WO2019131029A1

WO2019131029A1 - Optical device

Info

Publication number: WO2019131029A1
Application number: PCT/JP2018/044815
Authority: WO
Inventors: 青児西脇
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2017-12-27
Filing date: 2018-12-06
Publication date: 2019-07-04

Abstract

An optical device according to one embodiment is provided with: a light source for emitting laser light; an optical waveguide element positioned on the light path for the laser light; a first transparent member positioned on the light path and having a bottom surface facing the optical waveguide element and side surfaces having rotational symmetry with respect to the light path; and a control circuit. The optical waveguide element includes: a first grating that includes a plurality of parts with different refractive indices from each other disposed along the radial direction and propagates part of the incident laser light along the radial direction within the optical waveguide element; and a second grating that is disposed outside of the first grating, includes a plurality of parts with different refractive indices from each other disposed along the radial direction, and emits light from the optical waveguide element.

Description

Optical device

The present disclosure relates to an optical device.

Conventionally, in order to determine the position of an object scattered in the field of view, the distance to the object surface can be determined by irradiating the object with light pulses from a light source and measuring the time delay of reflected light from the object for each direction. It is measured. For example, Patent Document 1 discloses an optical phased array using such a technique.

JP, 2017-187649, A

The present disclosure provides a technique for scanning horizontally and / or vertically over an object scattered in a field of view by laser light and selectively receiving or detecting reflected light from the object.

An optical apparatus according to an aspect of the present disclosure includes: a light source for emitting a laser beam; an optical waveguide element located on an optical path of the laser beam; a bottom surface located on the optical path and facing the optical waveguide element; A first transparent member having a side surface that is rotationally symmetric about a virtual axis along the optical path as a central axis, and a control circuit. The optical waveguide element includes a plurality of portions disposed along the radial direction of a virtual circle centered on the point on which the laser beam is incident and having different refractive indices, and a part of the incident laser beam A first grating propagating along the radial direction in the optical waveguide element as propagating light, and an outer side of the first grating are disposed along the radial direction, and the refractive indexes are mutually different. And a second grating for causing a part of the propagated light to be emitted from the optical waveguide element as an emitted light. The emitted light is incident on the first transparent member from the bottom surface or the side surface, and is emitted from the side surface.

The above general aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium. Alternatively, the present invention may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

According to one aspect of the present disclosure, an object scattered in a field of view is scanned horizontally and / or vertically by laser light without using a mechanical structure to selectively receive or reflect light reflected from the object. It can be detected.

FIG. 1A is a perspective view schematically showing the configuration of an optical device and the path of a light beam. FIG. 1B is a cross-sectional view schematically showing the configuration of an optical device and the path of a light beam. FIG. 1C is a perspective view schematically showing the configuration of a light source in the optical device. FIG. 1D is a perspective view schematically showing another form of a cylindrical body in the optical device. FIG. 2A is a diagram showing a vector diagram. FIG. 2B is a diagram showing a vector diagram. FIG. 3A is a perspective view schematically showing the polarization direction of incident light and the state of input in the first embodiment. FIG. 3B is a cross-sectional view schematically showing an input grating coupler. FIG. 3C is a cross-sectional view showing the appearance of light that is coupled in and guided by light intensity. FIG. 3D is a plan view schematically showing an input grating coupler. FIG. 3E is a plan view showing the relationship between the polarization direction and the input propagation direction by light intensity. FIG. 3F is a plan view showing the relationship between the polarization direction and the input propagation direction by light intensity. FIG. 3G is a plan view showing the relationship between the polarization direction and the input propagation direction by light intensity. FIG. 4A is a graph showing the wavelength dependency of the input coupling efficiency of the input grating coupler when there is no reflective layer. FIG. 4B is a cross-sectional view schematically showing the input grating coupler when there is a reflective layer. FIG. 4C is a graph showing the layer thickness dependency of the input coupling efficiency with the reflective layer. FIG. 4D is a graph showing the wavelength dependency of input coupling efficiency when there is a reflective layer. FIG. 5A is a plan view showing the relationship between the polarization direction of incident light and the input propagation direction by light intensity. FIG. 5B is a diagram showing the relationship between the deflection angle φ and the intensity I of the guided light propagating and the relationship between the deflection angle φ of the light energy E included in the deflection angle range from −φ to φ. FIG. 6 is a perspective view schematically showing a configuration example of a polarization rotator. FIG. 7A is a view schematically showing propagation paths of radiation light in the output grating coupler when there is no aberration correction. FIG. 7B is a view schematically showing propagation paths of radiation light in the output grating coupler when there is aberration correction control. FIG. 8A is a view schematically showing that radiation light from the output grating coupler is refracted and emitted at a cylindrical surface. FIG. 8B is a view schematically showing a pattern of a transparent electrode layer for realizing aberration correction. FIG. 9A is a diagram showing the relationship between the deflection angle in the propagation direction and the effective refractive index change amount of guided light for achieving aberration correction. FIG. 9B is a diagram showing the relationship between the thickness of the waveguide layer and the effective refractive index, with the liquid crystal refractive index as a parameter. FIG. 9C is a view schematically showing the arrangement of the buffer layer, the waveguide layer, and the liquid crystal. FIG. 10A is a view for explaining the relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light. FIG. 10B is a diagram for explaining a phase plane generated due to the relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light. FIG. 10C is a view for explaining the relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light. FIG. 10D is a view for explaining a phase plane generated due to the relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light. FIG. 10E is a view schematically showing how the aberration at the time of focusing on the point F ′ is corrected. FIG. 11A is a diagram showing the relationship between the depth of the output grating coupler and the radiation loss coefficient. FIG. 11B is a diagram showing the relationship between the depth of the output grating coupler and the radiation loss coefficient. FIG. 11C is a diagram showing the relationship between the duty and the radiation loss coefficient. FIG. 11D is a view showing the relationship between the duty and the radiation loss coefficient. FIG. 11E is a view showing the relation between the coupling length and the waveguide strength, and the relation between the coupling length and the radiation strength. FIG. 11F is a view showing the relation between the coupling length and the waveguide strength, and the relation between the coupling length and the radiation strength. FIG. 12A is a diagram showing the positional relationship between radiation light from the output grating coupler and a cylindrical body. FIG. 12B is a diagram showing the positional relationship between radiation light from the output grating coupler and a cylindrical body. FIG. 13A is a horizontal sectional view showing the relationship between the radiation from the output grating coupler and the beam width of refracted light from the cylindrical surface. FIG. 13B is a vertical sectional view showing the relationship between the radiation from the output grating coupler and the beam width of the refracted light from the cylindrical surface. FIG. 14A is a view showing the relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light. FIG. 14B is a view showing the relationship of time course of the polarization rotation angle of input light, the voltage applied to the transparent electrode, and the rotation angle in the horizontal direction and the vertical direction. FIG. 14C is a view showing horizontal and vertical scanning by laser light. FIG. 15A is a view showing the relationship of time course of the polarization rotation angle of the input light, the light source wavelength, the voltage applied to the transparent electrode, and the rotation angle in the horizontal direction and the vertical direction. FIG. 15B is a view showing horizontal and vertical scanning of laser light. FIG. 16A is a view showing the relationship of the control signal of the polarization rotator, the polarization angle of light, the output light quantity of the light source, and the time course of the light quantity detected by the light detector. FIG. 16B is a view showing the relationship of the time lapse of the control signal of the polarization rotator, the output light quantity of the light source, and the light quantity detected by the light detector. FIG. 16C is a view showing the relationship of the control signals of the polarization rotator, the output light quantity of the light source, and the time course of the light quantity detected by the light detector. FIG. 17A is a view schematically showing a pattern of a transparent electrode layer. FIG. 17B is a view schematically showing a pattern of the transparent electrode layer. FIG. 18 is a perspective view schematically showing the structure of an optical device and the path of light in the third embodiment. FIG. 19A is a view showing the relationship of time course of the rotation angle of the voltage distribution pattern of the electrode 9B, the output light quantity of the light source, the light quantity detected by the light detector, and their normalized difference signal in the third embodiment. . FIG. 19B is a diagram showing the relationship between the divided regions of the electrode 9B and the azimuth of the horizontal scanning beam in the third embodiment. FIG. 19C is a view for explaining the relationship between horizontal and vertical scanning by laser light corresponding to the divided regions of the electrode 9B in the third embodiment and the position between scanning light beams. FIG. 20A is a diagram showing the relationship between the detection difference signal for the divided region B1 of the electrode 9B and the horizontal direction scanning azimuth angle in the third embodiment. FIG. 20B is a diagram for explaining the relationship between the detection difference signal for the divided region B3 of the electrode 9B and the horizontal direction scanning azimuth angle in the third embodiment. FIG. 20C is a diagram for explaining the relationship between the detection difference signal for the divided region B5 of the electrode 9B and the horizontal direction scanning azimuth angle in the third embodiment. FIG. 20D is a diagram for explaining the relationship between the detection difference signal for the divided region B2 of the electrode 9B and the horizontal direction scanning azimuth angle in the third embodiment. FIG. 20E is a diagram for explaining the relationship between the detection difference signal for the divided region B4 of the electrode 9B and the horizontal direction scanning azimuth angle in the third embodiment. FIG. 21A is a perspective view schematically showing the configuration of an optical device and the path of light in the fourth embodiment. FIG. 21B is a cross-sectional view schematically showing the configuration of an optical device and the path of light in the fourth embodiment. FIG. 22 is a diagram schematically showing propagation paths of radiation light in the output grating coupler in the fourth embodiment when there is aberration correction control. FIG. 23A is a view showing the relationship of time lapse of the sum of the ratio of detected light amount, detected light amount of the light detector, detected light amount of light source, and light amount in the fourth embodiment; . FIG. 23B is a diagram showing the relationship between the split region of the electrode 9B and the direction of the horizontal scanning beam in the fourth embodiment. FIG. 23C is a diagram showing a relationship between a scanning angle and a signal indicating a detected light amount ratio with respect to the scanning light beam b1, the scanning light beam b2, the scanning light beam b3, the scanning light beam b4 and the scanning light beam b5 in the fourth embodiment. FIG. 24A is a view schematically showing a relationship between an electrode pattern on the transparent electrode layer side and an applied voltage. FIG. 24B is a view schematically showing the relationship between the electrode pattern on the reflective layer side and the applied voltage. FIG. 24C is a view schematically showing the relationship between the configuration obtained by aligning and overlapping the electrode pattern on the transparent electrode layer side and the electrode pattern on the reflective layer side, and the applied voltage. FIG. 25A is a view for explaining patterns of electrodes on the transparent electrode layer side in the fourth embodiment. FIG. 25B is a view for explaining patterns of electrodes on the reflective layer side in the fourth embodiment. FIG. 25C is a view schematically showing a configuration in which the electrode pattern on the transparent electrode layer side and the electrode pattern on the reflective layer side are aligned and overlapped in the fourth embodiment. FIG. 25D is a view schematically showing a relation between a part of the electrode pattern shown in FIG. 25C and a propagation path of guided light in the fourth embodiment. FIG. 26A is a view schematically showing a laser beam vertically emitted from a phased array in the conventional example. FIG. 26B is a view schematically showing a laser beam emitted obliquely from the phased array in the conventional example.

(Findings that formed the basis of this disclosure)
Before describing the embodiments of the present disclosure, the findings underlying the present disclosure will be described. In this specification, the term "light" is used not only for visible light but also for infrared light.

There are two representative ways to illuminate the light to determine the position of objects scattered in the field of view. One is a method of uniformly illuminating the entire area of the field of view with light pulses. The other is a method of comprehensively scanning the entire area of the field of view with a directional laser beam. The latter method can suppress the amount of emitted light smaller than the former method, and is safe for humans located on the object side.

Generally, in scanning with a laser beam, a light source, a photodetector and a galvano mirror are placed on a rotating stage. The light emitted from the light source is reflected by the galvano mirror. At that time, light scanning can be performed in the vertical direction by rotating the galvano mirror up and down, and light scanning can be performed in the horizontal direction by rotating the rotation stage. However, due to the mechanical structure, the scanning speed is slow, and the apparatus is large and expensive.

For example, a phased array shown in Patent Document 1 can be cited as an approach for making the mechanism free.

The principle of light scanning by the phased array will be described below.

FIGS. 26A and 26B are diagrams schematically showing laser beams emitted in the vertical direction and in the oblique direction from the phased array in the conventional example, respectively. In the example shown to FIG. 26A and FIG. 26B, several wave source 21 is uniformly arranged by the space | interval of pitch (xi) on x-axis. When light of the wavelength λ having the same phase is oscillated from the plurality of wave sources 21, as shown in FIG. 26A, the excitation light propagates by forming a wavefront 21a parallel to the x axis. When light is oscillated such that the phase difference between adjacent left and right wave sources becomes Λ sin θ, as shown in FIG. 26B, the excitation light propagates by forming a wavefront 21 b forming an angle θ with the x axis. By arranging the wave sources 21 uniformly along the x-axis and y-axis and adjusting their excitation phase, it is possible to set the propagation direction of the excitation light in two axial directions.

However, in the above-described conventional method, the pitch Λ of the wave source 21 needs to be equal to or less than a fraction of the wavelength λ in order to form a wavefront. In the case of radio waves, the wavelength is, for example, 10 cm or more. For this reason, it is possible to arrange a plurality of wave sources 21 functioning as an antenna at intervals of a fraction of the wavelength or less. However, in the case of light, the wavelength is, for example, about 1 μm. For this reason, it is not easy to arrange a plurality of wave sources 21 at submicron intervals. In the case of a laser, light oscillates through an amplification process in the resonator. Therefore, unlike radio waves, it is not easy to control the phase of the laser.

Therefore, the inventor has conceived of a novel optical device.

The present disclosure includes the optical devices described in the following items.

[Item 1]
The optical device according to the first item includes a light source for emitting a laser beam, an optical waveguide element located on the optical path of the laser beam, a bottom surface located on the optical path and facing the optical waveguide element, and A first transparent member having a side surface that is rotationally symmetrical about a virtual axis along the light path as a central axis, and a control circuit. The optical waveguide element includes a plurality of portions disposed along the radial direction of a virtual circle centered on the point on which the laser beam is incident and having different refractive indices, and a part of the incident laser beam A first grating propagating along the radial direction in the optical waveguide element as propagating light, and an outer side of the first grating are disposed along the radial direction, and the refractive indexes are mutually different. And a second grating for causing a part of the propagated light to be emitted from the optical waveguide element as an emitted light. The emitted light is incident on the first transparent member from the bottom surface or the side surface, and is emitted from the side surface.

[Item 2]
In the optical device according to the first item, the first grating may have a concentric structure centered on the point.

[Item 3]
In the optical device according to the first item, the second grating may have a concentric structure centered at the point.

[Item 4]
In the optical device according to the first item, the first transparent member may have a cylindrical shape or a truncated cone shape.

[Item 5]
In the optical device according to the fourth item, the side surface of the first transparent member may include a third grating whose grating vector is parallel to the central axis.

[Item 6]
The optical device according to the fifth item further includes a cylindrical second transparent member surrounding the first transparent member and coaxial with the central axis, and the inner side surface and the outer side surface of the second transparent member May include a fourth grating whose grating vector is parallel to the central axis.

[Item 7]
In the optical device according to any of the fourth to sixth items, a transparent layer in contact with the first transparent member is further included on the first grating and the second grating, and the transparent layer is It may have a refractive index of 8 or more.

[Item 8]
In the optical device according to any one of the first to seventh items, the control circuit causes the light source to change the wavelength of the laser light to thereby determine the direction of the laser light emitted from the optical waveguide element. It may be changed.

[Item 9]
In the optical device according to any one of the first to eighth items, the optical waveguide device includes a first dielectric layer, a second dielectric layer on the first dielectric layer, and the second dielectric layer. And a third dielectric layer on the dielectric layer, wherein a refractive index of the second dielectric layer is higher than a refractive index of the first dielectric layer and a refractive index of the third dielectric layer. A first position between the second dielectric layer and the first dielectric layer, and a second position between the second dielectric layer and the third dielectric layer The first grating and the second grating are disposed in at least one selected from the group, and a part of the laser light incident on the second dielectric layer is the light beam as the propagation light. The second grating propagates along the radial direction in the second dielectric layer and serves as the outgoing light. Et al may be emitted.

[Item 10]
In the optical device pertaining to the ninth item, the optical waveguide element may further include a reflective layer, and the first dielectric layer may be disposed between the second dielectric layer and the reflective layer. .

[Item 11]
In the optical device pertaining to the ninth or tenth item, the optical waveguide element further includes a first electrode layer and a transparent second electrode layer, and the first electrode layer and the second electrode layer And the first dielectric layer, the second dielectric layer, and the third dielectric layer are disposed between the first electrode layer and the second electrode layer. The third dielectric layer may be a liquid crystal layer including liquid crystal.

[Item 12]
In the optical device according to the eleventh item, in a state where a voltage is not applied to the liquid crystal layer, the alignment direction of the liquid crystal is perpendicular to the grating vector of the first grating or the grating vector of the second grating. It may be.

[Item 13]
In the optical device according to the eleventh item, the optical waveguide element is disposed between the first grating and the second grating along the radial direction and has a plurality of portions having different refractive indexes. The alignment direction of the liquid crystal may be perpendicular to the grating vector of the fifth grating in a state further including a fifth grating that does not apply a voltage to the liquid crystal layer.

[Item 14]
In the optical device pertaining to the eleventh item, at least one electrode layer selected from the group consisting of the first electrode layer and the second electrode layer is a first electrode facing the first grating and A second electrode facing the second grating, and a third electrode between the first electrode and the second electrode, wherein the third electrode is the virtual circle The plurality of conductive divided regions may be arranged along the circumferential direction of the plurality of conductive regions, and the plurality of divided regions may be insulated from each other.

[Item 15]
In the optical device pertaining to the fourteenth item, the control circuit may control the direction of the emitted light by controlling a voltage applied to the liquid crystal layer via the second electrode.

[Item 16]
In the optical device according to the fourteenth or fifteenth item, the control circuit controls the voltage applied to the liquid crystal layer through the first electrode to allow the laser light to be transmitted from the first grating. The efficiency of coupling to the propagating light may be controlled.

[Item 17]
In the optical device according to any of the fourteenth to the sixteenth items, the control circuit is a divided area facing a portion in the second dielectric layer through which the propagation light propagates among the plurality of divided areas. Voltage may be sequentially applied.

[Item 18]
The optical device according to any of the fourteenth to seventeenth aspects further comprises a polarization spectroscope, a photodetector, and a polarization rotator, wherein the polarization spectroscope and the polarization rotator are the light source and the light source. Located on the optical path to the first transparent member, the control circuit changes the polarization direction of the laser beam passing through the polarization rotator by controlling the voltage applied to the polarization rotator , A part of the light emitted from the optical waveguide element, reflected by the object, and incident on the optical waveguide element is detected light after passing through the optical waveguide element, the polarization rotator, and the polarization spectroscope The light may be incident on the light detector, and the light detector may generate an electrical signal according to the amount of the detection light.

[Item 19]
In the optical device pertaining to the eighteenth item, the control circuit is configured to calculate the time between the maximum value and the minimum value of the amount of the detection light detected by the light detector while the light source emits the laser light. The rotation angle of the polarization direction of the laser beam which has passed through the polarization rotator may be controlled by acquiring the interval and adjusting the voltage applied to the polarization rotator based on the time interval.

[Item 20]
The optical device according to any of the fourteenth to seventeenth items further comprises a first polarization spectroscope, a polarization converter, a spectroscope, and a photodetector, and the photodetector is configured to And a second light detector, wherein the first polarization spectroscope, the polarization converter, and the spectroscope are disposed on the light path between the light source and the first transparent member. A portion of the light that is located, emitted from the optical waveguide element, reflected by the object, and passed through the optical waveguide element, and then enters the spectroscope, passes through the spectroscope and the polarization converter, The other part of the light incident on the first light detector as the first detection light and incident on the spectroscope after passing through the spectroscope is the second detection light as the second detection light. And the first light detector receives a first electrical signal corresponding to the amount of the first detection light. Form, the second optical detector may generate a second electrical signal corresponding to the amount of the second detection light.

[Item 21]
In the optical device pertaining to the twentieth item, the polarization converter may be a quarter wave plate.

[Item 22]
In the optical device pertaining to the twentieth item, the polarization converter may convert light of linear polarization into light of circular tangential direction.

[Item 23]
The optical device according to any of the twentieth to twenty-second items further comprises a second polarization spectroscope, and the photodetector further comprises a third photodetector, which is emitted from the optical waveguide element, After being reflected by the object and passing through the optical waveguide element and the spectroscope, a part of the light incident on the second polarization spectroscope is subjected to a third detection after passing through the second polarization spectroscope The other part of the light incident on the second photodetector as light and incident on the second polarization spectroscope passes through the second polarization spectroscope, and then a fourth detection light As the third light detector, the third light detector may generate an electric signal according to the amount of the fourth detection light.

[Item 24]
In the optical apparatus according to the twentieth or twenty first item, the control circuit receives the first electric signal and the second electric signal, adds the sum of the first electric signal and the second electric signal, and An electrical signal may be generated according to the ratio of the first electrical signal to the second electrical signal.

[Item 25]
In the optical device according to any of the eighteenth to twenty-fourth items, the control circuit is configured to minimize the maximum value of the amount of light detected by the light detector while the light source emits the laser light. The voltage applied to the first electrode may be controlled so that

[Item 26]
In the optical device according to any of the eighteenth to twenty-fifth items, the light detector includes a filter circuit, and the control circuit is a first light pulse in which intensity modulation signals of different frequencies are superimposed on the light source. And the second light pulse are sequentially emitted, and the light detector emits light from the light waveguide element to the light detector, reflects the object, and enters the light waveguide element as part of the first light pulse, and A portion of the second optical pulse emitted from the optical waveguide element, reflected by the object, and incident on the optical waveguide element is detected, and a signal corresponding to the amount of the portion of the first optical pulse And a signal corresponding to the part of the second light pulse may be separated and output.

[Item 27]
In the optical device according to the fourteenth item, in the at least one electrode layer, the boundary between two adjacent ones of the plurality of divided regions has a zigzag shape along the radial direction. Good.

[Item 28]
In the optical device according to the twenty-seventh item, in each of the first electrode layer and the second electrode layer, a boundary between two adjacent divided regions of the plurality of divided regions is in the radial direction. In the first electrode layer when viewed in a direction perpendicular to any of the first dielectric layer, the second dielectric layer, and the third dielectric layer. The boundary and the boundary in the second electrode layer may form a shape in which rhombuses are continuous.

[Item 29]
The optical device according to the twenty-ninth item is a light source for emitting laser light, and a photodetector for generating an electric signal according to the amount of incident light, the photodetector including a filter circuit, the light source, and A control circuit for controlling the light detector, the control circuit causing the light source to sequentially emit a first light pulse and a second light pulse on which intensity modulation signals of different frequencies are superimposed; The light detector is made to detect a part of the first light pulse and a part of the second light pulse reflected by the object, and the processing of the filter circuit makes it possible to detect the one of the first light pulses. A signal corresponding to the amount of part and a signal corresponding to the part of the second light pulse are separated and output.

[Item 30]
The optical waveguide element according to the thirtieth item comprises a first dielectric layer, a second dielectric layer on the first dielectric layer, and a third dielectric on the second dielectric layer. And a pair of electrode layers sandwiching the first to third dielectric layers, wherein the refractive index of the second dielectric layer is equal to the refractive index of the first dielectric layer and the third dielectric layer. The third dielectric layer is a liquid crystal layer, and the electrode layer closer to the first dielectric layer of the pair of electrode layers is a reflective layer The electrode layer closer to the third dielectric layer is a transparent electrode layer, and at least one of the pair of electrode layers includes a plurality of conductive divided regions arranged along a certain direction, The plurality of divided regions are isolated from each other, and among the plurality of divided regions, the boundary between any two adjacent divided regions has a zigzag shape. That.

[Item 31]
In the optical waveguide element according to the thirtieth item, each of the pair of electrode layers includes the plurality of divided regions, and when viewed from a direction perpendicular to any of the first to third dielectric layers, The boundary at one of the pair of electrodes and the boundary at the other may form a continuous rhombus shape.

In the present disclosure, all or part of a circuit, unit, device, member or part, or all or part of a functional block in a block diagram represents a semiconductor device, a semiconductor integrated circuit (IC), or a large scale integration (LSI). It may be implemented by one or more electronic circuits, including: The LSI or IC may be integrated on one chip or may be configured by combining a plurality of chips. For example, functional blocks other than storage elements may be integrated on one chip. Although the term “LSI” or “IC” is used here, the term is changed depending on the degree of integration, and may be called system LSI, VLSI (very large scale integration), or ULSI (ultra large scale integration). A Field Programmable Gate Array (FPGA) programmed after the manufacture of the LSI, or a reconfigurable logic device capable of reconfiguring junctions inside the LSI or setting up circuit sections inside the LSI can also be used for the same purpose.

Furthermore, all or part of the functions or operations of the circuits, units, devices, members or parts can be performed by software processing. In this case, the software is recorded on a non-transitory recording medium such as one or more ROMs, optical disks, hard disk drives, etc., and the software is identified by the software when it is executed by a processor. The functions are performed by a processor and peripherals. The system or apparatus may include one or more non-transitory storage media on which software is recorded, a processor, and any hardware devices required, such as an interface.

Hereinafter, more specific embodiments of the present disclosure will be described. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. The present inventors provide the attached drawings and the following description so that those skilled in the art can fully understand the present disclosure, and intend to limit the subject matter described in the claims by these is not. In the following description, components having the same or similar functions are given the same reference numerals.

First Embodiment
FIG. 1A and FIG. 1B are a perspective view and a cross-sectional view schematically showing the configuration of an optical device and the path of light in the first embodiment, respectively. FIG. 1C is a perspective view schematically showing the configuration of a light source in the optical device. FIG. 1D is a perspective view schematically showing another form of a cylindrical body in the optical device. FIG. 2A is a diagram showing a vector diagram of the relationship between incident light and guided light in the input grating coupler and the relationship between guided light and emitted light in the output grating coupler. FIG. 2B is a diagram showing a vector diagram of the relationship of diffraction on a cylindrical surface.

The course of the light beam in the first embodiment will be described.

In the example shown in FIGS. 1A and 1B, the optical device includes the light source 1, the collimator lens 2a, the reflection mirror 3, the polarization spectroscope 4, the polarization rotator 5, the condenser lens 2b, and the cylindrical body 6 , An optical waveguide element 7, a control circuit 30, a control circuit 31, and a control circuit 32. The control circuit 30, the control circuit 31, and the control circuit 32 may be integrated into one control circuit. In the following description, for the sake of convenience, the axis L is in the vertical direction, and the direction orthogonal thereto is in the horizontal direction. The polarization rotator 5, the focusing lens 2b, the cylindrical body 6, and the optical waveguide element 7 are disposed with the axis L as a central axis.

The light source 1 emits a laser beam 10 a which is linear polarized light of wavelength λ by an oscillation signal from the control circuit 30 that controls laser oscillation. The light source 1 may be a Fabry-Perot laser light source, but may be configured as shown in FIG. 1C, for example. The light source 1 shown in FIG. 1C has a configuration in which a Fabry-Perot laser light source 1a is combined with a fiber Bragg grating 1b. The fiber Bragg grating 1b is constituted by a fiber-shaped core 36 and a cladding 37 surrounding the core. The refractive index of the core 36 is higher than the refractive index of the cladding 37. The core 36 is formed with a grating that produces a periodic refractive index profile along the central axis of the fiber. The light 10A emitted from the laser light source 1a enters the incident end 36a of the AR coated core 36 and becomes guided light propagating in the core. Bragg reflection diffraction light from the grating is fed back to the laser light source 1a side. The feedback light causes the laser light source 1a to oscillate at a wavelength corresponding to the pitch of the grating. As a result, light 10a of a stable wavelength is emitted from the emission end 36b of the fiber Bragg grating 1b. In the configuration shown in FIG. 1C, the fiber Bragg grating 1 b is sandwiched by the fixing plate 39 via the piezoelectric element 38. The control circuit 35 applies a voltage to deform the piezoelectric element 38 to press the fiber Bragg grating 1 b. The pressure changes the condition of reflection diffraction by the grating. Thereby, the wavelength of the emitted light 10a can be controlled. The displacement response of the piezoelectric element 38 is from several kilohertz to several tens of kilohertz. Therefore, wavelength tuning corresponding to the response is possible.

The light 10a becomes parallel light 10b by the collimator lens 2a, is reflected by the reflection mirror 3 to become light 10c incident on the polarization spectroscope 4, and becomes light 10d to be transmitted through the polarization spectroscope 4. The polarization spectroscope 4 is located on the light path from the light source 1 to the polarization rotator 5. The polarization spectroscope 4 is, for example, a polarization beam splitter. A beam shaping prism may be inserted between the collimating lens 2 a and the reflection mirror 3 to convert the distribution of the laser light 10 a spreading in an ellipse into a circle. The light 10d transmitted through the polarization spectroscope 4 enters the polarization rotator 5 along the central axis L in the state of linear polarization in the polarization direction 11d. The polarization rotator 5 is located on the optical path of the light 10 a emitted from the light source 1. A voltage is applied to the polarization rotator 5 by the control signal from the control circuit 31 that controls the polarization. As a result, the polarization direction 11e of the light 10e emitted from the polarization rotator 5 rotates relative to the polarization direction 11d. The light 10 e passes through the condenser lens 2 b along the central axis L, and enters the cylindrical body 6 which is an example of the first transparent member having the refractive index n ₀ and the radius r ₀ . The central axis L is located on the optical path of the light 10 e that has passed through the polarization rotator 5 and can be said to be an axis along the optical path.

The optical waveguide element 7 is located on the optical path of the light 10 e that has passed through the polarization rotator 5. The optical waveguide element 7 includes a transparent flat substrate 7 f and a flat substrate 7 a. The transparent flat substrate 7 f is a transparent substrate having a refractive index n ₀ ′. The optical waveguide element 7 includes a buffer layer 7c having a low refractive index, a waveguide layer 7d having a high refractive index on the buffer layer 7c, and a liquid crystal layer 7e on the waveguide layer 7d. The refractive index of the waveguide layer 7d is higher than the refractive index of the buffer layer 7c and the refractive index of the liquid crystal layer 7e. The optical waveguide element 7 includes a reflective layer 7b on the side opposite to the side in contact with the waveguide layer 7d of the buffer layer 7c. For example, on the upper surface of the flat substrate 7a, a reflective layer 7b of Al or the like, a transparent buffer layer 7c of SiO ₂ or the like, and a transparent waveguide layer 7d of Ta ₂ O ₅ or the like are formed in this order.

The optical waveguide element 7 includes a grating 8a which is an example of a first grating, a grating 8b which is an example of a fifth grating, and a grating 8c which is an example of a second grating. In the example shown in FIGS. 1A and 1B, the grating 8a, the grating 8b, and the grating 8c, which are concavo-convex gratings having a concentric structure centering on the axis L, are formed on the surface of the waveguide layer 7d. The grating 8a and the grating 8c function as a grating coupler. The grating 8 b is a grating for liquid crystal alignment. Depending on the application, the grating 8a, the grating 8b, the grating 8c, and the optical waveguide element 7 may have a fan-like shape, for example, by cutting a part of the shape of a concentric circle.

The grating 8 a is formed in a circular area of radius r ₁ centered on the axis L. Pitch of the grating 8a is lambda _0, the depth is _{d 0.} Grating 8c is formed from a radius r ₂ to the annular area ranging from a radius r _3. The pitch of the grating 8c is Λ ₁ and depth d ₁ . The grating 8 b is formed in an annular zone ranging from the radius r ₁ to the radius r ₂ . Pitch of the grating 8b is for example 0.8Ramuda ₁ or less, the depth _{d 1.} Typical sizes of radius r ₁ , radius r ₂ and radius r ₃ are of the order of millimeters. By the pitch of the grating 8b and 0.8Ramuda ₁ or less, the unevenness of the grating 8b acts for liquid crystal alignment, does not function as a coupler. Therefore, the unevenness of the grating 8b does not emit the guided light.

The grating 8a, the grating 8b, and the grating 8c may be formed on the surface side of the buffer layer 7c if the concavo-convex shape appears on the liquid crystal side surface of the waveguide layer 7d. By forming an uneven shape on the surface of the waveguide layer 7d, the grating acts as an alignment means of liquid crystal. That is, the liquid crystal is aligned in the direction of the grating. On the lower surface side of the transparent flat substrate 7f, that is, on the waveguide layer side, a transparent electrode layer 7g of ITO or the like is formed. The transparent electrode layer 7g faces the waveguide layer 7d via the liquid crystal layer 7e. The transparent electrode layer 7g is divided into three electrodes 9A, an electrode 9B, and an electrode 9C having the axis L at the same center. The electrode 9A, the electrode 9B, and the electrode 9C face the grating 8a, the grating 8b, and the grating 8c, respectively. When no voltage is applied to the liquid crystal layer 7e, the liquid crystal molecules of the liquid crystal layer 7e are aligned along the direction of the unevenness on the surface of the waveguide layer 7d. In other words, the alignment direction of the liquid crystal in the liquid crystal layer 7e is parallel to the surface of the waveguide layer 7d and perpendicular to the lattice vectors of the grating 8a, the grating 8b, and the grating 8c. The reflective layer 7 b and the transparent electrode layer 7 g function as electrodes for controlling the alignment of liquid crystal. The electrode 9A, the electrode 9B, and the electrode 9C are independent electrodes. Instead of the transparent electrode layer 7g, the reflective layer 7b may be divided into three electrodes, or each of the transparent electrode layer 7g and the reflective layer 7b may be divided into three electrodes.

The grating 8b may be formed on the lower surface side of the transparent flat substrate 7f. A concentric grating centered on the axis L may be formed at a position facing the grating 8a and the grating 8c on the lower surface side of the transparent flat substrate 7f. When the unevenness is formed on the lower surface, the unevenness is transferred also to the surface of the transparent electrode layer 7g. Thereby, the liquid crystal molecules of the liquid crystal layer 7e can be aligned along the direction of the unevenness. Naturally, liquid crystal molecules of the liquid crystal layer 7e can be aligned by forming an alignment film such as polyimide on the surfaces of the waveguide layer 7d and the transparent electrode layer 7g and rubbing it in the rotational direction.

The light 10 f passing through the lower surface of the cylindrical body 6 is focused along the central axis L to the grating 8 a which is a grating coupler. The light 10 f focused on the grating 8 a excites the guided light 10 g going from the center O of the concentric circle which is the intersection of the waveguide layer 7 d and the axis L in the waveguide layer 7 d.

The coupling condition to the guided light 10g is that the grating vector PO represented by the arrow of size λ / Λ ₀ is equal to the effective refractive index N, as shown in FIG. 2A. The said coupling conditions are described by Formula (1).

The light 10fa transmitted through the grating 8a is also reflected by the reflection layer 7b, and is again incident on the grating 8a to enhance the excitation of the guided light 10g. The guided light 10 g propagates along the radial direction of the concentric circles, is emitted at an angle θ ₁ from the grating 8 c which is a grating coupler, and becomes the emitted light 10 h toward the cylindrical body 6 side.

Binding conditions to the emitted light, as shown in FIG. 2A, the perpendicular foot of vector OP 1 _'matches the end point P ₁ of the grating vector PP ₁ represented by the magnitude lambda / lambda ₁ of dashed arrows It is. The said coupling conditions are described by Formula (2).

The light 10 ha emitted toward the reflective layer 7 b is also reflected by the reflective layer 7 b and overlaps with the emitted light 10 h. A voltage is applied to the liquid crystal layer 7 e via the pair of electrode layers of the reflective layer 7 b and the transparent electrode layer 7 g by the control signal of the control circuit 32 that controls the alignment of the liquid crystal. This according with the change in orientation of the liquid crystal, the refractive index n ₁ of the liquid crystal is changed, a change in the effective refractive index N of the guided light 10g. If the effective refractive index of the guided light 10g changes in the region of the grating 8c, the direction of the light emitted from the grating 8c to the outside of the optical waveguide element 7 changes. The control circuit 32 can independently send signals to the electrode 9A, the electrode 9B, and the electrode 9C. The voltage signal applied to the liquid crystal layer is an alternating wave. The orientation direction of the liquid crystal is inclined toward the normal direction side of the surface of the waveguide layer 7d depending on the amplitude of the AC wave, and the inclination angle of the orientation direction is determined. In the following description, the voltage applied to the liquid crystal layer means the amplitude of the AC wave applied to the liquid crystal layer.

The emitted light 10 h passes through the lower surface of the cylindrical body 6 and becomes refracted light 10 j which refracts the cylindrical surface 6 a which is the side surface of the cylindrical body 6 from the horizontal plane at an angle of _θθ ′. The refractive equation is described by equation (3).

A blazed grating with a pitch of ₂ may be formed on the surface of the cylindrical surface 6a, which is an example of a third grating. In the blazed grating, a saw-like groove is formed along a direction perpendicular to the central axis L. The blazed grating, refracted light 10j diffracts in a vertical plane, the outgoing light 10i emitted to the outside at an angle theta _⊥ from the horizontal plane. Relationship diffraction, as shown in FIG. 2B, the distance between the 'foot _{P 2} and vector OP ₃ of a perpendicular' foot _{P 3} of a perpendicular vector OP ₂ is lattice vector _P 3 _{P 2} (size lambda / lambda Expressed by equaling _two dashed arrows). The relationship of diffraction is described by equation (4).

As shown in FIG. 1D, the cylindrical body 6 may be surrounded by a cylindrical body 6A which is an example of a second transparent member. The central axis of the cylindrical body 6A is the same as the central axis of the cylindrical body 6. Blazing gratings having a pitch 表面_2b and a pitch Λ _2c , which are an example of a fourth grating, are formed on the inner surface 6b and the outer surface 6c of the cylindrical body 6A. In the example shown in FIG. 1D, the emitted light 10h is diffracted three times by a blazed grating with a pitch Λ ₂ , a pitch Λ _2b and a pitch Λ _2c to become an emitted light 10i. By dispersing the diffraction three times, the pitch of each blazed grating can be set large and processing becomes easy.

The cylindrical body 6 is located on the transparent flat substrate 7 f. In general, instead of the cylindrical body 6, a transparent member which is a rotationally symmetric object with the axis L as a central axis may be used. If the pitch of the grating 8c changes, the generatrix of the rotationally symmetric body has the shape of a curve. When the pitch is constant, the generatrix of the rotationally symmetric body has a linear shape, and the rotationally symmetric body becomes a cylinder or a cone.

The scanning in the vertical direction by the outgoing beam 10i is realized by the change of the wavelength of the light source 1 or the change of the refractive index of the liquid crystal layer 7e at the electrode 9C. From equation (2), the derivative of the effective refractive index N with respect to the radiation angle θ ₁ is described by equation (5), and the derivative of the radiation angle θ ₁ with respect to the wavelength λ is described by equation (6). The derivative of the emission angle _{θθ in} the vertical direction with respect to the wavelength λ is described by the equation (7) according to the equations (3) to (6).

The light emitted from the optical waveguide element 7 and reflected by the external object is returned to the optical waveguide element 7. A part of the light incident on the optical waveguide device 7 propagates in the optical waveguide device 7 toward the central axis L by the grating 8 c, and is emitted from the optical waveguide device 7 by the grating 8 a, and the polarization rotator 5 and the polarization spectroscope The light beam is incident on the light detector 12 through 4. The light detector 12 generates an electrical signal according to the amount of incident light. This process will be described in more detail.

The light reflected by the surface of the external object reverses the optical path of the outgoing beam 10i and enters the cylindrical surface 6a, and then the emitted light 10h, the guided light 10g, and the light 10f on the input side, the light 10e, and Reverse the light path of the light 10d. At the input at grating 8c, only light of the same wavelength and the same phase plane as at the output of the forward pass is selectively coupled. Therefore, stray light having different wavelengths and / or phases is effectively eliminated. By the control of the polarization rotator 5, the polarization direction of the reverse light 10D is rotated by 90 degrees as compared with the polarization direction of the light 10d at the time of the forward path. Therefore, backward light 10D will become light 10D ₀ reflects the polarization spectroscope 4, it is detected by the photodetector 12. The photodetector 12 includes a detection circuit 33. The detection signal is processed by the detection circuit 33. In the example shown in FIGS. 1A and 1B, the optical device may further comprise a control circuit. The control circuit 34 generates, from the detection signal of the detection circuit 33, for example, a control signal for controlling the orientation of the light source or the liquid crystal. Further, the control circuit 30, the control circuit 31, the control circuit 32, the control circuit 34, and the control circuit 35 may be integrated into one control circuit.

The polarization spectroscope 4 may use a half mirror instead of the polarization beam splitter. At this time, regardless of the control of the polarization rotator 5, the backward light 10 D of the light 10 d is reflected by the half mirror and detected by the light detector 12. When a half mirror is used, the light quantity is halved in the forward path and is halved in the return path. That is, the light amount is 1⁄4 in the reciprocating path. Although the polarization control can be simplified, the amount of detected light is reduced.

FIG. 3A is a perspective view schematically showing the polarization direction and the input state of incident light in the first embodiment. FIG. 3B is a cross-sectional view schematically showing the input grating 8a. FIG. 3C is a cross-sectional view showing the appearance of light that is coupled in and guided by light intensity. FIG. 3D is a plan view schematically showing an input grating coupler. FIGS. 3E to 3G are plan views showing the relationship between the polarization direction and the input propagation direction by the light intensity. In the example shown in FIGS. 3B and 3D, the diameter of the grating 8a is 2r ₁ = 10 μm, the pitch is Λ ₀ = 0.57 μm, and the depth is d ₀ = 0.10 μm. The material of the waveguide layer 7 d is Ta ₂ O ₅ and the layer thickness is 0.15 μm. The refractive index of the liquid crystal layer 7 e and the buffer layer 7 c is the same as the refractive index of SiO ₂ . At this time, guided light in the TE mode is excited by vertical incidence. In the examples shown in FIG. 3C and FIGS. 3E to 3G, analysis results of wavelength λ = 0.94 μm are shown.

As shown in FIGS. 3C and 3E, when the polarization direction 11e of the light 10f which is incident light is parallel to the y-axis direction, the guided wave light to be excited propagates strongly in the x-axis direction. As shown in FIG. 3F, when the polarization direction 11e of the light 10f is parallel to the 135 degree direction, the guided wave light to be excited propagates strongly in the 45 degree direction. As shown in FIG. 3G, when the polarization direction 11e of the light 10f is parallel to the x-axis direction, the guided wave light to be excited propagates strongly in the y-axis direction. As shown in FIGS. 3C and 3E to 3G, the grating 8a spreads a portion of the light 10f around the direction perpendicular to the polarization direction 11e in the waveguide layer 7d of the optical waveguide element 7. Propagate. For example, when the guided light to be excited is in the TM mode, the propagation direction is rotated by 90 degrees and aligned with the polarization direction at the time of incidence. If the polarization direction of incident light can be controlled, the propagation direction of guided light can be changed. The responsiveness of the change in propagation direction is determined by the responsiveness of control of the polarization direction.

In the case of an optical device including the light source 1, the polarization rotator 5, and the optical waveguide device 7, the propagation direction of the guided light propagating in the waveguide layer 7 d is guided by applying a voltage to the polarization rotator 5. It can be changed in any direction parallel to the wave layer 7d.

FIG. 4A is a diagram showing the wavelength dependency of the input coupling efficiency of the grating 8a which is an input grating coupler in the case where there is no reflective layer in the first embodiment. FIG. 4B is a cross-sectional view schematically showing the grating 8 a in the case where there is a reflective layer in the first embodiment. FIG. 4C is a view showing the layer thickness dependency of the SiO ₂ layer which is a buffer layer of the input coupling efficiency when there is a reflective layer. FIG. 4D is a graph showing the wavelength dependency of input coupling efficiency when there is a reflective layer.

The analysis conditions in the example shown in FIG. 4A are the same as the analysis conditions in the example shown in FIGS. 3A to 3G. As shown in FIG. 4A, at a wavelength of 0.94 μm, an input efficiency of up to 20% can be obtained. The shape conditions in the example shown to FIG. 4B are the same as the shape conditions in the example shown to FIG. 3A-FIG. 3G except having provided the reflection layer 7b of Al. As shown in FIG. 4C, the input efficiency periodically increases or decreases due to the change in the layer thickness of the buffer layer 7c. When the thickness of the buffer layer 7c is 1.06 μm, the input efficiency is maximized. In the example shown in FIG. 4D, the wavelength dependency when the layer thickness of the buffer layer 7c is fixed to 1.06 μm is shown. At a wavelength of 0.944 μm, the input efficiency is at a maximum, and the maximum is 50%. Assuming that only the TE mode component of the incident light is coupled in and guided, a coupling efficiency of approximately 100% can be obtained by introducing a reflective layer and optimizing the layer thickness of the buffer layer.

FIG. 5A is a plan view showing the relationship between the polarization direction of incident light and the input propagation direction in the first embodiment by light intensity. As shown in FIGS. 3E to 3G, when TE-mode guided light is excited at normal incidence, the polarization direction is parallel to the y-axis, and the deflection angle φ with respect to the x-axis is defined.

FIG. 5B is a diagram showing the relationship between the deflection angle φ and the intensity I of the guided light propagating and the relationship between the deflection angle φ of the light energy E included in the deflection angle range from −φ to φ. The argument range of -φ to φ also includes light propagating in the diagonal direction. The light intensity is described by equation (8) and the light energy is described by equation (9). If the light propagating in the diagonal direction is not included, 41% of the excitation guided light can be used if the light in the range of -45 degrees to 45 degrees can be captured. That is, 21% of incident light can be used together with 50% of input efficiency.

On the other hand, among the incident light, components that can not be coupled, such as the TM mode component, are reflected by the grating 8a, and return to the polarization spectroscope 4 through the cylindrical body 6, the condenser lens 2b, and the polarization rotator 5. . By reciprocating the polarization rotator 5 within the light emission time of the light source 1, the polarization direction of the light is rotated by twice the rotation angle in the forward path. Therefore, the light detector 12 can detect the reflected light corresponding to the rotation angle φ by the polarization rotator 5. Details will be described later with reference to the example shown in FIG. 16A.

On the other hand, the maximum value of the detected light quantity at the time of light emission of the light source is proportional to the efficiency of the light which can not be input to the grating 8 a of the incident light. By monitoring the maximum value of the detected light quantity, it can be used to control the input efficiency. Details will be described later with reference to the example shown in FIG. 16A.

Next, the principle of the polarization rotator will be described.

FIG. 6 is a perspective view schematically showing a configuration example of the polarization rotator in the first embodiment. Here, the polarization rotator 5 will be described using a Faraday rotator capable of higher speed response. The Faraday rotator comprises a cylindrical magnetic glass rod 5a and a coil 5b wound around it. When a current is supplied to the coil 5b by a control signal from the control circuit 31 that controls polarization, a magnetic field vector flowing along the central axis in the magnetic glass rod 5a changes in proportion to the amount of current. As a result, when light propagates along the central axis from light 10 d to light 10 e due to the Faraday effect, the polarization direction is rotated from polarization direction 11 d to polarization direction 11 e. In the case of a Faraday rotator, the response of polarization rotation reaches GHz order and is extremely fast. Although the response is inferior to that of the Faraday rotator, polarization rotation can also be performed with a liquid crystal element.

FIG. 7A is a view schematically showing propagation paths of emitted light in the grating 8c which is an output grating coupler in the case where there is no aberration correction in the first embodiment. FIG. 7B is a view schematically showing propagation paths of radiation light in the grating 8 c in the case where there is aberration correction control in the first embodiment. In the example shown to FIG. 7A and 7B, an upper stage shows a top view, a middle stage shows a perspective view, and a lower stage shows sectional drawing.

As shown in FIG. 7A, in the absence of aberration correction, the guided light 10g propagating in the waveguide layer 7d and the guided light 10g ₀ exit the grating 8c and propagate the light 10H propagating in the cylindrical body 6 and the light 10H. becomes _0, the cylindrical surface, that is, light 10I, and light 10I ₀ emitted to the outside is refracted side. As shown in the middle of FIG. 7A, the light 10 H and the light ₁₀ H ₀ intersect on the central axis L. As shown in the upper part of FIG. 7A, in plan view, the light 10I and the light 10I ₀ intersect at a point F on the central axis L and do not bend even after exiting the surface of the cylindrical body 6 It becomes divergent light going straight along.

As shown in FIG. 7B, when aberration correction is performed, the guided light 10g propagating in the waveguide layer 7d and the guided light 10g ₀ exit the grating 8c, and the light 10h propagating in the cylindrical body 6 and the light 10h It becomes ₀ and becomes light 10i and light 10i ₀ which are refracted to the surface of the cylindrical body, that is, the side surface and emitted to the outside. As shown in the middle part of FIG. 7B, the light 10 h and the light 10 h ₀ intersect on the axis L ′ away from the central axis L along the positive direction of the x axis. As shown in the upper part of FIG. 7B, in plan view, the light 10 h and the light 10 h ₀ intersect at a point F ′ on the axis L ′ and exit from the surface of the cylindrical body 6 and then bend into parallel light .

Next, a method of estimating the amount of aberration correction will be described.

FIG. 8A is a view schematically showing that light radiated from the grating 8c, which is an output grating coupler, in the first embodiment is refracted at a cylindrical surface and emitted.

The ray paths shown in FIG. 8A are as described in FIGS. 7A and 7B. In plan view, the intersection of the light 10h and the side surface of the cylinder 6 is Q, the intersection of the light 10h ₀ and the surface of the cylinder 6 'and the angular QFQ' Q a and [psi, the angular FF'Q 'phi Define as Since light 10 i ₀ is parallel to light 10 i, equation (10) holds. However, ψ ′ satisfies the relationship of equation (11).

From equation (10) and equation (11), the angle ψ is given by equation (12). On the other hand, when the distance between the point F and the point F ′ is defined as f ₀ , f ₀ is given by equation (13). Light 10H, and light 10H ₀ is a light converging at point F, the light 10h and light 10h, ₀ is the light converging at point F '. According to the aberration theory, the aberration that displaces the focal position of the focused light from F to F ′, that is, the longitudinal focal movement aberration, is given by the left side of Equation (14).

FIG. 8B is a view schematically showing a pattern of a transparent electrode layer for realizing aberration correction. Electrode 9B is in a facing position to the grating 8b, it is formed in a range from a radius r ₁ radius r _2. The electrode 9B is divided in the radial direction. In other words, the electrode 9B has a plurality of conductive divided regions aligned along the circumference of a virtual circle centered on the point on which the light 10f is incident. The control circuit 31 rotates the polarization direction 11 e of the light 10 e by a predetermined angle by changing the voltage applied to the polarization rotator 5. Thus, the control circuit 31 sequentially changes the propagation direction of the guided light 10g in the waveguide layer 7d. In synchronization with the change in the propagation direction, the control circuit 32 sequentially applies a voltage independently and sequentially to the division regions facing the portion of the waveguide layer 7d in which the guided light 10g propagates among the plurality of division regions in the electrode 9B. Do. Thereby, aberration correction can be realized and the radiation beam can be rotated.

In the example shown in FIG. 8B, the electrodes 9B are equally divided by 5 degrees in the rotation direction, and are divided into 72 electrodes 9B1 to 9B72 which are divided regions. In the example shown in FIG. 8B, only a part is displayed. The fan-shaped divided regions are electrically isolated from one another and voltages can be applied independently. When different voltages are applied to the divided regions, the refractive index of the adjacent liquid crystal layer 7e changes. As a result, the effective refractive index of the guided light 10g propagating through the corresponding position also changes. In this manner, the phase of the guided light can be changed for each declination of propagation. Assuming that the change width of the effective refractive index is ΔN, the phase difference generated between the propagation distances (r ₂ −r ₁ ) is given by the right side of equation (14). Therefore, the conditional expression for refracting the emitted light at the cylindrical surface to become parallel light is described by Expression (14). The ΔN in the aberration correction is given by the equation (15) from the equations (13) and (14).

FIG. 9A is a diagram showing the relationship between the deflection angle φ in the propagation direction and the effective refractive index change amount of guided light for achieving aberration correction in the first embodiment. In the example shown in FIG. 9A, the refractive index n ₀ = 1.58, radius r ₀ = 1.25 mm, and the width (r ₂ −r ₁ ) of the electrode 9B = 4 mm based on the equation (15). The variation width ΔN in the case is plotted. It can be seen that ΔN = 0.056 for capturing light in the declination range of −45 degrees to 45 degrees.

FIG. 9B is a diagram showing the relationship between the layer thickness of the Ta ₂ O ₅ layer which is a waveguide layer and the effective refractive index, with the liquid crystal refractive index n ₁ as a parameter. FIG. 9C is a view schematically showing the arrangement of the buffer layer 7c, the waveguide layer 7d, and the liquid crystal 7e.

The refractive index difference of nematic liquid crystal molecules is as large as about 0.20. Considering that 80% of them act as an effective refractive index difference, the effective refractive index difference is about 0.15. In the example shown in FIG. 9B, in the case of a light wavelength of 0.94 μm and the refractive index of 1.45 of the buffer layer 7c, the layer of the waveguide layer 7d calculated as n ₁ = 1.50 and n ₁ = 1.65. The relationship between thickness and effective refractive index N is represented by curve 13a and curve 13b, respectively. In the example shown in FIG. 9C, in the case where the refractive index difference of the liquid crystal is 0.15, ΔN = 0 if the layer thickness of the waveguide layer 7d formed of Ta ₂ O _{5 is} about 0.10 μm to 0.15 μm. It can be seen that a change from 06 to ΔN = 0.04 can be expected.

10A to 10D are diagrams for explaining the relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light in the first embodiment.

In the example shown in FIG. 10A, the guided light propagating from the center O toward the outer peripheral side corresponds to the positions of the fan-shaped electrodes 9B1, 9B2 and 9B72 centered on the point O, respectively. , Guided light 10g2, and guided light 10g72.

In the example shown in FIG. 10B, the strip fan-shaped electrode is replaced by a square for easy understanding, and the positional relationship between the light ray propagation path and the electrode is shown. Depending on the voltage applied to the electrodes, a difference in elevation occurs in the refractive index of the propagation path. Assuming that the refractive index at the position corresponding to the electrode 9B1 is the highest and the refractive index decreases as the distance from the electrode 9B1 increases, the equiphase surface 14a of light after passing through the electrode has a stepped shape.

In the example shown in FIG. 10C, the band fan shape is deformed into a lightning bolt shape. That is, the area of the electrode 9B is divided by a circle c1a, a circle c1b, a circle c2a, a circle c2b, and a circle c3a. The circles c1b and c2b are circles slightly larger than the circles c1a and c2a, respectively. Let the intersections of the guided light 10g72, the circle c1a, the circle c2a, and the circle c3a be an intersection point P1a, an intersection point P2a, and an intersection point P3a, respectively. The intersections of the guided light 10g1 with the circle c1a, the circle c1b, the circle c2a, the circle c2b, and the circle c3a are taken as an intersection point P1A, an intersection point P1b, an intersection point P2A, an intersection point P2b, and an intersection point P3A. The intersections of the guided light 10g2, the circle c1b, and the circle c2b are taken as an intersection P1B and an intersection P2B, respectively. The lightning shape of the electrode 9B1 connects a point O, a point P1a, a point P1b, a point P2a, a point P2b, and a point P3a, and a point O, a point P1A, a point P1B, a point P2B, a point P2A, a point P2B, and a point P3A It is a shape sandwiched between lines. However, the area of the electrode 9A is not included. The point between the point P3a and the point P3A is along the circle c3a. The other electrode has a shape in which the electrode 9B1 is rotated around the point O according to the dividing angle. In the case of 72 division, the division angle is 5 degrees.

In the example shown in FIG. 10D, the electrodes between the circle c1a and the circle c2b are replaced with diamonds for easy understanding, and the positional relationship between the light ray propagation path and the electrodes is shown. Since the electrodes are replaced by lozenges, the propagation directions of the illustrated guided light 10g1, the guided light 10g2 and the guided light 10g72 are respectively rotated in reverse by the deflection angle φ and are expressed in parallel. A light beam propagating along the propagation direction between the guided light 10g1 and the guided light 10g2 and between the guided light 10g1 and the guided light 10g72 propagates across two adjacent electrodes. The ratio of the propagation distance for each electrode changes in proportion to the deflection angle φ of the light beam. This relationship also holds between the circle c2a and the circle c3a. Therefore, depending on the voltage applied to the electrodes, a difference in elevation occurs in the refractive index of the propagation path. For example, when the refractive index at the position corresponding to the electrode 9B1 is the highest and becomes lower as the distance from the electrode 9B1 is reached, the equiphase surface of light after passing through the electrode becomes a shape 14b obtained by linear interpolation of the step shape 14a. Although five divided circles are used in the example shown in FIG. 10C, other combinations such as seven or nine may be used.

FIG. 10E is a view schematically showing how the aberration at the time of focusing on the point F ′ is corrected. The vertical axis represents the amount of aberration, and the horizontal axis represents the deflection angle φ. Aberrations in focusing at point F 'before correction are shown by curve 15. If the voltage applied to the electrodes is optimized, in the case of the electrode shape in the example shown in FIG. 10A, the aberration in focusing on the point F 'is corrected as represented by the curve 15a. In the case of the electrode shape in the example shown in FIG. 10C, the aberration in focusing on the point F 'is corrected as represented by the curve 15b. The curve 15 b corresponds to the difference of the bending line 15 B with respect to the curve 15. It is understood that the aberration is compressed to about 1/10 even in the curve 15a, and most of the aberration is corrected in the curve 15b. Therefore, by controlling voltage application to the electrode shape in the example shown in FIG. 10C, the radiation light from the grating 8c can be emitted as parallel light from the cylindrical surface. The voltage application to the electrode shape is synchronized with the propagation direction of the guided light, that is, the polarization rotation angle of the incident light. At that time, voltage application is performed to increase the refractive index of the liquid crystal so that the phase in the propagation direction where the light intensity is strongest is delayed.

From the above, the electrode 9B has the following configuration, and the control circuit 31 and the control circuit 32 perform the following operation.

The electrode 9B has a plurality of divided regions arranged along the circumference of a virtual circle centered on the point on which the light 10f is incident. The control circuit 31 rotates the polarization direction 11 e of the light 10 e by a predetermined angle by changing the voltage applied to the polarization rotator 5. Thus, the control circuit 31 sequentially changes the propagation direction of the guided light 10g in the waveguide layer 7d. In synchronization with the change in the propagation direction, the control circuit 32 sequentially applies a voltage independently and sequentially to the division regions facing the portion of the waveguide layer 7d in which the guided light 10g propagates among the plurality of division regions in the electrode 9B. Do. Thereby, aberration correction can be realized and the radiation beam can be rotated.

11A and 11B are diagrams showing the relationship between the depth d of the grating 8c and the radiation loss coefficient α when the grating duty ε is fixed at 0.5 in the first embodiment. In the example shown in FIG. 11A, the liquid crystal refractive index n ₁ = 1.6, and in the example shown in FIG. 11B, the liquid crystal refractive index n ₁ = 1.45. 11C and 11D are diagrams showing the relationship between the duty ε and the radiation loss coefficient α when the depth d is fixed to 0.01 μm in the first embodiment. In the example shown in FIG. 11C, the liquid crystal refractive index n ₁ = 1.6, and in the example shown in FIG. 11D, the liquid crystal refractive index n ₁ = 1.45. The other analysis conditions in the example shown in FIGS. 11A to 11D are the same as in the case shown in FIG. 4D in which the layer thickness of the buffer layer 7c is 1.06 μm.

When the grating depth d = 0.01 μm, the radiation loss coefficient α is about 2 (1 / mm) in the example shown in FIG. 11A, and the radiation loss coefficient α = 1 in the example shown in FIG. 11B. The size is about (1 / mm). As shown in FIGS. 11C and 11D, the radiation loss coefficient α can be reduced by shifting the duty ε from 0.5. The radiation loss coefficient α increases as the liquid crystal refractive index increases, and increases as the wavelength decreases. However, in the design example of the present embodiment, due to the interference effect of the reflected light from the reflective layer 7b, the radiation loss coefficient α behaves irregularly only when the wavelength λ is 0.93 μm.

FIG. 11E and FIG. 11F is a diagram showing the relationship between the relationship and the coupling length w ₁ and the radiation intensity of the coupling length w ₁ and the waveguide strength. In the example shown in FIG. 11E, α = 0.4 to 2.0 increases linearly proportionally at w ₁ = 0 mm to 1.5 mm, and is fixed at α = 2.0 at w ₁ > 1.5 mm . In the example shown in FIG. 11F, α = 0.2 to 1.0 increases linearly proportionally at w ₁ = 0 mm to 1.5 mm, and is fixed at α = 1.0 at w ₁ > 1.5 mm . The coupling length w ₁ is the distance from the start point r _{2 of} the coupler to the radiation position, as shown in FIGS. 12A and 12B described later. Here, the coupling length corresponding to the width of the emitted light is defined by the position where the waveguide intensity is 1 / e ² .

The example shown in FIG. 11E corresponds to the condition that the liquid crystal refractive index is high or the wavelength is short. At this time, the bonding length is 1.5 mm. The example shown in FIG. 11F corresponds to the condition that the liquid crystal refractive index is low or the wavelength is long. At this time, the bonding length is 2.5 mm.

12A and 12B are diagrams showing the positional relationship between the light emitted from the grating 8c and the cylinder in the first embodiment. In the example shown in FIG. 12A, the refractive index n ₀ ′ of the transparent flat substrate 7 f is 1.58, which is the same as the refractive index n ₀ of the cylindrical body. In the example shown in FIG. 12B, the refractive index n ₀ ′ of the transparent flat substrate 7 f is 2.0. In the example shown in FIGS. 12A and 12B, the emitted light 10h, the emitted light 10h1, and the emitted light 10h2 from the grating 8c correspond to the condition in which the wavelengths are increased in this order. At that time, the emitted light 10h, corresponding to the emitted light 10h1, and the emitted light 10h2, also coupling length _{w 1} is larger in this order.

In the example shown in FIG. 12A, the radiation angle theta ₁ with the transparent plane substrate 7f is large. Therefore, under the condition that the radiation light 10h is made to enter the small diameter cylindrical body 6, the other radiation light 10h1 and the radiation light 10h2 can not be made to enter. In the example shown to FIG. 12B, radiation angle (theta) ₁ 'in the transparent plane substrate 7f can be made small by the large refractive index of the transparent plane substrate 7f. Thereby, all the emitted light 10 h, the emitted light 10 h 1 and the emitted light 10 h 2 can be made to enter into the cylindrical body 6. By increasing the refractive index of the transparent flat substrate 7f, a large reflection loss occurs at the interface 7fa between the transparent flat substrate 7f and the liquid crystal layer 7e and at the interface 7fb between the transparent flat substrate 7f and the cylindrical body 6. In order to suppress reflection loss, for example, an AR coating process is performed on the upper and lower surfaces of the transparent flat substrate 7 f.

As described above, by increasing the refractive index of the medium between the cylindrical body 6 and the grating 8 c to, for example, a refractive index of 1.8 or more, emitted light with different radiation angles can be efficiently stored in the cylindrical body 6. It can lead.

FIG. 13A and FIG. 13B are a horizontal sectional view and a vertical sectional view showing the relationship between the radiation light from the grating 8c and the beam width of the refracted light from the cylindrical surface in the first embodiment, respectively. In the example shown in FIG. 13B, the beam width w ₁ ′ in the cylindrical body 6 satisfies the relation of the equation (16) using the radiation angle θ ₁ in the cylindrical body 6 and the coupling length w ₁ . The beam width w _屈折 of the refracted light on the cylindrical surface satisfies the relationship of the equation (17) using the radiation angle θ ₁ and the beam width w ₁ ′ in the cylindrical body 6. Thus, the beam width w _⊥ is given by equation (18). On the other hand, as shown in FIG. 13A, when the light 10h ₀ ranging 45 degrees declination -45 degrees is aberration corrected parallel light 10i ₀ in horizontal cross section, the beam width w _∥ in horizontal cross-section cylindrical body 6 The diameter of 2r is close to ₀ . Therefore, the refracted light from the cylindrical surface becomes parallel light of the beam width _w⊥ and the beam width w _∥ . These lights are Fraunhofer diffracted at a sufficiently long distance propagation. Its divergence angle alpha _⊥, and divergence angle alpha _∥, respectively (19), and is given by equation (20).

Wavelength lambda = 0.94 .mu.m, the radius _r 0 = 1.25 mm, the coupling length _w 1 = 1.5 mm, in the case of the radiation angle theta ₁ = 66 degrees, alpha _⊥ = 0.1 °, and α _∥ = 0. It becomes 02 degrees, and the spread of the beam is suppressed sufficiently small. When the spread of the beam is small, the diffusion of light in the forward path can be suppressed. Thereby, the amount of detected light can be increased.

FIG. 14A is a diagram showing the relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light in the first embodiment. FIG. 14B is a view showing the relationship between the polarization rotation angle of input light and the time course of the voltage applied to the transparent electrode in the case of laser scanning using only control of the refractive index of liquid crystal in the first embodiment. . The limit of the response speed of the liquid crystal is 1 ms between on and off, and the speed of beam scanning is 30 ms per frame.

In the example shown in FIG. 14A, the voltage applied to the divided electrodes 9B has a cycle of 90 degrees in the rotational direction. For example, the same voltage is applied to the electrode 9B1, the electrode 9B19, the electrode 9B37, and the electrode 9B55. The same voltage is applied to the electrode 9B2, the electrode 9B20, the electrode 9B38, and the electrode 9B56. The voltage applied to the electrode within an angular range of 90 degrees, which is one period, exhibits a voltage distribution pattern having a difference in height under the condition for correcting the aberration. The voltage distribution pattern rotates in synchronization with the rotation angle φ of the polarization by the polarization rotator while maintaining the pattern shape. Polarization rotation can respond much faster than voltage distribution patterns. Therefore, it is also possible to rotate only the polarized light and detect the reflected light from a plurality of directions during a certain voltage distribution pattern.

In the example shown in FIG. 14B, the polarization rotation angle φ of the input light repeats the range of 0 degree to 90 degrees with a period of T = 2 ms. The voltage applied to the electrode 9B1 represented by the solid line repeats high and low as a 2 ms cycle rectangular signal. The frequency of this repetition is close to the response limit of the liquid crystal. For this reason, the change of the refractive index of the liquid crystal represented by the broken line becomes slower than the change of the applied voltage, and becomes a movement of 2 ms cycle. By gradually shifting the phase of the applied voltage from the electrode 9B2 to the electrode 9B3 as represented by the oblique arrows, the phase of the applied voltage at the electrode 9B9 shifts by half a period, and the phase of the applied voltage at the electrode 9B18 shifts by one period, that is, 2 ms. . The phase shift width of the applied voltage is determined by the rule for correcting the aberration. As a whole of the electrode 9B, the voltage distribution pattern rotates in synchronization with the polarization rotation angle φ. The movement of the voltage distribution pattern corresponds to the horizontal scanning by the outgoing beam.

The voltage applied to the electrode 9C represented by the solid line linearly increases and decreases with a period of 30 ms. The change in the refractive index of the liquid crystal represented by the dashed line also shows the same movement as the applied voltage. However, the change in the refractive index of the liquid crystal is gradual compared to the steep fall of the applied voltage. The change in refractive index of the liquid crystal at the electrode 9C corresponds to the change in angle of the light emitted from the grating 8c. Thus, the vertical scanning by the outgoing beam exhibits a linear oscillation with a period of 30 ms. Assuming that n ₀ = 1.58, θ ₁ = 75 degrees, and ΔN = 0.045 from the equation (5), the change width of θ ₁ is 6.3 degrees. From Eq. (3) and Eq. (4), assuming that Λ ₂ = 2.5 μm, the change of the output angle _⊥ in the vertical direction becomes about 10 degrees. Therefore, by applying a voltage to the electrode 9C, scanning in the vertical direction at a change of 10 degrees of the emission angle with a cycle of 30 ms is possible.

FIG. 14C is a view showing horizontal and vertical scanning by laser light.

The scanning in the horizontal direction in the range of 0 degrees to 90 degrees is performed by the control of the polarization and the control of the liquid crystal alignment with respect to the electrode 9B. The control of the liquid crystal alignment with respect to the electrode 9C shifts the scanning position to 10 degrees in the vertical direction in 30 ms. That is, after scanning from 0 degrees to 90 degrees in the horizontal direction while shifting in the vertical direction, the horizontal position returns to 0 degrees while maintaining the vertical position. This exercise is repeated 15 times. In the next scan, the scan position is returned to the original position of 0 degree vertical position and 0 degree horizontal position, and the same motion as described above is repeated. The resolution in the horizontal direction is unlimited, and the resolution in the vertical direction, that is, the number of scanning lines, is 15 per 30 ms of one frame.

FIG. 15A shows the polarization rotation angle of the input light, the light source wavelength, the voltage applied to the transparent electrode, and the voltage applied to the transparent electrode in the case of laser scanning in which the control of the liquid crystal refractive index and the variable control of the light source are both controlled in the first embodiment. It is a figure which shows the relationship of the time progress of the rotation angle of the horizontal direction and the perpendicular direction. FIG. 15B is a view showing horizontal and vertical scanning of laser light. The relationship between the pattern of the transparent electrode layer and the propagation direction of the guided light is as described in the example shown in FIG. 14A. Further, the limit of the response speed of liquid crystal is 1 ms between on and off, and the speed of beam scanning is described as 30 ms per frame. The principle of variably controlling the wavelength has been described in the example shown in FIG. 1C. Besides, for example, there is a super periodic structure diffraction type DBR (Distributed Bragg Reflector). In the super periodic structure diffraction type DBR, the range of 40 nm can be swept at high speed with a period of 20 KHz as the variation width of the wavelength.

In the example shown in FIG. 15A, the polarization rotation angle φ of the input light repeats the range of 0 degree to 90 degrees with a period of T = 2 ms. The voltage applied to the electrode 9B1 represented by the solid line repeats high and low as a 2 ms cycle rectangular signal. The frequency of this repetition is close to the response limit of the liquid crystal. For this reason, the change of the refractive index of the liquid crystal represented by the broken line becomes slower than the change of the applied voltage, and becomes a movement of 2 ms cycle. By gradually shifting the phase of the applied voltage from the electrode 9B2 to the electrode 9B3 as represented by the oblique arrows, the phase of the applied voltage is shifted by a half cycle at the electrode 9B9, and the phase of the applied voltage is shifted by one cycle at the electrode 9B18, ie 2 ms. . The phase shift width of the applied voltage is determined by the rule for correcting the aberration. As a whole of the electrode 9B, the voltage distribution pattern rotates in synchronization with the rotation angle φ of polarization. The movement of the voltage distribution pattern corresponds to the horizontal scanning by the outgoing beam.

The voltage applied to the

electrodes

9A and 9C represented by solid lines repeats high and low with a cycle of 30 ms. The change of the refractive index of the liquid crystal represented by the broken line also shows the same movement as the applied voltage. However, the change in the refractive index of the liquid crystal is gradual compared to the steep fall of the applied voltage.

The wavelength of the light source 1 gradually increases from 0.93 μm to 0.95 μm in 30 ms while repeating high frequency oscillation with a total amplitude of 1.5 nm, and this movement is repeated in a cycle of 30 ms. When the wavelength of the light source 1 changes, the input condition at the grating 8a changes. Therefore, in order to cope with changes in input conditions, the applied voltage to the electrode 9A also gradually increases in 30 ms, and this movement is repeated in 30 ms cycles. The wavelength fluctuation of the high frequency of 1.5 nm in total amplitude does not greatly affect the input efficiency. For this reason, the voltage applied to the electrode 9A is set to correspond only to the variation of the low frequency of 20 nm width. The change in refractive index of the liquid crystal at the electrode 9C corresponds to the change in angle of the light emitted from the grating 8c. Thus, combined with the wavelength change, the vertical scanning by the outgoing beam exhibits a linear oscillation with a period of 30 ms.

Assuming that n ₀ = 1.58, θ ₁ = 75 °, Λ ₁ = 0.29 μm, and Λ ₂ = 2.5 μm from the equation (7), the wavelength change of 20 nm, the effective refractive index change of ΔN = 0.045 Thus, the change in the output angle _θ⊥ in the vertical direction is about 30 degrees. Furthermore, high frequency wavelength oscillation with a total amplitude of 1.5 nm provides an output angular oscillation with a total amplitude of 2 degrees in the vertical direction.

In the example shown to FIG. 15B, it is a figure which shows the mode of the scanning of the horizontal direction and the orthogonal | vertical direction by a laser beam. The scanning in the horizontal direction in the range of 0 degrees to 90 degrees is performed by the control of the polarization and the control of the liquid crystal alignment with respect to the electrode 9B. The control of the liquid crystal alignment with respect to the electrode 9C and the control of the low frequency wavelength shift the scanning position up to 30 degrees in the vertical direction in 30 ms. In addition, due to wavelength control of high frequency, each scanning line vibrates with a full swing width of 2 degrees in the vertical direction. That is, after scanning from 0 degrees to 90 degrees in the horizontal direction while shifting in the vertical direction, the horizontal position returns to 0 degrees while maintaining the vertical position. This exercise is repeated 15 times. In the next scan, the scan position is returned to the original position of 0 degree vertical position and 0 degree horizontal position, and the same motion is repeated. Horizontal resolution is unlimited. The resolution in the vertical direction, that is, the number of scanning lines, is 15 per 30 ms of one frame. The spacing between scan lines is 30 degrees / 15 = 2 degrees. On the other hand, the scanning lines vibrate to fill in the vertical direction. Therefore, the vertical resolution is also almost unlimited.

The voltage applied to the electrode 9A is used for control to maximize the input coupling efficiency. The control circuit 32 controls the efficiency with which the light 10f is coupled to the light 10g propagating through the waveguide layer 7d, that is, the input coupling efficiency, by adjusting the voltage applied to the electrode 9A. The voltage applied to the electrode 9C is used to control the radiation angle. The control circuit 32 controls the direction of the light 10 h emitted from the grating 8 c to the outside by adjusting the voltage applied to the electrode 9 C. As described above, a part of the light 10 a emitted from the light source 1 passes through the polarization rotator 5 while the light source 1 emits the light 10 a and is reflected by the optical waveguide element 7. Through the polarization splitter 4 and detected by the light detector 12. Therefore, the maximum value of the amount of light detected by the light detector 12 at the time of light emission of the light source is proportional to the efficiency of light of the incident light which can not be input to the grating 8 a. Therefore, the voltage applied to the electrode 9A is controlled to minimize the maximum value of the detected light amount at the time of light emission of the light source. The control circuit 32 minimizes the maximum value of the light quantity of the light detected by the light detector 12 by controlling the voltage applied to the electrode 9A while the light source 1 emits the light 10a. This operation records the local maxima in time series, compares the change of the local maximum at each control cycle of the voltage applied to the polarization rotator 5 by the control circuit 31, and analyzes the direction of the minimization. It will be.

FIG. 16A and FIG. 16B show the relationship of the time lapse of the control signal of the polarization rotator 5, the output light quantity of the light source 1 and the light quantity detected by the light detector 12 in the first embodiment. Compared to the example shown in FIG. 16A, in the example shown in FIG. 16B, the frequency signal is superimposed on the rectangular pulse.

In the example shown in FIG. 16A, the oscillation signal from the control circuit 30 that controls the oscillation of the light source 1 changes, for example, as a rectangular pulse having a width of 10 ns every Δ = 250 ns. The signal waveform 16a, the signal waveform 16a1, and the signal waveform 16a2 correspond to the output light quantity of the light pulse emitted from the light source 1 by the control signal of the rectangular pulse. The pulse oscillation every 250 ns becomes 120,000 pulses in one frame of 30 ms. This corresponds to scanning a range of 90 degrees × 30 degrees at a pixel resolution of 600 × 200 (= 120,000) if the resolutions in the horizontal direction and the vertical direction are equal.

The control signal 17a, the control signal 17a1, and the control signal 17a2 from the control circuit 31 that controls the polarization are also switched in synchronization with the signal waveform 16a that is the pulse signal, the signal waveform 16a1, and the signal waveform 16a2. For example, the polarization rotation angle is controlled as follows. First, the polarization rotation angle φ is set in the time range of the rectangular pulse of the signal waveform 16a, and the polarization rotation angle π / 2-φ is set in the time range between the rectangular pulse of the signal waveform 16a and the rectangular pulse of the signal waveform 16a1. The polarization rotation angle in the time range between the rectangular pulse of the signal waveform 16a and the rectangular pulse of the signal waveform 16a1, ie, the polarization rotation angle at the time of detection, is generally π / 2−φ + nπ, where n is an integer. n is determined so as to minimize the absolute value of the polarization rotation angle. In the rectangular pulse of the signal waveform 16a1, the variation δ (= πΔ / 2T) corresponding to beam scanning is added, and the polarization rotation angle φ + δ is obtained in the time range of the rectangular pulse of the signal waveform 16a1, and the rectangular pulse and signal of the signal waveform 16a1 are The polarization rotation angle π / 2-φ-δ is obtained in the time range between the rectangular pulse of the waveform 16a2. In the rectangular pulse of the signal waveform 16a2, a change amount δ corresponding to beam scanning is added, and the polarization rotation angle φ + 2δ is obtained in the time range of the rectangular pulse of the signal waveform 16a2. During T = 2 ms, make a 1/4 rotation around axis L. The polarization angle of the forward light between the polarization rotator 5 and the object is φ, φ + δ, and φ + 2δ for the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2, respectively. The polarization angle of return light between the polarization rotator 5 and the polarization spectroscope 4 is 2φ, 2 in the time range of the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2, respectively. (Φ + δ) and 2 (φ + 2 δ), and π / 2 in the other time range.

In the example shown in FIG. 1A, light emitted according to the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2 emits the cylindrical body 6 as a parallel beam 10i. Reflected light from the outside world returns to a time range outside the rectangular pulse. Therefore, the polarization direction of the reflected light passes through the polarization rotator 5 and is rotated by 90 degrees as compared with the time of light emission. The reflected light whose polarization direction has been rotated by 90 degrees is detected by, for example, the signal waveform 18 a and the signal waveform 18 a 1 by the photodetector 12 through the polarization spectroscope 4. The time interval 19a between the end of the signal waveform 16a and the signal waveform 18a and the time interval 19a1 between the end of the signal waveform 16a1 and the signal waveform 18a1 are called TOF signal (Time-of-Flight) signal. The TOF signal may be a time interval between the front ends. Based on this time difference, the distance to an object in the outside world can be calculated. For example, when the time delay of reflected light is 250 ns, the distance to the object is 37.5 m. The model shown in FIG. 16A can measure up to 37.5 m.

On the other hand, among the light of the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2, the component reflected by the optical waveguide element 7 passes again through the polarization rotator 5 and the polarization angle Are respectively rotated by 2φ, 2 (φ + δ) and 2 (φ + 2δ) compared to the time of light emission, and detected as a signal waveform 20a, a signal waveform 20a1 and a signal waveform 20a2 by the photodetector 12 through the polarization spectroscope 4 Be done. Among the detection signals, for example, the signal waveform 20a, the signal waveform 20a1, and the signal waveform 20a2 in the time range of the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2 are extracted The possible signal is the extraction detection signal 20, which is represented by a solid line. The time range of the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2 corresponds to the light emission time of the light source. As a reference, the polarization rotation angle in the time range of the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2 is extracted and drawn by a broken line. The period is T = 2 ms of the control signal of polarization rotation. The polarization rotation angle changes from 0 degrees to 90 degrees for each period T. On the other hand, the extraction detection signal 20 draws a curve of a square of sin with a period T. The signal waveform 20a, the signal waveform 20a1, and the signal waveform 20a2 correspond to the extraction detection signal 20A, the extraction detection signal 20A1, and the extraction detection signal 20A2, respectively, on the extraction detection signal 20.

The minimal point 20R on the extraction detection signal 20 corresponds to the start or end point of the period of the polarization rotation control signal. The maximum point 20P corresponds to an intermediate point between the start point and the end point of the control signal of polarization rotation. That is, the distance between the minimum point 20R and the maximum point 20P is equal to 45 degrees. In other words, the rotation angles of the control signal of polarization rotation and the detection signal coincide with each other. When the polarization rotator 5 is a Faraday rotator, in the magnetic glass rod 5a constituting it, physical property values such as the Verdet constant given to the Faraday effect are changed by the change of the temperature and / or the wavelength. When the characteristics of the polarization rotator 5 are out of order, the polarization is not rotated according to the control signal. For example, when the rotational sensitivity of the polarization to the applied voltage decreases, the extraction detection signal 20 extends with respect to the time axis, as represented by a dashed dotted line shown in FIG. 16A. In this case, minimum point 20R ₀ on extraction detection signal 20 is shifted from the start or end of the control signal of the polarization rotation, the distance between the minimum point 20R ₀ and maximum point 20P ₀ deviates from 45 degrees. In other words, the rotation angles of the control signal of polarization rotation and the detection signal do not match. In order to solve this problem, the control circuit 31 detects the local minimum 20R and the local maximum 20P in each cycle from the extraction detection signal 20. The minimum point 20R corresponds to the start or end point of the period of the polarization rotation control signal. The time interval between the minimum point 20R and the maximum point 20P is controlled such that the polarization rotation angle is 45 degrees. The polarization rotation angle of 45 degrees is 1/2 of 90 degrees, which is the period of the control signal of polarization rotation. This operation is performed every control period (T) of the voltage applied to the polarization rotator 5 by the control circuit 31.

The maximum value 20P of the detection signal 20 in the time range of the rectangular pulse of the signal waveform 16a, the rectangular pulse of the signal waveform 16a1, and the rectangular pulse of the signal waveform 16a2 is proportional to the efficiency of the input light which can not be input. Therefore, the output value of the maximum value 20P is used as a control signal when controlling the voltage applied to the electrode 9A in order to maximize the input coupling efficiency. The smaller the maximum value 20P, the higher the input efficiency. The control circuit 32 adjusts the voltage applied to the electrode 9A so that the maximum value 20P becomes smaller every cycle (T) of the voltage applied to the polarization rotator 5. Thus, the control circuit 32 controls the coupling efficiency with the light 10g in which the light 10f propagates in the waveguide layer 7d, that is, the input efficiency.

From the above, the control circuit 31, the control circuit 32, and the control circuit 34 perform the following operations.

The control circuit 31 adjusts the voltage applied to the polarization rotator 5 while the light source 1 emits the light 10 a. The control circuit 34 passes through the polarization rotator 5, is reflected by the optical waveguide element 7, passes again through the polarization rotator 5, and maximizes the amount of light detected by the photodetector 12 through the polarization splitter 4. Get the value and the local minimum. The control circuit 34 controls the rotation angle of the polarization direction 11 e of the light 10 e that has passed through the polarization rotator 5 by comparing the time positions of the maximum value and the minimum value described above. The control circuit 32 adjusts the voltage applied to the electrode 9A by comparing the change in the maximum value described above, and controls the input efficiency of the light 10g propagating through the waveguide layer 7d.

Incidentally, as in the example shown in FIG. 16A, when the time interval 19a is made time interval 19a ₀ long, rectangular pulse signal waveform 18a is the signal waveform 16a1, and interrupts between the rectangular pulse of the signal waveform 16a2, the signal waveform 18a It will be ₀ . As a result, it may be determined between the signal waveform 18a ₀ and the signal waveform 18a1 difficult. At this time, as shown in FIG. 16B, the high frequency signal is superimposed on the oscillation signal of the light source 1 and the intensity modulation signal of the high frequency is put on the output light amount to discriminate the frequency between the adjacent pulse waveform 16A and the pulse waveform 16A1. Be As the frequency differentiation, for example, a high frequency signal is superimposed on the pulse waveform 16A and the pulse waveform 16A2, and a low frequency signal is superimposed on the pulse waveform 16A1.

The superimposed signal also remains in the detection signal 18A and the detection signal 18A1 obtained in this manner. When the detection circuit 33 includes a filter circuit, the detection signal 18A and the detection signal 18A1 can be separated from the superposition signal by processing the superposition signal by the filter circuit. The filter circuit functions as a high pass filter (HPF) or a low pass filter (LPF). For example, the detection signals 18A, and the detection signal 18A1, are respectively converted signal 18H by multiplying the high-pass filter, and the signal 18H _0. Detection signals 18A, and the detection signal 18A1, are respectively converted signal 18L is multiplied to a low pass filter, and the signal 8L _0. The signal 18E is obtained from the difference between the signal 18H minus the signal 18L. A signal 18L ₀ from both difference obtained by subtracting from the signal 18H _0, signal 18E ₀ is obtained. By determining a positive or negative signal 18E and the signal 18E _0, it is possible to identify whether the detection signal 18A corresponds to either of the pulse waveform 16A and pulse waveform 16A1. As a result, it is possible to reliably measure the time interval 19a ₀ and the time interval 19a1. The model shown in FIG. 16B allows measurements up to 75 m. If the frequency of the pulse waveform 16A2 can also be differentiated, the measurement distance can be further extended. The processing of the superimposed signal by such a filter circuit can also be applied to a conventional optical device that measures the distance of an object.

From the above, the control circuit 30 and the control circuit 34 perform the following operation.

The control circuit 30 causes the light source 1 to sequentially emit the light pulse of the pulse waveform 16A and the light pulse of the pulse waveform 16A1 on which intensity modulation signals of different frequencies are superimposed.

The control circuit 34 outputs a part of the light pulse of the pulse waveform 16A and a part of the light pulse of the pulse waveform 16A1 which are emitted from the light waveguide element 7 to the light detector 12 and reflected by the object and enter the light waveguide element 7 Is detected, and a detection signal 18A corresponding to a partial amount of the light pulse of the pulse waveform 16A and a detection signal 18A1 corresponding to a part of the light pulse of the pulse waveform 16A1 are separated and output.

As shown in FIG. 14A, the voltage applied to the electrode layer has a cycle of 90 degrees. Therefore, four voltage distribution patterns are obtained in one rotation. This voltage distribution pattern shows rotational motion at the response speed of the liquid crystal. The response speed of light emission by the light source 1 and the rotation speed of polarization by the polarization rotator 5 far exceed the response speed of the liquid crystal. Therefore, the light emission and the rotation of polarization can be controlled independently in each of the plurality of directions corresponding to the voltage distribution pattern. For example, light can be emitted in two directions at a time to scan the beam and detect light reflected from the two directions. The two directions are, for example, the direction in the range of -45 to 45 degrees and the direction in the range of 45 to 135 degrees.

FIG. 16C is a diagram showing the relationship of time passage of the control signal of the polarization rotator 5, the output light quantity of the light source 1, and the detection light quantity of the light detector 12 in the case of overlapping scanning.

In the example shown in FIG. 16C, the oscillation signal from the control circuit 30 that controls the oscillation of the light source 1 changes as, for example, a rectangular pulse having a width of 10 ns every 250 ns in a single direction. The signal waveform 16a, the signal waveform 16a1, and the signal waveform 16a2 correspond to the output light quantity of the light pulse emitted from the light source 1 by the control signal of the rectangular pulse. The control signal 17a, the control signal 17a1, and the control signal 17a2 from the control circuit 31 that controls the polarization are also switched in synchronization with the signal waveform 16a, the signal waveform 16a1, and the signal waveform 16a2, which are pulse signals. For example, the polarization rotation angle is controlled as follows. The rectangular pulse of the signal waveform 16a has the polarization rotation angle φ in the time range of the rectangular pulse of the signal waveform 16a, and the polarization rotation angle π / in the time range between the rectangular pulse of the signal waveform 16a and the rectangular pulse of the signal waveform 16a1. It becomes 2-φ. The rectangular pulse of the signal waveform 16a1 has a polarization rotation angle φ + π / 2 in the time range of the rectangular pulse of the signal waveform 16a1, and the polarization rotation angle in the time range between the rectangular pulse of the signal waveform 16a1 and the rectangular pulse of the signal waveform 16a2. It becomes-phi + pi. In the rectangular pulse of the signal waveform 16a2, the amount of change δ corresponding to the beam scanning is added, and the polarization rotation angle φ + δ is obtained. The signal waveform 16a and the signal waveform 16a2 correspond to light emission within a field of view ranging from -45 degrees to 45 degrees, and the signal waveform 16a1 corresponds to light emission within a field of view ranging from 45 degrees to 135 degrees.

In the example shown in FIG. 1A, in the time range of the rectangular pulse of the signal waveform 16a, the light 10i is aberration-corrected and emits the cylindrical body 6 within the field of view in the range of -45 degrees to 45 degrees. Light reflected from the outside world is returned outside the time range of the rectangular pulse of the signal waveform 16a. The polarization direction of the reflected light is rotated by 90 degrees through the polarization rotator 5. Thereafter, the reflected light is separated by the polarization spectroscope 4 toward the light detector 12 and detected by the light detector 12 as a signal waveform 18 a. The time interval 19a between the end of the signal waveform 16a and the signal waveform 18a is a TOF signal. This makes it possible to detect the distance to an object within the field of view in the range of -45 degrees to 45 degrees.

Similarly, even in the time range of the rectangular pulse of the signal waveform 16a1, the light 10i is aberration-corrected and emits the cylindrical body 6 within the field of view in the range of 45 degrees to 135 degrees. Reflected light from the outside world returns outside the time range of the rectangular pulse of the signal waveform 16a1. The polarization direction of the reflected light is rotated by 90 degrees through the polarization rotator 5. Thereafter, the reflected light is separated by the polarization spectroscope 4 toward the light detector 12 and detected by the light detector 12 as a signal waveform 18a1. The time interval 19a1 between the end of the signal waveform 16a1 and the end of the signal waveform 18a1 is a TOF signal. This makes it possible to detect the distance to an object within the field of view in the range of 45 degrees to 135 degrees.

For example, when the time delay of reflected light is 250 ns, the distance to the object is 37.5 m. In the model shown in FIG. 16C, measurements up to 37.5 m are possible in the range of -45 degrees to 135 degrees, ie an angle range of 180 degrees.

The patterning of the electrodes shown in FIGS. 8B, 10A, and 10C may be formed not on the transparent electrode layer 7g side but on the reflective layer 7b side. Furthermore, the guided light 10g excited by the grating 8a may be in the TM mode. When a liquid crystal element is used as the polarization rotator 5, high-speed response can not be achieved as with a Faraday rotator. For this reason, it is impossible to switch the polarization angle at high speed synchronized with the on / off of the light emission as shown in FIG. 16A. However, if a half mirror is used as the polarization spectroscope 4, reflected light from the outside can be detected without switching the polarization angle. When a quarter wave plate is used instead of the polarization rotator 5, circularly polarized light is incident on the grating 8a. Therefore, the guided light 10g is excited uniformly in all deflection directions. Only a part of the excitation light is aberration corrected, and the light utilization efficiency drops to a fraction. Also in this case, if a half mirror is used for the polarization spectroscope 4, reflected light from the outside can be detected.

Therefore, according to the present embodiment, it is possible to emit the narrowed laser light having a spread angle of 0.1 degree or less toward the external object. At that time, the outgoing beam can be scanned at a moving image speed of 30 frames or more per second within the field of view of 90 degrees in the horizontal direction and 30 degrees in the vertical direction. Furthermore, it is possible to selectively receive or detect only the light having the same wavelength and phase as the reflected light from the object by removing the stray light. Also, the detected light can be converted into accurate two-dimensional distance information of the object in the field of view. Three-dimensional positional relationship can be obtained from two-dimensional distance information.

Second Embodiment
FIG. 17A and FIG. 17B are diagrams schematically showing the pattern of the transparent electrode layer in the second embodiment.

In the example shown in FIG. 17A, the voltage applied to the divided electrode layers has a cycle of 120 degrees. For example, the same voltage is applied to the electrode 9B1, the electrode 9B25, and the electrode 9B49, and the same voltage is applied to the electrode 9B2, the electrode 9B26, and the electrode 9B50. The voltage applied to the electrode within the angle range of 120 degrees exhibits a high and low voltage distribution pattern under the condition for correcting the aberration. The voltage distribution pattern rotates in synchronization with the rotation angle φ of the polarization by the polarization rotator while maintaining the pattern shape. In the division method shown in FIG. 17A, the response speed of light emission by the light source 1 and the rotation speed of polarization by the polarization rotator 5 far exceed the response speed of the liquid crystal. For this reason, it is possible to control emission and polarization rotation independently in each of the three directions corresponding to the voltage distribution pattern. Therefore, using the method shown in FIG. 16C, light can be emitted in three directions at a time, and reflected light from three directions can be detected.

In the example shown in FIG. 17B, the electrodes 9B are equally divided in the radial direction by 4 degrees in the rotational direction, and are divided into 90 pieces of electrodes 9B1 to 9B90. The applied voltage to the divided electrode layers has a period of 72 degrees. For example, the same voltage is applied to the electrode 9B1, the electrode 9B19, the electrode 9B37, the electrode 9B55, and the electrode 9B73. The same voltage is applied to the electrode 9B2, the electrode 9B20, the electrode 9B38, the electrode 9B56, and the electrode 9B74. The voltage applied to the electrode within the 72 ° angle range exhibits a high and low voltage distribution pattern under the condition for correcting the aberration. The voltage distribution pattern rotates in synchronization with the rotation angle φ of the polarization by the polarization rotator while maintaining the pattern shape. In the division method shown in FIG. 17B, light emission and polarization rotation can be controlled independently in each of the five directions corresponding to the voltage distribution pattern. Therefore, light can be emitted in five directions at a time and reflected light from five directions can be detected using the method shown in FIG. 16C.

As can be seen from FIGS. 1A and 1B, the path of the light beam after the light 10f acts 180 degrees symmetrically including the return path. In the first embodiment, as shown in FIG. 14A to FIG. 14C, the aberration correction is also realized with 180 degree symmetry. As a result, as reflected signals from the outside world, two kinds of signals from within the field of view in the range of -45 to 45 degrees corresponding to the front and in the field of range of 135 to 225 degrees corresponding to the rear overlap Come back. Light from two diagonally located directions is obtained from the same emission. In this case, the two types of signals can be separated, for example, by comparison with images obtained in other imaging systems and by applying image processing. On the other hand, in the division method shown in FIGS. 17A and 17B, the two voltage distribution patterns located on the opposite side by 180 degrees are different. As a result, although aberration correction is performed on the one hand, large aberrations remain in the diagonal direction. For this reason, the phase correction is also asymmetrical, and the detection signals do not overlap. Therefore, the processing of the perspective image can be simplified as compared with the first embodiment.

Third Embodiment
FIG. 18 is a perspective view schematically showing the structure of an optical device and the path of light in the third embodiment. The cross-sectional structure of the optical waveguide device 7 is the same as that shown in FIG. 1B. In the third embodiment, the polarization rotator 5 in the first embodiment is replaced by the quarter wave plate 4a and the half mirror 4b, the control circuit 31 is omitted, and the polarization spectroscope 4c, the photodetector 12A and the light detection 12B is newly added. Other than that is the same as that of the first embodiment, and the overlapping description will be omitted.

FIG. 19A shows the rotation angle of the voltage distribution pattern of the electrode 9B, the output light quantity of the light source 1, the light quantity P0 detected by the light detector 12A, the light detector 12B, and the light detector 12 in the third embodiment; And a detected light amount P45, and a relationship between time progress of a normalized difference signal of the detected light amount P0, the detected light amount P90, and the detected light amount P45.

FIG. 19B is a diagram showing the relationship between the divided region of the electrode 9B and the direction of the horizontal scanning beam in the third embodiment. FIG. 19C is a diagram showing a relationship between horizontal and vertical scanning by laser light corresponding to divided areas of the electrode 9B area, and the position between scanning light beams.

The optical apparatus according to the third embodiment includes a light source 1, a collimator lens 2a, a reflection mirror 3, a polarization spectroscope 4, a quarter wavelength plate 4a, a half mirror 4b, a polarization spectroscope 4c, A lens 2b, a cylindrical body 6, an optical waveguide element 7, a control circuit 30, and a control circuit 32 are provided. The polarization spectroscope 4, the quarter wavelength plate 4a, the half mirror 4b, the condenser lens 2b, the cylindrical body 6, and the optical waveguide element 7 are disposed with the axis L as a central axis.

In the example shown in FIG. 18, the light source 1 emits a laser beam 10a which is linear polarized light of wavelength λ. The light 10a becomes collimated light 10b by the collimator lens 2a, is reflected by the reflection mirror 3 to become light 10c incident on the polarization spectroscope 4, and transmits the polarization spectroscope 4 to become light 10d. The polarization spectroscope 4 is, for example, a polarization beam splitter. A beam shaping prism may be inserted between the collimating lens 2 a and the reflection mirror 3 to convert the distribution of the laser light 10 a spreading in an ellipse into a circle. Light 10d will become 1/4 light 10d ₀ circularly polarized light transmitted through the wavelength plate 4a, and enters the half mirror 4b, becomes the light 10e and half is transmitted therethrough. The light 10 e passes through the condenser lens 2 b along the central axis L, and enters the cylindrical body 6 which is a transparent member having a refractive index n ₀ and a radius r ₀ . The central axis L is located on the optical path of the light 10 e that has passed through the half mirror 4 b and can be said to be an axis along the optical path. Circularly polarized light is incident on the grating 8a. Therefore, the guided light 10g is excited uniformly in all deflection directions.

The paths of light after the light 10e are the same as in the first embodiment in both the forward and backward paths. Therefore, the description is omitted. After reflecting the surface of the object in the external world, light 10E was reverse to the position of the half mirror 4b in the return path, half is reflected by the half mirror 4b, becomes light 10E _0, reflected by the polarization spectrometer 4c light 10E ₁ and then branches into a transmitted light 10E _2, are detected by a photodetector 12A and the photodetector 12B. The polarization spectroscope 4c is, for example, a polarization beam splitter. Reflected light 10E ₁ is S-polarized component of the light 10E _0, transmitted light 10E ₂ is a P-polarized component of the light 10E _0.

Among the light 10E, components 10D ₀ transmitted through the half mirror 4b is transmitted through the 1/4-wave plate 4a, a portion is reflected polarization spectroscope 4, is detected by the photodetector 12. The light detector 12, the light detector 12 A, and the light detector 12 B include a detection circuit 33. The detection signal is processed by the detection circuit 33. The surface normal of the reflecting surface of the half mirror 4b and the surface normal of the reflecting surface of the polarization splitter 4 may not be parallel, and for example, they are inclined at 45 degrees. For example, only the configuration from the light source 1 to the 1⁄4 wavelength plate 4a may be rotated 45 degrees around the axis L. In this case, of the light 10E which is return light, light with a direction of 0 ° orthogonal to the polarization corresponding to the electric field vector is detected by the photodetector 12A, and light with a direction of 90 ° orthogonal to the polarization is a photodetector Light detected by 12 B and in a 45 degree direction orthogonal to the polarization is detected by the light detector 12.

In the example shown in FIG. 19A, the oscillation signal from the control circuit 30 that controls the oscillation of the light source 1 changes, for example, as a rectangular pulse having a width of 10 ns every Δ = 250 ns. Correspondingly, pulsed light of the signal waveform 16a and pulsed light of the signal waveform 16a1 are emitted. The pulse oscillation every 250 ns becomes 120,000 pulses in one frame of 30 ms. In synchronization with this pulse signal, the amount of change δ (= 2πΔ / 5T) corresponding to beam scanning is added to the rotational angle of the voltage applied to the electrode 9B, and the voltage distribution pattern of the electrode 9B is for T = 2 ms , 1/5 rotation around the axis L.

In the example shown in FIG. 19B, the electrode 9B is divided into five fan-shaped regions B1, B2, B3, B4, and B5. In each of the regions, guided light for beam scanning propagates. Region B1, region B2, region B3, region B4, and region B5 have φ = -36 degrees to 36 degrees, 36 degrees to 108 degrees, 108 degrees to 180 degrees, 180 degrees to 252 degrees, and 252 degrees to 324, respectively. It is responsible for the horizontal scanning range in the range of degrees.

FIG. 19C schematically shows horizontal and vertical scanning of laser light in each of the area B1, the area B2, the area B3, the area B4, and the area B5. A voltage distribution pattern for aberration correction is formed in a range of ± 36 degrees centered on the direction connecting center O and points b1, b2, b3, b4 and b5 shown in FIG. 19B. Ru. As a result of the aberration correction, parallel light beams scan the positions of point b1, point b2, point b3, point b4 and point b5 shown in FIG. 19C. The point b1, the point b2, the point b3, the point b4, and the point b5 move in each area while maintaining an angular difference of 72 degrees. That is, the point b1 shown in FIG. 19C scans the area B1 corresponding to the range of φ = −36 degrees to 36 degrees. Similarly, the points b2, b3, b4 and b5 also synchronously scan the areas B2, B3, B4 and B5, respectively. The horizontal scan shown in FIG. 19C can also be viewed as the 360 degree range being scanned continuously. When the point b1 crosses the boundary between the area B1 and the area B2, the scanning line at the point b1 is switched to the scanning line at the point b2. That is, the point itself continuously scans the 360 ° section, but the name in the figure changes according to the area.

The polarization direction of the light 10E reflected by the object and reversely traveled to the position of the half mirror 4b differs among the area B1, the area B2, the area B3, the area B4, and the area B5. The light in the regions B1, B2, B3, B4 and B5 has polarizations centered at φ = 90 degrees, 162 degrees, 234 degrees, 306 degrees and 18 degrees, respectively. Specifically, in the xy plane shown in FIG. 19B, the polarization direction of light is orthogonal to the azimuth Ob1 in the area B1, orthogonal to the azimuth Ob2 in the area B2, and orthogonal to the azimuth Ob3 in the area B3. In the area B4, it is orthogonal to the azimuth Ob4, and in the area B5, it is orthogonal to the azimuth Ob5.

In FIG. 19A, the time course of the detected light amount P0, the detected light amount P90, and the detected light amount P45 in the light detector 12A, the light detector 12B, and the light detector 12 is shown. Further, in FIG. 19A, return lights from the area B1, the area B2, the area B3, the area B4, and the area B5 are simultaneously detected within a time range of 250 ns after the emission of the pulsed light 16a. The signal waveform 20a, the signal waveform 20a1, the signal waveform 20b, the signal waveform 20b1, the signal waveform 20c, and the signal waveform 20c1 can not be input to the grating 8a, and are detection signals of light reflected and returned as it is.

For example, the return light from area B1, area B2, area B3, area B4 and area B5 is signal waveform 18a ₁ , signal waveform 18a ₂ , signal waveform 18a ₃ , signal waveform 18a ₄ , respectively, by photodetector 12A. and it is detected as a signal waveform 18a _5. By the photodetector 12B, region B1, the area B2, the region B3, the region B4, and return light from the region B5, respectively the signal waveform 18b _1, the signal waveform 18b _2, the signal waveform 18b _3, the signal waveform 18b _4, and the signal It is detected as a waveform 18b _5. Return light from the regions B1, B2, B3, B4, and B5 is signal waveforms 18c ₁ , 18c ₂ , 18c ₃ , 18c ₄ , and 18c ₄ by the photodetector 12, respectively. It is detected as a waveform 18c _5. From their sum signal 18a ₁ + 18b ₁ + 18c ₁ , sum signal 18a ₂ + 18b ₂ + 18c ₂ , sum signal 18a ₃ + 18b ₃ + 18c ₃ , sum signal 18a ₄ + 18b ₄ + 18c ₄ , and sum signal 18a ₅ + 18b ₅ + 18c ₅ respectively The TOF signal of the return light from the area B1, the area B2, the area B3, the area B4, and the area B5 is detected. Region B1, the area B2, the region B3, the return light TOF signals from the region B4, and regions B5, respectively signals 19a _1, signal 19a _2, signals 19a _3, signals 19a _4, and a signal 19a _5. The light amount of the sum signal is used up to 3/4 of the light amount of the light 10E.

From the three detected light amounts, three normalized difference signals (P0-P90) / (P0 + P45 + P90), normalized difference signals (P0-P45) / (P0 + P45 + P90), and normalized difference signals (P90-P45) / ( P0 + P45 + P90) is generated. As the n from 1 5 integer, the signal 18e _n, signals 18f _n, and the signal 18 g _n are respectively signals 20a _n, it is generated from the signal 20b _n, and the signal 20c _n.

In the time range of 250 ns, five signals corresponding to each of the regions B1 to B5 are detected. At that time, it is determined which signal corresponds to which region. Each of the five signals is based on reflections from objects with different distances or reflectivities. Therefore, the correspondence between the signal and the region can not be determined from the magnitude relationship between the five signals. On the other hand, the magnitude relationship between the detected light amount P0, the detected light amount P90, and the detected light amount P45 is based on the same reflection. Therefore, if it is the said magnitude correlation, it can apply to determination. In the present embodiment, three standardized difference signals are used for the determination.

FIG. 20A, FIG. 20B, FIG. 20C, FIG. 20D, and FIG. 20E respectively show the region B1, the region B3, the region B5, the region of the electrode 9B when one light beam is scanned in the range of -36 degrees to 324 degrees. It is a figure which shows the behavior of the detection difference signal on the basis of the returned light in B2 and area | region B4. For example, FIG. 20A shows the normalized difference signal (P0-P90) / (P0 + P45 + P90), the normalized difference signal (P0-P45) / (P0 + P45 + P90), and the normalized difference signal (P90-P45) / (P0 + P45 + P90) in the region B1. And the horizontal scanning azimuth angle φ. From the difference in magnitude relationship of the difference signal, it can be classified into six types of divisions of division A, division B, division C, division D, division E, and division F in the range of 180 degree cycle. As shown in FIG. 20B, FIG. 20C, FIG. 20D, and FIG. 20E, the difference signal waveform and the six types of section ranges shift in azimuth by −36 degrees each. From the example shown in FIG. 19B, the region B1 is in the range of φ = −36 degrees to φ = 36 degrees. In the example shown in FIG. 20A, if the ray is in the range of φ = −36 degrees to φ = 36 degrees, the ray is a scanning line at point b1. At that time, scanning lines by the light ray b3, the light ray b5, the light ray b2 and the light ray b4 draw signal curves in the range of -36 degrees to 36 degrees in the example shown in FIGS. 20B, 20C, 20D and 20E respectively. . For example, from the example shown in FIG. 19B, the region B2 is in the range of φ = 36 degrees to φ = 108 degrees. In the example shown in FIG. 20D, the range of φ = −36 degrees to φ = 36 degrees corresponds to the movement of the scanning line at point b2 that is 72 degrees away from point b1. Therefore, if the light beam is caused by the scanning line b1, the normalized difference signal draws a curve in the range of φ = −36 degrees to φ = 36 degrees in the example shown in FIG. 20A. Therefore, equation (21) holds.

In the examples shown in FIGS. 20C, 20D, and 20E, the magnitude relationship of any difference signal does not satisfy Formula (21) within the range of φ = −36 degrees to φ = 36 degrees. Thus, the signals in the area shown in FIG. 20A can be differentiated from the signals in the areas shown in FIGS. 20C, 20D, and 20E. Thereby, the light ray b1 can be separated into the light ray b5, the light ray b2, and the light ray b4. On the other hand, in the range of φ = −22 degrees to φ = 9 degrees, the section A shown in FIG. 20B overlaps the section A shown in FIG. 20A. As a result, in Formula (21), it can not classify. However, in this overlapping section, the normalized difference signal (P0-P45) / (P0 + P45 + P90) shown in FIG. 20A is larger than the normalized difference signal (P0-P45) / (P0 + P45 + P90) shown in FIG. 20B. Thus, the signal shown in FIG. 20B can be distinguished from the signal shown in FIG. 20A. Thereby, the light ray b1 can be separated from the light ray b3. Therefore, it is possible to specify which of the five signals shown in FIG. 19A corresponds to the area B1. The same relationship holds for the other regions B2, B3, B4 and B5. As a result, it is possible to distinguish all of the five detection signals corresponding to which region or which scan line.

Fourth Embodiment
21A and 21B are a perspective view and a cross-sectional view schematically showing the configuration of an optical device and the path of a light beam, respectively, in the fourth embodiment.

In the fourth embodiment, the reflection mirror 3, the polarization spectroscope 4c, the photodetector 12, the photodetector 12A, and the photodetector 12B in the third embodiment are omitted, and instead the photodetector 12a and the photodetector 12b is added, the cylindrical body 6 is changed to a truncated cone prism 6T, and a substrate 7F including a truncated cone-like hollow is inserted between the transparent flat substrate 7f and the truncated cone prism 6T. The incident light 10c corresponds to the parallel light 10b shown in FIG. 21A, and its polarization is S wave. Other than that is the same as the third embodiment. Therefore, duplicate explanations are omitted.

The optical apparatus according to the fourth embodiment includes a light source 1, a collimator lens 2a, a polarization splitter 4, a quarter wavelength plate 4a, a half mirror 4b, a condenser lens 2b, a truncated cone prism 6T, and a cone. Substrate 7F including a trapezoid hollow, optical waveguide device 7, photodetector 12a, photodetector 12b, detection circuit 33a, detection circuit 33b, control circuit 30, control circuit 32, and control circuit 34 And The polarization spectroscope 4, the quarter wavelength plate 4a, the half mirror 4b, the condenser lens 2b, the truncated cone prism 6T, the substrate 7F including a truncated cone, and the optical waveguide element 7 are disposed with the axis L as a central axis Be done.

In the example shown to FIG. 21A, the light source 1 radiate | emits the laser beam 10a which is a linear polarization of wavelength (lambda). The laser beam 10a becomes parallel light 10b of S polarization by the collimator lens 2a, and is reflected by the polarization spectroscope 4 to become light 10d. The polarization spectroscope 4 is, for example, a polarization beam splitter. A beam shaping prism may be inserted between the collimating lens 2 a and the polarization spectroscope 4 to convert the distribution of the laser light 10 a spreading in an ellipse into a circle. Light 10d will become 1/4 light 10d ₀ circularly polarized light transmitted through the wavelength plate 4a, and enters the half mirror 4b, becomes the light 10e and half is transmitted therethrough. Light 10e passes through the condenser lens 2b along the central axis L, incident on the truncated conical prism 6T which is a transparent member having a refractive index n _0. The central axis L is located on the optical path of the light 10 e that has passed through the half mirror 4 b and can be said to be an axis along the optical path. Circularly polarized light is incident on the grating 8a. Therefore, the guided light 10g is excited uniformly in all deflection directions. The truncated cone prism 6T and the substrate 7F including a truncated cone-shaped hollow are in close contact with the transparent flat substrate 7f with the axis L as the same axis.

The path of light after the light 10 e is almost the same as in the first and third embodiments. Therefore, the description is omitted. However, the light emitted from the grating 8c is refracted through the transparent flat substrate 7f and the substrate 7F, refracts the frusto-conical hollow surface of the substrate 7F, enters the side surface of the frusto-conical prism 6T, and refracts it to the light 10h. The light is emitted from the side of the truncated cone on the opposite side to be refracted light 10i. The truncated cone-like hollow surface of the substrate 7F and the side surface of the truncated cone prism 6T have the axis L as the same axis. A blazed grating may be formed on these surfaces. In the blazed grating, a saw-like groove is formed along a direction perpendicular to the central axis L. The blazed grating causes the transmitted light to be diffracted in the vertical plane. As a result, at the side surface position of the truncated cone prism 6T, the refracted light 10j becomes the outgoing light 10i which is emitted to the outside at an angle of _θ⊥ from the horizontal surface.

In the return path after reflecting the object, half of the light 10E that has traveled the forward path back to the position of the half mirror 4b is reflected by the half mirror 4b to become light 10E ₀ , and is detected by the light detector 12a . Among the light 10E, components 10D ₀ transmitted through the half mirror 4b is transmitted through 1/4-wave plate 4a. A portion of the transmitted light 10D is transmitted through the polarization spectroscope 4 and detected as a transmitted light 10B by the photodetector 12b. The photodetector 12a includes a detection circuit 33a, and the photodetector 12b includes a detection circuit 33b. The detection signal is processed by the detection circuit 33a and the detection circuit 33b. The optical device may further comprise a control circuit 34. The control circuit 34 generates, for example, a control signal for controlling the orientation of the light source or the liquid crystal from the detection signals of the detection circuit 33a and the detection circuit 33b. Further, the control circuit 30, the control circuit 32, and the control circuit 34 may be integrated into one control circuit.

FIG. 22 is a view schematically showing propagation paths of light emitted from the grating 8 c in the case where aberration correction control is performed in the fourth embodiment. In the example shown in FIG. 22, the upper part shows a plan view, the middle part shows a perspective view, and the lower part shows a cross-sectional view. As shown in FIG. 22, the waveguided light 10g propagating in the waveguide layer 7d and the waveguided light 10g ₀ exit the grating 8c, enter the side surface of the truncated cone prism 6T, refract and propagate the inside light 10h light 10h _0, becomes light 10h1, and light 10h1 _0, the light 10i emitted to the outside is refracted the frustoconical side surface of the opposite side, the light 10i _0, becomes light 10i1, and light 10i1 _0. As shown in the middle of FIG. 22, the light 10h light 10h _0, light 10h1, and light 10h1 _0, the axis L away from the center axis L along the positive direction of the x-axis "cross over. Axis L ' Is inclined relative to the central axis L. Light 10h, and light 10h ₀ is "intersect at a point F 'on, light 10h1 and 10h1 _0, the axis L" axis L shown upper. Figure 22 that intersect at a point F "on, and in the lower In the example, the cylindrical body 6 is replaced by a truncated cone prism 6 T. Thereby, the light 10 h on the outer peripheral side and the radius r ₀ of the refracting point of the light 10 h ₀ corresponding to the inclination of the axis L ′ ′ The light 10 h 1 on the inner circumferential side and the radius r ₀ ′ of the refracting point of the light 10 h ₁₀ change. As a result, it is possible to collimate the light beam after exiting the side surface of the truncated cone prism 6T.

In the fourth embodiment, a light beam passes twice through the side surface of the truncated cone prism 6T on which the blazed grating is formed. In the mode in which the light beam passes the side, the degree of freedom in design is wider than in the mode in which the bottom surface of the cylindrical body 6 in the first and third embodiments passes. Also, the light beam receives the influence of diffraction by the blaze grating twice by passing through the side surface. If a blazed grating is also formed on the truncated hollow surface of the substrate 7F, the light beam is affected by diffraction three times. By such two or more diffractions, sufficient diffraction efficiency can be obtained even if the grating pitch is large as compared with the first and third embodiments. The large pitch of the grating facilitates fabrication and increases the diffraction efficiency. A substrate 7F is generally arranged to extract the light emitted from the grating 8a into the air. On the other hand, if light can be extracted, the substrate 7F can be omitted. The configuration in which the substrate 7F is provided with a truncated cone-like hollow can take out the radiation from the grating 8a into the air regardless of the radiation angle. Therefore, the degree of freedom in design is broadened.

FIG. 23A shows the rotation angle of the voltage distribution pattern of the electrode 9B, the output light quantity of the light source 1, the detected light quantity Pa of the light detector 12a and the light detector 12b, the detected light quantity Pb, and the detected light quantity in the fourth embodiment. It is a figure which shows the relationship of time progress of Pa + Pb and ratio Pb / Pa.

FIG. 23B is a diagram showing the relationship between the split region of the electrode 9B and the direction of the horizontal scanning beam in the fourth embodiment. From the area B1, area B2, area B3, area B4 and area B5 of the electrode 9B, the first scanning beam at the point b1, the second scanning beam at the point b2, the third scanning beam at the point b3, the fourth scanning at the point b4 A ray and a fifth scanning ray at point b5 are emitted respectively. These five scan rays rotate equiangularly around the center O at an angle of 72 degrees to one another.

Polarization amplitude of the light 10E ₀ corresponding to the scanning beam through point bk is, ak amplitude coefficients, as azimuth or scanning angle phi, is expressed by equation (22). However, k = 1, 2, 3, 4, and 5.

Using the Jones matrix, the relationship between the polarization amplitude of the light 10E _{0 and} the polarization amplitude of the transmitted light 10B is expressed by Equation (23).

The first term of the left side represents the matrix of the polarization spectroscope 4, the second term represents the matrix of the 1⁄4 wavelength plate 4a, the third term represents the polarization amplitude of the light 10E ₀ , and the right side represents the polarization of the transmitted light 10B. Represents the amplitude.

From the equations (22) and (23), the detected light amount Pa and the detected light amount Pb at the light detector 12a and the light detector 12b are expressed by the equation (24) and the equation (25), respectively.

From Expression (24) and Expression (25), the detected light amount ratio Pb / Pa is expressed by Expression (26).

Figure 23C is a detected light intensity ratio _Pb 1 / Pa ₁ corresponding to the first scanning beam through point b1, the detection light amount ratio _Pb 2 / Pa ₂ corresponding to the second scanning beam through point b2, the third scanning light beam by point b3 The corresponding detected light amount ratio Pb ₃ / Pa ₃ , the detected light amount ratio Pb ₄ / Pa ₄ corresponding to the fourth scanning beam at the point b ₄ , and the detected light amount ratio Pb ₅ / Pa ₅ corresponding to the fifth scanning beam at the point b ₅ It is a figure which shows the relationship between the signal to show and the scanning angle (phi) which is a liquid crystal pattern rotation angle. The relationship is obtained from equation (26). In the example shown in FIG. 23C, Pb ₁ / Pa ₁ <Pb ₄ / Pa ₄ <Pb ₃ / Pa ₃ <Pb ₂ / Pa ₂ <Pb ₅ / Pa ₅ in the range from φ = 0 ° to φ = 18 ° In the range of φ = 18 degrees to φ = 36 degrees, the relationship of Pb ₄ / Pa ₄ <Pb ₁ / Pa ₁ <Pb ₂ / Pa ₂ <Pb ₃ / Pa ₃ <Pb ₅ / Pa ₅ is φ = In the range of 36 degrees to φ = 54 degrees, the relationship of Pb ₄ / Pa ₄ <Pb ₂ / Pa ₂ <Pb ₁ / Pa ₁ <Pb ₅ / Pa ₅ <Pb ₃ / Pa ₃ is obtained, and from φ = 54 degrees to φ = In the range of 72 degrees, a relationship of Pb ₂ / Pa ₂ <Pb ₄ / Pa ₄ <Pb ₅ / Pa ₅ <Pb ₁ / Pa ₁ <Pb ₃ / Pa ₃ holds. In the relationship of Pb ₂ / Pa ₂ <Pb ₅ / Pa ₅ <Pb ₄ / Pa ₄ <Pb ₃ / Pa ₃ <Pb ₁ / Pa ₁ in the range of φ = 72 ° to φ = 90 °, φ = 0 ° Pb ₁ / Pa ₁ is Pb ₂ / Pa ₂ , Pb ₂ / Pa ₂ is Pb ₃ / Pa ₃ , and Pb ₃ / Pa ₃ is Pb ₄ /, compared to the relationship from φ to 18 ° in Pa _{_{_4,}} Pb ₄ / Pa ₄ is in _{_{_{Pb 5 / Pa 5, Pb 5}}} / Pa 5 is up repeatedly in _Pb ₁ / Pa 1. Also in the angle range after that, the relation of carry-up holds. By this, all the magnitude relationships up to 360 degrees can be known. Therefore, the scanning angle φ is determined by the drive signal to the electrode 9B, and if the scanning angle φ is determined, the magnitude relationship between the five detected light amount ratios is determined. This allows the detection signal to identify any of the scanning rays.

In the example shown in FIG. 23A, the oscillation signal from the control circuit 30 that controls the oscillation of the light source 1 changes, for example, as a rectangular pulse having a width of 10 ns every Δ = 250 ns. Correspondingly, pulsed light of the signal waveform 16a and pulsed light of the signal waveform 16a1 are emitted. The pulse oscillation every 250 ns becomes 120,000 pulses in one frame of 30 ms. In synchronization with this pulse signal, the amount of change δ (= 2πΔ / 5T) corresponding to beam scanning is added to the rotational angle of the voltage applied to the electrode 9B, and the voltage distribution pattern of the electrode 9B is for T = 2 ms , 1/5 rotation around the axis L.

FIG. 23A shows the time course of the detected light amount Pa and the detected light amount Pb in the light detector 12a and the light detector 12b. Return light from the area B1, the area B2, the area B3, the area B4, and the area B5 is simultaneously detected within a time range of 250 ns after the emission of the pulse light of the signal waveform 16a. The signal waveform 20a, the signal waveform 20a1, the signal waveform 20b, and the signal waveform 20b1 can not be input to the grating 8a, and are detection signals of light reflected and returned as it is.

For example, the photodetector 12a, a region B1, the area B2, the region B3, the region B4, and return light from the region B5, respectively the signal waveform 18a _1, the signal waveform 18a _2, the signal waveform 18a _3, the signal waveform 18a ₄ , and is detected as a signal waveform 18a _5. The photodetector 12b, a region B1, the area B2, the region B3, the return light from the region B4, and the region B5, respectively the signal waveform 18b _1, the signal waveform 18b _2, the signal waveform 18b _3, the signal waveform 18b _4, and It is detected as a signal waveform 18b _5. The control circuit 34 receives an electrical signal according to the light amount Pa detected by the light detector 12a and an electrical signal according to the light amount Pb detected by the light detector 12b. The control circuit 34 generates an electrical signal according to the sum and ratio of these two electrical signals. A ₁ + b ₁ , a ₂ + b ₂ , a ₃ + b ₃ , a ₄ + b ₄ , and a ₅ + b ₅ are generated as a sum signal Pa + Pb indicating the sum of the amounts of light detected by the

light detectors

12a and 12b . The signal ratio Pb / Pa indicating the ratio of the detected light amount of the light detector 12a and the light detector 12b is b ₁ / a ₁ , b ₂ / a ₂ , b ₃ / a ₃ , b ₄ / a ₄ , and b ₅ / A ₅ is generated.

In the sum signal Pa + Pb, five signals are used as TOF signals. On the other hand, those signals are based on reflections from objects with different distances or reflectivities. Therefore, it is not possible to specify which signal corresponds to which of the regions B1 to B5 using only the sum signal. However, by adding the signal ratio Pb / Pa, from the magnitude relationship of the signal ratio, the five signals are the first scanning beam at the point b1, the second scanning beam at the point b2, the third scanning beam at the point b3, and the point b4. It is possible to specify which of the fourth scanning beam and the fifth scanning beam according to the point b5, or which signal corresponds to which of the regions B1 to B5. For example, in the example of the signal ratio shown in FIG. 23A, if the scanning angle φ is in the range of 0 ° to 18 °, five signals from the left, the first scanning beam, the second scanning beam, the third scanning beam, the fourth The scanning beam and the fifth scanning beam are in order, and if the scanning angle φ is in the range of 18 degrees to 36 degrees, the fourth scanning beam, the third scanning beam, the second scanning beam, the first scanning beam, and the fifth scanning beam It can be determined as the order of scanning rays.

Next, the control principle of the propagation direction of the guided light in the electrode 9B will be described.

FIG. 24A and FIG. 24B are diagrams schematically showing the relationship between the electrode pattern on the transparent electrode layer 7g side and the reflective layer 7b side and the applied voltage. All of the electrode pattern 40a, the electrode pattern 40b, and the electrode pattern 40c shown in FIG. 24A, and the electrode pattern 40A, the electrode pattern 40B, and the electrode pattern 40C shown in FIG. 24B are configured by three zigzag patterns extending from left to right It is done. Each zigzag pattern is isolated. A voltage signal is applied to the electrode pattern 40a, the electrode pattern 40b, and the electrode pattern 40c shown in FIG. 24A independently by the control circuit 32a, the control circuit 32b, and the control circuit 32c. Similarly, voltage signals are applied to the electrode pattern 40A, the electrode pattern 40B and the electrode pattern 40C shown in FIG. 24B independently by the control circuit 32A, the control circuit 32B and the control circuit 32C.

FIG. 24C is a view schematically showing the relationship between the configuration obtained by aligning and overlapping the electrode pattern on the transparent electrode layer side and the electrode pattern on the reflective layer side, and the applied voltage. When the transparent electrode layer 7g is on the upper side and the reflective layer 7b is on the lower side, in the zigzag patterns located in the upper and lower sides, lines formed by connecting the apexes on one side of the zigzags are in a mutually overlapping relationship. The shape of the zigzag pattern on the side of the reflective layer 7 b is a shape in which the zigzag pattern on the side of the transparent electrode layer 7 g is vertically inverted. Therefore, as shown in FIG. 24C, the electrode pattern on the transparent electrode layer 7g side and the electrode pattern on the reflective layer 7b side are aligned and overlapped have a shape in which rhombuses are continuous.

In the case of producing the electrode pattern shown in FIG. 24C on only one side, the wiring is not easy because the diamonds are isolated one by one. On the other hand, in the method of superposing the electrode pattern shown in FIG. 24A and the electrode pattern shown in FIG. 24B, since the pattern itself is a wiring, the fabrication is easy. An alternating voltage signal 41a, an alternating voltage signal 41b, and an alternating voltage signal 41c are applied to the zigzag electrode pattern 40a, the electrode pattern 40b, and the electrode pattern 40c on the transparent electrode layer 7g side, respectively. Thus, the amplitude increases in the order of the AC voltage signal 41a, the AC voltage signal 41b, and the AC voltage signal 41c. Assuming that the facing electrodes are grounded, a difference in refractive index is generated in the liquid crystal layer corresponding to the zigzag electrode pattern 40a, the electrode pattern 40b, and the electrode pattern 40c due to this amplitude gradient. The waveguided light 10g propagating from the left to the right in the waveguide layer 7d sandwiched between the electrodes is refracted downward every time it passes through the inclined pattern boundary from the optical path. An alternating voltage signal 41A, an alternating voltage signal 41B, and an alternating voltage signal 41C are applied to the zigzag electrode pattern 40A, the electrode pattern 40B, and the electrode pattern 40C on the reflective layer 7b side. As a result, the amplitude increases in the order of the AC voltage signal 41A, the AC voltage signal 41B, and the AC voltage signal 41C. Assuming that the facing electrodes are grounded, this amplitude gradient also refracts the waveguide light 10g propagating from left to right in the waveguide layer 7d sandwiched between the electrodes downward.

The AC voltage signal 41A, the AC voltage signal 41B, and the AC voltage signal 41C have opposite polarities to the AC voltage signal 41a, the AC voltage signal 41b, and the AC voltage signal 41c, respectively. Therefore, as shown in FIG. 24C, in the electrode pattern in which the transparent electrode layer 7g and the reflective layer 7b are aligned and overlapped, the AC voltage signal 41a1 and the AC voltage signal 41A1 form a signal pair, and the AC voltage signal 41b1 and the AC voltage The signal 41 B 1 forms a signal pair, and the AC voltage signal 41 c 1 and the AC voltage signal 41 C 1 form a signal pair. Since their phases are inverted, the AC voltage amplitude is doubled. Thereby, the guided light 10g can be largely refracted downward. Furthermore, as compared with the electrode patterns shown in FIGS. 24A and 24B, the frequency with which the guided light 10g crosses the pattern boundary increases. As a result, the bending of the guided light 10g is further doubled, and the variation in the bending angle due to the difference in the optical path is also improved.

Based on the principle described with reference to the examples shown in FIGS. 24A to 24C, control of the propagation direction of guided light in the fourth embodiment will be described.

FIG. 25A and FIG. 25B are diagrams schematically showing the patterns of the electrodes 9B on the transparent electrode layer 7g side and the reflective layer 7b side in the fourth embodiment, respectively. Each of the electrode pattern shown in FIG. 25A and the electrode pattern shown in FIG. 25B is configured of 60 zigzag patterns extending from the inner circumferential side to the outer circumferential side. As described above, in at least one of the reflective layer 7b and the transparent electrode layer 7g, the boundary between any two adjacent divided regions among the plurality of divided regions in the electrode 9B is a virtual one centered on the point at which the laser light is incident. Has a zigzag shape along the radial direction of the circle. Each zigzag pattern is isolated and a voltage signal is applied independently. In the example shown in FIG. 25A and FIG. 25B, adjacent zigzag patterns are in a relation in which lines formed by connecting the vertices on one side of the zigzags overlap with each other. The shape of the zigzag pattern on the side of the reflective layer 7 b is a shape in which the zigzag pattern on the side of the transparent electrode layer 7 g is inverted in the rotational direction.

FIG. 25C is a view schematically showing a configuration in which the electrode pattern on the transparent electrode layer side and the electrode pattern on the reflective layer side are aligned and overlapped. FIG. 25D is a view schematically showing the relationship between a part of the electrode pattern shown in FIG. 25C and the propagation path of the guided light 10g. As shown in FIG. 25C, the pattern of the electrode 9B in which the transparent electrode layer 7g and the reflective layer 7b are aligned and overlapped has a shape in which rhombuses are continuous. In each of the reflective layer 7b and the transparent electrode layer 7g, among the plurality of divided regions in the region 9B, the boundary between any two adjacent divided regions is a movement of a virtual circle centered on the point at which the laser light is incident. It has a zigzag shape along the radial direction. When viewed from a direction perpendicular to any of the buffer layer 7c, the waveguide layer 7d, and the liquid crystal layer 7e, the above-mentioned boundary in one of the pair of electrode layers and the above-mentioned boundary in the other have a rhombus shape. Form

Therefore, as shown in FIG. 25D, when the magnitude of the AC voltage amplitude applied to the zigzag pattern has a gradient along the rotational direction, the liquid crystal refractive index increases along the direction of the arrow 42. Thus, the propagation path of the guided light 10g propagating from the inner circumferential side to the outer circumferential side in the waveguide layer 7d can be bent to the arrow 42 side. Therefore, by controlling the voltage applied to the electrode having the shape shown in FIG. 25C, the light emitted from the grating 8c can be emitted as parallel light from the side surface of the truncated cone.

Note that the method used in any of the embodiments can be applied to the other embodiments. For example, the method described with reference to the example shown in FIG. 16A in the first embodiment can be applied to the third and fourth embodiments. That is, as in the first embodiment, for example, the signal waveform 20a which is a sum signal, the signal waveform 20a1, and the maximum value 20P of the extraction detection signal formed by extracting the signal waveform 20a2 can not be input efficiency of the incident light. Proportional to Therefore, the output value of the maximum value 20P is used as a control signal when controlling the voltage applied to the electrode 9A in order to maximize the input coupling efficiency. The smaller the maximum value 20P, the higher the input efficiency.

The method described with reference to the example shown in FIG. 16B in the first embodiment can also be applied to the third and fourth embodiments. In this case, by superimposing a high frequency signal to the oscillation signal of the light source 1, by placing a high-frequency intensity modulation signal to the output light intensity, for example even if the signal waveform 18a ₁ exceeds the time zone of the rectangular pulse of the signal waveform 16a1, which is It can be identified that the detection signal corresponds to the rectangular pulse of the signal waveform 16a. Thereby, the measurement distance can be extended.

In the third and fourth embodiments, the quarter-wave plate 4a may be a polarization conversion element that converts linearly polarized light into circularly polarized light or polarized light in a direction orthogonal to the circular tangent. Generally, linearly polarized light can be converted to light polarized in a circular tangent direction by sandwiching a nematic twist liquid crystal between a substrate aligned in the linear direction and a substrate aligned in the rotational direction. By using such a polarization conversion element, the input efficiency to the grating 8a can be doubled. As a result, it is possible to excite the TE mode guided light 10g uniformly in all deflection directions.

In the third and fourth embodiments, the half mirror 4b intervenes between the forward paths. Therefore, the light utilization efficiency at the input is reduced to half as compared to the first embodiment. On the other hand, light can be input to all declination azimuths, and return light from all azimuths can be detected, and detection signals can be separated for each azimuth. Therefore, the horizontal scanning range and detection range can be extended to 360 degrees at the same frame rate.

In the optical arrangement, the relationship between transmission and reflection of light to the polarization spectroscope 4 or the half mirror 4b may be interchanged.

According to the embodiment described above, it is possible to emit a narrowed laser beam with a spread angle of 0.1 degree or less toward an external object. At that time, the outgoing beam can be scanned at a moving image speed of 30 frames or more per second within the field of view of 360 degrees in the horizontal direction and 10 degrees in the vertical direction. The vertical field of view extends up to 30 degrees when wavelength tuning is added. Furthermore, it is possible to selectively receive or detect only the light from which the stray light is removed and the wavelength and the phase are aligned among the reflected light from the object. Also, the detected light can be converted into accurate two-dimensional distance information of the object within the field of view. Three-dimensional positional relationship can be obtained from two-dimensional distance information.

The present disclosure scans laser light horizontally and vertically toward an object scattered in a field of view, selectively receives or detects reflected light from the object, and measures a three-dimensional positional relationship of the object. Provide technology.

DESCRIPTION OF SYMBOLS 1 light source

2a collimate lens

2b condensing lens 3 reflective mirror 5 polarization splitter 5 polarization rotator 6 cylindrical body 7 light waveguide element 7a planar substrate 7b reflective layer 7c buffer layer 7d waveguide layer 7e liquid crystal layer 7f transparent planar substrate 7g

transparent electrode Layers

8a, 8b,

8c Gratings

9A, 9B, 9C

Electrodes

10a, 10b, 10c, 10d, 10e, 10h, 10i Light 10g Guided Light 10D Reversed

Light

11d,

11e Polarization Direction

30, 31, 32, 34 Control Circuit 33 Detection circuit

Claims

A light source for emitting laser light,
An optical waveguide element located on the optical path of the laser light;
A first transparent member located on the optical path and having a bottom surface facing the optical waveguide element, and a side surface that is rotationally symmetric about a virtual axis along the optical path as a central axis;
Control circuit, and
The optical waveguide device is
It includes a plurality of portions arranged along the radial direction of a virtual circle centered on the point where the laser beam is incident and has different refractive indices, and a part of the incident laser beam is used as the propagation light. A first grating for propagating in the optical waveguide element along the radial direction, and a plurality of portions disposed outside the first grating and disposed along the radial direction and having mutually different refractive indices A second grating for emitting a part of the propagated light from the optical waveguide element as an emitted light;
Including
The emitted light is incident on the first transparent member from the bottom surface or the side surface and emitted from the side surface.
Optical device.
The first grating has a concentric structure centered on the point,
An optical device according to claim 1.
The second grating has a concentric structure centered on the point,
An optical device according to claim 1.
The first transparent member has a cylindrical shape or a truncated cone shape.
An optical device according to claim 1.
The side of the first transparent member includes a third grating whose grating vector is parallel to the central axis
The optical device according to claim 4.
It further comprises a cylindrical second transparent member surrounding the first transparent member and coaxial with the central axis,
The inner and outer sides of the second transparent member include a fourth grating whose grating vector is parallel to the central axis,
The optical device according to claim 5.
The optical waveguide device further includes a transparent layer in contact with the first transparent member on the first grating and the second grating,
The transparent layer has a refractive index of 1.8 or more.
The optical device according to any one of claims 4 to 6.
The control circuit causes the light source to change the wavelength of the laser light, thereby changing the direction of the laser light emitted from the optical waveguide element.
The optical device according to any one of claims 1 to 7.
The optical waveguide element includes a first dielectric layer, a second dielectric layer on the first dielectric layer, and a third dielectric layer on the second dielectric layer,
The refractive index of the second dielectric layer is higher than the refractive index of the first dielectric layer and the refractive index of the third dielectric layer,
A group consisting of a first position between the second dielectric layer and the first dielectric layer and a second position between the second dielectric layer and the third dielectric layer The first grating and the second grating are arranged in at least one selected from
A portion of the laser beam incident on the second dielectric layer propagates in the second dielectric layer along the radial direction as the propagation light, and the second light beam is output as the emission light. Emit from the grating of
The optical device according to any one of claims 1 to 8.
The optical waveguide device further includes a reflective layer,
The first dielectric layer is disposed between the second dielectric layer and the reflective layer,
The optical device according to claim 9.
The optical waveguide device further includes a first electrode layer and a transparent second electrode layer,
The first dielectric layer, the second dielectric layer, and the third dielectric layer are disposed between the first electrode layer and the second electrode layer,
The second electrode layer is closer to the third dielectric layer than the first electrode layer,
The third dielectric layer is a liquid crystal layer containing liquid crystal,
An optical device according to claim 9 or 10.
When no voltage is applied to the liquid crystal layer, the alignment direction of the liquid crystal is perpendicular to the grating vector of the first grating or the grating vector of the second grating.
The optical device according to claim 11.
The optical waveguide device further includes, between the first grating and the second grating, a fifth grating including a plurality of portions arranged along the radial direction and having mutually different refractive indices,
When no voltage is applied to the liquid crystal layer, the alignment direction of the liquid crystal is perpendicular to the grating vector of the fifth grating.
The optical device according to claim 11.
At least one electrode layer selected from the group consisting of the first electrode layer and the second electrode layer includes a first electrode facing the first grating and a second electrode facing the second grating. Two electrodes, and a third electrode between the first electrode and the second electrode,
The third electrode includes a plurality of conductive divided regions disposed along the circumferential direction of the virtual circle,
The plurality of divided regions are mutually isolated
The optical device according to claim 11.
The control circuit controls the direction of the emitted light by controlling a voltage applied to the liquid crystal layer through the second electrode.
The optical device according to claim 14.
The control circuit controls the efficiency of coupling of the laser light from the first grating to the propagation light by controlling a voltage applied to the liquid crystal layer through the first electrode.
An optical device according to claim 14 or 15.
The control circuit sequentially applies a voltage to the divided regions facing the portion in the second dielectric layer through which the propagation light propagates among the plurality of divided regions.
The optical device according to any one of claims 14 to 16.
A polarization spectrometer,
A photodetector,
Further comprising a polarization rotator,
The polarization spectroscope and the polarization rotator are located on the optical path between the light source and the first transparent member.
The control circuit changes the polarization direction of the laser beam passing through the polarization rotator by controlling a voltage applied to the polarization rotator.
A part of light emitted from the optical waveguide element, reflected by the object, and incident on the optical waveguide element passes through the optical waveguide element, the polarization rotator, and the polarization spectroscope, and then, as detection light, Is incident on the light detector,
The light detector generates an electrical signal according to the amount of the detected light,
An optical device according to any of claims 14-17.
The control circuit acquires a time interval between the maximum value and the minimum value of the amount of the detection light detected by the light detector while the light source emits the laser light, and based on the time interval The rotation angle of the polarization direction of the laser beam having passed through the polarization rotator is controlled by adjusting the voltage applied to the polarization rotator.
An optical device according to claim 18.
A first polarization spectrometer,
A polarization converter,
A spectrometer,
And a light detector,
The light detector includes a first light detector and a second light detector,
The first polarization spectroscope, the polarization converter, and the spectroscope are located on the light path between the light source and the first transparent member.
A part of light emitted from the optical waveguide element, reflected by an object, and passed through the optical waveguide element and then incident on the spectroscope is transmitted to the first spectroscope after passing through the spectroscope and the polarization converter. As the detection light, it is incident on the first light detector,
Another part of the light incident on the spectroscope is incident on the second light detector as a second detection light after passing through the spectroscope.
The first photodetector generates a first electrical signal according to the amount of the first detection light,
The second photodetector generates a second electrical signal according to the amount of the second detection light,
An optical device according to any of claims 14-17.
The polarization converter is a quarter wave plate,
An optical device according to claim 20.
The polarization converter converts linearly polarized light into circularly polarized light.
An optical device according to claim 20.
Further comprising a second polarization spectrometer,
The light detector further includes a third light detector,
A part of the light emitted from the optical waveguide element, reflected by the object, passed through the optical waveguide element and the spectroscope, and then incident on the second polarization spectroscope,
After passing through the second polarization spectroscope, as a third detection light, it enters the second light detector,
The other part of the light incident on the second polarization spectroscope passes through the second polarization spectroscope and then enters the third light detector as fourth detection light,
The third light detector generates an electrical signal according to the amount of the fourth detection light.
An optical device according to any of claims 20-22.
The control circuit
Receiving the first electrical signal and the second electrical signal;
Generating an electrical signal according to a sum of the first electrical signal and the second electrical signal and a ratio of the first electrical signal to the second electrical signal;
22. An optical device according to claim 20 or 21.
The control circuit controls a voltage applied to the first electrode such that a local maximum of the amount of light detected by the light detector is minimized while the light source emits the laser light. ,
An optical device according to any one of claims 18 to 24.
The light detector includes a filter circuit,
The control circuit
Causing the light source to sequentially emit a first light pulse and a second light pulse on which intensity modulation signals of different frequencies are superimposed;
A part of the first light pulse emitted from the optical waveguide element, reflected by the object, and incident on the optical waveguide element to the light detector and emitted from the optical waveguide element and reflected by the object A portion of the second optical pulse incident on the optical waveguide element, and a signal according to the amount of the portion of the first optical pulse and the portion of the second optical pulse Separate and output the signal according to
26. An optical device according to any of claims 18-25.
In the at least one electrode layer, a boundary between two adjacent ones of the plurality of divided regions has a zigzag shape along the radial direction.
The optical device according to claim 14.
In each of the first electrode layer and the second electrode layer, a boundary between two adjacent divided regions among the plurality of divided regions has a zigzag shape along the radial direction,
When viewed from a direction perpendicular to any one of the first dielectric layer, the second dielectric layer, and the third dielectric layer, the boundary in the first electrode layer and the second dielectric layer The boundaries in the electrode layer form a series of rhombuses,
The optical device according to claim 27.