JP2009009093A - Image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display apparatus capable of displaying a stable image with ease by raster scanning of a beam associated with resonant oscillation in a main scanning direction. <P>SOLUTION: The image display apparatus capable of displaying an image on a plane of projection by raster scanning of the beam associated with resonant oscillation in a horizontal scanning direction (the main scanning direction), includes a resonance-point detector for detecting a mechanical resonant frequency in the horizontal scanning direction. Out of frequencies fp1 to fp4 and fm1 to fm3 that are multiples of a vertical synchronizing frequency fv in image display, for example a frequency nearest to the mechanical resonant frequency fo detected in the resonance-point detector is determined as a horizontal scanning frequency of the raster scanning. The image display apparatus can thus provide a stable image display with ease. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays.

  Optical scanners that deflect and scan light beams such as laser light are used in optical devices such as barcode readers, laser printers, and displays. Some of these optical scanners include a polygon mirror that scans reflected light by rotating a polygonal column mirror with a motor, and a galvano mirror that rotates and vibrates a plane mirror using an electromagnetic actuator. However, in such an optical scanner, a mechanical drive mechanism for driving the mirror by a motor or an electromagnetic actuator is required. However, since the drive mechanism is relatively large and expensive, There is a problem in that downsizing is hindered and the price is increased.

  Therefore, in order to reduce the size, price, and productivity of optical scanners, components such as mirrors and elastic beams are integrated using micromachining technology that microfabricates silicon and glass using semiconductor manufacturing technology. Development of molded micro light scanner is progressing.

  There is an image display apparatus in which two sets of the above-described optical scanners are arranged and a two-dimensional image is displayed on a projection surface by raster scanning the light beam reflected by each mirror.

  In such an image display device, stable image display is possible by synchronizing between an image signal related to a display image and raster scanning (horizontal scanning and vertical scanning). However, in order to obtain a horizontal scanning output with a large width, in the horizontal scanning in which the resonance vibration of the mirror part is generally performed, the resonance frequency (horizontal scanning frequency) related to this resonance vibration and the horizontal synchronization frequency of the image signal are matched to be synchronized. It is not easy to take. As techniques for achieving this synchronization, for example, the following (i) to (iii) are known.

  (i) At the design stage and the manufacturing stage of the optical scanner, the resonance frequency is set so as to substantially coincide with the horizontal synchronization frequency of the image signal.

  (ii) An image frame (image signal) is temporarily stored in a buffer memory, and a read clock is generated from a horizontal scanning drive signal that performs resonance vibration using a PLL circuit, and the above-described buffer is based on this clock. The image signal of each horizontal line is read from the memory (see, for example, Patent Document 1).

  (iii) An optical scanner having a structure capable of adjusting the resonance frequency is used. For example, as in the technique disclosed in Patent Document 2, the resonance frequency is adjusted by changing the moment of inertia of the vibrating body by bending the flexible arm extending from the vibrating body (mirror part) by applying an electric field. .

JP-A-11-146222 Special table 2004-518992 gazette

  However, in the technique (i), the horizontal scanning output (horizontal scanning width) may change drastically when the resonance frequency fluctuates due to environmental changes such as temperature or changes over time, and the horizontal scanning direction (main scanning direction). In addition, stable image display becomes difficult in raster scanning of light rays accompanied by resonance vibration.

  On the other hand, in the technique (ii), the above-described PLL circuit or the like is necessary, and the apparatus configuration is complicated.

  In the technique (iii), the resonance frequency can be adjusted, but the structure for the adjustment becomes complicated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image display device that can easily perform stable image display in raster scanning of light beams accompanied by resonance vibration in the main scanning direction.

  In order to solve the above problem, the invention of claim 1 is an image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays, and (a) a light beam emitted from a predetermined light source. A first actuator that swings a movable part having a reflective surface about a first axis; and (b) swings the movable part about a second axis that intersects the first axis substantially perpendicularly. A second actuator to be moved, and (c) driving the first actuator based on a first drive signal repeated at a first frequency to cause the movable portion to oscillate and vibrate around the first axis. (D) main scanning means for scanning the light beam reflected by the reflecting surface in the main scanning direction related to the raster scanning; and (d) driving the second actuator based on a second driving signal repeated at a second frequency to Rocking the movable part about two axes And a sub-scanning unit that scans the light beam reflected by the reflecting surface in the sub-scanning direction related to the raster scan, wherein the main scanning unit includes (c-1) a resonance frequency related to oscillation vibration of the movable unit. And (c-2) a setting unit that sets a frequency near the resonance frequency among the specific frequencies calculated based on the second frequency as the first frequency. Have.

  According to a second aspect of the present invention, in the image display device according to the first aspect of the invention, the specific frequency is n times the second frequency (where n is a natural number).

  According to a third aspect of the present invention, in the image display device according to the first or second aspect of the invention, the specific frequency is (n + 0.5) times the second frequency (where n is a natural number). .

  According to a fourth aspect of the present invention, in the image display device according to any one of the first to third aspects of the present invention, the setting means sets a frequency closest to the resonance frequency among the specific frequencies. Means for setting as the first frequency.

  According to a fifth aspect of the present invention, in the image display device according to any one of the first to fourth aspects, the main scanning means is calculated based on the second frequency as the first drive signal. In addition to signal generation means for generating each drive signal repeated at each of a plurality of frequencies, the detection means drives the first actuator based on each drive signal generated by the signal generation means to perform the first Means for detecting a frequency corresponding to the resonance frequency by causing the movable portion to oscillate and oscillate about an axis and comparing the amplitude of the oscillating angle of the movable portion in each drive signal.

  According to a sixth aspect of the present invention, in the image display device according to any one of the first to fourth aspects, the main scanning means is calculated based on the second frequency as the first drive signal. In addition to signal generation means for generating each drive signal repeated at each of a plurality of frequencies, the detection means drives the first actuator based on each drive signal generated by the signal generation means to perform the first Means for detecting a frequency corresponding to the resonance frequency by causing the movable part to oscillate around the axis and comparing the phase of the oscillating angle of the movable part in each drive signal.

  According to a seventh aspect of the present invention, in the image display device according to any one of the first to sixth aspects, the frequency detected by the detecting means is a frequency calculated based on the second frequency. .

  According to an eighth aspect of the present invention, in the image display device according to any one of the first to seventh aspects, the setting means is configured to change the first frequency according to a change in a resonance frequency detected by the detection means. There is a change means for changing the frequency, and the phase of the swing angle of the movable part in each drive signal repeated at each of the first frequencies before and after the change by the change means is substantially equal.

  The invention according to claim 9 is an image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays, and (a) has a reflection surface that reflects light rays emitted from a predetermined light source. A first actuator that swings the movable portion around a first axis; and (b) a second actuator that swings the movable portion around a second axis that substantially intersects the first axis. And (c) the first actuator is driven based on the first drive signal repeated at the first frequency, and the movable part is oscillated and oscillated around the first axis, thereby being reflected by the reflecting surface. Main scanning means for scanning a light beam in the main scanning direction according to the raster scanning; and (d) the second actuator driven based on a second driving signal repeated at a second frequency to move the second actuator around the second axis. By swinging the part, the reflective surface Sub-scanning means for scanning the emitted light beam in the sub-scanning direction related to the raster scanning, the main scanning means (c-1) among the specific frequencies calculated based on the second frequency, A setting unit configured to set a frequency near a resonance frequency related to the oscillation vibration of the movable portion as the first frequency;

  According to a tenth aspect of the present invention, there is provided an image display device capable of displaying an image on a predetermined projection surface by raster scanning of a light beam, wherein: (a) a first reflection that reflects a light beam emitted from a predetermined light source; A first actuator for swinging a first movable part having a surface about a first axis; and (b) a second actuator having a second reflecting surface for reflecting the light beam reflected by the first reflecting surface. A second actuator that swings the movable portion about the second axis; and (c) the first actuator is driven based on a first drive signal repeated at a first frequency to move the first actuator about the first axis. Main scanning means for scanning the light beam reflected by the first reflecting surface in the main scanning direction according to the raster scanning by oscillating and vibrating the first movable part; and (d) a second frequency repeated at the second frequency. And driving the second actuator based on the two drive signals to Sub-scanning means for scanning the light beam reflected by the second reflecting surface in the sub-scanning direction related to the raster scanning by swinging the second movable portion around an axis, and the main scanning means (C-1) setting means for setting, as the first frequency, a frequency near a resonance frequency related to oscillation vibration of the first movable part among the specific frequencies calculated based on the second frequency.

  The invention of claim 11 is an image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays, and (a) a first reflection that reflects light rays emitted from a predetermined light source. A first actuator for swinging a first movable part having a surface about a first axis; and (b) a second actuator having a second reflecting surface for reflecting the light beam reflected by the first reflecting surface. A second actuator that swings the movable portion around the second axis; and (c) the second actuator is driven based on a first drive signal repeated at a first frequency, and the second actuator is moved around the second axis. Main scanning means for scanning the light beam reflected by the second reflecting surface in the main scanning direction according to the raster scanning by oscillating and vibrating the second movable part; and (d) a second frequency repeated at the second frequency. The first actuator is driven based on the two drive signals to Sub-scanning means for scanning the light beam reflected by the first reflecting surface in the sub-scanning direction related to the raster scanning by swinging the first movable portion around an axis, and the main scanning means (C-1) setting means for setting, as the first frequency, a frequency near a resonance frequency related to oscillation vibration of the second movable part among the specific frequencies calculated based on the second frequency.

  The invention of claim 12 is an image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays, and (a) has a reflection surface for reflecting light rays emitted from a predetermined light source. First swing means for swinging the movable part around the first axis, and second swing means for swinging the movable part around a second axis that intersects the first axis substantially perpendicularly. And (b) reflecting on the reflecting surface by oscillating and oscillating the movable part around the first axis using the first oscillating means based on a first drive signal repeated at a first frequency. A main scanning means for scanning the emitted light beam in the main scanning direction related to the raster scanning, and (d) around the second axis using the second swinging means based on the second drive signal repeated at the second frequency. Light beam reflected by the reflecting surface by swinging the movable part Sub-scanning means for scanning in the sub-scanning direction related to the raster scanning, wherein the main scanning means (c-1) swings the movable part among the specific frequencies calculated based on the second frequency. Setting means for setting a frequency near a resonance frequency related to vibration as the first frequency.

  According to the first to eighth aspects of the present invention, the first actuator is driven based on the first drive signal repeated at the first frequency, and the movable section is oscillated and oscillated around the first axis. The light beam reflected by the reflecting surface is scanned in the main scanning direction related to raster scanning, and the second actuator is driven based on the second driving signal repeated at the second frequency to swing the movable portion around the second axis. By moving, the light beam reflected by the reflecting surface of the movable part is scanned in the sub-scanning direction related to raster scanning. Then, a frequency corresponding to the resonance frequency related to the oscillation vibration of the movable part is detected, and a frequency near the resonance frequency among the specific frequencies calculated based on the second frequency is set as the first frequency. As a result, stable image display can be easily performed in raster scanning of light beams accompanied by resonance vibration in the main scanning direction.

  In particular, in the second aspect of the invention, since the specific frequency is n times the second frequency (where n is a natural number), an appropriate first frequency can be easily determined.

  In the invention of claim 3, since the specific frequency is (n + 0.5) times the second frequency (where n is a natural number), an appropriate first frequency can be easily determined.

  In the invention of claim 4, since the frequency closest to the resonance frequency among the specific frequencies is set as the first frequency, a large oscillating vibration is obtained in the movable part.

  In the invention of claim 5, the first actuator is driven based on each drive signal repeated at each of a plurality of frequencies calculated based on the second frequency, and the movable part is oscillated and oscillated around the first axis. The frequency corresponding to the resonance frequency is detected by comparing the amplitude of the swing angle of the movable part in each drive signal. As a result, the resonance frequency can be detected efficiently.

  According to a sixth aspect of the invention, the first actuator is driven based on each drive signal repeated at each of a plurality of frequencies calculated based on the second frequency, and the movable portion is oscillated and oscillated around the first axis. The frequency corresponding to the resonance frequency is detected by comparing the phase of the swing angle of the movable part in each drive signal. As a result, the resonance frequency can be detected efficiently.

  In the invention of claim 7, since the frequency detected by the detection means is a frequency calculated based on the second frequency, the resonance frequency can be detected efficiently.

  In the invention according to claim 8, when the first frequency is changed in accordance with the change in the resonance frequency detected by the detecting means, the movable portion of each drive signal repeated at each of the first frequencies before and after the change is changed. Since the phase of the swing angle is substantially equal, more stable image display can be performed.

  According to the ninth aspect of the present invention, the first actuator is driven based on the first drive signal repeated at the first frequency, and the movable part is oscillated and oscillated around the first axis, thereby reflecting the movable part. The light beam reflected by the surface is scanned in the main scanning direction related to raster scanning, and the second actuator is driven based on the second driving signal repeated at the second frequency to swing the movable portion around the second axis. Thus, the light beam reflected by the reflecting surface of the movable part is scanned in the sub-scanning direction related to the raster scanning. And among the specific frequencies calculated based on the second frequency, a frequency near the resonance frequency related to the oscillation vibration of the movable part is set as the first frequency. As a result, stable image display can be easily performed in raster scanning of light beams accompanied by resonance vibration in the main scanning direction.

  According to the tenth aspect of the present invention, the first actuator is driven based on the first drive signal repeated at the first frequency, and the first movable portion is oscillated and oscillated around the first axis. The light beam reflected by the first reflecting surface of the movable portion is scanned in the main scanning direction related to the raster scanning, and the second actuator is driven based on the second driving signal repeated at the second frequency to rotate around the second axis. By swinging the second movable portion, the light beam reflected by the second reflecting surface of the second movable portion is scanned in the sub-scanning direction related to raster scanning. And among the specific frequencies calculated based on the second frequency, a frequency near the resonance frequency related to the oscillation vibration of the first movable part is set as the first frequency. As a result, stable image display can be easily performed in raster scanning of light beams accompanied by resonance vibration in the main scanning direction.

  According to the eleventh aspect of the present invention, the second actuator is driven based on the first drive signal repeated at the first frequency, and the second movable part is oscillated and oscillated around the second axis. The light beam reflected by the second reflecting surface of the movable part is scanned in the main scanning direction related to the raster scanning, and the first actuator is driven based on the second driving signal repeated at the second frequency to rotate around the first axis. By swinging the first movable portion, the light beam reflected by the first reflecting surface of the first movable portion is scanned in the sub-scanning direction related to raster scanning. And among the specific frequencies calculated based on the second frequency, a frequency near the resonance frequency related to the oscillation vibration of the second movable part is set as the first frequency. As a result, stable image display can be easily performed in raster scanning of light beams accompanied by resonance vibration in the main scanning direction.

  According to the twelfth aspect of the present invention, the light reflected from the reflecting surface of the movable portion is rastered by oscillating and vibrating the movable portion around the first axis based on the first drive signal repeated at the first frequency. Raster scanning of the light beam reflected by the reflecting surface of the movable portion by scanning in the main scanning direction related to scanning and swinging the movable portion around the second axis based on the second drive signal repeated at the second frequency. Scan in the sub-scanning direction. And among the specific frequencies calculated based on the second frequency, a frequency near the resonance frequency related to the oscillation vibration of the movable part is set as the first frequency. As a result, stable image display can be easily performed in raster scanning of light beams accompanied by resonance vibration in the main scanning direction.

<First Embodiment>
<Configuration of image display device>
FIG. 1 is a diagram showing an appearance of an image display device 100A according to the first embodiment of the present invention.

  The image display device 100 </ b> A has a box shape and is configured as a projector device that projects an image (image) on the screen 9. In the image display device 100A, a two-dimensional image can be displayed on the screen 9 by performing raster scanning RS of light rays that are irradiated toward the screen 9 that is the projection surface. In this raster scanning RS, for example, light is continuously scanned from the start position Qa at the upper end of the display image to the end position Qb at the lower end of the display image, whereby one image display is completed. When the light beam is scanned to the position Qb, vertical scanning (and horizontal scanning) for returning to the position Qa for the next image display is performed during a vertical blanking period without image display.

  In the image display apparatus 100A, an optical scanner 1 shown in FIG. 2 and a light source 50 that emits a light beam (for example, laser light) LT toward the optical scanner 1 are provided.

  The optical scanner 1 is centered on a first axis Ay parallel to the Y axis (see FIG. 6) and a second axis Ax parallel to the X axis (see FIG. 6) and intersecting the first axis Ay at a substantially right angle. A mirror unit 11 capable of rotating is provided. The mirror unit 11 rotates two-dimensionally about the first axis Ay and the second axis Ax, so that the light beam LT from the light source 50 reflected by the mirror unit 11 can be raster-scanned RS. A specific configuration of the optical scanner 1 will be described in detail later.

  FIG. 3 is a block diagram illustrating a functional configuration of the image display apparatus 100A.

  The image display apparatus 100A includes the optical scanner 1 and the light source 50 described above, an optical scanner control unit 6 that controls the driving of the optical scanner 1, and a light source driving circuit 51 that drives the light source 50 and can modulate the light beam LT. And an image signal control unit 52 for controlling the light source driving circuit 51.

  The optical scanner control unit 6 includes a horizontal drive control unit 6a that controls rotation around the first axis Ay (FIG. 2) with respect to the mirror unit 11, that is, horizontal driving, and a second axis Ax (FIG. 2) with respect to the mirror unit 11. ) And a vertical drive control unit 6b for controlling rotation in the vertical direction, that is, driving in the vertical direction. The horizontal drive control unit 6a will be described in detail later.

  The image signal control unit 52 generates a control signal for controlling the light source 50 based on, for example, an image signal input from the outside of the image display device 100A. Based on the control signal, the light source 50 is controlled via the light source drive circuit 51 (for example, lighting / extinguishing control or light emission intensity control), whereby an appropriate image display based on the input image signal is displayed on the screen 9. You can do it. The image signal control unit 52 will be described in detail later.

  In addition, the image display device 100A includes an angle detection unit 55 that detects an angle (displacement angle) of the mirror unit 11 that swings about the first axis Ay (FIG. 2), and a resonance point related to the oscillation vibration of the mirror unit 11. And a resonance point detector 56 for detecting (resonance frequency).

  The angle detection unit 55 has a photo reflector (PR) 550 shown in FIG. 4 as a position detection sensor. And the angle of the mirror part 11 is detected by detecting the position where the light beam LP reflected by the back surface Sb (described later) of the mirror part 11 is incident on the photo reflector 550.

  Further, the angle detection unit 55 can detect the amplitude of the oscillating mirror unit 11 using the angle information of the mirror unit 11 obtained by the photo reflector 550. The amplitude detection of the mirror unit 11 will be described below.

  Since the displacement angle of the mirror portion 11 that performs oscillating vibration is expressed as a waveform of simple vibration as shown in FIG. 5, the envelope EN (dashed line portion) of the waveform indicates the amplitude of the displacement angle of the mirror portion 11. . Therefore, the amplitude of the displacement angle of the mirror unit 11 can be detected by detecting the maximum amplitude using the peak detection circuit or demodulating the envelope EN using the detection circuit, for example.

  Further, the angle detection unit 55 can detect the phase of the oscillating mirror unit 11 using the angle information of the mirror unit 11 obtained by the photo reflector 550. Specifically, the phase difference of the detection signal output from the photoreflector 550 is detected based on the phase of the drive signal generated by the horizontal scanning frequency signal generator 63 (described later), so that the mirror 11 The phase of the displacement angle can be detected.

  The resonance point detection unit 56 detects the mechanical resonance frequency related to the oscillation vibration of the mirror unit 11 based on the amplitude and phase of the displacement angle of the mirror unit 11 detected by the angle detection unit 55. For example, when the mirror unit 11 is oscillated and oscillated in turn with drive signals of frequency groups fp1 to fp3 and fm1 to fm3 (FIG. 14) to be described later, the frequency at which the amplitude of the displacement angle of the mirror unit 11 is maximized is set. Judged as the frequency corresponding to the machine resonance frequency.

  Below, the principal part structure of the optical scanner 1 is demonstrated.

<Configuration of essential parts of optical scanner 1>
FIG. 6 is a plan view showing the main configuration of the optical scanner 1. FIG. 7 is a cross-sectional view seen from the position VII-VII in FIG.

  The optical scanner 1 includes a frame portion 10 that is configured as a “B” -shaped plate-like member and is fixed to a housing (not shown) and the like. "-Shaped holding member 12. Further, in the optical scanner 1, the holding member 12 is connected to the frame 10 via the vibrating portion 2 and the mirror portion 11 is connected to the holding member 12 by the torsion bar portions 13 and 14 that perform elastic deformation.

  The mirror unit 11 has a disk shape, and the front surface Sa and the back surface Sb function as a reflecting surface that reflects the light beam LT emitted from the light source 50. That is, a reflective film made of a metal thin film such as gold or Al (aluminum) is formed on the front surface Sa and the back surface Sb of the mirror unit 11 so that the reflectance of incident light is improved.

  The torsion bar portion 13 includes two torsion bars 13a and 13b extending from the holding member 12 to the vibration portion 2 along the first axis Ay of the mirror portion 11 parallel to the Y axis. By such a torsion bar portion 13, the holding member 12 that holds the mirror portion 11 is elastically supported with respect to the vibration portion 2.

  Similarly, the torsion bar portion 14 includes two torsion bars 14a and 14b extending from both end portions of the mirror portion 11 to the holding member 12 along the second axis Ax of the mirror portion 11 parallel to the X axis. .

  The vibration unit 2 includes bent beams 21 and 22 as plate-like members connected to the torsion bar 13a, and bent beams 23 and 24 as plate-like members connected to the torsion bar 13b. The bending beams 21 to 24, the frame portion 10, the mirror portion 11, the holding member 12, and the torsion bars 13a, 13b, 14a, and 14b are integrally formed by, for example, anisotropic etching of a silicon substrate. .

  In addition, the vibration unit 2 includes piezoelectric elements 31 to 34 as electro-mechanical conversion elements attached to the upper surfaces of the bending beams 21 to 24 with, for example, an adhesive. The piezoelectric elements 31 to 34 are configured as piezoelectric vibrators (piezoelectric actuators) that swing the mirror portion 11 about the first axis Ay. The piezoelectric elements 31 to 34 and the bending beams 21 to 24 Four unimorph portions Ua to Ud are formed.

  Each of the piezoelectric elements 31 to 34 is provided with an upper electrode Eu and a lower electrode Ed on the front surface and the back surface (FIG. 7). The upper electrodes Eu of the piezoelectric elements 31 to 34 are electrically connected to electrode pads 31u to 34u provided on the frame unit 10 through wires, for example, and the lower electrodes of the piezoelectric elements 31 to 34 are connected to each other. The electrode pads 31d to 34d provided on the frame portion 10 are electrically connected to Ed via wires, for example. A drive voltage can be applied to each of the piezoelectric elements 31 to 34 from the outside of the optical scanner 1 through such an electrode pad.

  With the configuration of the optical scanner 1 as described above, bending deformation occurs in the bending beams 21 to 24 by applying a driving voltage to the piezoelectric elements 31 to 34 via the electrode pads 31u to 34u and 31d to 34d. As a result of the bending of the bending beams 21 to 24 in this way, a rotational torque is applied around the first axis Ay to the mirror unit 11 via the torsion bars 13a and 13b and the holding member 12, and the mirror unit functions as a movable unit. 11 can be oscillated around the first axis Ay. The oscillation vibration operation of the mirror unit 11 will be described in detail.

  FIG. 8 is a diagram for explaining the oscillation vibration operation of the mirror unit 11. Here, FIG. 8A and FIG. 8B correspond to FIG. 7 showing a cross section viewed from the VI-VI position in FIG. In FIG. 8A and FIG. 8B, the holding member 12 is not shown for convenience of explanation.

  In the optical scanner 1, the piezoelectric elements 31 to 34 expand and contract by applying an AC voltage in a range in which no polarization inversion occurs between the upper electrode Eu and the lower electrode Ed to the piezoelectric elements 31 to 34, and the unimorphs expand and contract. Therefore, it will be displaced in the thickness direction.

  Therefore, by applying a driving voltage that extends in the longitudinal direction (X-axis direction) to the piezoelectric element 31 and applying a driving voltage having an opposite phase to the driving voltage to the piezoelectric element 32, the piezoelectric element 32 is contracted. In the unimorph portions Ua and Ub whose one ends are connected to the frame portion 10, the bending beam 21 is bent downward as shown in FIG. 8A, while the bending beam 22 is bent upward. Similarly, by applying a drive voltage having the same phase as that of the piezoelectric element 31 and the piezoelectric element 32 to the piezoelectric element 33 and the piezoelectric element 34, the bending beam 23 is bent downward, while the bending beam 24 is moved upward. To bend. As a result, a rotational torque around the first axis Ay is generated in the mirror section 11 via the torsion bars 13a and 13b. Therefore, as shown in FIG. 8A, the mirror section 11 is inclined in the direction Da with the first axis Ay as the center. It will be.

  Further, by applying a driving voltage that extends in the longitudinal direction (X-axis direction) to the piezoelectric element 32, and applying a driving voltage having an opposite phase to the driving voltage to the piezoelectric element 31, the piezoelectric element 31 is contracted. In the unimorph portions Ua and Ub whose one ends are connected to the frame portion 10, the bending beam 21 is bent upward as shown in FIG. 8B, while the bending beam 22 is bent downward. Similarly, by applying a drive voltage having the same phase as that of the piezoelectric element 31 and the piezoelectric element 32 to the piezoelectric element 33 and the piezoelectric element 34, the bending beam 23 is bent upward, while the bending beam 24 is moved downward. To bend. As a result, a rotational torque around the first axis Ay is generated in the mirror section 11 via the torsion bars 13a and 13b. Therefore, as shown in FIG. 8B, the mirror section 11 rotates in the rotation direction Db about the first axis Ay. Will be inclined.

  In this way, if the AC drive voltage for rotating the mirror portion 11 in the direction Da (FIG. 8A) and the direction Db (FIG. 8B) is applied to the piezoelectric elements 31 to 34, this application is performed. Since the vertical vibration following the voltage is repeated in the unimorph portions Ua to Ud, a seesaw-like rotational torque is generated in the torsion bars 13a and 13b, and the mirror portion 11 swings within a predetermined angle range via the holding member 12. It will vibrate. That is, by driving the piezoelectric elements 31 to 34 based on a drive signal (see FIG. 10) repeated at the horizontal scanning frequency (first frequency) and swinging and vibrating the mirror unit 11 about the first axis Ay, The light beam LT reflected by the eleven reflecting surfaces can be scanned in the horizontal direction (main scanning direction) according to the raster scanning RS (FIG. 2).

  Here, when the swing angle of the mirror unit 11 is small, the mirror unit 11 is configured to set the frequency of the AC voltage applied to the piezoelectric elements 31 to 34 to the resonance frequency of the mechanical vibration system related to the optical scanner 1. Due to the resonance vibration, the optical scanner 1 can obtain a large deflection angle (optical scanning angle).

  Further, as shown in FIG. 6, the optical scanner 1 is provided with four piezoelectric elements (piezoelectric actuators) 35 to 38 corresponding to the piezoelectric elements 31 to 34 on the holding member 12, and thereby the above-described first element. Similar to the axis Ay, the mirror portion 11 can be swung around the second axis Ax. That is, by driving the piezoelectric elements 35 to 38 on the holding member 12 and swinging the mirror unit 11 about the second axis Ax, the light beam reflected by the reflecting surface of the mirror unit 11 is raster scanned RS (FIG. 1). ) In the vertical direction (sub-scanning direction). In this way, the piezoelectric elements 35 to 38 function as means for swinging the mirror part 11 about the second axis Ax (second swinging means), and the mirror part 11 about the first axis Ay as described above. The piezoelectric elements 31 to 34 functioning as the means for oscillating (first oscillating means) constitute an actuator section necessary for the raster scanning RS of the light beam.

  Hereinafter, the horizontal drive control unit 6a for driving the mirror unit 11 of the optical scanner 1 in the horizontal direction (around the first axis Ay) at the resonance frequency related to the mechanical resonance will be described.

<About the horizontal drive control unit 6a>
FIG. 9 is a block diagram for explaining a main configuration of the horizontal drive control unit 6a.

  The horizontal drive control unit 6 a includes a horizontal drive circuit 61 that applies a voltage to the piezoelectric elements 31 to 34 to drive the optical scanner 1 in the horizontal direction (around the first axis Ay), and a horizontal read frequency signal generation unit 62. And a horizontal scanning frequency signal generator 63.

  The horizontal readout frequency setting unit 62 sets a horizontal readout frequency frh (described later) based on the mechanical resonance frequency obtained by the resonance point detection unit 56 from the displacement angle of the mirror unit 11 detected by the angle detection unit 55. Information on the horizontal readout frequency frh set by the horizontal readout frequency setting unit 62 is input to the horizontal scanning frequency setting unit 63.

  The horizontal scanning frequency signal generator 63 outputs a single vibration drive signal as shown in FIG. 10, for example, for driving the optical scanner 1 in the horizontal direction. This drive signal is, for example, a signal that is repeated at half the horizontal readout frequency frh set by the readout frequency setting unit 62 and has a frequency component near the mechanical resonance frequency related to the oscillation vibration of the mirror unit 11. It is configured.

  Here, in order to fix the raster scanning RS of the light beam LT by the optical scanner 1 in each image display, the horizontal synchronizing frequency fh and the vertical synchronizing frequency fv of the image signal set by the horizontal reading frequency setting unit 62 are set. The following relationship (1) must be satisfied when the number of horizontal scanning lines (number of lines) is n (n is an integer).

fh = fv · n (1):
For example, in the case of performing image display in accordance with the image display standard of XGA (display pixel number 1024 × 768, horizontal all pixels 1344), the vertical synchronization frequency fv = 60 Hz, the horizontal scanning line number n = 806 (of these, the image display line) If the number q is 768), the horizontal synchronization frequency fh is 48.36 kHz according to the above equation (1).

<Regarding Image Signal Control Unit 52>
In the image display device 100A, in order to secure the brightness of the display screen while minimizing the output of the light source 50, the image is reciprocally displayed in the horizontal scan of the raster scan RS. The configuration of the image signal control unit 52 for performing reciprocal display of the image will be described below.

  FIG. 11 is a diagram for explaining a main configuration of the image signal control unit 52. Note that the thick line in FIG. 11 indicates the flow of the image signal.

  The image signal controller 52 includes a FIFO (First In Fast Out) line memory 521, a FILO (First In Last Out) line memory 522, a changeover switch 523, a FIFO frame memory 524, It has.

  The FIFO line memory 521 delays image data for one horizontal line by one horizontal time (= reciprocal of the horizontal readout frequency frh), for example, for an image signal (hereinafter also referred to as “input image data”) input from the outside. Output.

  On the other hand, the FILO line memory 522 inverts the data arrangement related to the image data for one horizontal line for the input image data, and outputs the input image data with a delay of one horizontal time.

  The changeover switch 523 switches the image data for one horizontal line output from the FIFO line memory 521 or the FILO line memory 522 every horizontal time and outputs the image data to the FILO frame memory 524.

  The FIFO frame memory 524 can store image data for one frame related to input image data. When image data for one horizontal line output from the changeover switch 523 is accumulated for one frame, the image data for one frame is output to the light source driving circuit 51.

  The operation of the image signal control unit 52 having the above configuration will be described below.

  FIG. 12 is a diagram for explaining the operation of the image signal control unit 52. Here, FIG. 12 (a) and FIG. 12 (b) show changes in data (data flow) over time. 12A shows the flow of image data for each horizontal line at the points Pa to Pd in FIG. 11, and FIG. 12B shows the flow for each frame at the points Pd and Pe in FIG. The flow of image data is shown. In FIG. 12A, “A” and “B” indicate horizontal lines of odd and even lines, and numbers “1” to “403” attached to “A” or “B” indicate odd lines or In addition to the line numbers in even-numbered rows, “−” indicates image data for one horizontal line whose data arrangement is inverted by the FILO line memory 522. In FIG. 12B, “F” indicates image data (image frame) for one frame, and numbers “1” to “3” attached to “F” indicate frame numbers. .

  At the point Pa, based on the input image data input to the image signal control unit 52, a data string arranged in order for each horizontal line is formed.

  At the point Pb, one horizontal line of the input image data is written into the FIFO line memory 521 at a write clock wc (FIG. 11), for example, at a frequency of 65 MHz (= horizontal synchronization frequency fh (48.36 kHz) × horizontal all pixels 1344). Thereafter, data is read with the read clock rc1 (FIG. 11) having the same frequency in the next one horizontal time, thereby forming an odd-numbered data column delayed by one horizontal time with respect to the point Pa.

  At the point Pc, after one horizontal line of the input image data is written to the FILO line memory 522 by the write clock wc (FIG. 11), it is read by the read clock rc1 (FIG. 11) having the same frequency in the next one horizontal time. As a result, an even-numbered data column is formed which is delayed by one horizontal time with respect to the point Pa and in which the left and right data arrangements are inverted.

  At the point Pd, a data string obtained by switching the above-described data strings at the points Pb and Pc by the changeover switch 523 for each horizontal line, that is, every horizontal time is formed. This data string is a data string that is delayed by one horizontal time with respect to the data string at the point Pa and in which the data arrangement is inverted only in even-numbered rows, and is written into the FIFO frame memory 524 with the write clock wc (FIG. 11). It is.

  At the point Pe, the image frame stored in the FIFO frame memory 524 is read out by the read clock rc2 (FIG. 11) at the next one vertical time, so that the point Pd is 1 as shown in FIG. 12B. A data string of image frames delayed by the vertical time is formed. Here, it is possible to store the next image frame in the FIFO frame memory 524 in parallel with the operation of reading the image frame from the FIFO frame memory 524 by setting the read clock rc2 to a frequency equal to or higher than the write clock wc. Therefore, a data string of image frames with one vertical time delay can be continuously output from the FIFO frame memory 524. Then, in reading of an image frame from the FIFO frame memory 524 with such a read clock rc2, as shown in FIG. 13, an image for one horizontal line is displayed in one horizontal line display period Thr set during one horizontal period Th. By reading and displaying data at high speed, stable image display is possible.

  Note that the read clock rc2 described above may be generated in the image signal control unit 52 having the FIFO frame memory 524, and a clock signal synchronized with the mechanical resonance frequency using a PLL circuit or the like as a read clock as in the prior art. There is no need to generate

  By the operation of the image signal control unit 52 as described above, an image frame in which the left and right data arrangement is inverted for each horizontal line is output. Based on this image frame, the light source driving circuit 51 outputs the light beam LT of the light source 50. If modulation is performed, an appropriate image can be displayed back and forth in the horizontal scan of the raster scan RS.

<Operation of Horizontal Reading Frequency Setting Unit 62>
The horizontal read frequency setting unit 62 of the horizontal drive control unit 6a performs an operation of setting the horizontal read frequency frh obtained from the horizontal scanning frequency selected based on the mechanical resonance frequency detected by the resonance point detection unit 56. This will be described in detail below.

  In order for the raster scanning RS of the light beam LT by the optical scanner 1 to be fixed, that is, for the positions of the respective scanning lines to overlap between sequentially displayed images, the horizontal readout frequency frh generally performs one-way display of images by horizontal scanning. In a typical case, when the vertical synchronization frequency is fv and the number of horizontal scanning lines (number of lines) is m (m is an integer greater than or equal to the number q of image display lines) as in the above expression (1), the following expression (2 ) Must be satisfied.

frh = fv · m (2):
However, since the image display apparatus 100A of the present embodiment performs horizontal scanning with reciprocal display of images (hereinafter also referred to as “reciprocal display scanning”), the image display apparatus 100A has a frequency of oscillation vibration of the optical scanner 1 in the horizontal scanning direction. A certain horizontal scanning frequency fmhd is (1/2) of the horizontal readout frequency frh as shown in the following equation (3).

fmhd = frh / 2 (3):
Therefore, when the formula (2) is substituted into the above formula (3), the following formula (4) is obtained.

fmhd = fv · m / 2 (4):
Here, in order for the position of the scanning line and the scanning direction to match between the display images obtained by the reciprocating display scanning, the number m of the horizontal scanning lines needs to be an even number, so the following equation (5) is established.

m = 2p (5):
However, p is an integer.

  Therefore, when the above equation (5) is substituted into the above equation (4), the following equation (6) is obtained.

fmhd = fv · p (6):
From the above, in the image display device 100A that performs reciprocal display scanning, from the candidates of the horizontal scanning frequency fmhd that satisfies the above condition (6), that is, n times the vertical synchronization frequency fv (where n is a natural number). For example, if a horizontal scanning frequency near the mechanical resonance frequency related to the optical scanner 1 is selected, image display by the raster scanning RS can be stably performed. This will be described in detail below.

  FIG. 14 is a diagram for explaining horizontal scanning frequency candidates. In FIG. 14, the horizontal axis indicates the frequency, and the vertical axes in FIGS. 14A and 14B indicate the amplitude and phase of the optical scanning output by the optical scanner 1. Note that “fo” in FIG. 14 represents the mechanical resonance frequency in the optical scanner 1.

  As shown in FIG. 14A, the horizontal scanning frequency fmhd satisfying the above equation (6) is set such that the first frequency fp1, the second frequency fp2, the second frequency fp2, If the third frequency fp3,..., And the first frequency fm1, the second frequency fm2, the third frequency fm3,... Is a candidate for the frequency (horizontal scanning frequency) of the drive signal generated by the horizontal scanning frequency signal generator 63. In other words, stable image display is possible by selecting one horizontal scanning frequency fmhd from the candidate frequency groups fp1 to fp4 and fm1 to fm3 around the mechanical resonance frequency fo.

  Hereinafter, using the information of the mechanical resonance frequency fo obtained by the resonance point detection unit 56, the horizontal readout frequency frh in the horizontal readout frequency setting unit 62 is set from the frequency groups fp1 to fp4 and fm1 to fm3 shown in FIG. Three methods (1) to (3) for selecting the horizontal scanning frequency fmhd used in FIG.

(1) Select the frequency closest to the mechanical resonance frequency The horizontal scanning frequency closest to the mechanical resonance frequency fo detected by the resonance point detector 56 is selected. For example, in the case shown in FIG. 14A, the frequency fp1 close to the mechanical resonance frequency fo is selected as the horizontal scanning frequency fmhd. As described above, among the specific frequencies fp1 to fp4 and fm1 to fm3 calculated by the above equation (6) based on the vertical synchronization frequency (vertical scanning frequency) fv, in the vicinity of the mechanical resonance frequency fo, specifically, to the mechanical resonance frequency fo. If the closest frequency is set as the horizontal scanning frequency, substantially resonant vibration can be performed in the mirror section 11, and a large amplitude of optical scanning output can be realized in horizontal scanning.

(2) Select frequency within frequency band defined by quality factor Q. Horizontal scanning frequency from frequency group within pass frequency band fbw defined by quality factor Q (−3 dB) related to resonance characteristic Gf having mechanical resonance frequency fo. Select fmhd. For example, in the case shown in FIG. 14A, the horizontal scanning frequency fmhd is selected from the five frequencies fm2, fm1, fp1, fp2, and fp3.

  Thus, if the horizontal scanning frequency fmhd is selected from the frequency group in the frequency band fbw, the amplitude of the optical scanning output falls within about 30% of the optical scanning output at the mechanical resonance frequency fo. Sufficient optical scanning output can be obtained. Note that the decrease within 30% can be compensated by increasing the gain in the horizontal drive circuit 61 or the like.

  For example, when the mechanical resonance frequency fo detected by the resonance point detection unit 56 is 31 kHz and the quality factor Q is 100, the (-3 dB) pass frequency band fbw (Hz) is calculated as follows. .

fbw = fo / Q = 31000/100 = 310 (Hz):
Therefore, if the vertical synchronization frequency fv = 60 Hz, five frequencies of frequency fm2 = 515 fv (30.9 kHz) to frequency fp3 = 519 fv (31.14 kHz) shown in FIG. 14A are candidates for the horizontal scanning frequency fmhd. Become. For example, when the frequency fp1 = 517 fv is selected, the horizontal readout frequency frh set by the horizontal readout frequency setting unit 62 is 62.04 kHz (= 517 × 60 × 2 Hz).

  As described above, if the frequency near the mechanical resonance frequency fo among the specific frequencies calculated by the above equation (6) based on the vertical synchronization frequency (vertical scanning frequency) fv is set as the horizontal scanning frequency, the mirror unit 11 is substantially omitted. Resonance vibration can be performed, and a large amplitude of optical scanning output can be realized in horizontal scanning.

  It is not essential to determine the frequency band fbw including the horizontal scanning frequency candidate based on the quality factor Q, and a frequency band within the lower limit of the optical scanning output that can be compensated by the horizontal driving circuit 61 is adopted. Also good.

(3) Selection of frequency that can maintain substantially the same phase In method (1) described above, the frequency closest to the mechanical resonance frequency fo detected by the resonance point detector 56 is selected as the horizontal scanning frequency fmhd. When the frequency fo fluctuates due to environmental changes (temperature, etc.), changes with time, etc., the phase of the optical scanning output changes greatly (maximum 180 degrees) as shown in FIG. 14B at a frequency that is too close to the mechanical resonance frequency fo. Therefore, the display image is disturbed.

  Therefore, in order to eliminate such a problem, the horizontal scanning frequency fmhd capable of maintaining substantially the same phase is selected from the phase detection result based on the displacement angle of the mirror unit 11 detected by the angle detection unit 55. For example, the horizontal scanning frequency fmhd is always selected from the frequencies belonging to the frequency band UP higher than the mechanical resonance frequency fo, or the horizontal scanning frequency fmhd is always selected from the frequencies belonging to the frequency band DN lower than the mechanical resonance frequency fo.

  That is, when the horizontal scanning frequency fmhd is changed in accordance with the change in the mechanical resonance frequency fo detected by the resonance point detection unit 56, the mirror unit 11 in each driving signal repeated at each of the horizontal scanning frequencies fmhd before and after the change. If the phase of the swing angle is made substantially equal, even when the mechanical resonance frequency fo fluctuates due to a temperature change or the like, a more stable image display can be performed.

  In the selection of the horizontal scanning frequency fmhd described above, information on the mechanical resonance frequency fo detected by the resonance point detector 56 is used. The detection of the mechanical resonance frequency fo will be described in detail below.

<Detection of mechanical resonance frequency>
Regarding the detection of the mechanical resonance frequency fo in the resonance point detector 56, the horizontal scanning frequency fmhd satisfying the above equation (6) is sequentially swept (for example, fm3 → fm2 → fm1 → fp1 →... In FIG. 14) to detect the angle. This is performed by observing the displacement angle of the mirror unit 11 detected by the unit 55. For example, as shown in FIG. 14 (a), since it is known in advance that the amplitude of the optical scanning output has a crest resonance characteristic Gf centered on the mechanical resonance frequency fo, the light is output every time the frequency is shifted by the vertical scanning frequency fv. If the amplitude of the scanning output is stored and the above-described peak-like resonance characteristic Gf can be observed, it can be determined that the horizontal scanning frequency fmhd corresponding to the top of the peak (maximum amplitude value) corresponds to the mechanical resonance frequency fo. This detection method of the mechanical resonance frequency fo is called a so-called “hill-climbing detection method”, but the quality factor Q of the resonance characteristic Gf related to the mirror unit 11 is generally a high numerical value (for example, 100 or more). Is possible. In addition, when it takes time to detect such a resonance frequency fo, it may be performed when the image display apparatus 100A is turned on (preparation stage).

  As described above, the horizontal scanning frequency signal generator 63 generates each driving signal repeated at each of a plurality of frequencies calculated based on the vertical synchronization frequency fv, and drives the piezoelectric elements 31 to 34 based on each driving signal. Then, the mirror unit 11 is oscillated and oscillated around the first axis Ay, and the frequency corresponding to the mechanical resonance frequency fo is detected by comparing the amplitude of the oscillating angle of the mirror unit 11 in each drive signal. As a result, the mechanical resonance frequency fo can be detected efficiently.

  For the detection of the mechanical resonance frequency fo in the resonance point detection unit 56, in addition to the above-described method of comparing the optical scanning output amplitude, a method of comparing the optical scanning output phase can be employed. That is, since the quality factor Q of the resonance characteristic Gf related to the mirror unit 11 is generally high as described above, the phase of the optical scanning output changes greatly (around 180 degrees at the maximum) around the mechanical resonance frequency fo as shown in FIG. However, it is possible to detect the mechanical resonance frequency fo focusing on this sudden change in phase.

  Specifically, each time the horizontal scanning frequency fmhd satisfying the above equation (6) is shifted by the vertical scanning frequency fv, the phase of the optical scanning output is stored to suddenly change the phase (for example, a phase change larger than a predetermined threshold value). ) Can be determined, the horizontal scanning frequency fmhd at the time of the sudden change can be determined as a frequency corresponding to the mechanical resonance frequency fo.

  In this way, the horizontal scanning frequency signal generator 63 generates each driving signal repeated at each of a plurality of frequencies calculated based on the vertical synchronization frequency fv, and drives the piezoelectric elements 31 to 34 based on each driving signal. The mirror unit 11 is oscillated and oscillated about the first axis Ay, and the frequency corresponding to the mechanical resonance frequency fo is detected by comparing the phase of the oscillating angle of the mirror unit 11 in each drive signal. As a result, the mechanical resonance frequency fo can be detected efficiently.

  As described above, the mechanical resonance frequency fo as a frequency calculated based on the vertical synchronization frequency fv is detected by the resonance point detection unit 56, and any one of the methods (1) to (3) described above is detected based on the detected frequency. However, if the horizontal scanning frequency fmhd is selected, an appropriate drive signal can be generated by the horizontal scanning frequency signal generator 63, so that stable image display is possible.

  Here, when the mechanical resonance frequency fo is detected during the image display operation in the image display apparatus 100A, there is a significant variation from the mechanical resonance frequency fo that has already been detected by the resonance point detection unit 56 and is currently used. Therefore, the frequency is shifted by the vertical scanning frequency fv before and after the mechanical resonance frequency fo currently used. When the amplitude of the optical scanning output at the preceding and succeeding frequencies is larger than the amplitude of the optical scanning output at the current mechanical resonance frequency, it is determined that the mechanical resonance frequency fo fluctuates in the direction of the frequency at which the amplitude increases. .

  Next, the frequency is swept by the vertical scanning frequency fv in the frequency direction of the large amplitude, and the change in the amplitude of the optical scanning output is observed. Here, if the amplitude change is equal to or less than a predetermined threshold, it is determined that the frequency is closest to the mechanical resonance frequency, and the frequency sweep is stopped, and the frequency set at that time is regarded as the mechanical resonance frequency fo. .

  Further, the mechanical resonance frequency fo can be detected during the vertical blanking period. Also in this case, the frequency is shifted by the vertical scanning frequency fv before and after the mechanical resonance frequency fo currently used, and each amplitude of the optical scanning output at the frequency before and after this is changed to the optical scanning output at the current mechanical resonance frequency. If the amplitude is larger than the amplitude, the mechanical resonance frequency fo is determined to have fluctuated in the frequency direction in which the amplitude increases. Next, the frequency is swept by the vertical scanning frequency fv in the frequency direction of the large amplitude, and the change in the amplitude of the optical scanning output is observed. Here, if the amplitude change is equal to or less than a predetermined threshold value, it is determined that the frequency is closest to the mechanical resonance frequency, the frequency sweep is stopped, and the frequency set at that time is regarded as the mechanical resonance frequency fo. . In addition, when it takes time to detect the mechanical resonance frequency fo described above, it is preferable to perform the detection operation not only in one vertical blanking period but also in a plurality of vertical blanking periods.

  On the other hand, when the horizontal scanning frequency fmhd is changed in accordance with the change in the mechanical resonance frequency fo, the horizontal scanning width and the vertical scanning width in the raster scanning RS slightly change.

  In such a case, with respect to the change in the horizontal scanning width, the output of the horizontal drive circuit 61 (for example, gain) is adjusted based on the change in the displacement angle of the mirror unit 11 detected by the angle detection unit 55 to change the mirror unit. Control may be performed so that the amplitude of the oscillation vibration of 11 becomes a predetermined value (target value). As for the change in the vertical scanning width, when the horizontal scanning frequency fmhd is changed as will be described below, for example, the gain G is changed in the vertical drive circuit (not shown) of the vertical drive control unit 6b. Adjustment may be made so that the vertical scanning width becomes a predetermined value (target value). By controlling the changes in the horizontal scanning width and the vertical scanning width as described above, the size and aspect ratio of the display screen can be maintained.

  For the integer p in the above equation (6), the integer p related to the horizontal scanning frequency fmhd before the change is p1, the integer p related to the horizontal scanning frequency fmhd after the change is p2, and the vertical scanning width before and after the change of the horizontal scanning frequency fmhd Are equal, the following equation (7) holds.

q · G1 / (2p1) = q · G2 / (2p2) (7):
However, q indicates the number of effective image display lines (for example, 768 in the case of XGA), and G1 and G2 are the gain G of the vertical drive circuit before and after the change of the horizontal scanning frequency fmhd.

  When the above equation (7) is modified, the following equation (8) is obtained.

G2 / G1 = p2 / p1 (8):
Therefore, if the gain G in the vertical drive circuit of the vertical drive control unit 6b is controlled based on the above equation (8), the vertical scanning width does not change before and after the change of the horizontal scanning frequency fmhd.

  When the mechanical resonance frequency fo changes due to an environmental change (for example, temperature change) during the raster scan RS, and the mechanical resonance characteristic changes, the horizontal scan width of the raster scan RS changes. Aspect ratio will fluctuate. In such a case, based on the change in the angle of the mirror unit 11 detected by the angle detection unit 55, the output of the horizontal drive circuit 61 is adjusted by changing the gain and the amplitude of the oscillation vibration of the mirror unit 11 is determined in advance. If the control is performed so that the value becomes the target value (target value), it is possible to prevent the display screen from changing.

  By the operation of the image display apparatus 100A as described above, the frequency satisfying the above equation (6) and the frequency near the mechanical resonance frequency fo is set to the horizontal scanning frequency fmhd. Synchronization with raster scanning can be easily achieved. As a result, stable image display can be easily performed.

  In the image display device 100A, it is not essential to perform horizontal scanning (reciprocating display scanning) of raster scanning RS with reciprocal display of images, and horizontal scanning of raster scanning RS with one-way display of images (hereinafter, referred to as reciprocal display scanning). Then, it is also possible to perform “one-way display scanning”).

  When this one-way display scanning is performed, the horizontal scanning frequency fmhs equal to the horizontal readout frequency frh as shown in the following equation (9) is different from the horizontal scanning frequency fmhd defined by the above equation (6) in the reciprocating display scanning. Is set.

fmhs = frh (9):
Therefore, when the above equation (2) is substituted into the above equation (9), the following equation (10) is obtained.

fmhs = fv · m (10):
Here, fv represents the vertical synchronization frequency, and m represents the number of horizontal scanning lines (number of lines).

  From the above, when performing one-way display scanning, if a horizontal scanning frequency near the mechanical resonance frequency related to the optical scanner 1 is selected from candidates of the horizontal scanning frequency fmhs that satisfy the condition of the above equation (10), Image display by the raster scan RS can be stably performed. This will be described below.

  FIG. 15 is a diagram for explaining horizontal scanning frequency candidates in one-way display scanning. FIG. 15 is a diagram corresponding to FIG. 14A, where the horizontal axis indicates the frequency, and the vertical axis indicates the amplitude of the optical scanning output by the optical scanner 1. Note that “fo” in FIG. 15 represents the mechanical resonance frequency in the optical scanner 1.

  As shown in FIG. 15, the horizontal scanning frequency fmhs satisfying the above equation (10) is, for example, the first frequency hp1, the second frequency hp2, the third frequency in the direction in which the frequency increases from the mechanical resonance frequency fo. If the frequency is hp3,..., And the frequency decreases from the mechanical resonance frequency fo, the first frequency hm1, the second frequency hm2, the third frequency hm3,. The frequency of the drive signal generated by the horizontal scanning frequency signal generator 63 (horizontal scanning frequency) is a candidate. In other words, stable image display is possible by selecting one horizontal scanning frequency fmhs from the candidate frequency groups hp1 to hp4 and hm1 to hm3 around the mechanical resonance frequency fo.

  The selection of the horizontal scanning frequency fmhs can be performed using any one of the methods (1) to (3) in the above-described reciprocating display scanning.

  In the one-way display scan, the resonance point detection unit 56 uses the mechanical resonance frequency detection method in the above-described reciprocating display scan, and sequentially sweeps the horizontal scanning frequency fmhs satisfying the above equation (10) (for example, in FIG. 15). hm3 → hm2 → hm1 → hp1 →...) makes it possible to efficiently detect the mechanical resonance frequency fo.

  On the other hand, when the horizontal scanning frequency fmhs is changed with the change of the mechanical resonance frequency fo, the horizontal scanning width and the vertical scanning width in the raster scanning RS are slightly changed.

  In such a case, with respect to the change in the horizontal scanning width, as in the case of the above-described reciprocating display scanning, the horizontal driving circuit 61 determines the change in the displacement angle of the mirror unit 11 detected by the angle detection unit 55. What is necessary is just to control so that the amplitude of the oscillation vibration of the mirror part 11 may become a predetermined value (target value) by adjusting the output. As for the change in the vertical scanning width, when the horizontal scanning frequency fmhs is changed as will be described below, for example, the gain G is changed in the vertical drive circuit (not shown) of the vertical drive control unit 6b to output the change. Adjustment may be made so that the vertical scanning width becomes a predetermined value (target value). By controlling the changes in the horizontal scanning width and the vertical scanning width as described above, the size and aspect ratio of the display screen can be maintained.

  For the integer m in the above equation (10), the integer m related to the horizontal scanning frequency fmhs before the change is m1, the integer m related to the horizontal scanning frequency fmhs after the change is m2, and the vertical scanning width before and after the change of the horizontal scanning frequency fmhs. Are equal, the following equation (11) holds.

q · G1 / m1 = q · G2 / m2 (11):
However, q indicates the number of effective image display lines (for example, 768 in the case of XGA), and G1 and G2 are the gain G of the vertical drive circuit before and after the change of the horizontal scanning frequency fmhs.

  When the above equation (11) is modified, the following equation (12) is obtained.

G2 / G1 = m2 / m1 (12):
Therefore, if the gain G in the vertical drive circuit of the vertical drive control unit 6b is controlled based on the above equation (12), the vertical scanning width does not change before and after the change of the horizontal scanning frequency fmhs.

  Note that the operation of the image signal control unit 52 in the case of performing one-way display scanning is, as shown in FIG. 16, one horizontal line display period set during a half period (Th / 2) of one horizontal period Th. Since the image data for one horizontal line is read and displayed at high speed in Ths, stable image display is possible. In this case, it is not necessary to invert the data arrangement in each adjacent horizontal line as in the case of the reciprocating display scanning shown in FIG. 12A, and the data string at the point Pa in FIG. The input image data input to the control unit 52 can be used as it is.

Second Embodiment
The image display device 100B according to the second embodiment of the present invention has a configuration similar to that of the image display device 100A according to the first embodiment shown in FIGS. 1 to 3, but an image signal control unit and a horizontal drive control unit. The configuration is different.

  That is, the image signal control unit 520 and the horizontal drive control unit 60a of the image display device 1B have a configuration in which a program for performing the operation described below is stored.

<Operation of Image Signal Control Unit 520>
The image signal control unit 520 has the same configuration as that of the image signal control unit 52 of the first embodiment shown in FIG. 11, but can use this configuration to perform operations different from those of the first embodiment. ing. Specifically, in the raster scanning RS (FIG. 1), the same reciprocating display scanning as that in the first embodiment can be performed, and the reciprocating display scanning in the direction opposite to that in the first embodiment is possible. This will be described in detail below.

  FIG. 17 is a diagram for explaining the operation of the image signal control unit 520. Here, FIG. 17 (a) corresponds to FIG. 12 (a).

  The image signal control unit 520 of the second embodiment can perform the same operation as the image signal control unit 52 of the first embodiment as shown in FIG.

  On the other hand, as shown in FIG. 17B, the image signal control unit 520 of the present embodiment can perform an operation opposite to that of the image signal control unit 52 of the first embodiment.

  That is, at the point Pb shown in FIG. 11, one horizontal line of the input image data is written in the FILO line memory 522 at the write clock wc, for example, the frequency 65 MHz (= horizontal synchronization frequency fh (48.36 kHz) × horizontal all pixels 1344). After being written, the data is read with the read clock rc1 having the same frequency in the next one horizontal time, so that the data columns in the odd rows that are delayed by one horizontal time with respect to the point Pa and in which the left and right data arrangements are inverted. It is formed.

  At a point Pc shown in FIG. 11, after one horizontal line of the input image data is written to the FIFO line memory 521 by the write clock wc, it is read by the read clock rc1 having the same frequency in the next one horizontal time. , Even-numbered data columns delayed by one horizontal time with respect to the point Pa are formed.

  At the point Pd shown in FIG. 11, a data string obtained by switching the above-described data string at the points Pb and Pc by the changeover switch 523 for each horizontal line, that is, every horizontal time is formed. This data string is a data string that is delayed by one horizontal time with respect to the data string at the point Pa and in which the data arrangement is inverted only in the odd-numbered rows, and is written into the FIFO frame memory 524 with the write clock wc.

  By the operation of the image signal control unit 520 as described above, an image frame in which only the even-numbered data array is inverted as shown in FIG. 17A, or only the odd-numbered data array as shown in FIG. An inverted image frame can be output.

<Operation of Horizontal Drive Control Unit 60a>
The horizontal read frequency setting unit 62 of the horizontal drive control unit 60a performs an operation of setting the horizontal read frequency frh obtained from the horizontal scanning frequency selected based on the mechanical resonance frequency detected by the resonance point detection unit 56. This will be described in detail below.

  In the reciprocal display scanning in the case where the image signal control unit 520 generates an image frame in which only the even-numbered rows of data are inverted as shown in FIG. 17A, the above equation (6) is used as in the first embodiment. If the horizontal scanning frequency near the mechanical resonance frequency fo related to the optical scanner 1 is selected from the candidates of the horizontal scanning frequency fmhd satisfying the above condition, image display by the raster scanning RS can be stably performed.

  On the other hand, an image frame in which only the even-numbered data sequence is inverted as shown in FIG. 17A and an image frame in which only the odd-numbered data sequence is inverted as shown in FIG. In the reciprocating display scanning when generated by the image signal control unit 520, if a horizontal scanning frequency near the mechanical resonance frequency fo related to the optical scanner 1 is selected from candidates of the horizontal scanning frequency fmhd that satisfies the following equation (13): The image display by the raster scanning RS can be stably performed.

fmhd = fv · (p + 0.5) (13):
However, fv is a vertical synchronizing frequency and p is an integer.

  That is, in the image display device 100B of the present embodiment, from the candidates for the horizontal scanning frequency fmhd that satisfies the above equation (13), that is, the (n + 0.5) times (where n is a natural number) the vertical synchronization frequency fv, The horizontal scanning frequency can be selected.

  From the above, the image display device 100B of this embodiment has candidates for the horizontal scanning frequency fmhd approximately twice that of the first embodiment. Specifically, as shown in FIG. 18 corresponding to FIG. 14A, in addition to the frequency groups fp1 to fp3 and fm1 to fm3 satisfying the above-described expression (6), the frequency group satisfying the above-described expression (13). The horizontal frequency fmhd can also be selected from ffp1 to ffp3 and ffm1 to ffm3. When the horizontal scanning frequency fmhd is selected from the frequency groups fp1 to fp3 and fm1 to fm3 satisfying the above-described expression (6), the image signal control unit 520 performs the image frame generation operation shown in FIG. On the other hand, when the horizontal scanning frequency fmhd is selected from the frequency groups ffp1 to ffp3 and ffm1 to ffm3 satisfying the above equation (13), the image signal control unit 520 generates the image frame shown in FIG. By performing the above, stable image display becomes possible.

  For the detection of the mechanical resonance frequency fo in the resonance point detector 56, the horizontal scanning frequency fmhd satisfying the above equation (6) or (13) is sequentially swept (for example, fm3 → ffm3 → fm2 → ffm2 → in FIG. 18). fm1 → ffm1 → fp1 → ffp1 →...), and the displacement angle of the mirror unit 11 detected by the angle detection unit 55 is observed.

  By the operation of the image display device 100B as described above, the same effects as those of the first embodiment are obtained. Further, in the image display device 100B, since the horizontal scanning frequency can be selected in increments of the vertical synchronization frequency fv / 2 as shown in FIG. 18, the degree of freedom in the selection is improved.

  Further, in the image display devices 100A and 100B of the first and second embodiments, the optical scanner 1 shown in FIG. 2 is rotated by 90 degrees with respect to the front, specifically, the optical scanner as shown in FIG. The light beam LT from the light source 50 may be raster scanned in one posture. Such an optical scanner 1 (FIG. 19) can reduce the moment of inertia of the movable part in the horizontal direction, which is driven at a higher speed than the vertical direction in the raster scanning RS.

<Third Embodiment>
An image display device 100C according to the third embodiment of the present invention has a configuration similar to that of the image display devices 100A and 100B of the first and second embodiments shown in FIG. 1, but the configuration of the optical scanner is different. ing.

<Main components of optical scanner>
FIG. 20 is a plan view showing a main configuration of an optical scanner 101 according to the third embodiment of the present invention.

  The optical scanner 101 is configured by a so-called MEMS (Micro Electro Mechanical Systems) mirror in which fine processing is performed on a silicon chip. Hereinafter, the optical scanner 101 is also referred to as a MEMS mirror 101 as appropriate.

  The optical scanner 101 mainly includes a mirror part 110, two torsion bars 121 and 122, a movable frame 130, an actuator part 150 including four piezoelectric elements (piezoelectric actuators) 151 to 154, four construction parts 141 to 144, Four fine coupling portions 130 a to 130 d and a fixed frame 170 are provided.

  The fixed frame 170 is a frame that is fixed to the housing of the image display device 100C and has four sides in which four plate-like portions are arranged in a substantially rectangular shape. The outer edge and the inner edge are substantially orthogonal to each other. The a-axis and the b-axis have a substantially square shape, and the inner edge forms a substantially square space.

  Then, two erection parts 141 and 143 are connected to a portion in the + b direction (upward in FIG. 20) on the b-axis inside the corner portion of the fixed frame 170, and the erection part 141 is connected to the fixed frame 170. Are arranged along one side located in the −a and + b directions (upper left in FIG. 20), and the erection portion 143 is located on one side located in the + a and + b directions (upper right in FIG. 20) of the fixed frame 170. Are arranged along. In addition, two erection parts 142 and 144 are connected to a portion of the corner of the fixed frame 170 in the −b direction (downward in FIG. 20) on the b axis. 170 is arranged along one side located in the −a and −b directions (lower left in FIG. 20), and the erection portion 144 is located in the + a and −b directions (lower right in FIG. 20) of the fixed frame 170. It is arranged along one side.

  In addition, piezoelectric elements 151 to 154 are attached to the installation parts 141 to 144 along the extending direction of the installation parts 141 to 144, respectively. Therefore, the erected portion 141 and the piezoelectric element 151 are extended from the inside of the corner portion of the fixed frame 170 located in the + b direction (upward in FIG. 20) toward the −a and −b directions (lower left in FIG. 20). The telescopic construction part 161 is configured, and the construction part 142 and the piezoelectric element 152 are in the −a and + b directions (upper left in FIG. ) Extending from the inside of the corner portion where the erection portion 143 and the piezoelectric element 153 are located in the + b direction (upward in FIG. 20) of the fixed frame 170 in the + a and −b directions. The telescopic construction part 163 extending toward the right (lower right in FIG. 20) is configured, and the construction part 144 and the piezoelectric element 154 have corner portions located in the −b direction (downward in FIG. 20) of the fixed frame 170. + A and + b directions from the inside (Fig. 2 In constituting the stretch-installing portion 164 which extends toward the upper right).

  The telescopic construction part 161 and the telescopic construction part 162 are spaced apart by a predetermined distance across the a axis, and the telescopic construction part 163 and the telescopic construction part 164 are spaced apart by a predetermined distance across the a axis.

  In addition, the end on the a-axis side of the telescopic installation part 161 is connected to the movable frame 130 by the thin connection part 130a, and the end on the a-axis side of the expansion / contraction installation part 162 is connected to the movable frame 130 by the thin connection part 130b. The a-axis side end of the telescopic erection part 163 is coupled to the movable frame 130 by the thin coupling part 130c, and the a-axis side end of the telescopic erection part 164 is coupled to the movable frame 130 by the thin coupling part 130d. Is connected to

  Similarly to the fixed frame 170, the movable frame 130 is a frame having four sides in which four plate-like portions are arranged in a substantially rectangular shape, and the outer edges are a-axis and b-axis whose diagonals are orthogonal to each other. It has a certain square shape, and the inner edge forms a hexagonal space.

  A torsion bar 121 extends in the −b direction (downward in FIG. 20) in the + b direction (upward in FIG. 20) on the b-axis inside the corner of the movable frame 130, and is movable. A torsion bar 122 extends in the + b direction (upward in FIG. 20) in the −b direction (downward in FIG. 20) on the b-axis inside the corner of the frame 130.

  The mirror part 110 is connected to the end of the torsion bar 121 that is not connected to the movable frame 130, and the mirror part 110 is connected to the end of the torsion bar 122 that is not connected to the movable frame 130. That is, the torsion bars 121 and 122 support the mirror unit 110 so as to be sandwiched from the + Y direction and the −Y direction. That is, the movable frame 130 supports the torsion bars 121 and 122 together with the mirror unit 110.

  The mirror unit 110 is a substantially square reflecting mirror having two sides that are substantially parallel to the a axis and two sides that are substantially parallel to the b axis as outer edges, and is disposed at the approximate center of the optical scanner 101. Reflects light rays for projection.

  Since the two torsion bars 121 and 122 are thin and have an elongated shape, they are elastically deformed relatively easily. Further, since the thin connecting portions 130a to 130d are thin and thin, they are elastically deformed relatively easily.

  As a specific rotation operation of the mirror unit 110, when a voltage is appropriately applied to the piezoelectric elements 151 to 154, the length of the piezoelectric elements 151 to 154 changes according to the applied voltage. The installation parts 141 to 144 to which the 154 is attached extend and contract along the extending direction. That is, the expansion / contraction erection parts 161 to 164 expand and contract along the extending direction. Therefore, for example, the voltage applied to the piezoelectric elements 151 and 153 and the voltage applied to the piezoelectric elements 152 and 154 are alternately switched between positive and negative, that is, the piezoelectric elements 151 and 153 and the piezoelectric elements 152 and 154 have an opposite phase. By applying a voltage, the mirror unit 110 rotates about the a axis. On the other hand, for example, the voltage applied to the piezoelectric elements 151 and 152 and the voltage applied to the piezoelectric elements 153 and 154 are alternately switched between positive and negative, that is, the piezoelectric elements 151 and 152 and the piezoelectric elements 153 and 154 have opposite phases. By applying a voltage, the mirror unit 110 rotates about the b-axis.

  For the four piezoelectric elements 151 to 154, a drive signal for realizing the rotation of the mirror unit 110 around the a axis and the rotation of the mirror unit 110 about the b axis are realized. By applying the drive signal in a superimposed manner, the mirror unit 110 causes the resonance drive around the b-axis with the torsion bars 121 and 122 as fulcrums, and the movable frame 130 for each of the mirror unit 110 and the torsion bars 121 and 122. Drive to rotate around the a-axis. Therefore, although it is one element having one mirror part 110, it is possible to simultaneously perform low-speed rotation about the a-axis and high-speed rotation about the b-axis using resonance drive. . In other words, by deflecting the light beam LT (FIG. 2) from the light source 50 along two different directions, the horizontal scanning and the vertical scanning of the light beam LT (FIG. 2) on the screen 9 (FIG. 1) can be performed simultaneously. it can. In other words, the actuator unit 150 including the four piezoelectric elements 151 to 154 oscillates the mirror unit (movable unit) 110 that reflects the light beam LT emitted from the light source 50 around the b-axis to generate the light beam LT. First oscillating means for performing horizontal scanning, and second oscillating means for performing scanning in the vertical direction of the light beam LT by oscillating the movable portion about an a axis intersecting the first axis at a substantially right angle. Will be included. Note that it is preferable to perform two-dimensional scanning, which performs horizontal scanning and vertical scanning at the same time, with a single element in order to reduce the number of parts of the optical scanner 101, and work required for manufacturing cost reduction and element adjustment. It is also preferable from the aspect that it can be reduced.

  Also in the optical scanner 101 configured as described above, by performing the same operations of the image signal control units 52 and 520 and the horizontal drive control unit 60a as in the first embodiment and the second embodiment described above, The same effect as in the second embodiment will be achieved.

  In the third embodiment, in the optical scanner 101, one mirror unit 110 is rotated about two axes (a axis and b axis) that are substantially orthogonal to each other, so that the light source 50 (FIG. 1) Although the light beam LT (FIG. 2) is scanned two-dimensionally, the scanning of the light beam in the horizontal direction and the scanning of the light beam in the vertical direction are realized by rotating two mirror units provided separately. Thus, the light beam LT from the light source 50 may be scanned two-dimensionally. As a specific example of such a configuration, a first actuator that swings the first mirror part (first movable part) that reflects the light beam LT emitted from the light source 50 about the a ′ axis, and a first actuator A second actuator that swings the second mirror part (second movable part) reflecting the light beam LT reflected by the mirror part about the b ′ axis from the light source 50 to the screen 9 (FIG. 1). In the optical path to reach, there is an embodiment in which they are arranged sequentially in space. However, in order to realize horizontal and vertical scanning, the a ′ axis and the b ′ axis are respectively lines in the optical path along the optical path from the light source 50 to the screen 9 (preferably the central line of the optical path, that is, the center The position and angular relationship between the a ′ axis and the b ′ axis are separated by a predetermined distance along the center line of the optical path, and the optical path is set. It is preferable to have a relationship of about 90 ° rotation about the center line. In other words, the b ′ axis is separated by a predetermined distance along a predetermined straight line substantially orthogonal to the a ′ axis with respect to the a ′ axis, and is rotated by about 90 ° around the predetermined straight line. It is preferable.

<Modification>
In each of the above embodiments, it is not essential to use a single vibration drive signal as shown in FIG. 10, and a rectangular drive signal as shown in FIG. 21 may be used. If such a rectangular drive signal also has a frequency component in the vicinity of the mechanical resonance frequency, the mirror unit 11 can be resonantly oscillated.

  For the angle detection unit in each of the above embodiments, it is not essential to detect the displacement angle of the mirror units 11 and 110 using the photo reflector 550 (FIG. 4). For example, the angle detection unit is attached to a torsion bar (described later). The displacement angle of the mirror unit 11 may be detected based on an output signal from a displacement angle detection sensor such as a piezoelectric element.

  In the optical scanner in each of the above embodiments, it is not essential to use a piezoelectric element as an actuator for swinging and displacing the mirror portions 11 and 110, and an electrostatic actuator such as an electromagnetic actuator such as a VCM or an electrostatic vibrator. An actuator or an actuator using a polymer resin (polymer) may be used.

  In each of the above embodiments, it is not essential to perform a raster scan of a light beam using an optical scanner having two swingable axes, and two sets of light having a single swingable axis. A raster scan of light rays may be performed using a scanner. Also in this case, the raster scanning of the light beam can be performed by swinging each mirror portion provided as a movable portion in each of the two sets of optical scanners about the axis of the optical scanner that intersects at a substantially right angle.

  In each of the above embodiments, it is not essential for the resonance point detection unit 56 to detect the mechanical resonance frequency related to the oscillation vibration of the mirror unit 11 based on the detection result of the angle detection unit 55, and these portions are provided. It is not necessary. In this case, for example, the resonance frequency may be measured at the time of factory inspection for each product related to the image display device and stored in a memory such as the optical scanner control unit 6.

It is a figure which shows the external appearance of 100 A of image display apparatuses which concern on 1st Embodiment of this invention. 4 is a diagram for explaining a positional relationship between the optical scanner 1 and a light source 50. FIG. It is a block diagram which shows the function structure of 100 A of image display apparatuses. It is a figure for demonstrating the angle detection of the mirror part 11 by the photo reflector 550. FIG. It is a figure for demonstrating the amplitude detection of the displacement angle of the mirror part. 2 is a plan view showing a main configuration of the optical scanner 1. FIG. It is sectional drawing seen from the VII-VII position of FIG. FIG. 6 is a diagram for explaining a swinging vibration operation of the mirror unit 11. It is a block diagram for demonstrating the principal part structure of the horizontal drive control part 6a. FIG. 6 is a diagram for explaining a drive signal output from a horizontal scanning frequency signal generation unit 63. 3 is a diagram for explaining a main configuration of an image signal control unit 52. FIG. 6 is a diagram for explaining the operation of an image signal control unit 52. FIG. It is a figure for demonstrating the data reading for 1 horizontal line in 1 horizontal period Th. It is a figure for demonstrating the candidate of a horizontal scanning frequency. It is a figure for demonstrating the candidate of the horizontal scanning frequency in a one-way display scanning. It is a figure for demonstrating the data reading for 1 horizontal line in 1 horizontal period Th by one way display scanning. It is a figure for demonstrating operation | movement of the image signal control part 520 of the image display apparatus 100B which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the candidate of a horizontal scanning frequency. It is a figure for demonstrating the optical scanner 1 of another attitude | position. It is a top view which shows the principal part structure of the optical scanner 101 which concerns on 3rd Embodiment of this invention. It is a figure for demonstrating the rectangular-shaped drive signal which concerns on the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Optical scanner 6 Optical scanner control part 6a, 60a Horizontal drive control part 6b Vertical drive control part 9 Screen 11, 110 Mirror part 13a, 13b, 14a, 14b, 121, 122 Torsion bar 31-38 Piezoelectric element 50 Light source 52 520 Image signal control unit 55 Angle detection unit 56 Resonance point detection unit 61 Horizontal drive circuit 62 Horizontal readout frequency setting unit 63 Horizontal scanning frequency signal generation unit 100A to 100C Image display device 150 Actuator unit 521 FIFO line memory 522 FILO line memory 523 Changeover switch 524 FIFO frame memory fo machine resonance frequency RS raster scan Th 1 horizontal period

Claims (12)

An image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays,
(a) a first actuator that swings a movable portion having a reflecting surface that reflects a light beam emitted from a predetermined light source around a first axis;
(b) a second actuator that swings the movable portion around a second axis that intersects the first axis at a substantially right angle;
(c) driving the first actuator based on a first drive signal repeated at a first frequency to swing and vibrate the movable part around the first axis, thereby causing a light beam reflected by the reflecting surface to be reflected; Main scanning means for scanning in the main scanning direction according to the raster scanning;
(d) driving the second actuator based on a second drive signal repeated at a second frequency to swing the movable portion around the second axis, thereby causing the light beam reflected by the reflecting surface to Sub-scanning means for scanning in the sub-scanning direction related to raster scanning;
With
The main scanning means includes
(c-1) detection means for detecting a frequency corresponding to a resonance frequency related to oscillation vibration of the movable part;
(c-2) setting means for setting a frequency near the resonance frequency among the specific frequencies calculated based on the second frequency as the first frequency;
An image display device comprising: The image display device according to claim 1,
The image display apparatus according to claim 1, wherein the specific frequency is n times (where n is a natural number) the second frequency. The image display device according to claim 1 or 2,
2. The image display device according to claim 1, wherein the specific frequency is (n + 0.5) times (where n is a natural number) times the second frequency. The image display device according to any one of claims 1 to 3,
The setting means includes
Means for setting, as the first frequency, a frequency closest to the resonance frequency among the specific frequencies;
An image display device comprising: The image display device according to any one of claims 1 to 4,
The main scanning means includes
Signal generating means for generating each of the driving signals repeated at each of a plurality of frequencies calculated based on the second frequency as the first driving signal;
And having
The detection means includes
Based on each drive signal generated by the signal generating means, the first actuator is driven to oscillate the movable part around the first axis, and the oscillation angle of the movable part in each drive signal is determined. Means for detecting a frequency corresponding to the resonance frequency by comparing amplitudes;
An image display device comprising: The image display device according to any one of claims 1 to 4,
The main scanning means includes
Signal generating means for generating each of the driving signals repeated at each of a plurality of frequencies calculated based on the second frequency as the first driving signal;
And having
The detection means includes
Based on each drive signal generated by the signal generating means, the first actuator is driven to oscillate the movable part around the first axis, and the oscillation angle of the movable part in each drive signal is determined. Means for detecting a frequency corresponding to the resonance frequency by comparing phases;
An image display device comprising: The image display device according to any one of claims 1 to 6,
The frequency detected by the detection means is a frequency calculated based on the second frequency. The image display device according to any one of claims 1 to 7,
The setting means includes
Changing means for changing the first frequency in accordance with a change in the resonance frequency detected by the detecting means;
Have
The image display device according to claim 1, wherein the phase of the swing angle of the movable portion in each drive signal repeated at each of the first frequencies before and after the change by the changing means is substantially equal. An image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays,
(a) a first actuator that swings a movable portion having a reflecting surface that reflects a light beam emitted from a predetermined light source around a first axis;
(b) a second actuator that swings the movable portion around a second axis that intersects the first axis at a substantially right angle;
(c) driving the first actuator based on a first drive signal repeated at a first frequency to swing and vibrate the movable part around the first axis, thereby causing a light beam reflected by the reflecting surface to be reflected; Main scanning means for scanning in the main scanning direction according to the raster scanning;
(d) driving the second actuator based on a second drive signal repeated at a second frequency to swing the movable portion around the second axis, thereby causing the light beam reflected by the reflecting surface to Sub-scanning means for scanning in the sub-scanning direction related to raster scanning;
With
The main scanning means includes
(c-1) Setting means for setting, as the first frequency, a frequency near a resonance frequency related to oscillation vibration of the movable part among the specific frequencies calculated based on the second frequency,
An image display device comprising: An image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays,
(a) a first actuator that swings a first movable portion having a first reflecting surface that reflects a light beam emitted from a predetermined light source around a first axis;
(b) a second actuator that swings a second movable portion having a second reflective surface that reflects the light beam reflected by the first reflective surface about a second axis;
(c) driving the first actuator based on a first drive signal repeated at a first frequency to cause the first movable portion to oscillate and vibrate around the first axis; Main scanning means for scanning reflected light rays in the main scanning direction according to the raster scanning;
(d) Reflecting on the second reflecting surface by driving the second actuator based on the second driving signal repeated at the second frequency and swinging the second movable portion around the second axis. Sub-scanning means for scanning the emitted light beam in the sub-scanning direction related to the raster scanning;
With
The main scanning means includes
(c-1) Setting means for setting, as the first frequency, a frequency near a resonance frequency related to oscillation vibration of the first movable part among the specific frequencies calculated based on the second frequency,
An image display device comprising: An image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays,
(a) a first actuator that swings a first movable portion having a first reflecting surface that reflects a light beam emitted from a predetermined light source around a first axis;
(b) a second actuator that swings a second movable portion having a second reflective surface that reflects the light beam reflected by the first reflective surface about a second axis;
(c) driving the second actuator based on a first drive signal repeated at a first frequency to swing and vibrate the second movable portion around the second axis, thereby causing the second reflecting surface to Main scanning means for scanning reflected light rays in the main scanning direction according to the raster scanning;
(d) Reflecting on the first reflecting surface by driving the first actuator based on the second driving signal repeated at the second frequency and swinging the first movable portion around the first axis. Sub-scanning means for scanning the emitted light beam in the sub-scanning direction related to the raster scanning;
With
The main scanning means includes
(c-1) Setting means for setting, as the first frequency, a frequency near a resonance frequency related to oscillation vibration of the second movable part among the specific frequencies calculated based on the second frequency,
An image display device comprising: An image display device capable of displaying an image on a predetermined projection surface by raster scanning of light rays,
(a) a first swinging means for swinging a movable part having a reflecting surface for reflecting a light beam emitted from a predetermined light source around a first axis, and the movable part intersecting the first axis at a substantially right angle; An actuator unit having second swinging means for swinging about a second axis that
(b) Based on the first drive signal repeated at the first frequency, the light beam reflected by the reflecting surface is oscillated and oscillated around the first axis using the first oscillating means. Main scanning means for scanning in the main scanning direction according to the raster scanning;
(d) oscillating the movable part around the second axis using the second oscillating means based on the second drive signal repeated at the second frequency, thereby causing the light beam reflected by the reflecting surface to Sub-scanning means for scanning in the sub-scanning direction related to raster scanning;
With
The main scanning means includes
(c-1) Setting means for setting, as the first frequency, a frequency near a resonance frequency related to oscillation vibration of the movable part among the specific frequencies calculated based on the second frequency,
An image display device comprising:

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