JP2015014757A - Scanning optical system, optical scanning device, and ranging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical system for wide-angle biaxial optical scanning, an optical scanning device, and a ranging device which offer both wide-angle scanning and compactness.SOLUTION: A scanning optical system includes: a first scanning unit which has a first reflective surface and reflects and scans light entering the first reflective surface from a light source by rotating the first reflective surface about a first rotational axis; a reflective mirror which has a belt-like reflective surface, which is cut out from a portion of a spheroid or sphere surface to a predetermined width in a direction in which a rotation center axis extends and is curved in a direction crossing the rotation center axis, and is positioned such that the belt-like reflective surface extends in a light scanning direction of the first scanning unit; and a second scanning unit which has a second reflective surface and reflects and scans light from the reflective mirror in a direction crossing the light scanning direction of the first scanning unit by rotating the second reflective surface about a second rotational axis. The first scanning unit and the second scanning unit are positioned on the rotation center axis of the reflective mirror with a space therebetween such that the light entering from the first scanning unit is reflected by the reflective mirror and enters the second scanning unit.

Description

  The present invention relates to a scanning optical system, an optical scanning device, and a distance measuring device.

  Conventionally, a scanning optical system using two scanners (for example, a movable mirror such as a galvano mirror) is widely used as a scanning optical system that scans light in two axial directions. A configuration in which a relay lens is disposed between two scanners is also known (Patent Document 1). In addition, it has been proposed to use a relay mirror instead of the relay lens (Patent Documents 2 and 3).

  Patent Document 2 discloses a first scanning unit that reflects and scans light incident on a first light reflecting surface from a light source by swinging a first movable plate having a first light reflecting surface, and a first scanning unit. The elliptical mirror that reflects the incident light and the second movable plate having the second light reflecting surface are swung to reflect and scan the light from the elliptical mirror in a direction perpendicular to the light scanning direction of the first scanning unit. A scanning optical system that includes a second scanning unit and performs two-dimensional scanning is disclosed.

  Patent Document 3 discloses a plurality of scanners that scan incident light, and at least one mirror that is arranged between the scanners and reflects scanned light scanned from one of the plurality of scanners to the adjacent scanner side. And a scanner unit that scans the light emitted from the illumination system. In addition, a scanning apparatus including a horizontal scanner unit that scans light in a wide angle in the horizontal direction and a vertical scanner unit that scans light in a vertical direction is disclosed.

JP 2012-150238 A JP 2005-352488 A Japanese Patent Application Laid-Open No. 2012-252068

  In a general-purpose scanning optical system using two scanners, if the first scanner performs wide-angle scanning, the second scanner becomes large. When a relay lens is disposed between the two scanners, the light is condensed by the relay lens, and the second scanner is prevented from being enlarged. However, even when a relay lens is used, wide-angle scanning is difficult because the entire optical system becomes large.

  In the scanning optical system described in Patent Document 2, a curved mirror such as an elliptical mirror is used, so that the configuration can be realized in a small size. However, since the incident light is the same as the outgoing light scanning surface, a scanning angle range is provided. There are limitations.

  Similarly, the scanning optical system described in Patent Document 3 uses a curved mirror such as an elliptical mirror, so that it can be realized in a small size. However, since the beam is scanned along the elliptical surface by the first scanner, in the wide-angle region, it is between the rotation angle of the first scanner and the incident angle (= final scanning angle) to the second scanner. Linearity will be lost. In addition, since the curvature of the reflecting surface of the curved mirror changes along the light scanning direction of the first scanner, it is difficult to scan the target area while maintaining the parallel degree of the emitted light.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide wide-angle scanning and downsizing in a scanning optical system, an optical scanning device, and a distance measuring device that scan light in two axes in a wide-angle direction. An object of the present invention is to provide a scanning optical system, an optical scanning device, and a distance measuring device that can be compatible.

  In order to achieve the above object, an invention according to claim 1 is provided with a first reflecting surface, and the first reflecting surface is rotated around a first rotation axis so as to be incident on the first reflecting surface from a light source. A first scanning unit that reflects and scans the reflected light, and a band-like reflection that is cut out from a part of the spheroid or spherical surface with a predetermined width in the direction in which the rotation center axis extends and is curved in a direction intersecting the rotation center axis A reflective mirror that reflects the light incident from the first scanning unit, and a second reflective surface that is arranged so that the belt-like reflective surface extends in the optical scanning direction of the first scanning unit. A second scanning unit configured to reflect and scan light from the reflecting mirror in a direction intersecting with a light scanning direction of the first scanning unit by rotating the second reflecting surface around a second rotation axis. And light incident from the first scanning unit and reflected by the reflecting mirror is incident on the second scanning unit. On so that, the first scanning unit and each of the second scanning unit are arranged separately on the rotational center axis of the reflector, a scanning optical system.

  According to a second aspect of the present invention, the reflecting mirror has a strip-shaped reflecting surface cut out from a part of the spheroid, and the first scanning unit is on the rotational center axis of the reflecting mirror and one of the ellipses. 2. The scanning optical system according to claim 1, wherein the scanning optical system is disposed at a focal position, and the second scanning unit is disposed on the rotation center axis of the reflecting mirror and at the other focal position of the ellipse.

  According to a third aspect of the present invention, the first reflection surface of the first scanning unit obliquely intersects the first rotation axis, and the first rotation axis is at an inclination angle φ with respect to the rotation center axis of the reflecting mirror. When the light beam from the light source is incident on the first reflection surface at an incident angle θ and the second reflection surface of the second scanning unit is fixedly disposed, the first rotation shaft has the first rotation shaft. When the inclination angle φ ≠ 0 °, the deviation of the light emitted from the second scanning unit with respect to the optical scanning direction of the first scanning unit is the above-mentioned when the inclination angle φ = 0 ° of the first rotation axis. The inclination angle φ is predetermined according to the incident angle θ so that the light emitted from the second scanning unit is smaller than a deviation with respect to the optical scanning direction of the first scanning unit. 2. The scanning optical system according to 2.

  The invention according to claim 4 further converges the light incident on the first scanning unit on the light incident side of the first scanning unit so that the light emitted from the second scanning unit becomes parallel light. The scanning optical system according to any one of claims 1 to 3, wherein a correction optical system is disposed.

  The invention according to claim 5 is an optical scanning device comprising a light source for irradiating light and the scanning optical system according to any one of claims 1 to 4.

  According to a sixth aspect of the present invention, the optical scanning device according to the fifth aspect is provided, a light output unit that outputs irradiation light for scanning a predetermined monitoring area, and reflection from an obstacle in the monitoring area. A light detection unit that detects light; and a distance calculation unit that calculates a distance to the obstacle based on a delay time of reflected light output from the light output unit and detected by the light detection unit. Distance measuring device.

  According to the present invention, it is possible to achieve both wide-angle scanning and downsizing in a scanning optical system, an optical scanning device, and a distance measuring device that scan light in two axes in a wide angle direction.

It is a block diagram which shows the structure of the control system of the distance measuring device which concerns on this Embodiment. It is a schematic diagram which illustrates the monitoring area | region which the distance measuring device which concerns on this Embodiment scans. It is a perspective view which shows schematic structure of the distance measuring device to which the optical scanning device of this Embodiment is applied. (A) It is the top view which looked at the distance measuring apparatus shown in FIG. 3 from upper direction. (B) is the side view which looked at the distance measuring apparatus shown in FIG. 3 from the side. (A) is a schematic diagram which shows the shape of the reflective mirror in which a reflective surface comprises a part of spheroid. (B) is a schematic diagram showing a positional relationship among the reflecting mirror, the first scanning unit, and the second scanning unit shown in (A). (C) is a schematic diagram showing a positional relationship among a reflecting mirror whose reflecting surface forms part of a spherical surface, a first scanning unit, and a second scanning unit. (A) And (B) is a figure which shows the scanning operation of the horizontal direction in the distance measuring apparatus shown in FIG. (A) is a top view and (B) is a side view. It is a graph which shows the scanning locus at the time of arranging the 2nd scanning part fixedly. It is a side view which shows the improvement operation | movement of the scanning locus of the distance measuring device shown in FIG. (A) is the schematic which shows an example of a structure of a 1st scanning part. (B) is a schematic diagram showing the inclination angle φ of the rotation axis of the first scanning unit having the first reflecting surface. (C) is an explanatory view illustrating the principle of improving the scanning locus by the light reflected by the second reflecting surface of the second scanning unit. It is a graph which shows the improved scanning locus.

<Distance measuring device>
First, the distance measuring device according to the present embodiment will be described.
FIG. 1 is a block diagram mainly showing a configuration of a control system of the distance measuring apparatus according to the present embodiment. As shown in FIG. 1, the distance measuring apparatus 10 includes a control unit 12, a light output unit 26 that outputs irradiation light 30 that scans a predetermined monitoring area, and reflected light 32 from an obstacle in the monitoring area. Is provided. The control unit 12 is configured as a computer including a CPU, a ROM, a RAM, and an input / output unit (I / O), and serves as a distance calculation unit that calculates a distance to the obstacle based on a delay time of reflected light. Function. For example, a laser radar device that performs scanning with laser light may be used. Hereinafter, the laser radar device will be described.

  In the present embodiment, the light output unit 26 and the light detection unit 28 share a part of the configuration. The light output unit 26 includes a light source driving unit 14, a laser light source 16, a shared optical system 18, a scanning mechanism driving unit 20, and a scanning mechanism 22. The light detection unit 28 includes a shared optical system 18, a scanning mechanism driving unit 20, a scanning mechanism 22, and a photodetector 24. That is, the shared optical system 18, the scanning mechanism driving unit 20, and the scanning mechanism 22 are shared between the light output unit 26 and the light detection unit 28.

  In the distance measuring device 10, a control signal is input from the control unit 12 to the light source driving unit 14. The light source driving unit 14 generates a driving signal for driving the laser light source 16 based on the input control signal. The laser light source 16 is pulse-modulated and driven based on the input drive signal. For example, modulation is performed with a pulse width of about 10 nanoseconds. Pulse-modulated laser light is emitted from the laser light source 16. The intensity of the laser light is determined in advance according to the size of the monitoring area, such as increasing the intensity when scanning far away.

  A control signal is input from the control unit 12 to the scanning mechanism driving unit 20 so as to synchronize with the operation of the laser light source 16. The scanning mechanism driving unit 20 generates a driving signal for driving the scanning mechanism 22 based on the input control signal. The scanning mechanism 22 is driven based on the input drive signal. In the present embodiment, as will be described later, the scanning optical system is configured by the scanning mechanism 22 and the shared optical system 18. Laser light emitted from the laser light source 16 is emitted toward the monitoring region by these scanning optical systems.

  The irradiation light 30 is reflected by an obstacle in the monitoring area and returns toward the distance measuring device 10. In the present embodiment, as will be described later, the scanning mechanism 22 and the shared optical system 18 constitute a light receiving optical system. The reflected light 32 that has returned is guided to the photodetector 24 by these light receiving optical systems and is detected by the photodetector 24. The photodetector 24 includes a light receiving element, and converts the detected light into an electrical signal and amplifies it. The amplified detection signal is input from the photodetector 24 to the control unit 12.

In the control unit 12, the distance L (unit: m) to the obstacle is calculated from the delay time τ (unit: second) of the reflected light (pulse) 32 based on the relationship of τ = 2 L / c. Here, the delay time τ is a time until the laser light pulse output from the laser light source 16 is detected as a reflected light pulse by the photodetector 24. c is the speed of light (3.0 × 10 ⁸ m / sec). The calculated distance L to the obstacle is displayed on a display device (not shown) or the like as necessary.

  The light output unit 26 of the distance measuring device 10 corresponds to an “optical scanning device”. An optical system constituted by the scanning mechanism 22 and the shared optical system 18 corresponds to a “scanning optical system”.

  Here, the scanning direction will be described. FIG. 2 is a schematic diagram illustrating a monitoring region scanned by the distance measuring apparatus according to the present embodiment. In the present embodiment, the distance measuring device 10 performs wide-angle scanning of the irradiation light 30 in the biaxial direction. That is, wide angle scanning is performed in the horizontal direction, and wide angle scanning is also performed in the vertical direction orthogonal to the horizontal direction. Therefore, as shown in the figure, the monitoring region is two-dimensionally scanned by the irradiation light 30. Here, the “horizontal direction” means a direction parallel to the surface on which the distance measuring device 10 is arranged. For example, in a vehicle-mounted laser radar device, the direction parallel to the road surface is the horizontal direction. In this specification, the horizontal direction is synonymous with the “longitude direction”, and the vertical direction is synonymous with the “latitude direction”. Although the “horizontal direction” and the “vertical direction” orthogonal to the horizontal direction will be described, the two-axis directions for wide-angle scanning need only intersect.

<Optical scanning device>
Next, the optical scanning device will be described.
FIG. 3 is a perspective view showing a schematic configuration of a distance measuring device to which the optical scanning device of the present embodiment is applied. 4A is a top view of the distance measuring device shown in FIG. 3 as viewed from above. FIG. 4B is a side view of the distance measuring device shown in FIG. 3 viewed from the side. As described above, in the present embodiment, the scanning optical system constituted by the scanning mechanism and the shared optical system is also used as a light receiving optical system for receiving reflected light.

First, the part which comprises an optical scanning device (light output part) is demonstrated.
As shown in FIG. 3, the distance measuring device 10 includes a laser light source 16, a first scanning unit 40, a reflecting mirror 42, and a second scanning unit 44. The first scanning unit 40 has a first reflecting surface 40A that rotates around the first rotation axis 40B. The first scanning unit 40 rotates the first reflecting surface 40A to reflect and scan the light incident on the first reflecting surface 40A from the laser light source 16. In the present embodiment, the first rotating shaft 40B is parallel to the vertical direction, and the light incident from the laser light source 16 is scanned in a substantially horizontal direction.

  Although not shown, the light emitted from the laser light source 16 is converted into parallel light by a lens disposed close to the laser light source 16. In the following description, the lens is omitted, and the light emitted from the laser light source 16 is assumed to be parallel light.

  The reflecting mirror 42 has a curved belt-like reflecting surface 42A that forms a part of a spheroid. The detailed shape of the reflecting mirror 42 will be described later. The curved belt-like reflecting surface 42A is arranged so as to extend in the optical scanning direction (horizontal direction) of the first scanning unit 40. The light incident from the first scanning unit 40 is reflected in the direction of the second scanning unit 44 by the reflecting surface 42A.

  The second scanning unit 44 has a second reflecting surface 44A that rotates around the second rotation axis 44B. The second scanning unit 44 rotates the second reflecting surface 44A to reflect and scan the light incident on the second reflecting surface 44A from the reflecting mirror 42. In the present embodiment, the second rotating shaft 44B is parallel to the horizontal direction, and the light incident from the reflecting mirror 42 is scanned in the substantially vertical direction. Thus, the irradiation light 30 for performing two-dimensional scanning is emitted from the second scanning unit 44.

  A correction optical system 46 such as a correction lens may be disposed on the light incident side of the first scanning unit 40. The correction optical system 46 has a function of converging light incident on the first scanning unit 40 so that light emitted from the second scanning unit 44 becomes parallel light. By disposing the correction optical system 46, the spread of the irradiation light 30 for performing two-dimensional scanning is suppressed, and the parallelism of the irradiation light 30 is not lowered. Therefore, the correction optical system 46 may be omitted when spreading of the irradiation light 30 is allowed or when the irradiation light 30 is convergent light.

  When the correction optical system 46 is arranged, the parallel light emitted from the laser light source 16 is converted into convergent light by the correction optical system 46. The convergent light is scanned in the horizontal direction by the first scanning unit 40. The light reflected by the first scanning unit 40 is once condensed between the first scanning unit 40 and the reflecting mirror 42, then spread and irradiated on the reflecting mirror 42. The light reflected by the reflecting mirror 42 becomes parallel light and is guided to the second scanning unit 44. Thereby, the irradiation light 30 emitted from the second scanning unit 44 also becomes parallel light.

Next, the part which comprises a photon detection part is demonstrated.
The distance measuring apparatus 10 includes a second scanning unit 44, a reflecting mirror 42, a first scanning unit 40, a condensing optical system 48, and a photodetector 24 as light detection units. The second scanning unit 44, the reflecting mirror 42, and the first scanning unit 40 are shared with the optical scanning device (light output unit). The incident reflected light 32 is reflected by the second scanning unit 44 in the direction of the reflecting mirror 42, reflected by the reflecting mirror 42 in the direction of the first scanning unit 40, and by the first scanning unit 40 of the condensing optical system 48. Reflected in the direction.

  The condensing optical system 48 is disposed on the light emission side of the first scanning unit 40. The condensing optical system 48 includes a concave mirror having a concave reflecting surface, and reflects and condenses the incident reflected light 32 to form an image on the imaging surface of the photodetector 24. The condensing optical system 48 is provided with an opening 48A. The light emitted from the laser light source 16 passes through the opening 48A and is irradiated on the first scanning unit 40.

  As shown, the reflected light 32 is a beam thicker than the irradiation light 30. In a distance measuring device such as a laser radar device, the received light signal intensity is proportional to the size of the effective aperture area on the light receiving side, so that an optical system capable of handling a thick beam is required. As described above, when the correction optical system 46 is arranged, it is easy to handle the reflected light 32 that is a thick beam.

  In the present embodiment, as shown in FIGS. 4A and 4B, when the surface on which the reflecting mirror 42 is disposed is a reference surface, the first scanning unit 40 is disposed substantially in the reference surface. The laser light source 16, the condensing optical system 48, the photodetector 24, and the correction optical system 46 are disposed above the reference plane. The second scanning unit 44 is disposed below the reference plane. As will be described later, the first scanning unit 40 and the second scanning unit 44 are arranged at different heights on the rotation center axis of the spheroid. The first scanning unit 40 is disposed above the second scanning unit 44.

  Light incident on the first scanning unit 40 from above from the laser light source 16 is reflected in the horizontal direction and applied to the reflecting mirror 42. The light reflected downward by the reflecting mirror 42 enters the second scanning unit 44 from above. The light incident on the second scanning unit 44 from above is reflected in the horizontal direction and emitted as irradiation light 30. The horizontal cross section of the reflection surface 42A of the spheroidal surface is a circle, and the light emitted from the first scanning unit 40 disposed at the center (rotation center) of the circle is reflected by the reflection surface 42A and again becomes a circle. Return to the center (center of rotation).

Here, the detailed shape of the reflecting mirror 42 will be described.
FIG. 5A is a schematic diagram showing the shape of a reflecting mirror whose reflecting surface forms part of a spheroid. As shown in FIG. 5A, the reflecting mirror 42 has a curved strip-like reflecting surface 42A that forms a part of a spheroid 54 obtained by rotating an ellipse 52 around a rotation center axis 50. The reflecting surface 42A is cut out from the spheroid 54 with a predetermined width in the direction in which the rotation center axis 50 of the spheroid 54 extends.

  Since the belt-like reflecting surface 42A is arranged so as to extend in the horizontal direction, the vertical width becomes a predetermined width. The width in the vertical direction is determined in advance according to the thickness of the beam of the reflected light 32 to be received, the spread of the beam reflected by the first scanning unit 40, the size of the optical system and apparatus, and the like. The horizontal cross section of the spheroid 54 is a circle, and the curvature of the reflecting surface 42A is constant in the horizontal direction. On the other hand, the vertical cross section of the spheroid 54 is an ellipse, and the curvature of the reflecting surface 42A changes in the vertical direction.

The positional relationship among the reflecting mirror, the first scanning unit, and the second scanning unit will be described.
FIG. 5B is a schematic diagram illustrating a positional relationship among the reflecting mirror, the first scanning unit, and the second scanning unit illustrated in FIG. The position where the first scanning unit 40 is disposed is referred to as a “first position 56”, and the position where the second scanning unit 44 is disposed is referred to as a “second position 58”. The ellipse 52 constituting the spheroid 54 has two focal positions on the rotation center axis 50. In the present embodiment, the “first position 56” is set as one focal position, and the first scanning unit 40 is arranged at one focal position. In addition, with the “second position 58” as the other focal position, the second scanning unit 44 is disposed at the other focal position.

  As described above, the horizontal cross section of the spheroid 54 is a circle, and the curvature of the reflecting surface 42A is constant in the horizontal direction. On the other hand, the vertical cross section of the spheroid 54 is an ellipse, and the curvature of the reflecting surface 42A changes in the vertical direction. The ellipse 52 constituting the spheroid 54 has two focal positions on the rotation center axis 50.

  The light emitted from one focal position of the ellipse 52 is reflected by the reflecting surface which is the spheroid 54 and is condensed at the other focal position. By using the reflection mirror 42 described above, even if the first scanning unit 40 disposed at one focal position scans in the horizontal direction at a wide angle, the scanned light is reflected by the reflection mirror 42 and the other focal point. The light is condensed in a narrow range around the second scanning unit 44 arranged at the position. Therefore, the second scanning unit 44 is reduced in size as compared with the conventional scanning optical system including the reflecting mirror, the first scanning unit, and the second scanning unit.

  Further, the light incident on the first scanning unit 40 is scanned in the horizontal direction. The horizontal cross section of the spheroid 54 is a circle, and the curvature of the reflecting surface 42A is constant in the horizontal direction. That is, even if the horizontal scanning angle by the first scanning unit 40 changes, the curvature of the reflecting surface 42A does not change. Therefore, wide-angle two-dimensional scanning is performed while maintaining parallelism.

  Note that if the curvature of the reflecting surface 42A changes, for example, by scanning the light incident on the first scanning unit 40 over a wide range in the vertical direction, aberrations (of the imaging position) are formed when the irradiation light 30 is scanned. Shift). This is because the lens action received by the light incident on the first scanning unit 40 changes. In the present embodiment, the light incident on the first scanning unit 40 is scanned in the horizontal direction where the curvature of the reflection surface 42A is constant, so that the aberration is suppressed as compared with the case where the curvature of the reflection surface 42A changes. The

  Further, as the reflecting mirror 42, a reflecting mirror whose reflecting surface forms a part of a spherical surface may be used. FIG. 5C is a schematic diagram showing the positional relationship between the reflecting mirror whose reflecting surface forms part of a spherical surface, the first scanning unit, and the second scanning unit. As shown in FIG. 5C, the reflecting mirror 42 has a curved strip-shaped reflecting surface 42 </ b> A that forms a part of a spherical surface 62 obtained by rotating a circle 60 around the rotation center axis 50.

  The cross section of the spherical surface 62 in the horizontal direction is a circle, and the curvature of the reflecting surface 42A does not change even if the scanning angle by the first scanning unit 40 changes. The vertical cross section of the spherical surface 62 is also a circle, and the curvature of the reflecting surface 42A does not change even if the light reflected by the first scanning unit 40 spreads in the vertical direction. Therefore, even when the light incident on the first scanning unit 40 is scanned over a wide vertical range, the curvature of the reflecting surface 42A is constant, and wide-angle two-dimensional scanning is performed while maintaining a high degree of parallelism. Done.

  However, in the reflecting mirror 42 in which the reflecting surface forms a part of the spherical surface 62, light emitted from a specific position on the rotation center axis 50 is reflected by the reflecting surface which is the spherical surface 62, and is different on the rotation center axis 50. It does not have the property of condensing at the position. For this reason, the condensing position of the light reflected by the reflecting mirror 42 varies. In this case, the second scanning unit 44 may be enlarged to such an extent that scattered reflected light is incident.

<Improvement of scanning trajectory>
Next, a method for improving the scanning locus will be described.
4A and 4B are diagrams showing a state before scanning is started, and illustrates a case where the first scanning unit 40 is at the reference position. When the first scanning unit 40 is at the reference position, light is reflected in the direction of 0 ° from the front front in the horizontal direction. On the other hand, FIGS. 6A and 6B are diagrams showing a horizontal scanning operation in the distance measuring apparatus shown in FIG. FIG. 6A is a top view and FIG. 6B is a side view.

  As shown in FIGS. 6A and 6B, when scanning is started, the first scanning unit 40 rotates around the first rotation axis 40B from the reference position and is incident on the first reflecting surface 40A. The light is reflected in the direction according to the rotation angle. In the illustrated example, light is reflected in a direction of 60 ° from the front front in the horizontal direction. Even if the reflection direction of light by the first reflecting surface 40A changes, as described above, the light emitted from the first scanning unit 40 arranged at the center (rotation center) of the circle is reflected by the reflecting surface 42A. Returning again to the center (rotation center) of the circle, the second reflecting surface 44A of the second scanning unit 44 is irradiated.

  On the other hand, in the illustrated example, the second scanning unit 44 is not rotated around the second rotation axis 44B. However, the emission angle of the irradiation light 30 in the vertical direction changes so as to face downward from the horizontal direction. FIG. 7 is a graph showing a scanning locus when the second scanning unit is fixedly arranged. In the illustrated example, the second scanning unit 44 is pre-rotated and fixedly arranged so that light is reflected in directions of 0 °, 15 °, 30 °, and 45 ° from the horizontal direction in the vertical direction. The scanning trajectory when 40 is rotated is shown. The reference position of the second scanning unit 44 is an arrangement in which light is reflected in a direction of 0 ° from the horizontal direction in the vertical direction (that is, the horizontal direction).

  As shown in FIG. 7, even if the second scanning unit 44 is fixedly arranged at any rotation angle, the scanning trajectory does not become a straight line extending in the horizontal direction, but is an upwardly convex curve (rotation angle 0 ° = reference position). A downwardly convex curve (rotation angles of 15 ° and 30 °), an obliquely extending straight line (rotation angle of 45 °) and the like. That is, in any case, it can be seen that the horizontal plane is not scanned. The scanning trajectory can be improved by rotating the second scanning unit 44 in conjunction with the rotation of the first scanning unit 40. However, in order to link the two scanning units, it is necessary to add a drive mechanism and a control procedure.

  Japanese Patent Application Laid-Open No. 2011-197575 discloses a method for flexibly setting a scanning trajectory of an optical scanning device. In the technique described in the publication, on the premise of a single scanning unit (a rotating reflector having a reflecting surface inclined with respect to the rotation axis), the scanning locus is formed by inclining the angle of the rotation axis of the rotating reflector as the scanning unit. It is improved. The scanning optical system according to the present embodiment is a scanning optical system including a first scanning unit 40, a reflecting mirror 42, and a second scanning unit 44, and the underlying configuration is different. However, it has been found that applying this method to the first scanning unit 40 improves the scanning trajectory of the optical scanning device.

  FIG. 8 is a side view showing the scanning locus improving operation of the distance measuring apparatus shown in FIG. As shown in FIG. 8, the first scanning unit 40 is constituted by a rotating reflector having a first reflecting surface 40A inclined with respect to the rotating shaft 40B, and the first rotating shaft 40B of the rotating reflector is inclined with respect to the reference direction. Inclined at an angle φ. The structure of the rotating reflector will be described later. Here, the “reference direction” is a direction in which the rotation center axis of the reflecting mirror 42 (reflecting surface 42A) extends, and is a vertical direction.

  It is assumed that light from the light source is incident on the first reflecting surface 40A at an incident angle θ and the second reflecting surface 44A of the second scanning unit 44 is fixedly arranged. Then, when the inclination angle φ ≠ 0 ° of the first rotation shaft 40B, the deviation of the light emitted from the second scanning unit 44 with respect to the light scanning direction of the first scanning unit 40 is the inclination angle φ of the first rotation shaft 40B. The inclination angle φ is determined in advance according to the incident angle θ so that the light emitted from the second scanning unit 44 becomes smaller than the deviation of the light emitted from the second scanning unit 44 with respect to the optical scanning direction of the first scanning unit 40 when = 0 °. Here, the “optical scanning direction of the first scanning unit 40” is the horizontal direction.

Here, the structure of the rotating reflector will be described.
FIG. 9A is a schematic diagram illustrating an example of the configuration of the first scanning unit. FIG. 9B is a schematic diagram showing the inclination angle φ of the rotation axis of the first scanning unit having the first reflecting surface. As shown in FIG. 9A, the first scanning unit 40 includes a first reflecting surface 40A that obliquely intersects the first rotation axis 40B, and is configured to be rotatable around the first rotation axis 40B. A rotating reflector such as a mirror.

  For example, as shown in the figure, it may have a cylindrical shape that can rotate around the first rotation shaft 40B. The cylinder is cut obliquely with respect to the first rotation shaft 40B to form a cut surface. The cut surface may be coated with a highly reflective material to form the first reflective surface 40A with a diagonal line. Moreover, it is good also as a structure which supports a disk-shaped plane mirror with a support | pillar.

As shown in FIG. 9B, the first rotation shaft 40B of the first scanning unit 40 is inclined by an inclination angle φ with respect to the vertical direction. The laser light source 16 is disposed obliquely above the first scanning unit 40. The laser light source 16 irradiates the first reflecting surface 40A with laser light (incident light i ₁ ) at a predetermined incident angle θ ₁ obliquely from above. The incident light i ₁ is reflected by the first reflecting surface 40A, and reflected light (emitted light o ₁ ) is emitted. As the first scanning unit 40 rotates around the first rotation axis 40B, the reflected light (emitted light o ₁ ) is scanned in the horizontal direction.

FIG. 9C is an explanatory diagram for explaining the principle of improving the scanning locus by the light reflected by the second reflecting surface of the second scanning unit. As shown in FIG. 9C, the laser light (incident light i ₁ ) from the laser light source 16 is incident on the first reflecting surface 40A of the first scanning unit 40 at an incident angle θ ₁ and the first reflecting surface. Reflected by 40A, reflected light (emitted light o ₁ ) is emitted. The laser light (emitted light o ₁ ) emitted from the first reflecting surface 40A is reflected by the reflecting surface 42A of the reflecting mirror 42 and is incident on the second reflecting surface 44A of the second scanning unit 44 at an incident angle θ ₂ . Is done. The laser light (incident light i ₂ ) from the reflective surface 42A is incident on the second reflective surface 44A of the second scanning unit 44 at an incident angle θ ₂ , reflected by the second reflective surface 44A, and reflected light (outgoing light). Irradiation o ₂ ) is emitted as “irradiation light”.

In the present embodiment, the deviation of the irradiation light (emitted light o ₂ ) emitted from the second scanning unit 44 with respect to the horizontal direction when the tilt angle φ ≠ 0 ° is the second when the tilt angle φ = 0 °. Incident light i ₁ incident on the first reflecting surface 40A of the first scanning unit 40 from the laser light source 16 so as to be smaller than the deviation of the irradiation light (emitted light o ₂ ) emitted from the scanning unit 44 with respect to the horizontal direction. depending on the angle theta _1, it should define a tilt angle φ of the first rotating shaft 40B of the first scanning unit 40 in advance.

  FIG. 10 is a graph showing an improved scanning trajectory. In the illustrated example, the second scanning unit 44 is pre-rotated and fixedly arranged so that light is reflected in directions of 0 °, 15 °, 30 °, and 45 ° from the horizontal direction in the vertical direction. The scanning trajectory when 40 is rotated is shown. Using the first scanning unit 40 shown in FIG. 9A, the first rotation shaft 40B was rotated at an inclination angle φ = 30 °.

  Then, when the second scanning unit 44 was fixedly arranged at a rotation angle of 0 °, the scanning locus could be a straight line extending in the horizontal direction. In addition, when the second scanning unit 44 was fixedly arranged at a rotation angle of 45 °, scanning was possible in a wide range along the vertical direction at a position of ± 90 ° in the horizontal direction. That is, assuming that a semi-cylindrical area below the reference position (vertical rotation angle 0 °) is a monitoring area, the entire monitoring area is scanned.

  Note that the configurations of the scanning optical system, the optical scanning device, and the distance measuring device described in the above embodiments are merely examples, and it goes without saying that the configurations may be changed without departing from the gist of the present invention. Yes.

DESCRIPTION OF SYMBOLS 10 Distance measuring device 12 Control part 14 Light source drive part 16 Laser light source 18 Shared optical system 20 Scan mechanism drive part 22 Scan mechanism 24 Photo detector 26 Light output part 28 Light detection part 30 Irradiation light 32 Reflected light 40 1st scanning part 40A First reflecting surface 40B First rotating shaft 42 Reflecting mirror 42A Reflecting surface 44 Second scanning unit 44A Second reflecting surface 44B Second rotating shaft 46 Correction optical system 48 Condensing optical system 48A Aperture 50 Rotation center axis 52 Ellipse 54 Rotation Elliptic surface 56 First position 58 Second position 60 Circle 62 Spherical surface

Claims (6)

A first scanning unit that includes a first reflecting surface, rotates the first reflecting surface around a first rotation axis, and reflects and scans light incident on the first reflecting surface from a light source;
A band-shaped reflecting surface that is cut out in a direction extending in the direction of the rotation center axis from a part of the spheroid or spherical surface and curved in a direction intersecting with the rotation center axis, the band-shaped reflection surface being A reflecting mirror arranged to extend in the light scanning direction of the first scanning unit and reflecting the light incident from the first scanning unit;
A second reflection surface, wherein the second reflection surface is rotated around a second rotation axis to reflect and scan light from the reflection mirror in a direction intersecting the light scanning direction of the first scanning unit; A scanning unit;
With
Each of the first scanning unit and the second scanning unit has a rotation center axis of the reflecting mirror so that light incident from the first scanning unit and reflected by the reflecting mirror is incident on the second scanning unit. Spaced apart above,
Scanning optical system. The reflecting mirror has a band-like reflecting surface cut out from a part of the spheroid,
The first scanning unit is disposed on the rotation center axis of the reflecting mirror and at one focal position of the ellipse, and the second scanning unit is disposed on the rotation center axis of the reflecting mirror and the other focal position of the ellipse. Placed in the
The scanning optical system according to claim 1. The first reflection surface of the first scanning unit obliquely intersects the first rotation axis, the first rotation axis is inclined at an inclination angle φ with respect to the rotation center axis of the reflection mirror, and the first reflection surface When light from the light source is incident at an incident angle θ and the second reflecting surface of the second scanning unit is fixedly arranged,
The deviation of the light emitted from the second scanning unit with respect to the light scanning direction of the first scanning unit when the tilting angle φ ≠ 0 ° of the first rotating shaft is the tilt angle φ of the first rotating shaft. The inclination angle φ is predetermined according to the incident angle θ so that the light emitted from the second scanning unit becomes smaller than the deviation of the light from the first scanning unit with respect to the optical scanning direction when 0 °. ,
The scanning optical system according to claim 1 or 2.   Further, a correction optical system for converging the light incident on the first scanning unit is disposed on the light incident side of the first scanning unit so that the light emitted from the second scanning unit becomes parallel light. The scanning optical system according to any one of claims 1 to 3. A light source that emits light;
A scanning optical system according to any one of claims 1 to 4,
An optical scanning device comprising: A light output unit comprising the optical scanning device according to claim 5 and outputting irradiation light for scanning a predetermined monitoring area;
A light detection unit for detecting reflected light from an obstacle in the monitoring area;
A distance calculation unit that calculates a distance to the obstacle based on a delay time of the reflected light output from the light output unit and detected by the light detection unit;
Distance measuring device with

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