Projector module and retinal projection display device equipped therewith

Abstract

This projector module (10000) can be used in a retinal projection display device, and is movable via a moving means. The projector module (10000) comprises a laser module (1000) having a plurality of laser chips, a collimation lens (2000) that converts light from the laser module (1000) into parallel light rays, and a light scanning device (3000) that changes the direction of and scans the light from the collimation lens (2000), and the relative positions of the laser module (1000), the collimation lens (2000), and the light scanning device (3000) are fixed.

Description

[Technical Field]

[0001] The present invention relates to a projector module and a retinal projection display device equipped therewith. [Background technology]

[0002] Augmented reality (AR) glasses and virtual reality (VR) glasses are expected to be small, wearable image display devices. In such devices, a light-emitting module that emits full-color visible light is one of the central elements for rendering high-quality images. In such devices, the light-emitting module independently and rapidly modulates the intensity of each of the three RGB colors that represent visible light, for example, to represent an image in the desired color.

[0003] As a method for modulating the light intensity of the three RGB colors in such a light-emitting module, Patent Document 1 discloses a method of emitting a color image by controlling the emission intensity of each color laser chip with an electric current. Furthermore, Reference Document 2 discloses a method in which laser light is guided by an optical fiber to a modulator having a waveguide formed on a substrate having an electro-optic effect, and the intensity of each of the three RGB colors is independently modulated by the modulator.

[0004] For wearable image display devices such as AR glasses and VR glasses, miniaturizing the light-emitting module so that all functions fit into the size of regular eyeglasses is key to widespread adoption. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-86976 [Patent Document 2] Patent No. 6728596 [Patent Document 3] Japanese Patent Publication No. 2009-130988 [Patent Document 4] Patent No. 2012-170270 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the light-emitting element disclosed in Reference 1, the laser emission intensity is directly controlled by current. However, in current control, it is necessary to control the current around a current value that is above a certain threshold current in order to ensure the stability of the emission intensity. As a result, there is a problem that power consumption is high and difficult to reduce.

[0007] Furthermore, Reference 2 discloses an optical modulator using a substrate made of lithium niobate, lithium tantalate, lead lanthanum zirconate titanate, potassium titanate phosphate, polythiophene, liquid crystal materials, and various inductive polymers that exhibit electro-optic effects, with an optical waveguide provided on this substrate. In particular, a preferred configuration is disclosed in which a single crystal or solid solution crystal of lithium niobate is used, and a portion of it is modified by a proton exchange method or a Ti diffusion method to form the optical waveguide. However, since the size of the modified waveguide portion (core) region is determined by the distance over which protons or Ti penetrate and diffuse, it is difficult to reduce the diameter of the optical waveguide. Therefore, the size of the optical waveguide itself inevitably becomes large, and because the diameter of the optical waveguide is large, the electric field of the modulation voltage does not concentrate easily, requiring either a large voltage to be applied for modulation, or a long electrode to apply the voltage to operate at a small voltage, which results in a large device size.

[0008] Furthermore, in a modulator using a modified portion B1-a of a bulk lithium niobate single crystal B1 as an optical waveguide, as shown in Figure 22(a), the refractive index difference Δn is created by simply adding a small amount of Ti to the bulk lithium niobate single crystal. Therefore, the refractive index difference between the modified waveguide portion (core) and the unmodified portion (cladding) is small. Consequently, the bending loss due to bending the optical waveguide is large, and it is not possible to bend the optical waveguide with a high curvature. This makes it difficult to reduce the size of the device. In addition, modulation light sources mounted on head-mounted displays such as AR glasses require a size that fits within the size of, for example, the temples of eyeglasses. However, it is difficult to fabricate an optical modulator miniaturized to such a size using a bulk crystal type optical modulator like the one in Reference 2.

[0009] A modulator using a modified portion B1-a of a lithium niobate single crystal B1 as an optical waveguide, and a convex portion F made from a single-crystal lithium niobate film F that has been epitaxially grown on a substrate such as sapphire, as shown in Figure 22(b). ridge In the case of a modulator using a Ti diffusion optical waveguide, the convex portion is smaller in size compared to a Ti diffusion optical waveguide, the area around the convex portion is entirely cladding, so the refractive index difference Δn can be increased by appropriately selecting the surrounding material, and the optical loss when the optical waveguide is bent into a curve is smaller compared to bulk lithium niobate single crystal, making it suitable for miniaturization.

[0010] Furthermore, Figure 7 of Reference 2 discloses an optical module 100 in which a light source unit 311 and a modulator 30 are modularized as constituent units, and the light source unit 311 is not directly modulated, but externally modulated light is emitted by the modulator 30. When an optical module with a configuration in which red (R), green (G), and blue (G) laser light is output from the modulator 30 and then combined is used as a component of an optical engine, as in the optical module 100 disclosed in Reference 2, the optical system becomes large, as will be discussed later, making it difficult to miniaturize the size of the optical engine.

[0011] Figure 23(a) shows a transparent image display method, which is a typical image display method used in image display devices. In this method, an image is projected onto a transparent half-mirror, and the observer perceives the displayed image by looking at a virtual screen located beyond the half-mirror. In contrast, the retinal projection method shown in Figure 23(b) projects the image directly onto the retina, allowing the user to recognize the displayed image. Because the projected image from the light source can be superimposed on the scenery seen with the naked eye, AR display becomes possible. In this method, the light from the light source is first focused within the pupil before being projected onto the retina, so the image is formed on the retina regardless of the thickness of the lens. This type of vision is called Maxwell's vision, and because it does not use the accommodative function of the eye's lens, it allows for a deep depth of field. In other words, it has the advantage of allowing the projected image to be seen without blurring while the background is in focus. On the other hand, when the pupil moves, it can cause vignetting ("vignetting"), making the displayed image difficult to see, and there is a problem that the eye box (the range in which the center of the pupil can move) is narrow.

[0012] The present invention has been made in view of the above problems, and aims to provide a compact retinal projection display device with a wide field of view that can be mounted on AR glasses, VR glasses, etc., and in which vignetting caused by changes in pupil position is suppressed, as well as a projector module used therein. [Means for solving the problem]

[0013] To solve the above problems, the present invention provides the following means.

[0014] The projector module according to the first aspect of the present invention can be used in a retinal projection display device and is a projector module that can be moved by moving means. The projector module includes a laser module having a plurality of laser chips, a collimation lens that collimates the light from the laser module into parallel light rays, and an optical scanning device that scans by changing the direction of the light from the collimation lens. The relative positions among the laser module, the collimation lens, and the optical scanning device are fixed.

[0015] In the projector module according to the above aspect, the laser module has a multiplexing circuit that multiplexes the light emitted from the plurality of laser chips. The light emitted from the plurality of laser chips is modulated by a drive current, and the light multiplexed by the multiplexing circuit is collimated by the collimation lens. The optical scanning device may perform scanning with the collimated light.

[0016] In the projector module according to the above aspect, the laser module has a plurality of Mach-Zehnder type optical waveguides through which the light emitted from the plurality of laser chips is guided, and a multiplexing section that multiplexes the modulated light from the plurality of Mach-Zehnder type optical waveguides. The light multiplexed by the multiplexing section may be collimated by the collimation lens, and the direction of the collimated light may be changed by the optical scanning device for scanning.

[0017] In the projector module according to the above aspect, as the collimation lens, there are a plurality of collimation lenses having the same number as the plurality of laser chips, each of which collimates the light from each of the plurality of laser chips into parallel light rays, and a dichroic mirror that multiplexes the light from each collimated by the plurality of collimation lenses. The direction of the light multiplexed by the dichroic mirror may be changed by the optical scanning device for scanning.

[0018] In the projector module according to the above aspect, as the collimation lens, there may be a plurality of collimation lenses having the same number as the plurality of laser chips, which make the light from each of the plurality of laser chips into parallel light beams, and the light from each collimated by the plurality of collimation lenses enters the light scanning device at different angles from each other, and the direction of each light is changed by the light scanning device and scanned.

[0019] In the projector module according to the above aspect, the Mach-Zehnder type optical waveguide may be one in which a lithium niobate film is processed into a convex shape.

[0020] In the projector module according to the above aspect, the light scanning device may be a MEMS mirror device.

[0021] The retinal projection display device according to the second aspect of the present invention includes the projector module according to the above aspect, moving means for moving the projector module, and pupil position detecting means for detecting the pupil position, and moves the projector module by the moving means in response to a change in the pupil position detected by the pupil position detecting means.

[0022] In the retinal projection display device according to the above aspect, the moving means may be a two-dimensional stage using a linear actuator.

[0023] In the retinal projection display device according to the above aspect, the linear actuator may be a piezoelectric ultrasonic linear motor.

[0024] In the retinal projection display device according to the above aspect, the moving means may be an actuator using a spherical motor.

[0025] In the retinal projection display device according to the above aspect, the moving means may be a voice coil motor.

[0026] In the retinal projection display device according to the above embodiment, magnetic fluid may be filled into the gap of the magnetic circuit sandwiching the coil in the voice coil motor.

[0027] In the retinal projection display device according to the above embodiment, an optical system with a Keplerian telescope configuration may be provided, in which an intermediate imaging plane exists between the optical scanning device and the pupil.

[0028] In the retinal projection display device according to the above embodiment, the focal length of the concave mirror or convex lens or diffracting element having a similar function to a concave mirror on the pupil side of the optical path of the Keplerian telescope configuration may be longer than that of the concave mirror or convex lens or diffracting element having a similar function to a concave mirror on the projector module side.

[0029] In the retinal projection display device according to the above embodiment, a field lens for adjusting the direction of light rays may be provided near the intermediate imaging surface.

[0030] The retinal projection display device according to the above embodiment may also be configured to include a light guide plate between the optical system of the Keplerian telescope configuration and the pupil, and to project an image onto the retina through the light guide plate.

[0031] The retinal projection display device according to the above embodiment may include a diffraction element at the position where the light guide plate is incident from the optical system of the Keplerian telescope configuration, and another diffraction element at the position where the light guide plate is exited to the pupil.

[0032] The retinal projection display device according to the above embodiment may include an incident prism at the position where the light guide plate is incident from the optical system of the Keplerian telescope configuration, and a translucent mirror at the position where the light guide plate is exited to the pupil.

[0033] The retinal projection display device according to the above embodiment may include an incident prism at the position where the light guide plate is incident from the optical system of the Keplerian telescope configuration, and a diffraction element at the position where the light guide plate is exited to the pupil.

[0034] A head-up display according to a third aspect of the present invention uses the retinal projection display device according to the above aspect for each of the left and right eyes, and uses the pupil position detection means to move the projector module by the moving means in accordance with the pupil position of the left and right eyes, and in accordance with the change in the pupil position of the left and right eyes detected by the pupil position detection means.

[0035] In the head-up display according to the above embodiment, the collimation lens of the projector module may be a variable lens, or the distance between the collimation lens and the laser module within the projector module may be variable.

[0036] The head-up display according to the above embodiment may be for in-vehicle use. [Effects of the Invention]

[0037] According to the present invention, it is possible to provide a compact retinal projection display device that can be mounted on AR glasses, VR glasses, etc., and that suppresses vignetting caused by changes in pupil position and has a wide field of view. [Brief explanation of the drawing]

[0038] [Figure 1] A schematic diagram of AR glasses is shown as an example of a retinal projection display device according to this embodiment. [Figure 2] This diagram illustrates the technical significance of the optical system in a Keplerian telescope configuration. [Figure 3] This diagram illustrates the technical significance of the optical system in a Keplerian telescope configuration. [Figure 4] This figure schematically shows an example of a projector module according to the first embodiment, where (a) is a plan view, (b) is a side view seen from the Y direction, and (c) is a side view seen from the X direction. [Figure 5] These are modified examples of the projector module according to the first embodiment, where (a) is the first modified example and (b) is the second modified example. [Figure 6]This is a schematic plan view of an example of an electromagnetically driven MEMS mirror device. [Figure 7] (a) is a schematic perspective view of a typical motor, (b) is a schematic perspective view of a spherical motor, and (c) is a schematic perspective view of a magnetostrictive spherical motor. [Figure 8A] This is a schematic plan view of an example of a laser module. [Figure 8B] This is a schematic plan view of another example of a laser module. [Figure 9] Figure 8B is a schematic cross-sectional view obtained by cutting along line XX. [Figure 10] Figure 8B is a schematic cross-sectional view obtained by cutting along the YY line. [Figure 11] This is a block diagram of the optical modulation output unit 200. [Figure 12] This figure shows the optical modulation curves in each Mach-Zehnder type optical waveguide. [Figure 13] This diagram schematically shows (a) an MMI type multiplexer, (b) a Y-type multiplexer, and (c) a directional coupler. [Figure 14] This is a first configuration example aimed at bringing the ratio of light output for each color closer to 1:1:1. [Figure 15] This is a second configuration example aimed at bringing the ratio of light output for each color closer to 1:1:1. [Figure 16] This is a third configuration example aimed at bringing the ratio of light output for each color closer to 1:1:1. [Figure 17] This is a schematic plan view of a Mach-Zehnder type optical waveguide with a curved section. [Figure 18] This is a schematic diagram illustrating how a linear actuator is used as a means of moving the projector module, causing the projector module to move in response to changes in pupil position, and how light rays from the projector module pass through the pupil. [Figure 19] This is a schematic diagram illustrating how a spherical motor actuator is used as a means of moving the projector module, moving the projector module in response to changes in pupil position, and allowing light rays from the projector module to pass through the pupil. [Figure 20] This is a schematic diagram of AR glasses, which is another example of a retinal projection display device according to this embodiment. [Figure 21] This is a schematic diagram illustrating an example of a head-up display. [Figure 22] (a) is a conceptual diagram illustrating a modulator in which a modified portion of a bulk lithium niobate single crystal is used as an optical waveguide, and (b) is a conceptual diagram illustrating a modulator in which a convex portion made by processing a single-crystal lithium niobate film is used as an optical waveguide. [Figure 23] In image display devices, typical image display methods are (a) the transmissive method and (b) the retinal projection method. [Modes for carrying out the invention]

[0039] The present invention will be described in detail below, with reference to the drawings as appropriate. The drawings used in the following description may show enlarged versions of key features for ease of understanding the features of the present invention, and the dimensional ratios of each component may differ from those in reality. The materials, dimensions, etc., exemplified in the following description are examples only, and the present invention is not limited to them. It is possible to modify and implement the invention as appropriate within the scope of achieving its effects.

[0040] [Retinal projection display device] Figure 1 shows a schematic diagram of AR glasses as an example of a retinal projection display device according to this embodiment. In the figure, characteristic parts are shown in enlargement to make the features of the invention easier to understand. The retinal projection display device 100000 shown in Figure 1 comprises a projector module 10000, a moving means 6000 for moving the projector module 10000, and a pupil position detection means (not shown) for detecting the pupil position. The projector module 10000 can be moved by the moving means 6000 in response to changes in the pupil position detected by the pupil position detection means. The symbol GL represents the temple of the eyeglasses.

[0041] The retinal projection display device according to the present invention can achieve a wide-viewing-angle retinal projection display that prevents vignetting caused by changes in pupil position by moving the projector module 10000 with the moving means 6000.

[0042] The projector module 10000 comprises a laser module 1000 having multiple laser chips, a collimation lens 2000 that converts the light from the laser module 1000 into parallel rays, and an optical scanning device 3000 that changes the direction of the light from the laser module 1000 for scanning, with the relative positions between the laser module 1000, the collimation lens 2000, and the optical scanning device 3000 being fixed.

[0043] The pupil position detection means (not shown) for detecting the pupil position can utilize known techniques. For example, a method can be used that involves photographing the eyeball EYE with a camera and detecting the position of the pupil PP in the eyeball EYE, or a method can be used that involves irradiating the eyeball EYE with light and using the reflected light from the eyeball EYE to detect the position of the pupil PP in the eyeball EYE.

[0044] The AR glasses 100000 shown in Figure 1 further include an optical system 20000A, 20000B with a Keplerian telescope configuration in which an intermediate imaging plane IP exists between the optical scanning device 3000 and the pupil. The optical system of a telescope basically consists of a combination of two lenses (objective lens and eyepiece lens), and a Keplerian telescope is one in which both the objective lens and eyepiece lens are convex lenses. Here, the symbol 20000A corresponds to the objective lens, and the symbol 20000B corresponds to the eyepiece lens. Symbol 20000B is a concave mirror, but it functions similarly to a convex lens. The concave mirror 20000B is a semi-transparent (half-mirror) combiner that superimposes the landscape seen by the observer with the image (video) from the projector module 1000. The observer sees the image as if it is magnified and displayed in the distance through the combiner 20000B. By making the focal length of objective lens 20000A shorter than the focal length of eyepiece lens 20000B, the actuator stroke can be reduced.

[0045] Using Figure 2, we will explain the technical significance of the optical system of a Keplerian telescope configuration. Figures 2(a) and (b) show that in the optical system of a Keplerian telescope, the aperture diaphragm and the MEMS mirror are equivalent. If we only track the center of each beam, the light rays diverging from the position of the aperture diaphragm will be imaged at the center of the pupil. Since the light emitted from the position plane of the aperture diaphragm will be imaged at the position plane of the pupil, this optical system can also be viewed as an optical system similar to that of a semiconductor exposure apparatus (stepper). In this case, it can be seen that there is a position for the MEMS mirror that corresponds to any pupil position. Therefore, it can be seen that the MEMS mirror should be moved in accordance with the movement of the pupil.

[0046] Figure 2 shows the case where the magnification is 1x, but Figure 3 shows the optical system configuration of a Keplerian telescope when the magnification is not 1x. Figure 3 shows the case where the magnification is 0.5x. The input beam diameter doubles at the output. The displacement of the pupil's viewpoint is twice the lateral (perpendicular to the optical axis) displacement of the input aperture diaphragm (MEMS mirror position). The displacement of the pupil's viewpoint is 2^2 = 4 times the vertical (optical axis direction) displacement of the input aperture diaphragm (MEMS mirror position).

[0047] In the retinal projection display device according to the present invention, even if the projector module is moved in accordance with the movement of the pupil position, by employing a Keplerian telescope optical system, it is possible to project light rays onto the pupil position without side effects such as changes in focus.

[0048] The retinal projection display device 100000 shown in Figure 1 is further equipped with a field lens 30000 that adjusts the direction of light rays near the intermediate imaging plane.

[0049] (Projector module (first embodiment)) Figure 4 is a schematic diagram showing an example of a projector module according to the first embodiment, where (a) is a plan view, (b) is a side view seen from the Y direction, and (c) is a side view seen from the X direction. The projector module 10000 shown in Figure 4 can be used in a retinal projection display device and is a projector module that is movable by a means of transport, comprising a laser module 1000 having a plurality of laser chips, a collimation lens 2000 that makes the light from the laser module 1000 into parallel rays, and an optical scanning device 3000 that changes the direction of the light from the collimation lens 2000 and scans, wherein the relative positions between the laser module 1000, the collimation lens 2000 and the optical scanning device 3000 are fixed.

[0050] The projector module according to the first embodiment may include other optical systems in addition to the laser module, collimation lens, and optical scanning device. The projector module 10000 shown in Figure 4 further includes a reflective mirror 4000 that reflects the light parallelized by the collimation lens 2000 to the optical scanning device 3000.

[0051] The laser module 1000 is fixed to the fixed stage 5000 via a support member 1001, the collimation lens 2000 is fixed to the fixed stage 5000 via a support member 2001, and the optical scanning device 3000 is fixed to the fixed stage 5000 via a support member 3001. Since the laser module 1000, the collimation lens 2000, and the optical scanning device 3000 are fixed to the fixed plate 5000 in this way, their relative positions are constant. Therefore, even when the projector module is moved so that the light rays from the projection module can pass through the pupil in response to changes in the pupil position, the relative positions of the laser module 1000, the collimation lens 2000, and the optical scanning device 3000 remain fixed. The fixing plate 5000 is preferably made of a high thermal conductivity material. This is because it can efficiently dissipate the heat generated by the projector module. Examples of high thermal conductivity materials include copper-based materials, aluminum materials, SUS, and high thermal conductivity ceramic substrates such as aluminum nitride and silicon nitride.

[0052] Figure 4 illustrates a linear actuator 6000X as a means of moving the projector module 10000 in the X direction, and a linear actuator 6000Y as a means of moving it in the Y direction. When the linear actuator 6000X is driven, the projector module 10000 can move in the X direction along the guide rail 7000X. When the linear actuator 6000Y is driven, the projector module 10000 can move in the Y direction along the guide rail 7000Y. The fixed stage 5000 is a two-dimensional stage that can move in the X and Y directions using the linear actuators 6000X and 6000Y. Known linear actuators can be used, such as a piezoelectric ultrasonic linear motor. A piezoelectric ultrasonic linear motor is a friction-driven motor that moves a rotor or slider by rubbing it with ultrasonic vibrations excited by a piezoelectric element. Because it uses a piezoelectric element, it has a fast response speed and is a quiet motor that does not generate noise because it does not have a reduction gear.

[0053] The guide rail 7000X is fixed to the mounting base 8000 via support members 7000X1 and 7000X2. The fixed base 8000 is preferably made of a high thermal conductivity material, because it can efficiently dissipate the heat generated. Examples of high thermal conductivity materials include copper-based materials, aluminum materials, SUS, and high thermal conductivity ceramic substrates such as aluminum nitride and silicon nitride.

[0054] In the projector module shown in Figure 4, the components, namely the laser module 1000, the collimation lens 2000, and the optical scanning device 3000, are all arranged on the horizontal surface 5000a of the fixed stage 5000. However, as shown in Figures 5(a) and 5(b), they may also be arranged on a fixed stage having surfaces of different heights and angles. Note that in Figure 4, the illustration of the support members and moving means that support the components has been partially omitted. Components with the same reference numeral are assumed to have similar configurations and their explanation is omitted.

[0055] In the projector module 10000A shown in Figure 5(a), the fixed stage 5000A has a horizontal surface 5000Aa on which the laser module 1000, collimation lens 2000, and reflective mirror 4000 are arranged with or without support members on a surface of the same height, and an inclined surface 5000Ab which is at a lower height than the horizontal surface 5000Aa and inclined toward the horizontal surface 5000Aa, on which the optical scanning device 3000 is arranged with support members. The inclination angle of the inclined surface shown in the figure is about 20°, but the inclination angle can be appropriately set according to the configuration of the projector module and the configuration of the retinal projection display device into which the projector module is incorporated.

[0056] In the projector module 10000B shown in Figure 5(b), the fixed stage 5000B has a horizontal surface 5000Ba on which the laser module 1000, collimation lens 2000, and reflective mirror 4000 are arranged with or without support members on a surface of the same height, and an inclined surface 5000Bb which is at a lower height than the horizontal surface 5000Ab and inclined toward the side away from the horizontal surface 5000Ab, on which the optical scanning device 3000 is arranged with support members. The inclination angle of the inclined surface shown in the figure is about 30°, but the inclination angle can be appropriately set according to the configuration of the projector module and the configuration of the retinal projection display device into which the projector module is incorporated.

[0057] (Optical scanning device) As the optical scanning device 3000, any known means capable of reflecting and scanning incident light can be used, but a MEMS mirror is preferred. This is because MEMS mirror devices have advantages such as a large mirror deflection angle and low power consumption.

[0058] Figure 6 shows a schematic plan view of an example of an electromagnetically driven MEMS mirror device. The MEMS mirror device 3000A has a mirror 3003 that reflects the incident laser light L1. The MEMS mirror device 3000A is a driven mirror manufactured using MEMS (Micro Electro Mechanical Systems) technology. The MEMS mirror device 3000A scans the laser light L1 by oscillating the mirror 3003 around the centerlines of the mutually orthogonal first axis and second axis, respectively.

[0059] The MEMS mirror device 3000A shown in Figure 6 includes, in addition to the mirror 3003, a first movable part 3031, a second movable part 3032, a support part 3033, a first drive coil 3034, a second drive coil 3035, and a magnet 3037. The mirror 3003 is provided on the first movable part 3031. The second movable part 3032 supports the first movable part 3031 so as to be able to swing about the first axis A1 as its centerline. The support part 3033 supports the second movable part 3032 so as to be able to swing about the second axis A2 which intersects the first axis A1 as its centerline. The second movable part 3032 is formed in a frame shape so as to surround the first movable part 3031 and is connected to the first movable part 3031 via a pair of torsion bars 3038 arranged on the first axis A1. The support part 3033 is formed in a frame shape so as to surround the second movable part 3032 and is connected to the second movable part 3032 via a pair of torsion bars 3039 arranged on the second axis A2. The first drive coil 3034 is provided in the first movable part 3031. The control unit (not shown) inputs a first drive signal to the first drive coil 3034 to cause the mirror 3003 to swing with the first axis A1 as its centerline. The second drive coil 3035 is provided in the second movable part 3032. The control unit (not shown) also inputs a second drive signal to the second drive coil 3035 to cause the mirror 3003 to swing with the second axis A2 as its centerline. The magnet 3037 generates a magnetic field that acts on the first drive coil 3034 and the second drive coil 3035.

[0060] The first drive signal is an electrical signal that causes the mirror 3003 to resonate with the first axis A1 as its centerline. When the first drive signal is input to the first drive coil 3034, a Lorentz force acts on the first drive coil 3034 due to its interaction with the magnetic field generated by the magnet 3037. By utilizing this Lorentz force, along with the resonance of the mirror 3003 and the first movable part 3031 at their natural frequencies, the mirror 3003 can be made to resonate with the first axis A1 as its centerline. The second drive signal is an electrical signal that causes the mirror 3003 to move linearly with the second axis A2 as its centerline. When the second drive signal is input to the second drive coil 3035, a Lorentz force acts on the second drive coil 3035 due to its interaction with the magnetic field generated by the magnet 3037. By utilizing the balance between this Lorentz force and the elastic force of the pair of torsion bars 3039, the mirror 3003 can be made to move linearly with the second axis A2 as its centerline.

[0061] The control unit (not shown) controls the MEMS mirror device 3000A as well as the laser module 1000. Control of the laser module 1000 includes controlling the timing of the start and end of projection display on the retinal projection display device, and controlling the color tone by current modulation to the optical semiconductor element and voltage modulation to the Mach-Zehnder type optical waveguide. For example, when the control unit receives an input signal to start projection display, it starts the operation of the MEMS mirror device 3000A. This causes the mirror 3003 of the MEMS mirror device 3000A to start oscillating. The control unit monitors the oscillation state of the MEMS mirror device 3000A by some means to confirm that the oscillation state has reached a steady state and is normal, and only then does it start the output of each optical semiconductor element of the laser module 1000. This is because if laser light is shone on the retina when the MEMS mirror is not operating, the laser light may be concentrated on a part or a single point of the retina, potentially causing retinal damage. As a result, laser light L1 is emitted from the laser module 1000. This causes the laser light L1 emitted from the laser module 1000 to be scanned.

[0062] (Means of transportation) In addition to the linear actuators mentioned above, other known actuators can be used as means of moving the projector module (actuator).

[0063] For example, an actuator using a spherical motor can be used. Figure 7(a) shows a general motor, and Figure 7(b) shows a schematic diagram of a spherical motor. While a general motor has only one degree of freedom, rotating only around its axis of rotation, a spherical motor does not have a specific axis of rotation and can rotate on three axes with a single motor, enabling miniaturization and weight reduction. By using an actuator with a spherical motor, the angle of the projector module changes along with its movement, allowing the center of the projected image to move in the direction of the gaze, thus effectively projecting an image over a wider area. Furthermore, compared to actuators with planar movement, the convergence point of the light rays is adjusted to match the three-dimensional movement of the pupil, so even with a wide field of view, vignetting at the pupil does not occur, preventing the field of view from narrowing due to pupil movement.

[0064] Any type of spherical motor can be used, including magnetostrictive, piezoelectric, and electromagnetic types. Figure 7(c) shows a magnetostrictive spherical motor using a magnetostrictive material for the spherical rotor (see Patent Documents 3 and 4). The size of the spherical motor can be, for example, within a few millimeters in length, width, and depth. A magnetostrictive spherical motor using an Fe-Ga alloy as the magnetostrictive material with high magnetostriction is preferable. Although the displacement is not as large as that of super-magnetostrictive materials containing rare earth elements, it has better workability, high rigidity, and is less expensive compared to super-magnetostrictive materials made of rare earth alloys.

[0065] Figure 7 shows that the spherical rotor comprises a spherical rotor, permanent magnets, a stationary part, and drive units A1, A2, B1, and B2. The spherical rotor is a magnetic material formed in a spherical shape. The spherical motor can control the spherical rotor to rotate in any direction of the three axes (i.e., the x-axis, y-axis, and z-axis). For example, if a stationary stage 5000 is attached to the tip of the spherical rotor, the stationary stage 5000 can be freely controlled in the three axial directions.

[0066] A voice coil motor (VCM) may be used as a means of propulsion. For the VCM (Variable Circuit Management) system, either a 2-axis VCM or a 3-axis VCM can be used. In a VCM, it is preferable that magnetic fluid is filled in the gap of the magnetic circuit surrounding the coil. The magnetic fluid is constrained to the gap by the magnetic field. Since magnetic fluid has a higher thermal conductivity than air, heat generated from the RGB laser module, MEMS mirror, etc., is effectively transferred from the coil through the magnetic fluid to the substrate that fixes the magnet, yoke, and actuator. Although the magnetization of the magnetic fluid is not large, a slight thrust improvement effect can still be expected.

[0067] (Laser module) Any known laser module can be used as the laser module, as long as it has multiple laser chips and a mechanism for combining the light emitted from the multiple laser chips, without any particular limitations. Examples of the combining mechanism include a Planar Lightwave Circuit (PLC) with a directional coupler, or one using a Mach-Zehnder type optical waveguide.

[0068] Figure 8A is a schematic plan view of a laser module 1000D, which comprises multiple semiconductor elements (laser chips) 30D-1, 30D-2, and 30D-3, and an optical multiplexing circuit 200D that combines the light emitted from the multiple semiconductor elements 30D-1, 30D-2, and 30D-3. The optical multiplexing circuit 200D has a waveguide structure having three input ports and one output port. Specifically, it includes a first input waveguide 101D, a second input waveguide 102D, and a third input waveguide 103D into which light emitted from semiconductor elements 30D-1, 30D-2, and 30D-3 respectively is incident, a first directional coupler 104D and a second directional coupler 105D, and an output waveguide 106D connected to the second input waveguide 102D.

[0069] In the laser module 1000D shown in Figure 8A, for example, blue light B (wavelength λ1) is incident on the first input waveguide 101D, green light G (wavelength λ2) is incident on the second input waveguide 102D, and red light R (wavelength λ3) is incident on the third input waveguide 103D. The three colors of light R, G, and B are combined by the first directional coupler 104D and the second directional coupler 105D, and light is emitted from the output port 150Da of the output waveguide 106D.

[0070] The first directional coupler 104D is designed with waveguide length, waveguide width, and gap between waveguides such that it couples the light λ1 incident from the first input waveguide 101D to the second input waveguide 102D, couples the light λ2 incident from the second input waveguide 102D to the first input waveguide 101D, and then couples it back to the second input waveguide 102D. The second directional coupler 105D is designed with waveguide length, waveguide width, and gap between waveguides such that it couples the light λ3 incident from the third input waveguide 103D to the second input waveguide 102D, and transmits the light λ1 and λ2 that were coupled to the second input waveguide 102D in the first directional coupler 104D.

[0071] The color tone of the light emitted from the 150Da output port can be adjusted by modulation (current modulation) of the drive current to the optical semiconductor elements. Current modulation of the optical semiconductor elements may be performed independently for each of the multiple optical semiconductor elements. Alternatively, only some of the optical semiconductor elements may be current-modulated.

[0072] Figure 8B is a schematic plan view of the laser module 1000. In Figure 8B, only a portion of the electrodes for introducing a phase difference to the Mach-Zehnder type optical waveguide are shown. Figure 9 is a schematic cross-sectional view of Figure 8B cut along the XX line. Figure 10 is a schematic cross-sectional view of Figure 8B cut along the YY line.

[0073] The laser module 1000 shown in Figure 8B has multiple Mach-Zehnder type optical waveguides 10-1, 10-2, 10-3 (hereinafter sometimes collectively referred to as "Mach-Zehnder type optical waveguide 10") through which light emitted from multiple semiconductor elements (laser chips) 30-1, 30-2, 30-3 (hereinafter collectively referred to as "optical semiconductor element 30") is guided, and a multiplexing section 50 into which modulated light from the Mach-Zehnder type optical waveguides 10-1, 10-2, 10-3 is combined. The light combined in the multiplexing section 50 is parallelized by a collimation lens 2000, and the direction of the parallelized light is changed and scanned by an optical scanning device 3000.

[0074] The laser module 1000 shown in Figure 8B comprises a light source unit 100 having three optical semiconductor elements 30-1, 30-2, and 30-3 (hereinafter sometimes collectively referred to as "optical semiconductor elements 30") that emit visible light wavelengths from 400 nm to 700 nm, and an optical modulation output unit 200 having three Mach-Zehnder type optical waveguides 10-1, 10-2, and 10-3 (hereinafter sometimes collectively referred to as "Mach-Zehnder type optical waveguides 10"), each made of a lithium niobate film processed into a convex shape, into which the light emitted from the optical semiconductor elements 30-1, 30-2, and 30-3 is incident. Furthermore, the optical semiconductor elements 30-1, 30-2, and 30-3 are mounted on a subcarrier (base) 120, and the Mach-Zehnder type optical waveguides 10-1, 10-2, and 10-3 are formed on a substrate 140.

[0075] In the laser module 1000, by using an optical waveguide made from a single-crystal lithium niobate thin film processed into a convex shape, the size of the optical waveguide can be reduced to less than 1 mm, making it possible to miniaturize the laser module. Furthermore, because an extremely insulating external modulator is controlled by voltage, almost no current is required for intensity modulation, and it operates with the minimum current necessary for laser emission, resulting in low power consumption.

[0076] From the perspective of miniaturization, we will further discuss the advantages of using lithium niobate film when fabricating optical waveguides compared to using bulk lithium niobate single crystals. When using a bulk lithium niobate single crystal to fabricate an optical waveguide, a Ti diffusion waveguide works by diffusing Ti into the bulk lithium niobate single crystal, creating a region with a refractive index higher than the original single crystal. In contrast, when using a lithium niobate film to fabricate an optical waveguide, the lithium niobate film is processed to create a convex portion that forms the optical waveguide. This convex portion is smaller in size compared to that of a Ti diffusion waveguide. Furthermore, when using bulk lithium niobate single crystals, the refractive index difference Δn between the Ti diffusion waveguide (core) and the surrounding single crystal portion (cladding) is small. This is because the refractive index difference Δn is created simply by adding a small amount of Ti to the bulk lithium niobate single crystal. In contrast, when using lithium niobate films, the entire area around the convex portion (core) corresponds to the cladding, so by appropriately selecting the surrounding materials (sapphire substrate and side / top surface materials of the waveguide), the refractive index difference Δn can be increased. As a result, the optical waveguide can be curved with a high curvature, and this curvature allows for a further reduction in the longitudinal size. Moreover, since the interaction length can be increased while keeping the external size small, the driving voltage can be reduced.

[0077] (Optical semiconductor device (laser chip)) Various laser elements can be used as the optical semiconductor element (laser chip) 30. For example, commercially available laser diodes (LDs) such as red light, green light, and blue light can be used. For red light, light with a peak wavelength of 610 nm to 750 nm can be used; for green light, light with a peak wavelength of 500 nm to 560 nm can be used; and for blue light, light with a peak wavelength of 435 nm to 480 nm can be used. In the laser module 1000 shown in Figure 8B, the optical semiconductor elements 30-1, 30-2, and 30-3 are defined as a blue light emitting LD, a green light emitting LD, and a red light emitting LD, respectively. The LDs 30-1, 30-2, and 30-3 are arranged at intervals from each other in a direction approximately perpendicular to the direction of light emission from each LD, and are provided on the upper surface 121 of the subcarrier 120. Hereafter, the code Z of any component may be referred to as Z-1, Z-2, ..., ZK if they are common to the components of these components. The aforementioned K is a natural number greater than or equal to 2. In the laser module 1000 shown in Figure 8B, the number of optical semiconductor elements is exemplified as 3, but it is not limited to 3; 2 or 4 or more elements are acceptable. The multiple optical semiconductor elements may all emit light at different wavelengths, or there may be optical semiconductor elements that emit light at the same wavelength. In addition, light other than red (R), green (G), and blue (B) can be used to emit light, and the mounting order of red (R), green (G), and blue (B) as explained in the diagram does not have to be in this order and can be changed as appropriate.

[0078] LD30 can be mounted on the subcarrier 120 as a bare chip. The subcarrier 120 is composed of, for example, aluminum nitride (AlN), aluminum oxide (Al2O3), silicon (Si), etc. As shown in Figure 10, metal layers 75 and 76 are provided between the subcarrier 120 and LD30. The subcarrier 120 and LD30 are connected via the metal layers 75 and 76. Known methods can be used to form the metal layers 75 and 76, and are not particularly limited, but known methods such as sputtering, vapor deposition, and coating of paste-formed metal can be used. The metal layers 75 and 76 may include, for example, one or more metals selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), lead (Pb), indium (In), nickel (Ni), titanium (Ti), and tantalum (Ta), tungsten (W), an alloy of gold (Au) and tin (Sn), a tin (Sn)-silver (Ag)-copper (Cu) solder alloy (SAC), SnCu, InBi, SnPdAg, SnBiIn, and PbBiIn, or may be composed of one or more metals selected from this group.

[0079] The substrate 140 is not particularly limited as long as it has a refractive index lower than that of the lithium niobate film constituting the Mach-Zehnder type optical waveguide, but a substrate on which a single-crystal lithium niobate film can be formed as an epitaxial film is preferred, and a sapphire single-crystal substrate is preferred. The crystal orientation of the single-crystal substrate is not particularly limited, but for example, since a c-axis oriented lithium niobate film has threefold symmetry, it is desirable that the underlying single-crystal substrate also has the same symmetry, and in the case of a sapphire single-crystal substrate, a C-plane substrate is preferred.

[0080] As shown in Figure 10, the entrance port 61 of the entrance path 13 of each Mach-Zehnder optical waveguide 10 faces the exit port 31-1 of each LD30, and is positioned so that the light emitted from the exit surface 31 of the LD30 can be incident on the entrance path 13. The axis JX-1 of the entrance path 13 substantially coincides with the optical axis AXR of the laser light LR emitted from the exit port 31-1 of the LD30. With this configuration and arrangement, the blue light, green light, and red light emitted from LD30-1, 30-2, and 30-3 can be incident on the entrance path 13 of each Mach-Zehnder optical waveguide 10.

[0081] As shown in Figure 10, the subcarrier 120 can be configured to be directly bonded to the substrate 140 via metal layers 93 (first metal layer 71, second metal layer 72, third metal layer 73). This configuration allows for further miniaturization by eliminating the need for spatial coupling or fiber coupling. In this embodiment, the side surface (first side surface) 122 of the subcarrier 120 facing the substrate 140 and the side surface (second side surface) 42 of the substrate 140 facing the subcarrier 120 are connected via the first metal layer 71, the second metal layer 72, the third metal layer 73, and the anti-reflective film 81. The melting point of the metal layer 75 is higher than the melting point of the third metal layer 73.

[0082] The first metal layer 71 is provided in contact with the side surface 122 by sputtering or vapor deposition, and may contain, or be composed of, one or more metals selected from the group consisting of, for example, gold (Au), platinum (Pt), silver (Ag), lead (Pb), indium (In), nickel (Ni), titanium (Ti), and tantalum (Ta). Preferably, the first metal layer 71 contains at least one metal selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), lead (Pb), indium (In), and nickel (Ni). The second metal layer 72 is provided in contact with the side surface 42 by sputtering or vapor deposition, and may contain, or be composed of, one or more metals selected from the group consisting of, for example, titanium (Ti), tantalum (Ta), and tungsten (W). Preferably, tantalum (Ta) is used for the second metal layer 72. The third metal layer 73 is interposed between the first metal layer 71 and the second metal layer 72 and contains, or may be composed of, one or more metals selected from the group consisting of, for example, aluminum (Al), copper (Cu), AuSn, SnCu, InBi, SnAgCu, SnPdAg, SnBiIn, and PbBiIn. Preferably, AuSn, SnAgCu, and SnBiIn are used for the third metal layer 73.

[0083] The thickness of the first metal layer 71, i.e., the size of the first metal layer 71 in the y-direction, is, for example, 0.01 μm or more and 5.00 μm or less. The thickness of the second metal layer 72, i.e., the size of the second metal layer 72 in the y-direction, is, for example, 0.01 μm or more and 1.00 μm or less. The thickness of the third metal layer 73, i.e., the size in the y-direction, is, for example, 0.01 μm or more and 5.00 μm or less. Furthermore, it is preferable that the thickness of the third metal layer 73 is greater than the thicknesses of the first metal layer 71 and the second metal layer 72. In such a configuration, the aforementioned roles of the first metal layer 71, the second metal layer 72, and the third metal layer 73 are well expressed, and the penetration of the material of the first metal layer 71 into the substrate 140 and the decrease in the adhesive strength between each metal layer are suppressed. The thicknesses of the first metal layer 71, the second metal layer 72, and the third metal layer 73 are measured, for example, by spectroscopic ellipsometry.

[0084] The first metal layer 71 is provided on the side surface facing the substrate 140 or the optical modulation structure layer 150 over substantially the entire surface surface 122, without contacting the metal layer 75. The front ends, i.e., upper ends, of the second metal layer 72 and the third metal layer 73 in the z direction reach the same position as the upper end of the first metal layer 71, for example, on the front side in the z direction. The rear ends, i.e., lower ends, of the second metal layer 72 and the third metal layer 73 in the z direction reach the same position as the lower ends of the subcarrier 20, the first metal layer 71, and the substrate 140, for example. When viewed along the y direction, the first metal layer 71 is formed to be larger than the subcarrier 20 in the x direction.

[0085] As described above, it is preferable that the area of ​​the first metal layer 71, i.e., the size in the plane including the x and z directions, is approximately the same as the area of ​​the second metal layer 72 and the third metal layer 73, and that its lower end reaches the same position as the lower end of the subcarrier 120. In such a configuration, the connection strength of the subcarrier 120 to the substrate 140 is maximized. That is, even if, for example, each of the LD30 and the subcarrier 120 is connected to the internal electrode pad corresponding to each LD30 among the multiple internal electrodes using wire bonding, the disconnection of the connection between the subcarrier 120 and the substrate 140 can be suppressed. Furthermore, by having the lower ends of the subcarrier 20, the first metal layer 71, the second metal layer 72, the third metal layer 73 and the substrate 140 reach the same position, the number of heat dissipation paths from the subcarrier 120 can be increased. Note that the area of ​​the first metal layer 71 may be smaller than the area of ​​the second metal layer 72 and the third metal layer 73.

[0086] In the laser module 1000, an anti-reflective film 81 is provided between the LD30 and the optical modulation structure layer 150. For example, the anti-reflective film 81 is integrally formed on the side surface 42 of the substrate 140 and the incident surface 151 of the optical modulation structure layer 150. However, the anti-reflective film 81 may be formed only on the incident surface 151 of the optical modulation structure layer 150.

[0087] The anti-reflective film 81 is a film that prevents incident light to the optical modulation structure layer 150 from being reflected in the opposite direction to the direction in which it enters from the incident surface 151, thereby increasing the transmittance of the incident light. The anti-reflective film 81 is a multilayer film formed by alternately stacking multiple types of dielectrics with predetermined thicknesses corresponding to the wavelengths of the incident light, which are red, green, and blue light. Examples of the aforementioned dielectrics include titanium oxide (TiO2), tantalum oxide (Ta2O5), silicon oxide (SiO2), and aluminum oxide (Al2O3).

[0088] The emission surface 31 of the LD30 and the incident surface 151 of the optical modulation structure layer 150 are positioned at a predetermined distance. The incident surface 151 faces the emission surface 31, and there is a gap 70 between the emission surface 31 and the incident surface 151 in the y-direction. Since the laser module 1000 is exposed to air, the gap 70 is filled with air. Because the gap 70 is filled with the same gas (air), it is easy to inject each color of light emitted from the LD30 into the incident path while satisfying a predetermined coupling efficiency. When the laser module 1000 is used in AR glasses or VR glasses, considering the amount of light required by the AR glasses and VR glasses, the size of the gap (spacing) 70 in the y-direction is, for example, greater than 0 μm and 5 μm or less.

[0089] (Mach-Zehnder optical waveguide) In a Mach-Zehnder optical waveguide, a beam of light with the same wavelength and phase is split into two pairs of beams, each given a different phase, and then merged. The difference in phase causes a change in the intensity of the merged light beam. The optical modulation output unit 200 has three Mach-Zehnder type optical waveguides 10-1, 10-2, and 10-3, the same number as the number of optical semiconductor elements 30-1, 30-2, and 30-3. The optical semiconductor elements 30-1, 30-2, and 30-3 and the Mach-Zehnder type optical waveguides 10-1, 10-2, and 10-3 are positioned so that the light emitted from the optical semiconductor elements is incident on the corresponding Mach-Zehnder type optical waveguide.

[0090] The Mach-Zehnder type optical waveguide 10 (10-1, 10-2, 10-3) shown in Figure 8B has a first optical waveguide 11, a second optical waveguide 12, an input path 13, an output path 14, a branching section 15, and a coupling section 16. The first optical waveguide 11 and the second optical waveguide 12 shown in Figure 1 are configured to extend linearly in the x-direction except near the branching section 15 and the coupling section 16, but the configuration is not limited to this. The lengths of the first optical waveguide 11 and the second optical waveguide 12 shown in Figure 1 are approximately the same. The branching section 15 is located between the input path 13 and the first optical waveguide 11 and the second optical waveguide 12. The input path 13 is connected to the first optical waveguide 11 and the second optical waveguide 12 via the branching section 15. The coupling section 16 is located between the first optical waveguide 11 and the second optical waveguide 12 and the output path 14. The first optical waveguide 11 and the second optical waveguide 12 are connected to the output path 14 via a coupling section 16.

[0091] The Mach-Zehnder type optical waveguide 10 includes a first optical waveguide 11 and a second optical waveguide 12, which are ridge portions (convex) protruding from the first surface 40a of a slab layer 40 made of lithium niobate. Hereinafter, the slab layer 40 made of lithium niobate and the ridge portions 11 and 12 made of lithium niobate together may be referred to as the lithium niobate film. The first surface 40a is the upper surface of the lithium niobate film in the portion other than the ridge portions. The two ridge portions (first ridge portion and second ridge portion) protrude in the z direction from the first surface 40a and extend along the Mach-Zehnder type optical waveguide 10. In this embodiment, the first ridge portion functions as the first optical waveguide 11, and the second ridge portion functions as the second optical waveguide 12. The XX cross-section (cross-section perpendicular to the direction of light propagation) of the ridge portion (first optical waveguide 11 and second optical waveguide 12) shown in Figure 9 is rectangular, the width in the y direction (Wridge) is, for example, 0.3 μm or more and 5.0 μm or less, and the height of the ridge portion (protrusion height H (=T) from the first surface 40a) is rectangular, and the width in the y direction (Wridge) is, for example, 0.3 μm or more and 5.0 μm or less, and the height of the ridge portion (protrusion height H (=T)) is rectangular, and the width in the y direction (Wridge slab -T LN For example, the particle size is between 0.1 μm and 1.0 μm. The shape of the ridge section (first optical waveguide 11 and second optical waveguide 12) is not limited to any shape that can guide light; for example, it may be dome-shaped or triangular.

[0092] The lithium niobate slab layer 40 is, for example, a c-axis oriented lithium niobate film. The lithium niobate slab layer 40 is, for example, an epitaxial film grown epitaxially on a substrate 140. An epitaxial film is a single-crystal film whose crystal orientation is aligned by the underlying substrate. An epitaxial film is a film with a single crystal orientation in the z direction and in the xy plane, and the crystals are aligned in the x, y, and z axis directions. Whether a film is epitaxial can be proven, for example, by checking the peak intensity and poles at the orientation position in 2θ-θ X-ray diffraction. Alternatively, the lithium niobate film 40 made of lithium niobate may be a lithium niobate film provided on a Si substrate via SiO2.

[0093] Lithium niobate is a compound represented as LixNbAyOz. A is an element other than Li, Nb, and O. Examples of elements represented by A include K, Na, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, V, Cr, Mo, W, Fe, Co, Ni, Zn, Sc, and Ce. These elements may be used individually or in combination of two or more. x represents a number between 0.5 and 1.2. Preferably, x is a number between 0.9 and 1.05. y represents a number between 0 and 0.5. z represents a number between 1.5 and 4.0. Preferably, z is a number between 2.5 and 3.5.

[0094] (electrode) Electrodes 21 and 22 are electrodes that apply a modulation voltage Vm to each Mach-Zehnder optical waveguide 10-1, 10-2, and 10-3 (hereinafter sometimes simply referred to as "each Mach-Zehnder optical waveguide 10"). Electrode 21 is an example of a first electrode, and electrode 22 is an example of a second electrode. The first end 21a of electrode 21 is connected to the power supply 131, and the second end 21b is connected to the termination resistor 132. The first end 22a of electrode 22 is connected to the power supply 131, and the second end 22b is connected to the termination resistor 132. The power supply 131 is part of the drive circuit 210 that applies the modulation voltage Vm to each Mach-Zehnder optical waveguide 10.

[0095] Electrodes 23 and 24 are electrodes that apply a DC bias voltage Vdc to each Mach-Zehnder type optical waveguide 10. The first end 23a of electrode 23 and the first end 24a of electrode 24 are connected to a power supply 133. The power supply 133 is part of a DC bias application circuit 220 that applies a DC bias voltage Vdc to each Mach-Zehnder type optical waveguide 10.

[0096] In Figure 9, the line widths and spacing between electrodes 21 and 22, which are arranged in parallel, are made wider than they actually are for clarity. Therefore, the length of the portion where electrode 21 and the first optical waveguide 11 overlap (interaction length) and the length of the portion where electrode 22 and the second optical waveguide 12 overlap appear to be different, but these lengths (interaction lengths) are approximately the same. Similarly, the length of the portion where electrode 23 and the first optical waveguide 11 overlap (interaction length) and the length of the portion where electrode 24 and the second optical waveguide 12 overlap (interaction length) are approximately the same.

[0097] Furthermore, if a DC bias voltage Vdc is superimposed on electrodes 21 and 22, electrodes 23 and 24 may not be provided. Also, ground electrodes may be provided around electrodes 21, 22, 23, and 24.

[0098] Electrodes 21, 22, 23, and 24 are located on a slab layer 40 made of lithium niobate and ridge portions 11 and 12 made of lithium niobate, with a buffer layer 32 in between. Electrodes 21 and 23 can each apply an electric field to the first optical waveguide 11. Electrodes 21 and 23 are each positioned to overlap with the first optical waveguide 11 in a plan view from the z direction, for example. Electrodes 21 and 23 are each located above the first optical waveguide 11. Electrodes 22 and 24 can each apply an electric field to the second optical waveguide 12. Electrodes 22 and 24 are each positioned to overlap with the second optical waveguide 12 in a plan view from the z direction, for example. Electrodes 22 and 24 are each located above the second optical waveguide 12.

[0099] The buffer layer 32 is located between each Mach-Zehnder optical waveguide 10 and electrodes 21, 22, 23, and 24. The protective layer 31 and the buffer layer 32 cover and protect the ridge portion. The buffer layer 32 also prevents light propagating through each Mach-Zehnder optical waveguide 10 from being absorbed by electrodes 21, 22, 23, and 24. The buffer layer 32 has a lower refractive index than the lithium niobate film 40. The protective layer 31 and the buffer layer 32 are, for example, SiInO, SiO2, Al2O3, MgF2, La2O3, ZnO, HfO2, MgO, Y2O3, CaF2, In2O3, etc., or mixtures thereof. The protective layer 31 and the buffer layer 32 may be made of the same material or different materials. If different materials are used, they can be appropriately selected from viewpoints such as improving DC drift, reducing Vπ, and reducing propagation loss.

[0100] The size of the optical modulation output unit 200, which includes a Mach-Zehnder type optical waveguide 10, is, for example, 100 mm. 2 The following applies: The size of the optical modulation output section 200 is 100 mm 2 The following are suitable for use with AR glasses and VR glasses.

[0101] The optical modulation output unit 200, which includes a Mach-Zehnder type optical waveguide 10, can be fabricated by known methods. For example, the optical modulation output unit 200 can be manufactured using semiconductor processes such as epitaxial growth, photolithography, etching, vapor phase growth, and metallization.

[0102] Figure 11 is a block diagram of the optical modulation output unit 200. The control unit 240 of the optical modulation output unit 200 includes a drive circuit 210, a DC bias application circuit 220, and a DC bias control circuit 230. The drive circuit 210 applies a modulation voltage Vm corresponding to the modulation signal Sm to the Mach-Zehnder type optical waveguide 10. The DC bias application circuit 220 applies a DC bias voltage Vdc to the Mach-Zehnder type optical waveguide 10. The DC bias control circuit 230 monitors the output optical signal Lout and controls the DC bias voltage Vdc output from the DC bias application circuit 220. By adjusting this DC bias voltage Vdc, the operating point Vd, which will be described later, is controlled.

[0103] The optical modulation output unit 200 converts an electrical signal into an optical signal. The optical modulation output unit 200 outputs the input light L that is emitted from the optical semiconductor element 30 and input from the input path 13 of the Mach-Zehnder type optical waveguide 10 in as the output light L out and modulates it. The modulation operation of the optical modulation output unit 200 will be described.

[0104] The input light L that is emitted from the optical semiconductor element 30 and input from the input path 13 in branches and propagates through the first optical waveguide 11 and the second optical waveguide 12. The phase difference between the light propagating through the first optical waveguide 11 and the light propagating through the second optical waveguide 12 is zero at the time of branching.

[0105] Next, a voltage is applied between the electrode 21 and the electrode 22. For example, differential signals having the same absolute value, opposite polarities, and non-shifted phases may be applied to each of the electrode 21 and the electrode 22. The refractive indices of the first optical waveguide 11 and the second optical waveguide 12 change due to the electro-optic effect. For example, the refractive index of the first optical waveguide 11 changes from the reference refractive index n to +Δn, and the refractive index of the second optical waveguide 12 changes from the reference refractive index n to -Δn.

[0106] The difference in refractive indices between the first optical waveguide 11 and the second optical waveguide 12 creates a phase difference between the light propagating through the first optical waveguide 11 and the light propagating through the second optical waveguide 12. The light that has propagated through the first optical waveguide 11 and the second optical waveguide 12 merges at the output path 14 and is output as the output light L out The output light L out is the superposition of the light propagating through the first optical waveguide 11 and the light propagating through the second optical waveguide 12. The intensity of the output light L out varies according to an odd multiple of the phase difference between the light propagating through the first optical waveguide 11 and the light propagating through the second optical waveguide 12. In such a procedure, the Mach-Zehnder type optical waveguide 10 modulates the input light L in into the output light L out .

[0107] A modulation voltage Vm corresponding to the modulation signal is applied to electrodes 21 and 22 of the optical modulation output unit 200 for applying the modulation voltage. The voltage applied to electrodes 23 and 24 for applying the DC bias voltage, that is, the DC bias voltage Vdc output from the DC bias application circuit 220, is controlled by the DC bias control circuit 230. The DC bias control circuit 230 adjusts the operating point Vd of the optical modulation output unit 200 by controlling the DC bias voltage Vdc. The operating point Vd is the voltage at the center of the modulation voltage amplitude.

[0108] The optical modulation curves for each Mach-Zehnder type optical waveguide 10 will be explained using Figure 12. Figure 12 is a diagram showing the relationship between the DC bias voltage and the output for a Mach-Zehnder type optical waveguide that does not have a configuration that creates a phase difference between the two optical waveguides (first optical waveguide 11 and second optical waveguide 12) and a Mach-Zehnder type optical waveguide that has a configuration that creates a phase difference between the two optical waveguides. In Figure 12, the horizontal axis is the DC bias voltage applied to electrodes 23 and 24, and the vertical axis is the normalized output from the Mach-Zehnder type optical waveguide 10. The output is normalized with "1" as the case where the phase difference between the light propagating in the first optical waveguide 11 and the light propagating in the second optical waveguide 12 is zero. The solid line shows the characteristics of a Mach-Zehnder type optical waveguide that does not have a configuration that generates a phase difference, while the dashed line shows the characteristics of a Mach-Zehnder type optical waveguide that has a configuration that generates a phase difference.

[0109] In a Mach-Zehnder type optical waveguide that does not have a configuration that generates a phase difference, when no voltage is applied (Vdc=0), light of the same phase passing through the two optical waveguides interferes with each other at the coupling section 16, resulting in a reinforced interference and the output of the Mach-Zehnder type optical waveguide reaching its maximum value.

[0110] (Wave section) The laser module 1000 has a light modulation output unit 200, which includes a multiplexer 50 into which modulated light from three Mach-Zehnder type optical waveguides is combined. The multiplexer 50 combines the light propagating through the output path 14E-2 of the Mach-Zehnder type optical waveguide 10-2 with the light propagating through the output path 14E-3 of the Mach-Zehnder type optical waveguide 10-3, and emits the light from the output port 150a via the output waveguide 51. Unlike the configuration in Patent Document 2, where the multiplexer is spaced apart from the modulator, resolution and color quality are improved. The color tone of the light emitted from the output port 150a can be adjusted by current modulation to the optical semiconductor elements and by voltage modulation to the Mach-Zehnder type optical waveguide. Alternatively, adjustment may be made by combining current modulation to the optical semiconductor elements and voltage modulation to the Mach-Zehnder type optical waveguide. Furthermore, current modulation to the optical semiconductor elements may be performed independently for each of the multiple optical semiconductor elements, or only some of the optical semiconductor elements may be current-modulated. Voltage modulation to the Mach-Zehnder type optical waveguide may be performed independently for each of the multiple Mach-Zehnder type optical waveguides, or only some of the Mach-Zehnder type optical waveguides may be voltage-modulated.

[0111] The multiplexing unit 50 may be any of the following selected from the group consisting of an MMI (Multi-Mode Interferometer) type multiplexer (see Figures 13(a) and 13(b)), a Y-type multiplexer (see Figure 13(c)), and a directional coupler (see Figure 13(d)).

[0112] The wave combiner 50 shown in Figure 13(a) is a wave combiner 50A that combines light propagating through the output path 14E-1 of the Mach-Zehnder type optical waveguide 10-1, light propagating through the output path 14E-2 of the Mach-Zehnder type optical waveguide 10-2, and light propagating through the output path 14E-3 of the Mach-Zehnder type optical waveguide 10-3. The combined light from the wave combiner 50A is output to the output waveguide 51.

[0113] Furthermore, the wave combiner 50 shown in Figure 13(b) consists of a wave combiner 50B-1 that first combines the light propagating through the output path 14E-1 of the Mach-Zehnder type optical waveguide 10-1 with the light propagating through the output path 14E-2 of the Mach-Zehnder type optical waveguide 10-2, and then a wave combiner 50B-2 that combines the light output from the wave combiner 50B-1 and propagates with the light propagating through the output path 14E-3 of the Mach-Zehnder type optical waveguide 10-3, and the light combined from the wave combiner 50B-2 is output to the output waveguide 51.

[0114] Furthermore, the wave combiner 50 shown in Figure 13(c) consists of a wave combiner 50C-1 that first combines the light propagating through the output path 14E-1 of the Mach-Zehnder type optical waveguide 10-1 with the light propagating through the output path 14E-2 of the Mach-Zehnder type optical waveguide 10-2, and then a wave combiner 50C-2 that combines the light output from the wave combiner 50C-1 and propagates with the light propagating through the output path 14E-3 of the Mach-Zehnder type optical waveguide 10-3, and the light combined from the wave combiner 50C-2 is output to the output waveguide 51.

[0115] Furthermore, the combined wave section 50 shown in Figure 13(d) consists of a directional coupling section 50D-1 in which light propagating through the output path 14E-1 of the Mach-Zehnder optical waveguide 10-1 is coupled with light propagating through the output path 14E-2 of the Mach-Zehnder optical waveguide 10-2, and then a directional coupling section 50D-2 in which light propagating through the output path 14E-3 of the Mach-Zehnder optical waveguide 10-3 is coupled to the combined light, and the combined light from the directional coupling section 50D-2 is output to the output waveguide 51.

[0116] The laser module 1000 may have a controller (not shown) that controls the current value injected into each of the three optical semiconductor elements 30 so that the peak output of each wavelength in the light emitted to the outside through the three Mach-Zehnder type optical waveguides 10 is in a predetermined proportion. Since this depends on the user, application, and the sensitivity of human color vision (most sensitive to green), it is possible to appropriately select the peak output of each wavelength so that it is in a predetermined proportion.

[0117] In optical waveguides, it is known that side surface roughness during the etching process is the main cause of optical loss. Furthermore, it is known that this optical loss due to side surface roughness is greater as the wavelength decreases. In other words, when the light propagating through an optical waveguide is blue (B), green (G), and red (R), the magnitude of the optical loss is known to be B > G > R. Therefore, the laser module 1000 may be configured such that the current injected into each of the three optical semiconductor elements 30 is constant, and the three Mach-Zehnder type optical waveguides 10 (10-1, 10-2, 10-3) emit light to the outside, with the peak output of each wavelength being in a predetermined proportion. By setting the current driving the laser to the same value for each wavelength, it becomes possible to use a simple driver, which in turn enables a simpler circuit and further miniaturization. If the configurations of the three Mach-Zehnder optical waveguides are the same, and the optical loss due to lateral roughness does not depend on the color of the light propagating through the waveguide, then the ratio of the output light of each color (or, if there is a multiplexing section, the ratio of the combined light of each color) will be R:G:B=1:1:1. However, because the optical loss due to lateral roughness depends on the color of the light propagating through the waveguide, it becomes possible to compensate for the difference in optical loss due to lateral roughness by making the configurations of the three Mach-Zehnder optical waveguides different from each other. Furthermore, depending on the application, it may be desirable to have a ratio other than R:G:B=1:1:1. In such cases, the configuration of the three Mach-Zehnder optical waveguides can be determined to achieve the desired ratio.

[0118] Figures 14 to 16 show examples of configurations that bring the ratio of light output of each color (or, if there is a multiplexing section, the ratio of light output of each color that is combined) closer to R:G:B=1:1:1.

[0119] The configuration shown in Figure 14 is such that the length of the optical waveguide from the incident end 13a to the exit end 14a of the three Mach-Zehnder type optical waveguides 10 (10-1, 10-2, 10-3) is shorter for Mach-Zehnder type optical waveguides that propagate light with shorter wavelengths. This configuration addresses a problem specific to ridge-type waveguide structures, where propagation loss increases with shorter wavelengths even if the side surface roughness of the ridge is the same. By shortening the length of the optical waveguide in the shorter wavelength structure, the propagation loss at each wavelength can be made uniform. This configuration makes it possible to bring the ratio of the light output of each color (or, if there is a multiplexing section, the ratio of the light output of each color that is combined) closer to R:G:B=1:1:1. In the configuration shown in Figure 14, the output paths 14 are of different lengths, but the input paths 13 may also be of different lengths, or the input paths 13 and output paths 14 may be of different lengths.

[0120] The configuration shown in Figure 15 includes, in each of the three Mach-Zehnder type optical waveguides 10 (10-1, 10-2, 10-3), an optical absorbing section 14A (14Aa, 14Ab, 14Ac) made of a material that absorbs light at the wavelength of the propagating light, extending from the incident end 13a to the exit end 14a. The length of the optical absorbing section 14A in the longitudinal direction of the optical waveguide is shorter for Mach-Zehnder type optical waveguides that propagate light at shorter wavelengths. This configuration also makes it possible to equalize the propagation loss at each wavelength. This configuration makes it possible to bring the ratio of the light output of each color (or, if there is a multiplexing section, the ratio of the light output of each color that is combined) closer to R:G:B=1:1:1. In the configuration shown in Figure 15, the output path 14 has a light-absorbing section 14A, but the input path 13 may also have a light-absorbing section 14A, or both the input path 13 and the output path 14 may have a light-absorbing section 14A.

[0121] The configuration shown in Figure 16 includes a curved section 13B (13Ba, 13Bb, 13Bc) in each of the three Mach-Zehnder type optical waveguides 10 (10-1, 10-2, 10-3) from the incident end 13a to the exit end 14a. The shorter the wavelength of light propagating in the Mach-Zehnder type optical waveguide, the greater the curvature of the curved section 13B and the shorter the length of the curved section 13B. This configuration also makes it possible to equalize the propagation loss at each wavelength. This configuration makes it possible to bring the ratio of the light output of each color (or, if there is a multiplexing section, the ratio of the light output of each color that is combined) closer to R:G:B=1:1:1. In the configuration shown in Figure 16, the curvature of the bent portion 13B is larger and the length of the bent portion 13B is shorter for Mach-Zehnder type optical waveguides that propagate shorter wavelength light. However, it is also possible to have a configuration in which the curvature of the bent portion 13B is larger for Mach-Zehnder type optical waveguides that propagate shorter wavelength light, or a configuration in which the length of the bent portion 13B is shorter. In the configuration shown in Figure 16, the input path 13 has a bend 13B, but the output path 14 may also have a bend 13B, or both the input path 13 and the output path 14 may have a bend 13B.

[0122] The maximum values ​​of the optical outputs emitted through the three Mach-Zehnder type optical waveguides 10 (10⁻¹, 10⁻², 10⁻³) may be the same intensity.

[0123] As shown in Figure 17, each Mach-Zehnder optical waveguide 10' (10-1', 10-2', 10-3') may have curved sections 10A, 10B, and 10C. The curved sections may be located in the 2-mode waveguides 11 and 12 (indicated by reference numerals 10B and 10C), the input path (indicated by reference numeral 10A), or the output path of the Mach-Zehnder optical waveguide. The optical waveguide configuration, in which a single-crystal lithium niobate thin film formed on a substrate is processed into a convex shape, allows for a high refractive index difference between the core (single-crystal lithium niobate thin film) and the cladding (substrate and side / top surface material of the optical waveguide), enabling the optical waveguide to be curved with high curvature. By curving, the size in the longitudinal direction can be further reduced. In addition, since the interaction length can be increased while keeping the external size small, the driving voltage can be reduced.

[0124] [Effect 1 (Means of Transportation 1)] Figure 18 is a schematic diagram illustrating how a linear actuator is used as a means of moving the projector module, moving the projector module in response to changes in pupil position, and allowing light rays from the projector module to pass through the pupil. In the figure, characteristic parts are shown in enlargement to make the features of the invention easier to understand. Components with the same reference numeral have similar configurations and their descriptions are omitted.

[0125] The retinal projection display device 100001A shown in Figure 18 comprises a projector module 10001A, a moving means 6000A for moving the projector module 10001A, and a pupil position detection means (not shown) for detecting the pupil position. The projector module 10001A can be moved by the linear actuator (moving means) 6001A in response to changes in the pupil position detected by the pupil position detection means. In Figure 18, the guide rails and support members between the linear actuator 6001A and the fixed base 8000 are not shown. In Figure 18, (EA0), (EA1), and (EA2) are symbols indicating the position of the pupil, showing that the pupil's position changed and it was located at these three locations. Also, (PA0), (PA1), and (PA2) are symbols indicating the position of the projector module, showing that the projector module was located at these three locations in accordance with the change in the pupil's position.

[0126] The projector module 10001A comprises a laser module 1001A, a collimation lens 2001A that converts the light from the laser module 1001A into parallel rays, and an optical scanning device 3001A that changes the direction of the light from the collimation lens 2001A for scanning. The laser module 1001A, the collimation lens 2001A, and the optical scanning device 3001A are fixed to the fixed stage 5001A, either via or directly without a support member, so their relative positions are constant. Therefore, even when the projector module is moved so that the light rays from the projection module can pass through the pupil in response to changes in the pupil position, the relative positions between the laser module 1001A, the collimation lens 2001A, and the optical scanning device 3001A remain fixed.

[0127] First, let's assume that when the pupil is located at position (EA0), the projection module 10001A is positioned at position (PA0) so that the light ray from the projection module 10001A can pass through the pupil. At this time, the light emitted from the laser module 1001A is parallelized by the collimation lens 2001A, the parallelized light is reflected and scanned by the optical scanning device 3001A, and the light passes through the objective lens 20001A of the optical system of the Keplerian telescope configuration, is reflected by the translucent concave mirror 20001B, converges near the pupil PP, and then projects an image onto the retina.

[0128] Next, when the pupil moves from position (EA0) to position (EA1), the pupil position detection means (not shown) detects the pupil position. Based on the pupil position, the control unit (not shown) calculates the direction and distance of movement of the linear actuator 6001A, and based on this movement information, the linear actuator 6001A moves from position (PA0) to position (PA1). After movement, the light emitted from the laser module 1001A is parallelized by the collimation lens 2001A, the parallelized light is reflected and scanned by the optical scanning device 3001A, and the light passes through the objective lens 20001A of the Keplerian telescope optical system, is reflected by the translucent concave mirror 20001B, converges near the pupil PP, and then projects an image onto the retina.

[0129] Furthermore, when the pupil moves from position (EA1) to position (EA2), the pupil position detection means (not shown) detects the pupil position. The control unit (not shown) calculates the direction and distance of movement of the linear actuator 6001A according to the pupil position, and the linear actuator 6001A moves from position (PA1) to position (PA2) based on this movement information. After movement, the light emitted from the laser module 1001A is parallelized by the collimation lens 2001A, the parallelized light is reflected and scanned by the optical scanning device 3001A, and the light passes through the objective lens 20001A of the Keplerian telescope optical system, is reflected by the translucent concave mirror 20001B, converges near the pupil PP, and then projects an image onto the retina.

[0130] Thus, according to the retinal projection display device 100001A shown in Figure 18, a linear actuator 6001A is used as the means of moving the projector module 10001A, so that the projector module 10001A is moved in accordance with the change in pupil position, the light rays from the projector module 10001A are focused and passed through the pupil, and an image is drawn on the retina.

[0131] [Effect 2 (Means of Transportation 2)] Figure 19 is a schematic diagram illustrating how a spherical motor actuator is used as a means of moving the projector module, moving the projector module in response to changes in pupil position, and allowing light rays from the projector module to pass through the pupil. In the figure, characteristic parts are shown in enlargement to make the features of the invention easier to understand. Components with the same reference numeral have similar configurations and their descriptions are omitted.

[0132] The retinal projection display device 100001B shown in Figure 19 comprises a projector module 10001B, an actuator 6001B that utilizes a spherical motor 6001Ba as a means of moving the projector module 10000B, and a pupil position detection means (not shown) for detecting the pupil position. The projector module 10001B can be moved by the actuator 6001B that utilizes the spherical motor 6001Ba in response to changes in the pupil position detected by the pupil position detection means.

[0133] The projector module 10001B comprises a laser module 1000B, a collimation lens 2001B that parallelizes the light from the laser module 1000B, and an optical scanning device 3001B that changes the direction of the light from the collimation lens 2001B for scanning. The laser module 1000B, the collimation lens 2001B, and the optical scanning device 3001B are fixed to the fixed stage 5001B, either via or directly without a support member, so their relative positions are constant. Therefore, even when the projector module is moved so that the light rays from the projection module can pass through the pupil in response to changes in the pupil position, the relative positions between the laser module 1000B, the collimation lens 2001B, and the optical scanning device 3001B remain fixed.

[0134] First, let's assume that when the pupil is located at position (EA0), the projection module 10001B is positioned at position (PA0) so that the light ray from the projection module 10001B can pass through the pupil. At this time, the light emitted from the laser module 1001B is parallelized by the collimation lens 2001B, the parallelized light is reflected and scanned by the optical scanning device 3001B, and the light passes through the objective lens 20002A of the optical system of the Keplerian telescope configuration, is reflected by the translucent concave mirror 20002B, converges near the pupil PP, and then projects an image onto the retina.

[0135] Next, when the pupil moves from position (EA0) to position (EA1), the pupil position detection means (not shown) detects the pupil position. Based on the pupil position, the control unit (not shown) calculates the direction and distance of movement of the actuator 6001B that utilizes the spherical motor 6001Ba, and based on this movement information, the actuator 6001B that utilizes the spherical motor 6001Ba moves from position (PA0) to position (PA1). After movement, the light emitted from the laser module 1001A is parallelized by the collimation lens 2001B, the parallelized light is reflected and scanned by the optical scanning device 3001B, and the light passes through the objective lens 20001A of the Keplerian telescope optical system, is reflected by the translucent concave mirror 20001B, converges near the pupil PP, and then projects an image onto the retina.

[0136] Furthermore, when the pupil moves from position (EA1) to position (EA2), the pupil position detection means (not shown) detects the pupil position. Based on the pupil position, the control unit (not shown) calculates the direction and distance of movement of the actuator 6001B that utilizes the spherical motor 6001Ba, and based on this movement information, the actuator 6001B that utilizes the spherical motor 6001Ba moves from position (PA1) to position (PA2). After movement, the light emitted from the laser module 1001B is parallelized by the collimation lens 2001B, the parallelized light is reflected and scanned by the optical scanning device 3001B, and the light passes through the objective lens 20001A of the Keplerian telescope optical system, is reflected by the translucent concave mirror 20001B, converges near the pupil PP, and then projects an image onto the retina.

[0137] Thus, according to the retinal projection display device 100001B shown in Figure 19, an actuator 6001B utilizing a spherical motor 6001Ba is used as the means of moving the projector module 10001B. This allows the projector module 10001B to be moved in accordance with changes in the pupil position, and the light rays from the projector module 10001B to be focused and passed through the pupil, thereby drawing an image on the retina. Furthermore, with the retinal projection display device 100001B, by using an actuator 6001B utilizing a spherical motor 6001Ba, movement of approximately 5D (planar pupil position (2D) + pupil position depth (1D) + light ray direction (2D)) becomes possible.

[0138] Figure 20 shows a schematic diagram of AR glasses as another example of a retinal projection display device according to this embodiment. In the figure, characteristic parts are shown in enlargement to make the features of the invention easier to understand. Components with the same reference numeral have similar configurations and their descriptions are omitted. The difference in this example of a retinal projection display device is that the translucent concave mirror 20003B, which corresponds to the translucent concave mirror (combiner) 20000B shown in Figure 1, is embedded in the light guide plate 40000.

[0139] The AR glasses 100001C shown in Figure 20 include a projector module 10001C, a moving means 6001C for moving the projector module 10001C, and a pupil position detection means (not shown) for detecting the pupil position. The projector module 10001C can be moved by the moving means 6001C in response to changes in the pupil position detected by the pupil position detection means. The AR glasses 100001C shown in Figure 20 further include a reflective mirror 4000C and optical systems 20003A and 20003B with a Keplerian telescope configuration. The translucent concave mirror 20003B is embedded in the light guide plate 40000. Light that passes through 20003A and enters the light guide plate 40000 is guided by repeated total internal reflection in the light guide plate 40000, reflected by the translucent concave mirror 20003B, and after converging near the pupil PP, it projects an image onto the retina.

[0140] As a modification of the AR glasses 100001C shown in Figure 20, a configuration may be provided in which a diffracting element having the same function as an incident prism is placed at the incident position from the optical system of the Keplerian telescope configuration of the light guide plate 40000, and another diffracting element having the same function as a translucent concave mirror 20003B is placed at the exit position from the light guide plate 40000 to the pupil.

[0141] As another variation of the AR glasses 100001C shown in Figure 20, an incident prism may be provided at the incident position from the optical system of the Keplerian telescope configuration of the light guide plate 40000, and a translucent mirror may be provided at the exit position from the light guide plate 40000 to the pupil.

[0142] As yet another modification of the AR glasses 100001C shown in Figure 20, an incident prism may be provided at the incident position from the optical system of the Keplerian telescope configuration of the light guide plate 40000, and a diffracting element may be provided at the exit position from the light guide plate 40000 to the pupil.

[0143] The retinal projection display device of the present invention can be used as various display devices such as AR glasses, VR glasses, and in-vehicle head-up displays. An example of its application to an in-vehicle head-up display is described below.

[0144] (Head-up display) A head-up display (HUD) overlays a projected image onto a person's real-world field of view, allowing them to perceive both the real-world image and the projected image simultaneously. For example, in a car, a head-up display allows the driver to see an image displaying driving assistance information superimposed on the background, located in front of the windshield.

[0145] Figure 21 shows a schematic diagram of an in-vehicle wearable head-up display using the retinal projection display device according to the above embodiment. The head-up display 100002 shown in Figure 21 corresponds to either the left or right eye and comprises a projector module 10002, a moving means (e.g., an XYZ 3-axis actuator) 6002 for moving the projector module 10002, and a pupil position detection means (not shown) for detecting the pupil position. The projector module 10002 can be moved by the moving means 6002 in response to changes in the pupil position detected by the pupil position detection means.

[0146] The projector module 10002 comprises a laser module 1002 having multiple laser chips, a collimation lens 2002 that parallelizes the light from the laser module 1002, and an optical scanning device 3002 that changes the direction of the light from the laser module 1002 for scanning. The laser module 1002, the collimation lens 2002, and the optical scanning device 3002 are fixed to the fixed stage 5002, either via or directly without a support member for the optical scanning device 3002, so their relative positions are constant. Therefore, even when the projector module is moved so that the light from the projection module can pass through the pupil in response to changes in the pupil position, the relative positions between the laser module 1002, the collimation lens 2002, and the optical scanning device 3002 remain fixed. The projector module 10002 also includes a reflective mirror 4002 that reflects the light parallelized by the collimation lens 2002 back to the optical scanning device 3002.

[0147] The head-up display 100002 further comprises an objective lens 20002A and an eyepiece lens 20002B, and a field lens 30002, as an optical system in the configuration of a Keplerian telescope, with an intermediate imaging plane IP between the optical scanning device 3002 and the pupil.

[0148] In the head-up display 100002, images such as driving assistance information from the projector module 10002 are reflected by the combiner (windshield glass) 50000 via the Keplerian telescope-configured optical system 20002A and 20002B, and then enter the eyes of the vehicle driver. The driver sees the images of driving assistance information superimposed on the background visible in front of the combiner 50000.

[0149] Each eye is equipped with a separate projector module, which can be operated independently by a different mechanism (actuator). In this case, the mechanism can be operated in response to head movements and the movements of each eyeball. Since images can be shown to the left and right eyes with separate projectors, it is possible to freely create parallax between the images for the left and right eyes, enabling free stereo display. Previously, parallax was created for the left and right eyes using the same display and optical system, so the parallax was constant and the distance of the virtual image was fixed.

[0150] By using a variable collimation lens or by varying the distance between the collimation lens and the laser module, the virtual image distance due to parallax can be matched with the distance perceived by the eye's focusing mechanism. This reduces discomfort. The objective lens, field lens, and eyepiece are common to both eyes (and have a wide rectangular shape), while the projection module and movement mechanism (actuator) are separate for each eye. Using pancake lenses for the eyepiece and objective lens allows for miniaturization. A concave mirror can also be used instead of lenses. By making the focal length of the objective lens shorter than that of the eyepiece, it is possible to reduce the actuator stroke. The field of view (FOV) will be smaller than the beam sweep angle of the MEMS mirror, but an FOV of about 10 degrees x 5 degrees is sufficient for an automotive HUD. [Explanation of Symbols]

[0151] 10-1, 10-2, 10-3 Mach-Zehnder type optical waveguide 11, 12 Optical waveguide 30-1, 30-2, 30-3 Optoelectronic semiconductor devices 50 Wave section 100 Light source section 200 Optical Modulation Output Section 1000, 1000Aa, 1000Ab, 1000Ac, 1000Ba, 1000Bb, 1000Bc, 1001A, 1001B, 1002 Laser Modules 2000, 2000Aa, 2000Ab, 2000Ac, 2000Ba, 2000Bb, 2000Bc collimation lenses 3000, 3000Aa, 3000Ab, 3000Ac, 3000Ba, 3000Bb, 3000Bc Optical Scanning Devices 6000, 6000A, 6000B, 6002 Transportation means 10000, 10000A, 10000B, 10001A, 10001B, 10002, Projector Module 100000, 100000A, 100000B, 100000C Retinal projection display device 100002 Head-Up Display

Claims

1. A projector module that can be used in a retinal projection display device and is movable by means of transport, A laser module having multiple laser chips, A collimation lens that converts the light from the laser module into parallel rays, The device comprises an optical scanning device that scans by changing the direction of light from the collimation lens, The laser module, the collimation lens, and the optical scanning device are fixed to a stationary stage so that their relative positions are fixed. The laser module and the collimation lens are fixed to a surface of the fixed stage at the same height, and the optical scanning device is fixed to a surface at a lower height than the aforementioned surface, or to a surface that is at a lower height than the aforementioned surface and is inclined. A projector module characterized in that the light rays emitted from the projector module are parallel rays that do not focus at any point.

2. The projector module according to claim 1, further comprising a reflective mirror that reflects light parallelized by the collimation lens to the optical scanning device.

3. The laser module has an optical multiplexing circuit that combines the light emitted from the plurality of laser chips. The light emitted from the aforementioned multiple laser chips is modulated by the drive current. The projector module according to claim 1 or 2, wherein the light combined by the optical multiplexing circuit is parallelized by the collimation lens, and the optical scanning device performs scanning using the parallelized light.

4. The laser module includes a plurality of Mach-Zehnder type optical waveguides into which light emitted from the plurality of laser chips is incident, and the plurality of Mach-Zehnder type optical waveguides include a modulation section that modulates the light emitted from the plurality of laser chips and a multiplexing section that combines the modulated light. The projector module according to claim 1 or 2, wherein the light combined in the multiplexing section is parallelized by the collimation lens, and the optical scanning device performs scanning using the parallelized light.

5. The collimation lens comprises a plurality of collimation lenses, each of which is the same number as the plurality of laser chips, and which each makes the light from each of the plurality of laser chips into a parallel beam. The system includes a dichroic mirror that combines the light from each of the multiple collimation lenses that have been made parallel, The projector module according to claim 1 or 2, wherein the direction of light combined by the dichroic mirror is changed and scanned by the optical scanning device.

6. The collimation lens comprises a plurality of collimation lenses, each of which is the same number as the plurality of laser chips, and which each makes the light from each of the plurality of laser chips into a parallel beam. The projector module according to claim 1 or 2, wherein light from each of the multiple remaining rectification lenses, which are parallelized, is incident on the optical scanning device at different angles to each other, and the optical scanning device changes the direction of each light and scans.

7. The projector module according to claim 4, wherein the Mach-Zehnder type optical waveguide is formed by processing a lithium niobate film into a convex shape.

8. The projector module according to any one of claims 1 to 7, wherein the optical scanning device is a MEMS mirror device.

9. A retinal projection display device comprising: a projector module according to any one of claims 1 to 8; a moving means for moving the projector module; and a pupil position detection means for detecting the pupil position, wherein the moving means moves the projector module in response to a change in the pupil position detected by the pupil position detection means.

10. The retinal projection display device according to claim 9, wherein the moving means is a two-dimensional stage using a linear actuator.

11. The retinal projection display device according to claim 10, wherein the linear actuator is a piezoelectric ultrasonic linear motor.

12. The retinal projection display device according to claim 9, wherein the moving means is an actuator using a spherical motor.

13. The retinal projection display device according to claim 9, wherein the moving means is a voice coil motor.

14. The retinal projection display device according to claim 13, wherein in the voice coil motor, magnetic fluid is filled in the gap of the magnetic circuit sandwiching the coil.

15. The retinal projection display device according to any one of claims 9 to 14, comprising an optical system with a Keplerian telescope configuration in which an intermediate imaging plane exists between the optical scanning device and the pupil.

16. The retinal projection display device according to claim 15, wherein the focal length of the concave mirror or convex lens or diffracting element having a function similar to a concave mirror on the pupil side of the optical path of the optical system of the Keplerian telescope configuration is longer than that of the concave mirror or convex lens or diffracting element having a function similar to a concave mirror on the projector module side.

17. The retinal projection display device according to claim 15 or 16, further comprising a field lens for adjusting the direction of light rays near the intermediate imaging surface.

18. A retinal projection display device according to any one of claims 15 to 17, comprising a light guide plate between the optical system of the Keplerian telescope configuration and the pupil, and projecting an image onto the retina through the light guide plate.

19. The retinal projection display device according to claim 18, wherein the light guide plate is provided with a diffraction element at the incident position from the optical system of the Keplerian telescope configuration, and another diffraction element is provided at the exit position from the light guide plate to the pupil.

20. The retinal projection display device according to claim 18, wherein the light guide plate is provided with an incident prism at the incident position from the optical system of the Keplerian telescope configuration, and a translucent mirror is provided at the exit position from the light guide plate to the pupil.

21. The retinal projection display device according to claim 18, wherein the light guide plate is provided with an incident prism at the incident position from the optical system of the Keplerian telescope configuration, and a diffracting element is provided at the exit position from the light guide plate to the pupil.

22. A head-up display comprising using a retinal projection display device according to any one of claims 9 to 21 for each of the left and right eyes, and using the pupil position detection means to move the projector module by the moving means in accordance with the pupil positions of the left and right eyes and in accordance with the changes in the pupil positions of the left and right eyes detected by the pupil position detection means.

23. The head-up display according to claim 22, wherein the collimation lens of the projector module is a variable lens, or the distance between the collimation lens and the laser module in the projector module is variable.

24. A head-up display, wherein the head-up display according to claim 22 or 23 is for use in a vehicle.

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