JP2009098129A - Beam irradiation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a beam irradiation apparatus capable of appropriately detecting a mirror turn position, by simple arithmetic processings. <P>SOLUTION: A laser beam and a servo beam are incident on a mirror 113 and a transparent member 200, respectively so that an angle direction A1 from an optical axis of the laser beam to be incident on the mirror 113 to the incidence plane of the mirror 113 and an angle direction A2, from the optical axis of the servo beam, to be incident on the transparent member 200 to the incidence plane of the transparent member 200, are mutually opposite. According to such a layout for an optical system, scan loci of the servo beam becomes closer to approach parallel. In order to further make the scan loci of the servo beam closer to approach parallel, when the mirror 113 (transparent member 200) is at a neutral position, the optical axis is made to have gradient of 45° or smaller, with respect to the incidence plane of the transparent member 200, and the servo beam is, preferably, made to be incident on the transparent member 200. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a beam irradiation apparatus that irradiates a target area with laser light, and in particular, based on reflected light when the target area is irradiated with laser light, the presence or absence of an obstacle in the target area and the distance to the obstacle. It is suitable for use in a beam irradiation device mounted on a so-called laser radar.

  In recent years, in order to improve safety during traveling, a laser radar that irradiates laser light forward in the traveling direction and detects the presence or absence of an obstacle in the target area and the distance to the obstacle from the state of the reflected light, It is installed in home passenger cars. In general, a laser radar scans a laser beam within a target area, detects the presence or absence of an obstacle at each scan position from the presence or absence of reflected light at each scan position, and further determines from the irradiation timing of the laser light at each scan position. Based on the time required to receive the reflected light, the distance to the obstacle at the scan position is detected.

  In order to increase the detection accuracy of the laser radar, it is necessary to appropriately scan the laser beam within the target area, and it is necessary to appropriately detect each scan position of the laser beam. Conventionally, as a laser beam scanning mechanism, a scanning mechanism using a polygon mirror and a lens driving type scanning mechanism for driving a scanning lens two-dimensionally (for example, see Patent Document 1 below) are known.

  As a new scanning mechanism different from these scanning mechanisms, the applicant has previously filed Japanese Patent Application No. 2006-121762 and has proposed a mirror rotation type scanning mechanism. In this scan mechanism, the mirror is supported so that it can be driven in two axes, and the mirror is rotated about each drive shaft by an electromagnetic drive force between the coil and the magnet. The laser light is incident on the mirror from an oblique direction, and the reflected light is irradiated toward the target area. The mirror is driven two-dimensionally around each drive axis, whereby the laser beam is scanned in a two-dimensional direction within the target area.

  In this scanning mechanism, the scanning position of the laser beam in the target area corresponds one-to-one with the rotational position of the mirror. Therefore, the scan position of the laser beam can be detected by detecting the rotational position of the mirror. Here, the rotation position of the mirror can be detected, for example, by detecting the rotation position of another member that rotates with the mirror.

  FIG. 13 is a diagram illustrating a configuration example for detecting the rotational position of the mirror. FIG. 5A shows a configuration example when a parallel plate-shaped transparent body is used as another member, and FIG. 4B shows a configuration example when a mirror is used as another member.

  In FIG. 6A, reference numeral 601 denotes a semiconductor laser, 602 denotes a transparent body, and 603 denotes a photodetector (PSD: Position Sensing Device). Laser light (servo light) emitted from the semiconductor laser 601 is refracted by a transparent body 602 arranged to be inclined with respect to the laser optical axis, and is received by the photodetector 603. Here, when the transparent body 602 rotates as shown by an arrow, the optical path of the servo light changes as indicated by a dotted line in the figure, and the light receiving position of the servo light on the photodetector 603 changes. Therefore, the rotational position of the transparent body 602 can be detected from the light receiving position of the servo light detected by the photodetector 603.

  In FIG. 6B, 611 is a semiconductor laser, 612 is a mirror, and 613 is a photodetector (PSD). Laser light (servo light) emitted from the semiconductor laser 611 is reflected by a mirror 612 arranged to be inclined with respect to the laser optical axis, and received by the photodetector 613. Here, when the mirror 612 rotates as shown by an arrow, the optical path of the servo light changes as indicated by a dotted line in the figure, and the light receiving position of the servo light on the photodetector 613 changes. Therefore, the rotational position of the mirror 612 can be detected from the light receiving position of the servo light detected by the photodetector 613.

Here, when the mirror 612 is rotated by an angle α as shown in FIG. 5B, the swing angle of the servo light reflected by the mirror 612 is 2α. For this reason, the light receiving surface of the photodetector 613 that receives this light is relatively large. On the other hand, when the transparent body 602 is used as shown in FIG. 5A, even if the transparent body 602 rotates, the fluctuation width of the servo light after passing through the transparent body 602 does not become so large. Therefore, the light receiving surface of the photodetector 603 can be made considerably smaller than in the case of FIG. 5B, and the cost on the photodetector can be suppressed.
Japanese Patent Laid-Open No. 11-83988

  Generally, in laser radar, laser light is scanned horizontally in a target area. Further, a plurality of horizontal scanning lines are set in the vertical direction. For this reason, in a scanning line at a position shifted in the vertical direction from the center of the target area, the laser beam is moved in the horizontal direction while being swung in the vertical direction by a predetermined angle (an angle corresponding to the target scanning line) from the horizontal direction. It needs to be scanned.

  However, in the mirror rotation type scanning mechanism, when one of the axes is a fixed axis and the mirror is fixed in the vertical direction, the other axis is the rotation axis and the mirror is rotated in the horizontal direction. The scanning trajectory of the laser beam at is not horizontal but tilted from the horizontal. For this reason, in such a scanning mechanism, it is necessary to simultaneously rotate the mirror around two axes so that the scanning locus is horizontal during the scanning operation for each scanning line.

  Here, if the configuration shown in FIG. 13A is used as a configuration for detecting the rotational position of the mirror, the scanning locus of the servo light on the photodetector 603 corresponding to each scanning line on the target region. Will appear multiple times. However, in this case, depending on the arrangement of the semiconductor laser 601, the scanning trajectories of the servo light on the photodetector 603 are not parallel to each other, but are inclined with respect to each other as shown in FIG. For this reason, in order to properly detect the mirror rotation position, it is necessary to perform arithmetic processing corresponding to the inclination angle for each scanning locus on the detection signal from the photodetector 603. The problem of incurring complexity arises.

  The present invention has been made to solve such a problem, and it is an object of the present invention to provide a beam irradiation apparatus that can appropriately detect a mirror rotation position even by simple arithmetic processing.

  In view of the above problems, the present invention has the following features.

  According to a first aspect of the present invention, in a beam irradiation apparatus that scans laser light in a target region, a laser light source that emits the laser light, a mirror that receives the laser light emitted from the laser light source, and the mirror 1 and an actuator that rotates in a first direction and a second direction, respectively, with a second axis perpendicular to the first axis as a rotation axis, and with the rotation of the mirror disposed in the actuator A photorefractive element that rotates in the first direction and the second direction, a servo light source that irradiates the photorefractive element with servo light, and the servo light refracted by the photorefractive element. A photodetector that outputs a signal corresponding to the light receiving position, and an angle direction facing the incident surface of the mirror from the optical axis of the laser light when entering the mirror, and when entering the photorefractive element The laser light and the servo light are incident on the mirror and the photorefractive element so that an angular direction facing the incident surface of the photorefractive element from the optical axis of the servo light is opposite to each other. .

  According to a second aspect of the present invention, in the beam irradiation device according to the first aspect, the photorefractive element is made of a transparent body in which the incident surface and the emission surface of the servo light are parallel to each other.

  According to a third aspect of the present invention, in the beam irradiation apparatus according to the first or second aspect, the servo light is perpendicular to the first axis and the photorefractive element when the mirror is in a neutral position. The optical axis is incident on the photorefractive element such that the optical axis has an inclination of 45 degrees or less with respect to the incident surface.

  According to a fourth aspect of the present invention, in the beam irradiation apparatus according to the third aspect, the servo light scans on the photodetector corresponding to each scanning line when the laser light is horizontally scanned in the target area. The trajectory is incident on the incident surface of the photorefractive element at an angle that approaches the most parallel.

  According to a fifth aspect of the present invention, in the beam irradiation apparatus according to any one of the first to fourth aspects, the laser beam has an optical axis with respect to the incident surface of the mirror when the mirror is in a neutral position. Is incident on the mirror so as to have an inclination of 45 degrees or less.

  According to the first aspect of the present invention, the angle direction facing the incident surface of the mirror from the optical axis of the laser light and the angle direction facing the incident surface of the photorefractive element from the optical axis of the servo light coincide with each other. The scanning trajectories of the servo light on the photodetector can be brought close to being parallel to each other. Therefore, even when processing is performed by approximating that these scanning trajectories are parallel to each other, the mirror rotation position can be properly detected.

  According to invention of Claim 3, each scanning locus | trajectory of the servo light on a photodetector can be made into a substantially parallel state mutually. For this reason, even if processing is performed by approximating that these scanning trajectories are parallel to each other, the rotational position of the mirror can be detected with high accuracy.

  According to the fourth aspect of the present invention, the scanning trajectories of the servo light on the photodetector can be in the most parallel state. For this reason, the detection accuracy of the mirror rotation position when these scanning trajectories are approximated to be parallel to each other can be maximized.

The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the embodiment described below is merely an example when the present invention is implemented, and the present invention is not limited to what is described in the following embodiment.

  FIG. 1 shows a configuration of a mirror actuator 100 according to the present embodiment. 2A is an exploded perspective view of the mirror actuator 100, and FIG. 2B is a perspective view of the mirror actuator 100 in an assembled state.

  In FIG. 1A, reference numeral 110 denotes a mirror holder. The mirror holder 110 has support shafts 111 and 112 having stoppers at the ends. A flat plate mirror 113 is mounted on the front surface of the mirror holder 110, and a coil 114 is mounted on the back surface. The coil 114 is wound in a square shape.

  A parallel plate-shaped transparent body 200 is attached to the support shaft 112. Here, the transparent body 200 is mounted on the support shaft 112 so that the two planes are parallel to the mirror surface of the mirror 113.

  Reference numeral 120 denotes a movable frame that rotatably supports the mirror holder 110 around the support shafts 111 and 112. An opening 121 for accommodating the mirror holder 110 is formed in the movable frame 120, and grooves 122 and 123 that engage with the support shafts 111 and 112 of the mirror holder 110 are formed. Further, support shafts 124 and 125 having stoppers at the ends are formed on the side surface of the movable frame 120, and a coil 126 is mounted on the back surface. The coil 126 is wound in a square shape.

  A fixed frame 130 supports the movable frame 120 so as to be rotatable about the support shafts 124 and 125. The fixed frame 130 has a recess 131 for accommodating the movable frame 120, and grooves 132 and 133 that engage with the support shafts 124 and 125 of the movable frame 120. Further, a magnet 134 for applying a magnetic field to the coil 114 and a magnet 135 for applying a magnetic field to the coil 126 are mounted on the inner surface of the fixed frame 130. The grooves 132 and 133 respectively extend from the front surface of the fixed frame 130 into the gap between the upper and lower two magnets 135.

  Reference numeral 140 denotes a leaf spring that presses the support shafts 111 and 112 from the front so that the support shafts 111 and 112 of the mirror holder 110 do not fall out of the grooves 122 and 123 of the movable frame 120. Reference numeral 141 denotes a leaf spring that presses the support shafts 124 and 125 from the front so that the support shafts 124 and 125 of the movable frame 120 do not fall out of the grooves 132 and 133 of the fixed frame 130.

  When assembling the mirror actuator 100, the support shafts 111 and 112 of the mirror holder 110 are engaged with the grooves 122 and 123 of the movable frame 120, and further, the front surfaces of the support shafts 111 and 112 are pressed down, so that the leaf spring 140 is attached to the front surface of the movable frame 120. Thereby, the mirror holder 110 is rotatably supported by the movable frame 120.

  After mounting the mirror holder 110 on the movable frame 120 in this way, the support shafts 124 and 125 of the movable frame 120 are engaged with the grooves 132 and 133 of the fixed frame 130, and further, the front surfaces of the support shafts 132 and 133 are pressed. In this manner, the leaf spring 141 is attached to the front surface of the fixed frame 130. Thereby, the movable frame 120 is rotatably attached to the fixed frame 130, and the assembly of the mirror actuator 100 is completed.

  When the mirror holder 110 rotates about the support shafts 111 and 112 with respect to the movable frame 120, the mirror 113 rotates accordingly. When the movable frame 120 rotates about the support shafts 124 and 125 with respect to the fixed frame 130, the mirror holder 110 rotates accordingly, and the mirror 113 rotates integrally with the mirror holder 110. As described above, the mirror holder 110 is supported by the support shafts 111 and 112 and the support shafts 124 and 125 orthogonal to each other so as to be rotatable in a two-dimensional direction. Rotate in the dimension direction. At this time, the transparent body 200 attached to the support shaft 112 also rotates as the mirror 113 rotates.

  In the assembled state shown in FIG. 6B, the two magnets 134 are arranged and polarized so that turning current about the support shafts 111 and 112 is generated in the mirror holder 110 by applying a current to the coil 114. Has been adjusted. Therefore, when a current is applied to the coil 114, the mirror holder 110 is rotated about the support shafts 111 and 112 by the electromagnetic driving force generated in the coil 114, and accordingly, the transparent body 200 is rotated.

  Further, in the assembled state shown in FIG. 5B, the two magnets 135 are arranged and polarized so that when a current is applied to the coil 126, rotational force about the support shafts 124 and 125 is generated in the movable frame 120. Has been adjusted. Therefore, when a current is applied to the coil 126, the movable frame 120 is rotated about the support shafts 124 and 125 by the electromagnetic driving force generated in the coil 126, and the transparent body 200 is rotated accordingly.

  FIG. 2 is a diagram illustrating a configuration of the optical system in a state where the mirror actuator 100 is mounted.

  In FIG. 2, reference numeral 500 denotes a base that supports the optical system. In the base 500, an opening (not shown in FIG. 2) is formed at the installation position of the mirror actuator 100, and the mirror actuator 100 is mounted on the base 500 so that the transparent body 200 is inserted into the opening. ing.

  An optical system 400 for guiding the laser beam to the mirror 113 is mounted on the upper surface of the base 500. The optical system 400 includes two mirrors 401 and 402, beam shaping lenses 403 and 404, and a semiconductor laser (not shown in FIG. 2).

  Laser light emitted upward from a semiconductor laser (not shown) is reflected in the horizontal direction by the mirror 401, and then the traveling direction is bent 90 degrees in the horizontal direction by the mirror 402. Thereafter, the laser light is subjected to a convergence effect in the horizontal direction and the vertical direction by the lenses 403 and 404, respectively. The lenses 403 and 404 have a beam shape of a predetermined size (for example, about 2 m in length and about 1 m in width) in a target region (for example, set at a position about 150 m ahead from the beam exit of the beam irradiation device). The lens surface is designed to be (size).

  The laser light transmitted through the lenses 403 and 404 is incident on the mirror 113 of the mirror actuator 100 and is reflected by the mirror 113 toward the target area. When the mirror 113 is driven two-dimensionally by the mirror actuator 100, the laser light is scanned in a two-dimensional direction within the target region.

  The mirror actuator 100 is arranged so that the laser beam from the lens 404 is incident on the mirror surface of the mirror 113 at an incident angle of 45 degrees in the horizontal direction when the mirror 113 is in the neutral position. The “neutral position” refers to the position of the mirror 113 when the mirror surface is parallel to the vertical direction and the laser beam is incident at an incident angle of 45 degrees in the horizontal direction with respect to the mirror surface.

  FIG. 3 is a partial plan view of the base 500 when viewed from the back side. FIG. 3 shows a portion near the position where the mirror actuator 100 is mounted on the back side of the base 500.

  As shown in the drawing, walls 501 and 502 are formed on the periphery on the back side of the base 500, and a flat surface 503 that is one step lower than the walls 501 and 502 is located on the center side of the walls 501 and 502. An opening for mounting the semiconductor laser 303 is formed in the wall 501. The substrate 301 on which the semiconductor laser 303 is mounted is mounted on the outer surface of the wall 501 so that the semiconductor laser 303 is inserted into the opening.

  On the other hand, a notch 502 a is formed in the wall 502, and the substrate 302 on which the PSD 306 is attached is attached to the outer surface of the wall 502 so that the PSD 306 is accommodated in the notch 502 a.

  A condensing lens 304 is attached to a flat surface 503 on the back side of the base 500 by a fixture 305. Further, an opening 503a is formed in the flat surface 503, and the transparent body 200 attached to the mirror actuator 100 protrudes from the back side of the base 500 through the opening 503a. Here, the transparent body 200 is positioned such that when the mirror 113 of the mirror actuator 100 is in the neutral position, the two planes are parallel to the vertical direction and inclined by 45 degrees with respect to the emission optical axis of the semiconductor laser 300. It is done.

  Laser light emitted from the semiconductor laser 303 (hereinafter referred to as “servo light”) passes through the condenser lens 304 and then enters the transparent body 200, and is refracted by the transparent body 200 as shown in FIG. Affected. Thereafter, the servo light transmitted through the transparent body 200 is received by the PSD 306, and a position detection signal corresponding to the light receiving position is output from the PSD 306.

  FIG. 4 is a diagram showing a scanning state of the laser light in the target area and a scanning state of the servo light on the PSD 306.

  In the present embodiment, as shown in FIG. 4A, the laser beam is scanned horizontally in the target area. Further, the horizontal scanning lines are set in five stages in the vertical direction. For this reason, in the four scanning lines that are shifted in the vertical direction from the center of the target region (scanning line 3), as shown in FIG. It is necessary to scan in the horizontal direction while swinging in the vertical direction (+ α direction or −α direction) by an angle corresponding to the angle.

  However, in the mirror actuator according to the present embodiment, the other shaft (support shafts 111 and 112) is rotated while the mirror 113 is fixed in the vertical direction with one shaft (support shafts 124 and 125) as a fixed shaft. When the mirror 113 is rotated in the horizontal direction as a moving axis, the scanning trajectory of the laser beam in the target area is not horizontal as shown in FIG. 4A, but is inclined from the horizontal. For this reason, in this mirror actuator, the mirror 113 is rotated in the horizontal direction around the support shafts 111 and 112 so that the scan locus becomes horizontal during the scanning operation for each scanning line, and at the same time, the support shaft 124. , 125 needs to be rotated in the vertical direction about the rotation axis.

  At this time, in this embodiment, since the optical axis of the servo light when entering the transparent body 200 is perpendicular to the optical axis of the laser light when entering the mirror 113, FIG. As shown in (), the scanning trajectories of servo light on the PSD 306 are substantially parallel to each other. Note that the five dotted arrows shown in FIG. 7C represent the scanning trajectory of the servo light corresponding to each scanning line in FIG. For this reason, even when processing is performed by approximating that these scanning trajectories are parallel to each other, the mirror rotation position can be properly detected.

<Verification 1>
Hereinafter, the verification result (simulation) of this effect will be described.

  FIG. 5A is a diagram showing the optical system in the example, and FIG. 5B is a diagram showing the optical system in the comparative example. In the figure, reference numeral 405 denotes a semiconductor laser that emits a laser beam applied to a target area. The other numbering components are the same as the numbering components used in the above embodiment.

  Here, the transparent body 200 is disposed immediately below the mirror 113. In both the example and the comparative example, the mirror 113 and the transparent body 200 are arranged so that the laser beam and the servo beam are incident on the incident surface with an inclination of 45 degrees in the neutral position. Further, in the example of FIG. 5A, as in the above embodiment, the optical axis of the servo light when entering the transparent body 200 and the optical axis of the laser light when entering the mirror 113 are perpendicular to each other. ing. On the other hand, in the comparative example of FIG. 5B, the servo light is incident on the transparent body 200 from the Z-axis direction, and the optical axis of the servo light when entering the transparent body 200 and the laser when entering the mirror 113. The optical axes of light are parallel to each other.

  Other simulation conditions are as follows.

a. Servo light wavelength: 650 nm
b. Refractive index of transparent body: 1.5
c. Transparent body thickness: 3 mm

  Under this condition, assuming that the laser beam is scanned in the horizontal direction within a range of ± 22.5 degrees from the midpoint of the scan line at each scan line in FIG. Obtained by simulation. Here, it is assumed that the optical axis of the laser beam is horizontal in the scanning line 3 at the center, and the optical axis of the laser beam is horizontal from the horizontal in the scanning line 2 and the scanning line 4, respectively, in the + α direction and − of FIG. It is assumed that the angle is inclined by 2.5 degrees in the α direction, and in the scanning line 1 and the scanning line 5, the optical axis of the laser light is 5 degrees from the horizontal to the + α direction and the −α direction in FIG. It was inclined.

  FIG. 6 is a diagram showing a simulation result for the example, and FIG. 7 is a diagram showing a simulation result for the comparative example. In the figure, the diagrams indicated as “5”, “2.5”, “0”, “−2.5”, “−5” indicate that the laser beam is “5 degrees in the vertical direction in the target area, respectively. ”,“ 2.5 degrees ”,“ 0 degrees ”,“ −2.5 degrees ”,“ −5 degrees ”with the scanning trajectory of the servo light on the PSD 306 when scanned in the horizontal direction. Show. That is, in the diagrams indicated as “5”, “2.5”, “0”, “−2.5”, and “−5”, the laser beam is the scanning line 1 in FIG. 4 shows the scanning trajectory of servo light on the PSD 306 when the scanning line 2, the scanning line 3, the scanning line 4, and the scanning line 5 are scanned.

  First, referring to FIG. 7, in the comparative example, the scanning trajectories of the servo light on the PSD 306 are not parallel to each other, and the PSD 306 increases as the scanning line on the target area moves away from the central scanning line 3 in the vertical direction. It can be seen that the inclination of the scanning path of the servo light increases.

  In contrast, in the embodiment, as shown in FIG. 6, the scanning trajectories of the servo light on the PSD 306 are substantially parallel to each other, and the scanning line on the target area is separated from the central scanning line 3 in the vertical direction. However, it can be seen that the scanning trajectory of the servo light on the PSD 306 does not tilt so much.

  From this simulation result, each scanning locus of the servo light on the PSD 306 is obtained by making the optical axis of the servo light incident on the transparent body 200 perpendicular to the optical axis of the laser light incident on the mirror 113. It was confirmed that can be made substantially parallel to each other.

  Therefore, as in the present embodiment, the optical system is configured so that the optical axis of the servo light when entering the transparent body 200 is perpendicular to the optical axis of the laser light when entering the mirror 113. For example, the scanning trajectories of the servo light on the PSD 306 can be made substantially parallel to each other. Therefore, according to the present embodiment, even when processing is performed by approximating that these scanning trajectories are parallel to each other, the rotational position of the mirror can be detected properly. Therefore, the rotation position of the mirror or the scan position of the laser beam in the target area can be detected appropriately with simple processing.

  In the above embodiment, the mirror 113 and the transparent body 200 are arranged so as to be parallel to each other. However, as shown in FIG. 8, the servo laser composed of the semiconductor laser 303, the condenser lens 304, the transparent body 200, and the PSD 306 is used. Even if the optical system is rotated and arranged in the XZ plane direction so as to be inclined with respect to the mirror 113 while maintaining the positional relationship of these optical components, the same effect as described above can be obtained. FIGS. 4A and 4B are arrangement examples when the servo optical system is rotated counterclockwise and clockwise, respectively.

<Verification 2>
In the above embodiment, the angle between the optical axis of the servo light and the incident surface of the transparent body 200 when the transparent body 200 is in the neutral position is set to 45 degrees. Thus, the servo light scanning locus on the PSD 306 may change.

  Therefore, the inventors set the transparent body 200 in the in-plane direction of the XZ plane from the initial position (position parallel to the mirror 113) as shown in FIG. 9 under the same conditions as in FIG. It was rotated and how the scanning trajectory of the servo light on the PSD 306 changes at each rotational position was obtained by simulation. This will be described below.

  FIG. 10 is a diagram illustrating a scanning locus of servo light on the PSD 306 when the angle θ in FIG. 9 is changed. Here, the angle θ is positive in the clockwise direction in FIG. 9 and negative in the counterclockwise direction. The scanning trajectory at each angle is the one when the angle α in FIG. 4 is +5 degrees, that is, the one when the scanning line 1 is scanned. Other simulation conditions are the same as in the case of FIG. 5A (verification 1).

  Referring to FIG. 10, when the transparent body 200 is rotated in the clockwise direction of FIG. 9 from the state in which the transparent body 200 is parallel to the mirror 113 (the diagram of θ = 0 degrees in the figure), the inclination of the servo light on the PSD 306 is obtained. When the transparent body 200 is rotated clockwise in FIG. 9, it can be seen that the inclination of the servo light on the PSD 306 is smaller than that at the initial position. Therefore, based on the verification result, in order to bring the scanning locus of the servo light corresponding to each scanning line closer to parallel, the transparent body 200 is rotated counterclockwise in FIG. It can be seen that it is advantageous to make the angle between the transparent body 200 and the transparent body 200 smaller than 45 degrees.

FIG. 11 shows the amount of displacement in the Y direction in the locus of the servo light on the PSD 306 by changing the angle θ shown in FIG. Here, the displacement (vertical axis) is
Displacement amount = (maximum value in Y direction position−minimum value in Y direction position) / minimum value in Y direction position (calculated as a percentage). The horizontal axis is the angle θ in FIG. 9, and the clockwise direction is positive as described above. Similarly to the case of FIG. 10, the displacement amount at each angle is that when the angle α in FIG. 4 is +5 degrees, that is, when the scanning line 1 is scanned.

  Referring to the figure, it can be seen that the displacement amount increases as the angle θ increases, and therefore the inclination of the servo light scanning locus on the PSD 306 increases. This is consistent with the verification in FIG.

  On the other hand, when the angle θ is reduced, the amount of displacement gradually decreases until it exceeds −15 degrees, but when the angle θ is exceeded, the amount of displacement gradually increases and the angle θ becomes −45. It can be seen that the amount of displacement is substantially the same as in the initial state (θ = 0). Therefore, it can be said that the transparent body 200 is preferably arranged so that θ in FIG. 9 is about −18 degrees in order to make the scanning trace of the servo light corresponding to each scanning line most parallel.

  Summarizing the above verification, the following matters can be derived.

  (1) From the verification results (Verification 1) in FIGS. 6 and 7, when the transparent body 200 and the mirror 113 are parallel, the optical axis of the servo light when entering the transparent body 200 and the mirror 113 are incident. When the optical axis of the laser beam at that time is vertical, the scanning locus of the servo light can be made parallel. However, as shown in FIG. 8, the servo optical system comprising the semiconductor laser 303, the condensing lens 304, the transparent body 200 and the PSD 306 is tilted with respect to the mirror 113 while maintaining the positional relationship of these optical components. The same effect can be obtained even if the rotation is arranged in the Z plane direction.

  After all, as shown in FIGS. 12A and 12C, the effect is that the angle direction A1 that faces the incident surface of the mirror 113 from the optical axis of the laser beam when entering the mirror 113, and the transparent body 200 The laser beam and the servo light are incident on the mirror 113 and the transparent body 200 so that the angle direction A2 facing the incident surface of the transparent body 200 from the optical axis of the servo light when entering the mirror is opposite to each other. The

  That is, as shown in FIGS. 12B and 12D, an angular direction A1 that faces the incident surface of the mirror 113 from the optical axis of the laser light and an angular direction A2 that faces the incident surface of the transparent body 200 from the optical axis of the servo light. When the laser beam and the servo beam are incident on the mirror 113 and the transparent body 200 so that they are in the same direction (here, the counterclockwise direction), as shown in FIG. The servo light scanning trajectories are not parallel to each other.

  Therefore, in order to parallelize the scanning trajectory of the servo light, as shown in FIGS. 12A and 12C, the angular direction A1 (counterclockwise) and the angular direction A2 (clockwise) are made opposite to each other. Is preferred.

  (2) From the verification results (Verification 2) of FIGS. 10 and 11, in order to further parallelize the scanning trajectory of the servo light, the incidence of the transparent body 200 occurs when the mirror 113 (transparent body 200) is in the neutral position. The servo light is preferably incident on the transparent body 200 so that the optical axis has an inclination of 45 degrees or less with respect to the surface.

  (3) From the verification result of FIG. 11 (Verification 2), in order to make the scanning trace of the servo light most parallel, when the mirror 113 (transparent body 200) is in the neutral position, the incident surface of the transparent body 200 is The servo light is preferably incident on the transparent body 200 so that the optical axis has an inclination of about 20 degrees.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the embodiment of the present invention can be variously modified in addition to the above.

  For example, in the above embodiment, a semiconductor laser is used as a light source for servo light, but instead of this, an LED (Light Emitting Diode) may be used. In the above-described embodiment, PSD is used as a photodetector that receives servo light. However, a quadrant sensor 310 may be used as a photodetector.

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

The figure which shows the structure of the mirror actuator which concerns on embodiment The figure which shows the optical system of the beam irradiation apparatus which concerns on embodiment The figure which shows the optical system of the beam irradiation apparatus which concerns on embodiment The figure explaining the scanning state of the laser beam and servo light which concern on embodiment The figure which shows the optical system of the Example which concerns on verification 1, and a comparative example The figure which shows the verification result of the Example which concerns on verification 1. The figure which shows the verification result of the comparative example which concerns on verification 1 The figure which shows the example of a change of the servo optical system which concerns on embodiment The figure explaining the rotation state of the optical system which concerns on verification 2, and a transparent body The figure which shows the verification result which relates to verification 2 The figure which shows the verification result which relates to verification 2 The figure which shows the relationship between the laser beam and servo light which concern on embodiment The figure explaining the position detection method using a photorefractive element and a mirror

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Mirror actuator 110 Mirror holder 111 Support shaft 112 Support shaft 113 Mirror 120 Movable frame 124 Support shaft 125 Support shaft 130 Fixed frame 200 Transparent body 303 Semiconductor laser 306 PSD

Claims (5)

In a beam irradiation apparatus that scans a laser beam in a target area,
A laser light source for emitting the laser light;
A mirror on which laser light emitted from the laser light source is incident;
An actuator for rotating the mirror in a first direction and a second direction about a first axis and a second axis perpendicular to the first axis as a rotation axis;
A photorefractive element disposed in the actuator and rotating in the first direction and the second direction as the mirror rotates;
A servo light source for irradiating the photorefractive element with servo light;
A photodetector that receives the servo light refracted by the photorefractive element and outputs a signal corresponding to the light receiving position;
The angle direction facing the incident surface of the mirror from the optical axis of the laser beam when entering the mirror, and the incident surface of the photorefractive element from the optical axis of the servo light when entering the photorefractive element The laser beam and the servo beam are incident on the mirror and the photorefractive element so that the angular directions are opposite to each other.
A beam irradiation apparatus characterized by that. In claim 1,
The photorefractive element is made of a transparent body in which the incident surface and the emission surface of the servo light are parallel to each other.
A beam irradiation apparatus characterized by that. In claim 1 or 2,
When the mirror is in a neutral position, the servo light is perpendicular to the first axis and has an optical axis having an inclination of 45 degrees or less with respect to the incident surface of the photorefractive element. Incident on the photorefractive element;
A beam irradiation apparatus characterized by that. In claim 3,
The servo light is incident on the incident surface of the photorefractive element at an angle at which the scanning locus on the photodetector corresponding to each scanning line when the laser light is scanned horizontally in the target area is closest to the parallel. Incident,
A beam irradiation apparatus characterized by that. In any one of Claims 1 thru | or 4,
The laser light is incident on the mirror such that the optical axis has an inclination of 45 degrees with respect to the incident surface of the mirror when the mirror is in a neutral position.
A beam irradiation apparatus characterized by that.

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