JP6614276B2 - Piezoelectric light deflector, optical scanning device, image forming device, and image projection device - Google Patents

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 a piezoelectric optical deflector that uses piezoelectric power. Furthermore, the present invention relates to an optical scanning device including the piezoelectric optical deflector, an image forming apparatus including the optical scanning device as an optical writing unit, and an image projecting device including the piezoelectric optical deflector as a scanning unit for a projection surface. .

  An optical deflector that deflects and scans a light beam such as a laser beam is widely used in an image forming apparatus such as a copying machine, an image projection apparatus, a laser beam printer, a barcode scanner, and the like. Conventionally, as this type of optical deflector, one using an electrostatic force, one using an electromagnetic force, one using a piezoelectric force, and the like are known.

  There are two types of optical deflectors using electrostatic force, parallel plate type and comb type, so that the comb type electrode can generate a relatively large driving force by the recent improvement of microfabrication technology. However, since a sufficient deflection angle of the light beam cannot be obtained, the drive voltage must be increased to compensate. However, if the drive voltage is increased, the power supply system components become larger, resulting in an increase in size as a whole and an increase in cost.

  Since an optical deflector using electromagnetic force has a permanent magnet disposed outside, the structure is complicated, the productivity is low, and the size reduction is difficult. Although the use of a magnetostrictive film or the like has been studied for miniaturization, there is a problem that a sufficient deflection angle cannot be obtained because the characteristics as a magnetic material are inferior. In addition, if a current is passed through the coil, extra heat is generated and power consumption increases.

  On the other hand, when the piezoelectric power is used, a relatively large driving voltage is required, but a large force can be generated with a small power. In addition, it is possible to obtain a large deformation by changing a slight distortion in the in-plane direction due to the piezoelectric force into a warp by bonding the piezoelectric material to the beam-like elastic member to form a unimorph structure or a bimorph structure. As an optical deflector (hereinafter referred to as a piezoelectric optical deflector) using this piezoelectric power, the piezoelectric drive unit has a cantilever structure, so that it is small in size and has good drive efficiency and a larger rotational amplitude. This has also been proposed (Patent Document 1).

  A piezoelectric light deflector deflects and scans a laser beam or the like by using a piezoelectric power generated by applying a voltage to a piezoelectric member and displacing a mirror portion via a driving beam. A typical material of the piezoelectric member used in this piezoelectric light deflector is lead zirconate titanate (PZT).

An object of the present invention, the piezoelectric light deflector, is to improve the stability of the ejection unperturbed.

The present invention includes a fixed base, a movable part having a mirror, an elastic support member that supports the movable part, and a drive beam that supports the elastic support member on the fixed base. And a lower electrode, a piezoelectric member , an upper electrode, and an insulating layer laminated on the beam member, one end of the drive beam is connected to the elastic support member, and the other of the drive beam The end is connected to the fixed base, the stacked upper electrode has four corners, and the two corners on the one end side are rounded, and the other end side The two corners are not rounded .

  According to the piezoelectric optical deflector of the present invention, it is possible to reduce the temporal variation of the mirror displacement amount during continuous driving.

It is a perspective view of the piezoelectric light deflector of Example 1 of the present invention. It is a top view of the piezoelectric light deflector of FIG. It is a figure explaining the structure of the drive beam of the piezoelectric optical deflector of FIG. It is a figure which shows the PE hysteresis characteristic of lead zirconate titanate (PZT). It is the figure which showed the relationship between the drive voltage of the piezoelectric optical deflector using a PZT film | membrane, and a time-dependent change of mirror displacement. It is a top view of the piezoelectric light deflector of Example 2 of the present invention. It is a perspective view of the biaxial piezoelectric light deflector of Example 3 of the present invention. It is a whole block diagram of an example of the optical scanning device using the piezoelectric optical deflector of this invention. It is the figure which showed the connection of the piezoelectric light deflector and drive means of the optical scanning device of FIG. It is a schematic block diagram of an example of the image forming apparatus which mounted the optical scanning device of FIG. 8 as an optical writing unit. It is a schematic block diagram of an example of the image projection apparatus using the piezoelectric light deflector of this invention. It is a top view of the piezoelectric optical deflector of Example 7 of this invention. It is an example of the voltage waveform applied to a piezoelectric member. It is a top view of the two-dimensional optical deflector of Example 8 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, a piezoelectric light deflector having a piezoelectric drive unit as described in Patent Document 1 having a cantilever structure is an object, but of course, the present invention is limited to such a piezoelectric light deflector. is not.

  FIG. 1 is a perspective view of the piezoelectric light deflector according to the first embodiment, and FIG. 2 is a plan view. 1 and 2, reference numeral 10 denotes a movable part, which has a mirror part 15 as a light reflecting surface for reflecting laser light or the like. Both ends of the movable part 10 are connected to torsion bars 20a, 20b as a pair of elastic support members that rotatably support the movable part 10. The ends of the torsion bars 20a, 20b opposite to the movable part 10 are connected to one ends of a pair of beam members 31a, 31b whose longitudinal direction is perpendicular to the longitudinal direction of the torsion bars 20a, 20b. Yes. The other ends of the beam members 31 a and 31 b are connected to the fixed base 40.

  The beam members 31a and 31b are provided only on one side of the torsion bars 20a and 20b, and the movable part 10 and the torsion bars 20a and 20b are cantilevered with respect to the fixed base 40 by the beam members 31a and 31b. It has become. Piezoelectric members 32a and 32b are laminated on one surface of the beam-like members 31a and 31b, and the beam-like member 31a and the piezoelectric member 32a form a drive beam 30a. The beam-like member 31b and the piezoelectric member 32b are driven. A beam 30b is formed.

  The piezoelectric members 32a and 32b have an upper electrode and a lower electrode, respectively, but only the upper electrodes 34a and 34b are shown in FIGS. Here, as will be described later, lead zirconate titanate (PZT) films are used for the piezoelectric members 32a and 32b.

  Although the drive beams 30a and 30b are entirely covered with an insulating layer (insulating film), they are omitted in FIGS.

  FIG. 3 is an enlarged schematic view showing the driving beam 30a and the fixed base 40 in the vicinity thereof. (A) is a plan view before the driving beam 30a is covered with an insulating layer, and (b) is covered with an insulating layer. A later plan view, (c) is a cross-sectional view taken along line AA ′ of (b). Since the drive beam 30b has the same configuration, the illustration is omitted.

  As shown in FIG. 3, the driving beam 30a is formed on the beam-shaped member 31a formed to protrude from the fixed base 40 in the order of an adhesive layer 33a, a lower electrode 35a, a piezoelectric member 32a, an upper electrode 34a, and an insulating layer 36a. A film is formed by sputtering and laminated. The upper electrode 34a and the lower electrode 35a are connected to the land portions 37a and 38a through wirings, respectively, and the land portions 37a and 38a are connected to an external drive circuit (not shown). The land portions 37a and 38a and the wiring are also formed by sputtering in the same manner as the upper electrode 34a and the lower electrode 35a.

  The fixed base 40 is made of silicon (Si), the adhesive layer 33a is made of titanium (Ti), the upper electrode 34a and the lower electrode 35a are made of platinum (Pt), and the piezoelectric member 32a is made of lead zirconate titanate (PZT).

  In the case of a thin film type piezoelectric optical deflector, the PZT thickness of the piezoelectric members 32a and 32b is about 2 μm. PZT has better electro-mechanical energy conversion efficiency than other piezoelectric materials, and a PZT film can be formed at low cost by a general manufacturing method such as a sputtering method or a coating formation method using a sol-gel liquid spinner. it can.

  Returning to FIG. 1, when a voltage is applied between the upper and lower electrodes of the piezoelectric members 32a and 32b, the piezoelectric members 32a and 32b expand and contract in the in-plane direction on the surfaces of the beam-like members 31a and 31b due to their electrostrictive characteristics. As a result, the drive beams 30a and 30b are bent and deformed. When the driving beams 30a and 30b are bent and deformed, torsional deformation occurs in the torsion bars 20a and 20b as elastic support members, and the movable portion 10 rotates.

  Specifically, the voltage applied to the upper / lower electrodes is a sine wave, and the drive beams 30a and 30b vibrate and vibrate. The bending vibrations of the drive beams 30a and 30b are converted into rotational vibrations (torsional vibrations) by the torsion bars 20a and 20b, and the movable part 10 is rotationally vibrated.

  In the case of the piezoelectric light deflector having the structure shown in FIG. 1, the longitudinal directions of the torsion bars 20a and 20b and the drive beams 30a and 30b are orthogonal to each other. Is efficiently converted to rotational vibration (torsional vibration), and the movable part 10 is largely rotationally oscillated. In addition, since the driving beams 30a and 30b have a configuration in which the torsion bars 20a and 20b and the movable portion 10 are cantilevered, the distal ends of the driving beams 30a and 30b can freely vibrate. Angular amplitude can be obtained. Furthermore, since the drive parts 30a and 30b are arrange | positioned only at the one side of the torsion bars 20a and 20b, size reduction is possible.

  By the way, when a voltage is applied to a ferroelectric such as PZT used for the piezoelectric members 32a and 32b of the drive beams 30a and 30b, a voltage may be generated in the ferroelectric. This phenomenon is called imprinting, and is mainly caused by the charge being injected from the electrode and moving inside the PZT to create a charge distribution. The imprint phenomenon affects the stable operation of the piezoelectric light deflector over time. Specifically, if the drive voltage is continuously applied to the piezoelectric member, the amount of displacement (rotation amount) of the mirror portion changes with time.

  Therefore, in the piezoelectric light deflector of the present embodiment, the minimum value or the maximum value of the drive voltage applied to the piezoelectric members 32a and 32b is set within a range of 0V from the coercive electric field value of PZT used for the piezoelectric members. As a result, the temporal change (amplitude temporal change) of the displacement amount of the mirror portion is reduced.

  FIG. 4 shows the results of measurement of PE hysteresis characteristics of lead zirconate titanate (PZT) used in the piezoelectric light deflector of this example. In FIG. 4, the vertical axis represents the amount of polarization (P), and the horizontal axis represents the electric field (E). PZT was manufactured by the Sorge method, and the film thickness (PZT film) was 2 μm. FIG. 4 shows that the coercive electric field value is 18.75 kV / cm-1. This is 18.75 (kV / cm <-1>) * 2 ([mu] m) = 3.75 (V) in terms of voltage.

  FIG. 5 shows the piezoelectric optical deflector of the present embodiment, in which the amplitude value of the driving voltage of the piezoelectric members 32a and 32b is kept constant at 12.5V, and the minimum value of the driving voltage is 0V, -2.50V, and -3.75V. , −5.0V (in this way, the offset amount of the drive voltage is set) and each drive voltage (FIG. 5A) and mirror unit when the piezoelectric optical deflector is operated for a long time. It is the figure which showed the relationship of amplitude variation with time (FIG.5 (b)). Here, the PZT film thickness of the piezoelectric members 32a and 32b is 2 μm as in FIG. The resonance frequency was 20 kHz, and the drive frequency was set to be the resonance frequency.

  FIG. 5 shows that when the minimum value of the drive voltage is set to −3.75 V (C case), the amplitude variation with time of the mirror portion is minimized. As described in FIG. 4, the value of 3.75 V corresponds to the coercive electric field value (voltage converted value) of PZT of the piezoelectric members 32a and 32b.

  When the minimum value of the driving voltage falls below the coercive electric field value of PZT, polarization inversion occurs. As a result, when driving for a long time, separation fatigue accumulates and the amplitude variation with time of the mirror portion increases (case D). On the other hand, when the minimum value of the drive voltage is set to 0 V or more, the imprint phenomenon proceeds, charges are accumulated in the PZT, and the amplitude variation with time of the mirror portion increases (case A).

  As described above, in the piezoelectric optical deflector of this embodiment, the minimum value of the driving voltage of the piezoelectric member is not less than the coercive electric field value of PZT so that polarization inversion does not occur, and 0 V or less so that the imprint phenomenon does not proceed. You can see that. Similarly, in the case of using the drive voltage with the polarity reversed, it is understood that the maximum value of the drive voltage may be equal to or lower than the coercive electric field value of PZT and equal to or higher than 0V. That is, it can be seen that it is preferable to set the minimum value or the maximum value of the driving voltage of the piezoelectric member within a range of 0 V from the coercive electric field value of PZT used for the piezoelectric member.

  FIG. 6 is a plan view of the piezoelectric light deflector according to the second embodiment. 6, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals. Although the overall configuration is basically the same as that of the first embodiment, in this embodiment, cuts 40a and 40b are formed at the connecting portions of the drive beams 30a and 30b and the torsion bars 20a and 20b. Specifically, the driving beams 30a and 30b are arranged so that the end portions on the movable portion 10 side of the driving beams 30a and 30b are closer to the movable portion 10 side than the end portions on the opposite side to the movable portion 10 of the torsion bars 20a and 20b. Incisions 40a and 40b are formed in the connecting portions of the torsion bars 20a and 20b.

  The torsion bars 20a and 20b have a large non-linearity as a spring characteristic. However, as the length becomes shorter, the non-linearity increases and the design becomes difficult. Further, the longer the torsion bars 20a and 20b, the larger the allowable displacement angle.

  In the present embodiment, the length of the torsion bars 20a and 20b is maintained within a desired range, and the drive beams 30a and 30b are arranged in the space-exempted portion, that is, the drive beams 30a and 30b are offset inward. As a result, the entire piezoelectric optical deflector can be further reduced in size. As a result, when the piezoelectric light deflector is manufactured by the MEMS process, the number of wafers in a single wafer increases, so that the cost can be reduced.

  Also in the piezoelectric optical deflector of the present embodiment, the minimum value or the maximum value of the drive voltage applied to the piezoelectric members of the drive beams 30a and 30b is set within a range of 0V from the coercive electric field value of PZT used for the piezoelectric members. As a result, it is possible to reduce the amplitude variation with time of the mirror unit 15.

  FIG. 7 is an overall perspective view of the piezoelectric optical deflector according to the third embodiment. The piezoelectric light deflectors described so far all deflect light in the uniaxial direction, but this embodiment is configured to deflect light in the biaxial direction.

  In FIG. 7, reference numeral 10 denotes a movable part having a mirror part as a light reflecting surface for reflecting light, and a pair of first elastic supports for rotatably supporting the movable part 10 on both sides of the movable part 10. First torsion bars 120a and 120b as members are connected. The ends of the first torsion bars 120a and 120b opposite to the movable part 10 have a pair of first drive beams 130a with the direction substantially perpendicular to the longitudinal direction of the first torsion bars 120a and 120b as the longitudinal direction. , 130b are connected. The first driving beams 130a and 130b are formed by laminating piezoelectric members on one side of the beam-like member to form a flat strip-like unimorph structure. The first drive beams 130 a and 130 b are arranged so as to protrude in the same direction from one side inside the frame-like movable frame 140 having a hole in the center, and are connected to the movable frame 140. The first drive beams 130a and 130b are disposed only on one side of the first torsion bars 120a and 120b, and the drive beams 130a and 130b connect the movable portion 10 and the first torsion bars 120a and 120b to the movable frame. 140 is cantilever-supported.

  The first drive beams 130a and 130b have upper and lower electrodes, respectively, but only the upper electrodes 134a and 134b are shown in FIG. Further, lead zirconate titanate (PZT) is used for the piezoelectric members of the first drive beams 130a and 130b.

  To both sides of the movable frame 140, a pair of torsion bars 220a and 220b as second elastic support members that rotatably support the movable frame 140 are connected. The ends of the second torsion bars 220a and 220b opposite to the movable frame 140 have a pair of second drive beams 230a and 230b with the direction substantially perpendicular to the longitudinal direction of the second torsion bars 220a and 220b as the longitudinal direction. Is connected. The second drive beams 230a and 230b are also laminated with a piezoelectric material on one side of the beam-like member to form a flat strip-like unimorph structure. The second drive beams 230 a and 230 b are arranged so as to protrude from the fixed base 240 in the same direction, and are connected to the fixed base 240. The second drive beams 230a and 230b are also arranged only on one side of the second torsion bars 220a and 220b. With the second drive beams 230a and 230b, the movable frame 140 and the second torsion bar 220a, 220b is cantilevered with respect to the fixed base 240. The second drive beams 230a and 230b also have an upper electrode and a lower electrode, respectively, but are omitted in FIG. PZT is also used for the piezoelectric members of the second drive beams 230a and 230b.

  In the present embodiment, a voltage is applied to the upper and lower electrodes of the piezoelectric members of the first drive beams 130a and 130b, and the first drive beams 130a and 130b are bent and deformed, whereby the first torsion bar ( The first elastic support members 120a and 120b are twisted and the movable part 10 rotates in the first direction around the axis of the first torsion bars 120a and 120b. Further, a voltage is applied to the upper and lower electrodes of the piezoelectric members of the second drive beams 230a and 230b, and the second drive beams 230a and 230b are bent and deformed, whereby the second torsion bars 220a and 220b are deformed. Torsional deformation occurs, the movable frame 140 rotates around the axes of the second torsion bars 220a and 220b, and the movable unit 10 rotates in the second direction. Here, the natural frequencies of the vibration modes in the first rotation direction around the axis of the first torsion bars 120a and 120b and the second rotation direction around the axis of the second torsion bars 220a and 220b are differentiated, By driving the first drive beams 130a and 130b and the second drive beams 220a and 220b at the respective frequencies, the movable portion 10 can be greatly rotated in the biaxial direction.

  In general, this type of biaxial piezoelectric optical deflector drives the first driving beams 130a and 130b to scan in the horizontal direction (X direction) and scans the second driving beams 220a and 220b for a two-dimensional image or the like. It is used in such a manner that it is driven to scan in the vertical direction (Y direction). Therefore, the driving frequency of the first driving beams 130a and 130b is set to be significantly higher than the driving frequency of the second driving beams 220a and 220b.

  Also in the biaxial piezoelectric optical deflector of the present embodiment, for example, the minimum or maximum value of the drive voltage applied to the piezoelectric members of the first drive beams 130a and 130b is set to the coercive electric field value of PZT used for the piezoelectric members. To 0V, it is possible to reduce the amplitude variation with time of the mirror unit 15.

  The present embodiment provides an optical scanning device as an optical writing unit of an image forming apparatus using the piezoelectric optical deflector that deflects light in the uniaxial direction of the first and second embodiments.

  FIG. 8 is an overall configuration diagram of the optical scanning device of the present embodiment, and FIG. 9 is a connection diagram of a piezoelectric optical deflector used in the optical scanning device and driving means.

  In FIG. 8, a laser beam (light beam) from a light source unit 1020 as a laser element is deflected by a piezoelectric light deflector 1022 after passing through an imaging optical system (collimator lens system) 1021. As the piezoelectric light deflector 1022, the piezoelectric light deflector having any one of the configurations of the first to third embodiments is used. The laser beam deflected by the piezoelectric light deflector 1022 is then irradiated in a spot shape on the surface to be scanned such as the photosensitive drum 1002 through the scanning optical system 1023 including the first lens 1023a, the second lens 1023b, and the reflection mirror 1023c. And imaged.

  As shown in FIG. 9, the piezoelectric light deflector 1022 is accommodated in a package member 1030. The package member 1030 is made of resin or ceramic material. The piezoelectric light deflector 1022 accommodated in the package member 1030 is electrically connected to the driving means 1024. The driving means 1024 applies a driving voltage between the lower electrode and the upper electrode of the driving beam that is a component of the piezoelectric light deflector 1022. As a result, the movable portion (mirror portion) of the piezoelectric light deflector 1022 rotates to deflect the laser light, and the surface to be scanned is optically scanned.

  The optical scanning device using the piezoelectric optical deflector of the present invention is optimal as a constituent member of an optical writing unit for an image forming apparatus such as a photographic printing 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. 10 shows an overall configuration diagram of an example of the image forming apparatus of this embodiment. In FIG. 10, 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 a photosensitive drum 1002 as a photosensitive member in the axial direction of the drum with one or a plurality of laser beams modulated by a recording signal. The photosensitive drum 1002 is rotationally driven in the direction of an arrow 1003, and an optical latent image (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 a laser in one axial direction of the present invention. Piezoelectric light deflector 1022 for deflecting the beam, and image formation for forming an image of a laser beam (light beam) modulated by the recording signal from the light source unit 1020 on the mirror surface of the movable part of the piezoelectric light deflector 1022 An 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 are included. The The piezoelectric 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 piezoelectric optical deflector 1022. Note that the piezoelectric light deflector 1022 is actually housed in the package member 1030 as shown in FIG.

  Since the piezoelectric light deflector 1022 consumes less power for driving than the conventional rotary polygon mirror, it is advantageous for power saving of the image forming apparatus. Further, since the wind noise during vibration of the movable part of the piezoelectric light deflector 1022 is smaller than that of the rotary polygon mirror, it is advantageous for improving the quietness of the image forming apparatus. Further, the piezoelectric light 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 of the image forming apparatus. It is.

  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 on which the piezoelectric light deflector for deflecting light in the biaxial direction described in the third embodiment is mounted.

  FIG. 11 shows an overall configuration diagram of an example of the image projection apparatus of the present embodiment. In FIG. 11, 2001-R is a laser light source that emits red (R) laser light, 2001-G is a laser light source that emits green (G) laser light, and 2001-B is blue (B) laser light. This is a laser light source that emits light. The R, G, and B laser beams emitted from the laser light sources 2001-R, 2001-G, and 2001-B are combined by a cross dichroic prism 2002 and are incident on the reflecting surface of the biaxial piezoelectric optical deflector 2003. . The biaxial piezoelectric optical deflector 2003 deflects and scans the combined laser light input to the reflecting surface in the biaxial direction (main scanning / sub-scanning direction) and projects it onto the projection surface (screen) 2004. The R, G, and B laser beams emitted from the laser light sources 2001-R, 2001-G, and 2001-B are output from the two-axis piezoelectric light deflector 2003 for each color component of the display image by a light source driving unit (not shown). Intensity modulation (pulse width modulation, amplitude modulation, etc.) is performed in accordance with the timing of two-dimensional deflection scanning. As a result, two-dimensional image information is projected on the projection surface 2004.

  Here, the two-axis piezoelectric light deflector 2003 has a configuration as shown in FIG. In the X direction (main scanning direction), the first drive beams 103a and 130b are driven at the resonance frequency, and the movable unit 10 is rotated and amplified at high speed using the resonance characteristics. On the other hand, in the Y direction (sub-scanning direction), the second drive beams 230a and 230b are driven at a frequency lower than the resonance frequency to cause the movable frame 140 to rotate at a low speed. That is, the difference between the X direction vibration and the Y direction drive frequency is made sufficiently large. Thereby, a large speed difference can be obtained between the X-axis direction and the Y-axis direction. Therefore, the two-axis piezoelectric light deflector 2003 can scan the light beam two-dimensionally and project an image on the projection surface (screen) 2004 two-dimensionally.

  Also in the image projection apparatus, a rotary scanning mirror such as a polygon mirror can be used as the light deflecting unit, but the biaxial piezoelectric optical deflector 2003 consumes less power for driving than the rotary scanning mirror. Therefore, it is advantageous for power saving of the image projection apparatus. Further, since the wind noise during vibration of the movable part of the biaxial piezoelectric optical deflector 2003 is smaller than that of the rotary scanning mirror, it is advantageous for improving the quietness of the image projection apparatus. Further, the two-axis piezoelectric optical deflector 2003 requires much less installation space than the rotary scanning mirror and has a small amount of heat generation, so that it can be easily downsized. It is advantageous to make.

  Although FIG. 11 shows a configuration example in which a color image is projected, the present invention can be applied to a case where a monochrome image is projected by using one laser light source.

  FIG. 12 is a plan view of the piezoelectric light deflector according to the seventh embodiment. 12, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals. Although the overall configuration is basically the same as that of the first embodiment, in this embodiment, the drive beams 11a and 11b are formed in a meandering shape.

  As shown in FIG. 12, the drive beams 11a and 11b are provided on the beam-shaped members 16 and 17 with meandering members having folded portions 14 and 15 and beam-shaped members 16 and 17 provided between the folded portions. The piezoelectric members 13A and 13B are provided. The piezoelectric members 13A and the piezoelectric members 13B are provided alternately. The beam members 16 and 17 are provided in a direction perpendicular to the rotation axis XX.

  For example, a beam-shaped member 16x1 is provided between the folded portion 14x1 and the folded portion 15x1. A beam-shaped member 16x2 is provided between the folded portion 14x2 and the folded portion 15x2. A beam-shaped member 16x3 is provided between the folded portion 14x3 and the folded portion 15x3.

  Further, for example, a beam-like member 17x1 is provided between the folded portion 15x1 and the folded portion 14x2. A beam-shaped member 17x2 is provided between the folded portion 15x2 and the folded portion 14x3. A beam-shaped member 17x3 is provided between the folded portion 15x3 and the folded portion 14x3.

  In addition, for example, the piezoelectric member 13A is provided on the beam-like members 16x1, 16x2, and 16x3, and for example, the piezoelectric member 13B is provided on the beam-like members 17x1, 17x2, and 17x3.

  In this embodiment, different voltages are applied to the piezoelectric member 13A and the piezoelectric member 13B, respectively. Here, FIG. 13 shows signal waveforms of voltages applied to the piezoelectric member 13A and the piezoelectric member 13B. The horizontal axis is time, and the vertical axis is applied voltage.

  As shown in FIG. 13, the voltage of the signal waveform a is applied to the piezoelectric member 13A, and the voltage of the signal waveform b is applied to the piezoelectric member 13B.

  As is clear from the signal waveform a and the signal waveform b, the piezoelectric member 13A and the piezoelectric member 13B may be applied with the same voltage or different voltages.

  When the voltage of the signal waveform a and the signal waveform b is applied to the piezoelectric member provided on each beam member, the drive beams 11a and 11b operate as cantilevers, and the movable part (mirror part) 10 is Rotating drive. That is, the drive beams 11a and 11b can be driven in the Y direction (sub-scanning direction) (non-resonant driving) to perform optical scanning.

  Note that by controlling the signal waveform of the voltage applied to the piezoelectric member 13A and the piezoelectric member 13B, it is possible to reduce the speed unevenness in the sub-scanning direction. For example, the applied voltage is adjusted so that the signal waveform a and the signal waveform b are different from each other, and the phase between the signal waveform a and the signal waveform b is shifted to change the speed in the sub-scanning direction. be able to.

  As described above, the optical beam can be scanned by non-resonant driving in the sub-scanning direction by forming the driving beam provided in the piezoelectric optical deflector in a meandering manner and controlling the voltage applied to the plurality of piezoelectric members. .

  FIG. 14 is a plan view of a two-dimensional optical deflector according to the eighth embodiment. 14, the same parts as those in FIG. 12 are denoted by the same reference numerals. Although the overall configuration is basically the same as that of the seventh embodiment, in this embodiment, the movable portion is rotated and oscillated not only around the X axis but also around the Y axis. Thereby, optical scanning in the biaxial direction becomes possible.

  As shown in FIG. 14, the movable part (reflection mirror part) 20 that reflects the laser light is supported by a pair of torsion bars 21a and 21b. The end of the torsion bar 21a (21b) is supported by one end of the piezoelectric cantilever 22a (22b), and the other end of the piezoelectric cantilever 22a (22b) is supported by the movable frame 23. The movable frame 23 is supported by one end of the drive beams 11a and 11b, and the other end of the drive beams 11a and 11b is supported by the frame member 25. A piezoelectric member 13 is independently provided on each beam member.

[Rotation around Y axis]
In the two-dimensional optical deflector, when the piezoelectric cantilevers 22a and 22b are driven, the torsion bars 21a and 21b that support the movable portion 20 are twisted. Thereby, the movable part 20 vibrates around the Y axis.

  By making the voltage applied to the piezoelectric cantilevers 22a and 22b a sine wave, the piezoelectric cantilevers 22a and 22b bend and vibrate. In other words, the bending vibration of the piezoelectric cantilevers 22a and 22b is converted into rotational vibration (torsional vibration) by the torsion bars 21a and 21b, so that the movable portion 20 is rotationally vibrated. The rotation of the movable part 20 is a resonance (mechanical resonance) drive.

  For example, the applied voltage may be a sine wave voltage of about 20 kHz. In this case, the movable part 20 is rotated at about 20 kHz by the twist of the torsion bars 21a and 21b, and the rotation angle of the movable part 20 is about ± 15 °.

[Rotation around X axis]
In the two-dimensional optical deflector, when the drive beams 11a and 11b are driven, the movable frame 23 rotates around the X axis, and the movable portion 20 rotates and vibrates around the X axis.

  Each beam-shaped member is deformed by setting the voltage applied to the piezoelectric members 13A and 13B to a sawtooth wave (see FIG. 13). That is, as the deformation of each beam-like member is accumulated and the meandering member is also deformed, the drive beams 11a and 11b operate as cantilevers, and thereby the movable portion 20 rotates and vibrates. The rotation of the movable unit 20 is non-resonant driving. The rotational vibration of the drive beams 11a and 11b can be controlled by adjusting the phase of the sawtooth wave and the maximum potential difference between the voltage applied to the piezoelectric member 13A and the voltage applied to the piezoelectric member 13B.

  For example, a sawtooth voltage of about 60 Hz may be applied. The sawtooth voltage can also shift the driving frequency by several Hz in consideration of the relationship with the resonance frequency.

  In this case, it is preferable that the minimum value of the driving voltage of the piezoelectric member is not less than the coercive electric field value of PZT so that polarization inversion does not occur and not more than 0 V so that the imprint phenomenon does not proceed. In the case of reversing the polarity of the drive voltage, similarly, the maximum value of the drive voltage of the piezoelectric member is preferably not more than the coercive electric field value of PZT and not less than 0V.

  By precisely controlling the voltages applied to the piezoelectric member 13A and the piezoelectric member 13B, optical scanning with high uniformity in the sub-scanning direction is possible.

  As described above, by using the sine wave vibration by mechanical resonance driving around the Y axis and the rotational vibration by non-resonance driving around the X axis, the movable unit 20 is driven to perform optical scanning in the biaxial direction. Can be realized. Further, in the two-dimensional optical deflector, it is possible to reduce the progress of the imprint phenomenon even with respect to non-resonant driving, and to improve the stability of fluctuation with time of the displacement amount of the mirror part during continuous driving.

DESCRIPTION OF SYMBOLS 10 Movable part 15 Mirror part 20a, 20b Torsion bar (elastic support member)
30a, 30b Driving beam 31a, 31b Beam-like member 32a, 32b Piezoelectric member 34a, 34b Upper electrode 35a Lower electrode 36a Insulating layer (insulating film)
40 Fixed base 120a, 120b First torsion bar (first elastic support member)
130a, 130b first driving beam 140 movable frame 220a, 220b second torsion bar (second elastic support member)
230a, 230b Second drive beam 134a, 134b Upper electrode 240 Fixed base

JP 2011-018026 A

Claims (10)

A fixed base, a movable part having a mirror, an elastic support member that supports the movable part, and a drive beam that supports the elastic support member on the fixed base;
The drive beam is a piezoelectric optical deflector having a beam-shaped member and a lower electrode, a piezoelectric member , an upper electrode, and an insulating layer laminated on the beam-shaped member.
One end of the drive beam is connected to the elastic support member, and the other end of the drive beam is connected to the fixed base,
The stacked upper electrode has four corners, a shape in which two corners on the side of the one end is rounded, the two corners of the side of the other end is not rounded A piezoelectric light deflector having a shape . A movable frame, a movable part having a light reflecting surface, a first elastic support member that supports the movable part, a first drive beam that supports the first elastic support member on the movable frame,
A fixed base; a second elastic support member that supports the movable frame; and a second drive beam that supports the second elastic support member on the fixed base;
The first driving beam has a beam-shaped member and a lower electrode, a piezoelectric member, an upper electrode, and an insulating layer stacked on the beam-shaped member,
Said second drive beam, the piezoelectric light deflector and a piezoelectric member provided on the beam member and the beams like member,
One end of the first drive beam is connected to the first elastic support member, and the other end of the first drive beam is connected to the movable frame;
The stacked upper electrode has four corners, a shape in which two corners on the side of the one end is rounded, the two corners of the side of the other end is not rounded A piezoelectric light deflector having a shape . A fixed base, a movable part having a mirror, an elastic support member that supports the movable part, and a drive beam that supports the elastic support member on the fixed base;
The drive beam is a piezoelectric optical deflector having a beam-shaped member and a lower electrode, a piezoelectric member , an upper electrode, and an insulating layer laminated on the beam-shaped member.
One end of the drive beam is connected to be orthogonal to the longitudinal direction of the elastic support member, and the other end of the drive beam is connected to the fixed base,
The stacked upper electrode has four corners, a shape in which two corners on the side of the one end is rounded, the two corners of the side of the other end is not rounded A piezoelectric light deflector having a shape . A fixed base, a movable part having a mirror, an elastic support member that supports the movable part and is connected to both sides of the movable part, and a drive beam that supports the elastic support member on the fixed base;
The drive beam is a piezoelectric optical deflector having a beam-shaped member and a lower electrode, a piezoelectric member , an upper electrode, and an insulating layer laminated on the beam-shaped member.
One end of the driving beam is connected to the elastic support member, the other end of the driving beam is connected to a fixed base, and the driving beam is connected to both sides with the movable part interposed therebetween,
The stacked upper electrode of the piezoelectric member on one end side of the drive beam has four corners, and the two corners on the one end side are rounded, and the other A piezoelectric light deflector characterized in that the two corners on the end side are not rounded . A movable frame, a movable portion having a light reflecting surface, a first elastic support member that rotatably supports the movable portion, and a first drive that supports the first elastic support member with respect to the movable frame With a beam,
A frame member, a second elastic support member that rotatably supports the movable frame, and a second drive beam that supports the second elastic support member with respect to the frame member;
The first driving beam has a beam-shaped member, and a lower electrode, a piezoelectric member , an upper electrode, and an insulating layer stacked on the beam-shaped member,
The second driving beam is a piezoelectric light deflection formed by a meandering member having a plurality of folded portions and a beam-like member provided between the folded portions, and a piezoelectric member provided on the beam-like member. In the vessel
One end of the first drive beam is connected to the first elastic support member, and the other end of the first drive beam is connected to the movable frame,
The stacked upper electrode has four corners, a shape in which two corners on the side of the one end is rounded, the two corners of the side of the other end is not rounded A piezoelectric light deflector having a shape .   5. The piezoelectric optical deflector according to claim 1, wherein the movable portion and the elastic support member are cantilevered with respect to the fixed base by a pair of the drive beams.   The piezoelectric optical deflector according to claim 2, wherein the movable portion and the first elastic support member are cantilevered with respect to the movable frame by a pair of the first drive beams. Optical scanning apparatus comprising: a piezoelectric light deflector according to any one of claims 1 to 7 for deflecting the scanning light beam. 9. The optical scanning device according to claim 8 , 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 transfer unit that transfers the toner image to a recording sheet. An image forming apparatus comprising: Image projection apparatus characterized by having a piezoelectric light deflector according to any one of claims 1 to 7.

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