Optical equipment and optical detection system

Abstract

The optical device includes: a plurality of optical waveguides extending in a first direction and arranged in a second direction intersecting the first direction; and a planar optical waveguide directly or indirectly connected to the plurality of optical waveguides, the plurality of optical waveguides causing light to propagate along the first direction, the planar optical waveguide including: a first mirror and a second mirror facing each other and extending along the first direction and the second direction; and an optical waveguide layer located between the first mirror and the second mirror.

Description

Technical Field

[0001] This disclosure relates to optical devices and optical detection systems. Background Technology

[0002] In the past, various devices have been proposed that can use light to scan space.

[0003] Patent document 1 discloses a structure capable of performing light-based scanning using a drive device that rotates a mirror.

[0004] Patent document 2 discloses an optical phased array having multiple nanophotonic antenna elements arranged in a two-dimensional pattern. Each antenna element is optically coupled to a variable optical delay line (i.e., a phase shifter). In this optical phased array, a coherent beam is guided to each antenna element through a waveguide, and the phase of the beam is shifted by the phase shifter. This allows for a variation in the amplitude distribution of the far-field radiation pattern.

[0005] Patent document 3 discloses an optical deflection element comprising: a waveguide having an optical waveguide layer in which light propagates internally and a first distributed Bragg reflector formed on the upper and lower surfaces of the optical waveguide layer; a light inlet for allowing light to enter the waveguide; and a light outlet formed on the surface of the waveguide for emitting light that has entered from the light inlet and propagated within the waveguide.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2013 / 168266

[0009] Patent Document 2: Japanese Patent Publication No. 2016-508235

[0010] Patent Document 3: Japanese Patent Application Publication No. 2013-16591 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] The present disclosure provides a new optical device that enables light-based scanning with a relatively simple structure.

[0013] Methods used to solve problems

[0014] An optical device according to the present disclosure includes: a plurality of optical waveguides extending in a first direction and arranged in a second direction intersecting the first direction; and a planar optical waveguide directly or indirectly connected to the plurality of optical waveguides, the plurality of optical waveguides causing light to propagate along the first direction, the planar optical waveguide including: a first mirror and a second mirror facing each other and extending along the first direction and the second direction; and an optical waveguide layer located between the first mirror and the second mirror.

[0015] The inclusive or specific form of this disclosure may also be implemented by devices, systems, methods, or any combination thereof.

[0016] Invention Effects

[0017] According to a technical solution disclosed herein, one-dimensional or two-dimensional scanning via light can be achieved with a relatively simple structure. Attached Figure Description

[0018] Figure 1 This is a perspective view schematically illustrating the structure of the optical scanning device previously studied by the inventors of this disclosure.

[0019] Figure 2 This is a schematic diagram illustrating the construction of a waveguide element's cross-section and an example of propagated light.

[0020] Figure 3A It is a diagram showing the cross-section of a waveguide array that emits light in a direction perpendicular to the exit surface of the waveguide array.

[0021] Figure 3B It is a diagram showing the cross-section of a waveguide array that emits light in a direction different from the direction perpendicular to the exit surface of the waveguide array.

[0022] Figure 4 It is a schematic representation of a waveguide array in three-dimensional space.

[0023] Figure 5 This is a schematic diagram of the waveguide array and phase shifter array viewed from the normal direction (Z direction) of the light emission surface.

[0024] Figure 6A This is a three-dimensional view schematically representing a comparative example of an optical device.

[0025] Figure 6B It is a schematic representation Figure 6A A three-dimensional view of the structure on the right.

[0026] Figure 7 It is a schematic representation of from Figure 6A A diagram showing the beam emitted by an optical device.

[0027] Figure 8AThis is a diagram illustrating examples of the intensity distribution of light propagating between two mirrors and examples of the intensity distribution of light emitted into the distance, respectively.

[0028] Figure 8B This is a diagram illustrating examples of the intensity distribution of light propagating between two mirrors and examples of the intensity distribution of light emitted into the distance, respectively.

[0029] Figure 8C This is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance, respectively.

[0030] Figure 9A This is a diagram schematically illustrating the optical device of Embodiment 1.

[0031] Figure 9B It is a schematic representation Figure 9A A three-dimensional diagram of a planar optical waveguide.

[0032] Figure 10 It is a schematic representation of from Figure 9A A diagram showing the state of light emitted by an optical device.

[0033] Figure 11A This is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in Embodiment 1.

[0034] Figure 11B This is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in Embodiment 1.

[0035] Figure 11C This is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in Embodiment 1.

[0036] Figure 12 This is a graph showing the periodic dependence of the crosstalk rate occurring between multiple optical waveguides 11.

[0037] Figure 13A This is a diagram schematically illustrating a first variation of the optical device of Embodiment 1.

[0038] Figure 13B This is a diagram schematically illustrating a second variation of the optical device of Embodiment 1.

[0039] Figure 14A This is a schematic cross-sectional view of the XZ plane of an example of the optical device of Embodiment 2.

[0040] Figure 14B This is a schematic cross-sectional view in the XY plane of an example of the optical device of Embodiment 2.

[0041] Figure 15 It is a schematic representation of from Figure 14A and Figure 14B A diagram showing the beam emitted by an optical device.

[0042] Figure 16A It is a diagram showing the intensity distribution of light propagating between two mirrors on the XY plane.

[0043] Figure 16B It is a diagram showing the intensity distribution of light propagating between two mirrors on the XZ plane.

[0044] Figure 17A This is a schematic diagram illustrating the first example of a structure used to drive a planar optical waveguide.

[0045] Figure 17B This is a schematic diagram illustrating the second example of a structure used to drive a planar optical waveguide.

[0046] Figure 18 This is a diagram illustrating an example of the structure of an optical scanning device with components integrated on a circuit board.

[0047] Figure 19 This is a schematic diagram illustrating a situation where a two-dimensional scan is performed by irradiating a laser beam or similar object from a light scanning device into a distant location.

[0048] Figure 20 This is a block diagram representing a structural example of a LiDAR system. Detailed Implementation

[0049] Before describing the embodiments of this disclosure, the understanding that forms the basis of this disclosure will be explained.

[0050] The inventors of this disclosure have discovered that conventional optical scanning devices have the following problem: it is not easy to scan space with light without complicating the structure of the device.

[0051] For example, the technology disclosed in Patent Document 1 requires a drive device to rotate the mirror. Therefore, the structure of the device becomes complex, and it is not robust against vibration.

[0052] In the optical phased array described in Patent Document 2, light needs to be branched and directed to multiple column waveguides and multiple row waveguides to guide the light to multiple antenna elements arranged in a two-dimensional configuration. Therefore, the wiring of the waveguides used to guide the light becomes very complex. Furthermore, the range of the two-dimensional scan cannot be increased. Moreover, in order to vary the amplitude distribution of the emitted light in the far field in a two-dimensional manner, phase shifters need to be connected to each of the multiple antenna elements arranged in a two-dimensional configuration, and phase control wiring needs to be installed on the phase shifters. This causes the phase of the light incident on the multiple antenna elements arranged in a two-dimensional configuration to change by different amounts. Therefore, the structure of the elements becomes very complex.

[0053] The inventors of this disclosure, addressing the aforementioned problems of the prior art, have researched a structure to solve these problems. Hereinafter, for comparison with embodiments of this disclosure, a structure researched by the inventors before conceiving the embodiments of this disclosure will be described. This structure includes a waveguide element having a pair of opposing mirrors and an optical waveguide layer sandwiched between these mirrors.

[0054] One of the mirrors in a waveguide element has a higher light transmittance than the other, causing a portion of the light propagating in the optical waveguide layer to escape outwards. The direction (or exit angle) of the emitted light, as described later, can be varied by adjusting the refractive index or thickness of the optical waveguide layer, or by changing the wavelength of the light input into the optical waveguide layer. More specifically, by changing the refractive index, thickness, or wavelength, the component of the wavenumber vector of the emitted light along the length of the optical waveguide layer can be varied. This enables one-dimensional scanning.

[0055] Furthermore, when using an array of multiple waveguide elements, two-dimensional scanning can also be achieved. More specifically, by imparting an appropriate phase difference to the light supplied to the multiple waveguide elements and adjusting the phase difference, the direction of mutual reinforcement of the light emitted from the multiple waveguide elements can be changed. Through the change in phase difference, the component of the wavenumber vector of the emitted light intersecting the direction along the length of the optical waveguide layer changes. Thus, two-dimensional scanning can be achieved. Moreover, in performing two-dimensional scanning, it is not necessary to vary the refractive index, thickness, or wavelength of the multiple optical waveguide layers by different amounts. That is, by imparting an appropriate phase difference to the light supplied to the multiple optical waveguide layers and simultaneously changing at least one of the refractive index, thickness, and wavelength of the multiple optical waveguide layers by the same amount, two-dimensional scanning can be performed. In this way, two-dimensional scanning of light can be achieved with a relatively simple structure.

[0056] In this specification, "at least one of refractive index, thickness, and wavelength" refers to at least one selected from the group consisting of the refractive index of the optical waveguide layer, the thickness of the optical waveguide layer, and the wavelength input to the optical waveguide layer. To change the direction of light emission, any one of the refractive index, thickness, and wavelength can be controlled individually. Alternatively, any two or all of these three can be controlled to change the direction of light emission. The wavelength of the light input to the optical waveguide layer can also be controlled, either instead of controlling the refractive index or thickness.

[0057] The above basic principles can be applied not only to the emission of light but also to the reception of optical signals. By changing at least one of the refractive index, thickness, and wavelength, the direction of the receivable light can be changed one-dimensionally. Furthermore, if the phase difference of the light is changed by multiple phase shifters connected to multiple waveguide elements arranged in one direction, the direction of the receivable light can be changed two-dimensionally.

[0058] In this disclosure, "scanning" based on light refers to changing the direction of light. "One-dimensional scanning" refers to changing the direction of light linearly along a direction intersecting that direction. "Two-dimensional scanning" refers to changing the direction of light two-dimensionally along a plane intersecting that direction.

[0059] <Structure Example of an Optical Scanning Device>

[0060] First, as an example, the structure of a two-dimensional scanning optical scanning device previously studied by the inventors of this disclosure will be described.

[0061] Figure 1 This is a perspective view schematically illustrating the structure of an optical scanning device 98 previously studied by the inventors of this disclosure. The optical scanning device 98 includes a waveguide array comprising a plurality of waveguide elements 10. The plurality of waveguide elements 10 each have a position in a first direction (…). Figure 1 The shape extends in the X direction (of the first direction). Multiple waveguide elements 10 extend in a second direction (of the second direction) intersecting the first direction. Figure 1 The waveguide elements 10 are arranged regularly in the Y direction. While propagating light in the first direction, the waveguide elements 10 also direct light out in a third direction D3, which intersects a virtual plane parallel to the first and second directions. In this embodiment, the first direction (X direction) and the second direction (Y direction) are orthogonal, but they may not be orthogonal. In this embodiment, the waveguide elements 10 are arranged at equal intervals in the Y direction, but they do not necessarily need to be arranged at equal intervals.

[0062] For reference, the X, Y, and Z axes, which are orthogonal to each other, are schematically shown. In this specification, the direction in which the arrow points to the axis is designated as the "+" direction, and the opposite direction is designated as the "-" direction. Furthermore, the orientation of the structures shown in the accompanying drawings is set for ease of explanation and does not limit the orientation in actual implementation of the embodiments of this disclosure. Moreover, the shape and size of the entirety or a portion of the structures shown in the drawings do not limit the actual shape and size.

[0063] Multiple waveguide elements 10 each have a first mirror 30 and a second mirror 40 (hereinafter simply referred to as "mirrors") facing each other, and an optical waveguide layer 20 located between mirrors 30 and 40. Mirrors 30 and 40 each have a reflecting surface at their interface with the optical waveguide layer 20 that intersects a third direction D3. Mirrors 30 and 40, as well as the optical waveguide layer 20, have a shape that extends in the first direction (X direction).

[0064] Furthermore, as described later, the plurality of first mirrors 30 of the plurality of waveguide elements 10 can also be multiple parts of a mirror integrally formed. Additionally, the plurality of second mirrors 40 of the plurality of waveguide elements 10 can also be multiple parts of a mirror integrally formed. Furthermore, the plurality of optical waveguide layers 20 of the plurality of waveguide elements 10 can also be multiple parts of an optical waveguide layer integrally formed. Multiple waveguides can be formed by at least (1) each first mirror 30 being separately formed from the other first mirrors 30, or (2) each second mirror 40 being separately formed from the other second mirrors 40, or (3) each optical waveguide layer 20 being separately formed from the other optical waveguide layers 20. "Separately formed" includes not only physically setting up space, but also separating the components by sandwiching materials with different refractive indices in between.

[0065] The reflecting surfaces of the first mirror 30 and the second mirror 40 are positioned approximately parallel to each other. Of the two mirrors 30 and 40, at least the first mirror 30 has the property of transmitting a portion of the light propagating in the optical waveguide layer 20. In other words, the first mirror 30 has a higher light transmittance than the second mirror 40. Therefore, a portion of the light propagating in the optical waveguide layer 20 is emitted from the first mirror 30 to the outside. Such mirrors 30 and 40 can, for example, be multilayer mirrors formed of a dielectric-based multilayer film (also known as a "multilayer reflective film").

[0066] By controlling the phase of the light input to each waveguide element 10, the refractive index or thickness of the optical waveguide layer 20 of these waveguide elements 10, or the wavelength of the light input to the optical waveguide layer 20, can be changed synchronously and simultaneously, enabling light-based two-dimensional scanning.

[0067] In order to achieve such two-dimensional scanning, the inventors of this disclosure analyzed the operating principle of the waveguide element 10. Based on the results, light-based two-dimensional scanning was successfully achieved by synchronously driving multiple waveguide elements 10.

[0068] like Figure 1 As shown, if light is input to each waveguide element 10, the light is emitted from the emission surface of each waveguide element 10. The emission surface is located on the opposite side of the reflecting surface of the first mirror 30. The direction D3 of the emitted light depends on the refractive index, thickness, and wavelength of the optical waveguide layer. In this embodiment, at least one of the refractive index, thickness, and wavelength of each optical waveguide layer is controlled synchronously so that the light emitted from each waveguide element 10 is approximately in the same direction. Therefore, the X-direction component of the wavenumber vector of the light emitted from the multiple waveguide elements 10 can be varied. In other words, the direction D3 of the emitted light can be varied along... Figure 1 The direction 101 shown changes.

[0069] Furthermore, since the light emitted from the multiple waveguide elements 10 is directed in the same direction, the emitted light interferes with each other. By controlling the phase of the light emitted from each waveguide element 10, the direction in which the light reinforces each other through interference can be changed. For example, when multiple waveguide elements 10 of the same size are arranged at equal intervals in the Y direction, light with a phase difference of a certain amount is input into each of the multiple waveguide elements 10. By changing this phase difference, the Y-direction component of the wavenumber vector of the emitted light can be changed. In other words, by changing the phase difference of the light introduced into the multiple waveguide elements 10 respectively, the direction D3 in which the emitted light reinforces each other through interference can be changed along... Figure 1 The direction 102 shown changes. This enables light-based two-dimensional scanning.

[0070] The following explains the operating principle of the optical scanning device 98.

[0071] <Operating Principle of Waveguide Elements>

[0072] Figure 2 This is a schematic diagram illustrating the construction of a cross-section of a waveguide element 10 and an example of propagated light. Figure 2 In the middle, will be with Figure 1 The direction perpendicular to the X and Y directions is defined as the Z direction, schematically representing a cross-section of waveguide element 10 parallel to the XZ plane. In waveguide element 10, a pair of mirrors 30 and 40 are arranged to sandwich the optical waveguide layer 20. Light 22, introduced from one end of the optical waveguide layer 20 in the X direction, is positioned on the upper surface of the optical waveguide layer 20. Figure 2 The first mirror 30 on the upper surface and the mirror disposed on the lower surface ( Figure 2The light propagates within the optical waveguide layer 20 through repeated reflections from the second mirror 40 (the lower surface of the first mirror 30). The light transmittance of the first mirror 30 is higher than that of the second mirror 40. Therefore, a portion of the light can be primarily output from the first mirror 30. Depending on the application, the transmittance of both the first and second mirrors can be adjusted to allow light to exit from the second mirror 40 instead of the first mirror 30, or light can be emitted from both the first mirror 30 and the second mirror 40.

[0073] In conventional waveguides such as optical fibers, light propagates along the waveguide through repeated total internal reflection. In contrast, in the waveguide element 10 of this embodiment, light propagates through repeated reflections by mirrors 30 and 40 disposed above and below the optical waveguide layer 20. Therefore, there is no restriction on the propagation angle of the light. Here, the propagation angle of the light is the angle of incidence pointing towards the interface between mirror 30 or 40 and the optical waveguide layer 20. Light incident at an angle closer to perpendicular to mirror 30 or 40 can also propagate. That is, light incident at an angle smaller than the critical angle of total internal reflection can also propagate. Therefore, the group velocity of light in the propagation direction is significantly lower than the speed of light in free space. Thus, the waveguide element 10 has the property that the propagation conditions of light vary significantly with changes in the wavelength of light, the thickness of the optical waveguide layer 20, and the refractive index of the optical waveguide layer 20. Such a waveguide is called a "reflective waveguide" or a "slow-light waveguide."

[0074] The emission angle θ of light emitted from waveguide element 10 into the air is represented by the following equation (1).

[0075] [Formula 1]

[0076]

[0077] According to equation (1), by changing the wavelength λ of light in the air and the refractive index n of the optical waveguide layer 20, w Any one of the thicknesses d of the optical waveguide layer 20 can change the direction of light emission.

[0078] For example, in n w With a refractive index of 2, d = 387 nm, λ = 1550 nm, and m = 1, the emission angle is 0°. If the refractive index is changed by n from this state... w =2.2, then the emission angle changes by approximately 66°. On the other hand, if the thickness changes to d = 420 nm without changing the refractive index, the emission angle changes by approximately 51°. If the wavelength changes to λ = 1500 nm without changing the refractive index and thickness, the emission angle changes by approximately 30°. Thus, by changing the wavelength λ of the light and the refractive index n of the waveguide layer 20... w Any change in either the thickness d of the optical waveguide layer 20 or the thickness d of the waveguide layer 20 can cause a significant change in the direction of light emission.

[0079] Therefore, the optical scanning device 98 of the present disclosure controls the wavelength λ of the light input to the optical waveguide layer 20 and the refractive index n of the optical waveguide layer 20. w The light emission direction can be controlled by at least one of the following: the thickness d of the optical waveguide layer 20. The wavelength λ of the light can also remain constant during operation. In this case, light scanning can be achieved with a simpler structure. The wavelength λ is not particularly limited. For example, the wavelength λ can be included in the wavelength range of 400 nm to 1100 nm (from visible light to near-infrared light), which provides high detection sensitivity using photodetectors or image sensors that typically detect light by absorbing it with silicon (Si). In another example, the wavelength λ can be included in the wavelength range of near-infrared light, from 1260 nm to 1625 nm, where transmission loss in optical fibers or Si waveguides is relatively small. These wavelength ranges are just one example. The wavelength range of the light used is not limited to the wavelength range of visible light or infrared light; for example, it can also be the wavelength range of ultraviolet light.

[0080] In order to change the direction of the emitted light, the optical scanning device 98 may have a first adjustment element that changes at least one of the refractive index, thickness and wavelength of the optical waveguide layer 20 in each waveguide element 10.

[0081] As described above, if waveguide element 10 is used, then by adjusting the refractive index n of the optical waveguide layer 20... w A change in at least one of the thickness d and wavelength λ can significantly alter the direction of light emission. This allows the emission angle of light emitted from mirror 30 to vary along the direction of waveguide element 10. Such one-dimensional scanning can be achieved by using at least one waveguide element 10.

[0082] To adjust the refractive index of at least a portion of the optical waveguide layer 20, the optical waveguide layer 20 may also contain a liquid crystal material or an electro-optical material. The optical waveguide layer 20 can be sandwiched between a pair of electrodes. By applying a voltage to the pair of electrodes, the refractive index of the optical waveguide layer 20 can be changed.

[0083] To adjust the thickness of the optical waveguide layer 20, at least one actuator can be connected to at least one of the first mirror 30 and the second mirror 40. By changing the distance between the first mirror 30 and the second mirror 40 using at least one actuator, the thickness of the optical waveguide layer 20 can be varied. If the optical waveguide layer 20 is formed of a liquid, its thickness can be easily varied.

[0084] <Principles of Two-Dimensional Scanning>

[0085] In a waveguide array consisting of multiple waveguide elements 10 arranged in one direction, the direction of light emission changes due to interference of light emitted from each waveguide element 10. The direction of light emission can be changed by adjusting the phase of the light supplied to each waveguide element 10. The principle is explained below.

[0086] Figure 3A This is a diagram showing a cross-section of a waveguide array that emits light in a direction perpendicular to the exit surface of the waveguide array. Figure 3A The diagram also records the phase shift of the light propagating in each waveguide element 10. Here, the phase shift is a value based on the phase of the light propagating in the waveguide element 10 at the left end. The waveguide array of this embodiment includes a plurality of waveguide elements 10 arranged at equal intervals. Figure 3A In the diagram, dashed arcs represent the wavefronts of light emitted from each waveguide element 10. Solid lines represent the wavefronts formed by light interference. Closed solid curves represent the intensity distribution of the interfering light. The interfering light includes the central main lobe and its two side lobes. The main lobe corresponds to the 0th order diffraction. Although in Figure 3A Although not explicitly stated, the interfering light can also include grating lobes equivalent to higher-order diffracted light. The arrow indicates the direction of the 0th-order diffracted light emitted from the waveguide array. Figure 3A In this example, the phases of the light propagating in the optical waveguide layers 20 of each waveguide element 10 are all the same. In this case, the light is emitted in a direction (Z direction) that is perpendicular to both the arrangement direction (Y direction) of the waveguide elements 10 and the direction in which the optical waveguide layers 20 extend (X direction).

[0087] Figure 3B This is a diagram showing a cross-section of a waveguide array that emits light in a direction different from the direction perpendicular to the exit surface of the waveguide array. Figure 3B In the example shown, the phase of the light propagating in the optical waveguide layer 20 of the multiple waveguide elements 10 differs by a certain amount (Δφ) in each of the arrangement directions. In this case, the light is emitted in a direction different from the Z direction. By changing this Δφ, the Y-direction component of the light direction can be changed. If the center-to-center distance between two adjacent waveguide elements 10 is p, then the light emission angle α0 is represented by the following equation (2).

[0088] [Formula 2]

[0089]

[0090] exist Figure 2 In the example shown, the direction of light emission is parallel to the XZ plane. That is, α0 = 0°. Figure 3A and Figure 3BIn the example shown, the direction of the light emitted from the optical scanning device 98 is parallel to the YZ plane. That is, θ = 0°. However, typically the direction of the light emitted from the optical scanning device 98 is neither parallel to the XZ plane nor to the YZ plane. That is, θ ≠ 0° and α0 ≠ 0°.

[0091] Figure 4 It is a schematic representation of a waveguide array in three-dimensional space. Figure 4 The thick arrows shown indicate the direction of light emitted from the optical scanning device 98. θ is the angle between the emitted light direction and the YZ plane. θ satisfies equation (1). α0 is the angle between the emitted light direction and the XZ plane. α0 satisfies equation (2).

[0092] Phase control of light introduced into the waveguide array

[0093] To control the phase of the light emitted from each waveguide element 10, a phase shifter that changes the phase of the light can be provided, for example, at the front end where the light is introduced into the waveguide element 10. The optical scanning device 98 in this embodiment includes multiple phase shifters connected to each of the multiple waveguide elements 10, and a second adjustment element that adjusts the phase of the light propagating in each phase shifter. Each phase shifter includes a waveguide directly connected to or via another waveguide of the optical waveguide layer 20 in a corresponding one of the multiple waveguide elements 10. The second adjustment element changes the direction (i.e., the third direction D3) of the light emitted from the multiple waveguide elements 10 by changing the phase difference of the light propagating from the multiple phase shifters to the multiple waveguide elements 10. In the following description, similar to the waveguide array, the multiple phase shifters arranged together may be referred to as a "phase shifter array".

[0094] Figure 5 This is a schematic diagram of the waveguide array 10A and the phase shifter array 80A viewed from the normal direction (Z direction) of the light exit surface. Figure 5 In the example shown, all phase shifters 80 have the same propagation characteristics, and all waveguide elements 10 have the same propagation characteristics. Each phase shifter 80 and each waveguide element 10 can have the same length, or the lengths can be different. When the lengths of each phase shifter 80 are equal, for example, the phase shift amount can be adjusted by the driving voltage. Furthermore, by constructing a structure in which the lengths of each phase shifter 80 change in equal steps, equal-step phase shifts can be applied with the same driving voltage. Furthermore, the optical scanning device 98 also includes a beam splitter 90 that branches the light to supply the multiple phase shifters 80, a first driving circuit 110 that drives each waveguide element 10, and a second driving circuit 120 that drives each phase shifter 80. Figure 5The straight arrows in the diagram represent light input. Two-dimensional scanning can be achieved by independently controlling the first drive circuit 110 and the second drive circuit 120, which are respectively configured. In this example, the first drive circuit 110 functions as a component of the first adjustment element, and the second drive circuit 120 functions as a component of the second adjustment element.

[0095] The first driving circuit 110 changes the angle of light emitted from the optical waveguide layer 20 by changing at least one of the refractive index and thickness of the optical waveguide layer 20 in each waveguide element 10. The second driving circuit 120 changes the phase of light propagating inside the waveguide by changing the refractive index of the waveguide in each phase shifter 80. The beam splitter 90 can be constructed from a waveguide in which light propagates through total internal reflection, or from a reflective waveguide similar to the waveguide element 10.

[0096] Alternatively, the phases of the individual beams branched by the beam splitter 90 can be controlled before guiding each beam to the phase shifter 80. In this phase control, for example, a passive phase control structure can be used by adjusting the length of the waveguide up to the phase shifter 80. Alternatively, a phase shifter with the same function as the phase shifter 80, controllable by an electrical signal, can be used. In this way, the phase can be adjusted before being guided to the phase shifter 80 to supply equal-phase light to all phase shifters 80. This adjustment simplifies the control of each phase shifter 80 by the second drive circuit 120.

[0097] Optical devices having the same structure as the optical scanning device 98 described above can also be used as optical receiving devices. Details regarding the operating principle and method of the optical device are disclosed in U.S. Patent Application Publication No. 2018 / 0224709. The entire disclosure of that document is incorporated herein by reference.

[0098] The aforementioned optical device 98 includes multiple waveguide elements 10. The inventors of this disclosure further investigated the structure of a simpler optical device for performing two-dimensional scanning and found that multiple waveguide elements 10 are not necessarily required in two-dimensional scanning. As described below, the optical device of this disclosure includes multiple optical waveguides and planar optical waveguides directly or indirectly connected to the multiple optical waveguides. The planar optical waveguide includes an optical waveguide layer 20 and mirrors 30 and 40. Even with such a simple structure, two-dimensional scanning can be achieved.

[0099] The optical scanning device and optical receiving device of the present disclosure can be used as antennas for optical detection systems such as LiDAR (Light Detection and Ranging) systems. Compared with radar systems that use radio waves such as millimeter waves, LiDAR systems can detect the distance distribution of objects with higher resolution because they use short-wavelength electromagnetic waves (visible light, infrared, or ultraviolet light). Such LiDAR systems can be installed, for example, in automobiles and UAVs (Unmanned Aerial Vehicles). i Mobile vehicles such as drones (alvees) and AGVs (Automated Guided Vehicles) can be used as one of the collision avoidance technologies. In this specification, optical scanning devices and optical receiving devices are sometimes collectively referred to as "optical devices." Furthermore, devices used in optical scanning devices or optical receiving devices are also sometimes referred to as "optical devices."

[0100] The optical device of the first item comprises: a plurality of optical waveguides extending in a first direction and arranged in a second direction intersecting the first direction; and a planar optical waveguide directly or indirectly connected to the plurality of optical waveguides. The plurality of optical waveguides propagate light along the first direction. The planar optical waveguide comprises: a first mirror and a second mirror facing each other and extending along the first direction and the second direction; and an optical waveguide layer located between the first mirror and the second mirror.

[0101] In this optical device, light-based scanning can be achieved with a relatively simple structure by interfering light propagating in multiple optical waveguides within the optical waveguide layer of a planar optical waveguide.

[0102] The optical device of the second item further includes, in the optical device of the first item, at least one of an electrode that changes the refractive index of the optical waveguide layer and an actuator that changes the thickness of the optical waveguide layer.

[0103] In this optical device, by changing at least one of the refractive index and thickness of the optical waveguide layer, the direction of light emitted from the optical waveguide layer through the first mirror and / or the second mirror can be changed.

[0104] The optical device of the third item, in the optical device of the first or second item, further includes other optical waveguides disposed between the aforementioned plurality of optical waveguides and the aforementioned planar optical waveguides. The aforementioned plurality of optical waveguides branch off from the aforementioned other optical waveguides.

[0105] In this optical device, light that propagates in multiple optical waveguides and interferes in other optical waveguides can be propagated to a planar optical waveguide.

[0106] In the optical device of the fourth item, in the optical device of the first or second item, the optical waveguide layer of the aforementioned planar optical waveguide includes an optical coupling portion comprising the front end portions of the aforementioned plurality of optical waveguides, and an optical waveguide portion adjacent to the optical coupling portion. The front end portions of the aforementioned plurality of optical waveguides include one or more gratings.

[0107] In this optical device, light propagating in multiple optical waveguides can be effectively propagated to the optical waveguide layer of the planar optical waveguide.

[0108] In the optical device of item 5, which relates to the optical device of item 3, the optical waveguide layer of the aforementioned planar optical waveguide includes an optical coupling portion comprising the front end portion of the aforementioned other optical waveguide, and an optical waveguide portion adjacent to the optical coupling portion. The front end portion of the aforementioned other optical waveguide includes one or more gratings.

[0109] In this optical device, light that propagates in multiple optical waveguides and interferes in other optical waveguides can be effectively propagated to the optical waveguide layer of the planar optical waveguide.

[0110] In the optical device of item 6, in the optical device of item 4 or 5, the refractive index and / or thickness of the optical coupling portion in the optical waveguide layer and the refractive index and / or thickness of the optical waveguide portion can be adjusted individually.

[0111] In this optical device, the direction of light emitted from the first mirror and / or the second mirror can be changed while maintaining effective optical coupling from multiple optical waveguides 11 to the optical waveguide layer 20.

[0112] In the optical device relating to item 7, in any of the optical devices relating to items 1 to 6, the plurality of optical waveguides are arranged at equal intervals in the second direction.

[0113] In this optical device, by changing the phase of light propagating in multiple optical waveguides by a certain amount along the second direction, the direction of light emitted from the first mirror and / or the second mirror can be changed.

[0114] In the optical device relating to item 8, in any of items 1 to 6, the plurality of optical waveguides include a first optical waveguide, a second optical waveguide, and a third optical waveguide arranged sequentially in the second direction. The center-to-center distance between the first optical waveguide and the second optical waveguide is different from the center-to-center distance between the second optical waveguide and the third optical waveguide.

[0115] In this optical device, the generation of side lobes and grating lobes caused by interference of light passing through the optical waveguide layer can be suppressed.

[0116] The optical device of item 9, in any one of items 1 to 8, further includes a phase shifter that changes the phase difference of the light propagating in each of the plurality of optical waveguides.

[0117] In this optical device, the direction of light emitted from the first mirror and / or the second mirror can be changed by a phase shifter.

[0118] The optical detection system of item 10 comprises: an optical device according to any one of items 1 to 9; a photodetector for detecting light emitted from the optical device and reflected from an object; and a signal processing circuit for generating distance distribution data based on the output of the photodetector.

[0119] This optical detection system can generate distance measurement images of objects.

[0120] In this disclosure, all or part of a circuit, unit, device, component, or section, or all or part of a functional block in a block diagram, may be implemented by one or more electronic circuits, including semiconductor devices, semiconductor integrated circuits (ICs), or LSIs (large scale integration). An LSI or IC can be integrated onto a single chip or a combination of multiple chips. For example, functional blocks other than storage elements can be integrated onto a single chip. It is referred to herein as an LSI or IC, but the terminology varies depending on the degree of integration; it may also be called a system LSI, VLSI (very large scale integration), or ULSI (ultra large scale integration). Field Programmable Gate Arrays (FPGAs) that can be programmed after the LSI is manufactured, or reconfigurable logic devices capable of reconfiguring the bonding relationships within the LSI or setting the circuit partitioning within the LSI, can also be used for the same purpose.

[0121] Furthermore, all or part of the functions or operations of a circuit, unit, device, component, or part can be executed through software processing. In this case, the software is recorded on one or more non-transitory recording media such as ROM, optical disk, or hard disk drive. When the software is executed by a processor, the functions determined by the software are executed by the processor and peripheral devices. The system or device may also include one or more non-transitory recording media containing the software, a processor, and necessary hardware devices, such as interfaces.

[0122] In this disclosure, "light" refers to electromagnetic waves that include not only visible light (wavelength from about 400 nm to about 700 nm), but also ultraviolet light (wavelength from about 10 nm to about 400 nm) and infrared light (wavelength from about 700 nm to about 1 mm).

[0123] The following describes more specific embodiments of this disclosure. However, sometimes the necessary detailed descriptions are omitted. For example, detailed descriptions of already known matters and repetitive descriptions of substantially the same structures are sometimes omitted. This is to avoid unnecessarily lengthy descriptions in order to facilitate understanding by those skilled in the art. Furthermore, the inventors of this disclosure have provided the drawings and the following description to enable those skilled in the art to fully understand this disclosure, but do not intend to limit the subject matter of the claims by these. In the following description, the same or similar structural elements are given the same reference numerals.

[0124] (Implementation Method 1)

[0125] Before describing Embodiment 1 of this disclosure, refer to Figures 6A to 8C Explain the comparative examples.

[0126] Figure 6A This is a schematic perspective view of the optical device 99, a comparative example. Figure 6A In this context, the structures are represented as separate left and right sides, but these structures are typically in contact. The comparative example optical device 99, as described later, corresponds to a configuration with multiple waveguide elements 10 arranged together. Figure 1 The structure.

[0127] exist Figure 6A In the example shown, the comparative example optical device 99 includes a plurality of optical waveguides 11 arranged in the Y direction, mirrors 30 and 40, and an optical waveguide layer 20 located between these mirrors. The optical waveguide layer 20 includes a first component 24a and a plurality of second components 24b extending in the X direction and arranged in the Y direction. The two sides and the upper surface of the second components 24b contact the first component 24a. The lower surface of the second components 24b contacts the mirrors 40. The plurality of optical waveguides 11 are disposed on a substrate 41. The refractive index of the optical waveguide 11 is greater than the refractive index of its periphery. This periphery includes a medium in contact with the two sides and the upper surface of the optical waveguide 11 and a substrate 41 in contact with the lower surface of the optical waveguide 11. The optical waveguides 11 propagate light in the X direction by total internal reflection. The plurality of optical waveguides 11 may also branch from other optical waveguides.

[0128] Figure 6B It is a schematic representation Figure 6A A three-dimensional view of the structure on the right. However, the orientation of the configuration is different. For example... Figure 6BAs shown, between mirrors 30 and 40, there are multiple waveguide portions 26a and multiple non-waveguide portions 26b arranged alternately in the Y direction. The multiple waveguide portions 26a and multiple non-waveguide portions 26b extend along the X direction. A waveguide portion 26a is located between two non-waveguide portions 26b. The waveguide portion 26a includes a first component 24a. The non-waveguide portion 26b includes a first component 24a and a second component 24b. The first component 24a exists in both the waveguide portion 26a and the non-waveguide portion 26b. In the optical device 99 of the comparative example, the refractive index n1 of the first component 24a is higher than the refractive index n2 of the second component 24b. In this case, the refractive index of the waveguide portion 26a is higher than the average refractive index of the non-waveguide portion 26b. Therefore, light propagates in the waveguide portion 26a along the X direction through total internal reflection in the Y direction. The first component 24a can be formed, for example, of a liquid crystal material or an electro-optical material, and the second component 24b can be formed, for example, of a dielectric material such as glass. The refractive index of the liquid crystal material can be changed by applying an external voltage.

[0129] exist Figure 6B In the example shown, the structure having waveguide portion 26a, the portion directly above waveguide portion 26a in mirror 30, and the portion directly below waveguide portion 26a in mirror 40 is equivalent to the waveguide element 10 described above. That is, multiple waveguide elements 10 are arranged in the Y direction.

[0130] In the comparative example optical device 99, the end face of the optical waveguide 11 parallel to the YZ plane is connected to the end face of the waveguide portion 26a of the optical waveguide layer 20 parallel to the YZ plane.

[0131] Figure 7 It is a schematic representation of from Figure 6A A diagram showing the light emitted from the optical device 99. However, mirrors 30 and 40 are omitted for simplicity. Furthermore, the multiple optical waveguides 11 and the optical waveguide layer 20 are shown in a planar view, while the light emitted outwards is shown in a three-dimensional view. The shades of black and white represent the intensity of the light. Black represents high intensity, and white represents low intensity.

[0132] exist Figure 7 In the example shown, light propagating along the X-direction from multiple optical waveguides 11 in multiple waveguide sections 26a of the optical waveguide layer 20 is emitted outward from the mirror 30. As the light is emitted outward, the intensity of the light representing the waveguide section 26a decreases along the +X direction. The light emitted outward from the multiple waveguide sections 26a via the mirror 30 is as follows... Figure 3A and Figure 3B As shown, interference occurs, forming a beam of light that propagates in a specific direction. This beam of light... Figure 7 As shown, it may vary in the direction indicated by the double arrows.

[0133] Figures 8A to 8C These are diagrams illustrating examples of the intensity distribution of light propagating between mirrors 30 and 40 and examples of the intensity distribution of light emitted into the distance, respectively. The left diagram of each figure shows the intensity distribution of light propagating between mirrors 30 and 40 in the XY plane. The left side of the left diagram corresponds to the connection between the multiple optical waveguides 11 and the optical waveguide layer 20. The right diagram of each figure shows the intensity distribution of light emitted into the distance. Synopsys' ModePROP was used in the calculation of the light intensity distribution shown in the left and right diagrams. The far-field pattern of the intensity distribution of light emitted into the distance was calculated by performing a Fourier transform on the light intensity distribution on the light-emitting surface of mirror 30. Figures 8A to 8C In the example shown, the spacing between mirrors 30 and 40 is 2.13 μm. The width of the second component 24b is 2 μm and the height is 0.9 μm. The width of the waveguide portion 26a is 3 μm, and the width of the non-waveguide portion 26b is equal to the width of the second component 24b.

[0134] exist Figure 8A In the example shown, the refractive index of component 24a is n1 = 1.68, and the refractive index of component 24b is n2 = 1.46. For example... Figure 8A As shown in the left figure, light propagates along the X direction in waveguide section 26a. The phase of light propagating in all waveguide sections 26a is equal. Figure 8A As shown in the right figure, the far-field diagram represents the 0th order diffraction beam at the center and the ±1st order diffraction beams on either side of it. Figure 8A In the example shown in the right figure, the exit angle θ of the light emitted from mirror 30 is between 45 and 50 degrees. This exit angle θ is relatively large. The exit angle α0 of the 0th order diffracted light is 0 degrees.

[0135] exist Figure 8B In the example shown, with Figure 8A The example shown is different; the phase of the light propagating in the multiple optical waveguides 11 is shifted by Δφ = π along the +Y direction. Figure 8B The left image and Figure 8A The left image is roughly the same. Figure 8B In the right image, with Figure 8A Compared to the right image, the far-field image changes in the direction of increasing emission angle α0. This means that due to the different phases of the input light, the Y-direction component of the light emitted from mirror 30 changes. Figure 8B In the example shown in the right figure, the exit angle α0 of the 0th order diffracted light is 6 degrees. The ±1st order diffracted light also changes in the same way. Furthermore, new higher order diffracted lights appear.

[0136] exist Figure 8C In the example shown, with Figure 8BThe example shown is different; the refractive index of component 24a is n1 = 1.52. Figure 8C The left image and Figure 8A and Figure 8B Unlike the left image, the light intensity decreases along the +X direction. Figure 8C In the right image, with Figure 8B Compared to the right image, the far-field image changes in the direction of decreasing emission angle θ. This means that the X-direction component of the light emitted from mirror 30 changes due to the change in refractive index of the optical waveguide layer 20. Figure 8C In the example shown in the right figure, the emission angle θ of the light emitted from mirror 30 is between 15 and 20 degrees. This emission angle θ is relatively small.

[0137] Next, refer to Figures 9A to 11C The optical device according to the present disclosure will be described below. The optical device according to this embodiment can achieve two-dimensional scanning with a simpler structure than the optical device 99 of the comparative example. Hereinafter, descriptions identical to those in the comparative example will be omitted.

[0138] Figure 9A This is a schematic diagram illustrating the optical device 100 according to Embodiment 1 of this disclosure. Figure 9A In the example shown, the optical device 100 includes a plurality of optical waveguides 11 and a single planar optical waveguide 50 directly connected to the plurality of optical waveguides 11. The planar optical waveguide 50 includes mirrors 30 and 40 extending along the X and Y directions and an optical waveguide layer 20 located between these mirrors. The optical device 100 of Embodiment 1 of this disclosure differs from the optical device 99 of the comparative example in that the plurality of second components 24b arranged in the Y direction are not present in the optical waveguide layer 20.

[0139] Figure 9B It is a schematic representation Figure 9A A three-dimensional view of the planar optical waveguide 50. However, the orientation of the configuration is different. For example... Figure 9B As shown, the optical waveguide layer 20 is uniform in any direction parallel to the XY plane. In one example, the optical waveguide layer 20 may contain a liquid crystal material or an electro-optical material. The refractive index of the liquid crystal material or electro-optical material may be varied by applying an external voltage. In another example, the optical waveguide layer 20 may contain a deformable liquid or gas. The thickness of the optical waveguide layer 20 can be varied by changing the spacing between mirrors 30 and 40. By varying the refractive index and / or thickness of the optical waveguide layer 20, the component parallel to the X-direction in the direction of light propagating in the optical waveguide layer 20 and emitted via mirror 30 can be varied. The first driving circuit 110 described above can drive the planar optical waveguide 50 to change the refractive index and / or thickness of the optical waveguide layer 20. The specific structure for driving the planar optical waveguide 50 will be described later.

[0140] A phase shifter array 80A can be connected to multiple optical waveguides 11. The phase shifter array 80A allows the phase of light propagating in the multiple optical waveguides 11 to be shifted by a certain amount along the Y direction. As a result, the component of the light propagating in the optical waveguide layer 20 and exiting from the mirror 30 that is parallel to the Y direction can be changed. The multiple optical waveguides 11 themselves can also function as the phase shifter array 80A. The second driving circuit 120 described above can drive the phase shifter array 80A to perform the aforementioned phase shifting.

[0141] Figure 10 It is a schematic representation of from Figure 9A A diagram showing the situation of light emitted from the optical device 100. Light input from multiple optical waveguides 11 and propagating within the optical waveguide layer 20... Figure 7 The example shown differs; interference within the optical waveguide layer 20 forms beam 22b. Regarding dashed curves, solid lines, and closed solid curves, see reference... Figure 3A and Figure 3B As explained, these beams 22b are emitted outward from mirror 30 and propagate in a specific direction.

[0142] Figures 11A to 11C These are diagrams illustrating examples of the intensity distribution of light propagating between mirrors 30 and 40 and examples of the intensity distribution of light emitted into the distance, according to Embodiment 1. The left and right diagrams and the calculation methods are as described above. Figures 11A to 11C In the example shown, the thickness of the optical waveguide layer 20 is 2.13 μm.

[0143] exist Figure 11A In the example shown, the refractive index of the optical waveguide layer 20 is n1 = 1.68. For example... Figure 11A As shown in the left figure, it is difficult to form a beam along the +X direction within the optical waveguide layer 20. Near Y=0, which corresponds to the center of the optical waveguide 11 (corresponding to the very center of the main waveguide), the beam intensity increases. Side lobes are formed around the main lobe. The beam propagates along the X direction within the optical waveguide layer 20. Figure 11A The far-field plot shown on the right is... Figure 8A The field diagram shown in the right figure is similar. However, as... Figure 11A As shown in the right figure, the intensity of ±1 order diffracted light is low.

[0144] exist Figure 11B In the example shown, with Figure 11A The example shown is different; the phase of the light propagating in multiple optical waveguides is shifted by π along the +Y direction. Figure 11B In the left image, with Figure 11A Compared to the left image, the beam has higher intensity in two directions. One direction includes components in the +X and +Y directions, and the other direction includes components in the +X and -Y directions. For example... Figure 11BAs shown in the right figure, the far-field pattern also exhibits high intensity in both directions. This means that the Y-direction component of the light emitted from mirror 30 changes due to the different phases of the input light. Figure 11B The far-field plot shown on the right is... Figure 8B The field diagram shown on the right is similar.

[0145] exist Figure 11C In the example shown, with Figure 11B The example shown is different; the refractive index of the optical waveguide layer 20 is n1 = 1.52. Figure 11C The left image and Figure 11B Compared to the left image, the beam has shifted in the -X direction. Figure 11C In the right image, with Figure 11B Compared to the right image, the far-field image shows a change in the direction of decreasing emission angle θ. Figure 11C The far-field plot shown on the right is... Figure 8C The field diagram shown on the right is similar.

[0146] As described above, in the optical device 100 of Embodiment 1, two-dimensional scanning can obviously also be realized, just like in the optical device 99 of the comparative example. According to the optical device 100 of Embodiment 1, since multiple waveguide elements 10 are not required, it can be easily manufactured.

[0147] Next, the crosstalk that occurs between light propagating in the multiple optical waveguides 11 is explained. Figure 9A In the example shown, multiple optical waveguides 11 are arranged periodically at equal intervals along the Y direction. If light propagates within the optical waveguides 11 along the X direction, evanescent light emanates from the optical waveguides 11 in the Y direction. If the center-to-center distance between two adjacent optical waveguides is short, the evanescent light emanating from the optical waveguides may transfer to the adjacent optical waveguides. As a result, light propagating in the multiple optical waveguides 11 may enter the optical waveguide layer 20 without phase difference.

[0148] Figure 12 This is a graph showing the periodic dependence of the crosstalk rate occurring between multiple optical waveguides 11 with a length of 100 μm. The refractive index of the optical waveguide 11 is 2.0, and the refractive index of the substrate 41 is 1.46. The width of the optical waveguide 11 is 600 nm, and the height is 300 nm. Figure 12 As shown, if the period between multiple optical waveguides 11 increases, the crosstalk rate decreases while oscillating. If the period is greater than 1.3 μm, the crosstalk rate can be suppressed to below a few percentage points.

[0149] Next, refer to Figure 13A and Figure 13B The first and second modifications of the optical device 100 according to Embodiment 1 will be described. There are cases where descriptions that are repeated in Embodiment 1 are omitted.

[0150] Figure 13A This diagram schematically illustrates a first modification of the optical device 100 according to Embodiment 1. In this first modification, unlike Embodiment 1, the plurality of optical waveguides 11 are not arranged at equal intervals along the Y direction. Figure 13A In the example shown, the five optical waveguides 11 are named "First Optical Waveguide 111" to "Fifth Optical Waveguide 115" in the +Y direction. The first center-to-center distance d1 between the first optical waveguide 111 and the second optical waveguide 112 is shorter than the second center-to-center distance d2 between the second optical waveguide 112 and the third optical waveguide 113. The third center-to-center distance d3 between the third optical waveguide 113 and the fourth optical waveguide 114 is equal to the second center-to-center distance d2 between the second optical waveguide 112 and the third optical waveguide 113. The fourth center-to-center distance d4 between the fourth optical waveguide 114 and the fifth optical waveguide 115 is equal to the first center-to-center distance d1 between the first optical waveguide 111 and the second optical waveguide 112. That is, d2 = d3 > d1 = d4. It is not necessary for all the optical waveguides 11 to have equal spacing; some may have different spacing. By appropriately designing the first intercenter distance d1 to the fourth intercenter distance d4, the generation of side lobes and grating lobes of beam 22b can be suppressed. As a result, the generation of side lobes and grating lobes of light emitted from mirror 30 can be suppressed.

[0151] Figure 13B This diagram schematically illustrates a second modification of the optical device 100 according to Embodiment 1. In this second modification, unlike Embodiment 1, a plurality of optical waveguides 11, an optical waveguide layer 20, and one or more elastic spacers 72 are provided on the mirror 40. The one or more elastic spacers 72 are located around the front ends of the plurality of optical waveguides 11 and around the optical waveguide layer 20. The shape of the one or more elastic spacers 72 may also be a continuous curve. The dimension of the elastic spacer 72 in the Z direction is larger than the dimension of the optical waveguide 11 in the Z direction, and also larger than the dimension of the optical waveguide layer 20 in the Z direction. The optical device 100 of the second modification is manufactured by attaching the mirrors 30 and 40 such that at least a portion of the elastic spacers 72 and the optical waveguide layer 20 are located between these mirrors.

[0152] In the absence of multiple elastic spacers 72, during attachment, mirror 30 may initially come into contact with a portion of the constituent parts disposed on mirror 40. In this case, mirror 30 may tilt relative to mirror 40, using the contact portion as a fulcrum. As a result, the intensity of light emitted from mirror 30 may decrease.

[0153] In contrast, when multiple elastic spacers 72 are present, mirror 30 comes into contact with the elastic spacers 72 first. Because the elastic spacers 72 are compressed, mirror 40 and mirror 30 can fit together, resulting in a uniform spacing between mirrors 30 and 40. As a result, the decrease in the intensity of light emitted from mirror 30 can be suppressed.

[0154] (Implementation Method 2)

[0155] Next, refer to Figures 14A to 16B This section describes an example of an optical device according to Embodiment 2 of this disclosure.

[0156] Figure 14A and Figure 14B These are schematic cross-sectional views in the XZ and XY planes, respectively, illustrating an example of the optical device 100 of Embodiment 2. Figure 14A and Figure 14B In the example shown, there are other planar optical waveguides 12 between the multiple optical waveguides 11 and the planar optical waveguide 50. In other words, the planar optical waveguide 50 is indirectly connected to the multiple optical waveguides 11 via the planar optical waveguides 12. The multiple optical waveguides 11 branch from the planar optical waveguides 12.

[0157] Mirror 40 is also located below the plurality of optical waveguides 11 and planar optical waveguides 12. The plurality of optical waveguides 11 and planar optical waveguides 12 are disposed on mirror 40 via cladding layer 51. The refractive index of the optical waveguides 11 is higher than that of cladding layer 51. The refractive index of the planar optical waveguides 12 is higher than that of cladding layer 51. The plurality of optical waveguides 11 are arranged along the Y direction. Cladding layer 51 has a structure parallel to the XY plane. The portion of cladding layer 51 that does not have the plurality of optical waveguides 11 and planar optical waveguides 12 on its upper side may also be removed. The optical waveguide layer 20 and mirror 30 located on the upper side of the planar optical waveguides 12 are not necessarily required.

[0158] The optical waveguide layer 20 includes an optical coupling portion 20c comprising a front end portion of a planar optical waveguide 12 and an optical waveguide portion 20g adjacent to the optical coupling portion 20c. The front end portion of the planar optical waveguide 12 is located between mirrors 30 and 40. Light propagating from the plurality of optical waveguides 11 in the planar optical waveguide 12 is coupled to the optical waveguide portion 20g via the optical coupling portion 20c.

[0159] A grating 15 is provided at the front end of the planar optical waveguide 12. The grating 15 includes a plurality of recesses and / or protrusions of 4 to 64. By appropriately designing the period of the grating 15, the difference between the propagation constant of light propagating in the planar optical waveguide 12 and the propagation constant of light propagating in the optical waveguide layer 20 can be compensated. Through this compensation, light can be effectively coupled from the planar optical waveguide 12 to the optical waveguide layer 20.

[0160] Figure 15 It is a schematic representation of from Figure 14A and Figure 14B A diagram showing the beam emitted from the optical device 100. Light propagating in the X direction in multiple optical waveguides 11 interferes within a planar optical waveguide 12 to form a beam 22b. The beam 22b is emitted outward from the optical waveguide portion 20g of the optical waveguide layer 20 via a mirror 30 and propagates in a specific direction.

[0161] Figure 16A and Figure 16B These are graphs showing the intensity distribution of light propagating between mirrors 30 and 40 in the XY and XZ planes, respectively. The calculation method is as described above. Figure 16A and Figure 16B In the example shown, the refractive index of optical waveguide 11 is 2.115, its width is 600 nm, it has 4 waves, and its period is 1.8 μm. The refractive index of cladding layer 51 is 1.46. The refractive index of planar optical waveguide 12 is 2.115. The refractive index of optical waveguide layer 20 is 1.61, and its thickness is 2.13 μm. The phase of light propagating in all the multiple optical waveguides 11 is equal.

[0162] like Figure 16A As shown, a light beam is formed within the planar optical waveguide 12. Figure 16B As shown, the light beam formed in the planar optical waveguide 12 propagates within the optical waveguide portion 20g via the grating 15.

[0163] exist Figure 14A In the example shown, the refractive index and / or thickness of the optical coupling portion 20c and the refractive index and / or thickness of the optical waveguide portion 20g in the optical waveguide layer 20 can also be adjusted individually. By adjusting them individually, the direction of light emitted from the mirror 30 can be changed while maintaining effective optical coupling from the optical waveguide 11 to the optical waveguide layer 20.

[0164] Instead of embodiment 2, in embodiment 1, the optical waveguide layer 20 of the planar optical waveguide 50 may also include an optical coupling portion comprising the front end portions of a plurality of optical waveguides 11 and an optical waveguide portion adjacent to the optical coupling portion. The front end portions of the plurality of optical waveguides 11 may include one or more gratings. With this structure, light can be effectively coupled from the plurality of optical waveguides 11 to the optical waveguide layer 20.

[0165] The first and second variations of Embodiment 1 can also be applied to Embodiment 2.

[0166] (Structure used to drive planar optical waveguide 50)

[0167] Next, refer to Figure 17A and Figure 17B This describes the structure used to drive the planar optical waveguide 50.

[0168] Figure 17A This is a schematic diagram illustrating the first example of driving a planar optical waveguide 50. Figure 17AIn the example shown, the planar optical waveguide 50 includes a first electrode 62a disposed between the optical waveguide layer 20 and the mirror 30, and a second electrode 62b disposed between the optical waveguide layer 20 and the mirror 40. The first electrode 62a may be, for example, a transparent electrode. Light propagating within the optical waveguide layer 20 is emitted to the outside via the first electrode 62a and the mirror 30. The second electrode 62b may be, for example, an electrode formed of a transparent electrode or metal. The optical waveguide layer 20 may, for example, contain a liquid crystal material or an electro-optical material. The optical waveguide layer 20 is located between a pair of electrodes including the first electrode 62a and the second electrode 62b. The first driving circuit described above applies a voltage to the pair of electrodes, causing a change in the refractive index of the optical waveguide layer 20.

[0169] Figure 17B This is a schematic diagram illustrating the second example of a planar optical waveguide 50. Figure 17B In the example shown, the planar optical waveguide 50 also includes a pair of actuators 70 supporting the mirror 30. The pair of actuators 70 may also support the mirror 40 instead of the mirror 30, or support both the mirror 30 and the mirror 40. The optical waveguide layer 20 may, for example, contain a deformable liquid or gas. The pair of actuators 70 may utilize, for example, electrostatic force, electromagnetic induction, piezoelectric materials, shape memory alloys, or heat. The pair of actuators 70 change the thickness of the optical waveguide layer 20 by varying the spacing between the mirrors 30 and 40. The first driving circuit described above applies a voltage to, for example, the pair of actuators 70 containing a piezoelectric material, causing the thickness of the optical waveguide layer 20 to change.

[0170] By varying the refractive index and / or thickness of the optical waveguide layer 20 as described above, the component of the light emitted from the mirror 30 that is parallel to the X-direction can be changed.

[0171] (Application Example)

[0172] Figure 18 This diagram illustrates an example of the structure of an optical scanning device 100 that integrates components such as a planar optical waveguide 50, multiple optical waveguides 11, a beam splitter 90, a phase shifter array 80A, and a light source 130 on a circuit board (e.g., a chip). The light source 130 can be, for example, a light-emitting element such as a semiconductor laser. In this example, the light source 130 emits light of a single wavelength λ in free space. The beam splitter 90 branches the light from the light source 130 and directs it into the waveguides of the multiple phase shifters. Figure 18 In the example shown, electrode 62A and multiple electrodes 62B are provided on the chip. For the planar optical waveguide 50, a control signal is supplied from electrode 62A. For the multiple phase shifters 80 in the phase shifter array 80A, control signals are transmitted from the multiple electrodes 62B respectively. Electrode 62A and the multiple electrodes 62B can be connected to a control circuit (not shown) that generates the aforementioned control signals. The control circuit can be set in... Figure 18 The chip shown can also be placed on other chips in the optical scanning device 100.

[0173] like Figure 18 As shown, by integrating all components onto a single chip, large-area optical scanning can be achieved using a small device. For example, all components can be integrated onto a chip of approximately 2mm × 1mm.

[0174] Figure 19 This is a schematic diagram illustrating a two-dimensional scan performed by irradiating a laser beam or similar light source from an optical scanning device 100 into a distant location. The two-dimensional scan is performed by moving the beam point 310 in both horizontal and vertical directions. For example, by combining it with the well-known Time of Flight (TOF) method, a two-dimensional ranging image can be obtained. The TOF method calculates the time of flight of light and determines the distance by irradiating a laser and observing the reflected light from an object.

[0175] Figure 20 This is a block diagram illustrating the structure of a LiDAR system 300, an example of a light detection system capable of generating such a ranging image. The LiDAR system 300 includes a light scanning device 100, a light detector 400, a signal processing circuit 600, and a control circuit 500. The light detector 400 detects light emitted from the light scanning device 100 and reflected from an object. The light detector 400 may be, for example, an image sensor sensitive to the wavelength λ of light emitted from the light scanning device 100, or a light detector including a light-receiving element such as a photodiode. The light detector 400 outputs an electrical signal corresponding to the amount of light received. The signal processing circuit 600 calculates the distance to the object based on the electrical signal output from the light detector 400, generating distance distribution data. The distance distribution data is data representing a two-dimensional distribution of distances (i.e., a ranging image). The control circuit 500 is a processor that controls the light scanning device 100, the light detector 400, and the signal processing circuit 600. The control circuit 500 controls the timing of the beam irradiated from the light scanning device 100, as well as the timing of the exposure and signal readout of the photodetector 400, and instructs the signal processing circuit 600 to generate a ranging image.

[0176] In 2D scanning, the frame rate for acquiring ranging images can be selected from, for example, 60fps, 50fps, 30fps, 25fps, 24fps, etc., which are commonly used in motion imaging. Furthermore, considering applications in automotive systems, a higher frame rate results in a higher frequency of acquiring ranging images, leading to more accurate obstacle detection. For example, when traveling at 60 km / h, at a frame rate of 60fps, an image can be acquired whenever the vehicle moves approximately 28cm. At a frame rate of 120fps, an image can be acquired whenever the vehicle moves approximately 14cm. At a frame rate of 180fps, an image can be acquired whenever the vehicle moves approximately 9.3cm.

[0177] The time required to acquire a ranging image depends on the beam scanning speed. For example, to acquire an image with a resolution of 100×100 points at 60 fps, the beam needs to be scanned at a speed of less than 1.67 μs per point. In this case, the control circuit 500 controls the beam emission by the optical scanning device 100 and the signal accumulation and readout by the photodetector 400 at an operating speed of 600 kHz.

[0178] <Application Examples of Light Receiving Devices>

[0179] The optical scanning apparatuses of the above-described embodiments of this disclosure can also be used as optical receiving apparatuses with substantially the same structure. The optical receiving apparatus includes a planar optical waveguide 50 and a plurality of optical waveguides 11, identical to those in the optical scanning apparatus, and a first adjustment element for adjusting the direction of the receivable light. A first mirror 30 transmits light incident from a third direction to the side opposite to the first reflecting surface. An optical waveguide layer 20 allows light transmitted through the first mirror 30 to propagate in a second direction. The first adjustment element can change the direction of the receivable light by changing at least one of the refractive index and thickness of the optical waveguide layer 20, and the wavelength of the light. Furthermore, when the optical receiving apparatus includes a plurality of phase shifters 80 identical to those in the optical scanning apparatus, and a second adjustment element that changes the phase difference of the light output after passing through the plurality of phase shifters 80, the direction of the receivable light can be changed two-dimensionally.

[0180] For example, it can constitute Figure 18 The light source 130 in the illustrated optical scanning device 100 is replaced with an optical receiving device in the receiving circuit. If light of wavelength λ is incident on the planar optical waveguide 50, the light is transmitted to the beam splitter 90 via the phase shifter array 80A, and finally concentrated to a single point before being transmitted to the receiving circuit. The intensity of the light concentrated at this single point can be said to represent the sensitivity of the optical receiving device. The sensitivity of the optical receiving device can be adjusted by adjustment elements respectively assembled to the planar optical waveguide 50 and the phase shifter array 80A.

[0181] The above-described implementation methods can be combined appropriately.

[0182] Industrial availability

[0183] The optical scanning device and optical receiving device of the present disclosure can be used for applications such as lidar systems mounted on vehicles such as automobiles, UAVs, and AGVs.

[0184] Label Explanation

[0185] 10 Waveguide Components

[0186] 10A waveguide array

[0187] 11 Optical waveguide

[0188] 12 Other planar optical waveguides

[0189] 15 gratings

[0190] 20 Optical waveguide layers

[0191] 20c Optical Coupling Section

[0192] 20g optical waveguide section

[0193] 22 Light

[0194] 22b beam

[0195] 24a Part 1

[0196] 24b Part 2

[0197] 26a Waveguide section

[0198] 26b Non-waveguide section

[0199] 30. First Frame

[0200] 40 Mirror 2

[0201] 41 substrate

[0202] 50 Planar optical waveguide

[0203] 51 Coating layer

[0204] Electrodes 62a, 62b, 62A, and 62B

[0205] 70 A pair of actuators

[0206] 72. Elastic spacers

[0207] 80 Phase Shifter

[0208] 80A Phase Shifter Array

[0209] 90 beam splitter

[0210] 99 Optical Equipment

[0211] 100 optical scanning equipment

[0212] Directions 101 and 102

[0213] 110 First Drive Circuit

[0214] 120 Second drive circuit

[0215] 130 light source

[0216] 300 LiDAR system

[0217] 310 beam spots

[0218] 400 photodetector

[0219] 500 control circuit

[0220] 600 Signal Processing Circuit

Claims

1. An optical device, wherein, have: Multiple optical waveguides extend in a first direction and are arranged in a second direction intersecting the first direction; and A planar optical waveguide, directly or indirectly connected to the aforementioned multiple optical waveguides. The aforementioned multiple optical waveguides cause light to propagate along the first direction described above. The aforementioned planar optical waveguide is singular and possesses: The first and second mirrors are positioned opposite each other and extend along the first and second directions mentioned above; and The optical waveguide layer is located between the first mirror and the second mirror.

2. The optical device as described in claim 1, wherein, It also includes at least one of an electrode that changes the refractive index of the optical waveguide layer and an actuator that changes the thickness of the optical waveguide layer.

3. The optical device as described in claim 1 or 2, wherein, It also includes other optical waveguides disposed between the aforementioned plurality of optical waveguides and the aforementioned planar optical waveguides. The aforementioned multiple optical waveguides branch off from the other optical waveguides mentioned above.

4. The optical device as described in claim 1 or 2, wherein, The optical waveguide layer in the aforementioned planar optical waveguide includes an optical coupling portion comprising the front end portions of the plurality of optical waveguides, and an optical waveguide portion adjacent to the optical coupling portion. The aforementioned front-end portion of the multiple optical waveguides includes one or more gratings.

5. The optical device as described in claim 3, wherein, The optical waveguide layer in the aforementioned planar optical waveguide includes an optical coupling portion comprising the front end portion of the other optical waveguides, and an optical waveguide portion adjacent to the optical coupling portion. The aforementioned front-end portion of the other optical waveguides includes one or more gratings.

6. The optical device as described in claim 4 or 5, wherein, The refractive index and / or thickness of the optical coupling portion in the aforementioned optical waveguide layer, as well as the refractive index and / or thickness of the aforementioned optical waveguide portion, can be adjusted individually.

7. The optical device as described in any one of claims 1 to 6, wherein, The aforementioned multiple optical waveguides are arranged at equal intervals in the aforementioned second direction.

8. The optical device as described in any one of claims 1 to 6, wherein, The aforementioned plurality of optical waveguides includes a first optical waveguide, a second optical waveguide, and a third optical waveguide arranged sequentially in the aforementioned second direction. The center-to-center distance between the first optical waveguide and the second optical waveguide is different from the center-to-center distance between the second optical waveguide and the third optical waveguide.

9. The optical device as described in any one of claims 1 to 8, wherein, It also includes a phase shifter that changes the phase difference of the light propagating in each of the plurality of optical waveguides.

10. A light detection system, wherein, have: The optical device according to any one of claims 1 to 9; A light detector that detects light emitted from the aforementioned light device and reflected from an object; and The signal processing circuit generates distance distribution data based on the output of the aforementioned photodetector.

Images