JP5296427B2 - Optical scanning device, control method therefor, image reading device, and display device - Google Patents

Description

  The present invention relates to an optical scanning device for scanning beam light.

  Laser beam printers and display devices are known as optical scanning devices that sweep light beams.

  In particular, an optical scanning device using a polygon mirror is known as a typical optical scanning device mounted on a laser beam printer. In such an optical scanning device, the laser beam generated from the laser beam generating element is irradiated on the side surface of the polygon mirror. Since the polygon mirror is rotated at a preset rotation speed, the laser beam reflected from the side surface scans the surface of the photosensitive drum via the lens having the fθ characteristic.

  In the case of the optical scanning device using the above polygon mirror, each side of the polygon mirror needs to be a mirror with high accuracy and is driven by a motor, so it is difficult to reduce the size and cost.

  As a means for improving this point, one using a galvanomirror is known. In addition, micromirrors based on MEMS technology using a silicon process are also used, and several methods such as electromagnetic driving, electrostatic driving, and piezoelectric driving have been proposed and put into practical use.

  As an optical scanning device of a driving system different from these, one using a plate wave has been proposed (see Patent Document 1 and Non-Patent Document 1). This method excites torsional vibration in the mirror part by the plate wave generated in the substrate having the mirror part supported by the torsion beam, and the structure is simple and a metal plate by press working can be used. As a technique capable of reducing the cost of an optical scanning device, it is attracting attention.

  FIG. 1A shows the structure of this optical scanning device. This apparatus includes a substrate 10 and a fixing member 16 that fixes one end of the substrate 10. The substrate 10 includes a mirror portion 13 and a pair of twisted beams 12 generated by processing, a beam support portion 19, and a piezoelectric film (piezoelectric element) 11 formed at a predetermined position on the substrate 10. When a drive signal is supplied to the piezoelectric film 11, a plate wave is generated, the plate wave propagates on the substrate, and excites rotational (rotation) vibration in the mirror unit 13. X in the figure is the central axis of the torsion beam 12, and is set at a position shifted from the position of the node of the plate wave amplitude indicated by Amin. FIGS. 1B and 1C show the state of the plate wave and the rotation of the mirror unit 13.

  Non-Patent Document 1 discloses a small optical scanning device of FIG. 1 having a substrate thickness of about 50 μm, a mirror part size of about 1 mm, a beam width of about 100 μm, and an overall size of 10 mm or less. ing. By driving the piezoelectric film 11, the mirror unit 13 vibrates at a frequency exceeding about 20 kHz with a deflection angle of about 40 °.

  When the mirror section 13 having such a configuration is irradiated with laser light, one-dimensional scanning laser light can be generated according to the deflection angle of the mirror section 13.

In the method of Patent Document 1, basically, the connection position of the torsion beam and the substrate and the position of the node of the plate wave generated on the substrate are matched to excite only the torsional vibration in the mirror part. It takes a very long time to start up the upper torsional vibration. Therefore, practically, in order to shorten the rise time, the center of gravity of the mirror is slightly shifted from the position of the torsion beam, and the connection position of the torsion beam and the substrate is set so that vibration in the substrate thickness direction is applied to the torsion beam. It is necessary to shift slightly from the position of the plate wave node.
JP 2006-293116 A Jae-Hyuk Park, et al., MEMS 2006, Istanbul, 19th IEEE Int. Conf., Pp730-733

  When a metal plate is used as the material of the substrate and is shaped by press working, the substrate and the torsion beam are likely to be deformed. In addition, expansion and contraction of the material due to environmental changes such as temperature occur. The deformation of the substrate and the torsion beam causes the surface of the mirror to fall, and becomes a serious problem as with the surface of a conventional polygon mirror.

  Further, in display applications and the like, it is required to perform horizontal and vertical two-dimensional scanning with a single mirror for miniaturization.

  In view of such circumstances, it is an object of the present invention to provide an optical scanning device capable of correcting a rotational axis shift and surface tilt.

In order to solve this problem, for example, an optical scanning device of the present invention has the following configuration. That is,
A mirror part for reflecting the incident light beam;
A substrate on which a pair of beams supporting the mirror portion is formed;
A fixing member for fixing the substrate at an end;
A plurality of vibration sources for vibrating and deforming the substrate;
A drive circuit that generates drive signals for the plurality of vibration sources,
The drive circuit generates drive signals of different frequencies;
With the drive signals of the different frequencies, the mirror portion is rotated and oscillated around the beam by a plate wave accompanied by the deformation of the substrate, and the deformation of the substrate is corrected ,
The drive signal is a signal in which signals having different frequencies are superimposed .

  According to the present invention, by adjusting the static deformation of the substrate, it is possible to correct the position of the mirror axis and the surface tilt of the mirror. Even if there is an error or deformation due to processing, an error in arrangement, deformation due to temperature, or the like, the mirror can be kept in a normal state. Thereby, a high-performance optical scanning device can be configured.

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

  In the following description, a piezoelectric material is used as the vibration source, but the effect of the present invention is not limited to this. Further, the materials and dimensions of the members used such as the vibration source and the substrate, the formation method, and the like can be applied in the same manner as those described in Patent Document 1, but the present invention applies thereto. Of course, it is not limited.

[First Embodiment]
2A and 2B are a top view and a side view of the optical scanning device of the present embodiment. The vibration sources 116 and 117 are disposed on the substrate 100 on which the mirror unit 130 and the torsion beam 120 that supports the mirror unit 130 are formed. One end of the substrate 100 is fixed to the fixing member 160. The vibration sources 116 and 117 are connected to the drive circuits 208 and 209 via electrodes (not shown).

  FIG. 3A shows the deformation of the substrate 100 and the rotational vibration of the mirror 130 due to the plate wave generated by the vibration sources 116 and 117. FIG. 3A is a side view of the optical scanning apparatus 1, in which the length direction of the substrate 100 is an x axis, the substrate thickness direction is a z axis, and a scale in the z axis direction is drawn greatly. The intersection of the substrate 100 and the mirror 130 becomes the position of the twisted beam 120, that is, the rotation axis of the mirror 130. A solid line and a dotted line in FIG. 3A indicate the states at the maximum amplitude of positive and negative, respectively.

  FIG. 3B shows how the substrate 100 is deformed when a DC voltage is applied to the vibration sources 116 and 117. Depending on the polarity of the signal applied to the vibration sources 116 and 117, the signal is warped and deformed in the positive and negative directions of the z-axis as indicated by a solid line or a dotted line.

  Here, when voltages having opposite polarities are applied to the vibration sources 116 and 117, the substrate 100 is twisted and deformed as shown in FIG. 4A, and the surface direction of the mirror 130 can be rotated about the x axis. In FIG. 4A, only the deformation of the base 100 is shown, and the mirror portion and the like are omitted. When voltages of the same polarity are applied to the vibration sources 116 and 117, the substrate 100 is warped and deformed as shown in FIG. 4B, and the position of the rotation axis of the mirror unit 130 in the z direction can be adjusted. is there.

  In the first embodiment, by driving a DC signal superimposed on an AC signal that generates a plate wave, the rotational vibration of the mirror unit 130 can be excited and the surface tilt can be adjusted. Thereby, the scanning line position of the light beam by the plate wave can be finely adjusted in the direction orthogonal to the scanning line, and the beam light can be scanned on the target scanning line.

  The actual driving of the apparatus is as follows.

First, a detection element for detecting the light beam is arranged in advance on a scan scanning line where the light beam is scanned by the rotational vibration of the mirror unit 130. Then, an AC drive signal having a preset frequency is applied to the vibration sources 116 and 117. As a result, the mirror unit 130 vibrates with the torsion beam 120 as a rotation (rotation) axis. Thereafter, the beam light is irradiated toward the mirror unit 130. When the mirror unit 130 is tilted, naturally, the detection element cannot detect the beam light reflected by the mirror unit 130. Therefore, a DC drive signal is superimposed on the vibration sources 116 and 117. The voltage of the DC drive signal superimposed on the vibration sources 116 and 117 is expressed as (voltage applied to the drive source 116, voltage applied to the drive source 117), for example, as follows.
(nV, -nV), ((n-1) V, (-(n-1) V), ..., (-(n-1) V, (n-1) V), (-nV, nV)

  Then, at each stage, the case where the detection element can detect the light beam reflected by the mirror unit 130 (the voltage applied to the drive source 116, the voltage applied to the drive source 117) is applied in a fixed manner. To do.

[Second Embodiment]
FIGS. 5A and 5B are a top view and a side view of the optical scanning device 2 according to the second embodiment of the present invention. The same members as those in FIGS. 2A and 2B are denoted by the same reference numerals. A different point is that vibration sources 110, 111, and 112 are provided instead of the vibration sources 116 and 117. Among them, the vibration source 110, the drive circuit 201 is connected for generating an AC drive signal for use to generate a Lamb wave, the vibration source 111 and 112 DC drive for use in tilt compensation of the mirror portion 130 A drive circuit 202 for generating a signal is connected.

  The deformation of the substrate 100 by the plate wave generated by the vibration source 110 and the state of rotational vibration of the mirror 130 are the same as in FIGS. When the DC voltage is applied to the vibration sources 111 and 112, the deformation of the substrate 100 is as shown in FIGS. 6A and 6B. Depending on the polarity of the signal applied to the vibration sources 111 and 112, a solid line or As indicated by the dotted line, it warps and deforms in the positive and negative directions of the z-axis. In particular, when reverse polarity voltages are applied to the vibration sources 111 and 112, the substrate 100 is twisted and deformed as shown in FIG. 6A, and the surface tilt of the mirror 130 is corrected as in the first embodiment. Can do. In FIGS. 6A and 6B, only the deformation of the base 100 is shown, and the mirror portion and the like are omitted. When voltages of the same polarity are applied to the vibration sources 111 and 112, the substrate 100 is warped and deformed as shown in FIG. 6B, and the position of the rotation axis of the mirror unit 130 in the z direction can be adjusted. is there.

[Explanation of Implementation Examples of First and Second Embodiments]
FIG. 7 shows a block configuration diagram when mounted on a laser beam printer 3 equipped with the optical scanning device of the present invention. In this figure, members similar to those in FIGS. 3 and 6 are denoted by the same reference numerals. Here, a case where the configuration of the second embodiment is used as a basis will be described. However, when the first embodiment is provided, the vibration sources 111 and 112 in the following description are referred to as the vibration sources 116 and 117, respectively. replaced will the vibration source 110 that generates a Lamb wave may be changed to read the vibration source 116 and 117.

  Hereinafter, the operation of each component will be described with reference to the flowchart shown in FIG.

  When the power of the laser beam printer 3 is turned on, the control unit 500 first controls the drive circuit 203 in step S1 to apply an AC drive signal having a preset voltage to the vibration source 110. . At this time, the vibration sources 111 and 112 are not driven. The control unit 500 also controls the entire laser beam printer.

  As a result, the vibration source 110 vibrates according to the given drive signal, generates a plate wave on the substrate 110, and excites the rotational vibration of the mirror unit 130 due to the propagation of the plate wave. Since some time is required until the rotational vibration of the mirror unit 130 is stabilized (equilibrium), the process waits until a preset time elapses (step S2). This time may be set depending on the size of the substrate 100, the size of the mirror unit 130, and the target vibration frequency.

  When the mirror unit 130 rotates and vibrates at a target vibration frequency, the control unit 500 drives the laser light source 300 to emit the laser light 400. As a result, it passes through the laser beam 400 emission optical system 310 and is reflected by the mirror unit 130 that is rotating and oscillating. The reflected laser light scans the beam detection circuit 330 provided on the target scan line of the beam light and the photosensitive drum 800 along the arrow 410 shown in the drawing via the imaging optical system 320. . The reflected laser light scans the beam detection circuit 330 provided on the scanning line of the beam light and the photosensitive drum 800 along the arrow 410 shown in the drawing through the imaging optical system 320.

  However, the above is a case where the mirror unit 130 is not tilted. If the mirror section 130 is tilted, the beam detection circuit 330 does not detect the laser beam at all, or even if it does, the entire area of the diameter of the laser beam is not irradiated to the beam detection circuit 330.

  Therefore, when scanning with laser light is started, the control unit 500 determines in step S3 and S4 whether or not laser light having an appropriate intensity resulting from the tilting of the mirror unit 130 is reflected by the mirror unit 130. judge.

  Specifically, the determination is made as follows.

  First, the intensity of the laser beam immediately after emission is detected by the beam detector 340 provided in the laser light source 300. The intensity of this laser beam is represented as BD0. Next, the intensity of the laser beam is detected by a beam detection circuit 330 provided in the vicinity of the photosensitive drum 800. The intensity of this laser beam is BD1. These BD0 and BD1 are supplied to the comparison calculator 210 (step S3).

  As described above, when the mirror portion in FIG. 2 is tilted, the beam detection circuit 330 does not detect the laser beam at all, or even if it is detected, the intensity of the detected laser beam is the target. It will not be strong.

  Therefore, the comparator 210 determines whether or not the relationship with the preset threshold Th satisfies “BD1 / BD0 ≧ Th” (step S4). This determination result is supplied to the drive circuit 203. The threshold value Th is typically set to “1.0”, but may be a value less than 1 that approximates “1.0” as long as a certain level of surface tilt can be allowed.

  If it is determined that BD1 / BD0 <Th, that is, if only laser light having a target intensity or less is detected, the process proceeds to step S5, the control is performed by the drive circuit 203, and the vibration sources 111, 112 are controlled. In order to cause torsional deformation as shown in FIG. 6A, a DC drive signal is applied. The degree of torsional deformation may be set in stages as described above. Note that a certain amount of time is required until the vibration sources 111 and 112 are stabilized by the application, and therefore, the process waits for that time in step S6. Thereafter, the process returns to step S3.

  Returning to step S3, as described above, the process of detecting BD1 and BD0 again is compared with the threshold value. Here, if it is determined that “BD1 / BD0 <Th”, the correction of the tilting is insufficient, so the process of step S5 is executed again. In the second and subsequent steps of step S5, the drive circuit 203 may be deformed differently from the previous torsional deformation.

  As described above, it is assumed that the relationship “BD1 / BD0 ≧ Th” is established. This means that the surface collapse of the mirror unit 130 is suppressed. Accordingly, the process proceeds to step S7 and shifts to a print standby state. Since the subsequent processing is the same as that of a normal laser beam printer using a polygon mirror, the description thereof is omitted. Note that when the printing process is actually changed, the beam detection circuit 330 functions as a beam detector that determines the scan timing of the laser beam.

  As described above, according to the present embodiment, even when the mirror unit 130 is tilted due to variations in the dimensions of the substrate 100 or positioning when fixed, the tilting of the mirror 130 is corrected. In addition, it is possible to emit a laser beam for scanning with high accuracy.

[Third Embodiment]
9A and 9B are a top view and a side view of the optical scanning device 4 according to the third embodiment of the present invention. The same members as those in the first and second embodiments are denoted by the same reference numerals. The substrate 101 is provided with a torsion beam 121, and the mirror unit 130 is rotatable about the y-axis center in the figure. The mirror part 130 is rotated about the y-axis by the torsion beam 120 due to the plate wave generated by the vibration source 110 as in the first and second embodiments. The vibration sources 111 and 112 are driven by the drive circuits 203 and 204, and are driven at a frequency f2 different from the frequency f1 of the drive circuit 201 of the vibration source 110. The vibration sources 111 and 112 are driven in opposite phases to excite rotational vibration in the torsion beam 121 as shown in FIG. 10, and rotate the mirror portion, not shown in the figure, about the x axis. Here, the vibration due to f2 is not due to a plate wave. Also in this embodiment, similarly to the above embodiment, by superimposing a DC signal on the vibration source, the substrate 101 can be statically deformed, and the mirror axis position adjustment and mirror surface tilt correction can be performed. Is possible.

[Fourth Embodiment]
FIGS. 11A and 11B are a top view and a side view of the optical scanning device 5 according to the fourth embodiment of the present invention. The same members as those in the above embodiment are denoted by the same reference numerals. Twist beams 121 and 122 are formed on the substrate 102, and both sides are supported by fixing members 160 and 161. Vibration sources 110 and 113 for generating plate waves are disposed on both sides of the mirror unit 130. Further, the vibration sources 111, 112, and 122 for exciting rotational vibrations in the torsion beams 121 and 121, and 114 and 115 are arranged. The driving method is the same as that of the third embodiment, and the vibration sources 114 and 115 are driven in opposite phases by the driving circuits 206 and 207.

[Fifth Embodiment]
12A and 12B are a top view and a side view of the optical scanning device 6 according to the fourth embodiment of the present invention. The same members as those in the above embodiment are denoted by the same reference numerals. In the present embodiment, the vibration sources 111, 112, 114, and 115 are excited by plate waves to excite rotational vibration in the torsion beam 120, and the torsion beams 121 and 122 are excited in rotation vibration. The operation similar to that of the fourth embodiment is enabled by applying the vibration of the frequency f2 in a superimposed manner.

[Description of Implementation Examples of Third to Fifth Embodiments]
FIG. 13 shows a configuration in which the present invention is mounted on a two-dimensional scanning device (a display is a typical device). The same members as those in the above embodiment are denoted by the same reference numerals. Although the illustration of the vibration source and the like is omitted, the same mirror driving unit as that shown in FIG. 9, FIG. 11 or FIG. 12 can be used. The laser light emitted from the light source 300 is scanned in the horizontal and vertical directions and irradiated on the screen 810. The drive signals of the drive circuits 203 to 207 are adjusted by the output signals of the BD sensor 330 and 331 to control the rotation angle of the mirror 130, and the light source 300 is controlled by the driver circuit 220 in synchronization with the optical scanning. The image is drawn on the screen 810. The BD sensors 330 and 331 are provided on the horizontal axis and the vertical axis that pass through the center point of the two-dimensional scan region. Then, after the rotational vibration of the mirror unit 130 is performed and an appropriate beam light is detected by the BD sensor 330, the rotational vibration of the mirror unit 130 is stopped and the depth sources 111 to 115 are driven in the vertical direction. Control to detect the proper beam light to be scanned. After this, a two-dimensional scan may be performed.

  In the above-described embodiment, an example in which a piezoelectric element is used as a drive source has been described. However, the type of element is not limited as long as the element generates a plate wave. For example, a magnetostrictive element (an element that vibrates by applying an alternating magnetic field) may be used instead of the piezoelectric element.

  The optical scanning device of the present invention can also be applied to a scanner (image reading device) that scans light on a document and reads the document, a barcode reader that reads a barcode, and the like.

It is a figure for demonstrating the structure of the conventional optical scanning device, and its drive state. It is a figure which shows the upper side figure and side view of the optical scanning device in 1st Embodiment. It is a figure which shows the mode of a vibration of the board | substrate of the optical scanning device in 1st Embodiment. It is a figure which shows a mode that the twist and curvature by the drive signal of the direct current component applied to two vibration sources in 1st Embodiment generate | occur | produce. It is a figure which shows the upper side figure and side view of the optical scanning device in 2nd Embodiment. It is a figure which shows a mode that the twist and curvature by the drive signal of the DC component applied to two vibration sources in 2nd Embodiment generate | occur | produce. It is a figure which shows the structure concerning beam light scanning at the time of applying 1st, 2nd embodiment to a laser beam printer. It is a flowchart which shows the process sequence of the control at the time of applying to the laser beam printer of FIG. It is a figure which shows the upper side figure and side view of the optical scanning device in 3rd Embodiment. It is a figure which shows a mode that the torsional vibration by the drive signal applied to two vibration sources in 3rd Embodiment generate | occur | produces. It is a figure which shows the upper side figure and side view of the optical scanning device in 4th Embodiment. It is a figure which shows the upper side figure and side view of the optical scanning device in 5th Embodiment. It is a figure which shows the structure at the time of applying 3rd thru | or 5th embodiment to a two-dimensional scanning apparatus.

Claims (6)

A mirror part for reflecting the incident light beam;
A substrate on which a pair of beams supporting the mirror portion is formed;
A fixing member for fixing the substrate at an end;
A plurality of vibration sources for vibrating and deforming the substrate;
A drive circuit that generates drive signals for the plurality of vibration sources,
The drive circuit generates drive signals of different frequencies;
With the drive signals of the different frequencies, the mirror portion is rotated and oscillated around the beam by a plate wave accompanied by the deformation of the substrate, and the deformation of the substrate is corrected,
The drive signal includes an optical scanning device which is a signal obtained by superimposing signals of different frequencies. A mirror part for reflecting the incident light beam;
A substrate on which a pair of beams supporting the mirror portion is formed;
A fixing member for fixing the substrate at an end;
A plurality of vibration sources for vibrating and deforming the substrate;
A drive circuit that generates drive signals for the plurality of vibration sources,
The drive circuit generates drive signals of different frequencies;
With the drive signals of the different frequencies, the mirror portion is rotated and oscillated around the beam by a plate wave accompanied by the deformation of the substrate, and the deformation of the substrate is corrected,
The plurality of vibration sources are at least two vibration elements that range in the axial direction of the beam on the substrate,
An optical scanning device, wherein a torsion of the substrate with respect to the fixing member is corrected by applying a DC voltage of opposite polarity to each of the two vibration elements. Beam light detection means provided on a scan line in the vicinity of the scan object for detecting the beam light reflected by the mirror unit;
Determination means for determining whether or not the light intensity detected by the light beam detection means is greater than or equal to a preset threshold;
When the determination unit determines that the light beam intensity is less than a preset threshold value, the drive circuit corrects the twist of the substrate with respect to the fixing member by applying the DC voltage. The optical scanning device according to claim 2 . A mirror part for reflecting the incident light beam;
A substrate on which a pair of beams supporting the mirror portion is formed;
A fixing member for fixing the substrate at an end;
A plurality of vibration sources for vibrating and deforming the substrate;
A control method of an optical scanning device having a drive circuit that generates drive signals for the plurality of vibration sources,
The drive circuit generates drive signals of different frequencies;
With the drive signals of the different frequencies, the mirror portion is rotated and oscillated around the beam by a plate wave accompanied by the deformation of the substrate, and the deformation of the substrate is corrected ,
The method of controlling an optical scanning device, wherein the drive signal is a signal in which signals of different frequencies are superimposed . Image reading apparatus characterized by comprising an optical scanning device according to any one of claims 1 to 3. Display apparatus comprising the optical scanning apparatus according to any one of claims 1 to 3.

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