JP2015176052A - Optical deflector, optical scanning device, image forming device, and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical deflector capable of accurately suppressing motion anomaly of a mirror unit in rotational oscillation thereof due to variation in manufacturing accuracy.SOLUTION: An optical deflector 2 includes a mirror unit 6 having a light reflective surface 4, torsion bar springs 8 and 10 which work as a pair of elastic support members that support the mirror unit 6 in a way that allows rotational oscillation thereof, a pair of drive beams 12 and 14, and a fixed base 16. Surfaces of the drive beams 12 and 14 on a reflective surface 34 side have a piezoelectric body 20 fixed thereon. The ends of the drive beams 12 and 14 on the fixed base 16 side are integrally connected and the piezoelectric body 20 is also continuously arranged. When voltage is applied to the piezoelectric body 20, an electrostrictive characteristic of the piezoelectric body 20 changes the volume thereof to expand or contract itself, causing the drive beans 12 and 14 to be warped to exhibit bending deformation. This causes twisting deformation of the torsion bar springs 8 and 10, which rotationally oscillates the mirror unit 6.

Description

  The present invention relates to an optical deflector for deflecting and scanning a light beam such as a laser beam, an optical scanning device having the optical deflector, a copier, a printer, a facsimile, a plotter having the optical scanning device, or at least one of them. The present invention relates to an image forming apparatus such as a multi-function peripheral equipped with an image projector, and an image projection apparatus equipped with the optical deflector.

The deflecting mirror as an optical deflector includes those using an electrostatic force, those using an electromagnetic force, and those using a piezoelectric force.
The deflecting mirror using electrostatic force has parallel plate type and comb-shaped electrodes, and the comb-shaped electrodes can generate a relatively large force due to the recent improvement of microfabrication technology.
However, since a sufficient light deflection angle cannot be obtained, the drive voltage must be increased to compensate.
In order to increase the drive voltage, it is necessary to increase the size of the power supply system components, but the overall size increases and the cost increases.

Since it is necessary to dispose a permanent magnet outside the deflecting mirror using electromagnetic force, the configuration of the device is complicated, the productivity is low, and it is difficult to reduce the size.
Although using a magnetostrictive film etc. is also examined, since the characteristic as a magnetic body is inferior, sufficient characteristics cannot be obtained.
Further, if a current is passed through the coil, excessive heat is likely to be generated, resulting in an increase in power consumption.

When piezoelectric power is used, a relatively large driving voltage is required, but a large force can be generated with small power.
Although this type of piezoelectric device generates a large amount of force but has a very small amount of deformation, in order to enlarge this, a piezoelectric material is bonded to another beam-like elastic member to form a unimorph structure or a bimorph structure.
In this way, a large deformation can be obtained by changing a slight distortion in the in-plane direction due to the piezoelectric power into a warp.

The other end of the pair of elastic support members that support the mirror portion so as to be able to rotate and vibrate is supported by a pair of bending springs (driving beams) that are fixed to the base table and can be deformed. A configuration for rotational vibration is also known (for example, Patent Document 1).
When a voltage is applied to the piezoelectric body fixed to the driving beam, the piezoelectric body expands and contracts to cause bending deformation of the driving beam, which causes torsional deformation in the elastic support member, and the mirror portion rotates and vibrates. .
The pair of drive beams are individually fixed to the base table.

  However, in the conventional configuration as described above, since the pair of drive beams are formed independently, if the shape of each of the drive beams is different due to variations in manufacturing accuracy, the balance is lost, and the behavior of the mirror portion in rotational vibration There was a problem that an abnormality occurred.

  The present invention has been made in view of such a current situation, and a main object thereof is to provide an optical deflector capable of highly accurately suppressing an abnormal behavior in rotational vibration of a mirror portion due to variations in manufacturing accuracy.

  In order to achieve the above object, an optical deflector of the present invention includes a mirror part having a light reflecting surface, and a pair of elastic support members that are fixed to the mirror part at one end and support the mirror part so as to be capable of rotational vibration. A pair of driving beams having one end fixed to the other end of the elastic support member and a fixed base having the other end of the pair of driving beams fixed The mirror portion and the pair of elastic support members are cantilevered with respect to the fixed base via the pair of drive beams, and the drive beam based on the expansion and contraction of the piezoelectric body by voltage application The elastic support member is twisted and deformed by bending deformation, and the mirror portion rotates and vibrates, and the pair of drive beams have a shape integrally connected on the fixed base side.

  According to the present invention, it is possible to suppress a behavioral abnormality in the rotational vibration of the mirror portion due to variations in manufacturing accuracy of the optical deflector with high accuracy.

1 is a perspective view of an optical deflector according to a first embodiment of the present invention. It is a figure which shows the optical deflector of FIG. 1, (a) is a front view, (b) is a side view. It is a general | schematic front view which shows the wiring structure of a voltage application. 4A and 4B are diagrams showing a voltage application wiring configuration, in which FIG. 3A is a cross-sectional view taken along line XX of FIG. 3, and FIG. It is a figure which shows the structure in case it has a piezoelectric material for a detection, (a) is a front view, (b) is a side view. It is a figure which shows the optical deflector which concerns on 2nd Embodiment, (a) is a front view, (b) is a side view. It is a figure which shows the structure in the case of having the piezoelectric material for a detection in 2nd Embodiment, (a) is a front view, (b) is a side view. It is a figure which shows the optical deflector which concerns on 3rd Embodiment, (a) is a front view, (b) is a side view. It is a general | schematic perspective view of the optical scanning device which concerns on 4th Embodiment. It is a schematic block diagram of the image forming apparatus which concerns on 5th Embodiment. It is a schematic block diagram of the image projector which concerns on 6th Embodiment. It is a principal part perspective view of the image projector.

Embodiments of the present invention will be described below with reference to the drawings.
The first embodiment will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the optical deflector 2 according to the present embodiment is a deflection mirror that deflects light in one direction.
The optical deflector 2 includes a mirror part 6 having a light reflecting surface 4, torsion bar springs 8 and 10 as a pair of elastic support members that are fixed to the mirror part 6 at one end and support the mirror part 6 so as to be capable of rotational vibration. , A pair of drive beams 12, 14 having one end fixed to the other end side of the torsion bar spring, and a fixed base 16 to which the other end side of the drive beams 12, 14 is fixed.
A cylindrical reinforcing rib 18 is formed on the side of the mirror 6 opposite to the light reflecting surface 4.

Drive beams 12 and 14 are connected to the ends of the torsion bar springs 8 and 10 opposite to the mirror part 6 in such a direction that the mirror part 6 bends in the axial direction in which the mirror part 6 twists and rotates.
The drive beams 12 and 14 are fixed to the fixed base 16 so as to protrude from the fixed base 16 in the same direction, and are disposed only on one side of the torsion bar springs 8 and 10.
That is, the mirror portion 6 and the pair of torsion bar springs 8 and 10 are cantilevered with respect to the fixed base 16 via the pair of drive beams 12 and 14.

The drive beams 12 and 14 have a configuration in which a piezoelectric body is fixed to a beam-shaped member.
That is, a piezoelectric body (piezoelectric member) 20 is fixed in a film shape or a layer shape on the surface of the drive beams 12 and 14 on the reflection surface 34 side, and a drive beam having a flat strip-like unimorph structure as a whole is formed.
In this embodiment, the mirror part 6, the torsion bar springs 8 and 10, and the drive beams 12 and 14 are integrally formed by processing with a silicon material by a MEMS (micro electro mechanical systems) process.
The mirror part 6 forms the light reflecting surface 4 by forming a thin film of metal such as aluminum or gold on the surface of the silicon substrate.
The ends of the pair of drive beams 12 and 14 on the fixed base 16 side are connected and integrated. That is, the drive beams 12 and 14 as a whole have a single-piece shape (single plate shape) connected on the fixed base side.

Although the wiring for applying an electric field to the piezoelectric body 20 is omitted in FIG. 1, the configuration will be described with reference to FIGS. 4A is a cross-sectional view taken along line XX in FIG. 3, and FIG. 4B is a cross-sectional view taken along line YY in FIG.
As shown in FIG. 4, the lower electrode 22 is provided on the surface of the driving beam, the piezoelectric body 20 and the upper electrode 24 are provided thereon, and the insulating layer 26 is provided on the outermost surface.
The lower electrode, the piezoelectric material, and the upper electrode are deposited on the beam-like member in this order by sputtering, and are etched so that only necessary portions remain.
The adhesive layer can be made of titanium (Ti), the upper and lower electrodes can be platinum (Pt), and the piezoelectric material can be lead zirconate titanate (PZT).
In FIG. 4, reference numerals 28 and 30 denote contact holes, and 32 and 34 denote aluminum wirings (section display is omitted).

As shown in FIG. 3, the wiring pattern for applying a voltage to the piezoelectric body 20 is connected to the central portion of the pair of drive beams 12 and 14. In FIG. 3, the insulating layer 26 is omitted.
More specifically, the wiring for the upper electrode 24 is disposed at the center of the portion connecting the pair of drive beams 12 and 14, and the wiring for the lower electrode 22 is disposed at the substantially central portion of the fixed base 16.
Thus, when the wiring is drawn from the land portion and a voltage is applied between the upper electrode 24 and the lower electrode 22, the volume changes due to the electrostrictive characteristics of the piezoelectric body 20 and expands and contracts in the in-plane direction on the surface of the beam-shaped member. Thus, the drive beams 12 and 14 are warped to bend and deform.
By disposing the connection portion of the wiring pattern with the electrode of the piezoelectric member so as to avoid the range in which the drive beams 12 and 14 vibrate, the failure of the voltage application configuration can be suppressed.
In this embodiment, the example in which the piezoelectric body 20 is manufactured by the film forming process has been described. However, the piezoelectric body 20 may be manufactured by a method of attaching a bulk material.

Since the longitudinal directions of the torsion bar springs 8 and 10 and the drive beams 12 and 14 are arranged substantially orthogonally, the rotational force generated by bending deformation of the drive beams 12 and 14 is efficiently twisted. Can tell the transformation of direction.
Further, since the drive beams 12 and 14 have a structure in which the torsion bar springs 8 and 10 and the mirror portion 6 are cantilevered, the tips of the drive beams 12 and 14 can freely vibrate and obtain a large amplitude. be able to.

As shown in FIG. 2, the center (center of gravity) p <b> 1 of the mirror portion 6 is close to the connection portion between the drive beams 12 and 14 and the fixed base 16 with respect to the center line P <b> 2 of the torsion bar springs 8 and 10. Is offset in the direction.
By doing so, the rotational vibration of the mirror unit 6 is further increased by the vibration of the drive beams 12 and 14.

As described above, the ends of the pair of drive beams 12 and 14 on the fixed base 16 side are connected and integrated.
By connecting the independent drive beams together, the pair of drive beams 12 and 14 vibrate substantially integrally, and the mirror vibration behavior caused by the non-uniform shape of the drive beams due to variations in manufacturing accuracy. Abnormalities can be suppressed.
Further, by integrating the pair of driving beams 12 and 14, a place where the piezoelectric body 20 is disposed is widened, and a larger vibration energy can be generated in the driving beam.
That is, the amount of amplitude of the mirror unit 6 with respect to the applied voltage can be increased (increase in amplitude sensitivity).
A device with higher output efficiency can be manufactured by disposing a piezoelectric body in a portion that is a simple space existing between a pair of drive beams provided independently.

Since the capacitance of the piezoelectric film increases, the power consumption increases. However, since the amplitude sensitivity increases, the operation can be performed at a low voltage, so that the power consumption can be suppressed.
If it is necessary to increase the operating frequency of the optical deflector according to the specifications of the application in which the optical deflector is mounted, the rigidity of the elastic support member (torsion bar spring) is increased to increase the resonance frequency of the rotational vibration of the mirror section. I have to let it.
In order to operate efficiently, it is necessary to increase the resonance frequency of the bending (deflection) of the drive beam corresponding to the resonance frequency of rotation.
As in this embodiment, by connecting and integrating the pair of drive beams 12 and 14, the rigidity of the entire drive beam supporting the mirror portion and the torsion bar spring can be increased. It is possible to easily design a larger size and a higher vibration frequency of the mirror portion.

Furthermore, in the case of manufacturing by a film forming process, the piezoelectric material is formed on the entire wafer, and then an unnecessary part is removed. Therefore, increasing the area ratio of the piezoelectric material within the wafer surface reduces the removal region. Effective above.
Furthermore, in the present embodiment, as shown in FIG. 1 and the like, not only the beam-shaped member but also the piezoelectric member disposed thereon is connected.
The wiring for applying a voltage to the drive beam is patterned with aluminum, etc., but if they are individually connected to the drive beams on both sides, the resistance will be slightly different between the two and there will be a difference in the drive voltage between the two The balance between the two is lost.

However, since the piezoelectric member is also connected and arranged in this manner, the uniformity of the electric field applied to the piezoelectric member is also improved, so that the operation of the mirror unit 6 can be stabilized.
That is, by connecting and integrating the piezoelectric members, it is possible to make the resistance uniform and suppress variations in driving voltage. As a result, variations in vibration applied to the pair of elastic support members (torsion bar springs) can be suppressed, and abnormal vibration behavior of the mirror portion can be suppressed.
Further, by integrating the wiring patterns that are respectively connected to the piezoelectric members on the pair of independent drive beams, the wiring patterns can be simplified and the defect rate can be reduced.

When mounted in the system, it is necessary to know the amplitude amount of the mirror unit 6 accurately, and a detection signal indicating the amplitude amount of the mirror unit may be required.
In such a case, as shown in FIG. 5, the detecting piezoelectric members 38 and 40 are provided.
A detection signal is obtained by the bending of the drive beam. Since the amplitude corresponding to the mirror portion is in the vicinity of the connection portion with the torsion bar spring, the detection piezoelectric members 38 and 40 for detecting the detection signal are provided in this vicinity. It is desirable to arrange.
By applying a drive signal at the natural frequency of the vibration mode, the mirror unit can obtain a large angular amplitude. The driving waveform may be a pulse or a wave shape, and the frequency may be in the vicinity of the above natural frequency.

In the present embodiment, as described above, the configuration in which the piezoelectric material is formed by sputtering together with the lower electrode and the upper electrode is shown. However, the piezoelectric material is a bulk material cut into a predetermined size and pasted with an adhesive. Also good.
Further, it may be formed by CVD, sol-gel method, aerosol deposition method (AD method) or the like.
In the present embodiment, the drive beams 12 and 14 are described as having a unimorph structure in which a piezoelectric material is disposed on one side of the beam-shaped member. However, a bimorph structure in which the piezoelectric material is disposed on both surfaces of the beam-shaped member may be employed.

6 and 7 show a second embodiment.
Note that the same parts as those in the above embodiment are denoted by the same reference numerals, and unless otherwise specified, description of the configuration and functions already described is omitted, and only the main part will be described (the same applies to other embodiments below).
The basic configuration of the optical deflector 2 is the same as that of the first embodiment. In the first embodiment, the torsion bar spring and the drive beam are connected on the center side of the mirror portion of the drive beam, but in this embodiment, they are connected on the outside as viewed from the center of the mirror portion.
With this configuration, the distance between the drive beams 12 and 14 can be reduced, and the size of the device can be reduced.

When mounted in a system, it is necessary to know the amplitude amount of the mirror portion accurately, and a detection signal indicating the amplitude amount of the mirror portion may be required.
In such a case, detection piezoelectric bodies 42 and 44 are provided as shown in FIG.
In the first embodiment, as shown in FIG. 5, the detection piezoelectric body is arranged inside the drive beam (near the mirror portion), but in the present embodiment, it is arranged outside.
A detection signal is obtained by the bending of the drive beam. Since the amplitude of the mirror portion corresponds to the vicinity of the connection portion with the torsion bar spring, the detection piezoelectric bodies 42 and 44 for detecting the detection signal in the vicinity thereof. It is desirable to arrange.

A third embodiment will be described with reference to FIG.
The basic configuration of the optical deflector 2 is the same as in the first and second embodiments.
In the first and second embodiments, the portion between the torsion bar spring and the drive beam where the pair of drive beams are connected has a rectangular shape. However, a predetermined interval is provided in the circumferential direction of the mirror unit 6.
That is, the connecting portion between the drive beams 12 and 14 is formed in an arc shape along the peripheral surface of the mirror portion 6.
In this way, the space between the pair of driving beams can be effectively used, and stress concentration at the corners of the driving beams can be suppressed and the vibration can be made difficult to break.
In addition, the electric field concentration can be suppressed to make it difficult to damage the piezoelectric member and the electrode.

FIG. 9 shows a fourth embodiment (optical scanning device).
Laser light from a laser element 50 as a light source passes through a collimating optical system 52 and is then deflected by an optical deflector 2.
The deflected beam is imaged in a spot shape on a scanning surface 60 such as a photosensitive drum by an imaging optical system including an fθ lens 54, a toroidal lens 56, and a mirror 58.
The optical deflector 2 is the optical deflector shown in the above embodiments. It is driven by applying a driving voltage between the lower electrode and the upper electrode by a mirror driving means (not shown).
The optical scanning device according to the present embodiment is suitable as an optical scanning device for an image forming apparatus such as a photographic printing type printer or a copying machine.

FIG. 10 shows a fifth embodiment (image forming apparatus).
The optical writing unit (optical scanning device) 62 including the optical deflector shown in each of the above embodiments emits a laser beam to the surface to be scanned and writes an image.
Reference numeral 64 indicates a photosensitive drum as an image carrier having a surface to be scanned as a scanning target by the optical writing unit 62.
The optical writing unit 62 scans the surface (scanned surface) of the photosensitive drum 64 in the axial direction of the photosensitive drum 64 with one or a plurality of laser beams modulated by the recording signal.

The photosensitive drum 64 is rotationally driven in the direction of the arrow 66, and an electrostatic latent image is formed by optically scanning the surface charged by the charging means 68 by the optical scanning device 62.
The electrostatic latent image is visualized as a toner image by the developing unit 70, and the toner image is transferred to a recording paper 74 as a recording medium by the transfer unit 72.
The transferred toner image is fixed on the recording paper 74 by the fixing means 76.
Residual toner is removed from the surface portion of the photosensitive drum that has passed through the portion of the photosensitive drum 64 facing the transfer means 72 by a cleaning section 78.

Instead of the photoconductor drum 64, a belt-like photoconductor may be used.
Alternatively, an intermediate transfer system may be used in which a toner image is temporarily transferred to a transfer medium other than recording paper, and the toner image is transferred from the transfer medium to recording paper and fixed.
The optical writing unit 62 includes a light source unit 80 that emits one or a plurality of laser beams modulated by a recording signal, a light source driving unit 82 that modulates the light source, and the optical deflector 2 described in each of the above embodiments. An image forming optical system 84 for forming an image of a laser beam (light beam) modulated by a recording signal from the light source unit 80 on the light reflecting surface of the optical deflector 2, and one or more reflected by the mirror surface It comprises a scanning optical system 86 that is a means for forming an image of the laser beam of the book on the surface (scanned surface) of the photosensitive drum 64.
The optical deflector 2 is incorporated in the optical writing unit 62 in a form mounted on a circuit board 90 together with an integrated circuit 88 for driving the optical deflector 2.

Since the optical deflector 2 consumes less power for driving than the rotary polygon mirror, it is advantageous for power saving of the image forming apparatus.
Since the wind noise during vibration of the mirror part of the optical deflector 2 is smaller than that of the rotary polygon mirror, it is advantageous for improving the noise reduction of the image forming apparatus.
The optical scanning device 62 requires much less installation space than the rotary polygon mirror, and the amount of heat generated by the optical deflector 2 is very small. Therefore, the optical scanning device 62 can be easily downsized, and thus the image forming apparatus can be downsized. It is advantageous.
The transport mechanism for the recording paper 74, the drive mechanism for the photosensitive drum 64, the control means such as the developing means 70 and the transfer means 72, the drive system for the light source unit 80, and the like are the same as those in the conventional image forming apparatus, and are therefore shown in the figure. Omitted.

11 and 12 show a sixth embodiment (image projection apparatus).
FIG. 11 is a conceptual diagram of an image projection apparatus according to this embodiment, and FIG. 12 is an overall perspective view thereof.
The image projection apparatus includes laser light sources 92R, 92G, and 92B that emit laser beams having three different wavelengths, and a condensing lens that is disposed in the vicinity of the emission end of each of the light sources to make the divergent light from the laser light sources substantially parallel. 94R, 94G, 94B are arranged.
Red laser light LR is emitted from laser light source 92R, green laser light LG is emitted from laser light source 92G, and blue laser light LB is emitted from laser light source 92B.
The laser beam LR is reflected by the mirror 93, passes through the half mirror 95, and is reflected by the laser beam LG half mirror 95.

The substantially parallel laser beams are combined by a combining prism 96 and are incident on a MEMS two-dimensional reflection angle variable mirror 98.
The two-dimensional reflection angle variable mirror 98 has the same configuration as the optical deflector described in the above embodiments.
The two-dimensional reflection angle variable mirror 98 resonates and vibrates at two angles perpendicular to each other with a predetermined angle (for example, about 10 degrees).
One two-dimensional reflection angle variable mirror 98 is not two-dimensional, and two one-dimensional scanning ones may be combined.
Further, a rotary scanning mirror such as a polygon mirror can be used.

Each of the three-wavelength laser light sources is intensity-modulated in accordance with the timing of deflection scanning by the two-dimensional reflection angle variable mirror 98, and projects two-dimensional image information onto the projection surface 100.
Intensity modulation may modulate the pulse width or the amplitude.
The laser light source is driven by converting the modulated signal into a current that can drive the laser by a driving circuit.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such specific embodiments, and unless specifically limited by the above description, the present invention described in the claims is not limited. Various modifications and changes are possible within the scope of the gist.
The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

  The present invention can also be applied to barcode scanners, laser radars, and the like.

2, 1025 Optical deflector 4 Light reflecting surface 6 Mirror part 8, 10 Torsion bar spring 12 as elastic support member 12, 14 Driving beam 16 Fixed base 20 Piezoelectric body 52 Collimating optical system 62 Optical scanning device 64 Photosensitive as image carrier Body drum 70 Developing device as developing means

JP 2011-1182026 A

Claims (8)

A mirror portion having a light reflecting surface;
One end is fixed to the mirror part, and a pair of elastic support members that support the mirror part so as to be able to rotate and vibrate,
A pair of drive beams having a configuration in which a piezoelectric body is fixed to a beam-shaped member, one end of which is fixed to the other end side of the elastic support member;
A fixed base to which the other end of the pair of drive beams is fixed;
With
The mirror part and the pair of elastic support members are cantilevered with respect to the fixed base via the pair of drive beams,
The elastic support member undergoes torsional deformation due to bending deformation of the drive beam based on expansion and contraction of the piezoelectric body due to voltage application, and the mirror portion rotates and vibrates.
The pair of drive beams is a light deflector having a shape integrally connected on the fixed base side. The optical deflector according to claim 1.
The optical deflector having a shape in which the piezoelectric body is integrally connected on the fixed base side. The optical deflector according to claim 1 or 2,
An optical deflector in which a wiring pattern for applying a voltage to the piezoelectric body is connected to a central portion of the pair of driving beams. The optical deflector according to claim 3.
The wiring pattern is an optical deflector disposed on the fixed base. In the optical deflector according to any one of claims 1 to 4,
An optical deflector in which a predetermined gap is formed between the pair of drive beams, the mirror section, and the pair of elastic support members. A light source, an optical deflector that deflects a light beam from the light source, an imaging optical system that forms an image of the deflected light beam in a spot shape on a scanned surface,
With
The optical scanning device according to claim 1, wherein the optical deflector is an optical deflector according to claim 1. An image carrier;
An optical scanning device that forms an electrostatic latent image on the image carrier based on image information;
Developing means for visualizing the electrostatic latent image;
Means for transferring and fixing the visible image to a recording medium;
Have
An image forming apparatus, wherein the optical scanning device is the optical scanning device according to claim 6. A light source;
A collimating optical system that makes the diverging light from the light source substantially parallel,
An optical deflector that displays the image by deflecting and scanning the light passing through the collimating optical system onto the projection surface;
Have
The image projector according to claim 1, wherein the optical deflector is an optical deflector according to claim 1.

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