WO2013001642A1

WO2013001642A1 - Mirror

Info

Publication number: WO2013001642A1
Application number: PCT/JP2011/065071
Authority: WO
Inventors: 猶原　真一
Original assignee: パイオニア株式会社
Priority date: 2011-06-30
Filing date: 2011-06-30
Publication date: 2013-01-03

Abstract

This mirror is applied to, for instance, an image display device that displays images by performing scanning using a laser beam. The mirror has: a frame section; a mirror section, which can rotate with respect to the frame section; and an elastic section, which supports the mirror section with respect to the frame section, and rotates the mirror section. Specifically, the elastic section is configured of a piezoelectric element that generates a voltage corresponding to distortion generated due to the rotation of the mirror section. Consequently, abnormal states can be suitably detected, and size reduction and cost reduction of the image display device and the like are made possible.

Description

mirror

The present invention relates to a mirror used in an image display device.

Conventionally, an image display device that displays an image by scanning a laser beam is known. For example, in Patent Document 1, in an optical apparatus using a scanner having a scanning mirror that scans laser light from a laser light source, the angle of the scanning mirror of the scanner is detected by an angle sensor, and the scanning mirror operates in a safe normal state. There has been proposed a technique for determining whether or not it is.

Japanese Patent Laid-Open No. 2005-31266

However, in the technique described in Patent Document 1 described above, since an angle sensor is used, it is difficult to reduce the size and cost of the image display device.

Examples of the problem to be solved by the present invention include the above. It is an object of the present invention to provide a mirror that can appropriately detect an abnormal state and can realize downsizing and cost reduction of an image display device.

In the first aspect of the invention, the mirror is configured to support the mirror unit with respect to the frame unit, the mirror unit rotatable with respect to the frame unit, and rotate the mirror unit. And an elastic part having a sufficient elasticity, and the elastic part is composed of a piezoelectric element that generates a voltage corresponding to a twist generated by the rotation of the mirror part.

In a seventh aspect of the invention, the mirror includes a frame part, a mirror part rotatable with respect to the frame part, a magnetic body provided in the mirror part, and the magnetic material generated by rotation of the mirror part. Detecting means for detecting a change in the magnetic field according to a change in the position of the body.

1 shows a configuration of an image display apparatus according to a first embodiment. The structure of the MEMS mirror which concerns on 1st Example is shown. The specific example of the voltage waveform obtained from an elastic part is shown. It is a flowchart which shows the abnormality determination process which concerns on 1st Example. The structure of the image display apparatus which concerns on 2nd Example is shown. The structure of the MEMS mirror which concerns on 2nd Example is shown. It is a flowchart which shows the abnormality determination process which concerns on 2nd Example.

In one aspect of the present invention, the mirror includes a frame part, a mirror part rotatable with respect to the frame part, and supports the mirror part with respect to the frame part and rotates the mirror part. An elastic portion having elasticity, and the elastic portion is formed of a piezoelectric element that generates a voltage corresponding to torsion caused by rotation of the mirror portion.

The above mirror is applied to an image display device that displays an image by scanning (scanning) a laser beam, for example. In the mirror, the elastic part itself that supports the mirror part is configured as a piezoelectric element. Thereby, based on the voltage change by the twist of the elastic part resulting from rotation of a mirror part, abnormality determination can be performed appropriately. In addition, since the elastic portion itself is configured as a piezoelectric element to perform abnormality determination, it is not necessary to separately add an angle sensor as described in Patent Document 1 described above. In comparison, it is possible to reduce the size and cost of the apparatus to which the mirror is applied.

In one aspect of the mirror described above, the mirror further includes a driving unit that rotates the mirror portion by a magnetic force. In this aspect, the mirror unit is driven by a magnetic force, and the operation of the mirror unit is detected by an elastic unit as a piezoelectric element. That is, magnetic force is used for the drive system, and voltage is used for the detection system. Therefore, crosstalk and noise between the drive system signal and the detection system signal can be appropriately reduced.

In another aspect of the mirror described above, the mirror further includes detection means for detecting a rotation angle of the mirror unit based on the voltage. Thereby, abnormality determination can be performed appropriately based on the detected rotation angle.

In another aspect of the mirror described above, the mirror is applied to an image display device that displays an image by scanning light from a light source, and the elastic portion has a natural frequency that is in a resonance relationship with a scanning operation frequency. Yes. Thereby, energy required for the scanning operation can be reduced.

In another aspect of the above mirror, the mirror is applied to an image display device that displays an image by scanning light from a light source, and the elastic portion has a peak output voltage at a frequency corresponding to a scanning operation frequency. It has the following characteristics. As a result, the output voltage of the elastic portion generated by the operation of the mirror portion can be increased, and subsequent detection and determination can be easily performed.

Preferably, in the mirror described above, the elastic portion has elasticity so as to rotate the mirror portion around an axis along one direction as a central axis.

In another aspect of the present invention, the mirror includes a frame portion, a mirror portion rotatable with respect to the frame portion, a magnetic body provided on the mirror portion, and the magnetic body generated by rotation of the mirror portion. Detecting means for detecting a change in the magnetic field in accordance with a change in the position.

In the above mirror, the detecting means detects a change in the magnetic field according to a change in the position of the magnetic body due to the rotation of the mirror section. Abnormality determination can be appropriately performed based on such a magnetic field change. In addition, since the abnormality determination is performed using the magnetic body and the detection means, it is not necessary to separately add an angle sensor as described in Patent Document 1 described above, so compared with the configuration described in Patent Document 1. Thus, it is possible to reduce the size and cost of the apparatus to which the mirror is applied.

In another aspect of the mirror described above, the detection unit detects a rotation angle of the mirror unit based on a change in the magnetic field. Thereby, abnormality determination can be performed appropriately based on the detected rotation angle.

In another aspect of the above-described mirror, the mirror further includes a driving unit that rotates the mirror unit with a voltage. In this aspect, the mirror unit is driven by a voltage, and the operation of the mirror unit is detected from a magnetic field change. That is, a voltage is used for the drive system, and a magnetic field change is used for the detection system. Therefore, crosstalk and noise between the drive system signal and the detection system signal can be appropriately reduced.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
First, a first embodiment of the present invention will be described.

(overall structure)
FIG. 1 shows a configuration of an image display apparatus 1 according to the first embodiment. As shown in FIG. 1, the image display device 1 mainly includes an image signal input unit 2, a video ASIC 3, a frame memory 4, a ROM 5, a RAM 6, a laser driver ASIC 7, a MEMS mirror control unit 8, A laser light source unit 9 and an abnormality detection circuit 60 are provided. For example, the image display device 1 is configured to be attachable to a head-up display that visually recognizes an image as a virtual image from the position (eye point) of the user's eyes, a user's head, and the like, and draws an image on the user's retina. Applies to head mounted displays. In addition, the image display device 1 can be applied to a projector using laser light, for example.

The image signal input unit 2 receives an image signal input from the outside and outputs it to the video ASIC 3. The video ASIC 3 is a block that controls the laser driver ASIC 7 and the MEMS mirror control unit 8 based on the image signal input from the image signal input unit 2 and the scanning position information input from the MEMS mirror 10, and is ASIC (Application Specific Integrated). Circuit). The video ASIC 3 includes a synchronization / image separation unit 31, a bit data conversion unit 32, a light emission pattern conversion unit 33, and a timing controller 34.

The synchronization / image separation unit 31 separates the image data displayed on the image display unit and the synchronization signal from the image signal input from the image signal input unit 2 and writes the image data to the frame memory 4. The bit data converter 32 reads the image data written in the frame memory 4 and converts it into bit data. The light emission pattern conversion unit 33 converts the bit data converted by the bit data conversion unit 32 into a signal representing the light emission pattern of each laser. The timing controller 34 controls the operation timing of the synchronization / image separation unit 31 and the bit data conversion unit 32. The timing controller 34 also controls the operation timing of the MEMS mirror control unit 8 described later.

In the frame memory 4, the image data separated by the synchronization / image separation unit 31 is written. The ROM 5 stores a control program and data for operating the video ASIC 3. Various data are sequentially read from and written into the RAM 6 as a work memory when the video ASIC 3 operates.

The laser driver ASIC 7 is a block that generates a signal for driving a laser diode (LD) provided in a laser light source unit 9 described later, and is configured as an ASIC. The laser driver ASIC 7 includes a red laser driving circuit 71, a blue laser driving circuit 72, and a green laser driving circuit 73. The red laser driving circuit 71 drives the red laser LD1 based on the signal output from the light emission pattern conversion unit 33. The blue laser drive circuit 72 drives the blue laser LD2 based on the signal output from the light emission pattern conversion unit 33. The green laser drive circuit 73 drives the green laser LD3 based on the signal output from the light emission pattern conversion unit 33.

A MEMS (Micro Electro Mechanical Systems) mirror control unit 8 controls the MEMS mirror 10 based on a signal output from the timing controller 34. The MEMS mirror control unit 8 includes a servo circuit 81 and a driver circuit 82. The servo circuit 81 controls the operation of the MEMS mirror 10 based on a signal from the timing controller. The driver circuit 82 amplifies the control signal of the MEMS mirror 10 output from the servo circuit 81 to a predetermined level and outputs the amplified signal.

The laser light source unit 9 mainly functions to emit laser light based on a drive signal output from the laser driver ASIC 7. Specifically, the laser light source unit 9 includes a red laser LD1, a blue laser LD2, a green laser LD3,

dichroic mirrors

91a and 91b, a collimator lens 92, and a MEMS mirror 10.

The red laser LD1 emits red laser light, the blue laser LD2 emits blue laser light, and the green laser LD3 emits green laser light. The dichroic mirror 91a reflects the red laser light and transmits the green laser light, thereby emitting the red laser light and the green laser light to the dichroic mirror 91b. The dichroic mirror 91 b transmits the red laser light and the green laser light and reflects the blue laser light, thereby emitting the red laser light, the blue laser light, and the green laser light to the collimator lens 92. The collimator lens 92 converts red laser light, blue laser light, and green laser light into parallel light and emits the parallel light to the MEMS mirror 10. Hereinafter, when the red laser LD1, the blue laser LD2, and the green laser LD3 are used without being distinguished from each other, they are simply referred to as “laser LD”, and the red laser light, the blue laser light, and the green laser light are used without being distinguished from each other. In this case, it is simply expressed as “laser light”.

The MEMS mirror 10 includes a mirror part 10a, an elastic part 10b, a frame part 10c, and an electromagnetic actuator 10d. The MEMS mirror 10 reflects the laser light incident from the collimator lens 92 toward the screen 11 under the control of the MEMS mirror control unit 8 in order to display the image input to the image signal input unit 2. Specifically, the electromagnetic actuator 10d uses the magnetic force to rotate the mirror unit 10a under the control of the MEMS mirror control unit 8 (specifically, the mirror unit 10a is swung at a predetermined cycle. The angle of the mirror unit 10a is changed at a period of (1) to scan the screen 11 with laser light. At that time, the electromagnetic actuator 10 d outputs the scanning position information to the video ASIC 3. The MEMS mirror 10 corresponds to an example of a “mirror” in the present invention, and the electromagnetic actuator 10d corresponds to an example of a “drive unit” in the present invention.

Here, the MEMS mirror 10 will be specifically described with reference to FIG. FIG. 2 is a diagram illustrating a configuration of the MEMS mirror 10 according to the first embodiment. As shown in FIG. 2, the mirror part 10a is supported by the elastic part 10b, and is configured to be rotatable in the direction indicated by the arrow with respect to the frame part 10c. The elastic part 10b has elasticity that connects the mirror part 10a and the frame part 10c and rotates the mirror part 10a. Specifically, the elastic part 10b has such elasticity that the mirror part 10a is rotated about an axis along one direction as a central axis. Thus, the elastic portion 10b corresponds to a so-called torsion bar. In the first embodiment, the elastic portion 10b is composed of a piezoelectric element that generates a voltage corresponding to the twist generated by the rotation of the mirror portion 10a. The elastic part 10b supplies the voltage generated according to the twist to the abnormality detection circuit 60 as a signal S10.

Referring back to FIG. 1, the abnormality detection circuit 60 will be described. The abnormality detection circuit 60 performs abnormality determination on the scanning operation state of the MEMS mirror 10 based on the signal S10 supplied from the elastic portion 10b of the MEMS mirror 10. Specifically, the abnormality detection circuit 60 determines whether or not an abnormality has occurred in the operation of the mirror unit 10a based on the rotation angle of the mirror unit 10a corresponding to the signal S10 (details of abnormality determination). Will be described later). In this case, the abnormality detection circuit 60 detects the rotation angle of the mirror unit 10a by, for example, amplifying the signal S10 supplied from the elastic unit 10b.

Then, the abnormality detection circuit 60 performs control to stop the irradiation of the laser beam when an abnormality is detected in the operation of the mirror unit 10a. Specifically, the abnormality detection circuit 60 stops the light emission of the laser LD by supplying the control signal S7 to the laser driver ASIC7. The abnormality detection circuit 60 corresponds to an example of “detection means” in the present invention.

(Abnormality judgment method)
Next, the abnormality determination method according to the first embodiment will be described. In the present embodiment, the elastic portion 10b that supports the mirror portion 10a is composed of a piezoelectric element, and the elastic portion 10b is generated by the rotation of the mirror portion 10a. Based on the voltage corresponding to the twist (in other words, the strain of the spring), Abnormality determination is performed on the scanning operation state of the MEMS mirror 10. That is, the abnormality detection circuit 60 treats the voltage change (corresponding to the above-described signal S10) generated by the elastic portion 10b as the operation state of the mirror portion 10a, thereby causing an abnormality in the scanning operation by the mirror portion 10a. Judge whether or not there is.

Specifically, the abnormality detection circuit 60 uses a voltage waveform generated by the elastic portion 10b during normal operation of the mirror portion 10a (hereinafter referred to as a “normal operation waveform”) as a reference, and a voltage obtained from the elastic portion 10b. Abnormality judgment is performed by comparing the waveform with the waveform during normal operation. In this case, when the voltage waveform obtained from the elastic portion 10b substantially matches the waveform during normal operation, the abnormality detection circuit 60 determines that the operation of the mirror portion 10a is normal and is obtained from the elastic portion 10b. When the measured voltage waveform is different from the normal operation waveform, it is determined that the operation of the mirror unit 10a is abnormal. In one example, the abnormality detection circuit 60 is configured using an LPF filter circuit or an HPF filter circuit, and the abnormality determination as described above is performed by processing the voltage waveform of the elastic portion 10b with the LPF filter circuit or the HPF filter circuit. Can be realized. When the abnormality detection circuit 60 determines that the operation of the mirror unit 10a is abnormal, the abnormality detection circuit 60 controls the laser driver ASIC 7 to stop the irradiation of the laser light.

Here, with reference to FIG. 3, a specific example of a voltage waveform obtained from the elastic portion 10b is shown. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the voltage generated by the elastic portion 10 b (that is, the voltage corresponding to the twist of the elastic portion 10 b). FIG. 3A shows an example of a voltage waveform (a waveform during normal operation) obtained from the elastic portion 10b when the mirror unit 10a operates normally. On the other hand, FIG. 3B shows an example of a voltage waveform obtained from the elastic portion 10b when the mirror portion 10a operates abnormally. From FIG. 3B, it can be seen that the magnitude of the voltage is considerably small as compared with the normal operation waveform of FIG. This indicates that the operation (rotation angle) of the mirror unit 10a is considerably smaller than that during normal operation. When the voltage waveform as shown in FIG. 3B is obtained, the abnormality detection circuit 60 determines that the operation of the mirror unit 10a is abnormal by performing the abnormality determination as described above.

Next, the abnormality determination process according to the first embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the abnormality determination process according to the first embodiment. The flow is repeatedly executed at a predetermined cycle when the image display apparatus 1 is operated.

First, in step S101, the MEMS mirror control unit 8 drives the electromagnetic actuator 10d of the MEMS mirror 10. Then, the process proceeds to step S102. When the electromagnetic actuator 10d is driven in this way, the elastic portion 10b is twisted by the rotation of the mirror portion 10a, and the elastic portion 10b as a piezoelectric element generates a voltage corresponding to the twist. The elastic portion 10b supplies the voltage generated according to the twist to the abnormality detection circuit 60 as a signal S10.

In step S102, the abnormality detection circuit 60 acquires a signal S10 corresponding to the voltage generated by the elastic portion 10b. That is, the abnormality detection circuit 60 acquires the voltage waveform generated by the elastic portion 10b. Then, the process proceeds to step S103.

In step S103, the abnormality detection circuit 60 determines whether or not the voltage waveform acquired in step S102 matches the waveform during normal operation. If the acquired voltage waveform substantially matches the waveform during normal operation (step S103: Yes), the process ends. In this case, the operation of the image display device 1 is continued. On the other hand, when the acquired voltage waveform does not match the waveform during normal operation (step S103: No), the process proceeds to step S104. In step S104, the abnormality detection circuit 60 controls the laser driver ASIC 7 so that the irradiation of the laser light is stopped. Then, the process ends.

According to the first embodiment described above, by configuring the elastic portion 10b itself supporting the mirror portion 10a as a piezoelectric element, based on the voltage change due to the twist of the elastic portion 10b caused by the rotation of the mirror portion 10a, Abnormality determination of the scan operation state can be performed appropriately. In addition, according to the first embodiment, since the elastic portion 10b itself is configured as a piezoelectric element to perform abnormality determination, it is not necessary to separately add an angle sensor as described in Patent Document 1 described above. Compared with the configuration described in Patent Document 1, the image display device 1 can be reduced in size and cost.

On the other hand, in the first embodiment, the mirror portion 10a is driven by the electromagnetic actuator 10d, and the operation of the mirror portion 10a is detected by the elastic portion 10b as a piezoelectric element. That is, magnetic force is used for the drive system, and voltage is used for the detection system. Therefore, crosstalk and noise between the drive system signal and the detection system signal can be appropriately reduced.

The elastic portion 10b preferably has a natural frequency that is in a resonance relationship with a frequency in a scanning operation for drawing an image (hereinafter, referred to as “scanning operation frequency” as appropriate). By doing so, the energy required for the scanning operation can be reduced.

In addition, since the piezoelectric element generally has a non-flat frequency characteristic having a voltage peak at a specific frequency, the elastic portion 10b as a piezoelectric element has an output voltage at a frequency that matches the scanning operation frequency. It is preferable that it has the characteristic which becomes a peak. By doing so, the output voltage of the elastic portion 10b generated by the operation of the mirror portion 10a can be increased, and the scan operation state can be easily detected. In addition, the process of amplifying the output voltage of the elastic part 10b can be omitted.

Note that when the laser beam irradiation is stopped when an abnormality is detected as described above, for example, it may be displayed that the laser beam irradiation is stopped due to an abnormality or that the scanning operation state is abnormal. .

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the mirror portion 10a is driven by the electromagnetic actuator 10d, and the operation of the mirror portion 10a is detected by the elastic portion 10b as a piezoelectric element. That is, magnetic force is used for the drive system, and voltage is used for the detection system. In contrast, in the second embodiment, a voltage is used for the drive system and a magnetic force is used for the detection system. Specifically, in the second embodiment, the mirror unit is driven by a voltage, and the operation of the mirror unit is detected based on a magnetic field change.

FIG. 5 shows a configuration of an image display device 1x according to the second embodiment. The same components as those of the image display device 1 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. Further, components and processes not particularly described here are the same as those in the first embodiment.

The image display device 1x according to the second embodiment is different from the image display device 1 according to the first embodiment in that it includes a MEMS mirror 10x instead of the MEMS mirror 10. The MEMS mirror 10x includes a mirror part 10xa, an elastic part 10xb, a frame part 10xc, a piezoelectric actuator 10xd, a magnetic body 10xe, and a Hall element 10xf.

The MEMS mirror 10 x reflects the laser light incident from the collimator lens 92 toward the screen 11 under the control of the MEMS mirror control unit 8 in order to display an image input to the image signal input unit 2. Specifically, the piezoelectric actuator 10xd uses the voltage to rotate the mirror unit 10xa under the control of the MEMS mirror control unit 8 (specifically, the mirror unit 10xa is swung at a predetermined cycle. The angle of the mirror unit 10xa is changed at a period of (1) to scan the screen 11 with laser light. The MEMS mirror 10x corresponds to an example of a “mirror” in the present invention, and the piezoelectric actuator 10xd corresponds to an example of a “driving unit” in the present invention.

Here, the MEMS mirror 10x will be described in detail with reference to FIG. FIG. 6 is a diagram illustrating a configuration of the MEMS mirror 10x according to the second embodiment. As shown in FIG. 6, the mirror portion 10xa is supported by the elastic portion 10xb and is configured to be rotatable in the direction indicated by the arrow with respect to the frame portion 10xc. The elastic part 10xb has elasticity that connects the mirror part 10xa and the frame part 10xc and rotates the mirror part 10xa. Specifically, the elastic part 10xb has such elasticity that the mirror part 10xa is rotated about an axis along one direction as a central axis. Thus, the elastic portion 10xb corresponds to a so-called torsion bar. In the second embodiment, unlike the first embodiment, the elastic portion 10xb is not composed of a piezoelectric element.

The magnetic body 10xe is attached to a surface opposite to the surface irradiated with the laser light in the mirror portion 10xa. Therefore, the magnetic body 10xe moves with the mirror part 10xa. That is, the position of the magnetic body 10xe changes with the rotation of the mirror unit 10xa. The Hall element 10xf is provided at a position where the position is not changed by the rotation of the mirror portion 10xa and the magnetic field generated by the magnetic body 10xe can be detected. For example, the hall element 10xf is provided in the frame portion 10xc. The Hall element 10xf is an element that detects a magnetic field using the Hall effect, and supplies a voltage corresponding to the detected magnetic field to the abnormality detection circuit 60 as a signal S10x. The Hall element 10xf corresponds to an example of “detecting means” in the present invention.

In the configuration of the MEMS mirror 10x in the second embodiment as described above, the position of the magnetic body 10xe changes with the rotation of the mirror portion 10xa, and the Hall element 10xf is provided according to the position change of the magnetic body 10xe. Magnetic field changes occur at different positions. The Hall element 10xf detects such a magnetic field change and supplies a voltage waveform corresponding to the detected magnetic field change to the abnormality detection circuit 60 as a signal S10x. The abnormality detection circuit 60 performs abnormality determination on the scanning operation state of the MEMS mirror 10x based on the signal S10x supplied from the Hall element 10xf. Specifically, the abnormality detection circuit 60 determines whether or not an abnormality has occurred in the scanning operation by the mirror unit 10xa by treating the magnetic field change detected by the Hall element 10xf as the operation state of the mirror unit 10xa. To do.

Specifically, the abnormality detection circuit 60 uses the voltage waveform output by the Hall element 10xf during normal operation of the mirror unit 10xa (hereinafter also referred to as “waveform during normal operation”) as a reference, and from the Hall element 10xf. Abnormality judgment is performed by comparing the obtained voltage waveform with the waveform during normal operation. In this case, when the voltage waveform obtained from the Hall element 10xf substantially matches the waveform during normal operation, the abnormality detection circuit 60 determines that the operation of the mirror unit 10xa is normal and is obtained from the Hall element 10xf. When the measured voltage waveform is different from the waveform during normal operation, it is determined that the operation of the mirror unit 10xa is abnormal. When the abnormality detection circuit 60 determines that the operation of the mirror unit 10xa is abnormal, the abnormality detection circuit 60 supplies the control signal S7 to the laser driver ASIC 7 to stop the emission of the laser LD.

Next, the abnormality determination process according to the second embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing the abnormality determination process according to the second embodiment. This flow is repeatedly executed at a predetermined cycle during the operation of the image display device 1x.

First, in step S201, the MEMS mirror control unit 8 drives the piezoelectric actuator 10xd of the MEMS mirror 10x. Then, the process proceeds to step S202. When the piezoelectric actuator 10xd is driven in this way, the position of the magnetic body 10xe is changed by the rotation of the mirror portion 10xa, and the Hall element 10xf detects a magnetic field change corresponding to the position change of the magnetic body 10xe. Then, the Hall element 10xf supplies a voltage corresponding to the detected magnetic field change to the abnormality detection circuit 60 as a signal S10x.

In step S202, the abnormality detection circuit 60 acquires a signal S10x corresponding to the voltage output from the hall element 10xf. That is, the abnormality detection circuit 60 acquires the voltage waveform output from the Hall element 10xf. Then, the process proceeds to step S203.

In step S203, the abnormality detection circuit 60 determines whether or not the voltage waveform acquired in step S202 matches the waveform during normal operation. If the acquired voltage waveform substantially matches the waveform during normal operation (step S203: Yes), the process ends. In this case, the operation of the image display device 1x is continued. On the other hand, when the acquired voltage waveform does not match the waveform during normal operation (step S203: No), the process proceeds to step S204. In step S204, the abnormality detection circuit 60 controls the laser driver ASIC 7 so that the laser beam irradiation is stopped. Then, the process ends.

According to the second embodiment described above, the abnormality determination of the scanning operation state can be appropriately performed by detecting the magnetic field change according to the position change of the magnetic body 10xe due to the rotation of the mirror portion 10xa by the Hall element 10xf. it can. Further, according to the second embodiment, since the abnormality determination is performed using the magnetic body 10xe and the Hall element 10xf, it is not necessary to add an additional angle sensor as described in Patent Document 1 above. Compared with the configuration described in Document 1, it is possible to reduce the size and cost of the image display device 1x.

On the other hand, in the second embodiment, the mirror unit 10xa is driven by the piezoelectric actuator 10xd, and the operation of the mirror unit 10xa is detected by the Hall element 10xf. That is, a voltage is used for the drive system, and a magnetic field change is used for the detection system. Therefore, crosstalk and noise between the drive system signal and the detection system signal can be appropriately reduced.

It should be noted that in order to further reduce crosstalk and noise from the drive system to the detection system, it may be blocked by an electromagnetic shield so that changes in electric and magnetic fields do not affect each other. In addition, when a magnetic field exists in the vicinity of the mirror portion 10xa, the polarization direction of the laser light is rotated by the Kerr effect in magneto-optical (MO). Therefore, in an apparatus in which the polarization direction affects, a magnetic material is present in the vicinity where the laser light is reflected. A magnetic shield structure may be separately provided so that 10xe does not affect the reflection of laser light.

In addition, it is not limited to attaching the magnetic body 10xe to the surface opposite to the surface irradiated with the laser light in the mirror portion 10xa (see FIG. 6). As long as the laser beam is not irradiated when the image is drawn, the mirror portion 10xa may be attached to such a location. Further, the magnetic body 10xe may be attached to the side surface of the mirror portion 10xa.

In the above example, the magnetic field generated by the magnetic body 10xe is detected by the Hall element 10xf, but a coil is used instead of the Hall element 10xf to detect the magnetic field generated by the magnetic body 10xe. good. In this case, the coil functions as the “detecting means” in the present invention.

[Modification]
In the above description, the abnormality determination is performed by the abnormality detection circuit 60 as hardware, but abnormality determination may be performed by software instead. Specifically, a microcomputer or a DSP (Digital Signal Processor) in the image display device 1 or 1x can perform the abnormality determination as described above. In this case, the microcomputer or the DSP acquires the signal S10 corresponding to the output voltage of the elastic portion 10b or the signal S10x corresponding to the output voltage of the Hall element 10xf, and predetermined for the voltage waveform corresponding to the signal S10 or the signal S10x. By performing this arithmetic processing, the abnormality determination of the scanning operation state is performed. Then, the microcomputer and the DSP control the laser driver ASIC 7 so that the irradiation of the laser beam is stopped when an abnormality is detected.

In the above, the embodiment in which the present invention is applied to a configuration for performing one-dimensional scanning (that is, a configuration in which the mirror units 10a and 10xa are rotated around only one axis as a central axis) has been described. The present invention can also be applied to a configuration that performs dimension scanning. That is, the present invention can be applied to a configuration in which the mirror unit is rotated in two directions defined by the two axes with the two axes as the central axes. In this configuration, two elastic parts are used so as to support the mirror part in the directions of the two axes.

The first embodiment described above can also be applied when using two such elastic portions. That is, the two elastic portions can be configured by piezoelectric elements that generate a voltage corresponding to the twist generated by the rotation of the mirror portion. Also in this case, it is preferable that each of the two elastic portions is configured to have a natural frequency that is in a resonance relationship with the scanning operation frequency. For example, the elastic part used for scanning in the horizontal direction (X-axis direction) is preferably configured with a relatively high natural frequency, and the elastic part used for scanning in the vertical direction (Y-axis direction) It is preferable to use a relatively low natural frequency corresponding to the frame frequency (for example, about 50 to 60 Hz).

The present invention can be used for image display devices such as projectors, head-up displays, and head-mounted displays.

1, 1x image display device 3 Video ASIC
7 Laser driver ASIC
8 MEMS mirror control unit 9 Laser

light source unit

10, 10x MEMS mirror 10a, 10xa mirror unit 10b, 10xb elastic unit 10c, 10xc frame unit 10d Electromagnetic actuator 10xd Piezoelectric actuator 10xe Magnetic body 10xf Hall element 60 Abnormality detection circuit

Claims

A frame part;
A mirror part rotatable with respect to the frame part;
An elastic part that supports the mirror part with respect to the frame part and has elasticity so as to rotate the mirror part;
The mirror is characterized in that the elastic part is composed of a piezoelectric element that generates a voltage corresponding to a twist caused by rotation of the mirror part.
The mirror according to claim 1, further comprising driving means for rotating the mirror portion by magnetic force.
The mirror according to claim 1 or 2, further comprising a detecting means for detecting a rotation angle of the mirror unit based on the voltage.
Applied to image display devices that display images by scanning light from the light source,
4. The mirror according to claim 1, wherein the elastic portion has a natural frequency that is in a resonance relationship with a scanning operation frequency. 5.
Applied to image display devices that display images by scanning light from the light source,
5. The mirror according to claim 1, wherein the elastic portion has a characteristic that an output voltage reaches a peak at a frequency corresponding to a scanning operation frequency. 6.
The mirror according to any one of claims 1 to 5, wherein the elastic part has elasticity to rotate the mirror part about an axis along one direction as a central axis.
A frame part;
A mirror part rotatable with respect to the frame part;
A magnetic body provided in the mirror portion;
And a detecting means for detecting a change in a magnetic field according to a change in the position of the magnetic body caused by the rotation of the mirror section.
The mirror according to claim 7, wherein the detection means detects a rotation angle of the mirror unit based on a change in the magnetic field.
The mirror according to claim 7 or 8, further comprising driving means for rotating the mirror portion by voltage.