JP6942333B2 - Light deflection device and rider device - Google Patents

Description

The present invention relates to an optical deflection device that controls the traveling direction of light, and a lidar device including the optical deflection device.

The technical fields of laser radar or lidar equipment (LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging)) that use laser measurement to acquire the distance to surrounding objects as a two-dimensional image are the automatic driving of cars and three-dimensional. It is used for map production, etc., and its basic technology can also be applied to laser printers, laser displays, and the like.

In this technical field, a light beam is applied to an object, the reflected light reflected by the object is detected, distance information is obtained from the time difference and frequency difference, and the light beam is scanned two-dimensionally. Acquires wide-angle 3D information.

A light deflection device is essential for light beam scanning. Conventionally, mechanical mechanisms such as rotation of the entire device, mechanical mirrors such as polygon mirrors (polygon mirrors) and galvano mirrors, and small integrated mirrors using micromachine technology (MEMS technology) have been used, but they are large. In recent years, research on non-mechanical light deflection devices has been active due to problems such as high cost and instability in vibrating moving objects.

As a non-mechanical light deflection device, a phased array type or a diffraction grating type that realizes light deflection by changing the wavelength of light or the refractive index of the device has been proposed. However, the phased array type light deflection device has a problem that it is very difficult to adjust the phase of a large number of light radiators arranged in an array and it is not possible to form a high-quality sharp light beam. On the other hand, the diffraction grating type light deflection device can easily form a sharp beam, but has a problem that the light deflection angle is small.

To solve the problem of a small light deflection angle, the inventor of the present invention has proposed a technique for increasing the light deflection angle by coupling a slow light waveguide to a diffraction mechanism such as a diffraction grating (Patent Document 1). .. Slow light light is generated in photonic nanostructures such as photonic crystal waveguides, has a low group velocity, and is characterized by a large change in propagation constant due to slight changes in wavelength and refractive index of the waveguide. Have. When a diffraction mechanism is installed inside or in the immediate vicinity of this slow light waveguide, the slow light waveguide is combined with the diffraction mechanism to form a leakage waveguide, which radiates light into free space. At this time, a large change in the propagation constant is reflected in the deflection angle of the synchrotron radiation, and as a result, a large deflection angle is realized.

FIG. 6 shows an outline of a device structure in which a diffraction mechanism is introduced into a photonic crystal waveguide that propagates light (slow light) having a low group velocity, and a synchrotron radiation beam. The light deflection device 101 includes a photonic crystal waveguide 102 having a dual periodic structure in which two types of circular holes having different diameters are repeated in the plane of the photonic crystal along the waveguide. The double-period structure constitutes a diffraction mechanism, which converts slow light propagating light into radiation conditions and radiates it into space.

In the light deflection device 101, the photonic crystal waveguide 102 is formed by a lattice array 103 in which circular holes (low refractive index portions) 111 are arranged in a high refractive index member 110 on a clad 113 made of a low refractive index material such as _{SiO 2.} It is formed. The lattice arrangement 103 of the low refractive index portion 111 is, for example, a double periodic structure having a periodic structure in which large-diameter circular holes are repeated and a periodic structure in which small-diameter circular holes are repeated. In the lattice arrangement 103 of the photonic crystal waveguide 102, the portion where the circular hole 111 is not provided constitutes the waveguide core 112 that propagates the incident light.

The synchrotron radiation beam is a high-quality beam formed in the vertical direction and spread in the horizontal direction. Here, the vertical direction is the direction along the waveguide core, and is the traveling direction of the propagating light propagating in the photonic crystal waveguide 102. On the other hand, the lateral direction is a direction orthogonal to the direction along the waveguide core and is a direction orthogonal to the direction in which the propagating light travels.

6 (b) and 6 (c) are diagrams for explaining the beam intensity distribution of the synchrotron radiation beam, FIG. 6 (b) shows the beam intensity distribution in the vertical direction, and FIG. 6 (c) shows the beam intensity distribution in the horizontal direction. The beam intensity angle distribution is shown.

In FIG. 6B, the synchrotron radiation beam gradually leaks along the waveguide core to form a sharp beam with a uniform vertical beam intensity distribution. In FIG. 6C, the lateral beam intensity angle distribution has a wide angle distribution.

In the lateral angular distribution of the synchrotron radiation beam, if there is a lateral spread and a complicated beam intensity distribution shape having a plurality of peaks of the beam intensity, it becomes a factor that lowers the conversion efficiency to the parallel beam.

In order to suppress the lateral spread of the synchrotron radiation beam, as shown in FIG. 6D, a collimated lens such as a cylindrical lens is installed above the light deflection device, and the synchrotron radiation beam from the waveguide core is emitted. A configuration that converts to a parallel beam is used.

FIG. 7 is a diagram for explaining the lateral deflection of the light emitting beam using a cylindrical lens. The lateral deflection of the light emission beam is performed by arranging the cylindrical lens 104 above the light deflection device 101 along the waveguide core 112, as shown in FIG. Here, the light radiation beam is laterally deflected by switching the waveguide core 112 that incidents the incident light on the plurality of waveguide cores 112 included in the light deflection device 101.

In order to deflect the synchrotron radiation beam in the lateral direction, the waveguide core 112 that emits light is switched by switching the light incident on the waveguide core 112 with an optical switch or the like, and the waveguide core 112 and the cylindrical lens 104 are switched. This is done by changing the relative positional relationship with the incident position of.

Further, the vertical deflection of the light radiation beam is performed by changing the wavelength of the incident light or changing the refractive index of the photonic crystal waveguide 102 by heating or the like. As a result, the light deflection device forms a light beam that is collimated in both the vertical and horizontal directions.

The lidar device uses two light deflection devices, one for transmission and one for reception, and emits a light emission beam from the light deflection device for transmission to hit the object to be measured (object), and the object reflects and returns. The reflected light is detected by a light deflecting device for reception. The lidar device generates a frequency chirp light signal, divides it into reference light and signal light, and the signal light is emitted from a light deflecting device for transmission, reciprocates by hitting an object, and is received by a light deflection device for reception. The distance to the object is obtained from the beat signal obtained by mixing this with the reference light.

For example, in a radar device, a technique is known in which the distance to a target and the relative speed are detected by transmitting and receiving radar waves. (Patent Document 2)

Japanese Patent Application No. 2016-10844 International release WO2013 / 088938

The lidar device uses two light deflection devices, one for transmission and one for reception, in order to emit light to the object and detect reflected light from the object. The two light deflection devices, one for transmission and the other for reception, are provided with a collimating lens such as a cylindrical lens in both light deflection devices to suppress the spread of light in the lateral direction and to perform lateral deflection.

There is also a configuration in which one optical deflection device is used for both transmission and reception, but in this configuration, a 2-input 2-output photocoupler (2 input / 2 output photocoupler) is used to guide the received light to the mixer (mixing unit). 2x2 coupler) is required. In such a configuration, a loss of 3 dB is always generated at the time of transmission and at the time of reception, and a total loss of 6 dB is generated in principle. In order to reduce the loss in the configuration of one such optical deflection device, it is desirable that the transmission optical deflection device and the reception optical deflection device are separated.

FIG. 8 shows a configuration in which two optical deflection devices, one for transmission and the other for reception, are arranged in parallel in the horizontal direction orthogonal to the length direction of the waveguide core. 8 (a) to 8 (c) show the arrangement configuration, and show the configuration in which the cylindrical lenses 104A and 104B are arranged in parallel with respect to the parallel arrangement of the transmission optical deflection device 101A and the reception optical deflector 1B. 8 (d) and 8 (e) show the positional relationship between the emitted light and the reflected light between the two light deflection devices.

In a configuration in which two light deflection devices for transmission and reception are arranged in parallel in the horizontal direction, two cylindrical lenses are arranged above each light deflection device in order to make the light beam a parallel beam. Similarly, they are arranged in parallel in the horizontal direction.

In such a configuration in which the cylindrical lenses are arranged in parallel in the horizontal direction, the positional relationship such as distance and parallelism is precisely arranged between the two cylindrical lenses in order to prevent the occurrence of a deviation in the positional relationship between the transmitted light and the received light. There is a need to.

FIG. 8A shows a state in which the cylindrical lenses 104A and 104B are correctly arranged with respect to the transmission light deflection device 101A and the reception light deflection device 101B, and FIGS. 8B and 8C show transmission light. The positions of the cylindrical lenses 104A and 104B are displaced with respect to the deflection device 101A and the reception light deflection device 101B, and FIGS. 8 (d) and 8 (e) show the positions of the scanned images when the positions are displaced. ing.

When the cylindrical lens 104B is displaced in the lateral direction, as shown in FIGS. 8 (b) and 8 (d), the scanning image formed by the receiving light deflection device 101B is displaced in the lateral direction of the cylindrical lens 104B. The position deviates from the scanning area 121 of the target 120. Further, even when the cylindrical lens 104B is displaced in rotation position, as shown in FIGS. The position is deviated from the scanning area 121 of 120.

An object of the present invention is to solve the above-mentioned problems and to eliminate the need for high precision in manufacturing and alignment in a lens that collimates the light included in the light deflection device.

In the light deflection device of the present invention, two light deflectors, a transmission light deflector and a reception light deflector, and a light emission beam emitted from the transmission light deflector are parallel beams, and the reflected light from the object is reflected. The lidar device of the present invention relates to a rider device provided with this light deflection device, with respect to an arrangement configuration with a collimating lens that condenses light on a receiving light deflector.

[Light deflection device]
The optical deflection device of the present invention includes two optical deflectors arranged in tandem along the length direction in the waveguide core of the waveguide, and one collimating lens. In the present invention, the two elements constituting the optical deflection device are represented by an optical deflector. One collimating lens is linearly arranged along the direction of the parallel arrangement of the two light deflectors on the side where the light is emitted and incident with respect to the two light deflectors arranged in parallel. Here, the vertical direction is the length direction of the waveguide core of the photonic crystal waveguide, and the parallel arrangement is an arrangement along the vertical direction.

In the optical deflection device of the present invention, the relative positions of the two optical deflectors constituting the optical deflection device can be defined by a mask pattern when the device of the deflection element is manufactured by a chip, so that the optical deflector is set in a predetermined direction. It is easy to arrange them together, and it is possible to construct an optical deflector arranged in tandem with high accuracy along the length direction of the waveguide core of the photonic crystal waveguide constituting the optical deflection device.

In the optical deflection device of the present invention, since the collimating lens arranged to face the two vertically arranged optical deflectors is one continuous optical element, the optical characteristics of the lenses for the two optical deflectors are the same. In addition, since the lens alignment can be performed in one step, the alignment work is easy.

Further, when the vertical angle of the deflection of the light beam by the optical deflector of the optical deflection device is changed by heating the waveguide portion to change the refractive index, the two optical deflectors are arranged in a straight line. Due to the arranged configuration, the heating states of the two light deflectors can be easily homogenized.

As described above, the light deflecting device of the present invention is configured by two light deflectors arranged in a linear column and one collimating lens in the direction of the light beam of the light deflector for transmission and reception. Matching is easy and the efficiency of the optical radar of the lidar device of the present invention is improved.

The two optical deflectors included in the optical deflection device of the present invention are on a photonic crystal waveguide having a lattice arrangement in which low refractive index portions are periodically arranged in the plane of a high refractive index member, and on a photonic crystal. It is equipped with a provided diffraction mechanism. The incident light incident on the transmission optical deflector is propagated by the waveguide core of the photonic crystal waveguide and radiated to the outside by a diffraction mechanism provided on the photonic crystal. The emitted light emission beam is reflected by the object, and the reflected light is collected by the diffraction mechanism of the receiving light deflector and detected through the waveguide core of the photonic crystal waveguide.

The photonic crystal waveguide provided in the optical deflector of the present invention is configured by a periodic structure that expresses slow light. In the periodic structure of the slow light photonic crystal, low refractive index portions are arranged on a high refractive index member with a period a (≈λ / 2n). Note that n is the equivalent refractive index of light propagating in the waveguide of the high refractive index member, and λ is a wavelength near the Bragg wavelength.

Due to this periodic structure, in the photonic crystal waveguide, a photonic band gap (stop band) is generated near the Bragg wavelength satisfying a = λ / 2n, the group refractive index _ng in the waveguide increases, and the group velocity Causes a small slow light. Slow light propagates while having a widening (exuding component) of the intensity distribution of the electromagnetic field around it.

In slow light, the propagation constant β changes significantly due to a slight change in the wavelength λ of light or the refractive index n of the waveguide. When the propagation constant β of the periodic structure of the waveguide changes, the coupling condition with the periodic structure of the diffraction mechanism changes, and the angle θ of the synchrotron radiation beam changes. Therefore, the angle θ of the synchrotron radiation beam can be changed by changing the wavelength λ of light and the refractive index n of the waveguide to change the propagation constant β.

The light deflection device of the present invention uses a surface diffraction grating or a slow light photonic crystal waveguide having a lattice arrangement in which low refractive index portions are arranged in a double period in the plane of a high refractive index member as a diffraction mechanism. It can be configured.

The diffraction mechanism by the surface diffraction grating is configured by arranging the surface diffraction gratings adjacent to each other on the photonic crystal waveguide. On the other hand, the diffraction mechanism by the slow light photonic crystal waveguide is configured by stacking the slow light photonic crystal waveguide in the lattice array constituting the photonic crystal waveguide. The slow light photonic crystal constituting this diffraction mechanism and the slow light photonic crystal constituting the waveguide differ in the period of the low refractive index portion with respect to the high refractive index member. For example, the circuit mechanism has a lower refractive index than the waveguide. Let the cycle of the index part be a long cycle.

In the diffraction mechanism using the slow light photonic crystal waveguide, the periodic structure combines with the slow light exudation component of the waveguide to scatter and diffract it, and gradually radiates upward or diagonally with respect to the traveling direction of the waveguide. do. The light emission beam is emitted from a wide range along the traveling direction of the waveguide, and the radiation is in phase with each other, so that the light emission beam is a high-quality sharp light beam.

Therefore, one form of the optical deflection device of the present invention is a double-period structure having a photonic crystal waveguide constituting a slow light waveguide and a photonic crystal periodic structure having two types of periods, short period and long period. The short-period periodic structure constitutes a slow light waveguide with a large step, and the long-period periodic structure constitutes a diffraction mechanism with a small step.

The photonic crystal waveguide of the transmission optical deflector and the reception optical deflector included in the optical deflection device of the present invention includes a plurality of waveguide cores. The plurality of waveguide cores are arranged in parallel in the horizontal direction orthogonal to the length direction of the waveguide core. Each waveguide core arranged in parallel in the horizontal direction has a different positional relationship with the collimating lens. Due to the optical characteristics of the collimated lens, the light incident near the center of the collimated lens travels almost straight, and the light incident on the edge side of the collimated lens is refracted toward the center side of the collimated lens to form a parallel beam. .. Further, there is a correspondence relationship between the waveguide core into which the incident light is incident and the light beam emitted. Therefore, by switching the waveguide core on which the incident light is incident, the irradiation position of the light radiation beam on the object can be changed, and the light can be scanned laterally on the object.

As the collimating lens provided in the light deflection device of the present invention, it is possible to use a single lens of a cylindrical lens having a width similar to the width of the optical deflector and the same length as the vertically arranged length of the two optical deflectors. can. Further, the collimating lens included in the light deflection device of the present invention is not limited to a single lens, and may be composed of a group lens composed of a plurality of lenses. The collimating lens by the group lens can be, for example, a set of group lenses in which a plurality of rod lenses are arranged in parallel, or a set of group lenses in which a plurality of lenses are stacked and arranged. The plurality of rod lenses are, for example, narrower than the width of the light deflector and have a length comparable to the length of the two light deflectors arranged in a column.

[Rider device]
The lidar device of the present invention includes the light deflection device of the present invention, a mixer that outputs a beat signal, and a calculation unit that obtains the distance between the light deflection device and an object based on the frequency spectrum of the beat signal.

Of the two optical deflectors included in the optical deflector, one optical deflector is used as a transmitting optical deflector and the other optical deflector is used as a receiving optical deflector. The mixer was emitted from the reference light of the frequency chap optical signal branched immediately before entering the transmitting optical deflector and the transmitting optical deflector, reciprocated through the object, and received by the receiving optical deflector. The beat signal is output together with the signal light. The mixer can use, for example, a balanced photodiode, which detects a beat signal with a frequency difference corresponding to the delay time between the signal light and the reference light. The arithmetic unit obtains the distance to the object based on the frequency spectrum of the beat signal.

When the speed of light is c and one modulation period of the chirp optical signal is T, the arithmetic unit performs (c × fb × T) / (2) based on the beat frequency fb of the frequency spectrum and the frequency displacement width B of the chirp optical signal. The distance is calculated by the formula of × B).

As described above, the light deflection device and the lidar device of the present invention do not require high precision in manufacturing and alignment in the lens that collimates the light included in the light deflection device.

It is a figure for demonstrating the schematic configuration example of the light deflection device of this invention. It is a figure for demonstrating the operation example of the light deflection device of this invention. It is a figure for demonstrating the operation example of the light deflection device of this invention. It is a figure for demonstrating the operation example of the light deflection device of this invention. It is a figure for demonstrating the schematic structure of the rider device of this invention. It is a figure for demonstrating the outline of the device structure which introduced the diffraction mechanism into the photonic crystal waveguide which propagates the light (slow light) having a low group velocity, and the synchrotron radiation beam. It is a figure for demonstrating the lateral deflection of a light emission beam using a cylindrical lens. It is a figure for demonstrating the configuration in which two optical deflection devices for transmission and reception are arranged in parallel in the lateral direction orthogonal to the length direction of a waveguide core.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a schematic configuration example of the light deflection device of the present invention will be described with reference to FIG. 1, the operation of the light deflection device of the present invention will be described with reference to FIGS. 2 to 4, and the lidar device of the present invention will be described with reference to FIG. The outline configuration of the above will be described.

(Overview of optical deflection device)
FIG. 1 is a diagram for explaining the light deflection device of the present invention. The optical deflection device 1 includes two optical deflectors, a transmission optical deflector 1A and a reception optical deflector 1B. The transmitting optical deflector 1A and the receiving optical deflector 1B are composed of a photonic crystal waveguide 2. The photonic crystal waveguide 2 is formed by a lattice array 3 in which low refractive index portions are periodically arranged on a high refractive index member 10 made of a semiconductor such as Si. The low refractive index portion can be, for example, a circular hole 11 provided in the high refractive index member 10. Further, the photonic crystal waveguide 2 is provided on the clad 13 made of a semiconductor material such as Si.

In the photonic crystal waveguide 2, the portion of the lattice arrangement 3 in which the circular hole 11 of the low refractive index portion is not provided constitutes the waveguide core 12 for propagating light. The waveguide core 12 is formed by a portion of the lattice arrangement 3 composed of the arrangement of the circular holes 11 in which the circular holes 11 are not arranged in a part of the lattice arrangement 3. The incident light incident on the waveguide core 12 is radiated to the outside from the waveguide core 12 while propagating in the length direction of the waveguide core 12.

The optical deflection device 1 includes two optical deflectors, a transmission optical deflector 1A and a reception optical deflector 1B. In the transmitting optical deflector 1A and the receiving optical deflector 1B, the photonic crystal waveguide 2 is formed by the lattice arrangement 3 in which the circular holes 11 of the low refractive index portion are periodically arranged in the high refractive index member 10. The photonic crystal waveguide 2 has a double-period structure in which the circular holes 11 are arranged in two types of periods, long and short, to radiate light diffraction between the waveguide that propagates light and the waveguide and the outside. Consists of a diffractive structure.

The transmission optical deflector 1A has a plurality of waveguide cores 12Aa to 12Ac arranged in parallel on the photonic crystal waveguide 2, and the reception optical deflector 1B has a plurality of waveguide cores on the photonic crystal waveguide 2. 12Ba to 12Bc are arranged in parallel. The number of waveguide cores arranged in parallel can be any number.

The transmitting optical deflector 1A and the receiving optical deflector 1B are arranged in parallel in a straight line along the length direction of the waveguide core 12. In the parallel arrangement, the transmission light deflector 1A is arranged on the side where the incident light is incident, and the reception light deflector 1B is arranged on the side where the emitted light is emitted.

In addition to the transmission light deflector 1A and the reception light deflector 1B described above, the light deflection device 1 includes one cylindrical lens 4 as a collimating lens that converts light into parallel light. The cylindrical lens 4 is provided along the direction of the columnar arrangement of the light deflectors on the side of the surface that emits the light emission beam and the surface that receives the reflected light with respect to the two light deflectors (1A, 1B) arranged in a column. It is placed on top of each other.

The size of the cylindrical lens 4 is, for example, the same as the width of the optical deflectors (1A, 1B) and the length of the two vertically arranged optical deflectors (1A, 1B). be able to. The size of the cylindrical lens 4 is such that the light radiation beam emitted from the transmission light deflector 1A is converted into a parallel beam and irradiated to an object (not shown), and the reflected light reflected by the object is emitted. The size is not limited to the same size as the above-mentioned columnar arrangement, and may be any size as long as the size is sufficient for condensing the light on the receiving light deflector 1B.

The collimating lens included in the light deflection device of the present invention can be in a plurality of lens forms. A mode in which a single-lens cylindrical lens 4 is used as the collimating lens shown in FIG. 1A is shown. As the cylindrical lens 4, a single lens having a width similar to the lateral width of the optical deflectors 1A and 1B and a length similar to the length in which the two optical deflectors 1A and 1B are arranged in a column can be used.

The collimating lens included in the light deflection device of the present invention is not limited to a single lens, and may be composed of a group lens composed of a plurality of lenses as shown in FIG. 1 (b). The collimating lens by the group lens is, for example, a set of group lenses 4a in which a plurality of rod lenses 4a1, 4a2 to 4an are arranged in parallel, or a set of a set of lenses 4b1 and 4b2 in which a plurality of lenses 4b1 and 4b2 are laminated. It can be a set lens 4b. The plurality of rod lenses 4a1, 4a2 to 4an are, for example, narrower than the width of the light deflector and have a length similar to the length of the two light deflectors arranged in a column.

Next, an operation example of the light deflection device of the present invention will be described with reference to FIGS. 2 to 4. The incident light and the synchrotron radiation beam shown in FIGS. 2 to 4 are schematically shown. In reality, the object 20 is sufficiently far away that the synchrotron radiation and the reflected light are substantially parallel to each other and can be regarded as having substantially the same angle as compared with the distance between the two light deflectors 1A and 1B. In FIGS. 2 to 4, the distance between the object 20 and the light deflection device 1 is shown in a state where the object 20 and the light deflection device 1 are arranged much closer than they actually are, for the sake of explanation.

In FIGS. 2 to 4, the object 20 is arranged above the cylindrical lens 4 of the light deflection device 1 with the measurement surface of the object 20 facing the light deflection device 1. In this arrangement, the light emission beam A emitted from the transmission light deflector 1A is converted into a parallel beam by the cylindrical lens 4, and then propagates in a beam shape to irradiate the measurement surface of the object 20. The object 20 scatters in all directions, and a part of the scattered light is received as a reflected beam by the receiving light deflector 1B. The reflected beam B is focused on the receiving light deflector 1B by the cylindrical lens 4, and is detected via the waveguide core of the receiving light deflector 1B.

In irradiating the object 20 with the light radiation beam A, the scanning region 21 is scanned by changing the irradiation position on the object 20. The scanning region 21 is scanned in the vertical direction along the length direction of the waveguide core 12 and in the horizontal direction orthogonal to the length direction of the waveguide core 12, as well as in the vertical and horizontal directions. And may be combined to perform scanning in any direction.

2 and 3 show an example of vertical scanning. FIG. 2A shows a state in which incident light is incident on the waveguide core 12Aa on one side of the transmission optical deflector 1A and the scanning region 21a of the object 20 is scanned in the vertical direction. .. The longitudinal scan is performed as the slow light propagates through the waveguide core 12Aa, as shown in FIG. 2 (b).

FIG. 3A shows a state in which incident light is incident on the waveguide core 12Ac on the other side of the transmission optical deflector 1A and the scanning region 21c of the object 20 is scanned in the vertical direction. .. The longitudinal scan is performed as the slow light propagates through the waveguide core 12Ac, as shown in FIG. 3 (b). When the central portion of the object 20 is used as the scanning region, the incident light can be incident on the central waveguide core of the transmission optical deflector 1A and scanned in the vertical direction. The scan of this central portion is not shown. Further, the radiation angle of the light radiation beam at this time can be changed by the wavelength of the incident light and the refractive index of the photonic crystal waveguide.

Although 3 examples of the waveguide cores are shown in FIGS. 2 to 4, the number of waveguide cores is not limited to this number and can be any number.

FIG. 4 shows an example of lateral scanning. FIG. 4A shows the transmission optical deflector 1A by sequentially switching the incident light and incident light on the waveguide core 12Aa, the waveguide core 12Ab, and the waveguide core 12Ac of the transmission optical deflector 1A. The light emitting beam emitted from the object 20 is moved in the lateral direction orthogonal to the length direction of the waveguide core, thereby indicating a state in which the scanning region 21d of the object 20 is scanned in the lateral direction. The horizontal scan is performed in the vertical direction as the slow light propagates through the waveguide core 12Aa, as shown in FIG. 4 (b).

In FIG. 4, the lateral scanning of the scanning region 21d is described so that the light emission beam is emitted from each of the waveguide cores 12Aa to 12Ac at the same time, but the light emission from each of the waveguide cores 12Aa to 12Ac is described. Since the beam is emitted by switching the incident light, it is actually performed with a time lag.

Further, in the case where the incident light is incident on each of the waveguide cores 12Aa to 12Ac of the plurality of waveguide cores at the same time, the beat frequency of the detection light and the reference light in the lidar device is extracted. In addition, accurate distance measurement may not be possible due to interference between incident light and detection light incident on each waveguide core. is necessary.

In the above, the optical deflection device is described by using a configuration example using a photonic crystal waveguide slow light as a diffraction mechanism, but it is composed of two optical deflectors arranged in a linear column and one collimating lens. In the light deflection device to be used, a surface diffraction grating may be used instead of the photonic crystal waveguide slow light.

(Overview of rider device)
Next, a schematic configuration of the rider device of the present invention will be described with reference to FIG.
The lidar device 5 uses the light deflection device 1 of the present invention to scan the object 20 by irradiating the object 20 with light and detecting the reflected light reflected and returned by the object 20 to scan the object 20. Find the distance to the object 20. It is also possible to obtain the relative speed between the rider device 5 and the object 20.

As described above, the light deflection device 1 included in the lidar device 5 includes a transmission light deflector 1A and a reception light deflector 1B arranged in a straight line, and a collimating lens (cylindrical lens 4) arranged above the transmission light deflector 1A and a reception light deflector 1B. ) Is provided.

Of the two light deflectors included in the light deflection device 1, the signal light is incident on the transmission light deflector 1A. The signal light incident on the transmission optical deflector 1A propagates through the waveguide core of the photonic crystal waveguide by slow light. The slow light leaks to the outside while propagating through the waveguide core and emits a light emission beam A toward the object 20. The light emission beam A is reflected by the object 20. The receiving light deflector 1B receives the reflected light B and emits the detected light from the end of the waveguide core.

The deflection angles of the transmitting light deflector 1A and the receiving light deflector 1B can be changed by the wavelength of the incident light or the refractive index of the photonic crystal waveguide. The refractive index variable device 56 that changes the refractive index of the photonic crystal waveguide is, for example, a device that changes the temperature of the photonic crystal waveguide that constitutes the transmitting optical deflector 1A and the receiving optical deflector 1B. Can be configured.

As the signal light incident on the transmission optical deflector 1A, one of the light obtained by separating the frequency chirp optical signal whose frequency changes sequentially by the separator 52 is used. This light may be amplified by the semiconductor amplifier (SOA) 53 and used. The other light separated by the separator 52 is introduced into the mixer 54 as reference light.

The frequency modulator (Modulator) linearly modulates the frequency of the laser light generated by the laser light source 50 with a fixed period T to generate a frequency chirp light signal. Since the signal light and the reference light are light obtained by separating the frequency chirp light signal, they have the same frequency and phase.

The detection light obtained from the reception light deflector 1B of the light deflection device 1 is introduced into the mixer 54 together with the reference light, and a beat signal in which the reference light and the detection light are mixed is generated.

The round trip between the light deflection device 1 and the object 20 causes a delay in the signal light, during which the reference light gradually changes in frequency depending on the frequency chirp. The mixer 54 mixes and detects the signal light and the reference light that are received after reciprocating. As a result, a beat signal corresponding to the frequency difference between the signal light and the detection light is detected. The mixer 54 uses, for example, a balanced photodiode 54a to detect a beat signal with a frequency difference corresponding to the delay time between the detection light and the reference light.

The calculation unit 55 obtains the distance from the object 20 based on the frequency spectrum of the beat signal obtained by the mixer 54. The arithmetic unit 55 can be configured by, for example, an A / D converter that A / D-converts the output signal of the balanced photodiode 54a, and a processor that arithmetically processes the obtained digital signal.

Assuming that the beat frequency of the beat signal is fb, the frequency displacement width of the signal light is B, the speed of light is c, and one modulation cycle required for modulation of one cycle of the chirp light signal is T, the distance R from the target is the following equation (1). ).
R = (c × fb × T) / (2 × B)… (1)

When the relative speed with respect to the object is obtained by the lidar device of the present invention, it is obtained by using the beat frequency fu obtained by using the up-chirp optical signal whose frequency increases and the down-chirp optical signal obtained by using the down-chirp optical signal whose frequency decreases. The relative velocity v is expressed by the following equation (2) using the beat frequency fd to be obtained. Note that fo is the center frequency of the chirp optical signal.
v = (c / 4fo) × (fu−fd)… (2)

The present invention is not limited to each of the above embodiments. Various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

The optical deflection device of the present invention can be mounted on automobiles, drones, robots, etc., and can be mounted on a personal computer or smartphone to easily capture the surrounding environment. 3D scanner, surveillance system, spatial matrix light for optical exchange and data center. It can be applied to switches and the like.

In the above-described embodiment, Si is assumed as the high refractive index member constituting the photonic crystal waveguide of the light deflection device, and light in the wavelength range of near infrared light is used. By applying it to visible light materials as a refractive index member, it is expected to be further applied to projectors, laser displays, retinal displays, 2D / 3D printers, POS, card readers, and the like.

1 Optical deflection device 1A Optical deflector for transmission 1B Optical deflector for reception 2 Photonic crystal waveguide 3 Lattice arrangement 4 Cylindrical lens 5 Rider device 10 High refractive index member 11 Circular hole 12 waveguide core 12Aa-12Ac waveguide core 12Ba -12Bc waveguide core 13 clad 20 object 21, 21a, 21c, 21d scanning area 50 laser light source 52 separator 54 mixer 54a balanced photonic crystal 55 arithmetic unit 56 refractive index variable 101 optical deflection device 101A optical deflection for transmission Device 101B Optical deflection device for reception 102 Photonic crystal waveguide 103 Lattice arrangement 104, 104A, 104B Cylindrical lens 110 High refractive index member 111 Circular hole (low refractive index part)
112 Waveguide core 113 Clad 120 Target 121 Scanning area A Light emission beam B Reflection beam

Claims (7)

Waveguides of the waveguide core is formed in a linear shape, the main surface light is the side that is emitted and incident, a two optical deflector having a length the waveguide of the waveguide core of each other two optical deflector is sequence in tandem so as to be continuous in a straight line along the direction,
Each pre-SL two light deflectors, the main surface of the waveguide core is formed of the waveguide so as to face the, and, arranged along the column direction of arrangement of the two light deflectors A light deflection device , comprising one collimating lens. Each of the light deflectors is
A photonic crystal waveguide having a lattice arrangement in which low refractive index portions are periodically arranged in the plane of a high refractive index member.
as well as,
The light deflection device according to claim 1, further comprising a diffraction mechanism provided on the photonic crystal. The diffraction mechanism is
Surface diffraction grating,
Or
The light deflection device according to claim 2 , which is a slow light photonic crystal waveguide having a lattice array in which low refractive index portions are arranged in a plane of a high refractive index member in a double cycle. The optical deflection device according to claim 2 or 3 , wherein the photonic crystal waveguide of each optical deflector includes a plurality of waveguide cores. The collimating lens is any one of a single lens of a cylindrical lens, a set of a set of lenses in which a plurality of rod lenses are arranged in parallel, and a set of a set of lenses in which a plurality of lenses are arranged in a laminated manner. The light deflection device according to any one of 1 to 4. One of the optical deflectors of any one of the optical deflecting devices of claims 1 to 5 is used as a transmitting optical deflector, and the other optical deflector is used as a receiving optical deflector.
A chirped light signal incident to the transmission optical deflector, a mixer for outputting the input beat signal and detecting light from said receiving credit optical deflector,
A rider device including a calculation unit for obtaining a distance between the light deflection device and an object based on the frequency spectrum of the beat signal. Based on the beat frequency fb of the frequency spectrum and the frequency displacement width B of the chirp optical signal, the arithmetic unit sets the speed of light to c and one modulation period of the chirp optical signal to T.
(C × fb × T) / (2 × B)
The rider device according to claim 6, wherein the distance is calculated by the calculation formula of.

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