Scanning optics and laser radar

Abstract

The objective is to maintain image quality while miniaturizing the device. [Solution] The scanning optical system comprises a light projecting and receiving system 50 consisting of a light source and a light projecting optical system 501 that irradiates the projecting light beam from the light source, and a light receiving element array 55 and a light receiving optical system 502 that guides the reflected received light beam to the light receiving elements of the light receiving element array 55, and a rotating mirror body 53 that rotates around a rotation axis, scans the projecting light beam and the received light beam, and has only a pair of reflective surfaces aligned in the rotation axis direction, the rotation axis coinciding with the center of gravity of the rotating mirror body 53, and the light receiving element array 55 has multiple light receiving elements arrayed in the sub-scanning direction.

Description

[Technical Field]

[0001] The present invention relates to a scanning optical system and a laser radar. [Background technology]

[0002] Laser radar irradiates a measurement space with laser light and measures the distance to an object in the measurement space based on the time between the irradiation and the reception of the reflected light (see, for example, Patent Document 1).

[0003] The scanning optical system used in such laser radars is equipped with a polygon mirror, and scans the measurement space by reflecting laser light off the rotating polygon mirror, and receives the reflected light from objects with a light receiving means such as a photodiode. This polygon mirror has multiple reflective surfaces that are angled slightly differently relative to the rotation axis. By using such a polygon mirror, the laser radar sequentially changes the direction of laser light emission in the vertical direction (sub-scanning direction) to scan the measurement space two-dimensionally. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5754564 Summary of the Invention [Problem to be solved by the invention]

[0005] While miniaturization is required for laser radar, there is also a demand for higher image quality. Simply increasing the number of polygon mirror faces to achieve higher image quality would result in the device becoming larger.

[0006] The present invention has been made in view of the above circumstances, and has as its object to maintain high image quality while miniaturizing the device. [Means for solving the problem]

[0007] The above object of the present invention can be achieved by the following means.

[0008] (1) a light projecting and receiving system including a light source, a light projecting optical system for irradiating a light projecting beam from the light source, and a light receiving optical system for guiding a light receiving element array and a reflected light receiving beam to a light receiving element of the light receiving element array; a rotating mirror body that rotates around a rotation axis, scans the projected light beam and the received light beam, and has only a pair of reflecting surfaces aligned in the direction of the rotation axis; the rotation axis coincides with the center of gravity of the rotating mirror body, The light receiving element array is a scanning optical system in which a plurality of light receiving elements are arrayed at least in the sub-scanning direction.

[0009] (2) The scanning optical system according to (1) above, wherein the light beam projected from the light source is elongated vertically in the sub-scanning direction.

[0010] (3) The scanning optical system according to (1) above, wherein the light receiving element array is an array that is vertically long in the sub-scanning direction.

[0011] (4) The scanning optical system according to (1) above, wherein the optical axes of the light projecting optical system and the light receiving optical system are arranged coaxially.

[0012] (5) The scanning optical system according to (1) above, wherein the rotation axis of the rotating mirror body is disposed within the reflecting surface when viewed from the rotation axis direction.

[0013] (6) A scanning optical system as described in (5) above, wherein, when viewed from the direction of the rotation axis, the rotation axis of the rotating mirror body is positioned within the range of the reflecting surface where the projected light beam and the received light beam impinge.

[0014] (7) A scanning optical system according to any one of (1) to (6) above; A laser radar that measures the distance to an object based on the timing of light emission from the light source and the timing of light reception by the light receiving element. [Effects of the Invention]

[0015] The scanning optical system according to the present invention includes a light projecting and receiving system including a light source and a light projecting optical system that projects a light beam from the light source, a light receiving element array and a light receiving optical system that guides the reflected light beam to the light receiving elements of the light receiving element array, and a rotating mirror that rotates about a rotation axis to scan the light projecting and receiving light beams and has only a pair of reflective surfaces aligned in the rotation axis direction, the rotation axis coinciding with the center of gravity of the rotating mirror, and the light receiving element array having a plurality of light receiving elements arrayed in the sub-scanning direction. This makes it possible to maintain high image quality while miniaturizing the device. [Brief explanation of the drawings]

[0016] Advantages and features provided by one or more embodiments of the present invention will be more fully understood from the following detailed description and the accompanying drawings, which are for purposes of illustration only and are not intended to be limiting. [Figure 1] 1 is a cross-sectional view showing a laser radar according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a general configuration of a rotating mirror body. [Figure 3] FIG. 2 is a schematic diagram showing a general configuration of a rotating mirror body. [Figure 4] FIG. 2 is a block diagram showing the configuration of a control unit of the laser radar. [Figure 5] FIG. 10 is a schematic diagram showing the configuration of a non-coaxial type. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of a coaxial type in the second embodiment. [Figure 7] 10A and 10B are diagrams illustrating the structure of a scanning optical system and the area of ​​a rotating body in a second embodiment. [Figure 8] 10A and 10B are diagrams illustrating the structure of a scanning optical system and the area of ​​a rotating body in a comparative example. [Figure 9] 10A and 10B are diagrams illustrating the structure of a scanning optical system and the area of ​​a rotating body in a third embodiment. [Figure 10]10A and 10B are diagrams illustrating the structure of a scanning optical system and the area of ​​a rotating body in a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0018] FIG. 1 is a cross-sectional view showing a laser radar 10 (hereinafter also referred to as LiDAR (Light Detection and Ranging)) according to this embodiment. The LiDAR 10 includes a scanning optical system 11 and a control unit 12, and is housed in a housing 57. In the following, the Z direction is the up-down direction, and the XY plane is the horizontal plane. The Y direction is roughly the irradiation direction of the laser projection light beam. The Z direction is the direction of the rotation axis. In the following, the X direction is also referred to as the main scanning direction, and the Z direction is also referred to as the sub-scanning direction.

[0019] The lidar 10 includes a scanning optical system 11 and a control unit 12 and is housed in a housing 57 .

[0020] The scanning optical system 11 has a semiconductor laser 51 as a light source, a first optical element 52, a rotating mirror body 53, a second optical element 54, a light receiving element array 55, and a motor 56. The semiconductor laser 51 and the first optical element 52 constitute a light projecting optical system 501. The second optical element 54 and the light receiving element array 55 constitute a light receiving optical system 502. The light projecting optical system 501 and the light receiving optical system 502 constitute a light projecting and receiving system 50.

[0021] (Light projection optical system 501) For example, an edge-emitting laser (EEL) is used as the semiconductor laser 51. Alternatively, a vertical-cavity surface-emitting laser (VCSEL) array may be used as the semiconductor laser 51. The arrangement direction of the EEL is determined so that the projected light beam of the semiconductor laser 51 is vertically long (the length in the sub-scanning direction is longer than the length in the main scanning direction). Alternatively, the long sides of the EEL may be arrayed in the sub-scanning direction. Alternatively, multiple VCSEL laser light sources may be arranged. The aspect ratio of the projected light beam is any value within the range of, for example, 1:5 to 1:200.

[0022] The first optical element 52 is configured with a collimating lens or a collimating lens and another optical lens. The first optical element 52 converts the light emitted from the semiconductor laser 51 into parallel light. The vertically elongated projection light beam described above may be obtained by the cooperation of the semiconductor laser 51 and the first optical element 52. In other words, the vertically elongated projection light beam is realized by the optical lens of the first optical element 52.

[0023] FIG. 2 is a schematic diagram showing the overall configuration of the rotating mirror body 53. As shown in FIGS. 1 and 2, the rotating mirror body 53 as a whole has a shape formed by two stacked hexahedrons. The rotating mirror body 53 rotates around a rotation axis 530. The rotation direction is, for example, counterclockwise when viewed from above, as indicated by the arrows in FIGS. 1 and 2. The rotating mirror body 53 is composed of a main body 531 and a weight (balancer) 532. The main body 531 is composed of an upper portion 3a, a lower portion 3c, and a plate-shaped central support portion 3b. The upper portion 3a, the lower portion 3c, and the central support portion 3b are integrally formed. The main body 531 (upper portion 3a, lower portion 3c) of the rotating mirror body 53 is hollow. The central support portion 3b of the main body 531 is connected to a motor shaft 56a (see FIG. 1) of a motor 56 fixed to a housing 57, and the entire rotating mirror body 53 is rotated. 1, the axis (axis of rotation) of motor shaft 56a extends in the Z direction, which is the vertical direction, and the XY plane, which is made up of the X and Y directions perpendicular to the Z direction, is the horizontal plane. However, the present invention is not limited to this, and the axis of motor shaft 56a may be tilted with respect to the vertical direction.

[0024] Rotating mirror body 53 also has a pair of reflecting surfaces M1 and M2 aligned in the direction of the rotation axis (Z direction). These reflecting surfaces M1 and M2 are formed, for example, by depositing a reflective film on the surface of a resin material (e.g., PC (polycarbonate)) shaped like main body 531 of rotating mirror body 53. The reflecting surfaces of rotating mirror body 53 are formed only by the pair of reflecting surfaces M1 and M2, and the other sides of main body 531 do not have a mirror function. In other words, rotating mirror body 53 performs one scan per rotation using reflecting surfaces M1 and M2.

[0025] (Center of gravity and axis of rotation) The rotation axis 530 is configured to coincide with the center of gravity (also referred to as the center of mass or center of gravity) of the rotating mirror body 53. In other words, the rotation axis 530 passes through the center of gravity of the rotating mirror body 53. This configuration can be achieved by arranging the weight 532 so that the rotation axis 530 of the rotating mirror body 53 passes through the center of gravity, as shown in Figures 1 and 2. In the case of the asymmetric rotating mirror body 53 shown in Figures 1 and 2, the center of gravity position can be calculated by determining the mass and center of gravity position of each component part and combining them using a weighted average of the masses. For example, the center of gravity and mass of the upper and lower rectangular prisms of the main body 531 and the cubic weight 532 can be calculated by combining these components using a weighted average of the masses.

[0026] (Light flux on reflective surface) FIG. 2 shows only the light-projecting optical system 501, and does not show the light-receiving optical system 502. The light beam projected from the light source of the light-projecting optical system 501 hits the irradiation areas a11 and a12 on the reflecting surfaces M1 and M2, respectively. FIG. 3 is a diagram corresponding to FIG. 2. In contrast to FIG. 2, FIG. 3 shows only the light-receiving optical system 502, and does not show the light-projecting optical system 501. The light beam received by the light-receiving optical system 502 hits the irradiation areas a22 and a21 on the reflecting surfaces M2 and M1, respectively. In other words, it can be said that the light-receiving optical system 502 receives (uses for distance measurement) only the light beam that hits the irradiation areas a22 and a21.

[0027] (Receiving optical system 502) The second optical element 54 collects the light reflected from the object and reflected by the rotating mirror body 53. The light receiving element array 55 receives the light collected by the second optical element 54 and has a plurality of pixels arranged in the Z direction. The light receiving element array 55 is arrayed at least in the sub-scanning direction. The light receiving element array 55 is a vertically elongated array (the length in the sub-scanning direction is longer than the length in the main scanning direction). For example, the light receiving element array 55 is a light receiving element array in which a plurality of light receiving elements are arranged in one or more rows in the sub-scanning direction. The number of light receiving elements arranged in the sub-scanning direction is 10 or more. More preferably, it is 20 or more. Even more preferably, it is 100 or more. For example, the light receiving element array 55 is composed of 200 pixels vertically and 70 pixels horizontally.

[0028] A normal CMOS (Complementary Metal-Oxide-Semiconductor) may be used as the light-receiving element. Alternatively, a single-photon avalanche diode (SPAD), which has higher sensitivity, may be used as the light-receiving element. For example, a SPAD-type light-receiving element with 600 x 200 pixels can be used with binning to create a 200 x 70 pixel array. With binning, the sensor resolution is sacrificed, but the signal amounts of adjacent pixels (e.g., 3 x 3 pixels) are added together and used as a single pixel value to increase the dynamic range.

[0029] The aspect ratio of the light receiving elements in the array of light receiving element array 55 can be set appropriately to correspond to the aspect ratio of the projected light beam. By matching the aspect ratio of the projected light beam from the light source with the aspect ratio of light receiving element array 55, the area irradiated by light projecting optical system 501 and the area sensed by the sensor in light receiving optical system 502 can be matched, making it possible to effectively use both resources. For example, if the two areas do not match, part of the irradiation beam will be wasted, or some light receiving elements will be unused.

[0030] The box-shaped housing 57 is fixed to a support member 90. The housing 57 has an upper wall 57a, an opposing lower wall 57b, and a side wall 57c connecting the upper wall 57a and the lower wall 57b. An opening 57d is formed in a portion of the side wall 57c, and a transparent plate 58 is attached to the opening 57d. The support member 90 is a pillar or wall when the RIDER 10 is fixed to a road surface, parking lot, square, park, or other location. When the RIDER 10 is fixed to a moving object such as a vehicle, the support member 90 is part of the moving object.

[0031] The motor 56 rotates the rotating mirror body 53. The rotating mirror body 53 is provided with an encoder 71 that detects the rotation angle of the rotating mirror body 53.

[0032] FIG. 4 is a block diagram showing the configuration of the control unit 12 of the rider 10 and the like.

[0033] The control unit 12 obtains distance information (distance values) based on the time difference between when the semiconductor laser 51 emits light and when the light is received by the light-receiving element array 55. From the obtained distance information, a distance image consisting of multiple pixels that indicates the distribution of distance values ​​to objects in the measurement space is generated. The distance image is also referred to as ranging point cloud data or a distance map. As will be described later, the control unit 12 also controls the rotation of the motor 56 that constitutes the scanning optical system 11 and the emission timing of the semiconductor laser 51.

[0034] The control unit 12 is a computer. The control unit 12 includes a CPU 121, which is a calculation device; a RAM 122, which is used as a work area and storage unit; and a ROM 123, which stores basic programs for booting the computer and the like. The control unit 12 also includes an HDD 124, which stores programs for controlling light emission timing and parameter data, and a clock oscillator 125, which generates pulse signals at regular intervals. These components are connected to each other via a bus or the like. This configuration of the control unit 12 is similar to that of a well-known computer, so a detailed description will be omitted. However, various controls are performed by the CPU 121 executing a program for performing the control method described below. The control unit 12 as a computer may be configured using circuits such as an FPGA or ASIC.

[0035] The control unit 12 is connected to each unit in the scanning optical system 11 directly or via an interface for connecting to an external device.

[0036] The control unit 12 controls the motor 56 to maintain a constant rotation speed. The control of the motor 56 itself may be performed by a known method, for example, by using a servo motor as the motor 56 and performing feedback control or feedforward control.

[0037] The control unit 12 obtains distance information (distance values) based on the time difference between when the semiconductor laser 51 emits light and when the light is received by the light-receiving element array 55. From the obtained distance information, a distance image consisting of multiple pixels that indicates the distribution of distance values ​​to objects in the measurement space is generated. The distance image is also called ranging point cloud data or a distance map. The control unit 12 also controls the rotation of the motor 56 that constitutes the scanning optical system 11 and the emission timing of the semiconductor laser 51 based on the signal from the encoder 71.

[0038] In FIG. 1 , a portion of the projected laser beam reflected by an object passes through the transparent plate 58 again and strikes the second reflecting surface M2 of the rotating mirror body 53 in the housing 57. The reflected laser beam is then reflected by the second reflecting surface M2 and the first reflecting surface M1, and is collected by the second optical element 54. Each reflected laser beam is detected pixel by pixel on the light-receiving surface of the light-receiving element array 55. The control unit 12 calculates distance information based on the time difference between the emission timing of the semiconductor laser 51 and the reception timing of the light-receiving element array 55. This allows detection of objects throughout the entire measurement space, resulting in a distance image frame containing distance information for each pixel. The distance image can be transmitted to a remote monitor via a network (not shown) or stored in the HDD 124. The resulting distance image can also be stored as background image data for object detection using background subtraction.

[0039] The configurations of the non-coaxial type and the coaxial type will be described below with reference to FIGS. 5 and 6. FIG. 5 is a schematic diagram showing the configuration of the scanning optical system 11. FIG. 5 shows an example of the non-coaxial type. The scanning optical system 11 in the first embodiment shown in FIGS. 1 to 3 above shows an application example of this non-coaxial type. In the non-coaxial type shown in FIG. 5, the optical axis of the light projection does not coincide with the optical axis of the light reception. That is, in the non-coaxial type, the light projection optical path from which the laser light emitted from the light source passes through the reflecting surfaces M1 and M2 of the rotating mirror body 53 and is irradiated into the measurement space is separate from the light reception optical path from which the laser light reflected by an object in the measurement space passes through the reflecting surfaces M1 and M2 and reaches the light receiving element.

[0040] FIG. 6 shows an example of a coaxial type. In the coaxial type shown in FIG. 6, the scanning optical system 11 has an optical path changing mirror 503. The optical path changing mirror 503 is a half mirror. Alternatively, the optical path changing mirror 503 is a reflective mirror with a hole large enough to allow the projecting light beam to pass through but not allow part of the receiving light beam to pass through. The receiving light beam is bent by approximately 90 degrees by the optical path changing mirror 503 and guided to the light receiving element array 55 of the light receiving optical system 502. In the coaxial type shown in FIG. 6, each optical element is arranged so that the optical axis of the projecting light and the optical axis of the receiving light coincide with each other. That is, in the coaxial type shown in FIG. 6, the optical path from the optical path changing mirror 503 to the object in the measurement space in the projecting light path coincides with the optical path from the object in the measurement space to the optical path changing mirror 503 in the receiving light path. Such a coaxial type has the advantage that the influence of errors on the reflective surface is reduced, and the use area of ​​the reflective surface (illumination areas a11, a12, a21, a22) is common, so the area of ​​the reflective surface can be reduced to match the use area, allowing for further miniaturization. In this embodiment, either a non-coaxial type or a coaxial type can be applied. Note that in the following second and third embodiments, examples in which the coaxial type is applied will be described, but the non-coaxial type may also be applied.

[0041] (Structure of the scanning optical system 11 and area of ​​the rotating body in the second embodiment) FIG. 7 is a diagram illustrating the structure and area of ​​the rotating body of the scanning optical system in the second embodiment. FIG. 7(a) is a front view of the rotating mirror body 53, FIG. 7(b) is a side view of the rotating mirror body 53, and FIG. 7(c) is a top view of the rotating mirror body 53. FIG. 7(d) is a schematic diagram showing the area of ​​the rotating body of the rotating mirror body 53 as viewed from above. In FIG. 7(a), the solid circle indicates the irradiation area (a21, a22) of the projected and received light beams on the reflecting surface when facing forward as shown in the figure. In FIG. 7(a), the dashed circle indicates the area used by the light beams when the rotating mirror body rotates (during scanning) (the same applies to FIGS. 9(a) and 10(a)). In the coaxial type, the centers of the projected and received beams are aligned, and the received beam has a larger illumination area. Therefore, in Figure 7(b) and other figures, illumination areas a21 and a22 of the received beam are shown, and illumination areas a11 and a12 are omitted. The dashed line in Figure 7(d) represents the area of ​​the rotating body used by the rotating mirror body 53 when rotated around the rotation axis. The area of ​​the rotating body corresponds to the volume that must be secured around the rotating mirror body 53 in the device. In Figure 7(d), the short dashed line indicates the position of the rotating mirror body 53 when rotated a predetermined angle, and the long dashed circular line indicates its trajectory. This circular dashed line corresponds to the area of ​​the rotating body when the rotating mirror body rotates. The smaller the area of ​​the rotating body, the smaller the size of the scanning optical system 11 can be.

[0042] FIG. 8 is a diagram illustrating the structure and area of ​​a rotating body of a comparative example. The rotating mirror body of the comparative example has a shape formed by joining two square pyramids in reverse orientation, as shown in Patent Document 1 (Japanese Patent No. 5754564), and has a total of eight surfaces, with four pairs of reflecting surfaces. FIGS. 8(a) to 8(d) are similar to FIGS. 7(a) to 7(d), respectively, except for the shape, showing the front view, side view, top view, and area of ​​the rotating body. In FIGS. 7 and 8, the width (bottom width) of the reflecting surface is shown as the same length. Comparing FIGS. 7(d) and 8(d) reveals that the second embodiment shown in FIG. 7 has a smaller area of ​​the rotating body than the comparative example shown in FIG. 8, enabling further miniaturization. Furthermore, by using an arrayed photodetector array 55, high image quality can be maintained while avoiding the degradation in resolution caused by a single scan per rotation due to the rotating mirror body 53 having only one pair of reflecting surfaces.

[0043] (Structure of the scanning optical system 11 and area of ​​the rotating body in the third embodiment) Figure 9 is a diagram illustrating the structure of the scanning optical system and the area of ​​the rotor in the third embodiment. Figures 9(a) to 9(d) show a front view, a side view, a top view, and the area of ​​the rotor, respectively, similar to Figures 7(a) to 7(d), except for the shape.

[0044] In the third embodiment, when viewed from the rotation axis direction (as viewed from above), the rotation axis 530 of the rotating mirror body 53 is disposed inside the reflecting surfaces M1 and M2. In particular, in the third embodiment, the rotation axis 530 is disposed inside the irradiation areas a21 and a22 of the reflecting surfaces M1 and M2, on which the projecting light beam and the receiving light beam strike. In the third embodiment, by disposing the rotation axis 530 in this manner, the area of ​​the rotating body can be made smaller, as shown in FIG. 9(d), thereby achieving further miniaturization. In the third embodiment, the rotation axis 530 is disposed so that the imaginary vertical line of the rotation axis 530 passes through the approximate center of the irradiation areas a21 and a22. By adopting a positional relationship in which the imaginary vertical line passes through the center, the lower part of the main body 531 (the lower part of the rotating mirror body 53) can be made the most compact. Also, the rotation axis 530 is optimized (not shown) by cutting away the parts of the main body 531 other than the reflecting surfaces M1 and M2 so that it becomes the center of gravity of the main body 531. Therefore, there is no weight 532 as in the first embodiment. A central support part is provided at the bottom of the main body 531, and a motor shaft 56a (see FIG. 1) is connected to this central support part to transmit driving force to the rotating mirror body 53.

[0045] FIG. 10 is a diagram illustrating the structure of the scanning optical system and the area of ​​the rotating body in a modified example of the third embodiment. In this modified example, the rotating shaft 530 is disposed within the irradiation areas a21 and a22 of the reflecting surfaces M1 and M2 where the projecting and receiving light beams strike. Similar to FIGS. 7(a) to 7(d), FIGS. 10(a) to 10(f) show a front view, a side view, a top view, and an area of ​​the rotating body, respectively, except for the shape. Furthermore, in this modified example of the third embodiment, the upper and lower portions of the rotating mirror body 53 have different sizes, with the lower portion being smaller. As shown in FIG. 10(a), the rotation axis 530 is positioned within the illumination areas a21 and a22 of the reflecting surfaces M1 and M2 where the projected and received beams strike. More preferably, the rotation axis 530 and the optical axis of the received beam coincide on the reflecting surface M1, creating a situation where the beam strikes the same position on the lower reflecting surface M1 regardless of rotation. In FIG. 10(a), the beam spreads during rotation (scanning) of the rotating mirror body on the upper reflecting surface M2, as indicated by the dashed circle, but does not spread on the lower reflecting surface M1 (no dashed circle). Therefore, as shown in FIGS. 10(a) and 10(c), the size of the lower portion 3c of the main body 531 can be reduced to match the illumination area a21. This allows the area of ​​the rotating body to be reduced during rotation of the lower portion 3c, as shown in FIG. 10(f).

[0046] As described above, the scanning optical system according to this embodiment includes a light projecting and receiving system including a light projecting optical system that projects a light projecting beam from a light source and a light receiving optical system that guides the reflected light projected onto the light receiving elements of the light receiving element array, and a rotating mirror body that rotates around a rotation axis, scans the light projecting and receiving beams, and has only a pair of reflecting surfaces aligned in the direction of the rotation axis, the rotation axis coinciding with the center of gravity of the rotating mirror body, and the light receiving element array has a plurality of light receiving elements arrayed in the sub-scanning direction. With this configuration, the rotating mirror body having only a pair of reflecting surfaces can be made compact, and the light receiving element array is made up of an array of light receiving elements, thereby achieving high image quality.

[0047] In this embodiment, the light beam projected from the light source is elongated in the sub-scanning direction. If the beam (light beam projected) were circular, some of the beam would be wasted outside the scanning direction and would not be usable, but by elongating the beam in the sub-scanning direction, it is possible to more efficiently extend the distance without increasing the beam output.

[0048] In this embodiment, the light receiving element array is a vertically long array in the sub-scanning direction. By using a vertically long array, it is possible to minimize unused light receiving elements, thereby making effective use of light receiving element resources and achieving high image quality.

[0049] Furthermore, in this embodiment, a coaxial type can be adopted in which the optical axes of the light projecting optical system and the light receiving optical system are arranged coaxially. This allows the irradiation areas to be aligned in the sub-scanning direction without being arranged side by side, thereby reducing the size of the mirror reflecting surface in the direction of the rotation axis, and therefore the size of the scanning optical system in the direction of the rotation axis.

[0050] In the second embodiment, the rotation axis of the rotating mirror is located within the reflecting surface when viewed from the rotation axis direction, which reduces the area of ​​the rotating mirror, thereby enabling the scanning optical system to be further miniaturized.

[0051] Furthermore, as in the modified example of the second embodiment, when viewed from the direction of the rotation axis, the rotation axis of the rotating mirror body is positioned within the range of the reflecting surface that is hit by the projecting light beam and the receiving light beam. This allows for further miniaturization. At least the lower part of the rotating mirror body, which has the reflecting surface M1, can be made smaller to the range that the light beam hits, allowing for further miniaturization.

[0052] The means and methods for performing various processes in the scanning optical system or laser radar according to the above-described embodiments can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a USB memory or a DVD (Digital Versatile Disc)-ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is typically transferred and stored in a storage unit such as a hard disk. The program may also be provided as standalone application software, or may be incorporated into the software of the laser radar device as a function of the device.

[0053] While embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and are not intended to be limiting, and the scope of the present invention should be construed by the language of the appended claims. [Explanation of symbols]

[0054] 10 Rider 11 Scanning optical system 12 Control Unit 50 Light emitter / receiver system 501 Projection optical system 51 Semiconductor laser 52 First optical element 53 Rotating mirror body 530 Rotational Axis 531 Main body 532 Weight 502 Light receiving optical system 54 Second optical element 55 Photodetector array 503 Optical path changing mirror 56 Motor 56a Motor shaft 57 Case

Claims

1. a light projecting and receiving system including a light source, a light projecting optical system for projecting a light beam from the light source, and a light receiving optical system for guiding a reflected light beam to a light receiving element of the light receiving element array; a rotating mirror body that rotates around a rotation axis, scans the projected light beam and the received light beam, and has only a pair of reflecting surfaces aligned in the direction of the rotation axis; the rotation axis coincides with the center of gravity of the rotating mirror body, The light receiving element array is a scanning optical system in which a plurality of light receiving elements are arrayed in the sub-scanning direction.

2. The scanning optical system according to claim 1 , wherein the light beam projected from the light source is elongated vertically in the sub-scanning direction.

3. 2. The scanning optical system according to claim 1, wherein the light receiving element array is an array that is elongated vertically in the sub-scanning direction.

4. 2. The scanning optical system according to claim 1, wherein the optical axes of the light projecting optical system and the light receiving optical system are arranged coaxially.

5. The scanning optical system according to claim 1 , wherein the rotation axis of the rotating mirror body is located within the reflecting surface when viewed from the rotation axis direction.

6. The scanning optical system according to claim 5 , wherein the rotation axis of the rotating mirror body is located within a range of the reflecting surface that is struck by the projecting light beam and the receiving light beam, as viewed from the direction of the rotation axis.

7. a scanning optical system according to any one of claims 1 to 6; A laser radar that measures the distance to an object based on the timing of light emission from the light source and the timing of light reception by the light receiving element.

Images