WO2021192601A1

WO2021192601A1 - Line beam scanning optical system, and laser radar

Info

Publication number: WO2021192601A1
Application number: PCT/JP2021/003109
Authority: WO
Inventors: 公博村上
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2020-03-26
Filing date: 2021-01-28
Publication date: 2021-09-30

Abstract

This laser radar is provided with a line beam scanning optical system (10), and a light receiving optical system. The line beam scanning optical system (10) is provided with: a plurality of laser light sources (11a) arranged side-by-side in a direction corresponding to the long side of a line beam (B10); an optical deflector (14) including a mirror (14a) which deflects the line beam (B10) in the short-side direction; a lens portion (40) which collimates laser beams emitted from each of the plurality of laser light sources (11a), and condenses each collimated laser beam onto the mirror (14a); and a diffusing optical element (15) which causes each of the plurality of laser beams reflected by the mirror (14a) to diffuse in the long-side direction. Each of the plurality of laser beams is incident on the diffusing optical element (15) while remaining in the state of having been collimated by the lens portion (40).

Description

Line beam scanning optics and laser radar

The present invention relates to a line beam scanning optical system that generates a long line beam in one direction and scans the line beam in the short side direction thereof, and a laser radar that detects an object using the line beam scanning optical system.

Conventionally, laser radars that detect objects using laser light have been developed in various fields. For example, in an in-vehicle laser radar, laser light is projected from the front of the vehicle, and it is determined whether or not an object such as a vehicle exists in front of the vehicle based on the presence or absence of the reflected light. Further, the distance to the object is measured based on the projection timing of the laser beam and the reception timing of the reflected light.

The following Patent Documents 1 and 2 disclose a device that scans a linear beam to detect an obstacle in front of a vehicle.

Japanese Unexamined Patent Publication No. 5-205199 JP-A-2017-150990

In the laser radar with the above configuration, it is necessary to increase the amount of light of the line beam in order to detect an object at a longer distance and a wider angle. As a method for that, a method of arranging a plurality of laser light sources side by side can be used.

On the other hand, when the laser radar is used outdoors, it is possible that the line beam will enter the human eye. Therefore, the line beam is required to have a safe amount of light so as not to affect the eyes even if it is incident on the human eye.

In view of such a problem, an object of the present invention is to provide a line beam scanning optical system and a laser radar capable of effectively increasing the amount of light of a line beam while suppressing the influence on the human eye.

The first aspect of the present invention relates to a line beam scanning optical system that generates a long line beam in one direction and scans the line beam in the short side direction thereof. The line beam scanning optical system according to this aspect includes a plurality of laser light sources arranged side by side in a direction corresponding to the long side of the line beam, and an optical deflector having a mirror for deflecting the line beam in the short side direction. The laser light emitted from the plurality of laser light sources is converted into parallel light, and the parallelized laser light is focused on the mirror, respectively, and the plurality of lasers reflected by the mirror. A diffusion optical element that diffuses light in the long side direction is provided. Each of the plurality of laser beams is incident on the diffusion optical element in a state of being collimated by the lens portion.

According to the line beam scanning optical system according to this aspect, the laser beam is diffused by the diffusing optical element to generate a line beam, so that the light emitting region of the line beam on the diffusing surface of the diffusing optical element is the target of eye-safe determination. It becomes an effective light source. On the other hand, when the diffusing optical element is not used, a minute region where the laser beams overlap on the mirror of the optical deflector becomes an appropriate light source for eye safe determination. Therefore, in this embodiment, the light emitting area of the pearl light source can be remarkably expanded and the influence of the line beam on the human eye can be remarkably suppressed as compared with the case where the diffusion optical element is not used. Therefore, it is possible to suppress the influence of the line beam on the human eye while effectively increasing the amount of light of the line beam by arranging a plurality of laser light sources.

In addition, in the line beam scanning optical system according to this embodiment, since a plurality of laser beams are incident on the diffused optical element in a state of being collimated, the light rays of each laser beam are directed to the diffused optical element. It is incident at almost the same angle of incidence. Therefore, each laser beam can be appropriately beam-shaped into a predetermined diffusion state by the diffusion optical element.

The second aspect of the present invention relates to a laser radar. The laser radar according to this aspect includes a line beam scanning optical system according to the first aspect and a light receiving optical system that receives reflected light from an object of laser light projected from the line beam scanning optical system. ..

According to the laser radar according to the present aspect, since the line beam scanning optical system according to the first aspect is provided, a plurality of laser light sources are arranged to effectively increase the amount of light of the line beam, and the line beam with respect to the human eye. The influence of can be suppressed. Therefore, it is possible to improve the safety of the laser radar while expanding the distance range in which the object can be detected.

As described above, according to the present invention, it is possible to provide a line beam scanning optical system and a laser radar capable of effectively increasing the amount of light of a line beam while suppressing the influence on the human eye.

The effect or significance of the present invention will be further clarified by the description of the embodiments shown below. However, the embodiments shown below are merely examples when the present invention is put into practice, and the present invention is not limited to those described in the following embodiments.

FIG. 1 is a diagram showing a configuration of an optical system and a circuit unit of a laser radar according to an embodiment. FIG. 2 is a perspective view showing the configuration of the line beam scanning optical system according to the embodiment. 3A and 3B are perspective views showing the configuration of the laser light source according to the embodiment, respectively, and FIG. 3C is a perspective view showing the configuration of the light source array of the laser radar according to the embodiment. Is. 4 (a) and 4 (b) are a top view and a front view schematically showing the configuration of the diffusion optical element according to the embodiment, respectively. FIG. 4C is a diagram showing the optical action of the diffusion optical element according to the embodiment. FIG. 5 is a diagram schematically showing a state in which a laser beam of a laser radar is emitted and a state of a line beam in a target region according to an embodiment. FIG. 6A is a diagram schematically showing the arrangement of each member in the line beam scanning optical system according to the embodiment. FIG. 6B is a diagram showing an acceptance angle of an apparent light source of the human eye (naked eye) based on the "Safety Standards for Laser Products" (JISC 6802: 2014) according to the embodiment. FIG. 7A is a perspective view showing the configuration of the line beam scanning optical system according to the first modification. FIG. 7B is a diagram schematically showing the arrangement of each member in the line beam scanning optical system according to the first modification. 8 (a) and 8 (b) are side views and perspective views showing the configuration of the line beam scanning optical system according to the second modification, respectively. 9 (a) and 9 (b) are perspective views showing the configuration of the laser light source according to the modified example 3, respectively, and FIG. 9 (c) is a perspective view showing the configuration of the light source array of the laser radar according to the modified example 3. Is. FIG. 10A is a diagram schematically showing the traveling direction of the laser light emitted from each of the three laser light sources arranged vertically according to the third modification. FIG. 10B is a diagram schematically showing the spread of the laser light emitted from the laser light source in the fast axis direction according to the embodiment. FIG. 11A is a perspective view showing the configuration of the optical deflector according to the embodiment. FIG. 11B is a diagram schematically showing the relationship between the beam incident on the mirror and the mirror according to the embodiment. FIG. 12A is a perspective view showing the configuration of the optical deflector according to the fourth modification. FIG. 12B is a diagram schematically showing the relationship between the beam incident on the mirror and the mirror according to the fourth modification.

However, the drawings are for illustration purposes only and do not limit the scope of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, the X, Y, and Z axes that are orthogonal to each other are added to each figure. The X-axis direction and the Y-axis direction are the long side direction and the short side direction of the line beam, respectively, and the Z-axis positive direction is the projection direction of the line beam.

FIG. 1 is a diagram showing a configuration of an optical system and a circuit unit of the laser radar 1. FIG. 2 is a perspective view showing the configuration of the line beam scanning optical system 10.

As shown in FIG. 1, the laser radar 1 includes a line beam scanning optical system 10 and a light receiving optical system 20 as an optical system configuration. The line beam scanning optical system 10 generates a long line beam B10 in one direction (X-axis direction) and scans the line beam B10 in the short side direction (Y-axis direction) thereof. The light receiving optical system 20 receives the reflected light from the object of the laser light projected from the line beam scanning optical system 10.

The line beam scanning optical system 10 includes a light source array 11, a fast-axis cylindrical lens 12, a slow-axis cylindrical lens 13, an optical deflector 14, and a diffusion optical element 15. Further, the light receiving optical system 20 includes a light receiving lens 21 and a light receiving element 22.

The light source array 11 is configured by integrating a plurality of laser light sources 11a. The laser light source 11a emits a laser beam having a predetermined wavelength. The laser light source 11a is an end face emitting type laser diode. The laser light source 11a may be a surface emitting type laser light source. In this embodiment, it is assumed that the laser radar 1 is mounted on the vehicle. Therefore, the emission wavelength of each laser light source 11a is set in the infrared wavelength band (for example, 905 nm). The emission wavelength of the laser light source 11a can be appropriately changed depending on the usage mode of the laser radar 1.

3 (a) and 3 (b) are perspective views showing the configuration of the laser light source 11a, respectively, and FIG. 3 (c) is a perspective view showing the configuration of the light source array 11.

As shown in FIG. 3A, the laser light source 11a has a structure in which the active layer 111 is sandwiched between the N-type clad layer 112 and the P-type clad layer 113. The N-type clad layer 112 is laminated on the N-type substrate 114. Further, the contact layer 115 is laminated on the P-type clad layer 113. When a current is applied to the electrode 116, the laser beam is emitted from the light emitting region 117 in the positive direction of the Y-axis. Generally, in the light emitting region 117, the width W1 in the direction parallel to the active layer 111 is wider than the width W2 in the direction perpendicular to the active layer 111.

The axis in the short side direction of the light emitting region 117, that is, the axis in the direction perpendicular to the active layer 111 (Z axis direction) is called the fast axis, and the axis in the long side direction of the light emitting region 117, that is, the active layer 111. An axis in the parallel direction (X-axis direction) is called a slow axis. In FIG. 3B, 118a indicates a fast axis and 118b indicates a slow axis. The laser beam emitted from the light emitting region 117 has a larger spread angle in the fast axis direction than in the slow axis direction. Therefore, as shown in FIG. 3B, the shape of the beam B20 is an elliptical shape that is long in the fast axis direction.

As shown in FIG. 3C, a plurality of laser light sources 11a are installed on the base 120 so as to be arranged along the slow axis, and the light source array 11 is configured. Therefore, the light emitting regions 117 of each laser light source 11a are arranged in a row in the slow axis direction. Here, each laser light source 11a is arranged so that the fast axis 118a of the light emitting region 117 is parallel to the direction corresponding to the short side direction of the line beam B10 shown in FIG. Although there are individual differences, the plurality of laser light sources 11a constituting the light source array 11 all have emission characteristics that are distributed within a certain range indicated in the specifications.

In FIG. 3C, the light source array 11 is configured by installing the plurality of laser light sources 11a adjacent to each other on the base 120, but the plurality of light emitting regions 117 are arranged in the slow axis direction. One formed semiconductor light source may be installed on the base 120. In this case, in the semiconductor light emitting device, the structural portion that emits the laser light from each light emitting region 117 corresponds to the laser light source 11a, respectively.

With reference to FIGS. 1 and 2, the fast-axis cylindrical lens 12 converges the laser light emitted from each laser light source 11a of the light source array 11 in the fast-axis direction, and substantially spreads the laser light in the fast-axis direction. Adjust to a parallel state. That is, the fast-axis cylindrical lens 12 has an action of parallelizing the laser light emitted from each laser light source 11a of the light source array 11 only in the fast-axis direction.

The slow-axis cylindrical lens 13 parallelizes the laser light emitted from the plurality of laser light sources 11a of the light source array 11 in the slow-axis direction, and collects the plurality of parallel-lighted laser light in the slow-axis direction. Let me. Each laser beam transmitted through the slow-axis cylindrical lens 13 heads toward the mirror 14a in a state of being parallelized. At this time, the laser beams approach each other as they approach the mirror 14a, and are incident on the mirror 14a at substantially the same position.

The fast-axis cylindrical lens 12 has a lens surface 12a that is curved only in a direction parallel to the YY plane. The generatrix of the lens surface 12a is parallel to the X axis. Fast Axis The fast axis of each laser beam incident on the cylindrical lens 12 is perpendicular to the generatrix of the lens surface 12a. The laser beams are aligned in the X-axis direction and incident on the fast-axis cylindrical lens 12. Each laser beam receives a convergence action in the fast axis direction (Z axis direction) on the lens surface 12a and becomes parallel light in the fast axis direction.

The slow axis cylindrical lens 13 has a lens surface 13a that curves only in a direction parallel to the XY plane. The generatrix of the lens surface 13a is parallel to the Z axis. The bus lines of the lens surfaces 12a and 13a are perpendicular to each other.

In the present embodiment, the fast-axis cylindrical lens 12 and the slow-axis cylindrical lens 13 parallelize the laser beams emitted from the plurality of laser light sources 11a, and collect the parallelized laser beams on the mirror 14a, respectively. A shining lens unit 40 is configured. However, the configuration of the lens unit 40 is not limited to this, and for example, parallel lightening in the slow axis direction and focusing on the mirror 14a may be realized by different lenses.

The optical deflector 14 is, for example, a MEMS (Micro Electro Mechanical Systems) mirror using a piezoelectric actuator, an electrostatic actuator, or the like. The reflectance of the mirror 14a is increased by a dielectric multilayer film, a metal film, or the like. The mirror 14a is arranged at a position near the focal length on the positive side of the Y-axis of the slow-axis cylindrical lens 13. The mirror 14a is driven so as to rotate about a rotation axis R1 parallel to the X axis. The mirror 14a has, for example, a circular shape having a diameter of about 3 mm.

The diffusion optical element 15 diffuses the laser light from each laser light source 11a incident from the mirror 14a side in the X-axis direction. The diffusion optical element 15 has a plate-like shape curved in an arc shape in a direction parallel to the rotation axis R1 of the mirror 14a with the mirror 14a substantially in the center as the center. That is, the diffusion optical element 15 has a shape in which a flat plate whose incident surface and exit surface are parallel to each other is curved in an arc shape. In the diffusing optical element 15, either the incident surface or the exit surface is a diffusing surface that diffuses the laser beam. Here, the exit surface is the diffusion surface 15a.

4 (a) and 4 (b) are a top view and a front view schematically showing the configuration of the diffusion optical element 15, respectively.

As shown in FIGS. 4A and 4B, a large number of semi-cylindrical microlenses 15b are integrally formed adjacent to each other on the diffusion surface 15a of the diffusion optical element 15. The generatrix of the microlens 15b is parallel to the Y axis. The microlenses 15b are arranged without gaps along the arc shape of the diffusion surface 15a. In the configuration examples of FIGS. 4A and 4B, the microlens 15b is a protruding lens, but the microlens 15b may be a concave lens.

FIG. 4C is a diagram showing the optical action of the diffusion optical element 15. For convenience, FIG. 4C shows a state in which the optical system from the light source array 11 to the diffusion optical element 15 is developed in one plane. Further, in FIG. 4C, the number of laser light sources 11a is set to 5 for convenience.

The plurality of laser beams LB10 parallelized by the slow-axis cylindrical lens 13 are reflected by the mirror 14a and then incident on the diffused optical element 15 in the collimated state. At this time, each laser beam LB10 incident on the diffusion optical element 15 is separated from the adjacent laser beam LB10 by a predetermined distance. The pitch between the intensity centers of the adjacent incident regions 15c of the laser beam LB10 in the diffusion optical element 15 is the pitch between the laser light sources 11a, the lens surface design (curvature) of the slow axis cylindrical lens 13, and the mirror 14a and the diffusion optical element 15. It depends on the distance between them.

Each laser beam LB10 is diffused in a direction parallel to the XX plane by the microlens 15b on the diffusion surface 15a. At this time, each laser beam LB10 is incident on the diffusion surface 15a so as to pass through the plurality of microlenses 15b. As a result, each laser beam LB10 is diffused by the plurality of microlenses 15b at a spread angle of full-width θ10. The diffused laser light LB10 travels in different directions from the mirror 14a as a starting point. Further, each laser beam LB10 after diffusion overlaps with other laser beam LB10 due to diffusion. In this way, all the laser beams LB10 are diffused and overlapped with each other to generate a line beam B10 that spreads in the X-axis direction.

When the laser radar 1 is for in-vehicle use, for example, the line beam B10 is set to have a spread angle in the long side direction of 60 ° or more and a spread angle in the short side direction of 1 ° or less.

Returning to FIG. 1, the optical deflector 14 drives the mirror 14a by the drive signal from the mirror drive circuit 33, and scans the beam reflected from the mirror 14a in the Y-axis direction. As a result, the line beam B10 is scanned in the lateral direction (Y-axis direction). In the configuration of FIG. 1, in the state where the mirror 14a is in the neutral position, the mirror 14a is tilted by 45 ° with respect to the emission light axis of the laser light source 11a, but the tilt angle of the mirror 14a with respect to the emission light axis of the laser light source 11a. Is not limited to this. The tilt angle of the mirror 14a can be appropriately changed according to the layout of the line beam scanning optical system 10.

FIG. 5 is a diagram schematically showing the emission state of the laser beam of the laser radar 1 and the state of the line beam B10 in the target region. In the upper part of FIG. 5, the cross-sectional shape of the line beam B10 when viewed in the projection direction (Z-axis positive direction) is schematically shown.

As shown in FIG. 5, in the present embodiment, the laser radar 1 is mounted on the front side of the vehicle 200, and the line beam B10 is projected in front of the vehicle 200. The spread angle θ11 in the long side direction of the line beam B10 is, for example, 90 °. Further, the upper limit of the distance D11 capable of detecting an object is, for example, about 250 m. In FIG. 5, for convenience, the spread angle θ11 is expressed smaller than it actually is.

Returning to FIG. 1, the reflected light of the line beam B10 reflected from the target region is collected by the light receiving lens 21 on the light receiving surface of the light receiving element 22. The light receiving lens 21 is, for example, a camera lens unit for imaging composed of a plurality of lenses, and the light receiving element 22 is, for example, an image sensor or a sensor array in which pixels are arranged in a matrix in the vertical and horizontal directions. Among these, in the example of the sensor array, an avalanche photodiode sensor may be arranged at the position of each pixel. In this case, the avalanche photodiode is used, for example, in Geiger mode (Geiger multiplication mode). In Geiger mode, when a photomultiplier is incident on an avalanche photodiode, the avalanche multiplier causes the charge collected on the cathode of the avalanche photodiode to be multiplied to the saturated charge amount. Therefore, the presence or absence of light incident on the pixel is detected with high sensitivity, and distance measurement at a longer distance becomes possible.

The light receiving element 22 has, for example, a rectangular light receiving surface, and is arranged so that the long side of the light receiving surface is parallel to the X axis. The long side direction of the light receiving surface of the light receiving element 22 corresponds to the long side direction of the line beam B10 in the target region. The reflected light of the line beam B10 is imaged on the light receiving surface of the light receiving element 22 by the light receiving lens 21 so as to extend along the long side direction of the light receiving surface.

Here, the pixel position in the X-axis direction of the light receiving surface corresponds to the position in the X-axis direction in the target region. Further, the pixel position of the light receiving surface in the Y-axis direction corresponds to the position in the Y-axis direction in the target region. When the line beam B10 is scanned in the Y-axis direction, the reflected light of the line beam B10 moves in the Y-axis direction on the light receiving surface of the light receiving element 22. Therefore, it is possible to detect at which position in the X-axis direction and the Y-axis direction of the target region the object exists, depending on the position of the pixel in which the received light signal is generated.

A licensor in which pixels are arranged in the X-axis direction may be used as the light receiving element 22. In this case, the Y position of the object to be detected is specified in synchronization with the movement of the line beam B10.

The laser radar 1 includes a controller 31, a laser drive circuit 32, a mirror drive circuit 33, and a signal processing circuit 34 as a circuit unit configuration.

The controller 31 includes an arithmetic processing circuit such as a CPU (CentralProcessingUnit) and a storage medium such as a ROM (ReadOnlyMemory) and a RAM (RandomAccessMemory), and controls each part according to a preset program. The laser drive circuit 32 causes each laser light source 11a of the light source array 11 to emit pulses in response to control from the controller 31. The controller 31 causes each laser light source 11a to repeatedly emit a pulse a plurality of times at a timing when the moving position of the reflected light of the line beam B10 is included in each pixel row of the light receiving element 22. At the time of pulse emission, the laser drive circuit 32 causes each laser light source 11a to emit a pulse at the same time. Alternatively, each laser light source 11a may be made to emit pulses in order with a predetermined time difference.

The mirror drive circuit 33 drives the optical deflector 14 according to the control from the controller 31. The optical deflector 14 rotates the mirror 14a with respect to the rotation axis R1 to scan the line beam B10 in the short side direction of the line beam B10.

The signal processing circuit 34 outputs the light receiving signal of each pixel of the light receiving element 22 to the controller 31. As described above, the controller 31 can detect the position of the object in the X-axis direction of the target region based on the position of the pixel in which the received light signal is generated. Further, the controller 31 is based on the time difference between the timing at which the light source array 11 is pulsed and the timing at which the light receiving element 22 receives the reflected light from the target region, that is, the timing at which the light receiving signal is received from the light receiving element 22. , Get the distance to the object in the target area.

In this way, the controller 31 detects the presence or absence of an object in the target region by scanning the line beam B10 with the light deflector 14 while causing the light source array 11 to emit light in pulses, and further determines the position of the object and the distance to the object. measure. These measurement results are transmitted to the control unit on the vehicle side at any time.

Next, the setting method of the line beam scanning optical system 10 will be described.

FIG. 6A is a diagram schematically showing the arrangement of each member in the line beam scanning optical system 10. For convenience, FIG. 6A also shows a state in which the optical system from the light source array 11 to the diffusion optical element 15 is developed in one plane, as in FIG. 4C.

In FIG. 6A, Fp1 is the focal position of the slow-axis cylindrical lens 13 on the laser light source 11a side (hereinafter, referred to as “front focal position”), and Fp2 is the optical deflector 14 side of the slow-axis cylindrical lens 13. Focus position (hereinafter referred to as "rear focal position"). In FIG. 6A, the straight line extending from each laser light source 11a indicates the optical axis of the laser light emitted from each laser light source 11a.

As shown in FIG. 6A, the light source array 11 is arranged so that the emission end surface of the laser light source 11a coincides with the front focal position Fp1. As a result, each laser beam emitted from each laser light source 11a is incident on the slow-axis cylindrical lens 13 while diverging, and is converted into parallel light by the refraction action thereof. At that time, since the optical axis of each laser beam is in a positional relationship of incident parallel to the optical axis of the slow axis cylindrical lens regardless of the distance to the light source array, the light is focused near the rear focal position Fp2. NS. The mirror 14a is arranged near the focusing position of the optical axis of each laser beam, that is, near the rear focal position Fp2.

The arrangement position of the mirror 14a does not necessarily have to coincide with the rear focal position Fp2, and the mirror is within the range W10 capable of receiving the beam (bundle of all laser light) focused by the slow axis cylindrical lens 13. 14a may be arranged. After being reflected by the mirror 14a, the laser beams travel in directions away from each other. At this time, since each laser beam is collimated by the slow axis cylindrical lens 13 as described above, each laser beam is separated from each other and incident on the diffuse optical element 15.

Here, when the projection surface P1 perpendicular to the Z axis is set on the rear side of the diffusion optical element 15, the distance between the intensity centers of the laser light on the diffusion optical element 15, that is, the incident position of the laser light with respect to the diffusion surface 15a is set. The distance between the incident positions when projected onto the projection surface P1 is preferably set to 10 mm or more from the viewpoint of ensuring eye safety, as described below.

FIG. 6B shows the acceptance angle of the special light source with respect to the human eye (naked eye) when measuring the exposure emission amount of the pulse laser based on the “Safety Standards for Laser Products” (JIS C 6802: 2014). It is a figure.

Here, it is assumed that the viewing angle α of the pearl light source is larger than the minimum value of 1.5 mrad (when the pearl light source is a distributed light source). When the wavelength of the laser beam is larger than 600 nm and 1400 nm or less, the measurement conditions applied to determine the exposure dose when the scanning beam that repeats pulse emission is incident on the naked eye are as follows.

Measurement distance ... 100 mm
Aperture diameter: 7 mm (equivalent to human pupil diameter)
Maximum viewing angle α _max … 5 to 100 mrad (depending on the pulse duration of the laser beam)

When the measurement is performed under these observation conditions, the maximum width of the apparent light source is when the maximum viewing angle α _max is 100 mrad, and is a region having a diameter of 10 mm. This region needs to be applied to all positions on the appropriate light source, but no matter where it is, the energy emitted from the range W20 of the viewing angle α outside the _{maximum viewing angle α max for each position is eye safe.} It does not contribute to the amount of exposure compared to the reference energy of. That is, eye safety can be ensured if the amount of exposure emission from the appropriate light source in the range of the maximum width of 10 mm is equal to or less than the class 1 accessible emission limit (AEL).

In the configuration of FIG. 6A, since the laser beam is diffused by the diffusing optical element 15 to generate the line beam B10, the light emitting region of the line beam B10 on the diffusing surface 15a of the diffusing optical element 15 is an eye-safe determination target. It becomes an effective light source of. In this case, when the distance D1 (distance between intensity centers) between the laser beams projected on the projection surface P1 is 10 mm or more in the maximum width of FIG. 6B, two or more lasers are in the range of this maximum width. Since light (a range of 1 / e ² or more of the peak intensity) is not included, the radiant energy of each laser beam may meet the eye safe standard. That is, when the distance D1 between the laser beams is 10 mm or more in the maximum width shown in FIG. 6 (b), the emission intensity (radiant energy) of each laser light source 11a can be increased to near the standard of eye safe.

On the other hand, when the distance D1 between the laser beams is less than the maximum width of 10 mm in FIG. 6 (b), the maximum width includes a plurality of laser beams ( ^{range of 1 / e 2} or more of the peak intensity) and the radiant energy is increased. It will be accumulated. Therefore, in this case, it is necessary to reduce the emission intensity of each laser light source 11a so that the integrated radiant energy satisfies the eye safe standard. As a result, the amount of light of the entire line beam B10 is reduced as compared with the case where the distance D1 between the laser beams is 10 mm or more in the maximum width shown in FIG. 6B.

From the above, by adjusting the arrangement of the diffusion optical elements 15 so that all the distances D1 between the laser beams on the projection surface P1 are _{10 mm or more in the maximum width defined by the maximum viewing angle α max (100 mrad).} The emission intensity of each laser light source 11a can be increased to near the standard of eye safe, and the amount of light of the line beam B10 can be increased more effectively. As a result, the range-finding range of the laser radar 1 can be expanded more remarkably while ensuring eye safety.

<Effect of embodiment>
According to this embodiment, the following effects are achieved.

Since the laser beam is diffused by the diffusing optical element 15 to generate the line beam B10, the light emitting region of the line beam B10 on the diffusing surface 15a of the diffusing optical element 15 becomes an effective light source for eye safe determination. When the diffusing optical element 15 is not used, a minute region where the laser beams overlap on the mirror 14a of the optical deflector 14 becomes an appropriate light source for eye safe determination. Therefore, according to the present embodiment, the light emitting area of the exclusive light source can be remarkably expanded and the influence of the line beam B10 on the human eye can be remarkably suppressed as compared with the case where the diffusion optical element 15 is not used. Therefore, it is possible to suppress the influence of the line beam B10 on the human eye while effectively increasing the amount of light of the line beam B10 by arranging a plurality of laser light sources 11a. Therefore, it is possible to improve the safety of the laser radar 1 while expanding the distance range in which the object can be detected.

Further, since the plurality of laser beams are incident on the diffused optical element 15 in a state of being collimated, the light rays of each laser beam are incident on the diffused optical element 15 at substantially the same incident angle. Therefore, the diffusion optical element 15 can appropriately beam-shape each laser beam into a predetermined diffusion state.

As described with reference to FIGS. 6 (a) and 6 (b), the distance (distance D1) between the intensity centers of the plurality of laser beams in the diffusion optical element 15 is preferably 10 mm or more. As a result, as described above, the emission intensity of each laser light source 11a can be increased to near the standard of eye safe, and the amount of light of the line beam B10 can be increased more effectively. As a result, the ranging range of the laser radar 1 can be expanded more remarkably.

As shown in FIGS. 2, 4 (a) and 6 (a), in the diffusion optical element 15, the diffusion surface 15a for diffusing the laser beam is centered on the mirror 14a and is aligned with the rotation axis R1 of the mirror 14a. It is curved in an arc shape in the parallel direction. As a result, the laser beams reflected by the mirror 14a can be incident on the diffusion surface 15a in the same incident state. Therefore, the design of the diffusion optical element 15 can be facilitated, and each laser beam can be appropriately beam-shaped to a predetermined diffusion state.

As shown in FIG. 2, the lens unit 40 includes a fast-axis cylindrical lens 12 (first lens) that collimates the laser light emitted from the plurality of laser light sources 11a in the fast-axis direction (first direction). , The plurality of laser beams parallelized in the fast axis direction by the fast axis cylindrical lens 12 are collimated in the slow axis direction (second direction) perpendicular to the fast axis direction, and parallelized in the slow axis direction. A slow-axis cylindrical lens 13 (second lens) that concentrates a plurality of laser beams on the mirror 14a is provided. In this way, by individually performing parallel lightening in the fast axis direction and parallel lighting in the slow axis direction with the fast axis cylindrical lens 12 and the slow axis cylindrical lens 13, the parallel lightening in each direction can be finely adjusted. It is possible to make each parallel light accurately. Further, by combining the slow-axis cylindrical lens 13 with a light source array 11 in which light emitting regions of a plurality of laser light sources are arranged in a row in the slow-axis direction, the mirror 14a has an action of condensing the optical axes of each laser light. This makes it possible to reduce the number of parts and simplify the configuration.

As shown in FIG. 2, the plurality of laser light sources 11a are end face emitting semiconductor lasers and are arranged side by side along the slow axis direction, and the fast axis cylindrical lens 12 transmits the plurality of laser lights to the fast axis. The slow-axis cylindrical lens 13 parallelizes the light in the direction, and the plurality of laser beams are parallel-lighted in the slow-axis direction and focused on the mirror 14a. In this way, the fast-axis cylindrical lens 12 can be miniaturized and the width in the short side direction of the line beam B10 can be reduced by making the fast-axis cylindrical lens 12 into parallel light first in the fast-axis direction having a large divergence angle. can.

<Change example 1>
In the above embodiment, the diffusion surface 15a of the diffusion optical element 15 is curved in an arc shape, but the diffusion surface 15a of the diffusion optical element 15 may be flat.

FIG. 7A is a diagram showing a configuration example in this case.

In this configuration example, as shown in FIG. 7A, the flat plate-shaped diffusion optical element 15 is arranged after the mirror 14a. The diffusion optical element 15 is arranged so that the entrance surface and the exit surface are perpendicular to the Z axis. Similar to the above embodiment, a large number of semi-cylindrical microlenses are formed on the diffusing surface 15a (exiting surface) of the diffusing optical element 15. In the microlens, the generatrix is parallel to the Y-axis direction and is arranged without a gap in the X-axis direction. The laser beams diffused by the microlens overlap each other to generate the line beam B10.

Also in this configuration example, as in the above embodiment, the light emitting region of the line beam B10 on the diffusing surface 15a of the diffusing optical element 15 becomes the apparent light source to be determined by the eye safe, so that the light emitting area of the apparent light source is remarkably expanded. The effect of the line beam B10 on the human eye can be remarkably suppressed. Therefore, it is possible to suppress the influence of the line beam B10 on the human eye while effectively increasing the amount of light of the line beam B10 by arranging a plurality of laser light sources 11a.

In the configuration example of FIG. 7A, the appearance shape of the diffusion optical element 15 is simpler than that of the above embodiment. However, since the incident angle with respect to the diffusing optical element 15 is different for each laser beam, the diffusing surface 15a (microlens) of the diffusing optical element 15 is provided for each incident region of the laser beam so that each laser beam is properly beam-shaped. The design needs to be adjusted. Therefore, the design of the diffusion surface 15a becomes slightly complicated as compared with the above embodiment.

Also in this configuration example, it is preferable that the diffusion optical element 15 is arranged so that the distance D1 is 10 mm or more, as in the above embodiment. As a result, the emission intensity of each laser light source 11a can be increased to near the standard of eye safe, and the amount of light of the line beam B10 can be increased more effectively.

Further, as shown in FIG. 7B, the slow axis cylindrical lens 13 may be configured so that the distance D1 between the laser beams on the incident surface of the diffusion optical element 15 is constant. Also in this case, it is preferable that the diffusion optical element 15 is arranged so that the distance D1 is 10 mm or more. As a result, the emission intensity of each laser light source 11a can be increased to near the standard of eye safe, and the amount of light of the line beam B10 can be increased more effectively.

In FIG. 6A, the lens surface 13a of the slow axis cylindrical lens 13 is configured so that the angular pitch of the laser beam is constant, but also in the configuration of FIG. 6A, the projection surface P1 is formed. The slow axis cylindrical lens 13 may be configured so that the distance D1 between the laser beams is constant. Also in this case, it is preferable that the diffusion optical element 15 is arranged so that the distance D1 is 10 mm or more.

<Change example 2>
In the above embodiment, the diffusion surface 15a of the diffusion optical element 15 is curved in an arc shape in the X-axis direction, but the diffusion surface 15a of the diffusion optical element 15 may be curved in an arc shape in the Y-axis direction.

8 (a) and 8 (b) are diagrams showing a configuration example in this case.

In this configuration example, a plate-shaped diffusion optical element 15 curved in an arc shape in the Y-axis direction is arranged after the mirror 14a. The diffusion optical element 15 has a shape obtained by cutting out a part of a cylinder along a generatrix. The diffusion optical element 15 is arranged so that the generatrix of the cylinder is parallel to the X-axis. The central bus in the circumferential direction is aligned with the rotation axis R1 of the mirror 14a in the Z-axis direction. The diffusion optical element 15 is arranged at a position where the center of the circle including the arc is positioned on a straight line parallel to the X axis passing through the center of the mirror 14a.

A large number of microlenses having a semicircular cross section are formed on the diffusion surface 15a (exit surface) of the diffusion optical element 15. The ridges of the microlenses extend in the direction along the arc (circumferential direction of the diffusion optical element 15), and are arranged without gaps in the X-axis direction. Also in this case, the laser beams diffused by the microlens overlap each other to generate the line beam B10.

Further, in this configuration example, even if the mirror 14a rotates and each laser beam is scanned, the incident angle of each laser beam with respect to the diffusion surface 15a of the diffusion optical element 15 does not substantially change. Therefore, the design of the diffusion surface 15a can be simplified in the scanning direction of the line beam B10, and each laser beam can be appropriately beam-shaped at each scanning position of the line beam B10. On the other hand, as in the above modification 1, since the incident angle with respect to the diffused optical element 15 is different for each laser beam, the diffused optical element 15 is provided for each incident region of the laser beam so that each laser beam is properly beam-shaped. It is necessary to adjust the design of the diffusion surface 15a (microlens).

In this configuration example as well, it is preferable that the diffusion optical element 15 is arranged so that the distance D1 between the laser beams on the incident surface of the diffusion optical element 15 is 10 mm or more, as in the above embodiment. As a result, the emission intensity of each laser light source 11a can be increased to near the standard of eye safe, and the amount of light of the line beam B10 can be increased more effectively.

Further, as in FIG. 7B, the slow axis cylindrical lens 13 may be configured so that the distance D1 between the laser beams on the incident surface of the diffusion optical element 15 is constant. Also in this case, it is preferable that the diffusion optical element 15 is arranged so that the distance D1 is 10 mm or more.

Further, the diffusion surface 15a may be curved in an arc shape around the center of the mirror 14a in both the X-axis direction and the Y-axis direction.

<Change example 3>
In the above embodiment, as shown in FIGS. 3A to 3C, each laser light source 11a has one light emitting region 117, but each laser light source 11a has a plurality of light emitting regions 117 in the fast axis direction. You may prepare.

9 (a) to 9 (c) are diagrams showing a configuration example in this case.

As shown in FIG. 9A, in this configuration example, a plurality of light emitting regions 117 are formed so as to be arranged in the fast axis direction (Z axis direction) in one laser light source 11a. A pair of the active layer 111, the N-type clad layer 112, and the P-type clad layer 113 are laminated via the tunnel junction layer 119 between the N-type substrate 114 and the contact layer 115. As a result, three light emitting regions 117 are formed.

Similar to the case of FIG. 3A, in the light emitting region 117, the width W1 in the direction parallel to the active layer 111 is wider than the width W2 in the direction perpendicular to the active layer 111. By applying a drive current to the electrode 116, laser light is emitted from each of the three light emitting regions 117, as shown in FIG. 9B. The beam B20 has a divergence angle in the direction parallel to the fast axis 118a larger than that in the direction parallel to the slow axis 118b. Therefore, the beam B20 has an elliptical shape that is long in the fast axis direction.

In this configuration example, as shown in FIG. 9C, a plurality of laser light sources 11a are arranged so as to be arranged in the slow axis direction to form the light source array 11. As a result, the plurality of light emitting regions 117 are arranged so as to line up not only in the slow axis direction but also in the fast axis direction. In this case as well, one semiconductor light emitting element formed so that the plurality of light emitting regions 117 are arranged in the slow axis direction and the fast axis direction may be installed on the base 120.

In this configuration example, the number of light emitting regions 117 is increased as compared with the configuration of FIG. 3C, so that the amount of light of the line beam B10 can be increased. However, in this configuration, as shown in FIG. 10A, the positions of the upper and lower light emitting regions 117 are displaced with respect to the optical axis of the fast axis cylindrical lens 12, so that the laser light emitted from these light emitting regions 117 The central axis is tilted by the fast axis cylindrical lens 12.

Here, assuming that the displacement amount of the light emitting region 117 with respect to the optical axis of the fast axis cylindrical lens 12 is d1 and the focal length of the fast axis cylindrical lens 12 is f1, the tilt angle θ1 of the central axis of the laser beam emitted from the light emitting region 117. Can be specified by the following equation.

θ1 = tan ^-1 (d1 / f1) ... (1)

As described above, the laser light emitted from the upper and lower light emitting regions 117 travels in a direction inclined in the fast axis direction with respect to the laser light emitted from the central light emitting region 117, so that the line beam is compared with the above embodiment. The short side direction of B10 is widened. Here, in order to suppress the spread of the line beam B10 in the short side direction, it is preferable to make the interval (displacement amount d1) of the light emitting regions 117 arranged in the fast axis direction as narrow as possible based on the above equation (1). It is preferable that the distance between the light emitting regions 117 arranged in the fast axis direction is at least smaller than the distance between the laser light sources 11a. Further, the focal length of the fast-axis cylindrical lens 12 is preferably as long as possible. As a result, the inclination angle θ1 can be reduced, and the spread of the line beam B10 in the short side direction can be suppressed.

When the fast axis is made parallel light by the fast axis cylindrical lens 12 with respect to the light source array 11 in which the light emitting regions are arranged in the fast axis direction as described above, the number of line beams corresponding to the number of light emitting regions arranged in the fast axis is formed. Will be done. In this case, it is possible to detect a plurality of lines at the same time. If there is not one line and there is a problem in system processing, the spread angle in the short side direction of the line is sacrificed, but by slightly shifting the arrangement position of the light source array 11 from the focal position of the fast axis cylindrical lens 12. , It is also possible to widen the divergence angle of the line beams and stack each line beam into one.

In the above embodiment, since the plurality of laser light sources 11a are arranged in only one row, as shown in FIG. 10B, the laser light emitted from the light emitting region 117 is fast-axis by the fast-axis cylindrical lens 12. It can be made into substantially parallel light in the direction. Therefore, the spread can be suppressed in the short side direction of the line beam B10, and the object can be efficiently detected farther.

<Change example 4>
In the above embodiment, as shown in FIG. 11A, a circular mirror can be used as the mirror 14a arranged in the light deflector 14. Here, the light deflector 14 is configured by a MEMS mirror. In this case, the optical deflector 14 has a square support portion 14b in a plan view, a frame portion 14c surrounding the support portion 14b, and a support portion 14b and a frame portion 14c at an intermediate position between the opposite sides of the support portion 14b. It is provided with a beam portion 14d for connecting the above. A mirror 14a is installed on the upper surface of the support portion 14b. The support portion 14b is rotated around the two beam portions 14d by a drive portion (not shown). The axis connecting the two beam portions 14d is the rotation axis R1 of the support portion 14b and the mirror 14a. The beam is incident on the mirror 14a in the direction of the dashed arrow.

FIG. 11B is a plan view of the vicinity of the mirror 14a. As described above, the laser light sources 11a are aligned in the slow axis direction, and the light emitted from the laser light source 11a is collimated by the fast-axis cylindrical lens 12 arranged in the immediate vicinity of the laser light source 11a, so that the light is incident on the mirror 14a. As shown in FIG. 11B, the shape of the beam spot BS1 of the beam is long in the slow axis direction. Therefore, when the shape of the mirror 14a is circular, an extra region in which the beam does not enter is widely generated in the mirror 14a.

On the other hand, in the present modification 4, as shown in FIGS. 12A and 12B, a mirror 14e having a long shape in one direction is installed in the optical deflector 14. That is, the elliptical mirror 14e is installed on the support portion 14b so that the longitudinal direction is parallel to the direction corresponding to the slow axis direction (arrangement direction of the laser light sources 11a). As a result, as compared with the circular mirror 14a shown in FIG. 10A, the region of the extra mirror 14e where the beam does not enter can be reduced, and the weight of the mirror 14e can be reduced. As a result, when the mirror 14e is driven at a constant angle, the stress generated in the support portion 14b of the mirror 14e can be reduced, a larger deflection angle can be realized, or a MEMS mirror with high robustness can be realized. Further, the dynamic deflection (distortion or deformation of the mirror 14e) generated when the mirror 14e is driven can be reduced. Therefore, the line beam B10 can be scanned more stably.

The shape of the mirror 14e does not necessarily have to be an ellipse, and may be a shape that is long in one direction. For example, the shape of the mirror 14e may be an oval, a track shape, a rectangle, or the like. Also in the above embodiment, the shape of the mirror 14a is not limited to a circle, and may be another shape such as a square.

<Other changes>
In the above embodiment and each modification, the diffusion surface 15a is arranged on the exit surface of the diffusion optical element 15, but the diffusion surface 15a may be arranged on the incident surface of the diffusion optical element 15. Further, the diffusion optical element 15 is not limited to the microlens array, and other optical elements such as a diffraction optical element may be used as long as the laser beam can be diffused in the long side direction of the line beam B10. ..

Further, in the above embodiment, the diffusion optical element 15 has a plate-like shape, but the shape of the diffusion optical element 15 is not limited to this. For example, in FIG. 2, the shape of the diffusion optical element 15 when viewed in the Y-axis direction may be a semi-cylindrical shape. In this case, the diffusion optical element 15 is made of a member whose incident surface is a flat surface and whose exit surface is an arcuate curved surface, and a diffusion surface 15a similar to that of the above embodiment is formed on the emission surface. Similarly, the diffusion optical element 15 shown in FIGS. 8A and 8B may have a semi-cylindrical shape.

In the above embodiment, an end face emitting laser diode is used as the laser light source 11a, but a light source array 11 in which surface emitting laser light sources such as VCSEL (Vertical Cavity Surface Emitting Laser) are arranged in a linear or matrix shape is used. May be done.

Further, in the above embodiment, as shown in FIG. 5, the horizontally long line beam B10 is scanned in the vertical direction, but the vertically long line beam may be scanned in the horizontal direction. In this configuration, the spread angle of the line beam B10 in the long side direction is small, but the swing angle of the line beam B10 in the horizontal direction is large.

Further, in the above embodiment, the MEMS mirror is used as the light deflector 14, but another light deflector such as a magnetically movable mirror or a galvano mirror may be used as the light deflector 14.

Further, in the above embodiment, the line beam scanning optical system 10 is configured such that the light source array 11, the fast axis cylindrical lens 12, the slow axis cylindrical lens 13, and the optical deflector 14 are arranged in one direction. The layout of the system 10 is not limited to this. For example, the line beam scanning optical system 10 may be configured so as to arrange a mirror in the middle of the optical path and bend the optical path. Further, the first cylindrical lens may be arranged on the rear side of the second cylindrical.

Further, the number of laser light sources 11a arranged in the light source array 11 is not limited to the number illustrated in the above embodiment. Further, the plurality of laser light sources 11a do not necessarily have to be unitized, and the plurality of laser light sources may be individually arranged.

Further, in the above embodiment, the laser radar 1 is mounted on the vehicle 200, but the laser radar 1 may be mounted on another moving body. Further, the laser radar 1 may be mounted on a device or equipment other than the mobile body. Further, the laser radar 1 may have only the function of detecting an object.

Further, the first cylindrical lens and the second cylindrical lens may be integrated and configured as aspherical toroidal lenses having different slow and fast axes. The configuration of the lens unit 40 can be variously changed.

In addition, various modifications of the embodiment of the present invention can be made as appropriate within the scope of the technical idea shown in the claims.

1 ... Laser radar 10 ... Line beam scanning optical system 11a ... Laser light source 12 ... Fast axis cylindrical lens (1st lens or 2nd lens)
13 ... Slow axis cylindrical lens (second lens or first lens)
14 ...

Optical deflectors

14a, 14e ... Mirror 15 ... Diffusing optical element 15a ... Diffusing surface 20 ... Light receiving optical system 40 ... Lens unit 117 ... Light emitting area 118a ... Fast axis 118b ... Slow axis

Claims

A line beam scanning optical system that generates a long line beam in one direction and scans the line beam in the short side direction thereof.
A plurality of laser light sources arranged side by side in the direction corresponding to the long side of the line beam,
An optical deflector having a mirror that deflects the line beam in the short side direction, and
A lens unit that collimates the laser beams emitted from the plurality of laser light sources and concentrates the parallelized laser beams on the mirror.
A diffusion optical element that diffuses the plurality of laser beams reflected by the mirror in the long side direction, respectively, is provided.
Each of the plurality of laser beams is incident on the diffusion optical element in a state of being collimated by the lens portion.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to claim 1,
The distance between the intensity centers of the plurality of laser beams in the diffusion optical element is 10 mm or more.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to claim 1 or 2.
In the diffusion optical element, the diffusion surface for diffusing the laser beam is curved in an arc shape in a direction parallel to the rotation axis of the mirror with the mirror as the center.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to any one of claims 1 to 3.
In the diffusion optical element, the diffusion surface for diffusing the laser beam is curved in an arc shape in a direction perpendicular to the rotation axis of the mirror with the mirror as the center.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to claim 1 or 2.
The diffusion optical element has a flat diffusion surface for diffusing the laser beam.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to any one of claims 1 to 5.
The lens unit
A first lens that collimates the laser light emitted from the plurality of laser light sources in the first direction, and
The plurality of laser beams collimated in the first direction by the first lens are collimated in a second direction perpendicular to the first direction, and the plurality of laser beams collimated in the second direction. A second lens that collects the laser light of the above on the mirror.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to claim 6,
The plurality of laser light sources are end face emitting semiconductor lasers, which are arranged side by side along the slow axis direction.
The first lens collimates the plurality of laser beams in the fast axis direction.
The second lens parallelizes the plurality of laser beams in the slow axis direction and collects them on the mirror.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to any one of claims 1 to 7.
Each of the laser light sources includes a plurality of light emitting regions in a direction perpendicular to the alignment direction, and the distance between the light emitting regions is smaller than the distance between the laser light sources.
A line beam scanning optical system characterized by this.
In the line beam scanning optical system according to any one of claims 1 to 8.
The mirror has a long shape in one direction, and is arranged so that the longitudinal direction of the shape is parallel to the direction corresponding to the alignment direction.
A line beam scanning optical system characterized by this.
The line beam scanning optical system according to any one of claims 1 to 9.
A light receiving optical system that receives reflected light from an object of laser light projected from the line beam scanning optical system is provided.
A laser radar characterized by that.