JP2014085547A - Piezoelectric optical deflector, optical scanner, image forming apparatus and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve drive durability by enabling the prevention of creeping discharge due to deterioration with time, such as long time use in a thin film type piezoelectric optical deflector.SOLUTION: A piezoelectric optical reflector has a movable part 10 having a light reflection surface, torsion bars 20a, 20b of an elastic support member for supporting the movable part 10 rotatably, and drive beams 30a, 30b for supporting the movable part 10 and the torsion bars 20a, 20b in a cantilever fashion with respect to a fixed base 40. The drive beams 30a, 30b are made of beam-shaped members 31a, 31b and thin film piezoelectric members 32a, 32b provided on the beam-shaped members 31a, 31b, and the piezoelectric members 32a, 32b have upper/lower electrodes. Tip angles of the upper electrodes 34a, 34b are formed in the shape of an obtuse angle, such as a circular arcuate shape, here.

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).

  By the way, depending on the usage environment, the optical deflector may be required to be thin in addition to being miniaturized. In order to reduce the thickness of the piezoelectric light deflector, the piezoelectric member may be thinned. However, since the distance between the upper and lower electrodes of the piezoelectric member is reduced, when a driving voltage is applied to the upper and lower electrodes, There is a possibility that electric discharge occurs from the ends of the upper and lower electrodes, and the electrodes are short-circuited (creeping discharge). When the upper and lower electrodes of the piezoelectric member are short-circuited, the operation of the piezoelectric light deflector becomes unstable and becomes inoperable.

  2. Description of the Related Art Conventionally, in piezoelectric actuators, piezoelectric light deflectors, and the like, it is known to cover the piezoelectric member and side surfaces of the upper and lower electrodes with an insulating film in order to prevent a short circuit between the upper and lower electrodes of the piezoelectric member (for example, Patent Documents). 2). However, when the piezoelectric member is driven by applying a driving voltage to the upper and lower electrodes, the insulating film expands and contracts together with the piezoelectric member. As a result, cracks and film defects (dielectric breakdown) occur in the insulating film during long-time driving, and the dielectric strength is reduced, which can cause creeping discharge. Therefore, further measures are indispensable in terms of reliability in piezoelectric optical deflectors used in devices that require high reliability.

  The object of the present invention is to prevent creeping discharge due to deterioration over time, such as long-time driving, even when the piezoelectric member is made thin, in the piezoelectric optical deflector, and to improve the driving durability of the thin-film piezoelectric optical deflector. The goal is to improve.

  The present invention relates to a fixed base, a movable part having a light reflecting surface, an elastic support member that rotatably supports the movable part, and a drive beam that supports the movable member and the elastic support member with respect to the fixed base. The drive beam comprises a beam-like member and a piezoelectric member provided on the beam-like member, the piezoelectric member having an upper electrode and a lower electrode, and the upper electrode and the lower electrode In the piezoelectric optical deflector in which a torsional deformation occurs in the elastic support member by applying a voltage and the driving beam is bent and deformed, and the movable portion rotates, the upper electrode and the lower electrode of the piezoelectric member The main feature is that the tip angle of at least one of the electrodes is obtuse.

  According to the piezoelectric optical deflector of the present invention, it is possible to prevent creeping discharge between the upper and lower electrodes even when the piezoelectric member is thinned.

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 top view of the piezoelectric light deflector of Example 2 of the present invention. It is a top view of the piezoelectric light deflector of Example 3 of the present invention. It is a perspective view of the biaxial piezoelectric light deflector of Example 4 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. 7 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.

  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 side of the beam-like members 31a and 31b, and the driving beams 30a and 30b are formed by the beam-like member 31a and the piezoelectric member 32a, and the beam-like member 31b and the piezoelectric member 32b. Forming.

  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, the tip angles of the upper electrodes 34a and 34b (tip angles on the free ends of the drive beams 30a and 30b) are arcuate obtuse angles. As will be described later, this makes it possible to suppress creeping discharge even if the piezoelectric members 32a and 32b are thinned.

  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. Both corners at the tip of the upper electrode 34a are formed in an arc shape (obtuse angle) (FIG. 31a (a)). 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.

  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 pulse wave or a sine wave, and the drive beams 30a and 30b bend 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, so that the bending vibration of the drive beams 30a and 30b is caused by the torsion bars 20a and 20b. 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 the driving beams 30a and 30b are driven, the insulating layers (insulating films) covering the driving beams 30a and 30b together with the piezoelectric members 32a and 32b also expand and contract, causing defects and cracks in the insulating film during long-time driving. As a result, the dielectric strength decreases. In particular, as shown in FIG. 1, when the drive beams 30a and 30b have a configuration in which the torsion bars 20a and 20b and the movable portion 10 are cantilevered, the amount of displacement increases at the free ends of the drive beams 30a and 30b. Prone to dielectric breakdown.

  When defects or cracks in the insulating film occur in the insulating layers covering the drive beams 30a and 30b and the dielectric strength decreases, creeping discharge is induced between the upper and lower electrodes of the piezoelectric members 32a and 32b. The creeping discharge is more easily induced as the piezoelectric members 32a and 32b become thinner.

  Here, as the tip shape of the electrode is a lead angle, the lines of electric force are concentrated on the tip of the electrode, and creeping discharge is more likely to occur. That is, since the lines of electric force enter perpendicular to the equipotential surface, when the tip shape of the electrode is a lead angle, the electric field concentrates on the electrode tip, and creeping discharge is likely to occur. On the contrary, if the tip shape of the electrode is an arc shape (obtuse angle), it is possible to prevent the electric field from concentrating on the tip of the electrode and to suppress the occurrence of creeping discharge.

  In particular, as shown in FIG. 1, when the piezoelectric drive unit is a cantilevered piezoelectric light deflector, the tip angles of the upper electrodes 31a and 34b (tip angles on the free ends of the drive beams 30a and 30b) are arcuate. (Oblique) makes it possible to prevent the electric field from concentrating on the tips of the upper electrodes 34a and 34b, and even if dielectric breakdown occurs at the free ends of the driving beams 30a and 30b due to long-time driving or the like, creeping discharge Can be suppressed.

  Actually, for a piezoelectric optical deflector having a piezoelectric drive unit with a cantilever structure (the thickness of the piezoelectric member is 2 μm), a durability test was performed by driving it for 1000 hours with a sine wave having a drive voltage of 10 V and a drive frequency of 20 kHz. The vicinity was observed with an optical microscope. When the tip shape of the upper electrode was a right angle, there was evidence of creeping discharge at the tip of the electrode, and there was evidence of dielectric breakdown at the free end of the drive beam. And the movable part operated unstable. On the other hand, when the shape of the tip angle of the upper electrode was an arc shape as in this example, no evidence of creeping discharge was observed, and good results were obtained for the rotational vibration of the movable part.

  1 to 3 show an example in which the tip angle of the upper electrode is an arc shape, but the tip angle of the lower electrode or the tip angle of the upper / lower electrode may be an arc shape (obtuse angle). .

  FIG. 4 is a plan view of the piezoelectric light deflector according to the second embodiment. 4, the same parts as those in FIG. 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-exposed portions, 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 present embodiment, by making the tip corners of the upper electrodes 34a and 34b arc-shaped, it is possible to prevent the electric field from concentrating on the tip of the electrode and to suppress creeping discharge. The same applies when the tip angle of the lower electrode or the upper / lower electrode is circular.

  FIG. 5 is a plan view of the piezoelectric light deflector according to the third embodiment. In FIG. 5, the same parts as those in FIGS. 2 and 4 are denoted by the same reference numerals. In the present embodiment, the shape of the tip angle of the upper electrodes 34a and 34b is changed to an arc shape to be a tapered shape.

  As shown in FIG. 5, creeping discharge can be suppressed even when the tip end corners of the upper electrodes 34a and 34b are tapered. However, according to experiments, when a high driving voltage of 10 V or more is required, it was confirmed that the electric field concentration can be further suppressed when the tip end angle of the electrode is an arc shape. Therefore, when a high driving operation is required, the tip angle of the electrode is preferably an arc shape.

  5 shows an example in which the shape of the tip angle of the upper electrode is tapered in the piezoelectric light deflector having the configuration of the second embodiment, the same applies to the piezoelectric light deflector having the configuration of the first embodiment. The tip angle of the upper electrode may be tapered. Also, the tip angle of the lower electrode or the upper / lower electrode may be tapered.

  FIG. 6 is an overall perspective view of the piezoelectric optical deflector according to the fourth 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. 6, 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 driving beams 130a and 130b each have an upper electrode and a lower electrode, but only the upper electrodes 134a and 134b are shown in FIG. Here, the tip angles of the upper electrodes 134a, 134b (tip angles on the free ends of the drive beams 130a, 130b) are arcuate obtuse angles.

  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.

  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 way that it is driven to scan in the vertical direction (Y direction). Therefore, since the driving frequency of the first driving beams 130a and 130b is set to be much higher than the driving frequency of the second driving beams 220a and 220b, dielectric breakdown occurs at the free ends of the first driving beams 130a and 130b. It becomes easy to get up.

  Therefore, in the present embodiment, the tip angles on the free ends of the first drive beams 130a and 130b are formed in an arc shape (obtuse angle shape), particularly with respect to the upper electrodes 134a and 134b of the first drive beams 130a and 130b. . Thereby, even if dielectric breakdown occurs at the free ends of the first drive beams 130a and 130b due to long-time use or the like, creeping discharge is suppressed and normal operation is permanently maintained.

  In the present embodiment, only the upper electrodes 134a and 134b of the first drive beams 130a and 130b have arc-shaped tip angles, but the upper electrodes of the second drive beams 203a and 230b also have their tips. The corners (tip angles on the free ends of the drive beams 230a and 230b) may be arcuate. The tip angle of the lower electrode or the upper / lower electrode may be an arc shape. Furthermore, the electrode shape at the tip angle may be a tapered shape.

  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 one axial direction of the first to third embodiments.

  FIG. 7 is an overall configuration diagram of the optical scanning device of the present embodiment, and FIG. 8 is a connection diagram of a piezoelectric optical deflector used in the optical scanning device and driving means.

  In FIG. 7, a laser beam (light beam) from a light source unit 1020 serving as a laser element passes through an imaging optical system (collimator lens system) 1021 and is then deflected by a piezoelectric light deflector 1022. 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. 8, 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 of the fifth embodiment is mounted as a constituent member of an optical writing unit.

  FIG. 9 shows an overall configuration diagram of an example of the image forming apparatus of this embodiment. In FIG. 9, 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. 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 transport mechanism for the recording paper 1007, the drive mechanism for the photosensitive drum 1002, the control means such as the developing means 1005 and the transfer means 1006, the drive system for 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 that deflects light in the biaxial direction described in the fourth embodiment is mounted.

  FIG. 10 shows an overall configuration diagram of an example of the image projection apparatus of the present embodiment. In FIG. 10, 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 biaxial piezoelectric optical 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. 10 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.

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 drive 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 JP 2011-209362 A

Claims (7)

A fixed base; a movable part having a light reflecting surface; an elastic support member that rotatably supports the movable part; and a drive beam that supports the movable part and the elastic support member with respect to the fixed base. ,
The driving beam includes a beam-shaped member and a piezoelectric member provided on the beam-shaped member, and the piezoelectric member has an upper electrode and a lower electrode,
In the piezoelectric optical deflector in which a voltage is applied to the upper electrode and the lower electrode, and the driving beam is bent and deformed, torsional deformation occurs in the elastic support member, and the movable part rotates.
A piezoelectric light deflector, wherein a tip angle of at least one of the upper electrode and the lower electrode of the piezoelectric member is obtuse. The movable portion and the elastic support portion are cantilevered with respect to the fixed base by a pair of drive beams,
2. The piezoelectric light deflector according to claim 1, wherein a tip angle of the electrode on the free end side of the drive beam is an obtuse angle.   3. The piezoelectric light deflector according to claim 1, wherein the obtuse angle is an arc shape or a taper shape. A movable frame, a movable part having a light reflecting surface, a first elastic support member that rotatably supports the movable part, and the movable part and the first elastic support member are supported with respect to the movable frame. A first drive beam;
A fixed base; a second elastic support member that rotatably supports the movable frame; and a second drive beam that supports the movable frame and the second elastic support member with respect to the fixed base. ,
Each of the first drive beam and the second drive beam includes a beam-shaped member and a piezoelectric member provided on the beam-shaped member, and the piezoelectric member has an upper electrode and a lower electrode,
A voltage is applied to the upper electrode and the lower electrode of the piezoelectric member of the first driving beam, and the first driving beam is bent and deformed, whereby torsional deformation occurs in the first elastic support member, The movable part rotates in a first direction;
A voltage is applied to the upper electrode and the lower electrode of the piezoelectric member of the second drive beam, and the second drive beam is bent and deformed, whereby torsional deformation occurs in the second elastic support member, In the piezoelectric optical deflector in which the movable frame rotates and the movable portion rotates in the second direction,
The piezoelectric light deflector according to claim 1, wherein a tip angle of at least one of the upper electrode and the lower electrode of the piezoelectric member in at least the first driving beam is an obtuse angle.   4. A piezoelectric light deflector according to claim 1, wherein the light beam is deflected and scanned, and the light beam deflected and scanned by the piezoelectric light deflector is spot-shaped on the surface to be scanned. An optical scanning apparatus comprising: a scanning optical system that forms an image.   6. An optical scanning device according to claim 5, a photosensitive member for forming a latent image by scanning with a light beam, a developing means for developing the latent image with toner, and a transfer means for transferring the toner image to recording paper. An image forming apparatus.   An image projection apparatus comprising the piezoelectric light deflector according to claim 4, wherein the piezoelectric light deflector deflects and scans a light beam to project an image on a projection surface.

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