Light deflection device and image projection device

Abstract

The present application provides a light deflection device and an image projection device, which do not include reflected light from a light-transmitting plate in a projected image. A light deflection device according to one aspect of the present application includes a light deflection portion (12) that deflects light incident on a reflecting surface (121) by oscillating the reflecting surface (121) about an oscillation axis, and a light-transmitting plate (3) that transmits the light deflected by the light deflection portion (12), the light-transmitting plate (3) having an inclination angle (θ) with respect to a reference surface (111) that is twice or more the maximum oscillation angle (α) of the reflecting surface (121) with respect to the reference surface (111).

Description

Technical Field

[0001] This invention relates to a light deflection device and an image projection device. Background Technology

[0002] Previously, it was known to use a light deflection device that deflects the light emitted by the light-emitting part on a reflective surface and then projects an image onto the surface being scanned.

[0003] In addition, a structure is disclosed in which the maximum swing angle of the reflecting surface relative to the reference surface is smaller than the tilt angle of the light-transmitting plate relative to the reference surface in order to prevent the generation of abnormal images on the scanned surface (for example, see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6627994 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, in the structure of Patent Document 1, reflected light from the light-transmitting plate is sometimes included in the projected image, which reduces the image quality.

[0009] The purpose of this invention is to ensure that the projected image does not contain reflected light from the light-transmitting plate.

[0010] Solution for solving the problem

[0011] One aspect of the light deflection device of the present invention includes: a light deflection section 12, which deflects light incident on the reflective surface 121 by oscillating the reflective surface 121 about an oscillation axis; and a light-transmitting plate 3, which transmits the light deflected by the light deflection section 12, wherein the tilt angle θ of the light-transmitting plate 3 relative to the reference surface 111 is more than twice the maximum oscillation angle α of the reflective surface 121 relative to the reference surface 111.

[0012] Furthermore, the above figure labels are for ease of understanding and are merely an example, not a limitation on the way they are illustrated.

[0013] Invention Effects

[0014] According to the present invention, the projected image can be made free of reflected light from the light-transmitting plate. Attached Figure Description

[0015] Figure 1 This is a perspective view showing an example of the overall structure of the image projection device in an embodiment.

[0016] Figure 2This is a diagram illustrating a structural example of the optical deflection device in an embodiment. Figure 2 (a) is a top view. Figure 2 (b) is the left-side view. Figure 2 (c) is the front view. Figure 2 (d) is the right-side view.

[0017] Figure 3 This is a perspective view showing a structural example of the optical deflection unit in an embodiment.

[0018] Figure 4 This is a diagram showing an example of the structure of the optical deflection section in an embodiment.

[0019] Figure 5 This is a diagram illustrating the drive signals. Figure 5 (a) is a diagram of an example of a horizontal drive signal. Figure 5 (b) is a diagram of an example of a vertical drive signal.

[0020] Figure 6 This is a diagram illustrating an example of laser incident and emission from the optical deflection device in an embodiment.

[0021] Figure 7 This is a cross-sectional view showing the effect of the tilt of the light-transmitting plate in the embodiment.

[0022] Figure 8 This is a cross-sectional view showing the effect of the tilt of the light-transmitting plate in the comparative example.

[0023] Figure 9 This is a perspective view showing another first example of the optical deflection section in the embodiment.

[0024] Figure 10 This is a perspective view showing another second example of the optical deflection section in the embodiment.

[0025] Figure 11 This is a diagram showing another example of the tilt of the light-transmitting plate in the embodiment.

[0026] Figure 12 This is a diagram of the first example of the combination of the height of the incident laser and the tilt of the light-transmitting plate. Figure 12 (a) is a 3D diagram. Figure 12 (b) is along Figure 12 (a) is a cross-sectional view of the TT cut line.

[0027] Figure 13 This is a second example of the combination of the height of the incident laser and the tilt of the light-transmitting plate. Figure 13 (a) is a 3D diagram. Figure 13 (b) is along Figure 13 (a) is a cross-sectional view of the UU cut line.

[0028] Figure 14 This is the third example of the combination of the height of the incident laser and the tilt of the light-transmitting plate. Figure 14 (a) is a 3D diagram. Figure 14 (b) is along Figure 14 (a) is a cross-sectional view of the VV cut line.

[0029] In the picture:

[0030] 1—Optical deflection unit; 11—Packaging component; 111—Mounting surface (an example of a reference surface); 111A, 111B, 111C—Plane; 12—Optical deflection section; 121—Reflective surface; 122—Modible frame; 123—Support section; 124a, 124b—Torsion beams; 125a, 125b—Connecting beams; 126a, 126b—First drive beams; 127a, 127b—Drive source; 128—Slit; 130a, 130b—Second drive beams; 131a, 131b—Modible frame connection; 132a, 132b—Fixed frame connection; 133—Fixed frame; 134a, 134b—Drive source; 135a, 135b—Terminal group; 136a 136b—Vertical piezoelectric sensor; 137a, 137b—Horizontal piezoelectric sensors; 2—Cover; 3—Light-transmitting plate; 31—First surface; 32—Second surface; 35—Tilting axis; 10—Light-emitting part; 20—Light deflection device; 30—Control part; 200—Scanned surface; 201—Image; A—First swing axis (an example of a swing axis, an example of a first axis); B—Second swing axis (an example of a second axis); L1—Incident laser; L2—Outgoing laser; R3—Triple reflection laser; R4—Quadruple reflection laser; h1, h2—Height; α—Maximum swing angle; α1—First maximum swing angle; α2—Second maximum swing angle; β1, β2—Selection angle; θ1, θ2—Tilting angle. Detailed Implementation

[0031] Hereinafter, the methods for carrying out the invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals are sometimes used to refer to the same structural parts, and repeated descriptions are omitted.

[0032] Furthermore, the embodiments shown below illustrate a light deflection device and an image projection device for embodying the technical concept of the present invention, and do not limit the present invention to the embodiments shown below. Unless specifically stated otherwise, the dimensions, materials, shapes, and relative arrangements of the structural components described below are not intended to limit the scope of the present invention, but are intended to be illustrative. Additionally, for clarity, there may be instances where the size and positional relationships of the components shown in the accompanying drawings are exaggerated.

[0033] The light deflection device of the embodiment includes: a light deflection section that deflects light incident on the reflective surface by oscillating the reflective surface about an oscillation axis; and a light-transmitting plate that allows light deflected by the light deflection section to pass through.

[0034] Such light deflection devices are used, for example, in image projection devices that project images onto a surface to be scanned, to deflect light and thus perform scanning on the surface. Examples of image projection devices include projectors, vehicle welcome projectors, head-up displays, head-mounted displays, vehicle headlights, object recognition devices, rangefinders, and fundus examination devices.

[0035] In addition, a vehicle welcome projector refers to a projector installed on a vehicle door or similar structure that projects a desired image, including signs, when the door is opened. Furthermore, an object recognition device refers to a device that detects and identifies the presence, shape, or distance to an object based on reflected or scattered light from the projected light.

[0036] When the aforementioned light deflection device is used in image projection devices or the like, sometimes a portion of the light deflected by the light deflection unit is reflected back to the light deflection unit instead of passing through the light-transmitting plate, and is deflected again on the reflecting surface. Additionally, sometimes a portion of the light that is deflected again is reflected back to the light deflection unit instead of passing through the light-transmitting plate, and is deflected again on the reflecting surface.

[0037] Because the projected image contains reflected light from the light-transmitting plate, multiple images sometimes overlap to produce visually recognizable multiple images, moiré patterns, etc.

[0038] Furthermore, if the light-emitting part, which allows light to be incident on the reflective surface, is positioned on the opposite side of the reflective surface, sandwiching a light-transmitting plate, the light from the light-emitting part, after passing through the light-transmitting plate, is incident on the reflective surface. In this case, the light reflected by the light-transmitting plate from the incident light is sometimes included in the projected image. Because the projected image contains reflected light from the incident light, point-like stray light may sometimes occur.

[0039] The light-transmitting plate includes a first surface and a second surface opposite to the first surface. Therefore, due to the reflected light from the first and second surfaces, multiple images and point-like stray light may be generated.

[0040] In contrast, in this embodiment, by tilting the light-transmitting plate relative to the reference surface at an angle greater than twice the maximum tilt angle of the reflecting surface relative to the reference surface, the projected image is free of secondary reflected light from the light-transmitting plate. Furthermore, this ensures a higher quality of the projected image.

[0041] Here, the reference plane refers to the plane that serves as the reference for the tilt of the reflecting surface caused by the oscillation, and specifically, the plane that serves as the reference for the tilt of the light-transmitting plate. The oscillation angle refers to the angle of tilt of the reflecting surface relative to the reference plane due to the oscillation. The maximum oscillation angle refers to the largest oscillation angle among all oscillation angles.

[0042] Furthermore, in the terminology used in the implementation method, "light deflection" refers to changing the direction of light travel. In the implementation method, the reflective surface deflects light by reflecting it.

[0043] Hereinafter, an image projection device having an embodiment of the light deflection device will be used as an example to describe the embodiment.

[0044] In the figures shown below, the X, Y, and Z axes are sometimes used to represent directions. However, the X direction along the X-axis represents the direction in which the light deflection unit of the light deflection device in the embodiment deflects light to perform scanning. The Y direction along the Y-axis is the direction in which the light deflection unit of the light deflection device in the embodiment deflects light to perform scanning, and it represents a direction that is approximately orthogonal to the X-axis. The Z direction along the Z-axis represents a direction that is approximately orthogonal to both the X-axis and the Y-axis.

[0045] Furthermore, the direction in which the arrow points in the X direction is marked as the +X direction, and the opposite direction of the +X direction is marked as the -X direction; the direction in which the arrow points in the Y direction is marked as the +Y direction, and the opposite direction of the +Y direction is marked as the -Y direction; the direction in which the arrow points in the Z direction is marked as the +Z direction, and the opposite direction of the +Z direction is marked as the -Z direction. However, these markings do not restrict the orientation of the light deflection device and the image projection device; the light deflection device and the image projection device can be configured in any orientation.

[0046] <Structural Example of Image Projection Device 100>

[0047] First, refer to Figure 1 and Figure 2 The overall structure of the image projection device 100 of the embodiment and the structure of the light deflection device 20 of the image projection device 100 will be described.

[0048] Figure 1 This is a perspective view illustrating an example of the overall structure of the image projection device 100. Additionally, Figure 2 This is a diagram illustrating an example of the structure of the optical deflection device 20. Figure 2 (a) is a top view. Figure 2 (b) is the left-side view. Figure 2 (c) is the front view. Figure 2 (d) is the right-side view.

[0049] like Figure 1 As shown, the image projection device 100 includes a light-emitting unit 10, a light deflection device 20, and a control unit 30. These are disposed within the frame of the image projection device 100.

[0050] Under the control of the control unit 30, the image projection device 100 uses the light deflection device 20 to scan the red, green, blue and IR (infrared) lasers emitted by the light-emitting unit 10 in the X and Y directions respectively, and projects a full-color image 201 onto the scanned surface 200.

[0051] In this embodiment, as an example, the Y direction corresponds to the direction of gravity, and the X direction corresponds to the horizontal direction that is approximately orthogonal to the direction of gravity. The light deflection device 20 can deflect the red, green, blue, and IR lasers emitted by the light-emitting unit 10 respectively, and scan the surface 200 along the X and Y directions.

[0052] However, the image 201 projected by the image projection device 100 is not limited to a full-color image; it can also be a monochrome image, etc. In the case of projecting a monochrome image, the image projection device 100 uses a monochrome laser to scan the surface 200 being scanned.

[0053] When the image projection device 100 is a projector, the scanned surface 200 corresponds to a screen or the like. When the image projection device 100 is a head-up display, the scanned surface 200 corresponds to a car's windshield or the like.

[0054] Furthermore, when the image projection device 100 is a head-mounted display or a fundus examination device, the scanned surface 200 corresponds to holographic optical elements, the retina of the eye, etc. When the image projection device 100 is a vehicle headlight, an object recognition device, or a rangefinder, it corresponds to a virtual plane in space.

[0055] The light-emitting unit 10 includes an LD (Laser Diode) that emits red laser light, an LD that emits green laser light, an LD that emits blue laser light, and an LD that emits IR laser light. The light-emitting unit 10 directs the red, green, blue, and IR laser light emitted by the LDs of each color onto the light deflection device 20. Each color of laser light is an example of the light emitted by the light-emitting unit.

[0056] like Figure 1 and Figure 2 As shown, the light deflection device 20 includes a light deflection unit 1, a cover 2, and a light-transmitting plate 3. The cover 2 is provided on the +Z direction side of the light deflection unit 1, and the light-transmitting plate 3 is provided on the +Z direction side of the cover 2.

[0057] The optical deflection unit 1 includes an optical deflection part and a package 11, and has the function of deflecting the laser emitted by the light-emitting part 10.

[0058] The package 11 is a box-shaped component that holds the light deflection part inside. The package 11 is constructed from a metal material such as alumina ceramic, aluminum, aluminum alloy, or stainless steel, or a plastic material. In addition, the package 11 includes a circuit board made of FRP (Fiber Reinforced Plastics) or FPC (Flexible Printed Circuits).

[0059] In addition, using Figure 3 and Figure 4 The structure and function of the optical deflection section will be explained separately.

[0060] The cover 2 is a cylindrical component with a quadrilateral cross-section, made of materials such as alumina ceramic, aluminum, aluminum alloy, stainless steel, or plastic. The cover 2 is fixed in place using an adhesive or similar means, with its end on the -Z direction side in contact with the mounting surface 111 on the +Z direction side of the encapsulation member 11. This mounting surface 111 corresponds to an example of a reference surface.

[0061] The end of the cover 2 on the +Z direction side is formed by a surface that is inclined relative to the mounting surface 111. With the inclined surface of the cover 2 in contact with the light-transmitting plate 3, the light-transmitting plate 3 is fixed and held by adhesive or low-melting-point glass welding.

[0062] The light-transmitting plate 3 is a plate-shaped component that allows the laser emitted by the light-emitting unit 10 to pass through, and also allows the laser deflected by the light deflecting unit contained in the light deflecting unit 1 to pass through. The light-transmitting plate 3 also functions as an entrance window that allows the laser to enter from the outside of the light deflecting device 20 into the inside, and as an exit window that allows the laser to exit from the inside of the light deflecting device 20 to the outside.

[0063] Such a light-transmitting plate 3 is constructed from materials such as optical glass, heat-resistant glass, hard glass, optical plastic, and hard plastic, which are transparent to the wavelengths of lasers of various colors emitted by the light-emitting part 10. Anti-reflective films for preventing reflection of incident lasers are respectively applied to the first surface and the second surface opposite to the first surface of the light-transmitting plate 3.

[0064] The end of the cover 2 in the +Z direction that the light-transmitting plate 3 contacts is inclined relative to the mounting surface 111, so the light-transmitting plate 3 is also held by the cover 2 in an inclined state relative to the mounting surface 111. By using the cover 2 and the light-transmitting plate 3 to seal, the adhesion of dust or other particles, moisture, oxygen and other contaminants to the light deflection part of the light deflection unit 1 are prevented.

[0065] The control unit 30 controls the emission of each color LD in the light-emitting unit 10 by applying driving signals such as driving voltage to the light-emitting unit 10. In addition, the control unit 30 controls the scanning of the laser performed by the light deflection device 20 by applying driving signals such as driving voltage to the light deflection device 20.

[0066] In addition to being implemented through circuits, the functions of the control unit 30 can also be partially or fully implemented through software (CPU; Central Processing Unit).

[0067] <Structure Example of Optical Deflection Unit 1>

[0068] Next, refer to Figure 3 and Figure 4 The structure of optical deflection unit 1 will be explained. First, Figure 3 This is a three-dimensional diagram illustrating an example of the structure of the optical deflection unit 1. Figure 3 The display shows the state after the cover 2 and the light-transmitting plate 3 in the light deflection device 20 have been removed.

[0069] like Figure 3 As shown, the optical deflection unit 1 includes a package 11 and an optical deflection section 12. The optical deflection section 12 is held in the package 11 such that its reflective surface 121 is disposed near the center of the package 11. Furthermore, the optical deflection unit 1 may include circuitry within the package 11, or it may include a substrate, control circuitry, etc., on the underside of the package 11.

[0070] The light deflection unit 12 deflects the laser light incident on the reflecting surface 121 by oscillating the reflecting surface 121 around a first oscillation axis A and a second oscillation axis B, respectively. The light deflection unit 12 is, for example, a MEMS (Micro-Electro-Mechanical Systems) mirror that uses a piezoelectric element to oscillate the reflecting surface 121. Here, the first oscillation axis A is an example of an oscillation axis, and another example is a first axis. The second oscillation axis B is an example of a second axis.

[0071] then, Figure 4 This is a diagram illustrating an example of the structure of the light deflection section 12. (See diagram for example.) Figure 4 As shown, the light deflection section 12 has a reflective surface 121, a movable frame 122 supporting the reflective surface 121 from the outside, and a pair of second drive beams 130a and 130b supporting the movable frame 122 from both sides.

[0072] The movable frame connecting part 131a connects the movable frame 122 and the second drive beam 130a. The fixed frame connecting part 132a connects the fixed frame 133 and the second drive beam 130a.

[0073] The movable frame connecting part 131b connects the movable frame 122 and the second drive beam 130b. The fixed frame connecting part 132b connects the fixed frame 133 and the second drive beam 130b.

[0074] The light deflection unit 12 has a reflective surface 121, a movable frame 122, a support 123, torsion beams 124a and 124b, connecting beams 125a and 125b, a first drive beam 126a and 126b, a second drive beam 130a and 130b, and a fixed frame 133.

[0075] The first drive beam 126a has a drive source 127a, and the first drive beam 126b has a drive source 127b. The second drive beam 130a has a drive source 134a, and the second drive beam 130b has a drive source 134b.

[0076] The first drive beams 126a and 126b function as actuators to deflect the laser by oscillating the reflective surface 121 about the first oscillation axis A. Additionally, the second drive beams 130a and 130b function as actuators to deflect the laser by oscillating the reflective surface 121 about the second oscillation axis B.

[0077] A slit 128 is formed in the support portion 123 in a manner that runs along the circumference of the reflective surface 121. Through the slit 128, the stress concentration generated by the torsional action of the torsion beams 24a and 24b can be dispersed to prevent damage to the first reflective surface 22, and the torsion of the torsion beams 124a and 124b can be transmitted to the reflective surface 121.

[0078] In the light deflection section 12, a reflective surface 121 is supported on the upper surface of the support section 123. The support section 123 is connected to the ends of the torsion beams 124a and 124b located on both sides. The torsion beams 124a and 124b form a first swing axis A and extend along the direction of the first swing axis A, supporting the support section 123 from both sides in the direction of the first swing axis A.

[0079] The torsion beams 124a and 124b twist, causing the reflecting surface 121 supported on the support 123 to swing, thereby deflecting the reflected light of the laser incident on the reflecting surface 121 for scanning. The torsion beams 124a and 124b are respectively connected to the connecting beams 125a and 125b, and to the first drive beams 126a and 126b.

[0080] The first drive beams 126a and 126b, the connecting beams 125a and 125b, the torsion beams 124a and 124b, the support portion 123, and the reflective surface 121 are supported from the outside by the movable frame 122.

[0081] One side of each of the first drive beams 126a and 126b is supported by the movable frame 122. The other side of the first drive beam 126a extends inward and connects to the connecting beams 125a and 125b. Similarly, the other side of the first drive beam 126b extends inward and connects to the connecting beams 125a and 125b.

[0082] The first drive beams 126a and 126b are arranged in pairs, with the reflective surface 121 and the support portion 123 sandwiched in a direction orthogonal to the torsion beams 124a and 124b. A drive source 127a is formed on the upper surface of the first drive beam 126a, and a drive source 127b is formed on the upper surface of the first drive beam 126b.

[0083] The drive sources 127a and 127b include an upper electrode formed on a thin film (hereinafter also referred to as "piezoelectric film") of a piezoelectric element formed on the upper surface of the first drive beams 126a and 126b, and a lower electrode formed on the lower surface of the piezoelectric film. The drive sources 127a and 127b are scaled down according to the polarity of the drive voltage applied to the upper electrode and the lower electrode.

[0084] Therefore, if driving voltages of different phases are applied alternately to the first driving beam 126a and the first driving beam 126b, the first driving beam 126a and the first driving beam 126b will vibrate alternately on opposite sides of the left and right sides of the reflecting surface 121.

[0085] Therefore, the torsion beams 124a and 124b can be used as the first swing axis A, causing the reflecting surface 121 to swing around the first swing axis A. For example, in the swing drive around the first swing axis A using the first drive beams 126a and 126b, resonant vibration can be used to make the reflecting surface 121 swing at high speed.

[0086] Here, Figure 5 This is a diagram illustrating the drive signals. Figure 5 (a) is a diagram representing an example of a horizontal drive signal. Figure 5 (b) is a diagram representing an example of a vertical drive signal.

[0087] like Figure 5 As shown, both horizontal drive signals AHp and AHn are sinusoidal waves with the same period and amplitude, but AHn is phase-shifted by half a period relative to AHp. That is, the horizontal drive signals AHp and AHn have their potentials reversed relative to their intermediate potentials. The first reflecting surface 22 is driven by the potential difference between the horizontal drive signals AHp and AHn, and its swing angle corresponds to the amplitudes of the horizontal drive signals AHp and AHn.

[0088] return Figure 4 One end of the second drive beams 130a and 130b is connected to the outside of the movable frame 122 via movable frame connecting portions 131a and 131b. The second drive beams 130a and 130b are arranged in pairs to clamp the movable frame 122 from both sides. Moreover, the second drive beams 130a and 130b support the movable frame 122 from both sides and swing about the second swing axis B.

[0089] The other end of the second drive beam 130a is connected to the inner side of the fixed frame 133 via the fixed frame connecting part 132a. In addition, the other end of the second drive beam 130b is connected to the inner side of the fixed frame 133 via the fixed frame connecting part 132b.

[0090] like Figure 4 As shown, the second drive beam 130a has a plurality of rectangular vertical beams extending in the direction along the first swing axis A, and a folded portion connecting the ends of adjacent vertical beams to each other, and has an overall sawtooth shape.

[0091] For example, counting from the first drive beam 126a side, the ends of the first and second vertical beams are connected by a fold-back section. Furthermore, the ends of the second and third vertical beams are connected by a fold-back section. Additionally, the ends of the third and fourth vertical beams are connected by a fold-back section. Furthermore, the ends of the fourth and fifth vertical beams are connected by a fold-back section. Additionally, the ends of the fifth and sixth vertical beams are connected by a fold-back section.

[0092] The second drive beam 130b also has a plurality of rectangular vertical beams extending in the direction along the first swing axis A, and a folded-back portion connecting the ends of adjacent vertical beams to each other, and the whole has a sawtooth shape.

[0093] For example, counting from the first drive beam 126b side, the ends of the first and second vertical beams are connected by a fold-back section. Furthermore, the ends of the second and third vertical beams are connected by a fold-back section. Additionally, the ends of the third and fourth vertical beams are connected by a fold-back section. Furthermore, the ends of the fourth and fifth vertical beams are connected by a fold-back section. Additionally, the ends of the fifth and sixth vertical beams are connected by a fold-back section.

[0094] A drive source 134a is formed on the upper surface of the second drive beam 130a for each rectangular unit (vertical beam) that does not include a curved portion. A drive source 134b is formed on the upper surface of the second drive beam 130b for each rectangular unit (vertical beam) that does not include a curved portion.

[0095] The driving source 134a includes an upper electrode formed on a piezoelectric film on the upper surface of the second driving beam 130a and a lower electrode formed on the lower surface of the piezoelectric film. The driving source 134b includes an upper electrode formed on a piezoelectric film on the upper surface of the second driving beam 130b and a lower electrode formed on the lower surface of the piezoelectric film.

[0096] The second drive beams 130a and 130b apply drive voltages to each vertical beam from adjacent drive sources 134a and 134b, causing all vertical beams to warp upwards and transferring the accumulated vertical motion of each vertical beam to the movable frame 122.

[0097] The second drive beams 130a and 130b cause the reflecting surface 121 to oscillate around the second oscillation axis B through this action. For example, non-resonant vibration can be used in the oscillation performed using the second drive beams 130a and 130b.

[0098] For example, drive source 134a includes drive sources 134a1, 134a2, 134a3, 134a4, 134a5, and 134a6 arranged from the right side of movable frame 122. Additionally, drive source 134b includes drive sources 134b1, 134b2, 134b3, 134b4, 134b5, and 134b6 arranged from the left side of movable frame 122. In this case, by driving drive sources 134a1, 134b1, 134a3, 134b3, 134a5, and 134b5 with the same waveform, and driving drive sources 134a2, 134b2, 134a4, 134b4, 134a6, and 134b6 with the same waveform that is a time-reversed version of the former, the reflecting surface 121 can be made to oscillate around the second oscillation axis B.

[0099] The drive wiring that applies drive voltage to the upper and lower electrodes of the drive source 127a is connected to predetermined terminals included in the terminal group 135a provided in the fixed frame 13. Additionally, the drive wiring that applies drive voltage to the upper and lower electrodes of the drive source 127b is connected to predetermined terminals included in the terminal group 135b provided in the fixed frame 133.

[0100] Additionally, the drive wiring that applies drive voltage to the upper and lower electrodes of the drive source 134a is connected to predetermined terminals included in the terminal group 135a provided in the fixing frame 133. Similarly, the drive wiring that applies drive voltage to the upper and lower electrodes of the drive source 134b is connected to predetermined terminals included in the terminal group 135b provided in the fixing frame 133.

[0101] Additionally, the light deflection unit 12 includes horizontal piezoelectric sensors 137a and 137b. These sensors are horizontal tilt angle sensors that detect the horizontal tilt (horizontal tilt angle) of the reflective surface 121 when it is swinging horizontally, and vibration sensors that detect the timing of laser emission. The horizontal piezoelectric sensors 137a and 137b are mounted on connecting beams 125a and 125b.

[0102] Furthermore, the light deflection unit 12 includes vertical piezoelectric sensors 136a and 136b. These sensors are vertical tilt angle sensors that detect the vertical tilt (vertical tilt angle) of the reflective surface 121 when it is oscillating in the vertical direction, and vibration sensors that detect unwanted vibrations of the vertical beam to remove unwanted vibration components from the drive signal. The vertical piezoelectric sensors 136a and 136b are disposed on one of the vertical beams constituting the second drive beams 130a and 130b.

[0103] Such an optical deflection section 12 can be fabricated, for example, using an SOI (Silicon On Insulator) substrate having a support layer, a buried oxide layer, and an active layer, via semiconductor processes.

[0104] Furthermore, in this embodiment, the first maximum swing angle α1 about the first swing axis A is configured to be larger than the second maximum swing angle α2 about the second swing axis B. For example, the first maximum swing angle α1 is ±12.0 degrees, and the second maximum swing angle α2 is ±7.0 degrees. In addition, the first maximum swing angle α1 is equivalent to the maximum swing angle α.

[0105] <The effect of tilting the light-transmitting plate 3>

[0106] Here, as described above, in a light deflection device equipped with a light-transmitting plate, sometimes a portion of the light deflected by the light deflection unit is reflected back to the light deflection unit instead of passing through the light-transmitting plate, is deflected again by the light deflection unit, and is included in the projected image. Additionally, sometimes a portion of the light incident on the light deflection device is reflected by the light-transmitting plate and included in the projected image. The effect of the tilt of the light-transmitting plate 3 relative to such reflected light from the light-transmitting plate 3 will be explained below.

[0107] Figure 6 This diagram illustrates an example of the incident laser beam onto the light deflection device 20 and the emitted laser beam from the light deflection device 20. The incident laser beam passes through the light-transmitting plate 3 and enters the light deflection device 20. The emitted laser beam passes through the light-transmitting plate 3 and exits from the light deflection device 20.

[0108] exist Figure 6 In the example shown, the incident laser is incident on the light deflection device 20 along a plane containing a first swing axis A along the Y-axis, and the outgoing laser is emitted from the light deflection device 20.

[0109] then, Figure 7 This is a diagram illustrating an example of the tilting effect of the light-transmitting plate 3 in the light deflection device 20. Figure 7 It is along Figure 6 A cross-sectional view of the optical deflection device 20 for the SS cutting line.

[0110] exist Figure 7 In the process, the incident laser L1 passes through the light-transmitting plate 3 and is incident on the reflecting surface 121 of the light deflection section 12. The outgoing laser L2 is emitted after the incident laser L1 is reflected by the reflecting surface 121 and passes through the light-transmitting plate 3.

[0111] The area through which the incident laser L1, incident on the reflective surface 121 of the light deflection section 12, passes through the light-transmitting plate 3 is at a height h1 relative to the mounting surface 111, which is higher than the area through which the outgoing laser L2, deflected by the light deflection section 12, passes through the light-transmitting plate 3 is at a height h2 relative to the mounting surface 111.

[0112] The first reflected laser R1 represents the laser light L1 reflected by the first surface 31 on the +Z direction side of the light-transmitting plate 3. The second reflected laser R2 represents the laser light L1 reflected by the second surface 32 on the -Z direction side of the light-transmitting plate 3.

[0113] A triple-reflected laser R3 indicates that the emitted laser L2 is reflected by the second surface 32 of the light-transmitting plate 3 and then reflected again by the reflecting surface 121 before passing through the light-transmitting plate 3 and exiting. A quadruple-reflected laser R4 indicates that the emitted laser L2 is reflected by the first surface 31 of the light-transmitting plate 3 and then reflected again by the reflecting surface 121 before passing through the light-transmitting plate 3 and exiting.

[0114] Here, the effect of reflected light, including reflected light from the light-transmitting plate 3, in the image projection device 100 will be described in detail.

[0115] The intensity of the incident laser L1 incident on the light deflection device 20 is set to 100%, and the transmittance of the anti-reflective films applied to the first surface 31 and the second surface 32 of the light-transmitting plate 3 is set to 98%.

[0116] In this case, if the incident laser L1 passes through the first surface 31 and the second surface 32, and the emitted laser L2 passes through the first surface 31 and the second surface 32, then 0.98 4 =0.92, the light intensity of the emitted laser L2 is 92% [%.

[0117] For example, when the emitted laser L2 scans the scanned surface 200 and depicts an image 201 on the scanned surface 200 at a resolution of 720P (1280×720 [pixels]), the light intensity of the emitted laser L2 depicting one [pixel] in one frame is 0.0001 [%] based on 92 / (1280×720). That is, one [pixel] is depicted with a light intensity of 0.0001 [%] of the light intensity of the incident laser L1.

[0118] On the other hand, in the image projection device 100, when a primary reflected laser R1 is included in an image 201 on the scanned surface 200, a primary reflected laser R1 with 2% of the light intensity of the incident laser L1 is included in the image 201. This primary reflected laser R1 has a light intensity 20,000 times that of the emitted laser L2 that depicts the image 201, and illuminates a predetermined portion within the image 201 without shifting.

[0119] Furthermore, when the secondary reflected laser R2 is included in the image 201 on the scanned surface 200, according to 0.98 2 A secondary reflected laser R2, representing 0.019% of the intensity of the incident laser L1, is included in the image 201. This secondary reflected laser R2 has an intensity 190 times that of the emitted laser L2 depicting the image 201 and illuminates a predetermined portion within the image 201 without shifting.

[0120] Furthermore, when the triple-reflected laser R3 is included in the image 201 on the scanned surface 200, according to 0.98 4 A triple-reflected laser R3, representing 0.018% of the intensity of the incident laser L1, is included in image 201. This triple-reflected laser R3 has an intensity 180 times that of the emitted laser L2 that depicts image 201, and depicts the same image as image 201 on the scanned surface 200 at a position offset from image 201.

[0121] Furthermore, when the quadruple reflected laser R4 is included in the image 201 on the scanned surface 200, according to 0.98 5 A quadruple reflected laser R4, representing 0.018% of the intensity of the incident laser L1, is included in image 201. This quadruple reflected laser R4 has an intensity 180 times that of the emitted laser L2 that depicts image 201, and depicts the same image as image 201 on the scanned surface 200 at a position offset from image 201.

[0122] In this embodiment, in order to prevent the lasers reflected by the light-transmitting plate 3, such as the first-reflection laser R1 to the fourth-reflection laser R4, from being included in the image 201, the light-transmitting plate 3 is set at an angle relative to the mounting surface 111.

[0123] Here, Figure 7 The tilt angle θ represents the tilt angle of the light-transmitting plate 3 relative to the mounting surface 111. The light-transmitting plate 3 is tilted about the axis along the second swing axis B relative to the mounting surface 111 at the tilt angle θ. In addition, the second maximum swing angle α2 represents the maximum swing angle about the second swing axis B corresponding to the axis along the X-axis.

[0124] In this embodiment, the tilt angle θ is determined in a manner that satisfies the conditions shown by the following formula.

[0125] |θ|=2×α2+β2

[0126] 0<β2≤90-2×α2

[0127] Where β1 and β2 represent the selection angles that can be appropriately chosen. || represents the absolute value. The units of the second maximum swing angle α2, the tilt angle θ, and the selection angles β1 and β2 are [degrees].

[0128] When the tilt angle θ is greater than the second maximum tilt angle α2, the primary reflected light R1 and the secondary reflected light R2 do not reach the scanned surface 200 and are not included in the image 201. In addition, when the tilt angle θ is more than twice the second maximum tilt angle α2, the tertiary reflected light R3 and the quaternary reflected light R4 do not reach the scanned surface 200 and are not included in the image 201.

[0129] Therefore, by determining the tilt angle θ in a manner that satisfies the above formula, it is possible to make the first-reflection laser R1 to the fourth-reflection laser R4 each a state not included in image 201. Figure 7 In the example shown, the second maximum swing angle α2 is 7.0 degrees, and the chosen angle β2 is 4.0 degrees. The tilt angle θ is determined to be 18.0 degrees according to the above formula.

[0130] then, Figure 8 This diagram illustrates the effect of the tilting of the light-transmitting plate 3a in the comparative example's light deflection device 20a. It is provided for easy comparison with the light deflection device 20 of the embodiment. Figure 8 The light deflection device 20a shown has the same structure as the light deflection device 20, except that the tilt angle of the light-transmitting plate 3a relative to the mounting surface 111 (reference surface) is different from that of the light deflection device 20.

[0131] Figure 8 Is along with Figure 6 A cross-sectional view of the SS cutting line corresponding to the cutting line cutting the optical deflection device 20a. Figure 8 In the text, the structural parts of the optical deflection device 20a are labeled with the same part numbers as those of the optical deflection device 20.

[0132] Figure 8 The tilt angle θ' represents the tilt angle of the light-transmitting plate 3a relative to the mounting surface 111. Additionally, the second maximum swing angle α2' represents the maximum swing angle about the second swing axis B.

[0133] The tilt angle θ' is 11.0 degrees, and the maximum swing angle is 7.0 degrees. Since the tilt angle θ' is larger than the second maximum swing angle α2, the primary reflected light R1 and the secondary reflected light R2 are not included in image 201.

[0134] However, the tilt angle θ' is less than twice the second maximum tilt angle α2, i.e., 14 degrees. Therefore, the third reflected light R3 and the fourth reflected light R4 are emitted in a direction close to the emitted laser L2 and are included in image 201. As a result, an image identical to image 201 is projected onto the scanned surface 200 at a position slightly offset from image 201. Multiple images overlap to produce visually recognizable multiple images, moiré patterns, etc.

[0135] <Effect of optical deflection device 20>

[0136] As described above, the light deflection device 20 of this embodiment includes a light deflection section 12 that deflects the laser incident on the reflective surface 121 by oscillating the reflective surface 121 around a first oscillation axis A (first axis) and a second oscillation axis B (second axis), and a light-transmitting plate 3 that allows the laser deflected by the light deflection section 12 to pass through.

[0137] Furthermore, in this embodiment, the tilt angle of the light-transmitting plate 3 relative to the mounting surface 111 (reference surface) is more than twice the second maximum tilt angle α2 of the reflecting surface 121 relative to the mounting surface 111. As a result, the primary reflected light R1, secondary reflected light R2, tertiary reflected light R3, and quaternary reflected light R4 that accompany the reflection from the light-transmitting plate 3 do not reach the scanned surface 200. Consequently, the projected image can be free of reflected light from the light-transmitting plate 3. Moreover, the quality of the image projected onto the scanned surface 200 can be ensured to a higher degree.

[0138] Furthermore, in the above embodiment, a structure is illustrated in which the light-emitting part 10 causes the laser to enter the interior of the light deflection device 20 from the outside of the light-transmitting plate 3, but it is not limited to this. This embodiment can be applied even if the light-emitting part 10 is provided inside the light deflection device 20 and the laser does not pass through the light-transmitting plate 3 but enters the reflective surface 121.

[0139] Furthermore, in this embodiment, the light deflection unit 12 deflects the laser light incident on the reflective surface 121 in the two intersecting directions by oscillating the reflective surface 121 about both the first oscillation axis A and the second oscillation axis B that intersects the first oscillation axis A. Moreover, the first maximum oscillation angle α1 of the reflective surface 121 relative to the mounting surface 111 about the first oscillation axis A is larger than the second maximum oscillation angle α2 of the reflective surface 121 relative to the mounting surface 111 about the second oscillation axis B, and the light-transmitting plate 3 is tilted about the axis along the second oscillation axis B.

[0140] For example, when the light-transmitting plate 3 is tilted about the first swing axis A, the first maximum swing angle α1 is 12.0 degrees, therefore, the light-transmitting plate 3 needs to be tilted by 28.0 degrees (when β1 is 4.0 degrees). In contrast, when tilted about the second swing axis B, the tilt angle of the light-transmitting plate 3 can be 18.0 degrees. Since the tilt angle of the light-transmitting plate 3 is small, at least one of the encapsulation member 11 or the cover 2 can be miniaturized. Moreover, the light deflection device 20 can be miniaturized.

[0141] Furthermore, in this embodiment, a structure in which the first swing axis A is along the Y direction is illustrated, but it is not limited to this; any structure in which the light-transmitting plate 3 is tilted about an axis with a smaller maximum swing angle around the reflecting surface 121 is acceptable. In other words, the first swing axis A can be oriented in any direction. For example, it can also be a structure in which the first swing axis A is along the X direction. Even in this structure, since the tilt angle of the light-transmitting plate 3 is small, at least one of the encapsulation member 11 or the cover 2 can be miniaturized, and the light deflection device 20 can be miniaturized.

[0142] However, when the first maximum swing angle α1 of the reflecting surface 121 relative to the mounting surface 111 about the first swing axis A is larger than the second maximum swing angle α2 of the reflecting surface 121 relative to the mounting surface 111 about the second swing axis B, the light-transmitting plate 3 is not limited to a structure that is tilted about an axis along the second swing axis B. For example, it may also be configured such that the light-transmitting plate 3 is tilted about an axis along the first swing axis A.

[0143] Furthermore, in this embodiment, the area of ​​the laser incident on the reflective surface 121 that passes through the light-transmitting plate 3 is at a height h1 relative to the mounting surface 111, which is higher than the area of ​​the laser that has been deflected by the light deflecting part 12 that passes through the light-transmitting plate 3, which is at a height h2 relative to the mounting surface 111. With this structure, at least one of the encapsulation member 11 or the cover 2 can be miniaturized, and the light deflecting device 20 can also be miniaturized.

[0144] <Modified example of optical deflection device 20>

[0145] Here, the optical deflection device 20 can be modified in various ways, so the following describes some examples of modifications.

[0146] (Modified example of the optical deflection section)

[0147] First, a modified example of the light deflection section will be described. In the above embodiment, a structure of the light deflection section 12 that deflects the laser in two intersecting directions is illustrated, but it is not limited to this. For example, the light deflection device 20 may also include a light deflection section that deflects the light incident on the reflecting surface in one direction by oscillating the reflecting surface around a swing axis.

[0148] Here, Figure 9This is a perspective view illustrating another first example of a light deflection unit. The light deflection unit 12a includes a reflecting surface 121a, and by oscillating the reflecting surface 121a about a second oscillation axis B, the laser light reflected by the reflecting surface 121a is deflected about the second oscillation axis B. The light deflection unit 12a is, for example, a MEMS mirror that uses a piezoelectric element to drive the reflecting surface 121a.

[0149] like Figure 9 As shown, the light deflection unit 12a has a reflective surface 121a, a support part 123a, connecting parts 131aa and 131ba, a second drive beam 130aa and 130ba, a drive source 134a1 and 134ba, a fixed frame connecting part 132aa and 132ba, and a fixed frame 133a.

[0150] The light deflection section 12a replaces the movable frame 122 of the light deflection section 12 by providing a support section 123a that includes a reflective surface 121a. The functions of each structural part are the same as the corresponding structural parts in the light deflection section 12. Therefore, repeated descriptions are omitted here.

[0151] then, Figure 10 This is a perspective view illustrating another second example of a light deflection section. The light deflection section 12b includes a reflecting surface 121b. By oscillating the reflecting surface 121b about a first oscillation axis A, the laser light incident on the reflecting surface 121b is deflected about the first oscillation axis A. The light deflection section 12b is, for example, a MEMS mirror that uses a piezoelectric element to drive the reflecting surface 121b.

[0152] like Figure 10 As shown, the light deflection unit 12b has a reflective surface 121b, a movable frame 122b, a support part 123b, torsion beams 124ab and 124bb, connecting beams 125ab and 125bb, a first drive beam 126ab and 126bb, and a drive source 127ab and 127bb.

[0153] The optical deflection section 12b removes the second drive beams 130a and 130b, which are connected to the movable frame 122 of the optical deflection section 12. The function of each component is the same as that of the corresponding component in the optical deflection section 12. Therefore, repeated descriptions are omitted here.

[0154] The optical deflection device 20 can also be equipped with Figure 9 and Figure 10 The light deflector shown is a light deflector that swings the reflective surface around a swing axis. In this case, by making the tilt angle of the light-transmitting plate 3 relative to the mounting surface 111 more than twice the maximum swing angle of the reflective surface 121 relative to the mounting surface 111, the same effect as the light deflector 20 described above can also be obtained.

[0155] (Example of deformation in the direction that causes the light-transmitting plate 3 to tilt)

[0156] Next, a variation of the direction in which the light-transmitting plate 3 is tilted will be described. In the above embodiment, a structure in which the light-transmitting plate 3 is tilted about an axis along the second swing axis B is illustrated, but it is not limited to this. For example, the light-transmitting plate 3 may be tilted about an axis along the first swing axis A at an angle of tilt that is more than twice the first maximum swing angle α1 of the reflecting surface 121 about the first swing axis A.

[0157] Alternatively, the light-transmitting plate 3 can be tilted about an axis other than the axes of the first swing axis A and the second swing axis B. In other words, the light-transmitting plate 3 can also be tilted about an axis contained in a plane parallel to the mounting surface 111, that is, an axis that is not parallel to the first swing axis A and the second swing axis B.

[0158] Here, Figure 11 These are schematic diagrams illustrating other examples of the tilt of the light-transmitting plate 3. In Figure 11 In the diagram, plane 111A represents the plane containing the first swing axis A and the second swing axis B, plane 111B represents the plane corresponding to the mounting surface 111, which serves as the reference surface, and plane 111C represents the plane parallel to the mounting surface 111.

[0159] The tilt axis 35 is an axis contained in plane 111C (a plane parallel to the reference plane), and is not parallel to the first swing axis A and the second swing axis B. The light-transmitting plate 3 can also be tilted around the tilt axis 35.

[0160] Furthermore, the tilt axis 35 can also be an axis oriented in any of the 360-degree directions around the orthogonal axis D, which is orthogonal to planes 111A, 111B, and 111C, respectively. Alternatively, the tilt axis 35 does not necessarily have to pass through the orthogonal axis D.

[0161] When the light-transmitting plate 3 is tilted about the tilting axis 35, and the tilting angle of the light-transmitting plate 3 about the first swing axis A is set to θ1, and the tilting angle of the light-transmitting plate 3 about the second swing axis B is set to θ2, it is preferable to satisfy the conditions shown in the following formula.

[0162] |θ1|=2×α1+β1

[0163] |θ2|=2×α2+β2

[0164] 0<β1≤90-2×α1

[0165] 0<β2≤90-2×α2

[0166] Furthermore, β1 and β2 represent the selected angles, and the units of α1, α2, θ1, θ2, β1, and β2 are [degrees]. By satisfying this condition, the same effect as the aforementioned light deflection device 20 can be obtained.

[0167] Furthermore, when the light deflection device 20 has a light deflection section 12 that causes the reflective surface 121 to oscillate about a swing axis, it is preferable to tilt the light-transmitting plate 3 about an inclined axis included in a plane 111C parallel to the mounting surface 111, that is, an inclined axis 35 that is not parallel to the swing axis. As a result, at least one of the encapsulation 11 or the cover 2 can be miniaturized.

[0168] (Example of deformation in the incident height of incident laser L1 towards the light-transmitting plate 3)

[0169] In the above embodiments, an example is shown where the height h1 of the area through which the incident laser L1 passes through the light-transmitting plate 3 relative to the mounting surface 111 is higher than the height h2 of the area through which the emitted laser L2 passes through the light-transmitting plate 3 relative to the mounting surface 111, but the embodiment is not limited to this.

[0170] For example, the area through which the emitted laser L2 passes through the light-transmitting plate 3 may be at a higher height relative to the mounting surface 111 than the area through which the incident laser L1 passes through the light-transmitting plate 3 may be at a higher height relative to the mounting surface 111, or the area through which the incident laser L1 passes through the light-transmitting plate 3 may be at a higher height relative to the mounting surface 111 than the area through which the emitted laser L2 passes through the light-transmitting plate 3 may be at a higher height relative to the mounting surface 111.

[0171] (An example of the combination of incident height and tilt of incident laser L1 in light-transmitting plate 3)

[0172] Next, refer to Figures 12 to 14 This describes various combinations of the incident height of the incident laser L1 onto the light-transmitting plate 3 and the tilt of the light-transmitting plate 3.

[0173] first, Figure 12 This is a diagram representing the first example. Figure 12 (a) is a perspective view of the optical deflection device 20. Figure 12 (b) is along Figure 12 (a) A cross-sectional view of the TT cut line. Figure 12 In this configuration, incident laser L1 is incident on the light deflection device 20 along a plane including the second swing axis B along the X-axis, and outgoing laser is emitted from the light deflection device 20. Additionally, the light-transmitting plate 3 is tilted about the second swing axis B along the X-axis.

[0174] In this case, the tilt angle θ of the light-transmitting plate 3 is preferably more than twice the second maximum swing angle α2 of the reflecting surface 121. In addition, the tilt angle θ of the light-transmitting plate 3 is particularly preferably equal to twice the second maximum swing angle α2 of the reflecting surface 121 plus 2.0 degrees as the selection angle β2.

[0175] then, Figure 13 This is a diagram representing the second example. Figure 13 (a) is a perspective view of the optical deflection device 20. Figure 13(b) is along Figure 13 A cross-sectional view of the UU cut line in (a). Figure 13 In this configuration, incident laser L1 is incident on the light deflection device 20 along a plane including a first swing axis A along the X-axis, and outgoing laser is emitted from the light deflection device 20. Additionally, the light-transmitting plate 3 is tilted about the first swing axis A along the Y-axis.

[0176] In this case, the tilt angle θ of the light-transmitting plate 3 is preferably more than twice the first maximum swing angle α1 of the reflecting surface 121. In addition, the tilt angle θ of the light-transmitting plate 3 is particularly preferably equal to twice the first maximum swing angle α1 of the reflecting surface 121 plus 2.0 degrees as the selection angle β2.

[0177] then, Figure 14 This is a diagram representing the third example. Figure 14 (a) is a perspective view of the optical deflection device 20. Figure 1 (b) is along Figure 14 (a) A cross-sectional view of the VV cut line. Figure 14 In this configuration, incident laser L1 is incident on the light deflection device 20 along a plane including a first swing axis A along the Y-axis, and emitted laser is emitted from the light deflection device 20. Additionally, the light-transmitting plate 3 is tilted about the first swing axis A along the Y-axis.

[0178] In this case, the tilt angle θ of the light-transmitting plate 3 is preferably more than twice the first maximum swing angle α1 of the reflecting surface 121. In addition, the tilt angle θ of the light-transmitting plate 3 is particularly preferably equal to twice the first maximum swing angle α1 of the reflecting surface 121 plus 2.0 degrees as the selection angle β2.

[0179] The embodiments have been described above, but the present invention is not limited to the specific embodiments disclosed above, and various modifications and alterations can be made without departing from the claims.

[0180] Furthermore, the ordinal numbers, quantities, and other numerical values ​​used in the description of the embodiments are all illustrative for the purpose of specifically illustrating the technology of the present invention, and the present invention is not limited to the illustrative numbers. In addition, the connection relationships between structural elements are illustrative for the purpose of specifically illustrating the technology of the present invention, and are not limited to the connection relationships that realize the functions of the present invention.

Claims

1. An optical deflection device, characterized in that, have: The light deflection section deflects the light incident on the reflecting surface by oscillating the reflecting surface about a swing axis. A light-transmitting plate that allows light deflected by the light-deflecting part to pass through and projects an image onto the scanned surface. The light deflection section deflects incident light in two intersecting directions by oscillating the reflecting surface about a first axis and a second axis that intersects the first axis. The first maximum swing angle of the reflecting surface about the first axis relative to the reference plane is greater than the second maximum swing angle of the reflecting surface about the second axis relative to the reference plane. The tilt angle of the light-transmitting plate relative to the reference surface is determined in such a way that it is more than twice the second maximum tilt angle of the reflecting surface relative to the reference surface, so as to prevent light that is reflected by the surface of the light-transmitting plate and returns to the light deflection section, and then reflected by the reflecting surface and transmitted through the light-transmitting plate to reach the scanned surface.

2. The optical deflection device according to claim 1, characterized in that, The light-transmitting plate is inclined about an axis contained in a plane parallel to the reference plane, that is, an axis that is not parallel to the first axis and the second axis.

3. The optical deflection device according to claim 1, characterized in that, The light-transmitting plate is tilted about an axis along the second axis.

4. The optical deflection device according to claim 1, characterized in that, The light-transmitting plate is tilted about an axis along the first axis.

5. The optical deflection device according to any one of claims 1 to 4, characterized in that, When the first maximum swing angle is set to α1, the second maximum swing angle is set to α2, the tilt angle of the light-transmitting plate about the first axis is set to θ1, and the tilt angle of the light-transmitting plate about the second axis is set to θ2, the following condition is satisfied: |θ1|=2×α1+β1 |θ²|=2×α²+β² 0≤β1≤90−2×α1 0≤β2≤90−2×α2 Where β1 and β2 represent the selected angles, || represents the absolute value, and the units of α1, α2, θ1, θ2, β1, and β2 are degrees.

6. The optical deflection device according to any one of claims 1 to 4, characterized in that, The light passes through the light-transmitting plate and then strikes the reflective surface. The area where the light incident on the reflective surface passes through the light-transmitting plate is at a higher height relative to the reference surface than the area where the light deflected by the light-deflecting part passes through the light-transmitting plate is at a higher height relative to the reference surface.

7. An image projection device, characterized in that, have: The light-emitting part; as well as The optical deflection device according to any one of claims 1 to 6, The light is scanned using the light deflection device, thereby projecting an image onto the scanned surface.

Images