JP2006323001A - Oscillator device and optical deflector using the same - Google Patents

Abstract

In an oscillator device such as an optical deflector, a vibration waveform with respect to time of a rotation angle of a movable member such as a scanning mirror that rotates and vibrates is not a sine waveform but a substantially triangular waveform.
An oscillating device such as an optical deflector includes a movable member 10 such as a scanning mirror that is supported by a support means 11 so as to be able to vibrate by rotating about a rotation axis, and the movable member 10 about a rotation axis. Drive means for driving to vibrate by rotating around the center position, and restoring means 20 for determining a rotational vibration range of the movable member 10 and generating a restoring force for returning the movable member 10 toward the center position. Have.
[Selection] Figure 3

Description

The present invention relates to an oscillator device that rotates a movable member about a rotation axis to vibrate (rotational vibration), an optical deflector using the same, and the like. In particular, technologies related to the technical field of resonant optical deflectors using mechanical resonance produced by micromechanics technology, scanning displays using this resonant optical deflector, laser beam printers, digital copying machines, etc. The present invention relates to an image forming apparatus.

In recent years, as represented by high integration of semiconductor devices, with the development of microelectronics, various devices have been miniaturized with high functionality. The same applies to an apparatus using a micromachine device (for example, a micro optical deflector, a micro mechanical quantity sensor, a micro actuator, etc. using a movable member that twists and vibrates around the torsion axis) by a micromechanical technology using a silicon process. For example, laser beam printers that perform optical scanning using a micro optical deflector, scanning image display devices such as head mounted displays, and the like have also been improved in function and size.

As a conventional example of an optical deflector that vibrates torsion, a moving magnet type, a moving coil type, and the like can be cited as an example of an electromagnetic configuration.

A configuration example of the moving magnet type scanning mirror is shown in FIG. 14 (see Patent Document 1). In this example, a scanning mirror 1001 (having a glass substrate 1001a, a mirror surface portion 1001b, and a permanent magnet 1001c), a support member 1001d, a driving shaft (rotating shaft) 1001e, and a magnetism generating portion 1002 (having an electromagnetic coil 1002a and a coil frame 1002b). Is provided. This operation is performed as follows. By energizing the electromagnetic coil 1002a and the magnetic force generated from the magnetism generating unit 1002, an attractive force or a restoring force acts on the magnetic pole of the permanent magnet 1001c. Then, the scanning mirror 1001 rotates and vibrates as indicated by an arrow shown in FIG. 14 with the drive shaft 1001e as the rotation center by twisting the support member 1001d. At this time, the scanning mirror 1001 is driven to be angularly displaced at an arbitrary angle in accordance with the magnetic force generated from the magnetic generator 1002.

Further, FIG. 15 shows a configuration example of the moving coil type scanning mirror (see the conventional example of Patent Document 2), where each part is shown separated in the vertical direction). This example includes a base 1101, a pair of left and right support portions 1102 and 1103, a vibrating body 1104 (an outer frame portion 1105, an opening portion 1105A of the outer frame portion 1105, a scanning mirror portion 1106, a pair of left and right beam portions 1107, and a driving electromagnetic coil. 1110), a pair of left and right permanent magnets 1108, 1109, and driving means D. The driving means D includes a pair of left and right permanent magnets 1102 and 1103 disposed on the base 1101 and a driving electromagnetic coil 1110 disposed on the outer peripheral portion of the scanning mirror unit 1106. A reverse alternating drive current is applied. In this configuration, when a drive current that is alternately forward and reverse is supplied to the drive electromagnetic coil 1110 by the drive means D, scanning is performed by the Lorentz force generated by the external magnetic field of the pair of permanent magnets 1102 and 1103 and the current of the drive electromagnetic coil 1110. The mirror 1106 rotates and vibrates about the pair of beams 1107 and 1108 as the rotation axis.

In addition, by alternately applying a voltage to two fixedly arranged drive electrodes, an electrostatic attractive force is applied to the movable member, so that the movable member, which is a scanning mirror, rotates around the rotation axis of the elastic support portion. There is also a type of torsional vibration. The driving means used in these conventional optical deflectors can also be adopted in an oscillator device such as the optical deflector of the present invention.

The scanning mirror causes a mechanical resonance phenomenon by applying a driving signal having a resonance frequency inherent to the scanning mirror to the driving means, and efficiently drives with a relatively large deflection angle (rotation angle, scanning angle). It can be performed. By performing this resonance driving, optical scanning with a wide amplitude can be performed with relatively low input energy.
JP-A-6-82711 JP 2001-117043 A

However, the above-mentioned mirror that rotates and vibrates at the resonance frequency has a sinusoidal relationship with respect to time. Therefore, when it is desired to use a range regarded as a part of the rotational vibration range, the temporal usage range and the amplitude usage range are relatively narrow and are often used for scanning mirrors as a means for forming an image. There were restrictions.

In view of the above problems, an oscillating device such as an optical deflector according to the present invention has a movable member that is supported by a support means so as to be able to vibrate by rotating about a rotation axis, and the movable member has a central position about the rotation axis. A driving means for driving to vibrate by rotating to the center, and a restoring means for determining a rotational vibration range of the movable member and generating a restoring force for returning the movable member toward the center position. .

Further, in view of the above problems, an oscillator device such as an optical deflector according to the present invention has a movable member that is supported by a support means so as to be able to vibrate by rotating about a rotation axis, and a detection that detects a rotation angle of the movable member. And the movable member are driven to vibrate by rotating around the central position about the central position, and the rotational vibration range of the movable member is determined based on the signal from the detection means, and the movable member is moved to the central position. Drive / restoration means for generating a restoring force for returning to the direction.

Further, in view of the above problems, a control method for an oscillating body device such as an optical deflector according to the present invention is the control method for an oscillating body device according to the above aspect, wherein the driving means is driven at a driving frequency substantially equal to the natural frequency of the movable member. By driving, the movable member is rotated and oscillated, and after obtaining the restoring force by the restoring means, the driving frequency and amplitude of the driving means are increased, and the rotational vibration of the movable member having a desired frequency and a substantially triangular waveform is obtained. It is characterized by obtaining.

Further, in view of the above problems, the control method of the oscillator device such as the optical deflector according to the present invention is the above-described control method of the oscillator device, wherein the movable member is moved by the driving / restoring means when the oscillator device is started. Rotational vibration is performed, and thereafter, the method is switched to the rotational vibration method of the movable member by the restoring force generated based on the signal from the rotation angle detection means of the movable member.

In view of the above problems, an image forming apparatus of the present invention includes a light source, a light source modulation unit that modulates the light source, an optical deflector that uses a movable member as a deflection mirror in the oscillator device, a light source modulation unit, and light. Control means for controlling the deflector is provided.

According to the present invention, since the restoring means or the driving / restoring means as described above is provided, a configuration in which the vibration waveform with respect to time of the rotation angle (deflection angle, scanning angle) of the movable member becomes a substantially triangular waveform instead of a sine waveform is realized. it can. In other words, it is possible to realize driving in which the angular velocity is substantially constant in a relatively wide region of the forward path and the return path in the rotational vibration of the movable member.

An embodiment of the present invention will be described while explaining the principle of the oscillator device of the present invention with reference to the drawings. The principle of a resonant optical deflector having a deflection mirror that rotates and oscillates around a rotation axis will be described. This principle is also commonly used for driving an oscillating body device that oscillates an oscillating body about a rotation axis. This is true.

FIG. 3A is a conceptual diagram showing an embodiment for explaining the principle of the oscillator device of the present invention. FIG. 2A is a conceptual diagram of a conventional example of sinusoidal drive shown for comparison.

In the optical deflector of the present embodiment, the scanning mirror 10 that is a movable member is supported on the support substrate so as to be able to rotate and vibrate about the rotation shaft 11 (here, when the rotation shaft 11 is a torsion bar, Its torsional stiffness is very small or almost zero). Also, a reflective surface is formed by forming a highly reflective film such as aluminum or a dielectric multilayer film on one side of the movable member. And by driving a movable member from the outside, a movable member is driven relatively with respect to a support substrate, and incident light which injects into a reflective surface is deflected. At this time, since a restoring means such as a repulsion spring 20 disposed at a predetermined position away from the movable member is provided, the movable member receives a repulsive force or a restoring force near the end of the rotational vibration range. Therefore, the movable member receives a repulsion (restoration) torque having characteristics as shown in FIG. This torque characteristic has a dead zone (a horizontal portion of θ _L >θ> −θ _L in FIG. 3B) in a non-linear vibration having a non-linear conserving system, and a first portion in FIG. This is equivalent to the spring characteristic of a symmetrical broken line having a quadrant and a hatched portion of the third quadrant.

On the other hand, in the optical deflector of FIG. 2A, the scanning mirror 10 as a movable member is only supported on the support substrate so as to be able to twist and vibrate about the rotation shaft 11 of the torsion bar. . Therefore, the movable member only receives the restoring torque due to the characteristics of the torsion bar as shown in FIG.

FIG. 1 shows the rotational vibration motion of the oscillator device of the present invention in comparison with that of the conventional example. In the figure, a sine curve indicated by (I) indicates the relationship between the angular displacement (rotation angle) of the scanning mirror obtained with a conventional resonance type optical deflector and time. In this sine curve, the range regarded as substantially equiangular velocity is the range indicated by A to A in the figure, and the temporal utilization efficiency of this range is low. Here, if a restoring force is applied to the scanning mirror at A and A, the movement of the scanning mirror can move as indicated by (IIa) and (IIb). In this case, the range indicated by (IIa) is a range of substantially equal angular velocity, and the range indicated by (IIb) is a range where the scanning mirror is inverted upon receiving a restoring force.

In the example shown in FIG. 1 as well, in the case of the sine waveform (I), only a range that can be regarded as a substantially equiangular velocity twice in one cycle can be obtained, whereas in the case of driving a substantially triangular waveform, it is the same. It can be seen that the equiangular velocity range can be obtained four times in time, and the time utilization efficiency is high. In the case of a substantially triangular waveform drive, the larger the sine wave period shown in (I), the more times it can be used, and the larger the amplitude of the sine wave shown in (I), the larger the usable amplitude range. Become wider.

In order to create a range indicated by (IIb) in which the scanning mirror is inverted by receiving the restoring force and to realize driving of a substantially triangular waveform, in the present invention, a non-linear vibration having a non-linear preserving system and a dead band with a slope of C A torque characteristic substantially equivalent to the characteristic of a nonlinear spring having a symmetrical broken line is used. Here, “substantially equivalent” means the following. The dead zone does not have to be a complete dead zone, and may be a region having a slight inclination such as that shown in FIG. 2 (b) that is loosened (in this case, the rotation axis also constitutes a restoring means), and The symmetrical broken line characteristic may be a characteristic in which the symmetry is somewhat broken or a characteristic that is somewhat curved. In short, according to the present invention, if a restoring force is generated to return the movable member toward the center position in the vicinity of the end of the rotational vibration range by any means, the sinusoidal curve is triangular to some extent. It is intended to obtain an effect that the range of the substantially equiangular velocity increases as the waveform approaches.

Assuming that the period T of vibration due to this non-linear spring characteristic is given, the vibration equation of the non-linear storage system is as shown in the following expression (1).
I · d ² θ / dt ² + g (θ) = 0 (1)
Here, I is the moment of inertia of the scanning mirror, and θ is the deflection angle (rotation angle) of the scanning mirror.

As shown in FIG.
g (θ) = C (θ−θ _L ) θ ≧ θ _L (in the example of FIG. 3, θ _L is an angle at which the scanning mirror collides with the spring)

= 0 θ _L >θ> −θ _L

= C (θ + θ _L ) θ _L ≧ θ
Then, the solution θ of the above vibration equation changes in a substantially triangular wave with respect to time, and its period T is
T = 4√ (I / C) · {π / 2 + θ _L / (A−θ _L )}, A ≧ θ _L (A is the amplitude of rotational vibration)
It is represented by If the shape of g (θ) is close to that described above, this period T has substantially the same dependency on the amplitude A of the rotational vibration (that is, T increases as A increases). Have. In the description here, the positive direction of the rotation angle of the scanning mirror and the positive direction of the restoring force (torque) T with respect to the center position of the rotational vibration range are opposite to each other.

On the other hand, in the system of FIG. 2, the vibration equation is as follows.
I · d ² θ / dt ² + T = 0 (T is T (torque) shown in FIG. 2B)
If a solution of this vibration equation is obtained, it can be seen that θ changes sinusoidally with respect to time, and this causes the above-mentioned problems.

As described above, in the present invention, since the restoring force characteristic as described above is used, a rotational vibration characteristic having a substantially uniform angular velocity can be obtained in a wide range of −θ _L ≦ θ ≦ θ _L. In order to realize this, in the above-described embodiment, the torsional rigidity of the rotating shaft 11 is lowered with respect to the moment of inertia of the scanning mirror 10 to cause a sine vibration at a natural frequency having a long period and a wide amplitude. Then, a substantially triangular waveform having a wide amplitude range that can be regarded as a substantially equiangular velocity and a narrow range other than that in which the scanning mirror is inverted upon receiving a restoring force is obtained.

If a thin thread-like strong material having little torsional rigidity, such as a carbon nanotube, is used as the rotating shaft 11 of the scanning mirror 10, a symmetrical broken line characteristic having the above ideal play element (dead zone) can be obtained. It becomes possible.

In this embodiment, when scanning the light beam, instead of the conventional resonance type reciprocating scan with a sinusoidal waveform, the resonance type reciprocating scan with a substantially triangular waveform is realized. There are two methods for oscillating the resonance mode (generally referred to as excitation, but generally referred to as driving). The first method is a method in which a portion for exciting (driving) the scanning mirror and a means for applying a restoring force at the deflection end of the scanning mirror are separated (for example, refer to an embodiment of FIG. 4 described later). In this case, the means for providing a restoring force does not provide energy to compensate for the attenuation of the scanning mirror. The second method is a method in which the means for providing the restoring force itself supplies energy that compensates for the attenuation of the scanning mirror. That is, one of the methods is to obtain information on the scanning angle of the scanning mirror and give an instantaneous restoring force in accordance with the timing from the information (for example, see the embodiment in FIG. 10 described later).

In both cases, it is necessary to consider starting until a restoring force is applied to the scanning mirror. In the first method, when an external force having a frequency equal to the inherent rotational frequency of the scanning mirror is applied and the region where the amplitude increases and the restoring force is applied is reached, the amplitude and frequency of the external force under the condition for establishing the resonance motion. To obtain a desired frequency (for example, see the embodiment of FIG. 4 described later). In the second method, a scanning mirror is rotationally oscillated by applying an external force having a frequency equal to the natural frequency of the scanning mirror, and thereafter, scanning angle information of the scanning mirror is obtained, and external force is applied to the moment and restoring force at that moment. To match the desired frequency (for example, see the embodiment of FIG. 10 below).

Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 3A is a conceptual diagram showing Example 1 of the optical deflector in which an elastic spring is disposed just outside the use amplitude range of the scanning mirror to generate a nonlinear spring characteristic having a dead zone. A scanning mirror 10 has a light reflecting surface on the surface side (upper surface side in FIG. 3A). Reference numeral 11 denotes a rotating shaft formed of a torsion bar or the like, which has a sufficiently weak torsional rigidity against the moment of inertia of the scanning mirror 10. The scanning mirror 10 has inherent torsional resonance vibration characteristics having a large amplitude and a long period.

When the scanning mirror 10 is started, it receives an external force (driving force) having a frequency equal to its natural frequency from a driving unit (not shown in FIG. 3A) and slowly around the rotation shaft 11 around the center position. Starts rotating and vibrating. At this time, typically, the driving force is given at a timing when the scanning mirror 10 passes through a substantially central position. Then, the edge of the scanning mirror 10 eventually collides with the repulsion spring 20 disposed at a predetermined position away from the scanning mirror 10 and receives a restoring force.

Thus, after the collision of the scanning mirror 10 with the spring 20 at both ends of the rotational vibration range, the spring 20 is displaced, the scanning mirror 10 is suddenly decelerated and rebounded, and this is repeated, and light having a substantially triangular wave (substantially equal angular velocity). Scanning is realized. FIG. 3B is a graph showing the characteristics of this nonlinear spring. Until the scanning mirror 10 collides with the spring 20 at the rotation angles −θ _L and θ _L , the dead zone is maintained, and the scanning mirror 10 rotates at a substantially constant angular velocity.

Here, if the spring constant is set high (for example, if a non-linear spring characteristic that is substantially orthogonal to the θ axis in FIG. 3B is used by using a hard member), the scanning mirror 10 rebounds at the moment of collision. Is obtained. For example, this corresponds to a case where a collision with a block having a physical property value with which the coefficient of restitution with the scanning mirror 10 can be regarded as approximately 1.

FIG. 4A shows a specific form of this embodiment of the moving magnet type. FIG. 4B shows a cross-sectional view thereof. In FIG. 4, 400 is a scanning mirror frame, 401 is a rotation axis (corresponding to the rotation axis 11), and rotatably holds a scanning mirror 403 (corresponding to the scanning mirror 10) (that is, the rotation axis 401). The torsional stiffness is very small or almost zero). These are integrally formed from a silicon plate by a micromachining technique. A repulsion spring 404 (corresponding to the repulsion spring 20) formed of a silicon oxide film is formed on the scanning mirror frame 400 at a predetermined distance from the scanning mirror 403.

Reference numeral 405 denotes a driving electromagnetic coil, and reference numeral 406 denotes a bulk permanent magnet formed on the back surface of the scanning mirror 403, which is magnetized in a direction substantially perpendicular to the rotating shaft 401. The scanning mirror frame 400 and the driving electromagnetic coil 405 are attached to the substrate 410 as shown. In such a configuration, the permanent magnet 406 receives electromagnetic force from the driving electromagnetic coil 405 and applies rotational vibration force to the scanning mirror 403. In the resonance mode, the permanent magnet 406 starts to be vibrated by an electromagnetic force having a frequency equal to the natural frequency of the scanning mirror 403. As the intensity of the excitation force increases, the amplitude of the rotational vibration increases, and the scanning mirror 403 eventually collides with the repulsion spring 404 (see FIG. 4B). After starting the collision, the period T changes according to the above equation (1). Therefore, if the drive current to the drive electromagnetic coil 405 is controlled and the frequency (1 / T) and the amplitude A are gradually matched with the frequency to be obtained, the desired triangular wave drive and frequency can be obtained.

Although FIG. 4 shows an example of a moving magnet type as a method of driving the scanning mirror by electromagnetic force, it can of course be realized by a moving coil type. In this case, a bulk permanent magnet is provided on the external fixed side, and an electromagnetic coil is formed on the scanning mirror. Moreover, it can replace with electromagnetic force and can also use the drive method by electrostatic attraction. In this case, a voltage is alternately applied to the two drive electrodes fixed and arranged on both sides of the rotation axis of the scanning mirror to alternately apply an electrostatic attractive force to the electrodes sandwiching the rotation axis on the scanning mirror, Oscillates around the axis of rotation.

In FIG. 4, the repulsion spring 404 is provided outside, but a repulsion spring (moving spring) may be provided on the scanning mirror 403 side. According to the first embodiment, an optical deflector in which the scanning mirror can vibrate with a large deflection angle and a substantially triangular waveform can be realized.

(Example 2)
FIG. 5A is a conceptual diagram of Example 2 in which a dead zone is generated by arranging electrodes outside the usable amplitude range of the scanning mirror. A scanning mirror 10 forms a light reflecting surface on the surface side. The scanning mirror 10 has a natural vibration characteristic having a large amplitude and a long vibration period. A movable electrode 30 is attached to the scanning mirror 10, and the movable electrode 30 is previously charged. Reference numeral 11 denotes a rotating shaft, and 31 denotes a counter fixed electrode disposed at a predetermined position away from the scanning mirror 10. Here, both electrodes 30, 31 are positively charged.

Also in this embodiment, the scanning mirror 10 receives an external force (driving force) having a frequency equal to the natural frequency from the driving unit (not shown in FIG. 5A) at the time of starting and slowly rotates around the rotating shaft 11. Starts rotating vibration around the center position. Also in this case, typically, the driving force is given at a timing at which the scanning mirror 10 passes through a substantially central position. The movable electrode 30 receives a restoring force in the vicinity of the opposite fixed electrode 31 near both ends of the rotational vibration range. Thus, at both ends of the rotational vibration range, the scanning mirror 10 is suddenly decelerated and rebounded (that is, receiving a restoring force based on a torque characteristic equivalent to the non-linear spring characteristic), and this is repeated to obtain a substantially triangular wave (substantially equal angular velocity). Optical scanning is realized. FIG. 5B is a graph showing a restoring torque characteristic equivalent to the nonlinear spring characteristic. Here, since it is generally considered that T (torque) 電極 1 / (distance between electrodes) ⁿ (n ≧ 2), the torque is in a substantially dead zone until the movable electrode 30 comes closest to the counter fixed electrode 31. It is in.

Here, as the movable electrode 30 of the scanning mirror 10 approaches the counter fixed electrode 31, the counter fixed electrode 31 is in the form of electric charges so that electrons in the counter fixed electrode 31 do not escape back to the power source side. It is also good to inject. Although the drive unit is omitted in FIG. 5A, a drive method that is not electrostatic attraction, for example, a drive method using electromagnetic force is desirable so as not to interfere with the electrostatic force between the movable electrode 30 and the counter fixed electrode 31.

FIG. 6 shows a cross-sectional view of a specific form of this embodiment of a moving magnet type. Reference numeral 400 denotes a scanning mirror frame, 401 denotes a rotation shaft, and a mirror 403 is rotatably held. These are integrally formed from a silicon plate by a micromachining technique. Reference numeral 600 denotes a movable electrode (corresponding to the movable electrode 30) formed on the surface of the scanning mirror. Reference numeral 601 denotes a counter fixed electrode (corresponding to the counter fixed electrode 31), which is formed on the support member 610 at a predetermined distance from the scanning mirror surface. The movable electrode 600 is preliminarily given a charge (in this case, a positive charge).

Reference numeral 405 denotes a driving electromagnetic coil, and reference numeral 406 denotes a bulk permanent magnet formed on the back surface of the scanning mirror 403. The scanning mirror frame 400 and the driving electromagnetic coil 405 are attached to the substrate 410 as shown. In such a configuration, the permanent magnet 406 receives electromagnetic force from the drive electromagnetic coil 405, and rotational vibration force is applied to the scanning mirror 403. The scanning mirror 403 is vibrated by an electromagnetic force having a frequency equal to its natural frequency. As the exciting force is increased, the movable electrode 600 and the counter fixed electrode 601 on the scanning mirror 403 approach each other and the movable electrode 600 rebounds. Since the electrostatic force has a large non-linearity, a dead zone region as shown in FIG. 5B can be realized. Here again, after the repulsion between the electrodes is started, the period T changes almost in accordance with the equation approximate to the above equation (1). Therefore, if the drive current to the drive electromagnetic coil 405 is controlled and the frequency (1 / T) and the amplitude A are gradually matched with the frequency to be obtained, the desired triangular wave drive and frequency can be obtained.

Although FIG. 6 shows an example of a moving magnet type, it can of course be realized by a moving coil type. In this case, a bulk permanent magnet is formed outside, and an electromagnetic coil is formed on the scanning mirror side. Also in the second embodiment, an optical deflector in which the scanning mirror can vibrate with a large deflection angle and a substantially triangular waveform can be realized.

(Example 3)
FIG. 7A is a conceptual diagram of Example 3 in which a magnetic pole is disposed just outside the use amplitude range of the scanning mirror to generate a torque characteristic equivalent to a spring characteristic having a dead zone. A scanning mirror 10 forms a light reflecting surface on the surface side. Reference numeral 11 denotes a rotating shaft, which has a weak torsional rigidity against the moment of inertia of the scanning mirror 10. The scanning mirror 10 has a natural resonance motion with a large amplitude and a long vibration period. A fixed magnet magnetized as shown in FIG. 7A is attached to the scanning mirror 10. Reference numeral 40 denotes a yoke, and reference numeral 41 denotes an electromagnetic coil. The magnetic pole formed on the yoke 40 is disposed at a predetermined position just outside the use amplitude range of the scanning mirror 10. In the present embodiment, the yoke 40, the electromagnetic coil 41, and the fixed magnet of the scanning mirror 10 constitute a driving / restoring means.

Reference numeral 42 denotes a light source, 43 denotes a light beam, and 44 and 45 denote optical sensors for detecting the deflection angle width of the scanning mirror 10. The scanning mirror 10 is started while resonating by the electromagnetic force generated by the yoke 40 around which the electromagnetic coil 41 is wound. At this time, typically, the electromagnetic force is applied at a timing when the scanning mirror 10 passes through a substantially central position of the rotational vibration. Eventually, when it is detected by the optical sensors 44 and 45 that the scanning mirror 10 has reached a predetermined deflection angle width, the energization timing to the electromagnetic coil 41 is switched, and a short time is reached near the end of the rotational vibration range. A restoring force is applied from the magnetic pole of the yoke 40 to the magnetic pole of the scanning mirror 10. Thus, after that, the method of applying the driving force to the scanning mirror 10 is switched, and is applied by the restoring force or the repulsive force from the magnetic pole of the yoke 40, thereby realizing optical scanning with a substantially triangular waveform. FIG. 7B is a graph showing a torque characteristic equivalent to the non-linear spring characteristic for this restoring force.

FIG. 8 is a perspective view showing a specific form of this embodiment of a moving magnet type. Reference numeral 400 denotes a scanning mirror frame, 401 denotes a rotation shaft, and the scanning mirror 403 is rotatably held. These are integrally formed from a silicon plate by a micromachining technique. Reference numeral 700 denotes an electromagnet (corresponding to the yoke 40) formed at a predetermined position away from the scanning mirror surface. Reference numeral 701 denotes a driving electromagnetic coil (corresponding to the electromagnetic coil 41). Reference numeral 702 denotes a bulk permanent magnet (corresponding to the fixed magnet on the scanning mirror 10), which is configured in the scanning mirror 403. Along with the movement of the scanning mirror 403, at the timing when the permanent magnet 702 approaches the electromagnet 700, the current flowing through the electromagnetic coil 701 is controlled so that the electromagnet 700 and the permanent magnet 702 have the same polarity and a restoring force is applied.

Reference numeral 703 denotes a piezoresistive portion formed at the foot of a torsion shaft (rotating shaft) 401 in order to detect the scanning angle of the scanning mirror 403. The scanning range angle of the scanning mirror 403 can be detected based on the principle that the piezoresistance value changes due to a change in torsional stress of the torsion shaft 401. In such a configuration, at the time of starting the optical deflector, the scanning mirror 403 is rotationally oscillated by the first driving method, and then the driving method is switched based on a signal from the piezoresistor 703 of the rotational oscillation angle of the scanning mirror 403. In this driving method, electromagnetic force is generated at different timing (timing when the permanent magnet 702 approaches the electromagnet 700), and the scanning mirror 403 is rotated and oscillated.

As a method for detecting the scanning angle, a light beam may be used. Alternatively, a counter-planar electrode may be disposed on the lower surface of the scanning mirror and the structure portion facing the lower surface, and the scanning angle may be detected using the change in the capacitance.

FIG. 9 is a cross-sectional view showing another specific embodiment of the present example using the restoring force of electrostatic force. Reference numerals 502 and 503 denote counter electrodes attached to the support substrate 510, and are arranged on the support substrate 510 while maintaining a desired space. In this example, the movable electrode 503 is formed on the back surface of the scanning mirror 403, and an electric charge is given thereto. Here, the counter electrodes 502 and 503 and the movable electrode 503 constitute a driving / restoring means.

In this configuration, at the time of start-up, alternating applied voltages are applied to the electrodes 502 and 503 at the same frequency as the inherent torsional frequency of the scanning mirror 403, and scanning mirror vibration at a low frequency is started. Also in this case, typically, the electrostatic force is given at a timing at which the scanning mirror 10 passes through a substantially central position of the rotational vibration. Reference numeral 801 denotes a laser beam light source, reference numeral 800 denotes a laser beam, and reference numerals 802 and 803 denote optical sensors which are detection means for detecting both ends of the amplitude angle range of the scanning mirror 403. When the scanning mirror 403 reaches a predetermined amplitude, the driving method of the scanning mirror 403 is switched based on the signals of the optical sensors 802 and 803. In other words, a driving method is employed in which alternating voltages that have a large restoring force are applied to the counter electrodes 502 and 503 at different timings with respect to the charge of the movable electrode 503. Thereafter, the vibration frequency is adjusted to a predetermined vibration frequency almost in accordance with an expression approximate to the expression (1).

FIG. 10 is a cross-sectional view showing still another specific embodiment of the present example using a piezoelectric vibration element. Reference numeral 900 denotes a bimorph piezo element attached to the support substrate 510. At the moment when the scanning mirror 403 collides with the element 900, a restoring force is applied to the scanning mirror 403. At the time of starting, another starting method, for example, a method using electromagnetic force or a method using electrostatic force (not shown) is adopted.

Reference numeral 901 denotes a sense coil that detects a change in the magnetic field from the permanent magnet 902 and detects the amplitude angle range of the scanning mirror 402. The permanent magnet 902 and the coil 901 can also serve as driving means at the start. In this embodiment, the piezo element 900 and the starting driving means constitute driving / restoring means.

[Example 4]
In the above embodiment, the scanning mirror, which is a movable member, is rotated and oscillated around a rotating shaft whose torsional rigidity is very small or almost zero. However, the movable member is a cantilever movable member made of an elastic body. The member can be rotated and vibrated by bending of the base portion 550a near the fixed end. The flexural rigidity may be adjusted by adjusting the thickness of the root portion 550a so as to realize a desired non-linear restoring torque characteristic.

FIG. 11 is a cross-sectional view showing a resonance type optical deflector according to the fourth embodiment having such a configuration. In FIG. 11 showing the present embodiment, a scanning mirror 550 is a cantilever movable member, 556 is a drive coil, 558 is a magnetic body attached to the scanning mirror 550, 552 is a base, and 551 is one end of the scanning mirror 550. Is a spacer for fixing and supporting In this configuration, the driving means includes a magnetic body 558 attached so as to move integrally with the scanning mirror 550 and a driving coil 556. The magnetic mirror 558 is magnetized in response to the magnetic field from the drive coil 556 and receives an attractive force from the drive coil 556, or the energization to the drive coil 556 is turned off and the attractive force disappears, whereby the scanning mirror 550 is rotated and oscillated. . In this embodiment, the restoring means includes a repulsion spring 520 and a flexible base portion 551a near the fixed end of the scanning mirror 550 that constitutes a part of the support means. Here, the deflectable root portion 551a has a certain degree of bending rigidity so that the scanning mirror 550 can maintain a horizontal central position when no external force is applied to the scanning mirror 550. Therefore, the dead zone in FIG. 3 is not a complete dead zone but has a slight inclination.

The rotational vibration indicated by the arrow in FIG. 11 of the cantilever type scanning mirror 550 of this embodiment is performed as described above by the drive coil 556 and the magnetic body 558 which are vibration or drive means. As described in the first embodiment, the scanning mirror 550 is driven by a substantially triangular wave by the repulsion spring 520 as a restoring means.

Even in the fourth embodiment that uses the cantilever-type vibrating body utilizing the bending of the root portion 550a near the fixed end, an optical deflector capable of vibrating the scanning mirror with a large deflection angle and a substantially triangular waveform can be realized.

In the above embodiment, the restoring means or the driving / restoring means is provided in the vicinity of both ends of the rotational vibration range of the movable member, but only in the vicinity of one end of the rotational vibration range of the movable member and the other rotation. For example, the end of the vibration range may be determined by giving a certain degree of torsional rigidity to the rotating shaft. Further, the restoring means for generating the restoring force for returning the movable member toward the center position does not necessarily have to be near the end of the rotational vibration range of the movable member, and may be, for example, near the center position. . Then, the detection means detects that the movable member reaches the vicinity of the end of the rotational vibration range, and the restoring means generates electromagnetic force or the like based on the signal from the detection means to return the movable member to the central position. You may do it.

(Example 5)
FIG. 12 is a schematic diagram of this embodiment showing a basic configuration of a laser beam printer using the optical deflector of the present invention. In FIG. 12, 2002 is a laser light source, 2003 is a lens or a lens group, 2004 is a writing lens or lens group (including an fθ lens), and 2006 is a drum-shaped photoconductor (image display surface). Between the two lenses or lens groups 2003 and 2004, an optical deflector 2001 using the resonant scanning mirror of the present invention is disposed. In addition to the driving method of the above embodiment, the optical deflector 2001 outputs rotational vibration timing information to control the lighting and modulation timing of the laser light source 2002 and the rotational driving of the photoconductor 2006. The optical deflector 2001 functions as an optical scanner device that scans light in a one-dimensional direction parallel to the rotation center of the drum-shaped photoconductor 2006. Here, the laser light emitted from the laser light source 2002 is subjected to a predetermined intensity modulation related to the timing of optical scanning, is deflected at a substantially constant angular velocity by the scanning mirror 2001, and is substantially at a uniform speed due to the presence of the fθ lens. Thus, the photosensitive member 2006 is scanned one-dimensionally.

On the other hand, the drum-shaped photoconductor 2006 rotates at a predetermined rotation speed around the rotation center. The surface of the photoreceptor 2006 is uniformly charged by a charger (not shown). Therefore, based on the scanning by the optical deflector 2001 and the rotation of the photosensitive member 2006, the scanned laser light is incident on the surface of the photosensitive member 2006 in a two-dimensional pattern by the writing lens 2004. An electrostatic latent image is formed between the incident portion and the non-light incident portion. Further, a toner image having a pattern corresponding to the electrostatic latent image on the surface of the photoreceptor 2006 is formed by a developing device (not shown), and a visible image is formed on the paper by, for example, transferring and fixing the toner image on the paper (not shown). The

(Example 6)
FIG. 13 is a schematic diagram of this example showing a basic configuration of a laser display which is an optical apparatus using the optical deflector of the present invention. In FIG. 13, 2002 is a laser light source, 2003 is a lens or a lens group, 2004 is a writing lens or lens group (including an fθ lens), and 2005 is a projection surface (image display surface). An optical deflector group 2001 is disposed between the two lenses or lens groups 2003 and 2004. The optical deflector group 2001 includes two scanning mirrors 2001a and 2001b. The light coming from the laser light source 2002 through the lens or the lens group 2003 is deflected around the first direction by the scanning mirror 2001a, and the light deflected by the scanning mirror 2001a is changed to the first direction by the scanning mirror 2001b. A deflecting action around a second direction orthogonal to each other is received. Then, the image is projected onto the projection surface 2005 through the writing lens or lens group 2004 to form an image. The two scanning mirrors 2001a and 2001b are in accordance with the present invention and are fabricated using a semiconductor fabrication process. The laser light incident from the laser light source 2002 is subjected to predetermined intensity modulation related to the optical scanning timing, and is two-dimensionally scanned at two substantially equal angular speeds by the two scanning mirrors 2001a and 2001b.

As described above, the scanned laser light passes through the writing lens 2004 to form an image on the projection surface 2005 at a constant speed. The frequency tracking control, amplitude control, and rotation timing information output are used for the horizontal scanning scanning mirror, and the same processing as in the above embodiment is performed. As a result, the horizontal scanning mirror and the vertical scanning mirror can be synchronized, the position of the scanning beam can be controlled, and a high-quality two-dimensional image can be displayed. In addition, since a scanning mirror that does not require a complicated detection unit is used in the image display device, an ultra-small image display device can be realized. Furthermore, since both high-efficiency mirror driving and driving state detection can be achieved, a display device with low power consumption can be realized.

In this way, by using the optical deflector of the present invention, small and inexpensive optical scanning can be used in place of conventional polygon mirrors in applications where optical scanning linearity is required, particularly in laser printers and scanning image forming apparatuses. A unit can be realized.

In addition, an optical deflector that vibrates with a large deflection angle and a triangular waveform is now desired in order to enhance the functionality of scanning image display devices such as laser beam printers and head-mounted displays that perform optical scanning using micromachine devices. Is in a situation. Under such circumstances, if the equiangular velocity scanning range of the triangular waveform of the optical deflector of the present invention can be utilized, for example, when this is utilized for a laser beam printer or the like, a conventional polygon mirror can be used without rotating at high speed. A relatively wide range of constant speed light scanning is obtained on the photosensitive drum using the fθ lens.

FIG. 1 is a diagram for explaining the principle of realizing a substantially triangular wave drive using a restoring means corresponding to a nonlinear spring according to the present invention. FIG. 2A is a sectional view for explaining a conventional example, and FIG. 2B is a graph showing torsion spring characteristics. FIG. 3A is a cross-sectional view illustrating the configuration principle for carrying out the first embodiment of the present invention, and FIG. 3B is a graph showing the non-linear spring characteristics of the restoring means. 4A is a perspective view for explaining the first embodiment of the present invention, and FIG. 4B is a sectional view thereof. FIG. 5A is a cross-sectional view for explaining the configuration principle for carrying out the second embodiment of the present invention, and FIG. 5B is a graph showing the nonlinear spring characteristic of the restoring means. FIG. 6 is a sectional view for explaining a second embodiment of the present invention. FIG. 7A is a cross-sectional view for explaining the configuration principle for carrying out the third embodiment of the present invention, and FIG. 7B is a graph showing the nonlinear spring characteristic of the restoring means. FIG. 8 is a perspective view illustrating Example 3 using electromagnetic force. FIG. 9 is a cross-sectional view illustrating Example 3 using an electrostatic force. FIG. 10 is a cross-sectional view illustrating Example 3 using mechanical force. FIG. 11 is a cross-sectional view illustrating Example 4 using a cantilever type movable member. FIG. 12 is a block diagram of a one-dimensional image forming apparatus of Embodiment 5 using the optical deflector of the present invention. FIG. 13 is a block diagram of a two-dimensional image display apparatus according to Embodiment 6 using the optical deflector of the present invention. FIG. 14 is a perspective view showing an optical deflector using a conventional moving magnet electromagnetic drive system. FIG. 15 is an exploded perspective view showing a conventional optical deflector using a moving coil electromagnetic drive system.

Explanation of symbols

10, 403 Movable member (scanning mirror)
11, 401 Support means (rotating shaft)
20, 404 Restoration means (repulsion spring)
30, 31, 600, 601 Restoration means (counter electrode)
40, 41, 700, 701, 702 Driving / restoring means (yoke, electromagnetic coil, electromagnet, permanent magnet)
42, 44, 45, 801, 802, 803 Detection means (light source, optical sensor)
405, 406 Driving means (electromagnetic coil for driving, permanent magnet)
502, 503 Driving / restoring means (counter electrode)
703 Detection means (piezoresistive part)
900 Drive / restoration means (piezo element)
901, 902 Detection means (sense coil, permanent magnet)
2001 Optical deflector 2002 of the present invention Light source (laser light source)

Claims (10)

A movable member that is supported by the support means so as to be able to vibrate by rotating about a rotation axis; a drive means for driving the movable member to rotate about a central position about a central position; An oscillator device comprising: a restoring means for determining a rotational vibration range and generating a restoring force for returning the movable member toward the center position. A movable member that is supported by a support means so as to be able to vibrate by rotating about a rotation axis, a detection means that detects the rotation angle of the movable member, and a vibration that rotates the movable member around a rotation axis about a central position. And driving / restoring means for determining a rotational vibration range of the movable member based on a signal from the detection means and generating a restoring force for returning the movable member toward the center position. Oscillator device characterized. The oscillator device according to claim 1, wherein the restoring means or the driving / restoring means is provided in the vicinity of at least one of both ends of the rotational vibration range of the movable member. 4. The torsion bar that supports the movable member so as to be capable of torsional vibration with a relatively weak or almost zero torsional rigidity around a torsion axis that defines the rotating shaft. The oscillator device described. The restoring force generated by the restoring means or the driving / restoring means is a mechanical repulsive force caused by deformation of a spring member generated when the movable member collides, or a repulsive force of electromagnetic force generated when the movable member approaches. The oscillator device according to any one of claims 1 to 4, wherein the oscillator device is a repulsive force of an electrostatic force caused by an injected charge generated when the movable member approaches. 6. The oscillator device according to claim 2, wherein a reflection surface is formed on the movable member, and the detection unit detects a rotation angle of the movable member by detecting an angle of light reflected by the reflection surface. . The oscillator device according to any one of claims 1 to 6, wherein the movable member is a deflection mirror and constitutes an optical deflector. In the control method of the oscillator device according to any one of claims 1 and 3 to 7, the movable member is rotationally vibrated by driving the drive means at a drive frequency substantially equal to the natural frequency of the movable member, Then, after obtaining the restoring force by the restoring means, the driving frequency and amplitude of the driving means are increased to obtain the desired vibration frequency and rotational vibration of the movable member having a substantially triangular waveform. Method. 8. The method for controlling an oscillating body device according to claim 2, wherein the driving / restoring means causes the movable member to oscillate at the time of starting the oscillating body apparatus, and thereafter detects the rotational angle of the movable member. A control method for an oscillator device, characterized in that the method is switched to a rotational vibration method of a movable member by a restoring force generated on the basis of a signal from. An image forming apparatus comprising: a light source; a light source modulating unit that modulates the light source; an optical deflector according to claim 7; and a control unit that controls the light source modulating unit and the optical deflector.

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