JP2012058527A - Light deflector, optical scanner, image forming device, and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light deflector in which variation of resonant frequency due to environment temperature or the like can be adjusted.SOLUTION: A light deflector includes a fixed base 60, a mirror 10 having a light reflection surface, an elastic support member 20 for swingably supporting the mirror 10, and a pair of vibrating beams 50 in which one end is connected to the fixed base 60, the other end is connected to the elastic support member 20, and a piezoelectric member is fixed to a beam-like member. The vibrating beam 50 is composed of a driving beam 30 that generates a torsional deformation in the elastic support member 20 to make the mirror 10 rotationally vibrate in a desired resonant frequency, by being applied with an AC voltage; and a frequency adjusting beam 40 that adjusts the resonant frequency by applying stress to the elastic support member 20.

Description

  The present invention relates to an optical deflector that deflects and scans a light beam such as a laser beam, and more particularly to an optical deflector that uses a piezoelectric power. Further, the present invention relates to an optical scanning device including the optical deflector, The present invention relates to an image forming apparatus provided as a writing unit and an image projecting apparatus provided with the optical deflector as a projection unit scanning unit.

  An optical deflector in which a movable member is provided on a mirror member supported by a pair of torsion springs, and the electrostatic force between the movable electrode and the fixed electrode is used as a driving force to reciprocally vibrate the mirror member using a torsion spring as a rotational axis Is known (see, for example, Patent Documents 1 and 2). Such an optical deflector can maximize the deflection angle of the mirror member when the drive frequency is matched with the resonance frequency of the mirror member.

  In the optical deflector described in Patent Document 1, the mirror member is provided with one or a plurality of pieces that can be easily cleaved by laser beam irradiation, and the moment of inertia of the mirror member is obtained by cleaving the pieces. By adjusting the resonance frequency, the resonance frequency can be adjusted.

  In the optical deflector described in Patent Document 2, the flat tuning electrode provided on the substrate surface facing the back surface of the mirror member (stage) or the electrode provided on the back surface of the mirror member is engaged. The resonance frequency can be adjusted by adjusting the voltage applied to the comb-shaped tuning electrode provided on the substrate surface.

  On the other hand, an optical deflector using a piezoelectric element for driving a mirror member is also known. For example, in Patent Document 3, two pairs of piezoelectric unimorph diaphragms on which piezoelectric elements are formed are connected to a mirror member, and an AC voltage having an opposite phase is applied to the piezoelectric elements of each pair of piezoelectric unimorph diaphragms. An optical deflector that reciprocally vibrates a member about a torsion spring as a rotation axis is described.

  Furthermore, although the structure and behavior of the vibration system are different from those of the optical deflectors mentioned above, a vibrator in which a vibration part having a mirror surface and a fixed part are connected via an elastic deformation part (torsion spring), and its fixed part Patent Document 4 discloses an optical deflector (optical scan) that has a vibration device (for example, a piezoelectric element) that applies high-frequency vibration in a direction orthogonal to the elastically deforming portion to resonate and vibrate the vibrator. In this optical deflector, the resonance characteristics of the vibrator can be adjusted by heating or deforming the elastic deformation portion by a resistance heating element or a piezoelectric element provided in the elastic deformation portion and changing the spring constant of the elastic deformation portion. .

  In an optical deflector that reciprocally vibrates a mirror member with a pair of torsion springs as a rotational axis, the displacement angle of the mirror member becomes maximum when the resonance frequency of the mirror member coincides with the drive frequency. However, the resonance frequency varies due to variations in the dimensions of the torsion spring and mirror member in the manufacturing process, and a sample in which a desired drive frequency deviates from the resonance frequency band is generated at a certain rate. Moreover, the resonance frequency of this type of optical deflector varies depending on the environmental temperature. In general, as the environmental temperature increases, the resonance frequency decreases.

  In the optical deflector described in Patent Document 1, once the resonance frequency is adjusted, it cannot be readjusted, and it cannot cope with the fluctuation of the resonance frequency due to the environmental temperature. Further, the optical deflector described in Patent Document 2 cannot be applied to an optical deflector that uses a piezoelectric element in principle for driving the mirror section.

  In the optical deflector described in Patent Document 4, although it is possible to cope with fluctuations in the resonance frequency due to the environmental temperature, because of the configuration in which the elastic deformation portion is directly deformed by a piezoelectric element or the like provided in the elastic deformation portion, Since the adjustment range of the resonance frequency cannot be widened, and a piezoelectric element or the like must be provided in the narrow elastic deformation portion, the manufacturing becomes complicated.

  It is an object of the present invention to provide an optical deflector that uses a piezoelectric element for driving a mirror portion, and that can adjust fluctuations in resonance frequency due to environmental temperature or the like over a wide range. Another object of the present invention is to provide an optical deflector that is small in size, has good driving efficiency, and can obtain a large rotational amplitude.

  The present invention also provides an optical scanning device provided with such an optical deflector, an image forming device provided with this optical scanning device as an optical writing unit, and an image projection device provided with such an optical deflector as a scanning unit for a projection surface. It is in.

The optical deflector of the present invention includes a fixed base, a mirror portion having a light reflecting surface, an elastic support member that supports the mirror portion so as to be swingable, one end connected to the fixed base, and the other end elastically supported. A vibration beam connected to the support member and having a piezoelectric member fixed to the beam-shaped member;
The vibrating beam generates a torsional deformation in the elastic support member by applying an AC voltage, and rotates and vibrates the mirror portion at a desired resonance frequency, and the elastic beam by applying a DC voltage. It is comprised with the frequency adjustment beam which gives stress to a supporting member and adjusts the said resonant frequency.

  In the optical deflector of the present invention, the longitudinal direction of the elastic support member and the longitudinal direction of the vibrating beam are arranged substantially orthogonally to each other, and the other end of the vibrating beam is fixed to the fixed base. The mirror beam and the pair of elastic support members are cantilevered with respect to the fixed base.

The optical deflector of the present invention includes a movable frame, a mirror portion having a light reflecting surface, a pair of first elastic support members that swingably support the mirror portion, and one end connected to the movable frame. A first vibrating beam having the other end connected to the first elastic support member and having a piezoelectric member fixed to the beam-shaped member,
Furthermore, a fixed base, a pair of second elastic support members that swingably support the movable frame, one end connected to the fixed base, the other end connected to the second elastic support member, and a beam A plurality of second vibrating beams each having a piezoelectric member fixed to the shaped member,
The first vibrating beam generates an torsional deformation in the first elastic support member by applying an alternating voltage, and causes the mirror portion to rotate and vibrate in a first direction at a first desired resonance frequency. A first drive beam and a first frequency adjusting beam that adjusts the resonance frequency by applying stress to the first elastic support member by applying a DC voltage;
The second vibrating beam generates an torsional deformation in the second elastic support member by applying an AC voltage, rotationally vibrates the movable frame at a second desired resonance frequency, and A second drive beam that is rotated and vibrated in a second direction, and a second frequency adjustment beam that adjusts the resonance frequency by applying a DC voltage to apply stress to the second elastic support member. It is characterized by being. Further, the frequency adjusting beam is characterized by only one of the first frequency adjusting beam and the second frequency adjusting beam.

  Further, an optical scanning device of the present invention includes a light source, an optical deflector configured as described above that deflects a light beam from the light source, and an imaging optical system that forms an image of the deflected light beam in a spot shape on a scanning surface. It is characterized by providing.

  The optical scanning device of the present invention includes an optical scanning device having the above-described configuration, a photosensitive member that forms a latent image by scanning a light beam, a developing unit that visualizes the latent image with toner, and a toner image that is recorded on recording paper. And transfer means for transferring to the surface.

  The image forming apparatus of the present invention includes a light source, a modulator that modulates a light beam from the light source according to an image signal, a collimating optical system that makes the light beam substantially parallel light, and the substantially parallel light. And an optical deflector configured as described above to deflect the projected light beam and project it onto the projection surface.

  According to the optical deflector of the present invention, the frequency adjustment beam is provided integrally with the drive beam, and the stress is applied to the elastic support member by the frequency adjustment beam, whereby the resonance frequency fluctuation can be adjusted in a wide range. It becomes possible. In addition to the frequency adjustment beam, the drive beam cantileverly supports the mirror part and a pair of elastic support members that swingably support the mirror part with respect to the fixed base. Let you get a large rotation amplitude.

Therefore, by using the optical deflector of the present invention, a stable optical scanning device with good characteristics can be provided, and by using the optical scanning device for an optical writing unit, an image forming device with good performance can be provided. . Furthermore, it is possible to provide an image projection apparatus that uses the optical deflector according to the present invention and has low power consumption and capable of wide angle projection.
In addition, the further structure and effect of the optical deflector of this invention will become clear by description of embodiment mentioned later.

It is a perspective view of the optical deflector of Example 1 of this invention. It is a top view of the optical deflector of FIG. It is a figure explaining the structure of the drive beam of the optical deflector of FIG. It is a figure which shows the frequency response characteristic of the rotation amplitude of the mirror part of the optical deflector of FIG. It is a figure which shows two types of natural vibration mode shapes of the mirror part of the optical deflector of FIG. 3 is a diagram illustrating an equivalent model of Example 1. FIG. It is a figure which shows the resonant frequency dispersion | variation of the some sample of Example 1. FIG. It is a figure which shows the relationship between the environmental temperature of Example 1, and a resonant frequency. It is a figure explaining the function of the frequency adjustment beam in Example 1. FIG. It is a figure explaining the function of the frequency adjustment beam in Example 1 similarly. 2 is a diagram illustrating a simplified model of Example 1. FIG. It is a figure which shows the relationship between the stress which acts on an elastic support member, and a resonant frequency. It is a figure which shows the specific example of the resonance frequency adjustment in Example 1. FIG. It is a perspective view of the optical deflector of Example 2 of this invention. It is a top view of the optical deflector of FIG. It is a figure which shows the frequency response characteristic of the rotation amplitude of the mirror part of the optical deflector of FIG. It is a figure which shows two types of natural vibration mode shapes of the mirror part of the optical deflector of FIG. It is a figure explaining the relationship between the bending deformation of the drive beam of the optical deflector of FIG. 14, and rotation of a mirror part. It is a perspective view of the optical deflector of Example 3 of this invention. It is a figure explaining the function of the 2nd frequency adjustment beam in Example 3. FIG. It is a figure explaining the function of the 2nd frequency adjustment beam in Example 3 similarly. It is a whole block diagram of an example of the optical scanning device using the optical deflector of this invention. It is a figure which shows the connection of the optical deflector and drive means of the optical apparatus of FIG. It is a whole block diagram of an example of the image forming apparatus which mounted the optical scanning device of FIG. 22 as an optical writing unit. 1 is an overall perspective view of an example of an image forming apparatus using an optical deflector of the present invention. FIG. 26 is a schematic configuration diagram illustrating the image projection apparatus of FIG. 25 including a drive system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall perspective view of a first embodiment of an optical deflector according to the present invention, and FIG. 2 is a plan view thereof. 1 and 2, reference numeral 10 denotes a mirror portion having a reflecting surface for reflecting light, and a pair of elastic support members (torsion bar springs) that support the mirror portion in a swingable manner at both ends of the mirror portion 10. ) 20 is connected. A pair of beam-like members 31 whose longitudinal direction is substantially perpendicular to the longitudinal direction of the elastic support member 20 are connected to the ends of the pair of elastic support members 20 opposite to the mirror portion 10, respectively. The other end of the beam-shaped member 31 is connected to the fixed base 60.

  The pair of beam-like members 31 protrude from the fixed base 60 in the same direction, and are disposed only on one side of each elastic support member 20. The pair of beam-like members 31, the mirror portion 10, and the pair of elastic supports 20 Is cantilevered with respect to the fixed base 60.

  Piezoelectric materials 32 are laminated on one surface of each beam-shaped member 31, and the beam-shaped member 31 and the piezoelectric material 32 form a driving beam 30 having a unimorph structure with a flat plate-like short rail shape. Further, a beam-like member 41 is extended and provided integrally with each beam-like member 31 so as not to be connected to the elastic support member 20, and a piezoelectric material 42 is similarly laminated on one surface of the beam-like member 41. The beam-shaped member 41 and the piezoelectric member 42 form a frequency adjusting beam 40 having a flat short rail-like unimorph structure.

  Here, a configuration in which the driving beam 30 and the frequency adjusting beam 40 are combined is referred to as a vibrating beam 50. That is, the vibrating beam 50 includes a portion of the driving beam 30 connected to the elastic support member 20 and a portion of the frequency adjustment beam 40 not connected to the elastic support member 20.

  For example, the mirror part 10, the elastic support member 20, the drive beam 30, the frequency adjustment beam 40, etc. are integrally formed by processing by a MEMS (micro electro mechanical systems) process. The mirror unit 10 forms a reflective surface by forming a thin film of metal such as aluminum or gold on the surface of a silicon substrate.

  Here, a detailed configuration of the drive beam 30 will be described with reference to FIG. 3A and 3B are schematic views showing the driving beam 30 and the fixed base 60 in the vicinity thereof in an enlarged manner. FIG. 3A is a plan view before being covered with an insulating layer, and FIG. 3B is a plan view after being covered with an insulating layer. (C) is sectional drawing of the AA 'line | wire part of (b). Since the frequency adjustment beam 40 has the same configuration, the illustration is omitted.

  As shown in FIG. 3, the drive beam 30 is formed on the beam-shaped member 31 that protrudes from the fixed base 60, on the adhesive layer 33, the lower electrode 35, the piezoelectric material (piezoelectric member) 32, the upper electrode 34, and the insulation. The layers 36 are formed by sputtering and stacked in this order, and are etched so that only necessary portions such as land portions 37 and 38 remain. The material of the adhesive layer 33 is titanium (Ti), the upper electrode 34 and the lower electrode 35 are platinum (Pt), and the piezoelectric material 32 is lead zirconate titanate (PZT).

  When wiring is drawn from the land portions 37 and 38 and a voltage is applied between the upper electrode 34 and the lower electrode 35, the piezoelectric material 32 expands and contracts in the in-plane direction on the surface of the beam-shaped member 31 due to its electrostrictive characteristics. The drive beam 30 as a whole is bent and deformed. For each drive beam 30, each drive beam 30 is bent and deformed in the same direction by applying an in-phase voltage to the piezoelectric member 32. The waveform of the voltage applied to the piezoelectric member 32 of each drive beam 30 may be either a pulse wave or a sine wave.

  Returning to FIG. 1 and FIG. 2, the longitudinal directions of the pair of elastic support members (torsion bar springs) 20 and the pair of drive beams 30 are arranged so as to be substantially orthogonal to each other. Since the vertical vibration at the tip of the driving beam 30 works perpendicularly to the torsional central axis of the elastic support member 20, the bending vibration of the driving beam 30 is efficiently converted into rotational vibration (torsional vibration) of the elastic support member 20, The mirror unit 10 is greatly rotated and vibrated. In addition, since the pair of drive beams 30 has a configuration in which the pair of elastic support members 20 and the mirror unit 10 are cantilevered, the tips of the drive beams 30 can freely vibrate, and the mirror unit 10 is larger. Angular vibration can be obtained. Furthermore, since the beam-shaped member 31 is disposed only on one side of the elastic support member 20, it can be reduced in size. The function of the frequency adjustment beam 40 will be described later.

  FIG. 4 shows frequency response characteristics of the amplitude of the rotation angle of the mirror unit 10 with respect to the voltage applied to the piezoelectric member 32 of the drive beam 30 in the optical deflector of the present embodiment. In FIG. 4, a and b are resonance points, but the mirror unit 10 shows different natural vibration mode shapes in a and b. Here, the natural vibration mode shape at the resonance point a is referred to as mode 1, and the natural vibration mode at the resonance point b is referred to as mode 2.

  FIG. 5 shows the natural vibration mode shapes (mode 1 and mode 2) of the mirror unit 10 at the resonance points a and b in the frequency response characteristics of FIG. As shown in FIG. 5A, in mode 1, bending deformation of the elastic support member 20 occurs, and the entire mirror portion 10 changes in the Z direction in the drawing. On the other hand, in mode 2, as shown in FIG. 5 (b), there is almost no bending deformation of the elastic support member 20, the elastic support member 20 is largely twisted, and the mirror portion 10 rotates greatly in the vicinity of the mirror center. In the optical deflector, it is necessary to use the frequency in the natural vibration mode of mode 2 because it is necessary to prevent fluctuation in the Z direction of the entire mirror unit and rotate it near the center of the mirror unit 10.

  Thus, by applying an applied voltage to the piezoelectric member 32 of the drive beam 30 at the natural frequency of mode 2, the mirror unit 10 can obtain a large angular amplitude, and the entire mirror unit 10 varies in the Z direction. Can be prevented. Specifically, the shape of the elastic support member 20 is determined from the mirror part shape (mass) and the resonance frequency, and the natural frequency of the primary bending deformation mode of the drive beam 30 is the primary torsional deformation of the elastic support member 20. It is set so as to substantially match the natural frequency of the mode. By doing so, the mirror unit 10 vibrates with a large angular amplitude, and the occurrence of fluctuations in the Z direction is prevented.

  As described above, the waveform of the voltage applied to the piezoelectric member 32 of each drive beam 30 may be either a pulse waveform or a wave shape such as a sine wave, and the frequency may be in the vicinity of the natural frequency of mode 1. That's fine.

  In this embodiment, the piezoelectric material is formed by sputtering together with the lower electrode and the upper electrode (FIG. 3). The piezoelectric material is a bulk material cut into a predetermined size and attached with an adhesive. It may be attached, or may be formed by an aerosol deposition method (AD method). The drive beam has a unimorph structure in which the piezoelectric material is arranged on one side of the beam-like member, but may have a bimorph structure in which the piezoelectric material is arranged on both sides of the beam-like member. This is the same in the following embodiments.

  Next, the function of the frequency adjusting beam 40 will be described in detail. First, the fluctuation factors of the resonance frequency will be described. There are two main causes of fluctuations in the resonance frequency: dimensional variation and environmental temperature change.

  First, the dimensional variation will be considered. In general, variations in dimensions occur due to the influence of the manufacturing process. FIG. 6 is a diagram showing an equivalent model of the optical deflector of the first embodiment shown in FIG. Now, as shown in FIG. 6, when a resonant vibrating body composed of a pair of elastic support members 20 and a mirror portion 10 is considered, the resonant frequency f is approximately

Given in. Here, K is the elastic support member spring constant, and I is the mirror moment of inertia. The spring constant K varies greatly depending on the dimensions of the elastic support member 20. As a result, the resonance frequency f varies greatly.

FIG. 7 shows the result of measuring the resonance frequency at a constant environmental temperature for several samples. FIG. 7 shows that the resonance frequency varies depending on the sample.

Next, the environmental temperature change will be considered. Here, as shown in FIG. 6, a resonant vibrating body composed of a pair of elastic support members 20 and a mirror unit 10 is considered.
Now, if E ₀ is the Young's modulus at a temperature of 0 ° and α is the Young's modulus temperature coefficient, the Young's modulus E at the temperature f is given by equation (2).
E = E ₀ (1-αt) (2)
The spring constant K is a product E of a constant K ′ determined by the spring shape and Young's modulus, and is given by the following equation (3).
K = K '* E (3)
From the equations (2) and (3), the spring constant K _t at the temperature _t is as shown in the equation (4).
K _t = K ′ * E = K ′ * E ₀ (1-αt) (4)
Therefore, the resonance frequency ft at the temperature t is obtained from the equations (1) and (4).

Given in. From equation (5), the resonance frequency decreases as the temperature increases.

  FIG. 8 shows the result of measuring the resonance frequency of the optical deflector of FIG. 1 while changing the environmental temperature. FIG. 8 shows that the resonance frequency decreases as the environmental temperature increases.

  Returning to FIG. 1, each frequency adjusting beam 40 applies a positive or negative DC voltage to the piezoelectric member 42 to apply a tensile or compressive stress to the pair of elastic support members 20, thereby causing a resonance frequency. It works to adjust. Hereinafter, the function of the frequency adjusting beam 40 will be described in detail.

FIG. 9 is an operation explanatory diagram when a positive voltage is applied to the piezoelectric member 42 of the frequency adjusting beam 40 in the configuration of FIG. It is assumed that the piezoelectric member 42 is polarized in the arrow 1 direction. When a positive voltage is applied to the piezoelectric member 42, the piezoelectric member 42 extends in the direction of the arrow 2. Thereby, the beam-like member 41 of the frequency adjusting beam 40 is deformed in the direction of the arrow 3. At this time, if the force generated at the end of the frequency adjusting beam 40 is F, and the distance from the approximate bending center of the frequency adjusting beam 40 is L, the bending moment M acting on the elastic support member 20 is
M = F * L (6)
Given in. Due to this bending moment M, a compressive stress acts on the elastic support member 20.

FIG. 10 is an operation explanatory diagram when a negative voltage is applied to the piezoelectric member 42 of the frequency adjusting beam 40 in the configuration of FIG. When a negative voltage is applied to the piezoelectric member 42, the piezoelectric member 42 contracts in the direction of the arrow 4. As a result, the beam-shaped member 41 of the frequency adjusting beam 40 is warped in the direction of the arrow 5. At this time, if the force generated at the end of the frequency adjusting beam 40 is F ′ and the distance from the approximate bending center of the frequency adjusting beam 40 is L, the bending moment M ′ acting on the elastic support member 20 is
M '= F' * L (7)
Given in. Due to this bending moment M ′, a tensile stress acts on the elastic support member 20.

  The relationship between the stress acting on the elastic support member 20 and the resonance frequency is as follows. As shown in FIG. 11, the elastic support member 20 is fixed at both ends, and assuming that uniform initial stress acts in the longitudinal direction, the change in the resonance frequency when compressive stress and tensile stress are applied to the elastic support member 20. A simulation was performed. FIG. 12 shows the simulation result. FIG. 12 shows that when a tensile stress acts on the elastic support member 20, the resonance frequency increases in proportion to the acting stress. On the other hand, when compressive stress acts on the elastic support member 20, it can be seen that the resonance frequency decreases in proportion to the acting stress. In this way, the resonance frequency can be changed by generating a stress in the elastic support member 20.

  By utilizing the relationship between the stress acting on the elastic support member 20 and the resonance frequency, a positive or negative DC voltage is applied to the piezoelectric member 42 constituting the frequency adjusting beam 40, and the elastic support member 20 is subjected to compression or tension stress. To adjust the resonance frequency.

  FIG. 13 shows a specific example of resonance frequency adjustment. In FIG. 13, A indicates the required frequency characteristics, and the resonance frequency is 28.5 KHz. B shows the frequency characteristics of a sample in which the resonance frequency is shifted by -10 Hz with respect to this resonance frequency of 28.5 KHz. On the other hand, C shows the frequency characteristic of a sample in which the resonance frequency is shifted by +10 Hz with respect to the resonance frequency of 28.5 KHz. For these two samples, a DC voltage is applied to the piezoelectric member 42 of the frequency adjusting beam 40, an AC voltage is applied to the piezoelectric member 32 of the drive beam 30, and the frequency of the AC voltage applied to the piezoelectric member 32 is set. The frequency characteristics were measured while changing. B ′ shows the frequency characteristics when a −50 V DC voltage is applied to the B sample, and it can be seen that the resonance frequency increases. On the other hand, C 'shows the frequency characteristics when + 50V DC voltage is applied to sample C, and it can be seen that the resonance frequency decreases. As a result, in both samples (b) and (c), by changing the DC voltage applied to the piezoelectric member of the frequency adjusting beam 40, it becomes possible to approximate the frequency characteristics of A.

  FIG. 14 is an overall perspective view of a second embodiment of the optical deflector of the present invention, and FIG. 15 is a plan view. 14 and 15, the same parts as those in FIGS. 1 and 2 are given the same reference numerals.

  1 and FIG. 2, the center (center of gravity) of the mirror portion 10 is made to coincide with the central axis of the pair of elastic support members 20, but in this embodiment, as shown in FIG. Further, the center (center of gravity) of the mirror portion 10 is offset by a distance ΔS with respect to the pair of elastic support members 20 in a direction approaching the connection portion between the vibrating beam 50 and the fixed base 60. By doing so, compared to the case of the first embodiment, the mirror unit 10 can be further rotationally oscillated using the deflection deformation of the pair of drive beams 40. Other configurations, operations, and effects are the same as those in the first embodiment.

  FIG. 16 shows the frequency response characteristics of the rotation angle amplitude of the mirror unit 10 with respect to the voltage applied to the piezoelectric member 31 of the driving beam 30 in the case where the center of gravity of the mirror unit 10 of this embodiment is offset (frequency adjusting beam). 40 is inoperative). FIG. 17 shows the natural vibration mode shapes (mode 1 and mode 2) of the mirror unit 10 at the resonance points a and b in the frequency response characteristics of FIG.

  Also in this embodiment, by applying an applied voltage to the piezoelectric member 31 of the drive beam 30b at the natural frequency of mode 2, the mirror unit 10 can obtain a large angular amplitude, and the entire mirror unit 10 has a Z direction. Fluctuations can be prevented. Moreover, compared to the case of the first embodiment, the mirror unit 10 can obtain a larger angular amplitude.

  FIG. 18 shows the relationship between the bending deformation of the driving beam and the rotation of the mirror part in the mode 2 of this embodiment. In mode 2 in which the elastic support member 20 is twisted, when the distance ΔS between the connection part a of the elastic support member 20 and the rotation center b of the mirror part 10 and the rotation angle of the mirror part 10 are θ, the mirror of the drive beam 30 A configuration in which the rotation center b of the mirror unit 10 does not change in the Z direction when the mirror unit 10 rotates by setting the deflection deformation c in the direction perpendicular to the reflecting surface (Z direction) to be ΔS · sin θ. It can be. Further, since the center of rotation of the mirror unit 10 is close to the center of gravity O of the mirror unit 10, the moment of inertia is reduced and the natural frequency can be increased. That is, higher speed driving is possible.

  The center of gravity of the mirror unit 10 is the center of gravity of the entire rotating unit supported by the pair of elastic support members 20, and the center of gravity may be offset including the rib structure on the back surface of the mirror.

  FIG. 19 shows an overall perspective view of Embodiment 3 of the optical deflector of the present invention. The previous embodiments 1 and 2 were configured to deflect light in one axis direction (single axis drive), but this embodiment was extended to a configuration that deflects light in two axes direction (two axis drive). is there.

  In FIG. 19, reference numeral 10 denotes a mirror part having a reflecting surface for reflecting light, and a pair of first elastic support members 120 that support the mirror part 10 so as to be swingable are connected to both sides of the mirror part 10. Has been. At the ends of the pair of first elastic support members 120 opposite to the mirror portion 10, the first vibrating beam is set with the direction substantially perpendicular to the longitudinal direction of the first elastic support member 120 as the longitudinal direction. 150 is connected. The other ends of the pair of first vibrating beams 150 are fixed to a frame-shaped movable frame having a hole in the center. That is, the pair of first vibrating beams 150 are respectively connected to the first elastic support members 120 so as to protrude in the same direction from one side inside the movable frame 160, and the pair of first elastic support members 120. The mirror unit 10 and the pair of first elastic support members 120 are cantilevered with respect to the movable frame 160 with the pair of first vibrating beams 150 disposed only on one side.

  The pair of first vibrating beams 150 includes a portion of the driving beam 130 connected to the first elastic support member 120 and a portion of the frequency adjustment beam 140 not connected to the first elastic support member 120, respectively. Become. Each drive beam 130 is formed by laminating a piezoelectric material on one surface of a beam-like member to form a flat strip-like unimorph structure. Similarly, each frequency adjusting beam 140 is formed by laminating a piezoelectric material on one side of the beam-like member to form a flat strip-like unimorph structure. These configurations are the same as those in the first embodiment.

  Further, in FIG. 19, a pair of second elastic support members 220 are connected to both sides of the movable frame 160 so as to be orthogonal to the pair of first elastic support members 120 and swingably support the movable frame 160. ing. Two ends of the pair of second elastic support members 220 on the side opposite to the movable frame 160 are set to have a longitudinal direction that is substantially perpendicular to the longitudinal direction of the second elastic support member 220. The second drive beams 250 a and 250 b are connected, and the other ends of the second drive beams 250 a and 250 are connected to the fixed base 260.

  The second vibrating beams 250 a and 250 b are also connected to the second elastic support member 220 and the second drive beams 230 a and 230 b are connected to the second elastic support member 220 and the second elastic support member 220 is not connected to the second elastic support member 220. It consists of the frequency adjusting beams 230a and 230b. The second drive beams 230a and 230b are arranged substantially orthogonally and symmetrically with respect to the second elastic support member 220, respectively, one end is connected to the second elastic support member 220, and the other end is fixed. A piezoelectric material is laminated on one side of a pair of beam members connected to the base 260 to form a flat strip-like unimorph structure. The second drive beams 230a and 230b are referred to as bridge drive beams. The second frequency adjusting beams 240a and 240b extend in a direction orthogonal to the second driving beams 230a and 230b in the vicinity of the connection point between the second driving beams 230a and 230b and the second elastic support member 220, respectively. Connecting members 270a and 270b are provided, and a piezoelectric material is laminated on one side of a plurality of beam members, one end of which is connected to the connecting members 270a and 270b and the other end is connected to a fixed base. Forming. Further, the pair of second elastic support members 220 are connected to the fixed base 260 by extending in the orthogonal direction from the coupling points with the second drive beams 230a and 230b, respectively.

  In the present embodiment, the first drive beam 130 vibrates the first elastic support member 120 to rotate the mirror portion 10 around the axis of the first elastic support member 120, and the second drive beam 130. (Bridge driving beam) The movable frame 160 is rotated around the axis of the second elastic support member 220 by applying vibration to the second elastic support member 220 by the bridge driving beams 230a and 230b. Here, the natural frequencies of the vibration modes in the first rotation direction around the axis of the first elastic support member 120 and the second rotation direction around the axis of the second elastic support member 220 are made different from each other. By driving the first driving beam 130 and the second driving beams (bridge driving beams) 230a and 230b at a frequency, the mirror unit 10 can be rotated greatly in the biaxial direction. The second drive beams 230a and 230b form a bridge drive beam, and the second elastic support member 220 is connected to the fixed base 260 by extending in the orthogonal direction from the connection point with the bridge drive beam. Biaxial vibration can be stabilized.

  The natural frequencies of the vibration modes in the first rotation direction around the axis of the first elastic support member 120 and the second rotation direction around the axis of the second elastic support member 220 are made different from each other, and the respective frequency components are changed. By driving the first driving beam 130 and the second driving beams (bridge driving beams) 230a and 230b with the included signal, the mirror unit 10 can be greatly rotated in the biaxial direction.

Hereinafter, the resonance frequency adjustment in the second rotation direction around the axis of the second elastic support member 220 by the second frequency adjustment beams 240a and 240b will be described. The resonance frequency adjustment in the first rotation direction around the axis of the first elastic support member 120 by the first frequency adjustment beam 140 is the same as that in the first embodiment, and thus the description thereof is omitted.
An AC voltage having a predetermined frequency is applied to the second drive beams (bridge drive beams) 230a and 230b, but a DC voltage is applied to the second frequency adjustment beams 240a and 240b.

FIG. 20 is an operation explanatory diagram when a positive voltage is applied to the second frequency adjustment beams 240a and 240b in the configuration of FIG. When a positive voltage is applied to the second frequency adjusting beams 240a and 240b, the piezoelectric members extend in the direction of arrow 1, respectively. As a result, the second frequency adjustment beams 240a and 240b are deformed in the direction of the arrow 2, respectively. At this time, when the force generated at the ends of the second frequency adjusting beams 240a and 240b is F and the distance from the approximate bending center of the second frequency adjusting beams 240a and 240b is L, the second The bending moment M acting on the elastic support member 220 is
M = F * L (8)
Given in. This bending moment M is generated in the direction of arrow 3, and the second elastic support member 220 is contracted in the direction of arrow 4. That is, due to the bending moment M, compressive stress acts on the second elastic support member 220.

FIG. 21 is an operation explanatory diagram when a negative voltage is applied to the second frequency adjustment beams 240a and 240b in the configuration of FIG. When a negative voltage is applied to the second frequency adjustment beams 240a and 240b, the piezoelectric members contract in the direction of arrow 5, respectively. As a result, the second frequency adjustment beams 240a and 240b are warped and deformed in the direction of the arrow 6, respectively. At this time, if the force generated at the ends of the second frequency adjusting beams 240a and 240b is F ′, and the distance from the approximate bending center of the second frequency adjusting beams 240a and 240b is L, the second The bending moment M ′ acting on the elastic support member 220 is
M '= F' * L (9)
Given in. This bending moment M ′ is generated in the direction of arrow 7, and the second elastic support member 220 extends in the direction of arrow 8. That is, a tensile stress acts on the second elastic support member 220 due to the bending moment M ′.

  From the relationship between the resonance frequency and the stress shown in FIG. 12, when a tensile stress acts on the second elastic support member 220, the resonance frequency increases in proportion to the acting stress. When compressive stress acts on the member 220, the resonance frequency decreases in proportion to the acting stress. That is, by generating a stress in the second elastic support member 220, the resonance frequency in the second rotation direction around the axis of the second elastic support member 220 can be adjusted. Specifically, as shown in FIG. 13, if a negative DC voltage is applied to the second frequency adjustment beams 240a and 240b, the resonance frequency can be increased, and if a positive DC voltage is applied, The resonance frequency can be reduced.

  As described above, with the configuration shown in FIG. 19, the mirror unit 10 can be greatly rotated in the biaxial direction, and at the same time, the resonant frequencies in the biaxial direction can be adjusted.

  In the configuration of FIG. 19, the frequency adjustment beam may be only one of the first frequency adjustment beam 140 or the second frequency adjustment beams 240a and 240b. For example, when the resonance frequency shift is only in the first rotation direction around the axis of the first elastic support member 120, the frequency adjustment beam may be only the first frequency adjustment beam 140. When the resonance frequency shift is only in the second rotation direction around the axis of the second elastic support member 220, the frequency adjustment beams need only be the second frequency adjustment beams 240a and 240b. This simplifies the configuration of the biaxial drive light deflector compared to the configuration of FIG.

  Further, the configuration of FIG. 19 is changed, and the plurality of first vibrating beams 150 are arranged substantially orthogonally and symmetrically with respect to the first elastic support member 120 in the same manner as the second vibrating beam 250. Thus, the first drive beam 130 may be a bridge drive beam. Also in the uniaxially driven optical deflectors of the first and second embodiments, the plurality of vibrating beams 50 are arranged substantially orthogonally and symmetrically with respect to the elastic support member 20, respectively. Can be a bridge drive beam. The configuration of the frequency adjustment beam is the same. The optical deflector of the present invention includes such a configuration.

  This embodiment provides an optical scanning device as an optical writing unit of an image forming apparatus using an optical deflector that deflects light in one axial direction of the first and second embodiments.

  FIG. 22 is an overall configuration diagram of the optical scanning device of the present embodiment, and FIG. 23 is a connection diagram of an optical deflector used in the optical scanning device and driving means.

  In FIG. 22, the laser light from the laser element 1020 passes through the collimator lens system 1021 and is then deflected by the optical deflector 1022. As this optical deflector 1022, the optical deflector having any one of the configurations of the first to fifth embodiments is used. The laser beam deflected by the optical deflector 1022 is then applied to a beam scanning surface 1022 such as a photosensitive drum through a scanning optical system 1023 including a first lens 1023a, a second lens 1023b, and a reflection mirror 1023c.

  As shown in FIG. 23, the optical deflector 1022 is electrically connected to the driving means 1024. The driving unit 1024 applies a driving voltage between the lower electrode and the upper electrode of the optical deflector 1022. As a result, the mirror portion of the optical deflector 1022 rotates to deflect the laser light, and the beam scanning surface 1022 is optically scanned.

  As described above, the optical scanning device using the optical deflector according to the present invention is optimal as a constituent member of an optical writing unit for an image forming apparatus such as a photographic printing type printer or a copying machine.

  This embodiment provides an image forming apparatus in which the optical scanning device according to the fourth embodiment is mounted as a constituent member of an optical writing unit.

  FIG. 24 shows an overall configuration diagram of an example of the image forming apparatus of this embodiment. In FIG. 24, reference numeral 1001 denotes an optical writing unit, which emits a laser beam to a surface to be scanned and writes an image. Reference numeral 1002 denotes a photosensitive drum as an image carrier that provides a surface to be scanned as an object to be scanned by the optical writing unit 1001.

  The optical writing unit 1001 scans the surface (scanned surface) of the photosensitive drum 1002 in the axial direction of the photosensitive drum 1002 with one or a plurality of laser beams modulated by the recording signal. The photosensitive drum 1002 is rotationally driven in the direction of an arrow 1003, and an optical latent image is formed on the surface charged by the charging unit 1004 by optical scanning by the optical writing unit 1001. The electrostatic latent image is visualized as a toner image by the developing unit 1005, and the toner image is transferred to the recording paper 1007 by the transfer unit 1006. The transferred toner image is fixed on the recording paper 1007 by the fixing unit 1008. Residual toner is removed by the cleaning unit 1009 from the surface portion of the photosensitive drum that has passed the transfer unit 1006 facing portion of the photosensitive drum 1002.

  A configuration using a belt-like photoconductor in place of the photoconductor drum 1002 is also possible. Further, the toner image may be temporarily transferred to a transfer medium other than the recording paper, and the toner image may be transferred from the transfer medium to the recording paper and fixed.

  The optical writing unit 1001 includes a light source unit 1020 as a laser element that emits one or a plurality of laser beams modulated by a recording signal, a light source driving unit 1500 that modulates a laser beam, and the uniaxial of the present invention described so far. An optical deflector 1002 that deflects the laser beam in the direction, and a connection for imaging the laser beam (light beam) modulated by the recording signal from the light source unit 1020 on the mirror surface of the mirror substrate of the optical deflector 1022. An image optical system 1021 and a scanning optical system 1023 that is a means for forming an image of one or a plurality of laser beams reflected and deflected by a mirror surface on the surface (scanned surface) of the photosensitive drum 1002 Is done. The optical deflector 1022 is incorporated in the optical writing unit 1001 in a form mounted on a circuit board 1025 together with an integrated circuit (driving means) 1024 for driving the optical deflector 1022.

  The optical deflector 1022 consumes less power for driving than the conventional rotary polygon mirror, which is advantageous for power saving of the image forming apparatus. Further, since the wind noise during vibration of the mirror substrate of the optical deflector 1022 is smaller than that of the rotary polygon mirror, it is advantageous for improving the quietness of the image forming apparatus. Furthermore, the optical deflector 1022 requires much less installation space than the rotary polygon mirror, and also has a small amount of heat generation, so that it can be easily downsized, and therefore advantageous for downsizing the image forming apparatus. is there.

  Note that the conveyance mechanism of the recording paper 1007, the driving mechanism of the photosensitive drum 1002, the control means such as the developing means 1005 and the transfer means 1006, the driving system of the light source unit 1020, and the like may be the same as those in the conventional image forming apparatus. Is omitted.

  The present embodiment provides an image projection apparatus equipped with an optical deflector that deflects light in the biaxial direction as in the third embodiment.

  FIG. 25 shows an overall configuration diagram of the image projection apparatus of the present embodiment. In FIG. 25, laser light sources 2001-R, 2001-G, and 2001-B that emit laser beams having three different wavelengths of red (R), green (G), and blue (B) are attached to a housing 2000. In the vicinity of the emission ends of the laser light sources 2001-R, 2001-G, 2001-B, a condenser lens 2002 that condenses the emitted light from the laser light sources 2001-R, 2001-G, 2001-B into substantially parallel light. -R, 2002, 002-B are arranged. The R, G, and B laser beams that are substantially parallel by the condenser lenses 2002-R, 2002, and 002-B pass through the mirror 2003 and the half mirror 2004, and are combined by the combining prism 2005. Incident on the mirror surface. As the optical deflector 2006, an optical deflector (two-dimensional reflection angle variable mirror) configured to deflect light in two-axis directions as in the seventh and eighth embodiments is used. The combined laser light incident on the mirror surface of the optical deflector 2006 is two-dimensionally deflected and scanned by the optical deflector 2006 and projected onto the projection surface to project an image.

  FIG. 26 is a schematic configuration diagram including the control system of the image projection apparatus of the present embodiment. In FIG. 26, the three-wavelength laser light source and the condenser lens are shown together, and the mirror, the half mirror, and the combining prism are omitted.

  The image generation unit 2011 generates an image signal according to the image information, and the image signal is sent to the light source drive circuit 2013 via the modulator 2012, and the image synchronization signal is sent to the scanner drive circuit 2014. The scanner drive circuit 2014 supplies a drive signal to the optical deflector 2006 according to the image synchronization signal. By this drive signal, the mirror unit 10 of the optical deflector 2006 resonates and vibrates in two orthogonal directions with an amplitude of a predetermined angle (for example, about 10 deg), and the incident laser light is two-dimensionally deflected and scanned. On the other hand, the intensity of the laser light emitted from the laser light source 2001 is modulated by the light source driving circuit 2013 in accordance with the timing of the two-dimensional deflection scanning of the optical deflector 2006, and thereby a two-dimensional image is projected on the projection surface 2007. Information is projected. Intensity modulation may modulate the pulse width or the amplitude. The modulator 2012 performs pulse width modulation or amplitude modulation on the image signal, and modulates the modulated signal into a current that can drive the laser light source 2001 by the light source driving circuit 2013 to drive the laser light source 2001.

  Here, a rotating scanning mirror such as a polygon mirror can be used as the light deflecting unit, but the optical deflector (two-dimensional reflection angle variable mirror) 2006 having the configuration of the seventh and eighth embodiments of the present invention is rotated. Since power consumption for driving is smaller than that of the scanning mirror, it is advantageous for power saving of the image projection apparatus. Further, since the wind noise during vibration of the mirror substrate of the optical deflector 2006 is smaller than that of the rotating scanning mirror, it is advantageous for improving the quietness of the image projection apparatus. Furthermore, the optical deflector 2006 requires much less installation space than the rotary scanning mirror and has a small amount of heat generation, so it can be easily downsized, and is therefore advantageous for downsizing the image projection apparatus. is there.

DESCRIPTION OF SYMBOLS 10 Mirror part 20 Elastic support member 30 Driving beam 31 Beam-shaped member 32 Piezoelectric member 40 Frequency adjustment beam 41 Beam-shaped member 42 Piezoelectric member 50 Vibrating beam 60 Fixed base 120 First elastic supporting member 130 First driving beam 140 First Frequency adjusting beam 150 first vibrating beam 160 movable frame 220 second elastic support member 230a, 230b second driving beam (bridge driving beam)
240a, 240b Second frequency adjusting beam 250a, 250b Second vibrating beam 260 Fixed base 270a, 270b Connecting member

JP 2003-84226 A JP 2005-128551 A JP 2005-128147 A Japanese Patent No. 2981600

Claims (12)

A fixed base, a mirror portion having a light reflecting surface, an elastic support member that supports the mirror portion in a swingable manner, one end connected to the fixed base, and the other end connected to the elastic support member. A vibrating beam having a piezoelectric member fixed to the member;
The vibrating beam generates a torsional deformation in the elastic support member by applying an AC voltage, and rotates and vibrates the mirror portion at a desired resonance frequency, and the elastic beam by applying a DC voltage. An optical deflector comprising: a frequency adjusting beam that applies stress to a supporting member to adjust the resonance frequency.   In the vibrating beam, the drive beam is configured by a portion where the beam-shaped member is connected to the elastic support member, and the frequency adjusting beam is configured by a portion where the beam-shaped member is not connected to the elastic support member. The optical deflector according to claim 1.   The longitudinal direction of the elastic support member and the longitudinal direction of the vibrating beam are arranged substantially orthogonal to each other, both are connected, and the other end of the vibrating beam is fixed to the fixed base. The optical deflector according to claim 1 or 2, wherein the elastic support member is cantilevered with respect to the fixed base.   4. The optical deflector according to claim 3, wherein the center of gravity of the mirror portion is offset in a direction approaching the connecting portion side between the vibrating beam and the fixed base with respect to the central axis of the elastic support member. A movable frame, a mirror portion having a light reflecting surface, a pair of first elastic support members that support the mirror portion so as to be swingable, one end connected to the movable frame, and the other end the first elastic A first vibrating beam connected to the support member and having a piezoelectric member fixed to the beam-shaped member;
Furthermore, a fixed base, a pair of second elastic support members that swingably support the movable frame, one end connected to the fixed base, the other end connected to the second elastic support member, and a beam A plurality of second vibrating beams each having a piezoelectric member fixed to the shaped member,
The first vibrating beam generates an torsional deformation in the first elastic support member by applying an alternating voltage, and causes the mirror portion to rotate and vibrate in a first direction at a first desired resonance frequency. A first drive beam and a first frequency adjusting beam that adjusts the resonance frequency by applying stress to the first elastic support member by applying a DC voltage;
The second vibrating beam generates an torsional deformation in the second elastic support member by applying an AC voltage, rotationally vibrates the movable frame at a second desired resonance frequency, and A second drive beam that is rotated and vibrated in a second direction, and a second frequency adjustment beam that adjusts the resonance frequency by applying a DC voltage to apply stress to the second elastic support member. To be
An optical deflector characterized by that. A movable frame, a mirror portion having a light reflecting surface, a pair of first elastic support members that support the mirror portion so as to be swingable, one end connected to the movable frame, and the other end the first elastic A first vibrating beam connected to the support member and having a piezoelectric member fixed to the beam-shaped member;
Furthermore, a fixed base, a pair of second elastic support members that swingably support the movable frame, one end connected to the fixed base, the other end connected to the second elastic support member, and a beam A plurality of second vibrating beams each having a piezoelectric member fixed to the shaped member,
The first vibrating beam generates an torsional deformation in the first elastic support member by applying an alternating voltage, and causes the mirror portion to rotate and vibrate in a first direction at a first desired resonance frequency. A first driving beam and a frequency adjusting beam that adjusts the resonance frequency by applying a DC voltage to apply stress to the first elastic support member;
The second vibrating beam generates an torsional deformation in the second elastic support member by applying an AC voltage, rotationally vibrates the movable frame at a second desired resonance frequency, and Consists of a second drive beam that oscillates in the second direction.
An optical deflector characterized by that. A movable frame, a mirror portion having a light reflecting surface, a pair of first elastic support members that support the mirror portion so as to be swingable, one end connected to the movable frame, and the other end the first elastic A first vibrating beam connected to the support member and having a piezoelectric member fixed to the beam-shaped member;
Furthermore, a fixed base, a pair of second elastic support members that swingably support the movable frame, one end connected to the fixed base, the other end connected to the second elastic support member, and a beam A plurality of second vibrating beams each having a piezoelectric member fixed to the shaped member,
The first vibrating beam generates an torsional deformation in the first elastic support member by applying an alternating voltage, and causes the mirror portion to rotate and vibrate in a first direction at a first desired resonance frequency. Composed of a first drive beam,
The second vibrating beam generates an torsional deformation in the second elastic support member by applying an AC voltage, rotationally vibrates the movable frame at a second desired resonance frequency, and A second driving beam that is rotated and vibrated in a second direction; and a frequency adjustment beam that adjusts the resonance frequency by applying a DC voltage to apply stress to the second elastic support member.
An optical deflector characterized by that.   The second vibrating beam is substantially orthogonal to the second elastic support member and symmetrically arranged, one end is connected to the fixed base, and the other end is connected to the second elastic support member. One end is connected to a second driving beam constituting the bridge driving beam, and a connecting member extending in a direction orthogonal to the bridge driving beam in the vicinity of a connection point between the bridge driving beam and the second elastic support member, 8. The optical deflector according to claim 5, wherein the other end is composed of a frequency adjusting beam connected to a fixed base.   The optical deflector according to any one of claims 5 to 8, wherein the second elastic support member is extended and connected to a fixed base.   5. A light source, an optical deflector according to claim 1 for deflecting a light beam from the light source, and an imaging optical system for imaging the deflected light beam in a spot shape on a surface to be scanned. An optical scanning device comprising:   11. An optical scanning device according to claim 10, a photosensitive member that forms a latent image by scanning with a light beam, a developing unit that visualizes the latent image with toner, and a transfer unit that transfers the toner image to recording paper. An image forming apparatus. A light source;
A modulator that modulates a light beam from the light source according to an image signal;
A collimating optical system in which the light beam is substantially parallel light;
An image projection apparatus comprising: the light deflector according to claim 1, wherein the light beam that has been converted into substantially parallel light is deflected and projected onto a projection surface.