward rotation / reverse rotation) and the torsional deformation of the torsion bar TB that easily swings the frame shaft portion FA and the holding pieces HD1a and HD1b (that is, the holding portion HD) Bending is used. Therefore, the swing amount of the frame shaft portion FA (forward rotation angle θ or reverse rotation angle θ) is larger than the swing amount when the frame shaft portion FA is swung only by the bending of the holding portion HD. (In other words, the amount of rocking of the frame shaft FA can be efficiently secured).

[Embodiment 3]
A third embodiment will be described. Note that members having the same functions as those used in Embodiments 1 and 2 are denoted by the same reference numerals, and description thereof is omitted.

In the first embodiment, the frequency of the voltage applied to the piezoelectric element PE matches the natural frequency of the optical scanner LS, and the mirror MR and the movable frame FM vibrate in different phases or the same phase. explained. By the way, there are many natural frequencies of such an optical scanner LS. When the optical scanner LS resonates, another member different from the mirror part MR and the movable frame FM also vibrates.

Therefore, attention is paid to the vibration phase of the movable frame portion FM and the vibration phase of the holding portion HD (and hence the unimorph YM). As shown in FIG. 1, the movable frame portion FM and the unimorph YM are connected via a frame shaft portion FA. Therefore, it is inconvenient that a large displacement occurs between the movable frame portion FM and the unimorph YM due to the swing of the mirror portion MR. This is because a stress corresponding to a large displacement is applied between the movable frame portion FM and the unimorph YM, and the frame shaft portion FA, the torsion bar TB, and the like may be damaged.

That is, the frequency applied to the piezoelectric element PE causes the mirror MR and the movable frame FM to vibrate in different directions, and further causes the movable frame FM and the unimorph YM to vibrate in different directions. As shown in FIG. 9, excessive stress is applied to the frame shaft part FA, the torsion bar TB, etc., and they may be damaged.

Therefore, as shown in FIG. 7, a vibration mode is generated in which the movable frame FM and the unimorph YM are vibrated in the same direction while vibrating the mirror portion MR and the movable frame portion FM in different directions. Specifically, the frequency of the voltage applied to the piezoelectric element PE matches or approximates the natural frequency of the optical scanner LS that causes such a vibration mode.

In this case, a part of the movable frame FM adjacent to the first frame shaft part FA1 and a part of the unimorph YM (a part of the movable frame FM adjacent to the second frame shaft part FA2) A part of the unimorph YM vibrates in the same direction as shown in Fig. 7. Then, as is clear from the comparison between Fig. 7 and Fig. 9, the stress is generated between the movable frame portion FM and the unimorph YM. The frame shaft FA and the torsion bar TB are not damaged.

In such a vibration mode, although the movable frame FM and the unimorph YM vibrate in the same direction, the mirror part MR and the movable frame part FM vibrate in different directions. As described above, the mirror part MR performs an extremely high-speed scanning operation.

[Other embodiments]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the second embodiment, an example is given in which the mirror MR swings with reference to the frame shaft FA without using the resonance of the optical scanner LS. However, the present invention is not limited to this, and the mirror portion MR may swing with respect to the frame shaft portion FA using the resonance of the optical scanner LS.

Further, the member (drive unit) for deforming the holding unit HD is not limited to the piezoelectric element PE. For example, as shown in FIG. 10, an electromagnetic unit 33 including an electromagnetic coil 31 and a permanent magnet 32 may be a drive unit (or an electromagnetic drive unit). In such an electromagnetic unit 33, the electromagnetic coil 31 is positioned on one surface (front surface) of the holding portion HD, and the permanent magnet 32 is positioned on the back side of the holding portion HD (separated from the back surface of the holding portion HD). The holding portion HD is bent by an electromagnetic force generated by the coil 31 and the permanent magnet 32.

Also, the piezoelectric drive unit is not limited to a unimorph but may be a bimorph. In addition, the electrostatic unit including two electrodes may be a driving unit (an electrostatic driving unit may be used). In such an electrostatic unit, one electrode is positioned on the back surface of the holding unit HD, and the other electrode is positioned away from the back surface of the holding unit HD (on the back side of the holding unit HD). The holding portion HD is bent by an electrostatic force. In short, as long as the driving unit can deform the holding unit HD, any of an electromagnetic method, an electrostatic method, a piezoelectric method, and the like may be used.

For example, in the case of an electrostatic drive unit, a vibration mode is generated in which the movable frame FM and the holding unit HD are vibrated in the same direction while vibrating the mirror unit MR and the movable frame unit FM in different directions. Like that. Specifically, the frequency of the voltage applied to the electrode is made to match or approximate the natural frequency of the optical scanner LS that causes such a vibration mode.

If this is the case, as in the third embodiment, stress is less likely to be applied between the movable frame portion FM and the holding portion HD, and the frame shaft portion FA and the torsion bar TB are not damaged.

By the way, various micro scanner devices (optical devices) on which the optical scanner LS described above is mounted are assumed (including a drive circuit for applying a voltage to the piezoelectric element PE. ) For example, a projector (image projection apparatus) as shown in the block diagram of FIG.

The projector 10 shown in FIG. 11 includes an input image processing unit 11, a drive control unit 12, and an optical mechanism unit 15.

The input image processing unit 11 receives an image signal (NTSC signal or the like) transmitted from a personal computer (PC) or the like. The input image processing unit 11 performs correction processing (γ correction, image distortion correction, etc.) as appropriate on the received image signal, and transmits the corrected image signal to the drive control unit 12.

The drive control unit 12 is composed of a dedicated electronic circuit, and includes an optical scanner drive circuit (drive circuit) 13 and a light source drive circuit 14.

The optical scanner driving circuit 13 generates a control signal for controlling the driving timing of the optical scanner LS in correspondence with the vertical synchronizing signal and horizontal synchronizing signal of the transmitted image signal. Then, the optical scanner drive circuit 13 transmits a drive signal having a potential corresponding to the control signal to the optical scanner LS included in the optical mechanism unit 15.

Note that the optical scanner drive circuit 13 has a phase of vibration when the movable frame portion FM swings with respect to the mirror shaft portion MA with respect to the piezoelectric element PE of the optical scanner LS, and the mirror portion MR is the mirror shaft portion MA. A voltage having a frequency for causing the optical scanner LS to resonate is applied so that the phase of vibration when oscillating with respect to is reversed.

The light source drive circuit 14 controls light emission of a light source unit 16 (described in detail, a light emitting element included in the light source unit 16) included in the optical mechanism unit 15. More specifically, the light source driving circuit 14 causes the light source 16 to emit light having a color and luminance corresponding to the gradation of the transmitted image signal. The timing at which the light source 16 is illuminated corresponds to the vertical synchronization signal and horizontal synchronization signal of the image signal.

The optical mechanism unit 15 includes a light source unit 16, an optical scanner LS, and a projection optical system 17, and projects light onto a screen SC (projection surface).

The light source unit 16 includes, for example, a light emitting element group in which light emitting elements such as lasers are gathered, and a collimator lens group in which collimator lenses that make the light from the light emitting elements a substantially parallel light flux. The light emitting element group includes a red light emitting element, a green light emitting element, and a blue light emitting element, and the collimator lens group includes three collimator lenses corresponding to the light emitting elements of each color. Each light emitting element generates and emits laser light having a luminance corresponding to the pixel value of the pixel signal from the light source driving circuit 14.

The optical scanner LS is the optical scanner LS itself described above. In brief, the optical scanner LS has a mirror part MR that reflects light traveling from the light source unit 16, and the mirror part MR has two axes that are substantially orthogonal (mirror axis part MA and frame axis part FA). ), The light is reflected two-dimensionally and deflected (scanned).

The projection optical system 17 appropriately guides the light deflected by the optical scanner LS onto the screen SC that is the projection surface, and projects a moving image on the screen SC. In FIG. 11, light (laser light) from the light source unit 16 through the optical scanner LS and further through the projection optical system 17 to the screen SC is indicated by a dotted arrow.

An example of a micro scanner device other than the projector 10 as shown in FIG. 11 is an image forming apparatus such as a copier or a printer. With such a micro scanner device, high-speed scanning and high-resolution image provision can be realized.

In addition, examples of micro scanners other than the optical scanner include those equipped with a lens (bending optical system) instead of the mirror part MR, and those equipped with a light source (light emitting element).

Claims

In a micro scanner device including a micro scanner and a drive circuit,
The micro scanner is
A fixed frame as an outer frame;
A first shaft portion;
A movable frame portion sandwiched between the first shaft portions and swingable with reference to the first shaft portion;
A second shaft portion connected to the movable frame portion and intersecting the first shaft portion;
By being clamped by the second shaft portion, the variation portion is held in the movable frame portion and swingable with respect to the second shaft portion;
A cantilever structure holding portion having one end connected to the first shaft portion and the other end fixed to a fixed frame;
A driving unit that deforms the holding unit by applying a force generated according to an applied voltage to the holding unit;
Including
The drive circuit is oscillated with respect to the drive unit with respect to the phase of vibration when the movable frame unit swings with respect to the second shaft portion, and the variable portion swings with reference to the second shaft portion. Applying a voltage having a frequency that causes the microscanner to resonate so that the phase of the vibration is in an opposite phase.
Micro scanner device.
The frequency of the applied voltage that causes the resonance causes a vibration mode in which a phase in which the movable frame portion vibrates and a phase in which a system including the holding portion and the driving portion vibrates are in phase. Micro scanner device.
2. The micro scanner device according to claim 1, wherein the frequency of the applied voltage causing the resonance generates a vibration mode in which a phase in which the movable frame portion vibrates and a phase in which the holding portion vibrates are in phase.
In a control method of a micro scanner device including a micro scanner and a drive circuit,
The micro scanner is
A fixed frame as an outer frame;
A first shaft portion;
A movable frame portion sandwiched between the first shaft portions and swingable with reference to the first shaft portions;
A second shaft portion connected to the movable frame portion and intersecting the first shaft portion;
While being held by the second shaft portion, it is held in the movable frame portion,
A variable portion swingable with respect to the second shaft portion;
A cantilever structure holding portion having one end connected to the first shaft portion and the other end fixed to a fixed frame;
A driving unit that deforms the holding unit by applying a force generated according to an applied voltage to the holding unit;
Including
The microscanner so that the phase of vibration when swinging with respect to the second shaft portion and the phase of vibration when swinging with respect to the second shaft portion are reversed from each other. A method for controlling a micro scanner device, wherein a voltage having a frequency for resonating is applied to the drive unit by the drive circuit.
The frequency of the applied voltage that causes the resonance is set to a frequency that generates a vibration mode in which the phase in which the movable frame portion vibrates and the phase in which the system including the holding unit and the drive unit vibrate are in phase. 5. A method for controlling the micro scanner device according to 4.
5. The micro scanner device according to claim 4, wherein the frequency of the applied voltage that causes the resonance is set to a frequency that generates a vibration mode in which a phase in which the movable frame portion vibrates and a phase in which the holding portion vibrates are in phase. Control method.