Light deflector and image generation device

Abstract

A second light deflector (17) is provided with: a movable part (103) that rotates about a rotating shaft (R2); a second mirror (M2) (scanning mirror) that is disposed on an upper surface of the movable part (103) and that is for scanning light; a projection part (500a) that projects monitor light onto a lower surface (103a) of the movable part (103) or an upper surface of the second mirror (M2); and a light receiving part (500b) that receives the reflected light of the monitor light reflected by the lower surface (103a) or the upper surface of the second mirror (M2). The light receiving part (500b) includes: a two-division photodiode (504) having two light receiving surfaces arranged along the direction in which the reflected light moves by the rotation of the movable part (103); and a mirror (503) (optical element) that condenses the reflected light onto the two light receiving surfaces.

Description

Optical deflector and image generating device

[0001] The present invention relates to an optical deflector and an image generating device including the optical deflector.

[0002] Conventionally, there is known an image generating device that generates an image by scanning light modulated by a video signal. In this device, for example, one frame of an image is generated by scanning the light horizontally in a first period and then scanning the light vertically in a second period longer than the first period. The first period corresponds to one line period of the video signal, and the second period corresponds to the frame period of the video signal.

[0003] In this type of image generating device, light is scanned using a mirror-rotating optical deflector, such as a MEMS (Micro Electro Mechanical Systems) mirror, and a configuration for monitoring the scanning position of the light, i.e., the rotation position of the scanning mirror, is also used.

[0004] In the configuration described in Patent Document 1 below, a PSD (Position Sensitive Detector) is used to monitor the rotational position of the scanning mirror. Specifically, monitoring light is irradiated onto the rear surface of the scanning mirror, and the reflected light is received by the PSD. A detection signal corresponding to the reception position of the reflected light is output from the PSD. As the mirror rotates, the reception position of the reflected light moves. The rotational position of the scanning mirror is detected from the reception position of the reflected light on the PSD.

[0005] Japanese Patent Application Laid-Open No. 2004-144926

[0006] In the image generating device described above, faster mirror drive is required to produce higher-resolution images. However, with the above configuration, the response characteristics of the PSD are relatively slow, so when the scanning mirror is driven at a speed that exceeds this response characteristic, it is difficult to obtain an accurate detection signal. Therefore, it is necessary to consider a method for detecting the mirror rotation position that can meet this demand for higher speeds.

[0007] In view of the above problems, an object of the present invention is to provide an optical deflector and an image generating device that can accurately obtain a detection signal corresponding to the rotational position of a scanning mirror even when the mirror is driven at high speed.

[0008] A first aspect of the present invention relates to an optical deflector. The optical deflector according to this aspect includes a movable part that rotates about a rotation axis, a scanning mirror disposed on the upper surface of the movable part for scanning light, a projection part that projects monitor light onto the lower surface of the movable part or the upper surface of the scanning mirror, and a light receiving part that receives reflected light of the monitor light reflected from the lower surface or the upper surface. The light receiving part includes a two-segment photodiode having two light receiving surfaces aligned along the direction in which the reflected light moves as the movable part rotates, and an optical element that focuses the reflected light onto the two light receiving surfaces. The sizes of the focused light spot and the two light receiving surfaces are set so that, within a rotation detection range for detecting the rotation of the movable part, the focused light spot of the reflected light straddles both of the two light receiving surfaces and does not extend beyond either of the light receiving surfaces at least in the direction in which the reflected light moves.

[0009] In the optical deflector according to this aspect, the focused light spots move on the two light receiving surfaces in the alignment direction in response to the rotation of the scanning mirror. Therefore, the balance of the extent to which the focused light spots fall on the two light receiving surfaces depends on the rotation position of the scanning mirror. As a result, the two sensor units constituting the two-segment photodiode output light receiving signals with a balance of magnitudes depending on the rotation position of the scanning mirror. Therefore, a detection signal depending on the rotation position of the scanning mirror can be generated from these two light receiving signals.

[0010] Furthermore, because the photodiodes have high response characteristics, even when the scanning mirror is driven at high speed, each sensor outputs a light-receiving signal with high response, making it possible to accurately obtain a detection signal corresponding to the rotational position of the mirror, even when the scanning mirror is driven at high speed.

[0011] A second aspect of the present invention relates to an image generating device, comprising the optical deflector according to the first aspect and a control unit that controls the optical deflector based on an output from the two-segment photodiode.

[0012] The image generating device according to this aspect includes the photodetector according to the first aspect, and therefore can accurately obtain a detection signal even when the scanning mirror is driven at high speed, thereby enabling the scanning position of the light to be appropriately controlled based on the detection signal.

[0013] As described above, the present invention can provide an optical deflector and an image generating device that can accurately obtain a detection signal corresponding to the rotational position of the mirror even when the scanning mirror is driven at high speed.

[0014] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below.

[0015] FIG. 1 is a perspective view schematically illustrating the configuration of AR glasses according to an embodiment. FIG. 2 is a diagram schematically illustrating the configuration of an image generation unit according to an embodiment. FIG. 3 is a diagram illustrating the configuration of a circuit unit of an image generation device according to an embodiment. FIG. 4 is a plan view illustrating the configuration of an optical deflection element included in a second optical deflector according to an embodiment. FIG. 5 is a graph illustrating an example of a drive voltage applied to a piezoelectric actuator according to an embodiment. FIG. 6 is a plan view of a second optical deflector including a configuration for detecting the rotation position of a second mirror according to an embodiment. FIG. 7 is a cross-sectional view of a second optical deflector including a configuration for detecting the rotation position of a second mirror according to an embodiment. FIGS. 8(a) and 8(b) are diagrams schematically illustrating methods of forming the reflective surfaces of the mirrors of the projection unit and the light receiving unit, respectively, according to an embodiment. FIGS. 9(a) to 9(c) are diagrams schematically illustrating how a focused spot moves on two light receiving surfaces as the second mirror rotates, respectively, according to an embodiment. FIG. 10 is a graph schematically illustrating the relationship between the rotation angle of the second mirror and the movable unit and a detection signal, according to an embodiment. FIG. 11 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 1. FIG. 12 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 2. FIG. 13 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 3. FIG. 14 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 4. FIG. 15 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 5. FIG. 16 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 6. FIG. 17 is a cross-sectional view of a second optical deflector including a configuration for detecting the rotation position of the second mirror according to another embodiment. FIG. 18 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 7. FIG. 19 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 8. FIG. 20 is a diagram showing an optical system for aligning monitor light with light for image generation according to Modification Example 8. FIG. 21 is a cross-sectional view showing the configurations of a projection unit and a light-receiving unit according to Modification Example 9. FIG. 22 is a cross-sectional view showing the configuration of a projection section and a light receiving section according to the tenth modification.

[0016] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] The following embodiment shows an example in which the present invention is applied to an image generation device for AR glasses. However, the following embodiment is one embodiment of the present invention, and the present invention is not limited to the following embodiment. For example, the present invention is not limited to an image generation device for AR glasses, but can also be applied to image generation devices such as AR goggles, VR glasses, VR goggles, and in-vehicle head-up displays.

[0019] Fig. 1 is a perspective view that schematically illustrates the configuration of AR glasses 1. In Fig. 1, the front, back, left, right, top, and bottom directions of the AR glasses 1 are indicated.

[0020] The AR glasses 1 include a frame 2 and a pair of image generation devices 3. The pair of image generation devices 3 are symmetrical in the left-right direction. The image generation device 3 includes an image generation unit 4, a half mirror 5, and a detection unit 6. The AR glasses 1 are worn on the user's head, similar to regular eyeglasses.

[0021] The frame 2 is composed of a front portion 2a and a pair of support portions 2b. The pair of support portions 2b extend rearward from the right and left ends of the front portion 2a. When the frame 2 is worn by a user, the front portion 2a is positioned in front of the user's pair of eyes E. The front portion 2a is made of a transparent material (for example, resin, etc.).

[0022] The image generating unit 4 is disposed on the inner surface of the support portion 2b. The image generating unit 4 projects light modulated by a video signal onto the corresponding half mirror 5.

[0023] The half mirror 5 is installed on the inner surface of the front surface 2a. The half mirror 5 reflects light projected from the corresponding image generation unit 4 to the user's eye E, and transmits light traveling in the forward and backward directions. The light from the image generation unit 4 reflected by the half mirror 5 is irradiated onto the fovea centralis, which is located at the center of the retina in the eye E. This allows the user to visually grasp the frame image 20 (see FIG. 2) generated by the image generation device 3. Furthermore, because the user can see what is in front of the AR glasses 1 through the half mirror 5, the user can visually grasp the state in front of the AR glasses 1 superimposed on the frame image 20 generated by the image generation device 3.

[0024] The pair of detectors 6 are installed on the inner surface of the front surface 2a and positioned between the pair of half mirrors 5. The detectors 6 are used to detect the line of sight of the user. The detection of the line of sight of the user will be described later with reference to FIG. 3.

[0025] FIG. 2 is a diagram schematically showing the configuration of the image generating unit 4. As shown in FIG.

[0026] The image generating unit 4 includes light sources 11a, 11b, and 11c, collimator lenses 12a, 12b, and 12c, apertures 13a, 13b, and 13c, a mirror 14a, dichroic mirrors 14b and 14c, a first optical deflector 15, a relay optical system 16, and a second optical deflector 17.

[0027] The light sources 11a, 11b, and 11c are, for example, semiconductor lasers. The light source 11a emits laser light with a red wavelength in the range of 635 nm to 645 nm, the light source 11b emits laser light with a green wavelength in the range of 510 nm to 530 nm, and the light source 11c emits laser light with a blue wavelength in the range of 440 nm to 460 nm.

[0028] In this embodiment, a color image is generated as the frame image 20 described below, and therefore the image generation unit 4 is provided with light sources 11a, 11b, and 11c capable of emitting red, green, and blue laser light. When a monochromatic image is displayed as the frame image 20, the image generation unit 4 may be provided with only one light source corresponding to the color of the image. Alternatively, the image generation unit 4 may be configured to include two light sources with different emission wavelengths.

[0029] The light beams emitted from the light sources 11a, 11b, and 11c are converted into parallel light beams by the collimator lenses 12a, 12b, and 12c, respectively. The light beams transmitted through the collimator lenses 12a, 12b, and 12c are shaped into approximately circular beams by the apertures 13a, 13b, and 13c, respectively.

[0030] Mirror 14a almost totally reflects the red light that has passed through aperture 13a. Dichroic mirror 14b reflects the green light that has passed through aperture 13b and transmits the red light reflected by mirror 14a. Dichroic mirror 14c reflects the blue light that has passed through aperture 13c and transmits the red and green light that have passed through dichroic mirror 14b. Mirror 14a and the two dichroic mirrors 14b and 14c are positioned to align the optical axes of the light of each color emitted from light sources 11a, 11b, and 11c.

[0031] The first optical deflector 15 reflects the light that has passed through the dichroic mirror 14c. The first optical deflector 15 is, for example, a MEMS (Micro Electro Mechanical System) mirror. The first optical deflector 15 is configured to rotate a first mirror M1 (scanning mirror), onto which the light that has passed through the dichroic mirror 14c is incident, around a rotation axis R1 that is parallel to the vertical direction in response to a drive signal. The rotation of the first mirror M1 changes the reflection direction of the light. As a result, the light reflected by the first mirror M1 is scanned in the left-right direction (horizontal direction) on the retina of the eye E.

[0032] The relay optical system 16 directs the light reflected by the first optical deflector 15 toward the center of the second mirror M2 (scanning mirror) of the second optical deflector 17. That is, the light incident on the first optical deflector 15 is deflected by the first mirror M1 at a predetermined deflection angle. The relay optical system 16 directs the light at each deflection angle toward the center of the second mirror M2. The relay optical system 16 has multiple mirrors, and reflects the light reflected by the first optical deflector 15 by the multiple mirrors to direct the light toward the second optical deflector 17. This makes it possible to achieve a long optical path length within the relay optical system 16 and reduce the deflection angle of the light when viewed from the second mirror M2.

[0033] The second optical deflector 17 reflects the light that has passed through the relay optical system 16. The second optical deflector 17 is a MEMS mirror. The second optical deflector 17 rotates a second mirror M2, onto which the light that has passed through the relay optical system 16 is incident, around a rotation axis R2 that is parallel to the left-right direction in response to a drive signal. The rotation of the second mirror M2 changes the reflection direction of the light. As a result, on the retina of the eye E, the light that is scanned in the left-right direction (horizontal direction) by the first optical deflector 15 is also scanned in the up-down direction (vertical direction).

[0034] The configuration of the second optical deflector 17 will be described later with reference to FIGS.

[0035] The light reflected by the second optical deflector 17, i.e., the light emitted from the image generation unit 4, is reflected by the half mirror 5 and forms a frame image 20 on the retina of the eye E. That is, the light modulated by the video signal (light emitted from the light sources 11a to 11c) is scanned horizontally (left and right) and vertically (up and down) by the first optical deflector 15 and the second optical deflector 17, so that one frame of the frame image 20 is formed on the retina of the eye E.

[0036] FIG. 3 is a diagram showing the configuration of the circuit section of the image generating device 3.

[0037] The detection unit 6 includes a light source 61 and an image sensor 62, and is connected to the control unit 41 of the image generation unit 4. The light source 61 is, for example, an LED that emits light of an infrared wavelength. The image sensor 62 is, for example, a CMOS image sensor or a CCD image sensor. The light source 61 irradiates light onto the user's eye E in response to an instruction from the control unit 41. The image sensor 62 captures an image of the user's eye E in response to an instruction from the control unit 41, and outputs the captured image to the control unit 41.

[0038] The image generating unit 4 includes a control unit 41 , a first mirror driving circuit 42 , a second mirror driving circuit 43 , a laser driving circuit 44 , and a mirror detecting circuit 45 .

[0039] The control unit 41 includes an arithmetic processing unit such as a CPU or FPGA, and a memory. The control unit 41 processes video signals from an external device and controls each unit of the image generation unit 4. The control unit 41 also detects the user's line of sight based on the captured image from the detection unit 6, for example, by the dark pupil method, the bright pupil method, or the corneal reflex method. Based on the detected line of sight of the user, the control unit 41 acquires the viewpoint position in the frame image 20 formed on the user's retina.

[0040] The first mirror driving circuit 42 drives the first mirror M1 of the first optical deflector 15 in response to a driving signal from the control unit 41. The second mirror driving circuit 43 drives the second mirror M2 of the second optical deflector 17 in response to a driving signal from the control unit 41.

[0041] The mirror detection circuit 45 outputs a detection signal corresponding to the driving state of the second mirror M2 in the second optical deflector 17, i.e., the scanning position of the light in the vertical direction (up and down direction), to the control unit 41. A method for generating the detection signal in the mirror detection circuit 45 will be described later with reference to FIGS.

[0042] The control unit 41 outputs a drive signal to the second mirror drive circuit 43 so that the second mirror M2 rotates in the vertical direction (up and down direction) with a desired drive waveform based on the detection signal from the mirror detection circuit 45. Furthermore, the control unit 41 controls the second mirror drive circuit 43 based on the line of sight of the user detected by the detection unit 6 and the detection signal from the mirror detection circuit 45 so that the frame image 20 is depicted at the position of the line of sight.

[0043] The image generating device 3 may further include a detection circuit that detects the driving state of the first mirror M1 in the first optical deflector 15, i.e., the scanning position of the light in the horizontal direction (left-right direction). In this case, the control unit 41 controls the first mirror driving circuit 42 based on a detection signal from the detection circuit so that the first mirror M1 rotates in the horizontal direction (left-right direction) with a desired driving waveform.

[0044] 4 is a plan view showing the configuration of the optical deflection element 100 included in the second optical deflector 17. X, Y, and Z axes, which are orthogonal to each other, are indicated in FIG. 4. The positive direction of the X axis corresponds to the right direction in FIG. 1.

[0045] 4, in this embodiment, the second optical deflector 17 includes a meandering MEMS mirror (optical deflection element 100). However, the optical deflection element 100 is not limited to a meandering MEMS mirror, and may be an optical deflection element of another configuration.

[0046] The optical deflection element 100 includes a support portion 101, a pair of drive portions 102, and a movable portion 103. The support portion 101 is a frame-shaped member having a predetermined thickness, and is formed of, for example, a silicon substrate. In a plan view, the support portion 101 has a rectangular outline.

[0047] The driving unit 102 includes a substrate 110 having one end connected to the support unit 101 and the other end connected to the movable unit 103, and four piezoelectric actuators 111 formed on the upper surface of the substrate 110. The substrate 110 has a meandering shape that snakes in a direction perpendicular to the rotation axis R2. The thickness of the substrate 110 is constant. The substrate 110 is formed integrally with the support unit 101 using the same material as the support unit 101.

[0048] The four piezoelectric actuators 111 are respectively disposed on the upper surface of four regions 110a of the substrate 110, which extend in a direction perpendicular to the rotation axis R2 (the Y-axis direction). Each piezoelectric actuator 111 has a structure in which a piezoelectric body of a certain thickness is sandwiched between an upper electrode and a lower electrode.

[0049] The piezoelectric body is made of, for example, PZT (lead zirconate titanate). The upper electrode and the lower electrode are made of, for example, platinum. When a voltage (drive signal) is applied between the upper electrode and the lower electrode, the piezoelectric actuator 111 (piezoelectric body) expands and contracts. This causes the substrate 110 to bend, generating a drive force for driving the movable part 103.

[0050] The movable part 103 is supported by a pair of drive parts 102. The movable part 103 is formed integrally with the substrate 110 and the support part 101 using the same material as the substrate 110 of the drive part 102. In a plan view, the movable part 103 is circular. The shape of the movable part 103 may be other shapes, such as a square. The thickness of the movable part 103 is the same as that of the substrate 110. Therefore, the movable part 103 has a disk shape. The above-mentioned second mirror M2 is formed on the upper surface of the movable part 103. If the reflectivity of the upper surface of the movable part 103 is high, the upper surface of the movable part 103 may serve as the second mirror M2.

[0051] When drive voltages of the same phase are applied to the odd-numbered piezoelectric actuators 111 from the movable part 103 side, the piezoelectric bodies of these piezoelectric actuators 111 deform, and the odd-numbered substrates 110 (regions 110a) vibrate so as to bend. At this time, a drive voltage of the opposite phase to the drive voltage applied to the odd-numbered piezoelectric actuators 111 is applied to the even-numbered piezoelectric actuators 111 from the movable part 103 side. This deforms the piezoelectric bodies in the piezoelectric actuators 111, and the even-numbered substrates 110 (regions 110a) deform so as to bend. In this way, the deformation of each substrate 110 causes the movable part 103 to rotate about the rotation axis R2.

[0052] FIG. 5 is a graph showing an example of the drive voltage applied to the piezoelectric actuator 111. As shown in FIG.

[0053] As described above, when the drive voltage of Figure 5 is applied to the odd-numbered piezoelectric actuators 111, a drive voltage of the opposite phase to that of Figure 5 is applied to the even-numbered piezoelectric actuators 111. In Figure 5, the horizontal axis represents time and the vertical axis represents voltage. The vertical and horizontal axes are both normalized.

[0054] In Figure 5, T0 is one period of the drive voltage. That is, the second mirror M2 rotates repeatedly during this period T0. Within this period T0, a period ΔT is the image drawing period. That is, during the period ΔT, the light sources 11a to 11c emit light modulated by a video signal, and vertical scanning for image drawing is performed by the second mirror M2.

[0055] In the waveform of Figure 5, the drive voltage waveform is changed sharply. That is, the scanning speed of the second mirror M2 is changed in some areas. This causes the number of images to increase or decrease in some areas. During periods when the scanning speed of the second mirror M2 is slow, the number of images to be drawn in the scanning direction of the second mirror M2 increases. This period corresponds to the scanning range including the line of sight. Therefore, the density of the frame image 20 in the range including the line of sight is increased, allowing the user to see the image more clearly.

[0056] The image generating device 3 configured as described above uses a configuration for monitoring the scanning position of light in the vertical direction, i.e., the rotation position of the second mirror M2 (scanning mirror) in the second optical deflector 17. This makes it possible to adjust the scanning speed of the mirror at an appropriate imaging position. In this case, for example, a configuration can be used in which monitoring light is irradiated onto the back surface (the surface on the negative side of the Z axis) of the movable part 103 and the reflected light is received by a PSD.

[0057] However, in this configuration, because the PSD has a relatively gradual response characteristic, it becomes difficult to obtain an accurate detection signal when the speed of the second mirror M2 (scanning mirror) is controlled steeply using a drive voltage waveform that includes high-frequency components exceeding this response characteristic. For example, when the second mirror M2 is controlled using a drive voltage waveform that includes high-frequency components of approximately 100 kHz, the detection signal from the PSD becomes rounded at the timing of the drive voltage switch, indicated by the dashed circle in Figure 5. In the image generating device 3 configured as described above, steep speed control of the second mirror M2 (e.g., approximately 100 kHz) is required to produce a higher-resolution image.

[0058] Therefore, in this embodiment, a method for detecting the rotation position that can meet the demand for higher speeds is used.

[0059] Fig. 6 is a plan view of the second optical deflector 17 including a configuration for detecting the rotational position of the second mirror M2. Fig. 7 is a cross-sectional view of the second optical deflector 17 of Fig. 6 taken along a plane parallel to the YZ plane at position A-A. In Fig. 7, the outer edge of the monitor light emitted from the light source 501 is indicated by a dashed line, and the optical axis of the monitor light is indicated by a dashed line.

[0060] 6 and 7 , the optical deflection element 100 is mounted in a frame member 200. The frame member 200 has a rectangular shape that is long in the X-axis direction in a plan view, and has a rectangular recess 201 into which the optical deflection element 100 fits. The frame member 200 has a constant thickness, and the recess 201 has a constant depth. A rectangular opening 202 is formed in the recess 201 that surrounds the drive unit 102 and the movable unit 103 of the optical deflection element 100 in a plan view. The optical deflection element 100 is mounted in the recess 201 with an adhesive or the like.

[0061] Circuit boards 301a and 301b and a support member 400 are installed on the underside of the frame member 200. A light source 501 for emitting monitor light and a drive circuit for driving the light source 501 are arranged on the circuit board 301a. This drive circuit is included in the mirror detection circuit 45 of FIG. 3. The light source 501 is formed of, for example, a light emitting diode. The light source 501 may also be a semiconductor laser. The light source 501 emits monitor light downward (negative direction of the Z axis).

[0062] The circuit board 301b is provided with a two-segment photodiode 504 and a processing circuit that processes light-receiving signals from the two-segment photodiode 504. This processing circuit is included in the mirror detection circuit 45 in FIG. 3. The two-segment photodiode 504 has two light-receiving surfaces aligned in the Y-axis direction. That is, the light-receiving surface of the two-segment photodiode 504 is divided into two in the Y-axis direction by a dividing line parallel to the X-axis. The two light-receiving surfaces face downward (negative Z-axis direction).

[0063] The two-segment photodiode 504 has a sensor unit for each light-receiving surface. These two sensor units output light-receiving signals whose magnitude corresponds to the amount of light received by the corresponding light-receiving surface. The processing circuit described above processes these light-receiving signals to generate detection signals that correspond to the rotational position of the second mirror M2. The configuration of the two-segment photodiode 504 and the method for generating the detection signals will be described later with reference to FIGS. 9(a) to 9(c) and 10.

[0064] The support member 400 has a box shape with an open top. The support member 400 is made of a light-blocking and highly rigid material such as SUS. In a plan view, the outline of the support member 400 is the same as the outline of the frame member 200. A recess 401 that is rectangular in plan view is formed in the support member 400. Mirrors 502 and 503 are installed in this recess 401.

[0065] The reflecting surface 502a of the mirror 502 has a concave shape that focuses the monitor light emitted from the light source 501 onto the lower surface 103a of the movable part 103. The reflecting surface 503a of the mirror 503 has a concave shape that focuses the monitor light reflected by the lower surface 103a of the movable part 103 into a focused spot. The light source 501, mirrors 502 and 503, and two-segment photodiode 504 are positioned on a common plane that passes through the center of the optical deflection element 100 in the X-axis direction and is perpendicular to the rotation axis R2. In other words, the light source 501, mirrors 502 and 503, and two-segment photodiode 504 are arranged so that the optical axis of the monitor light traveling from the light source 501 to the two-segment photodiode 504 is included in this plane.

[0066] Note that this arrangement is just one example, and for example, the light source 501, mirrors 502 and 503, and two-segment photodiode 504 may be arranged on a plane parallel to the rotation axis R2 of the second mirror M2. In this case, too, the two light-receiving surfaces of the two-segment photodiode 504 are arranged so that they are aligned in the Y-axis direction. In this configuration, components can be arranged in the longitudinal direction of the optical deflection element 100, thereby reducing the overall footprint.

[0067] 8A and 8B are diagrams schematically showing methods for forming the reflecting surfaces 502a and 503a of the mirrors 502 and 503, respectively.

[0068] As shown in FIG. 8A, the reflecting surface 502a of the mirror 502 has a shape that follows an ellipsoid of revolution formed by rotating an ellipse S1, which includes on its major axis L1 the light-emitting point F11 of the light source 501 and the focus F12 of the monitor light set on the lower surface 103a of the movable part 103, about the major axis L1.

[0069] 8A, when one ridge of the reflecting surface 502a is shaped to follow a part of the ellipse S1, light emitted from a light-emitting point F11 on the major axis L1 of the ellipse S1 is focused by the reflecting surface 502a to a focal point F12 on the major axis L1. Conversely, light emitted from the focal point F12 is focused by the reflecting surface 502a to the light-emitting point F11.

[0070] Here, a first focal length from the reflecting surface 502a to the light-emitting point F11 and a second focal length from the reflecting surface 502a to the focal point F12 change depending on the ratio between the major axis L1 and the minor axis of the ellipse S1. In other words, the ratio between the major axis L1 and the minor axis changes depending on the lengths of the first focal length and the second focal length, and the shape of the ellipse S1 also changes. Accordingly, the shape of the ridge line of the reflecting surface 502a also changes.

[0071] Here, the light emitting point of the light source 501 is set at the light emitting point F11, and the focal point F12 is set at the lower surface 103a of the movable part 103. As a result, the monitor light emitted from the light source 501 is reflected and collected by the reflecting surface 502a of the mirror 502, and is focused on the lower surface 103a of the movable part 103. The focal point F12 of the monitor light is set at the center of the lower surface 103a of the movable part 103, for example.

[0072] 8B, the reflecting surface 503a of the mirror 503 has a shape that follows an ellipsoid of revolution that is formed by rotating, about the major axis L2, an ellipse S2 that includes, on its major axis L2, the focus F12 set on the lower surface 103a of the movable part 103 and the focus F13 of the monitor light. As a result, based on the same principle as above, the reflected light of the monitor light reflected by the lower surface 103a of the movable part 103 is reflected and condensed by the reflecting surface 503a of the mirror 503, and focused at the focus F13.

[0073] Here, the focus F13 of the reflected light is positioned at a position that is offset from the two light-receiving surfaces of the two-segment photodiode 504 in the direction perpendicular to these light-receiving surfaces. In the example of FIG. 8B , the focus F13 is positioned on the far side of the light-receiving surfaces of the two-segment photodiode 504 in the direction of propagation of the reflected light. The focus F13 may also be positioned on the near side of the light-receiving surfaces of the two-segment photodiode 504 in the direction of propagation of the reflected light. In other words, the reflected monitor light is focused on the light-receiving surfaces of the two-segment photodiode 504 in an off-focus state. As a result, a focused spot of the reflected light that is larger than the focus is positioned on the two light-receiving surfaces.

[0074] 7, the light source 501 and the mirror 502 constitute a projection unit 500a that projects monitor light onto the lower surface 103a of the movable part 103, and the mirror 503 and the two-segment photodiode 504 constitute a light-receiving unit 500b that receives the reflected light of the monitor light reflected by the lower surface 103a of the movable part 103. The mirror 502 is also used as an optical element that focuses the monitor light emitted from the light source 501 onto the lower surface 103a of the movable part 103, and the mirror 503 is also used as an optical element that collects the reflected light of the monitor light reflected by the lower surface 103a of the movable part 103 onto the two light-receiving surfaces of the two-segment photodiode 504.

[0075] 7, it is assumed that the lower surface 103a of the movable part 103 has a reflectivity sufficient to guide a sufficient amount of reflected light to the light-receiving surface of the two-segment photodiode 504. On the other hand, if it is not possible to guide a sufficient amount of reflected light to the light-receiving surface of the two-segment photodiode 504, the area of ​​the lower surface 103a onto which the monitor light is irradiated may be given a mirror finish, or a separate reflective film may be formed.

[0076] 7, when the second mirror M2 rotates about the rotation axis R2 together with the movable part 103, the focused spot of the reflected light focused on the light receiving surface of the two-segment photodiode 504 moves in the Y-axis direction, i.e., in the direction in which the two light receiving surfaces are aligned. Therefore, the degree to which the focused spot fits onto the two light receiving surfaces changes depending on the rotation position of the second mirror M2.

[0077] 9(a) to 9(c) are diagrams showing the movement of the focused spot SP1 on the light receiving surfaces Da and Db as the second mirror M2 rotates. The upper rows of FIGS. 9(a) to 9(c) show a diagram of the two-segment photodiode 504 as seen from the side, and the lower rows of FIGS. 9(a) to 9(c) show a diagram of the two-segment photodiode 504 as seen from above.

[0078] Fig. 9(a) shows the state when the second mirror M2 is near one boundary of the rotation detection range, Fig. 9(c) shows the state when the second mirror M2 is near the other boundary of the rotation detection range, and Fig. 9(c) shows the state when the second mirror M2 is in the neutral position (the position in Fig. 7).

[0079] Here, the rotation detection range refers to a range for detecting the rotation of the second mirror M2 and the movable part 103. The rotation detection range can be set to be slightly wider than the ideal rotation range in which the second mirror M2 and the movable part 103 rotate in the period T0 in FIG.

[0080] 9A to 9C, the two-segment photodiode 504 has two light-receiving surfaces Da and Db aligned in the Y-axis direction. The two-segment photodiode 504 includes two sensor units 504a and 504b, each having two light-receiving surfaces Da and Db. The light-receiving surfaces Da and Db have the same shape and size. The dividing line between the light-receiving surfaces Da and Db is parallel to the X-axis direction. The focused spot SP1 of the reflected light B1 moves in the alignment direction of the light-receiving surfaces Da and Db (the Y-axis direction) in response to the rotation of the second mirror M2 and the movable unit 103.

[0081] 9A to 9C, the sizes of the light-receiving surfaces Da and Db are set so that the light-receiving spot SP1 of the reflected light B1 straddles both of the two light-receiving surfaces Da and Db and does not protrude from either of the light-receiving surfaces Da and Db in at least the Y-axis direction within the rotation detection range. In the example of Figures 9A to 9C, the sizes of the light-receiving surface Da and Db are set so that the light-receiving spot SP1 does not protrude from either of the light-receiving surfaces Da and Db in not only the Y-axis direction but also the X-axis direction within the rotation detection range.

[0082] In the state shown in Fig. 9(a), the second mirror M2 and the movable part 103 are rotated significantly in one direction, so that the focused spot SP1 of the reflected light B1 straddles the light-receiving surfaces Da and Db such that the majority of the focused spot SP1 is included on the light-receiving surface Da. In the state shown in Fig. 9(c), the second mirror M2 and the movable part 103 are rotated significantly in the other direction, so that the focused spot SP1 of the reflected light B1 straddles the light-receiving surfaces Da and Db such that the majority of the focused spot SP1 is included on the light-receiving surface Db. In the state shown in Fig. 9(b), the second mirror M2 and the movable part 103 are in a neutral position, so that the focused spot SP1 of the reflected light B1 straddles the light-receiving surfaces Da and Db evenly such that half of the focused spot SP1 is included on each of the light-receiving surfaces Da and Db.

[0083] The position of the two-segment photodiode 504 is adjusted so that the focused spot SP1 falls evenly on the light receiving surfaces Da and Db when the second mirror M2 and the movable portion 103 are in the neutral position.

[0084] In this way, the extent to which the focused spot SP1 falls on the two light receiving surfaces Da, Db changes depending on the rotational positions of the second mirror M2 and the movable part 103. Therefore, the rotational positions of the second mirror M2 and the movable part 103 can be detected based on the extent to which the focused spot SP1 falls on the two light receiving surfaces Da, Db, i.e., the balance between the magnitudes of the light receiving signals output from the two sensor units 504a, 504b.

[0085] FIG. 10 is a graph showing a schematic relationship between the rotation angles of the second mirror M2 and the movable portion 103 and the detection signal.

[0086] Here, the detection signal is calculated by the following formula:

[0087] Detection signal = (PD Ａ -PD Ｂ ) / (PD Ａ +PD Ｂ ) … (1)

[0088] In formula (1), PD Ａ is the magnitude of the light receiving signal output from one sensor unit 504a, and PD Ｂ is the magnitude of the light receiving signal output from the other sensor unit 504b. Ａ , P.D. Ｂ The difference is the received light signal PD Ａ , P.D. Ｂ This makes it possible to suppress variations in the detection signal due to variations in the intensity of the reflected light B1.

[0089] 10, an angle of zero indicates that the second mirror M2 and the movable part 103 are in a neutral position, and the range of positive and negative angles is the range in which the second mirror M2 and the movable part 103 rotate in one direction and the other direction from the neutral position. The angle range in which the detection signal is parallel to the angle axis corresponds to the angle range in which the focused spot SP1 is included in only one of the two light receiving surfaces Da and Db.

[0090] 10, the detection signal changes almost linearly in the rotation detection range from the minimum angle θmin to the maximum angle θmax in accordance with the change in the rotation angle of the second mirror M2 and the movable part 103. Therefore, the rotation positions of the second mirror M2 and the movable part 103 can be detected from the detection signal in the rotation detection range.

[0091] The mirror detection circuit 45 in FIG. 3 detects light reception signals PD output from two sensor portions 504a and 504b of a two-segment photodiode 504. Ａ , P.D. Ｂ The mirror detection circuit 45 amplifies and removes noise from the received light signal PD Ａ , P.D. Ｂ is A / D converted at a predetermined sampling period, and the converted digital signal is used to perform the calculation of the above equation (1). In this way, the mirror detection circuit 45 sequentially outputs digital detection signals to the control unit 41 at each sampling timing.

[0092] The control unit 41 monitors the actual rotation positions of the second mirror M2 and the movable unit 103 from the received detection signal based on the graph of Fig. 10 and controls the second mirror drive circuit 43 so that the actual rotation positions conform to the ideal waveform of Fig. 5. The rotation positions may be obtained by calculation based on the graph of Fig. 10, or may be obtained using a table that previously associates angles with the magnitude of the detection signal. In this way, the second mirror M2 and the movable unit 103 rotate in an ideal rotation state.

[0093] 3, the detection signal is generated by the mirror detection circuit 45, but the detection signal may be generated in the control unit 41. In this case, the mirror detection circuit 45 generates the light receiving signals PD Ａ , P.D. Ｂ The control unit 41 receives the digital light reception signal PD sequentially from the processing circuit and amplifies and removes noise, and performs A / D conversion on the digital light reception signal PD. Ａ , P.D. ＢThen, the control unit 41 uses this control signal to perform the above-mentioned control on the second mirror driving circuit 43.

[0094] <Effects of the embodiment> According to the above embodiment, the following effects are achieved.

[0095] As shown in Figures 9(a) to 9(c), as the second mirror M2 (scanning mirror) rotates, the focused spot SP1 moves on the two light receiving surfaces Da and Db in the alignment direction. Therefore, the balance of the extent to which the focused spot SP1 falls on the two light receiving surfaces Da and Db depends on the rotational position of the second mirror M2 (scanning mirror). Therefore, the two sensor units 504a and 504b constituting the two-segment photodiode 504 each output a light receiving signal with a balance of magnitudes depending on the rotational position of the second mirror M2 (scanning mirror). Therefore, from these two light receiving signals, a detection signal depending on the rotational position of the second mirror M2 (scanning mirror) can be generated using the above equation (1).

[0096] Furthermore, because the response characteristics of the two-segment photodiode 504 are high, even if the second mirror M2 (scanning mirror) is driven at high speed, light reception signals are output from the sensors 504a and 504b with high response. Therefore, even when the second mirror M2 (scanning mirror) is driven at high speed, a detection signal corresponding to the rotational position of the second mirror M2 (scanning mirror) can be accurately obtained.

[0097] 7, the light receiving unit 500b includes a mirror 503 that reflects the reflected monitor light and directs it toward the two-segment photodiode 504. In this way, the reflected monitor light is turned back by the mirror 503 and directed toward the two-segment photodiode 504, thereby making it possible to reduce the size of the light receiving unit 500b in the height direction. This allows the second optical deflector 17 (optical deflector) to have a compact shape.

[0098] 7, the reflecting surface 503a of the mirror 503 has a concave shape that focuses the reflected monitor light onto a light spot SP1, and the mirror 503 is also used as an optical element that focuses the reflected monitor light onto two light-receiving surfaces Da and Db. This reduces the number of components in the light-receiving unit 500b and simplifies the configuration of the second optical deflector 17 (optical deflector).

[0099] 7, the projection unit 500a includes a mirror 502 (another optical element) that focuses the monitor light on the lower surface 103a of the movable unit 103, and the reflecting surface 503a of the mirror 503 on the light-receiving unit 500b side has a shape that follows an ellipsoid of revolution formed by rotating, about the major axis L2, an ellipse S2 that includes the focus F12 of the monitor light on its major axis L2, as shown in FIG. 8B, and the focus F13 of the reflected light that falls on the major axis L2 is positioned at a position that is offset from the two light-receiving surfaces of the two-segment photodiode 504 in a direction perpendicular to these light-receiving surfaces. This allows the reflecting surface 503a to properly focus the monitor light reflected by the lower surface 103a of the movable unit 103 onto the light-receiving surfaces Da and Db of the two-segment photodiode 504.

[0100] 7, the projection unit 500a includes a light source 501 that emits monitor light, and a mirror 502 (another optical element) that focuses the monitor light emitted from the light source 501 on the lower surface 103a of the movable unit 103. This significantly reduces the area of ​​the lower surface 103a onto which the monitor light is irradiated, thereby increasing the degree of freedom in designing the optical deflection element 100.

[0101] 7, the projection unit 500a includes a mirror 502 that reflects the monitor light emitted from the light source 501 and directs it toward the lower surface 103a of the movable unit 103. In this way, by turning the monitor light back at the mirror 502 and directing it toward the lower surface 103a of the movable unit 103, the projection unit 500a can be made smaller in height. This allows the second optical deflector 17 (optical deflector) to have a compact shape.

[0102] 7, the reflecting surface 502a of the mirror 502 has a concave shape that focuses the monitor light on the lower surface 103a of the movable part 103, and the mirror 502 is also used as another optical element that focuses the monitor light on the lower surface 103a of the movable part 103. This makes it possible to reduce the number of parts in the projection part 500a and simplify the configuration of the second optical deflector 17 (optical deflector).

[0103] 8A, the reflecting surface 502a of the mirror 502 has a shape that follows an ellipsoid of revolution formed by rotating an ellipse S1, which has a major axis L1 including the light-emitting point F11 of the light source 501 and the focal point F12 of the monitor light, about the major axis L1. This allows the monitor light emitted from the light source 501 to be properly focused on the lower surface 103a of the movable part 103.

[0104] 6 and 7, the projection unit 500a and the light receiving unit 500b are placed in the recess 401 of the support member 400 made of a light-blocking material, and are surrounded by the support member 400. This makes it difficult for stray light to enter the two-segment photodiode 504, and a detection signal corresponding to the rotational position of the second mirror M2 can be obtained with high accuracy.

[0105] <Modification 1> The configurations of the projection unit 500a and the light receiving unit 500b are not limited to those in the above embodiment, and various modifications are possible.

[0106] FIG. 11 is a cross-sectional view showing the configuration of a projection unit 500a and a light receiving unit 500b according to the first modification.

[0107] 11, hatching is omitted for the components that make up the projection unit 500a and the light receiving unit 500b, and the support member 400 is also omitted. The recess 401 of the support member 400 is only required to be configured to be able to support the optical components of the projection unit 500a and the light receiving unit 500b. These points are the same in the second and subsequent modifications.

[0108] In the first modification, the monitor light emitted from the light source 501 is irradiated onto the lower surface 103a of the movable part 103 without being focused. The monitor light reflected by the lower surface 103a of the movable part 103 is focused by the lens 511 onto the light-receiving surfaces Da and Db of the two-segment photodiode 504. The focus F21 of the reflected light is positioned on the far side of the light-receiving surfaces Da and Db in the direction of travel of the reflected light. The optical axis of the monitor light traveling from the light source 501 to the two-segment photodiode 504 is included in a common plane parallel to the Y-Z plane. The two light-receiving surfaces Da and Db are aligned in the direction in which the focused spot SP1 moves due to the rotation of the movable part 103. When the movable part 103 is in the neutral position, the optical axis of the reflected light passes through the dividing line between the light-receiving surfaces Da and Db, perpendicular to the plane including the light-receiving surfaces Da and Db, as in the case of FIG. 9B.

[0109] 9A to 9C, with this configuration, the focused spot SP1 moves on the two light-receiving surfaces Da and Db in response to the rotation of the second mirror M2 and the movable part 103, and the degree to which the focused spot SP1 falls on the two light-receiving surfaces Da and Db changes. Therefore, as with the above embodiment, the rotation position of the second mirror M2 can be detected based on the light-receiving signal output from the two-segment photodiode 504.

[0110] <Modification 2> FIG. 12 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to Modification 2. In FIG.

[0111] In the modified example 2, a mirror 512 is added to the configuration of the modified example 1. The mirror surface 512a of the mirror 512 is flat. As in the above embodiment, the light source 501 is disposed on the circuit board 301a and emits monitor light downward.

[0112] This configuration also achieves the same effects as those of Modified Example 1. Furthermore, in this configuration, the monitor light is reflected by the mirror 512 and guided to the lower surface 103a of the movable part 103, so that the projection part 500a can be made smaller in height than in the configuration of Modified Example 1, and the shape of the second optical deflector 17 (optical deflector) can be made more compact.

[0113] <Modification 3> FIG. 13 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to Modification 3. In FIG.

[0114] In Modification Example 3, a mirror 513 is added to the configuration of Modification Example 2. The mirror surface 513a of the mirror 513 is flat. As in the above embodiment, the two-segment photodiode 504 is disposed facing downward on the circuit board 301b. The relationship between the focused spot SP1 and the light-receiving surfaces Da and Db is the same as in FIGS. 9(a) to 9(c).

[0115] This configuration also achieves the same effects as those of Modifications 1 and 2. Furthermore, in this configuration, the reflected light of the monitor light reflected by the lower surface 103 a of the movable part 103 is returned by the mirror 513 and guided to the two-segment photodiode 504, so that the light receiving part 500 b can be made smaller in the height direction than in the configurations of Modifications 1 and 2, and the shape of the second optical deflector 17 (optical deflector) can be made more compact.

[0116] <Modification 4> FIG. 14 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to Modification 4. In FIG.

[0117] In the modified example 4, a lens 514 is added to the configuration of the modified example 2. The lens 514 focuses the monitor light emitted from the light source 501 onto the lower surface 103a of the movable part 103.

[0118] This configuration also achieves the same effects as those of Modifications 1 and 2. Furthermore, in this configuration, the monitor light emitted from the light source 501 is focused on the lower surface 103a of the movable part 103, so the area of ​​the lower surface 103a onto which the monitor light is irradiated can be significantly reduced. This increases the degree of freedom in designing the optical deflection element 100.

[0119] 14, reflected light of the monitor light is generated from the focal point of the monitor light set on the lower surface 103a. Therefore, by omitting the lens 511 and moving the two-segment photodiode 504 closer to this focal point, a relatively small focused spot SP1 can be directed to the light-receiving surfaces Da and Db of the two-segment photodiode 504. As a result, as in the above embodiment, a detection signal corresponding to the rotational position of the second mirror M2 can be accurately generated from the light-receiving signal from the two-segment photodiode 504. In this case, the lens 514 of the projection unit 500a is also used as an optical element on the light-receiving unit 500b side that focuses reflected light of the monitor light on the two light-receiving surfaces Da and Db.

[0120] 14, the lens 511 may be omitted, and the lens 514 of the projection unit 500a may be configured to focus the monitor light at the focal point F12 instead of the lower surface 103a. In this case, the monitor light is irradiated onto the lower surface 103a of the movable unit 103 in an off-focus state. Even with this configuration, a detection signal corresponding to the rotational position of the second mirror M2 can be accurately generated from the light reception signal from the two-segment photodiode 504. Also in this case, the lens 514 of the projection unit 500a is also used as an optical element on the light receiving unit 500b side, which focuses the reflected light of the monitor light onto the two light receiving surfaces Da and Db.

[0121] <Modification 5> FIG. 15 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to Modification 5. In FIG.

[0122] In the fifth modification, the configuration of the light receiving unit 500b is modified compared to the configuration of Fig. 7. That is, in the configuration of Fig. 15, the reflected light of the monitor light reflected by the lower surface 103a of the movable part 103 is collected by the lens 511 onto the light receiving surfaces Da and Db of the two-segment photodiode 504. The focal point F21 of the reflected light is positioned on the far side of the light receiving surfaces Da and Db in the traveling direction of the reflected light.

[0123] With this configuration, as in the above embodiment, the rotation state of the second mirror M2 can be accurately detected based on the light reception signal from the two-segment photodiode 504. Also with this configuration, as in the configuration of Figure 14, the lens 511 may be omitted and the reflected light of the monitor light may be directed directly to the light receiving surfaces Da and Db.

[0124] Modification 6 FIG. 16 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to Modification 6. In FIG.

[0125] In Modification 6, the configuration of the projection unit 500a is modified compared to the configuration in Fig. 7. That is, in the configuration in Fig. 16, the monitor light emitted from the light source 501 is focused by the lens 514 onto the lower surface 103a of the movable unit 103. With this configuration, as in the above embodiment, the rotation state of the second mirror M2 can be accurately detected based on the light reception signal from the two-segment photodiode 504.

[0126] Other Embodiments In the above embodiment, the projection unit 500a projects the monitor light onto the lower surface 103a of the movable unit 103, but the monitor light may be projected onto the upper surface of the second mirror M2.

[0127] FIG. 17 is a cross-sectional view showing the configuration of a second optical deflector 17 according to another embodiment.

[0128] 17, the second optical deflector 17 includes a projection unit 500a that projects the monitor light L11 onto the upper surface of the second mirror M2, and a light receiving unit 500b that receives the reflected light of the monitor light L11 reflected by the upper surface of the second mirror M2. As in the above embodiment, the projection unit 500a includes a light source 501 and a mirror 502, and the light receiving unit 500b includes a mirror 503 and a two-segment photodiode 504.

[0129] The configurations of the projection unit 500a and the light receiving unit 500b are the same as those of the above embodiment, except that the projection target of the monitor light L11 (the reflection target of the monitor light L11) is the upper surface of the second mirror M2. As in the above embodiment, the reflecting surfaces 502a and 503a of the mirrors 502 and 503 are shaped along the respective ellipsoids of revolution. The mirrors 502 and 503 focus the monitor light L11 emitted from the light source 501 near the center of the upper surface of the second mirror M2. The mirror 503 focuses the monitor light L11 reflected by the second mirror M2 at a position offset from the two light receiving surfaces of the two-segment photodiode 504 in a direction perpendicular to these light receiving surfaces.

[0130] The light source 501 and the two-segment photodiode 504 are mounted on the upper surface of the circuit board 300. A drive circuit for driving the light source 501 and the two-segment photodiode 504 is mounted on the circuit board 300. The mirrors 502 and 503 are mounted on the lower surface of a glass substrate 600 mounted on the support member 400. Light L10 for generating an image modulated by a video signal passes through the glass substrate 600 and is incident on the second mirror M2. A light-shielding means 601 is provided on the lower surface of the glass substrate 600 in an area other than the area through which the light L10 passes.

[0131] 17 , as in the above embodiment, the focused spot SP1 moves on the two light receiving surfaces Da, Db in the alignment direction in response to the rotation of the second mirror M2 (scanning mirror). Therefore, the balance of the extent to which the focused spot SP1 falls on the two light receiving surfaces Da, Db corresponds to the rotation position of the second mirror M2 (scanning mirror). Therefore, the two sensor units 504a, 504b constituting the two-segment photodiode 504 output light receiving signals with a balance of magnitudes corresponding to the rotation position of the second mirror M2 (scanning mirror). Therefore, from these two light receiving signals, a detection signal corresponding to the rotation position of the second mirror M2 (scanning mirror) can be generated using the above equation (1).

[0132] Furthermore, because the response characteristics of the two-segment photodiode 504 are high, even if the second mirror M2 (scanning mirror) is driven at high speed, light reception signals are output from the sensors 504a and 504b with high response. Therefore, even when the second mirror M2 (scanning mirror) is driven at high speed, a detection signal corresponding to the rotational position of the second mirror M2 (scanning mirror) can be accurately obtained.

[0133] Modification 7 In the other embodiment described above, the configurations of the projection unit 500a and the light receiving unit 500b are not limited to the above configurations, and various modifications are possible.

[0134] FIG. 18 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to the seventh modification.

[0135] In the seventh modification, the monitor light L11 emitted from the light source 501 is irradiated onto the upper surface of the second mirror M2 without being focused. The monitor light L11 reflected by the second mirror M2 is focused by the lens 511 onto the light-receiving surfaces Da and Db of the two-segment photodiode 504. The focus F21 of the reflected light is positioned on the far side of the light-receiving surfaces Da and Db in the direction of travel of the reflected light. The optical axis of the monitor light L11 traveling from the light source 501 to the two-segment photodiode 504 is included in a common plane parallel to the Y-Z plane. The two light-receiving surfaces Da and Db are aligned in the direction in which the focused spot SP1 moves due to the rotation of the movable unit 103. When the movable unit 103 is in the neutral position, the optical axis of the reflected light passes through the dividing line between the light-receiving surfaces Da and Db, perpendicular to the plane including the light-receiving surfaces Da and Db, as in the case of FIG. 9B.

[0136] 9A to 9C, with this configuration, the focused spot SP1 moves on the two light-receiving surfaces Da and Db in response to the rotation of the second mirror M2 and the movable part 103, and the extent to which the focused spot SP1 falls on the two light-receiving surfaces Da and Db changes. Therefore, as with the above embodiment, the rotation position of the second mirror M2 can be detected based on the light-receiving signal output from the two-segment photodiode 504.

[0137] Eighth Modification FIG. 19 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to an eighth modification.

[0138] In the modification example 8, the light source 501 is omitted compared to the modification example 7. Here, the monitor light L11 is emitted from the image generating unit 4 in FIG. 3 together with the light L10 for image generation.

[0139] 20, the following are added to the configuration of FIG. 3: a light source 11d for emitting monitor light L11; a collimator lens 12d and an aperture 13d for collimating and beam-shaping the monitor light L11 emitted from the light source 11d; and a dichroic mirror 14d for aligning the optical axis of the monitor light L11 with the optical axis of the light L10 from the light sources 11a to 11c. The light source 11d emits laser light in the infrared wavelength band. The dichroic mirror 14d reflects the monitor light L11 from the light source 11d and transmits the light L10 from the light sources 11a to 11c.

[0140] Returning to FIG. 19 , the projection unit 500a includes a dichroic mirror 515, a mirror 516, and a lens 514. The dichroic mirror 515 reflects the monitor light L11 and transmits the light L10 out of the light L10 and the monitor light L11 whose optical axes are aligned by the optical system of FIG. 20 . The light L0 transmitted through the dichroic mirror 515 is incident on the second mirror M2 near the center in the Y-axis direction. The monitor light L11 reflected by the dichroic mirror 515 is reflected by the mirror 516 and then collected by the lens 514 near the center in the Y-axis direction of the second mirror M2. The configuration of the light receiving unit 500b is the same as that of Modification 7 of FIG. 18 .

[0141] According to the configuration of the eighth modified example, the light source 501 and its driving circuit can be omitted from the second optical deflector 17. Therefore, the configuration of the second optical deflector 17 can be simplified.

[0142] In the configuration of Modification Example 8, the monitor light L11 is also scanned by the first optical deflector 15. However, the scanning direction is parallel to the dividing line between the light receiving surfaces Da and Db in FIGS. 9A to 9C. Therefore, even when the monitor light L11 is scanned by the first optical deflector 15, the focused spot SP1 moves on the two light receiving surfaces Da and Db in accordance with the rotation of the second mirror M2 and the movable part 103, and the degree to which the focused spot SP1 fits onto the two light receiving surfaces Da and Db changes. Therefore, as in the above embodiment, the rotation position of the second mirror M2 can be detected based on the light receiving signal output from the two-segment photodiode 504. This also applies to Modification Example 9 described below.

[0143] <Modification 9> FIG. 21 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to Modification 9. In FIG.

[0144] In Modification Example 9, compared to Modification Example 8, the projection unit 500a is omitted, and a dichroic mirror 515 is added to the light receiving unit 500b. The projection unit that projects the monitor light L11 onto the upper surface of the second mirror M2 is composed of the light source 11d, collimator lens 12d, aperture 13d, and dichroic mirror 14d shown in FIG. 20. The light L10 and monitor light L11, whose optical axes are aligned by the optical system of FIG. 20, are incident on the vicinity of the center of the second mirror M2 and are reflected by the second mirror M2. The dichroic mirror 515 reflects the monitor light L11 out of the light L10 and monitor light L11 reflected by the second mirror M2, and transmits the light L10.

[0145] The monitor light L11 reflected by the dichroic mirror 515 is collected by the lens 511 onto the light receiving surface of the two-segment photodiode 504. The state in which the monitor light L11 is collected onto the two-segment photodiode 504 is the same as in the seventh modification.

[0146] According to the configuration of Modification Example 9, the projection unit 500a can be further omitted compared to the configuration of Modification Example 8. Therefore, the configuration of the second optical deflector 17 can be further simplified.

[0147] <Modification 10> FIG. 22 is a cross-sectional view showing the configuration of a projection section 500a and a light receiving section 500b according to Modification 10. In FIG.

[0148] In Modification Example 10, a half-wave plate 517 and polarizing beam splitters 518a and 518b are added to the configuration of Modification Example 18 in FIG. 18. The polarizing beam splitters 518a and 518b are arranged in the optical path of the image-generating light L10 and combine and split the monitor light L11 emitted from the light source 501 into light L10. The half-wave plate 517 adjusts the polarization direction of the monitor light L11 (laser light) emitted from the light source 501 so that it becomes S-polarized light with respect to the polarizing beam splitter 518a. The polarization direction of the light L10 becomes P-polarized light with respect to the polarizing beam splitter 518a. The polarizing beam splitter 518a aligns the optical axis of the reflected monitor light L11 with the optical axis of the transmitted light L10.

[0149] Light L10 and monitor light L11, whose optical axes are aligned by the polarizing beam splitter 518a, are incident on the second mirror M2 near the center in the Y-axis direction and are reflected by the second mirror M2. Of light L10 and monitor light L11 reflected by the second mirror M2, light L10 passes through the polarizing beam splitter 518b, and monitor light L11 is reflected by the polarizing beam splitter 518b. Monitor light L11 is then focused by the lens 511 onto the light-receiving surface of the two-segment photodiode 504. The state of focus of monitor light L11 on the two-segment photodiode 504 is the same as in the seventh modification.

[0150] <Other Modifications> In the above embodiment, the monitor light emitted from the light source 501 is focused on the lower surface 103a of the movable part 103. However, the monitor light does not necessarily have to be focused precisely on the lower surface 103a, and may be focused near the lower surface 103a. For example, the focus of the monitor light may be set at a position slightly offset from the lower surface 103a in a direction perpendicular to the lower surface 103a, and the monitor light may be irradiated onto the lower surface 103a of the movable part 103 in an off-focus state. This also applies to Modifications 4 to 6. Similarly, in the other embodiments and Modifications 7 to 10, the monitor light does not necessarily have to be focused precisely on the upper surface of the second mirror M2, and may be focused near the upper surface of the second mirror M2.

[0151] Furthermore, in the above embodiment and modifications 1 to 6, the lower surface 103a of the movable part 103 is a uniform plane, but as long as the monitor light is properly reflected and received by the two-segment photodiode 504 when the movable part 103 rotates, the lower surface 103a of the movable part 103 does not have to be a uniform plane. For example, ribs may be provided near the outer periphery of the lower surface 103a of the movable part 103. When ribs are provided on the lower surface 103a, as in the above embodiment and modifications 4 to 6, it is preferable to focus the monitor light on the lower surface 103a of the movable part 103 and limit the area of ​​the lower surface 103a onto which the monitor light is irradiated as small as possible. This prevents the monitor light from being blocked by the ribs, thereby increasing the degree of freedom in designing the optical deflector element 100.

[0152] In the above embodiment, as shown in Figures 9(a) to 9(c), the width of the light receiving surfaces Da, Db in the X-axis direction is wider than the size of the focused spot SP1 in the X-axis direction. However, as long as a detection signal that changes in one direction according to the rotation angle is obtained within the rotation detection range of Figure 10, the width of the light receiving surfaces Da, Db in the X-axis direction may be smaller than the size of the focused spot SP1 in the X-axis direction. The shapes of the light receiving surfaces Da, Db are not limited to those shown in Figures 9(a) to 9(c). This also applies to the other embodiments described above.

[0153] Furthermore, in the above embodiment, the configuration of the present invention is used to detect the scanning position of light in the vertical direction, but the configuration of the present invention may also be used to detect the scanning position of light in the horizontal direction. In this case, the configuration of the projection unit 500a and the light receiving unit 500b is applied to the first optical deflector 15. This also applies to the other embodiments described above.

[0154] Furthermore, in the above embodiment, an example was shown in which the present invention was applied to the image generating device 3 mounted on the AR glasses 1, but the image generating device to which the present invention is applied is not limited to this. The present invention can be used in various devices as long as it detects the rotational position of a mirror for optical scanning. The configurations of the projection unit 500a and the light receiving unit 500b according to the present invention are not limited to the configurations shown in the above embodiment, modified examples 1 to 6, other embodiments, and modified examples 7 to 10, and other modifications are possible. The calculation formula for calculating the detection signal is also not limited to the above formula (1).

[0155] The embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical idea defined in the claims.

[0156] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0157] (Technology 1) An optical deflector comprising: a movable part that rotates about a rotation axis; a scanning mirror that is arranged on the upper surface of the movable part and scans light; a projection part that projects monitor light onto the lower surface of the movable part or the upper surface of the scanning mirror; and a light receiving part that receives reflected light of the monitor light reflected on the lower surface or the upper surface, wherein the light receiving part includes: a two-segment photodiode having two light receiving surfaces that are aligned in a direction in which the reflected light moves due to rotation of the movable part; and an optical element that focuses the reflected light on the two light receiving surfaces, and the sizes of the light receiving spots and the two light receiving surfaces are set so that, within a rotation detection range for detecting rotation of the movable part, a focused spot of the reflected light straddles both of the two light receiving surfaces and does not extend beyond either of the light receiving surfaces at least in the direction in which the reflected light moves.

[0158] According to this technology, the focused light spot moves on the two light receiving surfaces in the alignment direction in response to the rotation of the scanning mirror. Therefore, the balance of the focused light spot on the two light receiving surfaces corresponds to the rotation position of the scanning mirror. As a result, the two sensor units constituting the two-segment photodiode output light receiving signals with a balance of magnitude corresponding to the rotation position of the scanning mirror. Therefore, a detection signal corresponding to the rotation position of the scanning mirror can be generated from these two light receiving signals. Furthermore, because the photodiode has high response characteristics, each sensor unit outputs a light receiving signal with high response even when the scanning mirror is driven at high speed. Therefore, even when the scanning mirror is driven at high speed, a detection signal corresponding to the rotation position of the mirror can be accurately obtained.

[0159] (Technology 2) The optical deflector according to Technology 1, characterized in that the optical element is a lens.

[0160] According to this technique, the reflected light of the monitor light can be collected on the light receiving surface of the two-segment photodiode with a simple configuration.

[0161] (Technology 3) In the optical deflector according to Technology 1, the light receiving section further includes a mirror that reflects the reflected light and directs it toward the two-segment photodiode.

[0162] According to this technique, the reflected monitor light is reflected by the mirror and guided to the two-segment photodiode, so that the light receiving section can be made smaller in height, and the shape of the optical deflector can be made compact.

[0163] (Technology 4) In the optical deflector described in Technology 3, the reflective surface of the mirror has a concave shape that focuses the reflected light to the focused spot, and the mirror is also used as the optical element.

[0164] According to this technique, the number of components in the light receiving section can be reduced, thereby simplifying the configuration of the optical deflector.

[0165] (Technology 5) In the optical deflector described in Technology 4, the projection unit includes another optical element that focuses the monitor light near the bottom surface of the movable unit or near the top surface of the scanning mirror, the reflecting surface of the mirror has a shape that follows an ellipsoid of revolution formed by rotating an ellipse that includes the focus of the monitor light on its major axis about the major axis, and the focus of the reflected light included on the major axis is positioned at a position that is deviated from the two light receiving surfaces in a direction perpendicular to these light receiving surfaces.

[0166] According to this technique, the reflected light of the monitor light reflected by the lower surface of the movable part can be properly focused onto the light receiving surface of the two-segment photodiode by the reflecting surface of the mirror.

[0167] (Technology 6) In the optical deflector described in any one of Technologies 1 to 5, the projection unit includes a light source that emits the monitor light, and another optical element that focuses the monitor light emitted from the light source near the bottom surface of the movable unit or near the top surface of the scanning mirror.

[0168] According to this technique, the area of ​​the lower surface of the movable part onto which the monitor light is irradiated can be significantly reduced, and the degree of freedom in designing the optical deflector can be increased.

[0169] (Technology 7) The optical deflector according to Technology 6, wherein the optical element of the projection unit is a lens.

[0170] According to this technique, the monitor light can be focused near the bottom surface of the movable part with a simple configuration.

[0171] (Technology 8) In the optical deflector described in Technology 6, the projection unit further includes a mirror that reflects the monitor light emitted from the light source and directs the light toward a lower surface of the movable unit or an upper surface of the scanning mirror.

[0172] According to this technology, the monitor light emitted from the light source is reflected by the mirror of the projection unit and directed to the underside of the movable unit, which allows the projection unit to be made smaller in height and the shape of the optical deflector to be made compact.

[0173] (Technology 9) In the optical deflector described in Technology 8, the reflective surface of the mirror has a concave shape that focuses the monitor light near the bottom surface of the movable part or near the top surface of the scanning mirror, and the mirror is also used as the other optical element.

[0174] According to this technique, the number of parts in the projection section can be reduced, and therefore the configuration of the optical deflector can be simplified.

[0175] (Technology 10) In the optical deflector described in Technology 9, the reflecting surface of the mirror has a shape along an ellipsoid of revolution formed by rotating an ellipse, the ellipse including the light emitting point of the light source and the focus of the monitor light on its major axis, about the major axis.

[0176] According to this technique, the monitor light emitted from the light source can be properly focused near the bottom surface of the movable part.

[0177] (Technology 11) In the optical deflector described in Technology 1, the projection unit projects monitor light onto a lower surface of the movable unit, and the light receiving unit receives reflected light of the monitor light reflected by the lower surface.

[0178] (Technology 12) An image generating device comprising: the optical deflector according to any one of techniques 1 to 11; and a control unit that controls the optical deflector based on an output from the two-segment photodiode.

[0179] According to this technology, since the image generating device includes the optical deflector described above, it is possible to accurately obtain a detection signal even when the scanning mirror is driven at high speed, and therefore the scanning position of the light can be appropriately controlled by this detection signal.

[0180] 3 Image generating device 11d Light source 17 Second optical deflector 41 Control unit 103 Movable unit 103a Lower surface 500a Projection unit 500b Light receiving unit 501 Light source 502 Mirror (another optical element) 502a Reflection surface 503 Mirror (optical element) 503a Reflection surface 504 Two-segment photodiode 504a, 504b Sensor unit 511 Lens (optical element) 512, 513 Mirror 514 Lens (another optical element) M2 Second mirror (scanning mirror) Da, Db Light receiving surface L1, L2 Major axis S1, S2 Ellipse F11 Light emitting point F12, F13 Focus B1 Reflected light SP1 Condensed spot

Claims

1. An optical deflector comprising: a movable part that rotates about a rotation axis; a scanning mirror that is arranged on the upper surface of the movable part and scans light; a projection part that projects monitor light onto the lower surface of the movable part or the upper surface of the scanning mirror; and a light receiving part that receives reflected light of the monitor light reflected on the lower surface or the upper surface, wherein the light receiving part includes a two-segment photodiode having two light receiving surfaces that are aligned in the direction in which the reflected light moves as the movable part rotates, and an optical element that focuses the reflected light on the two light receiving surfaces, and the sizes of the focused spot and the two light receiving surfaces are set so that, within a rotation detection range for detecting the rotation of the movable part, a focused spot of the reflected light straddles both of the two light receiving surfaces and does not extend beyond either of the light receiving surfaces, at least in the direction in which the reflected light moves.

2. The optical deflector according to claim 1, wherein the optical element is a lens.

3. An optical deflector according to claim 1, wherein the light receiving section further comprises a mirror which reflects the reflected light and directs it towards the two-segment photodiode.

4. An optical deflector according to claim 3, wherein the reflecting surface of the mirror has a concave shape for focusing the reflected light onto the focusing spot, and the mirror is also used as the optical element.

5. An optical deflector as described in claim 4, wherein the projection section includes another optical element that focuses the monitor light near the bottom surface of the movable section or near the top surface of the scanning mirror, the reflecting surface of the mirror has a shape along an ellipsoid of revolution formed by rotating an ellipse containing the focus of the monitor light on its major axis about the major axis, and the focus of the reflected light contained on the major axis is positioned at a position offset from the two light receiving surfaces in a direction perpendicular to these light receiving surfaces.

6. An optical deflector as described in claim 1, characterized in that the projection unit includes a light source that emits the monitor light, and another optical element that focuses the monitor light emitted from the light source near the bottom surface of the movable unit or near the top surface of the scanning mirror.

7. An optical deflector according to claim 6, wherein the optical element of the projection section is a lens.

8. An optical deflector according to claim 6, wherein the projection section further comprises a mirror that reflects the monitor light emitted from the light source and directs it toward the lower surface of the movable section or the upper surface of the scanning mirror.

9. An optical deflector as claimed in claim 8, characterized in that the reflecting surface of the mirror has a concave shape for focusing the monitor light near the lower surface of the movable part or near the upper surface of the scanning mirror, and the mirror is commonly used as the other optical element.

10. An optical deflector as claimed in claim 9, characterized in that the reflecting surface of the mirror has a shape conforming to an ellipsoid of revolution formed by rotating an ellipse, the major axis of which includes the light emitting point of the light source and the focus of the monitor light, about the major axis.

11. An optical deflector according to claim 1, characterized in that: the projection section projects monitor light onto the lower surface of the movable section; and the light receiving section receives reflected light of the monitor light reflected by the lower surface.

12. An image generating device comprising: an optical deflector according to any one of claims 1 to 11; and a control unit that controls the optical deflector based on an output from the two-segment photodiode.

Images