Light beam scanning device and distance measuring device

Abstract

An optical beam scanning device (1) comprises a plurality of light sources (11, 21), a plurality of beam shapers (13, 23), a scanning mirror (40), and a scanning region correcting optical member (45). The plurality of light sources emit a plurality of optical beams (12, 22). Each of the plurality of beam shapers includes a first lens (14, 24) and a second lens (15, 25). A distance (D1) between the first lens (14) and the second lens (15) in the beam shaper (13) for shaping the optical beam (12) is different from a distance (D2) between the first lens (24) and the second lens (25) in the beam shaper (23) for shaping the optical beam (22).

Description

[Technical Field]

[0001] The present disclosure relates to a light beam scanning device and a distance measuring device. [Background technology]

[0002] International Publication No. 2018 / 021108 (Patent Document 1) discloses a scanning illumination device including a light-emitting device and a projection optical system. The light-emitting device includes a laser diode, a light deflection unit, a wavelength conversion unit, and a condenser unit. The condenser unit includes a first optical system and a second optical system. The first optical system includes an aspherical lens and a cylindrical lens. The cylindrical lens of the first optical system has a curvature with respect to the fast axis of the laser beam emitted from the laser diode. The second optical system includes a cylindrical lens. The cylindrical lens of the second optical system has a curvature with respect to the slow axis of the laser beam. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 021108 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of a first aspect of the present disclosure is to provide an optical beam scanning device having a plurality of scanning areas, which can reduce distortion of the scanning areas and emit an optical beam of improved quality.An object of a second aspect of the present disclosure is to provide a distance measuring device having improved measurement accuracy. [Means for solving the problem]

[0005] The light beam scanning device disclosed herein includes a plurality of light sources, a plurality of beam shapers, a scanning mirror, and a scanning area correction optical member. The plurality of light sources emit a plurality of light beams. Each of the plurality of light beams is emitted from a corresponding one of the plurality of light sources and has a larger beam diameter in the fast axis direction than in the slow axis direction. Each of the plurality of beam shapers is provided for a corresponding one of the plurality of light sources and shapes the light beam emitted from the corresponding light source. The scanning mirror scans the plurality of light beams shaped by the plurality of beam shapers. The scanning area correction optical member corrects at least one of a plurality of scanning areas formed by the plurality of light beams scanned by the scanning mirror. Each of the plurality of beam shapers includes a first lens and a second lens. The first lens is disposed closer to the corresponding one of the plurality of light sources than the second lens. Each of the plurality of beam shapers imparts positive refractive power to a corresponding one of the plurality of light beams in the slow axis direction and the fast axis direction. Each of the plurality of beam shapers has a focal length Ff in the fast axis direction and a focal length F in the slow axis direction. f The scanning mirror has a larger focal length Fs. In at least one direction, an incident angle θ1 of a first light beam that is one of the plurality of light beams on the scanning mirror when the scanning mirror is at the center of its rotation range is different from an incident angle θ2 of a second light beam that is one of the plurality of light beams on the scanning mirror when the scanning mirror is at the center of its rotation range. A distance D1 between a first lens and a second lens in a first beam shaper that is one of the plurality of beam shapers and shapes the first light beam is different from a distance D2 between a first lens and a second lens in a second beam shaper that is one of the plurality of beam shapers and shapes the second light beam.

[0006] The distance measuring device of the present disclosure includes the light beam scanning device of the present disclosure. [Effects of the Invention]

[0007] The light beam scanning device of the present disclosure includes a scanning area correction optical element. Therefore, the light beam scanning device of the present disclosure can correct distortion of the scanning area due to differences in the angle of incidence of the light beam on the scanning mirror. The light beam scanning device of the present disclosure also includes a beam shaper, which includes a first lens and a second lens. The distances between the first lens and the second lens are different between the two beam shapers that shape two light beams having different angles of incidence on the scanning mirror. Therefore, the quality of the light beam emitted from the scanning area correction optical element is improved, for example, by improving the parallelism of the light beam emitted from the scanning area correction optical element. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic perspective view of a light beam scanning device according to a first embodiment. [Figure 2] 1 is a schematic side view of a light beam scanning device according to a first embodiment. [Figure 3] 1 is a schematic top view of a light beam scanning device according to a first embodiment. [Figure 4] 2 is a schematic perspective view of a light source included in the light beam scanning device according to the first embodiment. FIG. [Figure 5] FIG. 2 is a schematic perspective view of a beam shaper included in the light beam scanning device according to the first embodiment. [Figure 6] 2 is a schematic plan view of a beam shaper included in the light beam scanning device of the first embodiment, taken along the fast axis. FIG. [Figure 7] 2 is a schematic plan view of a beam shaper included in the light beam scanning device of the first embodiment, taken along the slow axis. FIG. [Figure 8] 3 is a schematic diagram showing the relationship between the incident angle of a light beam on a reflecting surface of a scanning mirror and the scanning locus of the light beam reflected by the reflecting surface. FIG. [Figure 9] FIG. 1 is a schematic perspective view of a light beam scanning device of a first comparative example. [Figure 10] FIG. 2 is a schematic side view of a light beam scanning device of a first comparative example. [Figure 11] FIG. 2 is a schematic top view of a light beam scanning device of a first comparative example. [Figure 12] 1 is a diagram showing a plurality of scanning areas generated by a light beam scanning device of a first comparative example. FIG. [Figure 13] FIG. 10 is a schematic perspective view of a light beam scanning device of a second comparative example. [Figure 14] FIG. 10 is a schematic front view of a light beam scanning device of a second comparative example. [Figure 15] FIG. 10 is a schematic plan view of a light beam scanning device of a second comparative example. [Figure 16] 3 is a diagram showing a plurality of scanning areas generated by the light beam scanning device according to the first embodiment. FIG. [Figure 17] FIG. 1 is a diagram showing the relationship between the width of an emitter (light emitting point), the focal length of a lens optical system, and the divergence angle of a light beam that has passed through the lens optical system. [Figure 18] FIG. 4 is a schematic perspective view showing another example of the light beam scanning device according to the first embodiment. [Figure 19] FIG. 4 is a schematic front view showing another example of the light beam scanning device according to the first embodiment. [Figure 20] FIG. 4 is a schematic plan view showing another example of the light beam scanning device according to the first embodiment. [Figure 21] FIG. 11 is a schematic perspective view of a light beam scanning device of a third comparative example. [Figure 22] FIG. 11 is a schematic plan view of a light beam scanning device of a third comparative example. [Figure 23] FIG. 10 is a schematic diagram of a distance measuring device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described. Note that the same reference numerals are used to designate the same components, and the description thereof will not be repeated.

[0010] Embodiment 1 The light beam scanning device 1 of the first embodiment will be described with reference to Figs. 1 to 8. Figs. 1 to 3 are diagrams schematically showing an example of the configuration of the light beam scanning device 1 in the first embodiment. Fig. 1 is a schematic perspective view of the light beam scanning device 1, Fig. 2 is a schematic side view of the light beam scanning device 1, and Fig. 3 is a schematic top view of the light beam scanning device 1. The light beam scanning device 1 mainly includes a plurality of light sources (e.g., light sources 11, 21, and 31), a plurality of beam shapers (e.g., beam shapers 13, 23, and 33), a scanning mirror 40, and a scanning area correction optical member 45. The light beam scanning device 1 may further include reflecting mirrors 17, 27, and 37.

[0011] In this embodiment, each of the multiple beam shapers is provided for a corresponding one of the multiple light sources. Hereinafter, a set of a light source and a beam shaper may be referred to as a light source module. For example, the light beam scanning device 1 includes three light source modules (light source modules 10, 20, and 30). The light source module 10 includes a light source 11 and a beam shaper 13. The light source module 20 includes a light source 21 and a beam shaper 23. The light source module 30 includes a light source 31 and a beam shaper 33. The beam shaper 13 corresponds to the light source 11. The beam shaper 23 corresponds to the light source 21. The beam shaper 33 corresponds to the light source 31. Although the light beam scanning device 1 includes three light sources, the light beam scanning device 1 may include two light sources or four or more light sources. The light beam scanning device 1 may include beam shapers in a number corresponding to the number of light sources.

[0012] <Light source 11,21,31> As shown in FIG. 1, multiple light sources (e.g., light sources 11, 21, and 31) emit multiple light beams (e.g., light beams 12, 22, and 32). Each of the multiple light beams is emitted from a corresponding one of the multiple light sources. Specifically, light source 11 emits light beam 12. light source 21 emits light beam 22. light source 31 emits light beam 32. As shown in FIGS. 4, 6, and 7, each of the multiple light beams has a larger beam diameter in the fast axis direction than in the slow axis direction. Below, the structure and function of the multiple light sources will be described using light source 11 as an example. Unless otherwise specified, other light sources (e.g., light sources 21 and 31) are similar to light source 11.

[0013] The light source 11 is, for example, a laser diode, and the light beam 12 is, for example, a laser beam. FIG. 4 is a schematic perspective view of a laser diode, which is an example of the light sources 11, 21, and 31. The laser diode includes a substrate 51, a cladding layer 52, an active layer 53, a cladding layer 54, an electrode 56, an electrode 57, and an insulating layer 59. The cladding layer 52 is formed on the substrate 51. The active layer 53 is formed on the cladding layer 52. The cladding layer 54 is formed on the active layer 53. The active layer 53 is sandwiched between the cladding layer 52 and the cladding layer 54. The electrodes 56 and 57 are used to apply a forward voltage to the cladding layer 52 and the cladding layer 54. The electrode 56 is formed on the substrate 51. The electrode 56 may be formed on the cladding layer 52 instead of the substrate 51. The electrode 57 is formed on the cladding layer 54. The cladding layer 54 has a ridge portion 55 (also called a contact layer) formed therein to limit the area through which current flows and to cause laser oscillation only in that area, and an electrode 57 is formed on the ridge portion 55.

[0014] When a voltage is applied between the electrodes 56 and 57, a light beam is emitted from the active layer 53. As shown in Fig. 4, the width W1 (length in the width direction of the active layer 53) of the emitter 60, which is the light emitting point of the light beam from the active layer 53, is larger than the width W2 (length in the thickness direction of the active layer 53) of the emitter 60. In a cross section perpendicular to the optical axis of the emitted light beam (a direction parallel to the z axis in the figure), the thickness direction of the active layer 53 corresponds to the fast axis (f axis in Figs. 5 to 7, etc.) of the light beam 12, and the width direction of the active layer 53 corresponds to the slow axis (s axis in Figs. 5 to 7, etc.) of the light beam 12.

[0015] 4, when the width W1 of the emitter (light-emitting point) 60 in the slow axis direction is greater than the width W2 of the emitter 60 in the fast axis direction, the beam diameter of the emitted light beam is larger in the fast axis direction than in the slow axis direction, and the quality of the light beam in the fast axis direction is higher than the quality of the light beam in the slow axis direction. Note that when the light source 11 is a multi-emitter laser diode including multiple emitters, the emitter width W1 is the total width of the multiple emitters.

[0016] The light source 11 may be, for example, a laser diode that emits a light beam 12 having a high output of 0.5 W or more. The light source 11 may be, for example, a multimode laser diode. A multimode laser diode can emit a light beam 12 having a higher output than a single-mode laser diode. Here, the light source 11 may be a laser diode whose oscillation mode of the slow axis is multimode and whose oscillation mode of the fast axis is single mode.

[0017] <Beam shapers 13, 23, 33> 5 to 7 are explanatory diagrams showing examples of multiple beam shapers (beam shapers 13, 23, and 33). FIG. 5 is a schematic perspective view of the beam shaper, FIG. 6 is a schematic plan view of the beam shaper on the fast axis, and FIG. 7 is a schematic plan view of the beam shaper on the slow axis. Each of the multiple beam shapers shapes a light beam emitted from a corresponding light source. Shaping the light beam includes changing the divergence angle of the light beam and the resulting beam width of the light beam. Each of the multiple beam shapers in the light beam scanning device 1 is used primarily for the purpose of improving the parallelism of the light beam incident on the scan area correction optical element 45. For example, each of the multiple beam shapers is used for the purpose of collimating the light beam incident on the scan area correction optical element 45. Here, each beam shaper does not need to strictly collimate the incident light beam. This is because it is important that each of the multiple light beams emitted from the scan area correction optical element 45 becomes approximately parallel light. Therefore, in this embodiment, each of the multiple beam shapers is equipped with multiple lenses, and is configured so that the beam shaping effect of each of the multiple beam shapers can be easily adjusted by adjusting the distance between the multiple lenses.

[0018] As shown in FIGS. 5 to 7 , each of the multiple beam shapers includes a front lens and a rear lens. The front lens may be referred to as the first lens of the beam shaper, and the rear lens may be referred to as the second lens of the beam shaper. As shown in FIG. 1 , the beam shaper 13 shapes the light beam 12. The beam shaper 13 includes a front lens 14 and a rear lens 15. In the beam shaper 13, the front lens 14 and the rear lens 15 are spaced apart by a distance D1. The beam shaper 23 shapes the light beam 22 emitted from the light source 21. The beam shaper 23 includes a front lens 24 and a rear lens 25. In the beam shaper 23, the front lens 24 and the rear lens 25 are spaced apart by a distance D2. The beam shaper 33 shapes the light beam 32 emitted from the light source 31. The beam shaper 33 includes a front lens 34 and a rear lens 35. In the beam shaper 33, the front lens 34 and the rear lens 35 are spaced apart by a distance D3. The structure and function of the beam shaper will be described below using the beam shaper 13 as an example. Unless otherwise specified, other beam shapers (e.g., beam shapers 23 and 33) are similar to the beam shaper 13.

[0019] The front lens 14 of the beam shaper 13 is disposed on the optical path of the light beam 12 closer to the light source 11 than the rear lens 15. In other words, the front lens 14 is disposed between the light source 11 and the rear lens 15. Here, the front lens 14 and the rear lens 15 do not each need to be a single lens. In other words, the beam shaper 13 may include a plurality of lenses (first optical system) as the front lens 14, and a plurality of lenses (second optical system) as the rear lens.

[0020] In this embodiment, the beam shaper 13 imparts positive refractive power to the light beam 12 in both the slow axis direction and the fast axis direction of the light beam 12 incident on the beam shaper 13. The focal length of the beam shaper 13 in the slow axis direction (more specifically, the composite focal length of the combination of the front lens 14 and the rear lens 15) is greater than the focal length of the beam shaper 13 in the fast axis direction. In other words, the refractive power of the beam shaper 13 in the fast axis direction of the light beam 12 is greater than the refractive power of the beam shaper 13 in the slow axis direction of the light beam 12. The beam shaper 13 may collimate the light beam 12 in the fast axis direction of the light beam 12.

[0021] Here, the focal length of a composite lens formed by combining two or more lenses, such as the composite focal length of the beam shaper 13, refers to the distance from the center of the lens group to the focal point where light emitted from a point is converted into parallel light by the composite lens (the group of lenses constituting the composite lens), or where parallel light is focused at a single point by the composite lens (the group of lenses constituting the composite lens). In other words, the "focal length" in this disclosure does not refer to the distance to which a light beam actually focuses (focal length in a broad sense), but rather refers to an inherent value determined by the specifications of the lenses (the group of lenses constituting the composite lens, in the case of a composite lens). The same applies to the focal length of a single lens. In other words, the focal length refers to the distance from the center of the single lens to the focal point where light emitted from a point is converted into parallel light by the single lens, or where parallel light is focused at a single point by the single lens.

[0022] The front lens of each beam shaper has positive refractive power in the fast axis direction of the light beam. The rear lens of each beam shaper has positive refractive power in the slow axis direction of the light beam. For example, the front lens may have a lens surface with positive curvature in the fast axis direction of the light beam (e.g., the convex surface on the incident side of the front lenses 14, 24, and 34 in FIG. 6). Also, for example, the rear lens may have a lens surface with positive curvature in the slow axis direction of the light beam (e.g., the convex surface on the exit side of the rear lenses 15, 25, and 35 in FIG. 7). In this case, the light beam is shaped mainly by the front lens in the fast axis direction and mainly by the rear lens in the slow axis direction.

[0023] The focal length F2s of the rear lens in the slow axis direction (the distance from the center of the rear lens to the focal point of the rear lens) may be greater than the focal length F1f of the front lens in the fast axis direction (the distance from the center of the front lens to the focal point of the front lens). In other words, the refractive power of the front lens in the fast axis direction may be greater than the refractive power of the rear lens in the slow axis direction. It is more preferable that the rear lens have zero refractive power in the fast axis direction. For example, the incident surface of the rear lens may be a plane perpendicular to the optical axis of the light beam.

[0024] In this way, a lens (e.g., a front lens) that mainly shapes the light beam in the fast axis direction (mainly by changing the divergence angle of the light beam to make the light beam approximately parallel) is different from a lens (e.g., a rear lens) that mainly shapes the light beam in the slow axis direction. Therefore, it is possible to significantly reduce the influence of the inter-lens distance within the beam shaper (specifically, the distance between the front lens and the rear lens) on the light beam shaping function of the beam shaper. As shown in Figures 5 to 7, in each of the multiple beam shapers, the divergence angle of the light beam incident on the front lens in the slow axis direction is smaller than the divergence angle of the light beam incident on the front lens in the fast axis direction, and the divergence angle of the light beam incident on the rear lens in the slow axis direction is larger than the divergence angle of the light beam incident on the rear lens in the fast axis direction.

[0025] In a beam shaper, when the distance between the front and rear lenses is changed without changing the distance between the light source and the front lens, the light beam is affected by the change in the distance between the front and rear lenses in the slow axis direction but is not affected by the change in the distance between the front and rear lenses in the fast axis direction. Therefore, if the front lens collimates the light beam to a small beam diameter in the fast axis direction, where the quality of the light beam is relatively good, then simply changing the distance between the front and rear lenses can adjust the divergence angle of the light beam in the slow axis direction of the light beam emitted from the beam shaper while maintaining the shaped state of the light beam in the fast axis direction. This function of the beam shaper is particularly effective in cases where the refractive power imparted to the light beam in the slow axis direction by the scan area correction optical element 45 varies depending on the position of incidence of the light beam on the scan area correction optical element 45. In other words, according to the above configuration, by changing the distance between the front lens and the rear lens between the beam shapers (the above-mentioned distances D1, D2, and D3), the parallelism of the light beam emitted from the scanning area correction optical member 45 can be improved.

[0026] In this embodiment, based on the above-described action of the beam shaper and the action of the scan area correction optical member 45, which will be described later, the distances between the front and rear lenses are made different between multiple beam shapers that emit multiple light beams that have different angles of incidence on the scan mirror 40 (and therefore different positions of incidence on the scan area correction optical member 45). Here, the angle of incidence of the light beam on the scan mirror 40 is the magnitude of the angle between the normal to the reflective surface of the scan mirror 40 and the optical axis of the light beam that is incident on the scan mirror 40 when the scan mirror 40 is at the center of the rotation range of the scan mirror 40 (hereinafter also referred to as the "rotation center"). Hereinafter, the normal to the reflective surface of the scan mirror 40 when the scan mirror 40 is at the rotation center may be referred to as the "first normal" of the scan mirror 40.

[0027] At least in the x-axis direction (see FIGS. 1 to 3 ), the angle of incidence of light beam 22 on scan mirror 40 is different from the angle of incidence of light beam 12 on scan mirror 40. At least in the x-axis direction, the angle of incidence of light beam 32 on scan mirror 40 is different from the angle of incidence of light beam 12 on scan mirror 40. More specifically, the angle of incidence of light beam 22 is larger than the angle of incidence of light beam 12. The angle of incidence of light beam 32 is larger than the angle of incidence of light beam 12. Note that in this embodiment, light source module 20 and reflecting mirror 27 are arranged with respect to light source module 30 and reflecting mirror 37 so that the optical paths of light beam 22 and light beam 32 are plane-symmetric with respect to a vertical plane (yz plane) containing the optical path of light beam 12. Therefore, the angle of incidence of light beam 22 on scan mirror 40 is the same as the angle of incidence of light beam 32 on scan mirror 40. In such a case, the distance D2 between the front lens 24 and the rear lens 25 in the beam shaper 23 that shapes the light beam 22 is different from the distance D1 between the front lens 14 and the rear lens 15 in the beam shaper 13 that shapes the light beam 12. The distance D3 between the front lens 34 and the rear lens 35 in the beam shaper 33 that shapes the light beam 32 is different from the distance D1. The distance D3 is the same as the distance D2.

[0028] Here, the x-axis direction may be a direction parallel to the slow axis direction of each light beam, a horizontal direction (here, including not only a direction perpendicular to the vertical direction but also a horizontal direction determined in a host device (such as an automobile) on which the light beam scanning device 1 is mounted), an arbitrary direction on a plane perpendicular to one of the rotation axes of the scanning mirror 40 (for example, a direction perpendicular to the rotation axis of the scanning mirror 40, or a direction in which the difference in incident angle to the scanning mirror 40 between multiple light beams is greatest), or a direction in which the scanning area of the light beam scanning device 1 is expanded (for example, the longitudinal direction of the entire scanning area of the light beam scanning device 1). Note that the slow axis direction and the x-axis direction of each light beam do not necessarily need to coincide. That is, in this embodiment, the slow axis of each light beam is arranged in the horizontal direction and the fast axis of each light beam is arranged in the vertical direction (i.e., a direction perpendicular to the horizontal direction), but the present invention is not limited to this.

[0029] In this embodiment, the angles of incidence of the light beams on the scanning mirror 40 are the same in the vertical direction (y direction) and different in the horizontal direction (e.g., x direction). Therefore, the angles of incidence of the light beams on the scanning mirror 40 are understood two-dimensionally. In contrast, when the angles of incidence of the light beams on the scanning mirror 40 are different in both the horizontal and vertical directions, the angles of incidence of the light beams on the scanning mirror 40 are understood three-dimensionally.

[0030] As shown in FIG. 7, in this embodiment, the front lens has negative refractive power in the slow axis direction. For example, the exit surface of the front lenses 14, 24, and 34 is a concave surface with a negative curvature along the slow axis direction. The front lens increases the divergence angle of the light beam in the slow axis direction. This effectively lengthens the focal length (composite focal length) Fs of the beam shaper in the slow axis direction even when the distance between the front lens and the rear lens is short. Note that the shape of the front lens is not limited to this, and may be, for example, a shape with no curvature or a shape with positive curvature in the slow axis direction.

[0031] An example of adjusting the distance between the front lens and the rear lens among a plurality of beam shapers will be shown below. The light beam 12 shaped by the beam shaper 13 is reflected by the reflecting mirror 17 and enters the scanning mirror 40. The light beam 22 shaped by the beam shaper 23 is reflected by the reflecting mirror 27 and enters the scanning mirror 40. The light beam 32 shaped by the beam shaper 33 is reflected by the reflecting mirror 37 and enters the scanning mirror 40. That is, the reflecting mirrors (reflecting mirrors 17, 27, 37) are arranged so that the light beams 12, 22, 32 enter one scanning mirror 40. In this embodiment, the reflecting mirrors 27 and 37 are arranged symmetrically with respect to a vertical plane including the optical path of the light beam 12.

[0032] The scanning mirror 40 rotates around its rotation axis, reflecting the light beams 12, 22, and 32 shaped by the beam shapers 13, 23, and 33. The light beams 12, 22, and 32 reflected by the scanning mirror 40 travel toward the outside of the light beam scanning device 1. In this way, the scanning mirror 40 reflects the multiple light beams 12, 22, and 32 while rotating, thereby scanning the light beams 12, 22, and 32. The scanning mirror 40 is, for example, a microelectromechanical system (MEMS) mirror in which the tilt angle of the reflecting surface of the scanning mirror 40 can be electrically controlled. The scanning mirror 40 may be, for example, an electromagnetic MEMS mirror in which the tilt angle of the reflecting surface can be controlled by electromagnetic force from a coil, or a piezoelectric MEMS mirror in which the tilt angle of the reflecting surface can be controlled by using a piezoelectric member. By controlling the inclination angle of the reflecting surface of the scanning mirror 40, it is possible to change the emission angle of each of the light beams 12, 22, 32 emitted from the light beam scanning device 1 (the direction in which each of the light beams 12, 22, 32 is emitted, more specifically, the angle between the first normal to the scanning mirror 40 and the optical axis of each of the light beams 12, 22, 32 emitted from the scanning mirror 40).

[0033] The scan mirror 40 can rotate around two rotation axes that are parallel to the reflective surface of the scan mirror 40 and perpendicular to each other. In this embodiment, one rotation axis of the scan mirror 40 is parallel to the x-axis, and the other rotation axis of the scan mirror 40 is parallel to the y-axis. The scan mirror 40 scans each of the light beams 12, 22, and 32 in the x-axis and y-axis directions. The light beam 12 scanned by the scan mirror 40 irradiates a scan area 71 (see FIG. 16). The light beam 22 scanned by the scan mirror 40 irradiates a scan area 72 (see FIG. 16). The light beam 32 scanned by the scan mirror 40 irradiates a scan area 73 (see FIG. 16). By controlling the tilt angle of the reflective surface of the scan mirror 40 around two axes that are orthogonal to each other, the emission angles of the light beams 12, 22, and 32 emitted from the light beam scanning device 1 can be changed two-dimensionally. Therefore, each of the multiple light beams can generate a scanning area that is a two-dimensional area.

[0034] The scanning areas 71, 72, and 73 are arranged in the x-axis direction. The scanning area 71 is located between the scanning area 72 and the scanning area 73. The light beam scanning device 1 can expand the scanning area in the x-axis direction. Each of the multiple scanning areas 71, 72, and 73 is larger than the other of the multiple scanning areas 71, 72, and 73. For example, in the direction in which the scanning areas 71, 72, and 73 are arranged (x-axis direction), the multiple scanning areas 71, 72, and 73 may be arranged such that one end of a pair of adjacent scanning areas overlaps only with the other end of the pair of adjacent scanning areas, or the multiple scanning areas 71, 72, and 73 are in contact with the other end of the pair of adjacent scanning areas. The multiple scanning areas 71, 72, and 73 have multiple centers 71c, 72c, and 73c. Each of the multiple centers 71c, 72c, and 73c is the center of a corresponding scanning area among the multiple scanning areas 71, 72, and 73. The positions of the centers 71c, 72c, and 73c may be different from each other.

[0035] In this embodiment, in the direction in which the scanning regions 71, 72, and 73 are arranged (x-axis direction), the end of the scanning region 72 overlaps only with the end of the scanning region 71 or is in contact with the end of the scanning region 71. In the direction in which the scanning regions 71, 72, and 73 are arranged, the end of the scanning region 73 overlaps only with the end of the scanning region 71 or is in contact with the end of the scanning region 71. The scanning region 71 has a center 71c. The scanning region 72 has a center 72c. The scanning region 73 has a center 73c. The center 72c is offset from the centers 71c and 73c in the direction in which the scanning regions 71, 72, and 73 are arranged. The center 73c is offset from the centers 71c and 72c in the direction in which the scanning regions 71, 72, and 73 are arranged. Note that the scanning regions 71, 72, and 73 do not necessarily have to overlap and may be separated from each other.

[0036] 8 is a diagram showing examples of scanning trajectories for each actual angle of incidence of the light beam on the scanning mirror 40 when the scanning mirror 40 is subjected to two-dimensional scanning (two-axis rotation) so that the light beam incident at an angle of incidence of 0 degrees with respect to the first normal to the scanning mirror 40 (i.e., the same direction as the first normal) has an emission angle of 20 degrees in all directions (i.e., so as to describe a circle at a position 20 degrees from the first normal). Fig. 8 shows four examples of actual angles of incidence of 0 degrees, 20 degrees, 40 degrees, and 60 degrees with respect to the first normal. Note that for any of the angles of incidence, the two-dimensional scanning of the scanning mirror 40 is the circular scanning described above.

[0037] Here, the trajectory shown as 0-degree incidence represents the trajectory traced by the above-mentioned two-dimensional scanning of a light beam whose actual angle of incidence on scanning mirror 40 is 0 degrees relative to the first normal. Also, the trajectory shown as 20-degree incidence represents the trajectory traced by the above-mentioned two-dimensional scanning of a light beam whose actual angle of incidence on scanning mirror 40 is 20 degrees in the -x-axis direction relative to the first normal. Note that, in the cases of 40-degree incidence and 60-degree incidence, similarly, the trajectories represent the trajectories traced by the above-mentioned two-dimensional scanning of a light beam whose actual angle of incidence is 40 degrees or 60 degrees in the -x-axis direction relative to the first normal.

[0038] In the case of 0-degree incidence, the light beam traces a circular scanning trajectory at a position where the emission angle is 20 degrees with respect to the first normal in all directions, as assumed for the two-dimensional scanning described above. Note that in Figure 8, the trajectory traced by each light beam is shown in terms of the emission angle with respect to the first normal in the two orthogonal axial directions of the x-axis and y-axis.

[0039] In contrast, in the case of a 20-degree incidence, there is a difference of 20 degrees in the -x-axis direction between the incidence angle assumed for the above two-dimensional scanning and the actual incidence angle. Therefore, for example, in a scanning mirror 40 (scanning mirror 40 whose reflective surface has an inclination angle of +10 degrees in the xz plane) that emits a 0-degree incidence light beam at 20 degrees in the +x-axis direction, the actual incidence angle on the reflective surface of scanning mirror 40 of a 20-degree incidence light beam (an incidence angle of 20 degrees in the -x-axis direction based on the first normal) is 30 degrees in the -x-axis direction. As a result, scanning mirror 40 that emits a 0-degree incidence light beam at 20 degrees in the +x-axis direction functions so that a 20-degree incidence light beam is emitted at an angle of 40 degrees in the +x-axis direction based on the first normal. Furthermore, for example, in a scanning mirror 40 for emitting a 0-degree incident light beam at 20 degrees in the −x-axis direction (a scanning mirror 40 in which the tilt angle of the reflecting surface in the x-z plane is −10 degrees), the actual incident angle of the 20-degree incident light beam on the reflecting surface of the scanning mirror 40 is 10 degrees in the −x-axis direction. As a result, the scanning mirror 40 for emitting a 0-degree incident light beam at 20 degrees in the −x-axis direction functions so that the 20-degree incident light beam is emitted at an angle of 0 degrees in the x-axis direction with respect to the first normal. FIG. 8 shows how the scanning trajectory of such a 20-degree incident light beam moves in the range from 0 degrees to 40 degrees in the x-axis direction. Here, it can be seen that when a 20-degree incident light beam is emitted at an angle of approximately 40 degrees in the +x-axis direction, in other words, when the actual incident angle of the light beam on the reflecting surface of the scanning mirror 40 increases to approximately 40 degrees, the distortion of the scanning trajectory of the light beam increases.

[0040] The same applies to the cases of 40-degree incidence and 60-degree incidence. For example, in the case of 40-degree incidence, there is a difference of 40 degrees in the -x-axis direction between the incident angle assumed for the above two-dimensional scanning and the actual incident angle. Therefore, for example, in a scanning mirror 40 (scanning mirror 40 whose reflective surface has an inclination angle of +10 degrees in the xz plane) that emits a 0-degree incident light beam at 20 degrees in the +x-axis direction, the actual incident angle on the reflective surface of scanning mirror 40 of a 40-degree incident light beam (40 degrees incident angle in the -x-axis direction with respect to the first normal) is 50 degrees in the -x-axis direction. As a result, the scanning mirror 40 that emits a 0-degree incident light beam at 20 degrees in the +x-axis direction functions so that a 40-degree incident light beam is emitted at an angle of 60 degrees in the +x-axis direction with respect to the first normal. Furthermore, for example, in a scanning mirror 40 for emitting a 0-degree incident light beam at 20 degrees in the -x-axis direction (a scanning mirror 40 in which the tilt angle of the reflecting surface in the xz plane is -10 degrees), the actual incident angle of a 40-degree incident light beam on the reflecting surface of scanning mirror 40 is 30 degrees in the -x-axis direction. As a result, scanning mirror 40 for emitting a 0-degree incident light beam at 20 degrees in the -x-axis direction functions so that a 40-degree incident light beam is emitted at an angle of 20 degrees in the +x-axis direction with respect to the first normal. Looking at Figure 8, it can be seen that for a 40-degree incident light beam, when it is emitted at an angle of approximately 60 degrees in the +x-axis direction, in other words, when the actual incident angle of the light beam on the reflecting surface of scanning mirror 40 becomes large, such as approximately 50 degrees, the distortion of the scanning trajectory of the light beam becomes large.

[0041] Furthermore, comparing 20-degree incidence with 40-degree incidence, it can be seen that as the angle of incidence of the light beam on the scanning mirror 40 in the x-axis direction increases, the distortion of the scanning trajectory of the light beam increases. That is, when the light beam is scanned by the scanning mirror 40, the scanning trajectory of the light beam 12, which has a relatively small angle of incidence on the scanning mirror 40, is not distorted much, but the scanning trajectories of the light beams 22 and 32, which have a relatively large angle of incidence on the scanning mirror 40, are significantly distorted. In order to correct such distortion of the scanning area, the light beam scanning device 1 is provided with a scanning area correction optical member 45.

[0042] 9 to 11 show a light beam scanning device 2 of a first comparative example. The light beam scanning device 2 of the first comparative example has a configuration similar to that of the light beam scanning device 1 of the present embodiment, but differs mainly in the following respects. The light beam scanning device 2 of the first comparative example does not have a scanning area correction optical member 45. Furthermore, in the light beam scanning device 2 of the first comparative example, the distances D1, D2, and D3 are equal to each other. Therefore, the beam shaping effects imparted to the light beams 12, 22, and 32 are equal. For simplicity, the light beam 32 is not shown in FIGS. 9 to 11.

[0043] FIG. 12 is an explanatory diagram showing a scanning area generated by the light beam scanning device 2 of the first comparative example. Because a rectangular shape is often required for the scanning area, the light beam scanning device 2 generates rectangular scanning areas 71, 72, and 73 by two-dimensionally swinging the reflecting surface of the scanning mirror 40 around the x-axis and y-axis directions. The larger the angle of incidence of the light beam on the scanning mirror 40, the greater the distortion of the shape of the scanning area formed by the light beam. Specifically, the angle of incidence of the light beam 22 on the scanning mirror 40 is greater than the angle of incidence of the light beam 12 on the scanning mirror 40. Therefore, as shown in FIG. 12, the shape of the scanning area 72 formed by the light beam 22 is more distorted than the shape of the scanning area 71 formed by the light beam 12. The angle of incidence of the light beam 32 on the scanning mirror 40 is greater than the angle of incidence of the light beam 12 on the scanning mirror 40. Therefore, as shown in FIG. 12, the shape of the scanning area 73 formed by the light beam 32 is more distorted than the shape of the scanning area 71 formed by the light beam 12.

[0044] In Figure 12, r x represents the rotation angle of the scanning mirror 40 around the x-axis, and r y represents the rotation angle of the scanning mirror 40 around the y-axis. In FIG. 12, the coordinate of the central angle of the scanning area 71 is set as the origin. Since the light beam 22 and the light beam 32 are symmetrical with respect to a vertical plane (yz plane) including the optical path of the light beam 12, the scanning areas 72 and 73 are also symmetrical with respect to the y-axis. x12, the incident angle of light beam 22 on scanning mirror 40 is relatively small, so the distortion of scanning area 71 is also small. In contrast, the incident angles of light beams 22 and 32 on scanning mirror 40 are relatively large, so scanning areas 72 and 73 are significantly distorted. Also, as in the example shown in FIG. 8, the larger the incident angle of the light beam on scanning mirror 40 and the larger the rotation angle of scanning mirror 40, the greater the distortion of the scanning area.

[0045] The scan area correction optical member 45 corrects distortion of the shape of at least one of the scan areas 71, 72, and 73 formed by the light beams 12, 22, and 32 scanned by the scan mirror 40. Specifically, the scan area correction optical member 45 corrects distortion of the shape of at least two of the scan areas 71, 72, and 73 (e.g., the scan areas 72 and 73). More specifically, the scan area correction optical member 45 corrects distortion of the shape of all of the scan areas 71, 72, and 73.

[0046] The scan area correction optical element 45 deflects the light beam (changes the traveling direction of the light beam) by utilizing a refractive or reflective effect on the light beam. For example, the shape of the scan area can be corrected by varying the refractive power acting on the light beam depending on the incident position of the light beam on the scan area correction optical element 45. For example, the scan area correction optical element 45 is an optical element that imparts different refractive power to the light beam incident on the scan area correction optical element 45 depending on the incident position of the light beam on the scan area correction optical element 45. The refractive power imparted by the scan area correction optical element 45 to the light beam may be positive or negative. Furthermore, the scan area correction optical element 45 may impart positive refractive power to the light beam at one position on the scan area correction optical element 45 and negative refractive power to the light beam at another position on the scan area correction optical element 45. The scanning area correction optical element 45 may, for example, deflect the light beam so that the light beam incident on the scanning area correction optical element 45 is emitted in a direction determined depending on the incident position of the light beam on the scanning area correction optical element 45.

[0047] The scanning area correction optical member 45 is, for example, a lens having a free-form surface shape (see FIGS. 1 to 3) or a mirror having a free-form surface shape. The free-form surface of the scanning area correction optical member 45 provides an appropriate deflection action to the light beam to correct the multiple scanning areas to appropriate shapes. Figure 16 shows multiple scanning areas 71, 72, and 73 generated by the light beam scanning device 1 of this embodiment.

[0048] The scan area correction optical element 45 may have, for example, negative refractive power in the slow axis direction of each of the light beams 12, 22, and 32. In this case, the negative refractive power of the scan area correction optical element 45 with respect to the light beam 22 in the slow axis direction of the light beam 22 is stronger than the negative refractive power of the scan area correction optical element 45 with respect to the light beam 12 in the slow axis direction of the light beam 12. Furthermore, the negative refractive power of the scan area correction optical element 45 with respect to the light beam 32 in the slow axis direction of the light beam 32 is stronger than the negative refractive power of the scan area correction optical element 45 with respect to the light beam 12 in the slow axis direction of the light beam 12. Therefore, the scan area correction optical element 45 can correct the shape of the scan area 72 more greatly than the shape of the scan area 71, and can correct the shape of the scan area 73 more greatly than the shape of the scan area 71. As shown in FIG. 16, distortion of the shape of each of the scan areas 71, 72, and 73 is reduced, and each of the scan areas 71, 72, and 73 is corrected to a desired shape, such as a substantially rectangular shape.

[0049] The scan area correction optical element 45 may have, for example, a positive refractive power in the slow axis direction of each of the light beams 12, 22, and 32. In this case, the positive refractive power of the scan area correction optical element 45 for the light beam 22 in the slow axis direction of the light beam 22 is stronger than the positive refractive power of the scan area correction optical element 45 for the light beam 12 in the slow axis direction of the light beam 12. Furthermore, the positive refractive power of the scan area correction optical element 45 for the light beam 32 in the slow axis direction of the light beam 32 is stronger than the positive refractive power of the scan area correction optical element 45 for the light beam 12 in the slow axis direction of the light beam 12. Therefore, the scan area correction optical element 45 can correct the shape of the scan area 72 more greatly than the shape of the scan area 71, and can correct the shape of the scan area 73 more greatly than the shape of the scan area 71. As shown in FIG. 16, distortion of the shape of each of the scan areas 71, 72, and 73 is reduced, and each of the scan areas 71, 72, and 73 is corrected to a desired shape, such as a substantially rectangular shape.

[0050] The scan area correction optical element 45 may be designed, for example, to have almost no optical effect on a light beam having a relatively small angle of incidence on the scan mirror 40 (e.g., light beam 12), and to have a large optical effect on a light beam having a relatively large angle of incidence on the scan mirror 40 (e.g., light beams 22 and 32). This optical effect may be a negative refractive power, a positive refractive power, or a mixture of negative and positive refractive powers (e.g., a negative refractive power is imparted to a light beam incident on one position of the scan area correction optical element 45, and a positive refractive power is imparted to a light beam incident on another position of the scan area correction optical element 45).

[0051] The above-described deflection effect of the scan area correction optical element 45 may change the divergence angle of the light beam, thereby reducing the parallelism of the light beam. That is, the scan area correction optical element 45 provides a deflection effect that is a positive effect for correcting distortion in the scan area, but may also have a negative effect on beam quality, such as reducing the parallelism of the light beam. For example, even if a beam shaper collimates a light beam, the scan area correction optical element 45 converts the light beam into divergent or convergent light, thereby reducing the parallelism of the light beam. Whether the light beam is divergent or convergent immediately after being emitted from the scan area correction optical element 45, the light beam becomes divergent at an object far from the light beam scanning device 1. Therefore, if the parallelism of the light beam emitted from the scan area correction optical element 45 decreases, an object far from the light beam scanning device 1 will be illuminated with a light beam with low brightness, reducing the accuracy of measuring the object's position.

[0052] On the other hand, if the refractive power imparted to the light beam by the scanning area correction optical member 45 varies depending on the incident position of the light beam on the scanning area correction optical member 45, the amount of change in the divergence angle of the light beam emitted from the scanning area correction optical member 45 by the scanning area correction optical member 45 will vary depending on the incident position of the light beam on the scanning area correction optical member 45 and the beam diameter of the light beam at the scanning area correction optical member 45. In this embodiment, the parallelism of the light beam emitted from the scanning area correction optical member 45 is improved by adjusting the inter-lens distance in the beam shaper while maintaining the effect of correcting the distortion of the scan area by the scanning area correction optical member 45. An example of adjusting the distance between the front lens and the rear lens between multiple beam shapers in the light beam scanning device 1 of this embodiment will be shown, compared with the light beam scanning device 2b of the second comparative example shown in FIGS. 13 to 15 . Note that, for simplicity, the light beam 32 is not shown in FIGS. 13 to 15 .

[0053] 13 to 15, the light beam scanning device 2b of the second comparative example further includes a scanning area correction optical member 45 compared to the light beam scanning device 2 of the first comparative example. However, in the light beam scanning device 2b of the second comparative example, the distances D1, D2, and D3 are equal to one another, similar to the light beam scanning device 2 of the first comparative example. Note that other points are similar to the light beam scanning device 1 of the present embodiment.

[0054] To increase the light intensity of each of the light beams 12, 22, and 32, light sources having high output power, such as multimode diode lasers, may be employed as the light sources 11, 21, and 31. In such light sources, the width W1 (see FIG. 4) of the emitter 60 of each of the light sources 11, 21, and 31 in the slow axis direction of each of the light beams 12, 22, and 32 is greater than the width W2 (see FIG. 4) of the emitter 60 of each of the light sources 11, 21, and 31 in the fast axis direction of each of the light beams 12, 22, and 32.

[0055] Figure 17 is a diagram showing the relationship between the light-emitting point width W, the focal length f of the lens optical system, and the divergence angle θ of a light beam that has passed through the lens optical system. Generally, the divergence angle θ of a light beam that has been emitted from the light-emitting point and passed through the lens optical system is given by the following equation (1). The larger the light-emitting point width W, the larger the divergence angle θ of the light beam after passing through the lens optical system. The longer the focal length f of the lens optical system, the smaller the divergence angle θ of the light beam after passing through the lens optical system.

[0056] θ ≒ W / f … (1) In this disclosure, the light-emitting spot width W corresponds to the width of the emitter of the light source. The lens optical system corresponds to a composite lens formed by combining a front lens and a rear lens provided in the beam shaper. The divergence angle θ of the light beam corresponds to the divergence angle of each of the light beams 12, 22, and 32 emitted from the beam shaper. Therefore, when the focal length of the beam shaper 13 (composite lens) in the slow axis direction of the light beam 12 is equal to the focal length of the beam shaper 13 (composite lens) in the fast axis direction of the light beam 12, the divergence angle of the light beam 12 passing through the beam shaper 13 in the slow axis direction is larger than the divergence angle of the light beam 12 passing through the beam shaper 13 in the fast axis direction. The same applies to the light beams 22 and 32.

[0057] In light of equation (1), if the width W2 of the emitter 60 in the fast axis direction (hereinafter also referred to as the "light-emitting spot width Wf") is sufficiently small so that the emitter 60 can be optically regarded as a point in the fast axis direction, the divergence angle of each light beam in the fast axis direction is sufficiently small even if the focal length of each beam shaper in the fast axis direction (the combined focal length of the front and rear lenses) is short. Therefore, the front lens may be primarily responsible for beam shaping of each beam shaper in the fast axis direction, and the focal length of the front lens in the fast axis direction of each beam shaper may be shortened (i.e., the positive refractive power of the front lens in each beam shaper may be strengthened). In this way, the divergence angle of each light beam in the fast axis direction can be sufficiently small, and the beam diameter of each light beam in the fast axis direction can be reduced.

[0058] In contrast, the width W1 of the emitter 60 in the slow axis direction (hereinafter also referred to as the "light-emitting spot width Ws") is sufficiently large that the emitter 60 cannot be regarded as an optical point in the slow axis direction. Therefore, in accordance with Equation (1), the focal length of each beam shaper in the slow axis direction (the combined focal length of the front and rear lenses) is increased to reduce the divergence angle of each light beam in the slow axis direction. However, as the focal length of each beam shaper in the slow axis direction increases, the beam diameter of each light beam emitted from each beam shaper increases. Therefore, the negative effect of the scanning area correction optical member 45 (for example, the effect of the curvature of the scanning area correction optical member 45, which reduces the parallelism of the light beam) becomes greater in the slow axis direction.

[0059] Based on the above relationship between the parallelism of the light beam and the beam diameter of the light beam, the beam shaper is designed as follows. Specifically, in the fast axis direction, a positive refractive power is imparted only to the front lens, and the focal length F1f of the front lens is shortened. Therefore, in the fast axis direction, the parallelism of each light beam at the scan area correction optical member 45 is high, and the beam diameter of each light beam at the scan area correction optical member 45 is small. Not only the light beam 12, but also the light beams 22 and 32, which have a large angle of incidence on the scanning mirror 40, can be made less susceptible to the effect of the curvature of the scan area correction optical member 45. In addition, there is no need to adjust the distance between the light source and the front lens for each light source module.

[0060] On the other hand, in the slow axis direction, the beam diameter of each light beam is large in the scanning area correction optical member 45. Furthermore, each of the scanning areas 72 and 73 is corrected more greatly by the scanning area correction optical member 45 than the scanning area 71. Therefore, in the slow axis direction, the light beams 22 and 32, which have a larger angle of incidence on the scanning mirror 40, are more significantly affected by the scanning area correction optical member 45 (the effect of the curvature of the scanning area correction optical member 45) than the light beam 12.

[0061] Therefore, in this embodiment, the position of the rear lens relative to the front lens is adjusted depending on the strength of the negative effect of the scan area correction optical element 45 (the effect of the curvature of the scan area correction optical element 45). Depending on the strength of the negative effect of the scan area correction optical element 45, the focal length in the slow axis direction of the light beam emitted from the beam shaper changes, and the divergence angle in the slow axis direction of the light beam emitted from the beam shaper changes. At least a part of the negative effect of the scan area correction optical element 45 is offset by the divergence angle in the slow axis direction of the light beam emitted from the beam shaper. In this way, the parallelism of each light beam in the scan area correction optical element 45 is improved. The quality of the light beam emitted from the scan area correction optical element 45 can be improved. Note that each beam shaper may have the effect of making the beam diameter in the fast axis direction of each of the multiple light beams incident on the scan area correction optical element 45 smaller than the beam diameter in the slow axis direction.

[0062] In the example of this embodiment shown in FIGS. 1 to 3, the scan area correction optical element 45 imparts negative refractive power in the slow axis direction to the light beams 22 and 32, which have a larger angle of incidence on the scan mirror 40 than the light beam 12. In this case, the distance between the front lens and the rear lens in the beam shaper 23 and 33 is set larger than the distance between the front lens and the rear lens in the beam shaper 13. That is, the rear lenses 15, 25, and 35 are positioned relative to the front lenses 14, 24, and 34 so that distance D1<distance D2 and distance D1<distance D3. For example, the effect of the curvature (negative refractive power) of the scan area correction optical element 45 may be corrected by intentionally shifting the rear lens from the focal position (the position where the beam shaper forms an object-side focal point at the light emission point) toward the output side, depending on the amount of the effect. As a result, the beam shaper 23 and 33 emit light beams that converge in the slow axis direction. Even if a light beam converging in the slow axis direction is emitted from the beam shapers 23 and 33, the negative refractive power of the scanning area correction optical member 45 in the slow axis direction causes the scanning area correction optical member 45 to emit a substantially parallel light beam.

[0063] In the example of this embodiment shown in FIGS. 1 to 3 , light beams 22 and 32 converging in the x-axis direction, which coincides with the slow-axis direction, are emitted from beam shapers 23 and 33, and light beam 12 parallel in the x-axis direction is emitted from beam shaper 13. Then, light beams 12, 22, and 32 of approximately parallel light are emitted from scanning area correction optical member 45. In contrast, in a light beam scanning device 2b of a second comparative example shown in FIGS. 13 to 15 , light beams 12 and 22 that are approximately parallel in the x-axis direction, which coincides with the slow-axis direction, are emitted from beam shapers 13 and 23. Then, the approximately parallel light beam 12 and light beam 22, which is diverging light, are emitted from scanning area correction optical member 45. Although light beam 32 is not shown in FIGS. 13 to 15 , light beam 32 is emitted from scanning area correction optical member 45 as diverging light, similar to light beam 22.

[0064] In a light beam scanning device 1b, which is another example of this embodiment shown in FIGS. 18 to 20, a scanning area correction optical element 45 imparts positive refractive power in the slow axis direction to light beams 22 and 32 whose incident angles on the scanning mirror 40 are larger than that of the light beam 12. In this case, the distance between the front and rear lenses in the beam shapers 23 and 33 is set smaller than the distance between the front and rear lenses in the beam shaper 13. That is, the rear lenses 15, 25, and 35 are positioned relative to the front lenses 14, 24, and 34 so that distance D1 > distance D2 and distance D1 > distance D3. For example, the effect of the curvature (positive refractive power) of the scanning area correction optical element 45 may be corrected by intentionally shifting the rear lenses from the focal position toward the incident side. This causes the beam shapers 23 and 33 to emit light beams that diverge in the slow axis direction. Even if a light beam diverging in the slow axis direction is emitted from the beam shapers 23 and 33, a substantially parallel light beam is emitted from the scanning area correction optical member 45 due to the positive refractive power of the scanning area correction optical member 45 in the slow axis direction.

[0065] In another example of this embodiment shown in Figures 18 to 20, light beams 22 and 32 diverging in the x-axis direction coinciding with the slow-axis direction are emitted from beam shapers 23 and 33, and a light beam 12 parallel in the x-axis direction is emitted from beam shaper 13. Then, the light beams 12, 22, and 32, which are substantially parallel light beams, are emitted from scanning area correction optical member 45. In contrast, in a light beam scanning device 2c of a third comparative example shown in Figures 21 and 22, the distances D1, D2, and D3 are equal to one another, and the light beams 12, 22, and 32, which are substantially parallel in the x-axis direction coinciding with the slow-axis direction, are emitted from beam shapers 13, 23, and 33. Then, the substantially parallel light beam 12 and the light beam 22, which is convergent light, are emitted from scanning area correction optical member 45. Although the light beam 32 is not shown in FIGS. 21 and 22, the light beam 32 is emitted from the scanning area correction optical member 45 as a convergent light beam, similar to the light beam 22.

[0066] In this embodiment, since the diameter of the light beam in the fast axis direction is small, the effect of the scanning area correction optical member 45 on the light beam in the fast axis direction can be ignored.

[0067] It is not necessary to collimate all of the light beams emitted from the scanning area correction optical member 45. The parallelism (spread angle) of each light beam emitted from the scanning area correction optical member 45 can be adjusted appropriately depending on the distance from the light beam scanning device 1, 1b to the object to be scanned, the desired quality of the light beam, and the like.

[0068] In the light beam scanning device 2b of the second comparative example (see FIGS. 13 to 15) and the light beam scanning device 2c of the third comparative example (see FIGS. 20 and 21), the distance between the front lens and the rear lens is equal between the beam shapers, and therefore the parallelism (divergence angle) of the light beams incident on the scanning area correction optical member 45 is equal to each other. The refractive power in the peripheral portion of the scanning area correction optical member 45 is stronger than the refractive power in the central portion of the scanning area correction optical member 45. Therefore, if the distance between the front lens and the rear lens of each beam shaper is set so that the light beam 12 emitted from the scanning area correction optical member 45 becomes a substantially parallel light, each of the light beams 22 and 32 emitted from the scanning area correction optical member 45 will diverge or converge in the slow axis direction. On the other hand, if the distance between the front lens and the rear lens of each beam shaper is set so that the light beams 22 and 32 emitted from the scanning area correction optical element 45 become approximately parallel light, the light beam 12 emitted from the scanning area correction optical element 45 will diverge or converge.

[0069] In contrast, in the light beam scanning devices 1 and 1b of this embodiment, the distances between the front and rear lenses (distances D1, D2, and D3 shown in FIG. 3) between the beam shapers are changed according to the optical effect given to the light beam by the scanning area correction optical member 45. This makes it possible to improve the parallelism of each light beam emitted from the light beam scanning devices 1 and 1b. The light beam scanning devices 1 and 1b can emit high-quality light beams.

[0070] <Modification> The light source module 30 and the reflecting mirror 37, and the light source module 20 and the reflecting mirror 27 may be arranged asymmetrically with respect to a vertical plane including the optical path of the light beam 12. For example, the incident angle of the light beam 32 on the scanning mirror 40 may be different from the incident angle of the light beam 22 on the scanning mirror 40, and the distance D3 may be different from the distance D2. For example, if the incident angle of the light beam 32 on the scanning mirror 40 is larger than the incident angle of the light beam 22 on the scanning mirror 40, and the scanning area correction optical element 45 imparts a stronger negative refractive power to the light beam 32 having a larger incident angle on the scanning mirror 40, the distance D3 may be larger than the distance D2. Furthermore, if the incident angle of the light beam 32 on the scanning mirror 40 is larger than the incident angle of the light beam 22 on the scanning mirror 40, and the scanning area correction optical element 45 imparts a stronger positive refractive power to the light beam 32 having a larger incident angle on the scanning mirror 40, the distance D3 may be smaller than the distance D2.

[0071] The fast axis direction of light beam 32 may be parallel to the fast axis direction of light beam 22 or may be non-parallel to the fast axis direction of light beam 12. The slow axis direction of light beam 32 may be parallel to the slow axis direction of light beam 22 or may be non-parallel to the slow axis direction of light beam 22.

[0072] The number of light source modules 10, 20, 30 and the number of reflecting mirrors 17, 27, 37 are not limited to three.

[0073] The effects of the light beam scanning devices 1 and 1b of this embodiment will be described. The light beam scanning device 1, 1b of this embodiment includes a plurality of light sources (e.g., light sources 11, 21, 31), a plurality of beam shapers (e.g., beam shapers 13, 23, 33), a scanning mirror 40, and a scanning area correction optical member 45. The plurality of light sources emit a plurality of light beams (e.g., light beams 12, 22, 32). Each of the plurality of light beams is emitted from a corresponding one of the plurality of light sources, and has a larger beam diameter in the fast axis direction than in the slow axis direction. Each of the plurality of beam shapers is provided for a corresponding one of the plurality of light sources, and shapes the light beam emitted from the corresponding light source. The scanning mirror 40 scans the plurality of light beams shaped by the plurality of beam shapers. The scanning area correction optical member 45 corrects at least one of a plurality of scanning areas formed by the plurality of light beams scanned by the scanning mirror 40. Each of the plurality of beam shapers includes a first lens (e.g., front lenses 14, 24, 34) and a second lens (e.g., rear lenses 15, 25, 35). The first lens is disposed closer to a corresponding one of the plurality of light sources than the second lens. Each of the plurality of beam shapers imparts positive refractive power to a corresponding one of the plurality of light beams in the slow axis direction and the fast axis direction. Each of the plurality of beam shapers has a focal length Ff in the fast axis direction and a focal length F in the slow axis direction. fThe scanning mirror 40 has a larger focal length Fs. In at least one direction, an incident angle θ1 of a first light beam (e.g., light beam 12), which is one of the multiple light beams, on the scanning mirror 40 when the scanning mirror 40 is at the center of its rotation range is different from an incident angle θ2 of a second light beam (e.g., light beam 22), which is one of the multiple light beams, on the scanning mirror 40 when the scanning mirror 40 is at the center of its rotation range. A distance D1 between a first lens (e.g., front lens 14) and a second lens (e.g., rear lens 15) in a first beam shaper (e.g., beam shaper 13), which is one of the multiple beam shapers and shapes the first light beam, is different from a distance D2 between a first lens (e.g., front lens 24) and a second lens (e.g., rear lens 25) in a second beam shaper (e.g., beam shaper 23), which is one of the multiple beam shapers and shapes the second light beam.

[0074] The light beam scanning devices 1 and 1b of the present embodiment include a scanning area correction optical member 45. Therefore, the light beam scanning devices 1 and 1b can correct distortions of the scanning areas (e.g., scanning areas 71, 72, and 73) caused by differences in the angle of incidence on the scanning mirror 40. The light beam scanning devices 1 and 1b also include beam shapers (e.g., beam shapers 13, 23, and 33), each of which includes a first lens (e.g., front lenses 14, 24, and 34) and a second lens (e.g., rear lenses 15, 25, and 35). The distances between the first and second lenses of the two beam shapers (e.g., beam shapers 13 and 23) that shape two light beams (e.g., light beams 12 and 22) that have different angles of incidence on the scanning mirror 40 are different from each other. Therefore, the quality of the light beam emitted from the scanning area correction optical member 45 is improved, for example, the parallelism of the light beam emitted from the scanning area correction optical member 45 is improved.

[0075] In other words, in a light beam scanning device 1, 1b having multiple scanning areas, when a scanning area correction optical element 45 that corrects distortions, etc. of the scanning area is provided, by varying the inter-lens distance between the beam shapers provided for at least two light beams having different angles of incidence on the scanning mirror 40, it is possible to obtain the first effect of the scanning area correction optical element 45, which is the correction effect of the scanning area by deflecting the light beam, while reducing the effect of fluctuations in the divergence angle of the emitted light (here, divergence or convergence of the emitted light), which is the second effect accompanying the above-mentioned first effect of the scanning area correction optical element 45.

[0076] In the light beam scanning device 1 of this embodiment, the incident angle θ2 is larger than the incident angle θ1. The scanning area correction optical member 45 applies negative refractive power to the second light beam in the slow axis direction. The distance D2 is larger than the distance D1.

[0077] Therefore, the light beam scanning device 1 can correct distortions and the like in the scanning areas (for example, the scanning areas 71, 72, and 73), and can improve the quality of the light beam emitted from the scanning area correction optical member 45.

[0078] In the light beam scanning device 1b of this embodiment, the incident angle θ2 is larger than the incident angle θ1. The scanning area correction optical member 45 provides a positive refractive power to the second light beam in the slow axis direction. The distance D2 is smaller than the distance D1.

[0079] Therefore, the light beam scanning device 1b can correct distortions and the like in the scanning areas (for example, the scanning areas 71, 72, and 73), and can improve the quality of the light beam emitted from the scanning area correction optical member 45.

[0080] In the light beam scanning device 1, 1b of this embodiment, the first lens (e.g., the front lens 14, 24, 34) has positive refractive power in the fast axis direction. The second lens (e.g., the rear lens 15, 25, 35) has positive refractive power in the slow axis direction. The focal length F2s of the second lens in the slow axis direction is greater than the focal length F1f of the first lens in the fast axis direction.

[0081] Therefore, the parallelism of the light beam in the slow axis direction is Raise Furthermore, the beam diameter of the light beam in the fast axis direction at the scanning area correction optical element 45 is smaller than the beam diameter of the light beam in the slow axis direction at the scanning area correction optical element 45. The reduction in parallelism of the light beam in the fast axis direction caused by the scanning area correction optical element 45 is negligible. The quality of the light beam emitted from the scanning area correction optical element 45 can be improved.

[0082] In the light beam scanning devices 1 and 1b of the present embodiment, the second lens (for example, the rear lenses 15, 25, and 35) has zero refractive power in the fast axis direction.

[0083] Therefore, by moving the second lens (e.g., rear lens 15, 25, 35), the distance (e.g., distances D1, D2, D3) between the first lens (e.g., front lens 14, 24, 34) and the second lens can be adjusted without affecting the parallelism of the light beam in the fast axis direction. The parallelism of the light beam resulting from the scan area correction optical element 45 is improved. The quality of the light beam emitted from the scan area correction optical element 45 can be improved.

[0084] In the light beam scanning devices 1 and 1b of the present embodiment, the first lens (for example, the front lenses 14, 24, and 34) has negative refractive power in the slow axis direction.

[0085] Therefore, the beam shaper (for example, the beam shaper 13, 23, 33) can be made smaller, and the optical beam scanning devices 1 and 1b can be made smaller.

[0086] In the light beam scanning devices 1 and 1b of the present embodiment, the divergence angle of the light beam incident on a first lens (e.g., front lens 14, 24, 34) in the slow axis direction is smaller than the divergence angle of the light beam incident on the first lens in the fast axis direction. The divergence angle of the light beam incident on a second lens (e.g., rear lens 15, 25, 35) in the slow axis direction is larger than the divergence angle of the light beam incident on the second lens in the fast axis direction.

[0087] Therefore, distortions and the like in the scanning areas (for example, scanning areas 71, 72, 73) can be corrected, and the effect of improving the quality of the light beam emitted from the scanning area correction optical member 45 can be more easily achieved.

[0088] In the optical beam scanning devices 1 and 1b of the present embodiment, each of the multiple light sources (e.g., light sources 11, 21, and 31) is a multimode laser diode. The emitter width of the multimode laser diode in the slow axis direction is larger than the emitter width of the multimode laser diode in the fast axis direction.

[0089] This allows the power of the light beams (for example, the light beams 12, 22, and 32) to be increased, and the light beam scanning devices 1 and 1b can scan objects that are located farther away.

[0090] In the light beam scanning device 1, 1b of this embodiment, each of the multiple light beams incident on the scanning area correction optical member 45 has a beam diameter in the fast axis direction and a beam diameter in the slow axis direction, and the beam diameter in the fast axis direction is smaller than the beam diameter in the slow axis direction.

[0091] Therefore, in the fast axis direction, the decrease in parallelism of the light beam caused by the scanning area correction optical member 45 is negligible, and the quality of the light beam emitted from the scanning area correction optical member 45 can be improved.

[0092] In the light beam scanning devices 1 and 1b of this embodiment, the scanning area correction optical member 45 is a lens having a free curved surface shape or a mirror having a free curved surface shape.

[0093] The free-form surface of the scanning area correction optical member 45 can provide an appropriate deflection action to the light beam, thereby correcting the multiple scanning areas to appropriate shapes.

[0094] In the light beam scanning devices 1 and 1b of this embodiment, the amount of change in the divergence angle that the scanning area correction optical member 45 gives to the first light beam is different from the amount of change in the divergence angle that the scanning area correction optical member 45 gives to the second light beam.

[0095] This improves the parallelism of the light beam emitted from the scanning area correction optical member 45. The quality of the light beam emitted from the scanning area correction optical member 45 can be improved.

[0096] In the light beam scanning devices 1 and 1b of the present embodiment, the multiple light sources include a first light source (e.g., light source 11), a second light source (e.g., light source 21), and a third light source (e.g., light source 31). The angle of incidence of the light beam (e.g., light beam 12) emitted by the first light source onto the scanning mirror 40 is different from at least one of the angle of incidence of the light beam (e.g., light beam 22) emitted by the second light source onto the scanning mirror 40 and the angle of incidence of the light beam (e.g., light beam 32) emitted by the third light source onto the scanning mirror 40.

[0097] This improves the parallelism of the light beam emitted from the scanning area correction optical member 45 due to differences in the angle of incidence on the scanning mirror 40. The quality of the light beam emitted from the scanning area correction optical member 45 can be improved.

[0098] In the light beam scanning device 1, 1b of this embodiment, at least one direction is a direction perpendicular to the rotation axis of the scanning mirror, a direction in which the difference in incident angle to the scanning mirror between multiple light beams is greatest, or the longitudinal direction of multiple scanning areas.

[0099] By selecting a direction in which distortion in the scanning area is likely to be large, it is possible to correct distortion in the scanning area (e.g., scanning areas 71, 72, 73), and it is easier to achieve the effect of improving the quality of the light beam emitted from the scanning area correction optical element 45.

[0100] In the light beam scanning devices 1 and 1b of the present embodiment, the plurality of scanning regions are each expanded.

[0101] Therefore, the light beam scanning devices 1 and 1b can scan a wider area. In the light beam scanning devices 1 and 1b of the present embodiment, the multiple scanning areas have multiple centers. Each of the multiple centers is the center of a corresponding scanning area among the multiple scanning areas. The positions of the multiple centers are different from one another.

[0102] Therefore, the light beam scanning devices 1 and 1b can scan a wider area. Embodiment 2 A distance measuring device 3 according to the second embodiment will be described with reference to Fig. 23. Fig. 23 is a schematic diagram showing an example of a distance measuring device 3 according to the third embodiment. As shown in Fig. 23, the distance measuring device 3 includes the light beam scanning device 1 according to the first embodiment, a light receiving optical system 81, a light receiving device 82, a computer 83, and a housing 87.

[0103] The light receiving optical system 81 guides the return beams 12r, 22r, and 32r, which are generated when the light beams 12, 22, and 32 are reflected or scattered by the object 88, to the light receiving device 82. The light receiving optical system 81 includes, for example, a condenser lens. The light receiving device 82 receives the return beams 12r, 22r, and 32r. The light receiving device 82 is, for example, a photodiode such as an avalanche photodiode or a single-photon avalanche photodiode.

[0104] The computer 83 includes a controller 84, an arithmetic unit 85, and a storage device 86 such as a ROM or a hard disk. The controller 84 and the arithmetic unit 85 are, for example, processors included in the computer 83, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an FPGA (Field-Programmable Gate Array).

[0105] The controller 84 is communicably connected to the light sources 11, 21, and 31, the scanning mirror 40, and the light receiving device 82. The controller 84 controls the distance measuring device 3.

[0106] Specifically, the controller 84 controls the light sources 11, 21, and 31 to control the timing at which the pulsed light beams 12, 22, and 32 are emitted from the light sources 11, 21, and 31. The controller 84 receives, from the light sources 11, 21, and 31, first timings at which the light sources 11, 21, and 31 emit the light beams 12, 22, and 32. The first timings include the timing at which the light source 11 emits the light beam 12, the timing at which the light source 21 emits the light beam 22, and the timing at which the light source 31 emits the light beam 32.

[0107] The controller 84 controls the scanning mirror 40. The controller 84 receives the tilt angle of the scanning mirror 40 (for example, the angle of the normal to the reflecting surface of the scanning mirror 40). The controller 84 receives, from the light receiving device 82, a signal corresponding to the amount of light of the return light 12r, 22r, and 32r received by the light receiving device 82. The controller 84 receives a second timing at which the light receiving device 82 receives the return light 12r, 22r, and 32r. The second timing includes the timing at which the light receiving device 82 receives the return light 12r, the timing at which the light receiving device 82 receives the return light 22r, and the timing at which the light receiving device 82 receives the return light 32r.

[0108] The calculator 85 calculates the direction and distance of the object 88 based on the emission direction of the light beams 12, 22, 32, the first timing when the light sources 11, 21, 31 emit the light beams 12, 22, 32, and the second timing when the light receiving device 82 receives the return light 12r, 22r, 32r.

[0109] Specifically, the calculator 85 calculates the emission directions of the light beams 12, 22, and 32 from the tilt angle of the scanning mirror 40 received by the controller 84 and the positions of the light sources 11, 21, and 31 relative to the scanning mirror 40 stored in the storage device 86. The calculator 85 receives from the controller 84 a first timing at which the light sources 11, 21, and 31 emit the light beams 12, 22, and 32. The calculator 85 receives from the controller 84 a second timing at which the light receiving device 82 receives the returned light beams 12r, 22r, and 32r.

[0110] The calculator 85 calculates the distance from the distance measuring device 3 to the object 88 and the direction of the object 88 relative to the distance measuring device 3 based on the emission directions, first timing, and second timing of the light beams 12, 22, and 32. The calculator 85 generates a distance image of the object 88 including the distance from the distance measuring device 3 to the object 88 and the direction of the object 88 relative to the distance measuring device 3. The calculator 85 outputs the distance image of the object 88 to a display device (not shown) communicatively connected to the storage device 86 or the computer 83. The display device displays the distance image of the object 88.

[0111] The housing 87 houses the light beam scanning device 1, the light receiving optical system 81, the light receiving device 82, and the computer 83. The housing 87 is provided with a transparent window (not shown) that transmits the light beams 12, 22, and 32 and the return light 12r, 22r, and 32r. The computer 83 may be disposed outside the housing 87.

[0112] The distance measuring device 3 may include a light beam scanning device 1b instead of the light beam scanning device 1 of the first embodiment.

[0113] The distance measuring device 3 of this embodiment has the following effects in addition to the effects of the light beam scanning devices 1 and 1b of the first embodiment.

[0114] The distance measuring device 3 of this embodiment includes the light beam scanning device 1 or the light beam scanning device 1b, a light receiving device 82, and a computing unit 85. The light receiving device 82 receives first return light (e.g., return light 12r) generated by a first light beam (e.g., light beam 12) being reflected or scattered by an object 88, and second return light (e.g., return light 22r) generated by a second light beam (e.g., light beam 22) being reflected or scattered by the object 88. The calculator 85 calculates the direction and distance of the object 88 based on the first emission direction of the first light beam, the second emission direction of the second light beam, the first emission timing at which the first light source (e.g., light source 11) emits the first light beam, the second emission timing at which the second light source (e.g., light source 21) emits the second light beam, the first light reception timing at which the light receiving device 82 receives the first return light, and the second light reception timing at which the light receiving device 82 receives the second return light.

[0115] The distance measuring device 3 includes the light beam scanning device 1 or the light beam scanning device 1b, so that the position of the object 88 can be measured with improved accuracy using the first light beam (e.g., light beam 12) and the second light beam (e.g., light beam 22).

[0116] The first and second embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0117] 1,1b,2,2b,2c Optical beam scanning device, 3 Distance measuring device, 10,20,30 Light source module, 11,21,31 Light source, 12,22,32 Light beam, 12r,22r,32r Return light, 13,23,33 Beam shaper, 14,24,34 Front lens, 15,25,35 Rear lens, 17,27,37 Reflecting mirror, 40 Scanning mirror, 45 Scanning area correction optical member, 51 Substrate, 52,54 Cladding layer, 53 Active layer, 55 Ridge portion, 56,57 Electrode, 59 Insulating layer, 60 Emitter (light emitting point), 71,72,73 Scanning area, 71c,72c,73c Center, 81 Light receiving optical system, 82 Light receiving device, 83 Computer, 84 Controller, 85 computing unit, 86 storage device, 87 housing, 88 object

Claims

1. a plurality of light sources that emit a plurality of light beams, each of the plurality of light beams being emitted from a corresponding one of the plurality of light sources and having a beam diameter that is larger in the fast axis direction than in the slow axis direction; further comprising a plurality of beam shapers, each of which is provided for a corresponding one of the plurality of light sources and shapes the light beam emitted from the corresponding light source; a scanning mirror that scans the plurality of light beams shaped by the plurality of beam shapers; a scanning area correction optical member that corrects at least one of a plurality of scanning areas formed by the plurality of light beams scanned by the scanning mirror, each of the plurality of beam shapers includes a first lens and a second lens, and the first lens is disposed closer to a corresponding one of the plurality of light sources than the second lens; each of the plurality of beam shapers imparts positive refractive power to a corresponding one of the plurality of light beams in the slow-axis direction and the fast-axis direction, and each of the plurality of beam shapers has a focal length Ff in the fast-axis direction and a focal length Fs in the slow-axis direction that is greater than the focal length Ff; an incident angle θ1 of a first light beam, which is one of the plurality of light beams, on the scanning mirror when the scanning mirror is at the center of a rotation range of the scanning mirror is different from an incident angle θ2 of a second light beam, which is one of the plurality of light beams, on the scanning mirror when the scanning mirror is at the center of the rotation range in at least one direction; a distance D between the first lens and the second lens in a first beam shaper that is one of the plurality of beam shapers and shapes the first light beam; １ is a distance D between the first lens and the second lens in a second beam shaper that is one of the plurality of beam shapers and shapes the second light beam. ２ An optical beam scanning device that is different from the above.

2. The incident angle θ2 is greater than the incident angle θ1, the scanning area correction optical member provides a negative refractive power to the second light beam in the slow-axis direction; The distance D ２ is the distance D １ The optical beam scanning device of claim 1 .

3. The incident angle θ2 is greater than the incident angle θ1, the scanning area correction optical member provides a positive refractive power to the second light beam in the slow-axis direction; The distance D ２ is the distance D １ 10. The optical beam scanning device of claim 1, wherein the optical beam scanning device is smaller than the optical beam scanning device of claim 1.

4. the first lens has a positive refractive power in the fast axis direction, the second lens has a positive refractive power in the slow axis direction, 4. The light beam scanning device according to claim 1, wherein a focal length F2s of the second lens in the slow axis direction is greater than a focal length F1f of the first lens in the fast axis direction.

5. 5. The optical beam scanning device according to claim 4, wherein the second lens has zero refractive power in the fast axis direction.

6. 6. The light beam scanning device according to claim 4, wherein the first lens has a negative refractive power in the slow axis direction.

7. a divergence angle of the light beam incident on the first lens in the slow axis direction is smaller than a divergence angle of the light beam incident on the first lens in the fast axis direction; 7. The light beam scanning device according to claim 4, wherein a divergence angle of the light beam incident on the second lens in the slow axis direction is larger than a divergence angle of the light beam incident on the second lens in the fast axis direction.

8. each of the plurality of light sources is a multimode laser diode; 8. The optical beam scanning device according to claim 1, wherein an emitter width of the multimode laser diode in the slow axis direction is larger than an emitter width of the multimode laser diode in the fast axis direction.

9. 9. The light beam scanning device according to claim 1, wherein each of the plurality of light beams incident on the scanning area correction optical element has a beam diameter in the fast axis direction and a beam diameter in the slow axis direction, and the beam diameter in the fast axis direction is smaller than the beam diameter in the slow axis direction.

10. 10. The light beam scanning device according to claim 1, wherein the scanning area correction optical member is a lens having a free-form surface shape or a mirror having a free-form surface shape.

11. 11. The light beam scanning device according to claim 1, wherein the amount of change in the divergence angle imparted to the first light beam by the scanning area correction optical element is different from the amount of change in the divergence angle imparted to the second light beam by the scanning area correction optical element.

12. the plurality of light sources include a first light source, a second light source, and a third light source; 11. The light beam scanning device according to claim 1, wherein an incident angle of the light beam emitted by the first light source onto the scanning mirror is different from at least one of an incident angle of the light beam emitted by the second light source onto the scanning mirror and an incident angle of the light beam emitted by the third light source onto the scanning mirror.

13. 13. The light beam scanning device according to claim 1, wherein the at least one direction is a direction perpendicular to a rotation axis of the scanning mirror, a direction in which the difference in incident angle to the scanning mirror between the plurality of light beams is greatest, or a longitudinal direction of the plurality of scanning areas.

14. 14. The optical beam scanning device according to claim 1, wherein the plurality of scanning regions are larger than each of the plurality of scanning regions.

15. the plurality of scanning areas have a plurality of centers; each of the plurality of centers is a center of a corresponding one of the plurality of scanning regions; The light beam scanning device according to claim 1 , wherein the positions of the plurality of centers are different from each other.

16. The light beam scanning device according to any one of claims 1 to 15; a light receiving device that receives return light generated when the light beam emitted from the light beam scanning device is irradiated onto an object; and a computing unit that calculates the distance to the object based on the received return light.

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