JP2015129678A - Scanning optical system, optical scanning device, and ranging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rotation of a reflection beam image on a photosensitive element without having to increase the number of parts.SOLUTION: A scanning optical system 18 includes: a projection mirror 24 which rotates about a predefined rotation axis X and reflects a light beam emitted from a laser light source 16 in a predefined direction L1 to project the light beam to an object in the predefined direction L1; and a light-receiving mirror 28 which is mounted such that a reflective surface thereof faces an inverted direction relative to a reflective surface of the projection mirror 24, rotates together with the projection mirror 24 about the rotation axis X, and receives a reflection beam of the light beam projected onto the object by the projection mirror 24. A light-reflective surface of at least one of the projection mirror 24 and light-receiving mirror 28 has orthogonal mirror surfaces that invert an image.

Description

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

  Conventionally, a light projecting / receiving optical system that projects light onto an object for distance measurement and receives light reflected from the object is separated into a light projecting optical system and a light receiving optical system, and the optical axis of the light projecting optical system A distance measuring device having a structure in which the optical axes of the light receiving optical systems are adjacent to each other has been proposed (see, for example, Patent Documents 1 and 2). The reason why the optical axes of the light projecting optical system and the light receiving optical system are arranged adjacent to each other is to enable detection of an object at a short distance for the following two reasons.

  First, the first reason is that if the scattered light inside the distance measuring device enters the light receiving element, the signal and the reflected light from the object at a short distance overlap, making it impossible to detect a near object. It is.

  The second reason is that when the optical axes of the light projecting optical system and the light receiving optical system are separated from each other, the reflection point of the object at a short distance deviates from the light receiving field.

  For example, the device described in Patent Document 1 has a structure that is folded back by a mirror on the back of the device in order to make the light receiving optical system more compact.

  In addition, as in the device described in Patent Document 2, when it is intended to detect an object at a short distance, it is appropriate to place the projection mirror for light projection and the scan mirror for light reception upside down. There is a problem that the projected image rotates on the light receiving element with scanning.

  This problem will be described with reference to FIG. As shown in FIG. 11, the light projecting mirror 100 and the light receiving mirror 102 rotate in the arrow B direction together with the arrow A direction as the rotation axis.

  The light projecting mirror 100 projects a light beam L1 emitted from a laser light source (not shown) in the direction of arrow A in the direction of arrow C1 perpendicular to the direction of arrow A, thereby projecting the light toward the target. On the other hand, the light receiving mirror 102 is arranged at a position where the light projecting mirror 100 is turned upside down in FIG. 11, and reflects the reflected beam L2 reflected from the object in the arrow C2 direction in the arrow A direction.

  Since the high-power laser light source has an elongated light emitting region, when the laser light emitted from the high-power laser light source is collimated as it is, the projection beam L1 also has an elongated beam shape as shown in FIG. Therefore, the beam shape of the reflected beam L2 reflected by the object on the light receiving element is also elongated.

  FIG. 12 shows a state in which the light projecting mirror 100 and the light receiving mirror 102 are further rotated in the arrow B direction from the state of FIG. As shown in FIG. 12, the longitudinal direction of the projection beam L <b> 1 rotates with the rotation of the projection mirror 100. The longitudinal direction of the reflected beam L2 reflected by the object is further rotated by the light receiving mirror 102, and is 2 with respect to the rotation angle θ of the light projecting mirror 100 and the light receiving mirror 102 on the light receiving element as shown in FIG. It rotates at a double rotation angle 2θ.

  Thus, since the reflected beam L2 rotates on the light receiving element, a large light receiving element having a diameter equal to or larger than the length of the major axis of the reflected beam L2 is required when all the light is to be received. However, when the size of the light receiving element increases, there is a problem that response speed and noise increase. For this reason, conventionally, the beam shape of the projection beam L1 is shaped by a complicated optical system such as a rectangular shape or a circular shape having the same vertical and horizontal lengths, or a low-power laser light source with a narrow width is used. It was necessary to use it.

  By using a structure in which the received reflected beam is folded back by a mirror on the back of the apparatus as in the apparatus described in Patent Document 1, the rotation of the image on the light receiving element of the reflected beam can be reduced.

  However, in the apparatus described in Patent Document 1, since the tilt angle of the light receiving mirror is not the same as that of the light projecting mirror, it is difficult to completely cancel the rotation. It is also physically difficult to make the inclination angle of the light receiving mirror the same as that of the light projecting mirror.

  Patent Document 3 proposes an apparatus that can reduce the rotation of an image of a reflected beam on a light receiving element by using a Dove prism.

JP 2011-257221 A Japanese Patent No. 4032061 Japanese Patent Laid-Open No. 9-21872

  However, the apparatus described in Patent Document 3 has a problem that the number of parts increases and the Dove prism needs to be rotated at half the speed of the scanning mirror, which complicates the apparatus configuration.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a scanning optical system and a light which can prevent the image of the reflected beam from rotating on the light receiving element without increasing the number of components. A scanning device and a distance measuring device are provided.

  In order to achieve the above object, the scanning optical system according to the first aspect of the present invention rotates around a predetermined rotation axis and reflects the light beam emitted from the light source in a predetermined direction. A light projecting mirror that projects light toward an object in a predetermined direction, and a light reflecting surface are installed in a direction in which the light reflecting surface of the light projecting mirror is inverted with respect to a surface perpendicular to the rotation axis; And a light receiving mirror that rotates with the light projecting mirror about the rotation axis and receives a reflected beam with respect to the light beam projected onto the object by the light projecting mirror, the light projecting mirror, and At least one light reflecting surface of the light receiving mirror has a right-angle mirror surface for inverting the image of the light beam.

  In addition, as described in claim 2, at least one light reflecting surface of the light projecting mirror and the light receiving mirror may have a plurality of the right-angle mirror surfaces.

  According to a third aspect of the present invention, a plurality of right-angle mirror reflecting surfaces having the right-angle mirror surface are disposed along a peripheral edge of at least one light reflecting surface of the light projecting mirror and the light receiving mirror, and the light projecting mirror. The angle formed by a reference line connecting the center of the light source and the position where the light beam is irradiated from the light source and a line connecting the center of the projection mirror and the center of the right-angle mirror reflecting surface is defined as θ. A configuration in which the right-angle mirror surface is formed such that an angle formed by an axial direction of the mirror reflection surface and a direction passing through the center of the right-angle mirror reflection surface and parallel to the reference line is θ / 2. It is good.

  Further, as described in claim 4, the shape of the light beam emitted from the light source may be an elongated shape.

  5. The optical scanning device according to claim 5, wherein the light source that emits the light beam and the light beam emitted from the light source are scanned to a predetermined monitoring region. A scanning optical system; and a photodetector that detects reflected light from an object existing in the monitoring region.

  According to a sixth aspect of the present invention, there is provided the distance measuring device according to the fifth aspect, and the object based on the time from when the light beam is output from the light source until the light detecting unit detects the light beam. A distance calculation unit that calculates a distance to

  According to the present invention, it is possible to prevent the image of the reflected beam on the light receiving element from rotating without increasing the number of components.

It is a block diagram which shows the structure of the control system of a distance measuring device. It is a block diagram of an optical scanning device. It is a perspective view of the light projection mirror which concerns on 1st Embodiment. It is sectional drawing of the light projection mirror which concerns on 1st Embodiment. It is a figure for demonstrating the image by reflection of a plane mirror. It is a figure for demonstrating inversion of the image by reflection of a right-angle mirror surface. It is a figure for demonstrating inversion of the projection beam by a projection mirror. It is a top view of the light projection mirror which concerns on 2nd Embodiment. It is a top view of the light projection mirror which concerns on 2nd Embodiment. It is a top view of the light projection mirror which concerns on 2nd Embodiment. It is a figure for demonstrating the image reflected by the conventional light projection mirror. It is a figure for demonstrating the image reflected by the conventional light projection mirror.

(First embodiment)

  Hereinafter, the distance measuring device according to the first embodiment will be described. FIG. 1 is a configuration diagram of a distance measuring device 10 according to the present embodiment. As shown in FIG. 1, the distance measuring device 10 includes an optical scanning device 12 and a control unit 14.

  In response to an instruction from the control unit 14, the optical scanning device 12 emits a light projection beam L1 that scans a predetermined monitoring area, and receives a reflected beam L2 from the object F existing in the monitoring area.

  In the present embodiment, a case will be described in which the distance measuring device 10 is a laser radar device that measures the distance to the object F by scanning with laser light as an example.

  The optical scanning device 12 includes a laser light source 16, a scanning optical system 18, and a photodetector 20.

  The control unit 14 is configured as a computer including a CPU, a ROM, a RAM, and an input / output unit (I / O). The control unit 14 controls the laser light source 16, the scanning optical system 18, and the photodetector 20 to project the light projection beam L 1 toward the monitoring region, receive the reflected beam L 2, and generate the light projection beam L 1. The distance to the object F is calculated based on the delay time from when the light is received until the photodetector 20 receives the reflected beam L2.

  FIG. 2 is a configuration diagram of the scanning optical system 18. As shown in FIG. 2, the scanning optical system 18 includes a collimating lens 22, a light projecting mirror 24, a rotation motor 26, a light receiving mirror 28, and a light receiving lens 30.

  The laser light source 16 includes, for example, a semiconductor laser, and emits laser light in response to an instruction from the control unit 14. In the present embodiment, the case where the laser light source is configured to include a high-power semiconductor laser as an example and the beam shape of the emitted laser light is an elongated shape will be described.

  The collimating lens 22 converts the laser light emitted from the laser light source 16 into parallel light.

  The light projection mirror 24 is attached to the support portion 32 at an angle inclined by 45 ° (135 °) as an example with respect to the arrow A direction (vertical direction) that is the emission direction of the emitted light from the laser light source 16. The part 32 is attached to the rotary motor 26. The light receiving mirror 28 is attached to the support part 34 at an angle of 135 ° (45 °) as an example with respect to the arrow A direction, and the support part 34 is attached to the rotary motor 26.

  Thus, the light receiving mirror 28 is disposed at a position where the light projecting mirror 24 is vertically inverted in FIG. That is, the light receiving mirror 28 is installed in a direction in which the light projecting mirror 24 is inverted with respect to a plane perpendicular to the rotation axis X of the rotary motor 26. The light projecting mirror 24 and the light receiving mirror 28 have a disc shape, and the diameter of the light projecting mirror 24 is smaller than the diameter of the light receiving mirror 28 as shown in FIG.

  The rotation motor 26 is rotationally driven by an instruction from the control unit 14, and the light projecting mirror 24 and the light receiving mirror 28 rotate together around the rotation axis X as the rotation motor 26 rotates.

  The light projecting mirror 24 reflects the light projecting beam L1 emitted from the laser light source 16 in the direction of arrow A in the direction of arrow B1 orthogonal to the direction of arrow A, thereby projecting light toward the monitoring region.

  The light receiving mirror 28 reflects the reflected beam L2 reflected in the arrow B2 direction orthogonal to the arrow A direction in the arrow A direction by the projected beam L1 projected on the object F in the monitoring area. . The reflected beam L 2 reflected by the light receiving mirror 28 in the direction of arrow A is imaged on the photodetector 20 by the light receiving lens 30.

  3 is a perspective view of the light projecting mirror 24, and FIG. 4 is a cross-sectional view of the light projecting mirror 24. As shown in FIGS. 3 and 4, a plurality of grooves having the same depth are formed along the same direction on the light reflecting surface of the light receiving mirror 28, and each groove intersects the roof surface, that is, at a right angle. This is a right-angle mirror surface 24A composed of two surfaces.

  Here, the phenomenon that the light reflected by the right-angle mirror surface 24A is inverted will be described. For example, as shown in FIG. 5, an image 40 of light incident on a prism 38 having a flat light reflecting surface 36 is reflected only once by the light reflecting surface 36 having a flat surface. For this reason, the left and right sides of the image 42 of the light emitted from the prism 38 are not reversed.

  On the other hand, as shown in FIG. 6, an image 48 of light incident on the prism 46 whose light reflecting surface 44 is a right-angle mirror surface is reflected twice by two orthogonal surfaces constituting the right-angle mirror surface. For this reason, the image 50 of the light emitted from the prism 46 is an inverted image.

  The emitted light emitted from the laser light source 16 is collimated by the collimating lens 22 and irradiated onto the light projecting mirror 24. The light reflecting surface of the light projecting mirror 24 has a configuration in which a plurality of right angle mirror surfaces 24A are formed. ing. For this reason, as shown in FIG. 7, the light projection beam L1 irradiated to the light projection mirror 24 is inverted in the direction of the arrow D and reflected toward the object F in the monitoring region. That is, the light projection beam L1 rotates in the opposite direction as compared with the case where the light projection mirror 24 is a plane mirror.

  The projected light beam L1 whose image is inverted is irradiated onto the object F, and the reflected beam L2 is reflected by the light receiving mirror 28 toward the photodetector 20 and forms an image on the photodetector 20.

  As described above, since the projection beam L1 rotates in the opposite direction as compared with the case where the projection mirror 24 is a plane mirror, the image on the photodetector 20 is projected as shown in FIG. It does not change with the rotation of the mirror 24 and the light receiving mirror 28, and is in the same direction as the light projection beam L1 emitted from the laser light source 16. For this reason, the size of the photodetector 20 does not need to be a size having a diameter equal to or larger than the major axis of the projection beam L1, and is efficient by using a photodetector having an elongated shape like the beam shape of the projection beam L1. The reflected beam L2 can be detected well. This can prevent response speed and noise from increasing.

  Further, since the shape of the light projection beam L1 can be elongated, the monitoring area in the direction (vertical direction) orthogonal to the scanning direction of the light projection beam L1 can be expanded. Further, by using a light receiving element array for the photodetector 20 and disassembling and receiving a vertically long image, a plurality of points can be measured at a time.

  In the present embodiment, the case where a plurality of right-angle mirror surfaces 24A are provided on the light reflecting surface of the light projecting mirror 24 has been described. However, the light projecting mirror 24 is a plane mirror, and a plurality of light reflecting surfaces of the light receiving mirror 28 are provided on the light reflecting surface. It is good also as a structure provided with the right-angle mirror surface.

  Further, in the present embodiment, the case where a plurality of right-angle mirror surfaces 24A are provided on the light reflection surface of the light projection mirror 24 has been described, but the number of right-angle mirror surfaces 24A is not limited to a plurality and may be one. The smaller the right-angle mirror surface 24A, the less the loss of light, so that deterioration of measurement accuracy can be suppressed. However, in order to reduce the number of right-angle mirror surfaces 24A without changing the size of the light projection beam L1, the grooves formed by the right-angle mirror surfaces 24A must be deepened, so the size of the light projection mirror 24 is large. Become. Therefore, when it is desired to reduce the size of the projection mirror 24, it is better to provide a large number of right-angle mirror surfaces 24A with small grooves.

  (Second Embodiment)

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same part as 1st Embodiment, and the detailed description is abbreviate | omitted.

  Since the distance measuring device 10 described in the first embodiment has a structure in which the light reflecting surface of the light projecting mirror 24 includes a right angle mirror surface 24A, the image of the reflected beam L2 rotates on the photodetector 20. Can be prevented.

  However, there is no change in that the light projection beam L1 rotates according to the scanning direction. For example, the position of the light projecting mirror 24 when the light projecting beam L <b> 1 having an elongated beam shape is reflected by the light projecting mirror 24 in the vertically long shape in the vertical direction is defined as the front surface of the light projecting mirror 24. When the light projection mirror 24 is rotated by + 90 ° or −90 ° from this state, the beam shape of the light projection beam L1 reflected by the light projection mirror 24 becomes a horizontally long shape in the horizontal direction. For this reason, in the state where the light projection mirror 24 is rotated + 90 ° or −90 ° from the front, the monitoring region in the height direction (vertical direction) becomes narrow.

  Therefore, in the present embodiment, a distance measuring device capable of scanning the projection beam L1 while maintaining a vertically long beam shape in the vertical direction regardless of the rotation angle of the projection mirror 24 will be described.

  In FIG. 8, the top view of the light projection mirror 24B which concerns on this embodiment was shown. Since the configuration other than the light projection mirror 24B is the same as that of the first embodiment, detailed description thereof is omitted.

  As shown in FIG. 8, the projection mirror 24B includes a plurality of right-angle mirror reflecting surfaces 24C having a plurality of right-angle mirror surfaces similar to those described in the first embodiment, along the periphery of the projection mirror 24B. ing. The laser light source 16 is provided above the paper surface of FIG. 8 at a predetermined position P on the periphery of the light projection mirror 24B, and irradiates the position P with a vertically long light projection beam L1 in FIG. The vertically long projection beam L1 irradiated to the projection mirror 24B is sequentially reflected by a plurality of right-angle mirror reflecting surfaces 24C provided on the periphery of the projection mirror 24B as the projection mirror 24B rotates.

  Here, as shown in FIG. 8, a reference line 60 connecting the center H1 of the projection mirror 24B and the position P irradiated with the projection beam L1 from the laser light source 16, and the center H1 of the projection mirror 24B and a right angle mirror. Assuming that the angle formed by the line 62 connecting the center H2 of the reflecting surface 24C and θ is θ, the right-angle mirror reflecting surface 24C has an axial direction of the right-angle mirror reflecting surface 24C (the extending direction of the groove formed by the right-angle mirror surface). A plurality of right angle mirror surfaces (grooves) are formed such that an angle α formed by 64 and a direction 66 passing through the center H2 and parallel to the reference line 60 is θ / 2.

  As shown in FIG. 9, when the axial direction of the right-angle mirror reflecting surface 24C at the position P where the projection beam L1 is irradiated is the same direction as the extending direction of the reference line 60, the light is reflected by the right-angle mirror reflecting surface 24C at the position P. The light projection beam L1 is a vertically long beam that is long in the direction perpendicular to the paper surface of FIG.

  Then, the projection mirror 24B rotates from the state of FIG. 9, and the axial direction of the right-angle mirror reflecting surface 24C at the position P where the projection beam L1 is irradiated is different from the extending direction of the reference line 60, as shown in FIG. Even in the direction, the light projecting beam L1 irradiated to the right-angle mirror reflecting surface 24C at the position P is inverted and reflected, so that the light projecting beam L1 is also perpendicular to the paper surface of FIG. Long vertical beam.

  As described above, the reference line 60 that connects the center H1 of the projection mirror 24B and the position P irradiated with the projection beam L1 from the laser light source 16, the center H1 of the projection mirror 24B, and the center H2 of the right-angle mirror reflecting surface 24C. The angle α formed by the axis 62 of the right-angle mirror reflecting surface 24C and the direction 66 passing through the center H2 and parallel to the reference line 60 is θ / 2, where θ is the angle formed by the line 62 connecting the two. As described above, a plurality of right-angle mirror reflecting surfaces 24 </ b> C having a plurality of right-angle mirror surfaces are provided on the periphery of the light projection mirror 24.

  Therefore, even when the projection mirror 24B is rotated to scan the projection beam L1, the projection beam L1 is inverted in an appropriate direction by the right-angle mirror reflecting surface 24C, so that the vertical direction is maintained. In this state, the projection beam L1 can be irradiated to the monitoring area.

  As shown in FIG. 8, the right-angle mirror reflecting surface 24C may be arranged discretely to some extent, but the light projection beam L1 reflected by a portion other than the discretely arranged right-angle mirror reflecting surface 24C. Therefore, it is preferable to provide the right-angle mirror reflecting surface 24C so that the axial direction changes continuously as much as possible. Thereby, even when the measurement points are continuous, it is possible to irradiate the projection beam L1 maintaining the vertical direction, and therefore it is possible to measure with high accuracy.

  Further, when the projection beam L1 is irradiated so as to maintain a vertically long beam in the vertical direction, the image is rotated on the photodetector 20, so that the light receiving mirror 28 and the projection mirror 24 are used to prevent this. It is good also as a mirror of the same structure. That is, a configuration may be adopted in which a plurality of light reflecting surfaces similar to the right-angle mirror reflecting surface 24 </ b> C are provided on the periphery of the light receiving mirror 28.

  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 Optical scanning device 14 Control part 16 Laser light source 18 Scanning optical system 20 Photo detector 24, 24B Light projection mirror 24 Light projection mirror 24A Right angle mirror surface 24C Light reflection surface 28 Light reception mirror 60 Reference line 64 Axial direction

Claims (6)

A projection mirror that rotates about a predetermined rotation axis and projects a light beam emitted from the light source in a predetermined direction to project toward the object in the predetermined direction;
A light reflecting surface is installed in a direction in which the light reflecting surface of the light projecting mirror is inverted with respect to a surface perpendicular to the rotation axis, and rotates with the light projecting mirror around the rotation axis, A light receiving mirror that receives a reflected beam with respect to the light beam projected onto the object by the light mirror;
With
A scanning optical system in which at least one light reflecting surface of the light projecting mirror and the light receiving mirror has a right-angle mirror surface for inverting the image of the light beam. The scanning optical system according to claim 1, wherein at least one of the light reflecting mirror and the light receiving mirror has a plurality of the right-angle mirror surfaces. A plurality of right-angle mirror reflection surfaces having the right-angle mirror surface are arranged along the periphery of the light reflection surface of at least one of the light projecting mirror and the light receiving mirror,
An angle formed by a reference line connecting the center of the projection mirror and the position where the light beam is irradiated from the light source, and a line connecting the center of the projection mirror and the center of the right-angle mirror reflecting surface is θ The right-angle mirror surface is formed such that an angle formed between the axial direction of the right-angle mirror reflection surface and the direction passing through the center of the right-angle mirror reflection surface and parallel to the reference line is θ / 2. The scanning optical system according to claim 1 or 2. The scanning optical system according to any one of claims 1 to 3, wherein a shape of a light beam emitted from the light source is an elongated shape. A light source that emits a light beam;
The scanning optical system according to any one of claims 1 to 4, wherein the light beam emitted from the light source is scanned to a predetermined monitoring region.
A photodetector for detecting reflected light from an object present in the monitoring area;
An optical scanning device comprising: An optical scanning device according to claim 5;
A distance calculation unit that calculates a distance to the object based on a time from when a light beam is output from the light source to when it is detected by the light detection unit;
Distance measuring device with

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