JP2008182304A - Harmonic oscillation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a harmonic oscillation for suitably adjust oscillation frequency in a resonance frequency range associated with mechanical resonance. <P>SOLUTION: A driving circuit (harmonic resonance circuit) for driving an optical scanner at its resonance frequency turns on/off a switch in one period associated with an oscillation voltage Va to switch a resonance circuit portion between a connection state (oscillation frequency fomL) wherein a predetermined capacitor is connected and a nonconnection state (oscillation frequency fomH). Consequently, a voltage waveform in a period Tb is changed from a waveform of oscillation frequency fomH to a waveform of oscillation frequency fomL, so that a voltage waveform Ka (broken line) changes to a voltage waveform Kb (solid line) to extend the period of an oscillation voltage Va from a period Th to a period Thr. Here, the oscillation frequency can be suitably adjusted in the driving circuit by varying a period Tb. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a harmonic oscillation device that generates an oscillation signal.

  Some oscillation circuits such as a VCO (voltage controlled oscillation circuit) and a VCXO (voltage controlled crystal oscillation circuit) adjust the oscillation frequency by providing a variable element for changing the reactance X in a positive feedback loop. A specific example will be described with reference to FIG.

  FIG. 16 is a diagram showing a main configuration of the oscillation circuit 9 according to the conventional technique.

  The oscillation circuit 9 is configured as a Colpitts type VCXO in which a crystal resonator is provided in a resonance circuit, and the inverting amplifier 98 is in an active state with an input biased by a negative feedback resistor 97. In addition, a resonance circuit 90 is configured by the crystal oscillator 96 that equivalently functions as an inductor at the oscillation frequency, the two capacitors 92 and 93, and the variable capacitance diode 91. In such an oscillation circuit 9, a reverse bias voltage can be applied to the variable capacitance diode 91 through the resistor 95 by the DC power supply 94, so that the capacitance value of the variable capacitance diode 91 can be changed by changing the output voltage of the DC power supply 94. Control is possible. The resistor 95 is a buffering resistor between the DC power supply 94 and the oscillation voltage generated by the resonance circuit 90.

  In the oscillation circuit 9 described above, the phase of the signal component equal to the resonance frequency of the resonance circuit 90 included in the output signal Vout is inverted and positively fed back to the input of the inverting amplifier 98, thereby oscillating the resonance frequency with an increased amplitude. The voltage can be taken out as the output signal Vout.

  In this oscillation circuit 9, the oscillation frequency fosc can be expressed by the following equation (1).

  Here, L in the above equation (1) is an equivalent inductance value at the oscillation frequency fosc of the crystal resonator 96. Further, C11 in the above equation (1) indicates the capacitance value of the variable capacitance diode 91, and C12 to C13 indicate the capacitance values of the capacitors 92 and 93, respectively.

  According to the above equation (1), it is understood that the oscillation frequency fosc can be changed (adjusted) by changing the capacitance value C11 of the variable capacitance diode 91 by the DC power source 94.

  Furthermore, if the phases of the output signal Vout of the oscillation circuit 9 and the external signal Vt are compared as shown in FIG. 17, external synchronization by a PLL (Phase Locked Loop) method is possible. The external synchronization by the PLL will be briefly described below.

  The phase comparator 81 compares the phases of the external signal Vt and the output signal Vout of the oscillation circuit 9 and outputs a voltage corresponding to the comparison amount. The loop filter 82 is configured as an LPF (Low Pass Filter) that stabilizes the negative feedback loop of the PLL. The oscillation circuit 9 oscillates at a frequency corresponding to the voltage signal Vp from the loop filter 82 and outputs the output signal Vout. Is obtained. With the PLL negative feedback loop as described above, the frequency of the output signal Vout can be matched with the frequency of the external signal Vt while maintaining a constant phase difference, and external synchronization of the output signal Vout can be achieved.

  On the other hand, optical scanners that deflect and scan light beams such as laser light are used in optical devices such as barcode readers, laser printers, and displays. Some of these optical scanners include a polygon mirror that scans reflected light by rotating a polygonal column mirror with a motor, and a galvano mirror that rotates and vibrates a plane mirror using an electromagnetic actuator. However, in such an optical scanner, a mechanical drive mechanism for driving the mirror by a motor or an electromagnetic actuator is necessary. However, since the drive mechanism is relatively large and expensive, There is a problem in that downsizing is hindered and the price is increased.

  Therefore, in order to reduce the size, cost, and productivity of optical scanners, components such as mirrors and elastic beams are integrated using micromachining technology that microfabricates silicon and glass using semiconductor manufacturing technology. Development of molded micro optical scanner is in progress.

  For example, in the micro optical scanner disclosed in Patent Document 1, a vibration system including a mirror unit (optical scanning unit) for performing optical scanning and a torsion bar unit is vibrated (driven) at the resonance frequency. Thus, a large displacement angle can be obtained in the mirror portion.

Japanese Patent No. 2981600

  In the prior art as described above, there is the following problem when the oscillation circuit 9 is used as a drive circuit for driving the optical scanner of Patent Document 1 at a resonance frequency.

  The oscillation circuit 9 is not preferable as a variable element used for an oscillation operation at a relatively low resonance frequency (several kHz to several tens of kHz) because the capacitance value and capacitance change width of the variable capacitance diode 91 are small. Therefore, even if the oscillation circuit 9 is applied as the drive circuit for the optical scanner, it is difficult to adjust (variably control) the oscillation frequency in the resonance frequency range related to the resonance (mechanical resonance) of the optical scanner.

  Further, since a large resonance voltage is applied to both ends of the variable capacitance diode 91 in the oscillation circuit 9 so as to be superimposed on the reverse bias voltage for controlling the capacitance value by the DC power supply 94, the capacitance value of the variable capacitance diode 91 becomes the resonance voltage. It will change under the influence of. In this case, the oscillation frequency is not stabilized in the oscillation circuit 9, and the oscillation frequency cannot be adjusted appropriately.

  The present invention has been made in view of the above problems, and an object thereof is to provide a harmonic oscillation device that can appropriately adjust an oscillation frequency in a resonance frequency range related to mechanical resonance.

  In order to solve the above problems, the invention of claim 1 is a harmonic oscillation device for generating an oscillation signal, wherein (a) an oscillation circuit that oscillates at a first oscillation frequency, and (b) is connected to the oscillation circuit. A possible predetermined passive element, (c) a switching means for switching between a connection state in which the predetermined passive element is connected to the oscillation circuit and a non-connection state, and (d) one cycle related to the oscillation signal A switching control means for switching between the connection state and the non-connection state by the switching means, and the connection state oscillation circuit to which the predetermined passive element is connected includes the first oscillation circuit. Oscillates at a second oscillation frequency different from the frequency.

  According to a second aspect of the present invention, in the harmonic oscillation device according to the first aspect of the invention, the switching control unit is configured to switch the connection by the switching unit at a switching timing at which a signal level related to the oscillation signal becomes a predetermined level. Means for switching between the state and the disconnected state.

  According to a third aspect of the present invention, in the harmonic oscillation device according to the second aspect of the present invention, a period from a specific switching timing related to the switching timing to a next switching timing is convex upward with respect to the signal waveform of the oscillation signal. It is a period included in a period and / or a downwardly convex period.

  According to a fourth aspect of the present invention, in the harmonic oscillation device according to any one of the first to third aspects, the oscillation circuit is provided with a positive feedback loop including a piezoelectric element. .

  According to a fifth aspect of the present invention, in the harmonic oscillation device according to any of the first to third aspects of the invention, the oscillation circuit includes an actuator that drives an optical scanning unit of an optical scanner. A positive feedback loop is provided.

  According to a sixth aspect of the invention, in the harmonic oscillation device according to the fifth aspect of the invention, the actuator is a piezoelectric actuator.

  According to a seventh aspect of the invention, in the harmonic oscillation device according to the fifth aspect of the invention, the actuator is an electromagnetic actuator.

  According to an eighth aspect of the present invention, in the harmonic oscillation device according to the fifth aspect of the present invention, the actuator is an electrostatic actuator.

  According to a ninth aspect of the present invention, in the harmonic oscillation device according to the fifth aspect of the present invention, the actuator is an actuator using a polymer resin.

  According to the first to ninth aspects of the present invention, a connection state in which a predetermined passive element is connected to the oscillation circuit that oscillates at the first oscillation frequency during one period related to the oscillation signal (the oscillation circuit in the connection state). Oscillates at a second oscillation frequency different from the first oscillation frequency) and the non-connected state are switched, so that the oscillation frequency can be appropriately adjusted in the resonance frequency region related to mechanical resonance.

  In particular, according to the second aspect of the present invention, since the connection state and the non-connection state are switched at the switching timing at which the signal level related to the oscillation signal becomes a predetermined level, a stable oscillation operation can be performed.

  According to a third aspect of the present invention, the period from the specific switching timing to the next switching timing is a period included in a period convex upward and / or a period convex downward in the signal waveform of the oscillation signal. More stable oscillation operation can be performed.

  In the invention of claim 4, since the oscillation circuit is provided with the positive feedback loop including the piezoelectric element, the piezoelectric element can be driven at a desired oscillation frequency.

  In the invention of claim 5, since the oscillation circuit is provided with a positive feedback loop including an actuator for driving the optical scanning unit of the optical scanner, the optical scanning unit of the optical scanner can be set in a desired manner. Can be driven at a frequency.

  In the invention of claim 6, since the actuator for driving the optical scanning unit of the optical scanner is a piezoelectric actuator, the optical scanner can be miniaturized.

  In the invention of claim 7, since the actuator for driving the optical scanning unit of the optical scanner is an electromagnetic actuator, the optical scanner can be miniaturized.

  In the invention of claim 8, since the actuator for driving the optical scanning unit of the optical scanner is an electrostatic actuator, the optical scanner can be miniaturized.

  In the invention of claim 9, since the actuator for driving the optical scanning unit of the optical scanner is an actuator using a polymer resin, the optical scanner can be miniaturized.

<First Embodiment>
<Configuration of optical scanner system>
The optical scanner system 100A according to the first embodiment of the present invention includes an optical scanner 1 and a drive circuit 5A for driving the optical scanner 1.

  Below, the structure of the optical scanner 1 and the drive circuit 5A is demonstrated in order.

<Configuration of essential parts of optical scanner 1>
FIG. 1 is a plan view showing the main configuration of the optical scanner 1. 2 is a cross-sectional view as seen from the position II-II in FIG.

  The optical scanner 1 includes a frame portion 10 configured as a “B” -shaped plate-like member and fixed to a housing (not shown) and the like, and a mirror portion 11 included in the frame portion 10. Further, in the optical scanner 1, a torsion bar portion (elastic deformation portion) 12 that performs elastic deformation is connected to the mirror portion 11, and an excitation portion 2 for exciting the mirror portion 11 is connected to the torsion bar portion 12. ing. The end of the excitation unit 2 is connected to the frame unit 10.

  The mirror part 11 has a disk shape, and the front surface Sa and the back surface Sb function as a reflection surface that reflects light. That is, a reflective film made of a metal thin film such as gold or Al (aluminum) is formed on the front surface Sa and the back surface Sb of the mirror unit 11 so that the reflectance of incident light is improved.

  The torsion bar portion 12 is composed of two torsion bars 12a and 12b extending from both ends of the mirror portion 11 to the vibration portion 2 along the center line Ax of the mirror portion 11 parallel to the X axis. The mirror unit 11 is elastically supported with respect to the excitation unit 2 by such a torsion bar unit 12.

  The vibration unit 2 includes bent beams 21 and 22 as plate-like members connected to the torsion bar 12a, and bent beams 23 and 24 as plate-like members connected to the torsion bar 12b. The bending beams 21 to 24, the frame portion 10, the mirror portion 11, and the two torsion bars 12a and 12b are integrally formed by anisotropic etching of a silicon substrate, for example.

  In addition, the vibration unit 2 includes piezoelectric elements 31 to 34 as electro-mechanical conversion elements attached to the upper surfaces of the bending beams 21 to 24 by, for example, an adhesive. The piezoelectric elements 31 to 34 are configured as piezoelectric vibrators for exciting the mirror unit 11, and four unimorph parts Ua to Ud are formed by the piezoelectric elements 31 to 34 and the bending beams 21 to 24. Is done.

  Each of the piezoelectric elements 31 to 34 is provided with an upper electrode Eu and a lower electrode Ed on the front surface and the back surface (FIG. 2). The upper electrodes Eu of the piezoelectric elements 31 to 34 are electrically connected to electrode pads 31u to 34u provided on the frame unit 10 through wires, for example, and the lower electrodes of the piezoelectric elements 31 to 34 are connected to each other. The electrode pads 31d to 34d provided on the frame portion 10 are electrically connected to Ed via wires, for example. A drive voltage can be applied to each of the piezoelectric elements 31 to 34 from the outside of the optical scanner 1 through such an electrode pad.

  With the configuration of the optical scanner 1 as described above, bending deformation occurs in the bending beams 21 to 24 by applying a driving voltage to the piezoelectric elements 31 to 34 via the electrode pads 31u to 34u and 31d to 34d. When the bending beams 21 to 24 are bent as described above, a rotational torque is applied around the central axis Ax to the mirror portion 11 via the torsion bars 12a and 12b, and the mirror portion 11 serving as a movable portion is moved to the central axis Ax. Oscillating vibration can be performed around the center. The oscillation vibration operation of the mirror unit 11 will be described in detail.

  FIG. 3 is a diagram for explaining the swing vibration operation of the mirror unit 11. Here, FIG. 3A and FIG. 3B correspond to FIG. 2 showing a cross section viewed from the position II-II in FIG.

  In the optical scanner 1, the piezoelectric elements 31 to 34 expand and contract by applying an AC voltage in a range in which no polarization inversion occurs between the upper electrode Eu and the lower electrode Ed to the piezoelectric elements 31 to 34, and the unimorphs expand and contract. Therefore, it will be displaced in the thickness direction.

  Therefore, by applying a driving voltage that extends in the longitudinal direction (Y-axis direction) to the piezoelectric element 31 and applying a driving voltage having an opposite phase to the driving voltage to the piezoelectric element 32, the piezoelectric element 32 is contracted. In the unimorph portions Ua and Ub whose one ends are connected to the frame portion 10, the bending beam 21 is bent downward as shown in FIG. 3A, while the bending beam 22 is bent upward. Similarly, by applying a drive voltage having the same phase as that of the piezoelectric element 31 and the piezoelectric element 32 to the piezoelectric element 33 and the piezoelectric element 34, the bending beam 23 is bent downward, while the bending beam 24 is moved upward. To bend. As a result, a rotational torque around the central axis Ax is generated in the mirror section 11 via the torsion bars 12a and 12b. Therefore, as shown in FIG. 3A, the mirror section 11 is inclined in the direction Da about the central axis Ax. Become.

  Further, by applying a driving voltage that extends in the longitudinal direction (Y-axis direction) to the piezoelectric element 32 and applying a driving voltage having an opposite phase to the driving voltage to the piezoelectric element 31, the piezoelectric element 31 is contracted. In the unimorph portions Ua and Ub whose one ends are connected to the frame portion 10, the bending beam 21 is bent upward as shown in FIG. 3B, while the bending beam 22 is bent downward. Similarly, by applying a drive voltage having the same phase as that of the piezoelectric element 31 and the piezoelectric element 32 to the piezoelectric element 33 and the piezoelectric element 34, the bending beam 23 is bent upward, while the bending beam 24 is moved downward. To bend. As a result, a rotational torque around the central axis Ax is generated in the mirror section 11 via the torsion bars 12a and 12b. Therefore, as shown in FIG. 3B, the mirror section 11 is inclined in the rotation direction Db around the central axis Ax. Will be.

  In this way, when the AC drive voltage for rotating the mirror portion 11 in the direction Da (FIG. 3A) and the direction Db (FIG. 3B) is applied to the piezoelectric elements 31 to 34, this application is performed. Since the vertical vibration following the voltage is repeated in the unimorph portions Ua to Ud, a seesaw-like rotational torque is generated in the torsion bars 12a and 12b, and the torsion bars 12a and 12b and the mirror portion 11 swing within a predetermined angle range. It will vibrate.

  Here, when the swing angle of the mirror unit 11 is small, the frequency of the AC voltage applied to the piezoelectric elements 31 to 34 is set to the resonance frequency of the mechanical vibration system related to the optical scanner 1, so that laser light or the like can be obtained. Since the mirror unit (optical scanning unit) 11 that reflects and performs optical scanning is resonantly oscillated, the optical scanner 1 can obtain a large deflection angle (optical scanning angle).

  Hereinafter, the configuration of the main part of the drive circuit 5A for driving the optical scanner 1 at the resonance frequency related to the mechanical resonance will be described below.

<Configuration of main part of drive circuit 5A>
FIG. 4 is a diagram showing a main configuration of the drive circuit 5A according to the first embodiment of the present invention.

  The drive circuit 5A is a harmonic oscillation circuit (sine wave oscillation circuit) configured as a Colpitts oscillation circuit, for example, and generates an oscillation signal. Here, the inverting amplifier 40 is in an active state with its input biased by the negative feedback resistor 41.

  The drive circuit 5A is provided with a positive feedback loop including a piezoelectric element 30 (piezoelectric actuator that drives the mirror unit 11 of the optical scanner 1) 30 that is a combination of the piezoelectric elements 31 to 34 in the optical scanner 1 described above. ing. A resonance circuit SC is constituted by the piezoelectric element 30 and the capacitors 52 to 53. In this resonant circuit SC, the capacitor 51 can be incorporated or removed by a switch 54 having one end connected to the capacitor 51 and the other end connected to the ground. That is, it is possible to switch between a connected state and a non-connected state in which the capacitor (passive element) 51 is connected to the resonance circuit (oscillation circuit) SC using the switch 54. It is assumed that the capacitors 51, 52, and 53 have capacitance values C1, C2, and C3, respectively.

  In addition, the drive circuit 5A has a resistance 42 for increasing the output of the inverting amplifier 40 and causing sufficient rotation (inversion) of the phase by the resonance circuit SC, and an oscillation voltage Va generated at one end Pa of the piezoelectric element 30. A comparator 44 that compares the control voltage Vc for controlling (adjusting) the oscillation frequency and switches the switch 54 on and off is provided. The comparator 44 outputs an “H” signal and an “L” signal that turn on and off the switch 54 according to the magnitude of the oscillation voltage Va with respect to the control voltage Vc as the voltage signal Vsw.

  In the drive circuit 5A configured as described above, the switch 54 that is turned on / off by the comparator 44 causes the capacitance value related to the oscillation operation of the resonance circuit SC to be 3 and the combined capacitance value of the two capacitors 52 and 53. It is switched between the combined capacitance values of the two capacitors 51, 52, 53. As a result, the oscillation frequency of the oscillation circuit 5A can be selected from high and low frequencies (detailed later).

  Next, the operation of the drive circuit 5A as described above will be described.

<Operation of Drive Circuit 5A>
FIG. 5 is a diagram showing an equivalent circuit 30c obtained by equivalently converting each mechanical element related to the oscillation vibration of the mirror unit 11 into an electric element. The equivalent circuit 30c is a circuit viewed from both ends Pa and Pb of the piezoelectric element 30 in the drive circuit 5A (FIG. 4).

  The capacitor 43 represents the capacitance of the piezoelectric element 30 and has a capacitance value Ca determined from the dielectric constant and shape of the dielectric forming the piezoelectric elements 31 to 34.

  The capacitor 471 is an equivalent element of a spring determined by combining the elasticity of the piezoelectric elements 31 to 34 and the elasticity of the bending beams 21 to 24 to which the piezoelectric elements 31 to 34 are attached. The capacitance value Cp of the capacitor 471 is the reciprocal of the spring constant.

  The inductor 472 is an equivalent element determined by combining the mass of the piezoelectric elements 31 to 34 and the mass of the bending beams 21 to 24, and has an inductance value Lp.

  The resistor 473 is an equivalent device that represents an internal loss related to the excitation vibration of the piezoelectric elements 31 to 34 and the bending beams 21 to 24, and has a resistance value Rp.

  The series resonance circuit Wp is formed by the capacitor 471, the inductor 472, and the resistor 473.

  The capacitor 481 is an equivalent element of a spring related to the torsion bars 12a and 12b, and has a capacitance value Cm.

  The inductor 482 is an equivalent element corresponding to the moment of inertia of the mirror unit 11 and has an inductance value Lm. Here, the current Im flowing through the inductor 482 corresponds to the angular velocity related to the oscillation of the mirror 11.

  The resistor 483 is an equivalent element that represents a loss in a resonance circuit including the capacitor 481 and the inductor 482, and mainly represents a friction loss with air due to the oscillation of the mirror portion 11.

  In the equivalent circuit 30c as described above, the voltage (corresponding to the rotational torque) applied to both ends Pa and Pb of the equivalent circuit 30c is configured by the above-described series resonance circuit Wp, the capacitor 481, the inductor 482, and the resistor 483. The current Im corresponding to the angular velocity ω of the mirror portion 11 flows through the inductor 482 after being divided by the parallel resonance circuit Wm.

  Next, the operation of the equivalent circuit 30c will be described.

  FIG. 6 is a diagram for explaining the frequency characteristics related to the equivalent circuit 30c. Here, FIG. 6A shows the relationship between the reactance X and the frequency f related to the equivalent circuit 30c. FIG. 6B and FIG. 6C show the relationship between the current Im flowing through the inductor 482 and its phase delay θm and the frequency f. 6A to 6C show the frequency characteristics when the losses of the series resonant circuit Wp and the parallel resonant circuit Wm are ignored (a sufficiently high Q value).

  The frequency characteristic of reactance X shown in FIG. 6A will be considered below. Since the resonance frequency fp of the series resonance circuit Wp corresponding to the unimorph parts Ua to Ud is normally set sufficiently higher than the resonance frequency frm of the parallel resonance circuit Wm related to the mirror part 11, the parallel resonance circuit When considering the frequency characteristics near the resonance frequency frm with respect to Wm, the inductor 472 of the series resonance circuit Wp is omitted. Similarly, when considering the frequency characteristics in the vicinity of the resonance frequency fp related to the series resonance circuit Wp, the inductor 482 of the parallel resonance circuit Wm is omitted.

  Each frequency fo1, fr1, frm, fop, fo2, fr2 shown in FIG. 6A is calculated by the following equations (2) to (7).

  Regarding the oscillation frequency of the drive circuit 5A, since the capacitors 51 to 53 are capacitive (C characteristics), the reactance X is a positive (plus) value in the frequency characteristics shown in FIG. 6A, that is, inductance (L characteristics). Will oscillate in the frequency ranges Ra and Rb.

  At the frequency fo1 shown in FIG. 6A, the parallel resonance circuit Wm related to the mirror unit 11 becomes inductive (L) and series resonance occurs with the capacitor 471. A large resonance voltage is generated at both ends, and a large resonance current Im flows through the inductor 482. That is, at the frequency (resonance frequency) fo1, a relatively large angular velocity is generated with respect to the oscillation of the mirror portion 11.

  Specifically, at the resonance frequency fo1, the maximum value of the current Im is obtained as shown in FIG. 6B, and the phase delay θm is changed from (+90) degrees to (−90) as shown in FIG. 6C. It changes rapidly every time.

  From the above, the oscillation frequency of the drive circuit 5A is very close to the frequency fo1 in the frequency range Ra.

  In the continuous oscillation state in the drive circuit 5A, the resonance frequency of the current Im is obtained by the peripheral circuit (capacitors 51 to 53, the resistor 42) of the piezoelectric element 30 so that the characteristic is almost equal to the oscillation frequency. This mechanical vibration also becomes a resonance state, and the maximum optical scanning angle is obtained.

  Further, since the frequency characteristic of the reactance X related to the equivalent circuit 30c indicates inductance (L property), the oscillation voltage generated at both ends Pa and Pb of the piezoelectric element 30 (FIG. 4) corresponding to the equivalent circuit 30c, and the inductor 482 Oscillates while maintaining a phase difference of about 90 degrees with the current Im flowing through the.

  In the drive circuit 5A of the present embodiment, there is a possibility of oscillation in the frequency range Rb showing the inductance (L property) in the frequency characteristic of the reactance X shown in FIG. In order to prevent this, the frequency difference between the frequency range Ra and the frequency range Rb is utilized to sufficiently reduce the gain of the positive feedback loop of the drive circuit 5A in the frequency range Rb so that the oscillation condition is not satisfied in the frequency range Rb. It is good to make it. For example, it is effective to set the frequency characteristic of the inverting amplifier 40 to a low-pass type, or to insert a trap circuit or LPF circuit.

  In the drive circuit 5A, the capacitor 51 can be connected to or disconnected from the resonance circuit SC using the switch 54 as described above. The oscillation frequencies fomL and fomH when the switch 54 is on and off are calculated by the following equations (8) and (9).

(I) Oscillation frequency fomL when switch 54 is on:

(II) Oscillation frequency fomH when switch 54 is off:

  However, LpmL and LpmH in the above equations (8) and (9) are equivalent inductance values of the piezoelectric element 30 at the oscillation frequencies fomL and fomm.

  As described above, in the drive circuit 5A, the two oscillation frequencies fomL and fomH (fomL <fomH) can be selected by turning the switch 54 on and off. That is, when the switch 54 is off, the capacitor 51 is not connected to the resonance circuit (oscillation circuit) SC (non-connection state), and the resonance circuit SC oscillates at the oscillation frequency (first oscillation frequency) LpmH. When ON, the capacitor 51 is connected to the resonance circuit (oscillation circuit) SC (connected state), and oscillation occurs at an oscillation frequency (second oscillation frequency) LpmL different from the oscillation frequency LpmH. In this way, in the drive circuit 5A capable of switching between the two oscillation frequencies fomL and fomH, a continuous variable operation of the oscillation frequency is possible. The variable operation of the oscillation frequency will be described below. In the following description, it is assumed that the drive circuit 5A is in the continuous oscillation state.

  FIG. 7 is a diagram for explaining the variable operation of the oscillation frequency in the drive circuit 5A.

  Each operation of the drive circuit 5A in the period Ta, the period Tb, and the period Tc shown in FIG.

(i) Period Ta
In the period Ta, since the oscillation voltage Va is lower than the control voltage Vc, the comparator 44 outputs an “L” signal to turn off the switch 54. As a result, since the capacitor 51 is not connected to the resonance circuit SC, the capacitance value related to the resonance operation of the resonance circuit SC becomes the combined capacitance value of the two capacitors 52 and 53, and the oscillation frequency shown in the above equation (9) The oscillation operation at fomH is performed.

(ii) Period Tb
In the period Tb, since the oscillation voltage Va is higher than the control voltage Vc, the comparator 44 outputs an “H” signal to turn on the switch 54. As a result, since the capacitor 51 is connected to the resonance circuit SC, the capacitance value related to the resonance operation of the resonance circuit SC becomes the combined capacitance value of the three capacitors 51 to 53, and the oscillation shown in the above equation (8). An oscillation operation at the frequency fomL is performed.

(iii) Period Tc
In the period Tc, the oscillation voltage Va is lower than the control voltage Vc, and thus the oscillation operation similar to that in the period Ta is performed.

  Since each operation in the period Ta to Tc described above is performed during one cycle of the oscillation voltage Va, an oscillation operation at an intermediate frequency can be performed with respect to the two oscillation frequencies fomH and fomL.

  Specifically, the switch 54 is turned on / off during one period related to the oscillation voltage (oscillation signal) Va to switch between a connected state and a non-connected state in which the capacitor 51 is connected to the resonance circuit SC. As a result, the voltage waveform of the period Tb is replaced from the waveform of the oscillation frequency fomH to the waveform of the oscillation frequency fomL, so that the voltage waveform Ka (broken line) changes to the voltage waveform Kb (solid line) and the cycle of the oscillation voltage Va is periodic. It is extended from Th to period Thr.

  Here, the start time and end time of the period (hereinafter also referred to as “replacement period”) Tb replaced with the waveform of the oscillation frequency fomL are timings at which the oscillation voltage Va coincides with the control voltage Vc. In other words, at the switching timing when the oscillation voltage (signal level related to the oscillation signal) Va becomes the control voltage (predetermined level) Vc, the switch 54 switches between the connected state and the non-connected state in which the capacitor 51 is connected to the resonance circuit SC. Is done. The period from the switching timing (specific switching timing) corresponding to the start time of the replacement period Tb to the next switching timing corresponding to the end time of the replacement period Tb relates to the signal waveform of the oscillation voltage (oscillation signal) Va. The period is included in the upwardly convex period.

  Thus, the on / off operation of the switch 54 is performed at the switching timing at which the oscillation voltage Va becomes the control voltage Vc because the potential at both ends of the capacitor 51 when the switch 54 is on and the capacitor when the switch 54 is off. This is because the potentials at both ends of 51 are made equal to prevent a sudden charging current from flowing through the capacitor 51 when the switch 54 is switched on and off. As a result, the oscillation operation in the drive circuit 5A becomes more stable.

  From the above, the oscillation frequency can be varied by adjusting the control voltage Vc and changing the replacement period Tb to be replaced with another oscillation frequency fomL waveform. Specifically, as shown in FIG. 8 showing the characteristics of the oscillation frequency fo with respect to the control voltage Vc, the oscillation frequency of the drive circuit 5A is changed from the lower oscillation frequency fomL to the higher one by changing the voltage value of the control voltage Vc. Can be controlled continuously up to the oscillation frequency fomH.

  For example, as shown in FIG. 9, if the control voltage Vc is changed from the voltage value Vc1 to the voltage value Vc2, the replacement period decreases from the period Tb1 to the period Tb2, so the oscillation period of the oscillation voltage Va is shortened from the period Thr1 to the period Thr2. Is done. Further, if the control voltage Vc is changed from the voltage value Vc2 to the voltage value Vc3, the switch 54 is maintained in the OFF state and the replacement period disappears, so the oscillation period of the oscillation voltage Va becomes the shortest period Th. Therefore, in the driving circuit 5A, the oscillation frequency fom can be controlled by adjusting the control voltage Vc as shown in FIG.

  Note that since voltage waveforms having different frequencies are synthesized by the switching operation of the oscillation frequencies fomL and fomH by the switch 54, waveform distortion occurs in the oscillation voltage Va, but for the reasons described below, the waveform distortion is practically negligible. The impact of has been reduced.

  FIG. 7B is a diagram showing a waveform of the current Im flowing through the inductor 482. Here, the current Im corresponds to the angular velocity related to the oscillation of the mirror 11 as described above.

  Even when the oscillation voltage Va generated at both ends Pa and Pb of the piezoelectric element 30 has some waveform distortion as shown in FIG. 7A, the reactance of the inductor 482 is proportional to the frequency. Only a high-frequency current flows in inverse proportion to the order (frequency) of the high-frequency voltage. Accordingly, as shown in FIG. 7B, the current Im flowing through the inductor 482, that is, the waveform distortion with respect to the angular velocity of the mirror portion 11 is reduced compared to the waveform distortion of the oscillation voltage Va shown in FIG. It becomes.

  Further, the distortion of optical scanning due to the oscillation of the mirror part 11 generally appears as a distortion of the displacement angle of the mirror part 11. Here, the displacement angle relating to the oscillation vibration of the mirror portion 11 corresponds to the charge amount Qm obtained by integrating the current Im. Therefore, as shown in FIG. 7C, the amount of charge Qm obtained by integrating the current Im, that is, the waveform distortion with respect to the displacement angle of the mirror portion 11 is further reduced as compared with the waveform distortion of the current Im shown in FIG. Will be.

  From the above, the distortion of the displacement angle of the mirror section 11 that directly affects the optical scanning is greatly reduced compared to the waveform distortion of the oscillation voltage Va, and the distortion level has no practical effect. .

  By the operation of the drive circuit 5A as described above, the switch 54 is turned on / off during one cycle related to the oscillation voltage Va, and the connection state and the non-connection state in which the capacitor 51 is connected to the resonance circuit SC. Therefore, the oscillation frequency can be appropriately adjusted in the resonance frequency range of the mechanical resonance related to the optical scanner 1.

  In the drive circuit 5A, the period from the start point to the end point of the replacement period Tb is an upwardly convex period (peak period) related to the signal waveform of the oscillation voltage Va as shown in FIG. The period included is not essential, and may be a period included in a downwardly convex period (valley part) related to the signal waveform of the oscillation voltage Va.

Second Embodiment
The optical scanner system 100B according to the second embodiment of the present invention has a configuration similar to that of the optical scanner system 100A of the first embodiment, but the configuration of the drive circuit is different.

  Below, the drive circuit 5B of 2nd Embodiment is demonstrated in detail.

<Configuration of main part of drive circuit 5B>
FIG. 10 is a diagram showing a main configuration of a drive circuit 5B according to the second embodiment of the present invention.

  The drive circuit 5B has a configuration similar to that of the drive circuit 5A of the first embodiment, but is mainly different in that it includes two sets of the capacitor 51, the switch 54, and the comparator 44 of the first embodiment. .

  That is, the drive circuit 5B includes two capacitors 51a and 51b having the same capacitance values C1a and C1b, and two switches 54a and 54b for incorporating and removing these capacitors 51a and 51b from the resonance circuit SC. And two comparators 44a and 44b for comparing the oscillation voltage Va and the control voltage ± Vc to switch the switches 54a and 54b on and off. Furthermore, the drive circuit 5B has an inverter 45 that inverts the output of the comparator 44b.

  The variable operation of the oscillation frequency in the drive circuit 5B configured as described above will be described.

  FIG. 11 corresponds to FIG. 7A and is a diagram for explaining the variable operation of the oscillation frequency in the drive circuit 5B.

  In the drive circuit 5B, the positive and negative voltage values (+ Vc, −Vc) having the same absolute value (voltage magnitude) and the oscillation voltage Va are compared by the comparators 44a and 44b, and 2 in one cycle of the oscillation voltage Va. Times, switching to another oscillation frequency is performed.

  Specifically, as shown in FIG. 11, in the period Tbp in which the oscillation voltage Va is higher than the control voltage (+ Vc), the switch 54a is turned on by the comparator 44a, and the capacitor 51a is connected to the resonance circuit SC. On the other hand, in a period Tbm in which the oscillation voltage Va is lower than the control voltage (−Vc), the switch 54b is turned on by the comparator 44b and the inverter 45, and the capacitor 51b is connected to the resonance circuit SC.

  As a result, the voltage waveform of the period (replacement period) Tbp is replaced with the waveform of the oscillation frequency fomH, and the voltage waveform of the period (replacement period) Tbm is replaced with the waveform of the oscillation frequency fomL. The voltage waveform Ja (broken line) changes to the voltage waveform Jb (solid line), and the cycle of the oscillation voltage Va is extended.

  Here, the start time and end time of the replacement periods Tbp and Tbm are timings at which the oscillation voltage Va coincides with the control voltages + Vc and −Vc. That is, the capacitor 51a or the capacitor 51b is connected to the resonance circuit SC by the switches 54a and 54b at the switching timing at which the oscillation voltage (signal level related to the oscillation signal) Va becomes the respective control voltages (predetermined levels) + Vc and −Vc. Switching between a connected state and a disconnected state is performed. The period from the switching timing (specific switching timing) corresponding to the start time of each replacement period Tbp, Tbm to the next switching timing corresponding to the end time of each replacement period Tbp, Tbm is an oscillation voltage (oscillation signal). This is a period included in the upward convex period and the downward convex period related to the Va signal waveform.

  In this manner, the switches 54a and 54b are turned on / off at the switching timing when the oscillation voltage Va becomes the control voltages + Vc and -Vc to switch the connection / disconnection of the separate capacitors 51a and 51b as in the first embodiment. Similarly, the potentials at both ends of the capacitors 51a and 51b when the switches 54a and 54b are turned on are equal to the potentials at both ends of the capacitors 51a and 51b when the switches 54a and 54b are turned off. This is to prevent a sudden charging current from flowing in each of the capacitors 51a and 51b during on / off switching. Thereby, the oscillation operation in the drive circuit 5B becomes more stable.

  By the operation of the drive circuit 5B as described above, the oscillation frequency can be appropriately adjusted in the resonance frequency region of the mechanical resonance related to the optical scanner 1 as in the first embodiment.

  Further, in the drive circuit 5B, since the two replacement periods Tbp and Tbm as shown in FIG. 11 are provided in one cycle of the oscillation voltage Va, the oscillation voltage Va becomes a distorted waveform of a symmetric wave. The next high frequency component is canceled, and the waveform distortion of the oscillation voltage Va can be reduced by the drive circuit 5A of the first embodiment.

<Third Embodiment>
The optical scanner system 100C according to the third embodiment of the present invention has a configuration similar to that of the optical scanner system 100A according to the first embodiment, but the configuration of the drive circuit is different.

  Hereinafter, the drive circuit 5C of the third embodiment will be described in detail.

<Configuration of main part of drive circuit 5C>
FIG. 12 is a diagram showing a main configuration of a drive circuit 5C according to the third embodiment of the present invention.

  The drive circuit 5C has a configuration similar to that of the drive circuit 5A of the first embodiment, but with respect to the drive circuit 5A, a piezoelectric element SN for detecting the swing angle of the mirror unit 11 and the piezoelectric circuit The difference is that a detection circuit 46 including an element SN is added.

  The piezoelectric element SN functions as a displacement angle detection sensor that is attached to the torsion bar 12a and detects the displacement angle of the mirror unit 11 as shown in FIG.

  The detection circuit 46 amplifies the output signal from the piezoelectric element SN and removes noise.

  In the drive circuit 5C configured as described above, the phase difference inverted by (−180) degrees with respect to the oscillation voltage Va generated at the terminal Pa of the piezoelectric element 30 with respect to the phase of the output signal Vn output from the detection circuit 46. Can be secured. This is because a phase difference of (−90) degrees occurs in the current (corresponding to the angular velocity of the mirror unit 11) Im flowing through the inductor 482 with respect to the oscillation voltage Va, and the charge amount (mirror unit 11) obtained by integrating the current Im. This is because a phase difference of (−90) degrees is further generated at a displacement angle of (−180) degrees, resulting in a total phase difference of (−180) degrees.

  By using the output signal Vn of the detection circuit 46 as described above, the phase change relating to the vibration near the resonance frequency of the mirror unit 11 as shown in FIG. If Vn is input to the inverting amplifier 40 and a necessary amount is inverted and amplified, the output from the inverting amplifier 40 becomes positive feedback and contributes to the oscillation operation.

  By the operation of the drive circuit 5C as described above, the oscillation frequency can be appropriately adjusted in the resonance frequency region of the mechanical resonance related to the optical scanner 1 as in the first embodiment.

  Further, in the drive circuits 5A and 5B of the first embodiment and the second embodiment described above, the frequency range Ra showing the inductance (L property) depending on the design of the piezoelectric elements 31 to 34 and the mirror part 11 (FIG. 6 ( In a)), the rotation of the phase of the impedance of the piezoelectric element 30 is insufficient, and it may become incompatible with the characteristics of the peripheral circuits related to the oscillation operation of the inverting amplifier 40 and the like, which may make it difficult to continuously oscillate. On the other hand, in the drive circuit 5C of the present embodiment, since the output signal Vn of the detection circuit 46 that detects the displacement angle related to the oscillation vibration of the mirror unit 11 is input to the inverting amplifier 40 as described above, continuous oscillation is performed. It can be done reliably.

  In the detection circuit 46 of the drive circuit 5C, it is not essential to detect the displacement angle of the mirror unit 11 using the output signal of the piezoelectric element (piezoelectric sensor) SN, and the amplitude of the mirror unit 11 near the resonance frequency. If the influence on the phase is sufficiently small, the displacement angle of the mirror unit 11 may be detected using another type of sensor (for example, PSD (Position Sensitive Detector) or CCD line sensor).

<Modification>
In each of the above embodiments, waveform distortion may be reduced by a circuit configuration described below.

  As shown in FIG. 13, if the oscillation frequency is adjusted (coarse adjustment) using a trimmer 55 of a variable capacitance element connected in parallel to the capacitor 52, the above-described replacement period in which the capacitor 51 is connected can be shortened. As a result, the waveform distortion in the oscillation voltage Va can be reduced.

  Further, as shown in FIG. 14, when a plurality of capacitors 56a and 56b connected in parallel to the capacitor 52 are selectively connected by switches 57a and 57b to adjust the oscillation frequency (coarse adjustment), the capacitor 51 becomes The above-described replacement period to be connected can be shortened. As a result, the waveform distortion in the oscillation voltage Va can be reduced.

  The oscillation frequency switching capacitor and switch in each of the above embodiments may not be configured as shown in FIG. 4 or the like as long as the oscillation frequency can be switched and continuous oscillation can be performed. For example, a circuit configuration in which an oscillation frequency switching capacitor 51 is connected in series with a capacitor 52 as shown in FIG. Even in such a configuration, the oscillation frequency is switched by turning on the switch 54. Note that the resistor 58 in FIG. 15 is a resistor for limiting the discharge current of the capacitor 51.

  In each of the above embodiments, it is not essential to use the voltage Va at one end Pa of the piezoelectric element 30 as an oscillation voltage to be referred to by the comparator, as long as the node can obtain an oscillation voltage with small waveform distortion and time delay. Any node of the drive circuit may be employed. For example, when the oscillation voltage Va at one end Pa of the piezoelectric element 30 is referred to by a comparator via a buffer circuit, an oscillation voltage that is not affected by the input impedance of the comparator can be obtained. In the drive circuit 3C of the third embodiment, the output voltage Vn from the detection circuit 46 (FIG. 12) may be referred to by the comparator 44.

  In the comparators in the above embodiments, it is not essential to refer to the oscillation voltage, and the oscillation current may be referred to.

  In the above embodiments, it is not essential to employ a Colpitts type oscillation circuit, and a harmonic oscillation circuit configured as an LC circuit or an RC circuit may be employed.

  In the drive circuits in the above embodiments, it is not essential to switch the oscillation frequency by connecting a capacitor to the resonance circuit SC, and the oscillation frequency may be switched by connecting an inductor or a resistor. That is, in each of the above embodiments, the oscillation frequency can be adjusted (variable control) by connecting / disconnecting passive elements (impedance elements) such as inductors, capacitors, and resistors.

  In the optical scanner in each of the above-described embodiments, it is not essential to use a piezoelectric element as an actuator for swinging and displacing the mirror unit 11. An electromagnetic actuator such as a VCM, an electrostatic actuator such as an electrostatic vibrator, An actuator using a polymer resin (polymer) may be used. When a polymer resin is used as the actuator, the bending beams 21 to 24, the frame portion 10, the mirror portion 11, and the two torsion bars 12a and 12b can be integrally formed with the polymer resin. .

  The present invention can be applied not only to a drive circuit for driving an optical scanner but also to a general VCO (voltage controlled oscillation circuit) or VCXO (voltage controlled crystal oscillation circuit).

2 is a plan view showing a main configuration of the optical scanner 1. FIG. It is sectional drawing seen from the II-II position of FIG. FIG. 6 is a diagram for explaining a swinging vibration operation of the mirror unit 11. It is a figure which shows the principal part structure of 5 A of drive circuits which concern on 1st Embodiment of this invention. It is a figure which shows the equivalent circuit 30c which carried out equivalent conversion of each mechanical element relevant to the rocking | fluctuation vibration of the mirror part 11 to an electrical element. It is a figure for demonstrating the frequency characteristic regarding the equivalent circuit 30c. It is a figure for demonstrating the variable operation | movement of the oscillation frequency in the drive circuit 5A. It is a figure which shows the characteristic of the oscillation frequency fo with respect to the control voltage Vc. It is a figure for demonstrating the variable operation | movement of the oscillation frequency in the drive circuit 5A. It is a figure which shows the principal part structure of the drive circuit 5B which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the variable operation | movement of the oscillation frequency in the drive circuit 5B. It is a figure which shows the principal part structure of 5 C of drive devices which concern on 3rd Embodiment of this invention. It is a figure for demonstrating the circuit structure concerning the modification of this invention. It is a figure for demonstrating the circuit structure concerning the modification of this invention. It is a figure for demonstrating the circuit structure concerning the modification of this invention. It is a figure which shows the principal part structure of the oscillation circuit 9 which concerns on a prior art. 4 is a diagram for explaining external synchronization in an oscillation circuit 9. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical scanner 5A-5C Drive circuit 11 Mirror part 12 Torsion bar part 12a, 12b Torsion bar 21-24 Curved beam 30 Piezoelectric element 30c which combined the piezoelectric elements 31-34 Equivalent circuit 31-34 Piezoelectric element 40, 98 Inversion amplifier 41, 97 Negative feedback resistors 44, 44a, 44b Comparator 45 Inverter 46 Detection circuits 51-53, 51a, 51b, 56a, 56b, 92, 93 Capacitors 54, 54a, 54b, 57a, 57b Switch 55 Trimmer 91 Variable capacitance diode 100A ˜100C Optical scanner system 482 Inductor Im Current SC flowing through inductor 482 Resonance circuit Va Oscillation voltage Vc Control voltage

Claims (9)

A harmonic oscillation device that generates an oscillation signal,
(a) an oscillation circuit that oscillates at a first oscillation frequency;
(b) a predetermined passive element connectable to the oscillation circuit;
(c) switching means for switching between a connection state in which the predetermined passive element is connected to the oscillation circuit and a non-connection state;
(d) switching control means for causing the switching means to switch between the connected state and the disconnected state during one cycle related to the oscillation signal;
With
The harmonic oscillation device, wherein the oscillation circuit in a connected state to which the predetermined passive element is connected oscillates at a second oscillation frequency different from the first oscillation frequency. The harmonic oscillation device according to claim 1,
The switching control means includes
Means for causing the switching means to switch between the connected state and the disconnected state at a switching timing at which the signal level related to the oscillation signal becomes a predetermined level;
A harmonic oscillation device comprising: The harmonic oscillation device according to claim 2,
The period from the specific switching timing to the next switching timing related to the switching timing is a period included in the upwardly convex period and / or the downwardly convex period of the signal waveform of the oscillation signal. Oscillator. The harmonic oscillation device according to any one of claims 1 to 3,
A harmonic oscillation device, wherein the oscillation circuit is provided with a positive feedback loop including a piezoelectric element. The harmonic oscillation device according to any one of claims 1 to 3,
A harmonic oscillation device, wherein the oscillation circuit is provided with a positive feedback loop including an actuator that drives an optical scanning unit of an optical scanner. The harmonic oscillation device according to claim 5,
The harmonic oscillation device, wherein the actuator is a piezoelectric actuator. The harmonic oscillation device according to claim 5,
The harmonic oscillation device, wherein the actuator is an electromagnetic actuator. The harmonic oscillation device according to claim 5,
The harmonic oscillation device, wherein the actuator is an electrostatic actuator. The harmonic oscillation device according to claim 5,
The harmonic oscillator is an actuator using a polymer resin.

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