JP2009085947A - Beam irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a beam irradiation device capable of detecting precisely a scanning position of a laser beam in a target area. <P>SOLUTION: A transparent body 200 is arranged to be turned in accompaniment to a mirror 113 for scanning the beam. The transparent body 200 is irradiated with a servo light to receive the servo light refracted by the transparent body 200, by a PSD 306. Micro-fine periodic structure 201 tapered along with separation from an incident face and an outgoing face is formed on the incident face and the outgoing face of servo light, at a pitch of a servo light wavelength band or less. <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.

  The applicant previously filed Japanese Patent Application No. 2006-121762 and 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 mirror is driven two-dimensionally around each drive axis, whereby the reflected light of the laser light from the mirror is scanned in the 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. 11 is a diagram illustrating a configuration example when the rotation position of another member is detected in this manner. FIG. 4A is a configuration example in the case where a parallel plate-shaped translucent member is used as another member, and FIG. 4B is a configuration example in which a mirror member is used as another member.

  In FIG. 1A, reference numeral 601 denotes a semiconductor laser, 602 denotes a light-transmitting member, and 603 denotes a photodetector (PSD: Position Sensing Device). The laser light emitted from the semiconductor laser 601 is refracted by the translucent member 602 disposed to be inclined with respect to the laser optical axis, and is received by the photodetector 603. Here, when the translucent member 602 rotates as shown by an arrow, the optical path of the laser light changes as indicated by a dotted line in the drawing, and the light receiving position of the laser light on the photodetector 603 changes. Therefore, the rotational position of the translucent member 602 can be detected from the light receiving position of the laser beam detected by the photodetector 603.

  In FIG. 5B, 611 is a semiconductor laser, 612 is a mirror member, and 613 is a photodetector (PSD). The laser light emitted from the semiconductor laser 611 is reflected by the mirror member 612 disposed to be inclined with respect to the laser optical axis, and is received by the photodetector 613. Here, when the mirror member 612 rotates as shown by an arrow, the optical path of the laser light changes as indicated by a dotted line in the drawing, and the light receiving position of the laser light on the photodetector 613 changes. Therefore, the rotational position of the mirror member 612 can be detected from the light receiving position of the laser beam detected by the photodetector 613.

Here, when the mirror member 612 is rotated by an angle α as shown in FIG. 5B, the swing angle of the laser light reflected by the mirror member 612 is 2α. For this reason, it is necessary to enlarge the light receiving surface of the photodetector 613. On the other hand, when the translucent member 602 is used as shown in FIG. 5A, even if the translucent member 602 is rotated, the fluctuation width of the laser light after passing through the translucent member 602 does not increase so much. 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

  However, when the translucent member 602 is rotated in this manner, the proportion of light reflected by the laser light incident surface and the exit surface of the translucent member 602 changes with the rotation. For this reason, the light quantity of the laser beam received by the photodetector 603 changes as the translucent member 602 rotates, thereby causing an error in the position detection signal output from the photodetector 603. It becomes like this. This error affects the detection accuracy of the laser beam scanning position in the target area.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a beam irradiation apparatus capable of accurately detecting a scanning position of a laser beam in a target region.

  According to a first aspect of the present invention, in a beam irradiation apparatus that scans laser light in a target region, an optical element that changes a traveling direction of the laser light by rotating in a predetermined direction, and the optical element is rotated in the direction. An actuator to be moved, a photorefractive element that is arranged in the actuator and rotates as the optical element rotates, a servo light source that irradiates servo light to the photorefractive element, and the servo that is refracted by the photorefractive element A photodetector that receives light and outputs a signal corresponding to the light receiving position, and has a period at a pitch equal to or lower than the wavelength band of the servo light on the servo light incident surface and the light emitting surface of the photorefractive element. A structure is formed.

  According to a second aspect of the present invention, in the beam irradiation apparatus according to the first aspect, the periodic structure has a tapered cone shape.

  According to a third aspect of the present invention, in the beam irradiation apparatus according to the first or second aspect, the photorefractive element is a flat plate-shaped translucent member.

  According to a fourth aspect of the present invention, in the beam irradiation apparatus according to any one of the first to third aspects, the optical element is a mirror.

  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 actuator includes a first support portion that rotatably supports the optical element in a first direction. , A second support portion that rotatably supports the first support portion in a second direction different from the first direction, and the first support portion and the second support portion are connected to the first direction. And an electromagnetic drive unit that drives in the first direction and the second direction.

  A sixth aspect of the present invention is the beam irradiation apparatus according to any one of the first to fifth aspects, wherein the photorefractive element is mounted on a rotating shaft that rotates the optical element. To do.

  In the present invention, the periodic structure has the intensity of the laser beam transmitted through the photorefractive element within the range of the swing angle of the optical element (equivalent to the swing angle of the photorefractive element) when the target region is irradiated with the beam. It is desirable to form so as not to substantially change. Specifically, an aspect ratio (aspect ratio = height of the periodic structure / periodic structure) in which the light transmission characteristics of the periodic structure hardly depend on the incident angle of the laser beam within the range of the swing angle. It is desirable to form a periodic structure at a pitch of 1).

  In the following embodiments, the swing angle of the transparent body (corresponding to the photorefractive element of the present invention) is ± 15 degrees with respect to the neutral position (laser light is incident on the transparent body at an incident angle of 45 degrees). The change in the intensity of the laser beam (corresponding to the servo light of the present invention) on the PSD (corresponding to the photodetector of the present invention) at the time has been verified. In this verification, the intensity change of the laser beam on the PSD within the range of the swing angle is suppressed to 1% or less. In this case, the error of the position detection signal output from the PSD is negligible in the evaluation of the detection accuracy of the scan position of the laser beam in the target area.

  At least in this way, if the change in the intensity of the servo light on the photodetector is suppressed to 1% or less, the deterioration of the detection accuracy of the scan position of the laser light in the target area is negligible. . The aspect ratio of the periodic structure is preferably set so that the change in the intensity of the servo light on the photodetector is 1% or less within the range of the swing angle of the photorefractive element.

  According to the present invention, since the reflection of the servo light is suppressed by the fine periodic structure, even if the photorefractive element rotates with the rotation of the optical element, the received light amount of the servo light in the photodetector is large. There will be no change. Therefore, the error of the position detection signal output from the photodetector can be suppressed, and the scan position of the laser beam in the target area can be detected with high accuracy.

  If the photorefractive element is attached to the rotation shaft of the optical element, the behavior of the optical element can be directly reflected on the photorefractive element. Therefore, the scan position of the laser beam in the target area can be detected with high accuracy from the detection result of the rotation position in the photorefractive element.

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. A fine periodic structure 201 is formed on these two planes of the transparent body 200 as will be described later.

  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 pressing plate 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 pressing plate 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 the front surfaces of the support shafts 111 and 112 are further pressed to hold down the press plate. 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 holding plate 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 rotates about the support shafts 111 and 112 by the electromagnetic driving force generated in the coil 114.

  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).

  Laser light emitted upward from a laser light source (not shown) is reflected by the mirror 401 in the horizontal direction, 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 area (for example, set at a position about 100 m in front of the beam emission port 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 undergoes a refraction action. 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.

  Here, in the transparent body 200, a fine periodic structure 201 is formed on the incident surface and the exit surface of the servo light, as shown in FIG. The periodic structure 201 suppresses the reflection of servo light on the incident surface and the exit surface of the transparent body 200.

  FIG. 4 is a diagram schematically showing the periodic structure 201. 1A is a perspective view of the periodic structure 201, and FIGS. 1B and 1C are a plan view and a side view of the periodic structure 201. FIG.

  As illustrated, the periodic structure 201 is formed by arranging tapered cone-shaped protrusions 201 a having a predetermined height H at a predetermined pitch P. When the transparent body 200 is formed from a resin material such as polycarbonate or cycloolefin polymer, the periodic structure 201 can be formed by injection molding using a mold having such a periodic structure. Such a protrusion 201a is called a surface non-reflective structure, and is formed with a periodic structure having a tapered cone shape. The shape is not limited to a cone as shown in the figure, and may be a pyramid or the like.

  When the transparent body 200 is made of a glass material in addition to the resin material, the periodic structure 201 can be formed on the plane of the transparent body 200 by so-called 2P molding. In such 2P molding, an ultraviolet curable resin is applied to a flat surface on the transparent body 200, and the ultraviolet curable resin is cured by irradiating ultraviolet rays in a state where a mold having a periodic structure is pressed. By peeling off from the ultraviolet curable resin, the periodic structure 201 is formed on the plane of the transparent body 200.

  In addition, when the transparent body 200 is formed from a thermosetting resin or a thermoplastic resin, the periodic structure 201 can be formed on the transparent body 200 using a thermal imprint technique.

  When the periodic structure 201 is formed using an ultraviolet curable resin, refraction close to the refractive index of the transparent body 200 in order to suppress reflection of servo light at the boundary surface between the transparent body 200 and the ultraviolet curable resin. It is necessary to use an ultraviolet curable resin with a high rate.

  FIG. 5 is a diagram showing the relationship between the periodic structure 201 and the refractive index. As shown in the figure, when the periodic structure 201 is formed on a medium having a refractive index n1, the effective refractive index on the surface of the incident medium of light gradually changes, as if between two media (refractive indices n0 and n1). In this state, there is no refractive index boundary. Thereby, the reflectance at the light incident surface of the medium having the refractive index n1 is suppressed. This phenomenon occurs when the pitch of the periodic structure 201 in the light incident plane direction is smaller than the wavelength of the incident light.

  Therefore, if P ≦ λ / n, where P is the pitch of the protrusions 201a on the periodic structure 201, n is the refractive index of the material, and λ is the wavelength of the servo light, the servo light on the incident surface and the reflective surface of the transparent body 200 is set. Reflection can be suppressed. In this embodiment, from this viewpoint, the pitch P of the periodic structure 201 formed on the incident surface and the reflecting surface of the transparent body 200 is set to be equal to or less than the wavelength of the servo light.

  In the present embodiment, the transparent body 200 is arranged in a state inclined with respect to the optical axis of the servo light, and the inclination angle changes as the mirror 113 rotates. For this reason, it is necessary to verify how the reflection suppression effect in the periodic structure 201 changes with respect to the change in the tilt angle of the transparent body 200 with respect to the servo light (angle dependency). On the other hand, the inventors actually formed the transparent body 200 having the periodic structure 201 on the incident surface and the emission surface, and verified the angle dependency. This will be described later with reference to FIG.

  As can be seen with reference to FIG. 5, as the height H of the protrusion 201a is higher, the change in the effective refractive index of light on the surface of the incident medium becomes more gradual, and reflection on the surface of the incident medium is suppressed. Therefore, it can be said that the change in the reflection suppression effect due to the change in the tilt angle of the transparent body 200 with respect to the servo light is suppressed as the height H of the protrusion 201a is increased. That is, as the aspect ratio of the periodic structure 201 (aspect ratio = height H of the periodic structure 201 / pitch P of the periodic structure 201) is larger, the fluctuation of the reflection suppressing effect due to the fluctuation of the tilt angle of the transparent body 200 can be suppressed. it can.

  6A is a diagram (side sectional view) showing a configuration of the PSD 306, and FIG. 6B is a diagram showing a light receiving surface of the PSD 306. As shown in FIG.

  Referring to FIG. 6A, PSD 306 has a structure in which a P-type resistance layer serving as a light-receiving surface and a resistance layer is formed on the surface of an N-type high-resistance silicon substrate. On the surface of the resistance layer, electrodes X1 and X2 for outputting a photocurrent in the horizontal direction of FIG. 2B and electrodes Y1 and Y2 for outputting a photocurrent in the vertical direction (shown in FIG. 1A). (Omitted) is formed. A common electrode is formed on the back side.

  When the light receiving surface is irradiated with laser light, an electric charge proportional to the amount of light is generated at the irradiation position. This electric charge reaches the resistance layer as a photocurrent, is divided in inverse proportion to the distance to each electrode, and is output from the electrodes X1, X2, Y1, and Y2. Here, the current output from the electrodes X1, X2, Y1, and Y2 has a magnitude divided in inverse proportion to the distance from the laser light irradiation position to each electrode. Therefore, the light irradiation position on the light receiving surface can be detected based on the current values output from the electrodes X1, X2, Y1, and Y2.

  For example, it is assumed that servo light is irradiated to the position P in FIG. In this case, the coordinates (x, y) of the position P with the center of the light receiving surface as the reference point are the current amounts output from the electrodes X1, X2, Y1, Y2, respectively, in the Ix1, Ix2, Iy1, Iy2, X direction and When the distance between the electrodes in the Y direction is Lx and Ly, for example, it is calculated by the following equation.

   FIG. 7B is a diagram showing a configuration of an arithmetic circuit that realizes this calculation formula. Current signals Ix1, Ix2, Iy1, and Iy2 output from the electrodes X1, X2, Y1, and Y2 are amplified by amplifiers 11, 12, 13, and 14, respectively. Then, (Ix2 + Ix1) and (Iy2 + Iy1) are calculated by the adder circuits 15 and 17, respectively, and (Ix2-Ix1) and (Iy2-Iy1) are respectively performed by the subtractor circuits 16 and 18. Is calculated. Further, the division circuits 19 and 20 respectively divide the left sides of the equations (1) and (2). From the division circuits 19 and 20, the x-direction position (2x / Lx) at the servo light receiving position P is obtained. ) And a position detection signal indicating the y-direction position (2y / Ly).

  In this calculation, when the received amount of servo light in the PSD 306 changes with the rotation of the transparent body 200, the denominator and numerator on the left side of the above formulas (1) and (2) change. Due to this influence, an error is included in the position detection signals output from the division circuits 19 and 20. This error is suppressed as the change in the received amount of servo light in the PSD 306 is smaller.

  In the present embodiment, as described above, since the fine periodic structure 201 is formed on the entrance surface and the exit surface of the transparent body 200, fluctuations in the amount of received PSD light when the transparent body 200 rotates are suppressed. . For this reason, the error contained in a position detection signal can be suppressed notably.

  Below, the verification result which verified this effect is shown.

  FIG. 8 is a diagram showing a measurement method in this verification. Here, a semiconductor laser that emits laser light having a wavelength of 650 nm was used as a light source for servo light. Further, as a sample to be verified (transparent refractor), a transparent body 200 (implementation sample) according to the present embodiment, a parallel plate-like transparent body (comparative sample 1) in which the periodic structure 201 is not formed, and this A transparent anti-reflection coating (Comparative Sample 2) was prepared on the entrance surface and exit surface of the transparent body. The transparent refractor was tilted in one direction from the state where the incident surface and the exit surface were perpendicular to the laser optical axis, and the amount of light transmitted through the transparent refractor was measured at each tilt angle.

  The measurement conditions are as follows.

a. Comparative sample 1
Material: Polycarbonate (refractive index 1.58)
Thickness: 1mm
b. Comparison sample 2
Material: Polycarbonate (refractive index 1.58)
Thickness: 1mm
Incident surface: Multilayer antireflection film (Nippon Yushi Co., Ltd., model number 8201UV) is mounted Outgoing surface: Multilayer antireflection film (Nippon Yushi Co., Ltd., model number 8201UV) is mounted c. Implementation sample Material: Polycarbonate (refractive index 1.58)
Thickness: 1mm
Incident surface: forming a periodic structure with a pitch of 300 nm and an aspect ratio of 1.52 Outgoing surface: forming a periodic structure with a pitch of 300 nm and an aspect ratio of 1.52

  In addition, the periodic structure in the implementation sample was formed by 2P molding using an ultraviolet curable resin (refractive index 1.52). The output power of the servo light semiconductor laser for each sample was the same.

  FIG. 9 shows the measurement results. The horizontal axis represents the tilt angle θ in FIG. 8, and the vertical axis represents the measured value of transmitted light intensity in the power meter. The vertical axis shows the measured value when the inclination angle θ is 0 degree as 1. In the figure, “ARS (Anti Reflection Structure)” is the measurement result for the implementation sample, “PC panel” is the measurement result for the comparison sample 1, and “AR film” is the measurement result for the comparison sample 2. is there. Also, the deflection range (hereinafter referred to as “detection range”) of the transparent refracting body (sample) when the mirror 113 swings in the range of ± 15 degrees (a deflection angle = 30 degrees) in the horizontal direction from the neutral position is indicated by a dotted line. ing.

  Referring to this measurement result, it can be seen that when the comparative samples 1 and 2 are used as the transparent refractors, the transmitted light intensity greatly changes in the detection range. Therefore, in this case, it is predicted that the position detection signal obtained by the arithmetic circuits of the above formulas (1), (2) and FIG. 7B includes a large error component based on the change in transmitted light intensity. The

  On the other hand, when the implementation sample is used as the transparent refractor, the transmitted light intensity hardly changes in the detection range. Specifically, the transmitted light intensity when the incident angle is 35 degrees is 1.00, the transmitted light intensity when the incident angle is 55 degrees is 0.99, and the variation between the two is about 1%. Therefore, according to the implementation sample, the position detection signal obtained by the arithmetic circuits of the above formulas (1), (2) and FIG. 7B does not include an error component based on the fluctuation of the transmitted light intensity. It is assumed that the scan position of the laser beam in the region can be detected with high accuracy.

  As described above, according to the present embodiment, since the reflection of the servo light is suppressed by the fine periodic structure 201, the servo light in the PSD 306 can be obtained even if the transparent body 200 rotates with the rotation of the mirror 113. There is no significant change in the amount of received light. Therefore, an error in the position detection signal output from the PSD 306 can be suppressed, and the scan position of the laser beam in the target area can be detected with high accuracy.

  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 embodiment, PSD is used as a photodetector that receives servo light. However, as shown in FIG. 10, a quadrant sensor 310 may be used as a photodetector. In this case, the servo light is applied to the center position of the four-divided sensor 310 when the mirror 113 is in the neutral position. Further, the X-direction position and the Y-direction position of the beam spot can be obtained from the following equations, for example, when output signals from the sensors are S1, S2, S3, and S4 as shown in the figure.

   FIG. 10 also shows the configuration of an arithmetic circuit that realizes this calculation formula. Signals S1, S2, S3, S4 output from each sensor are amplified by amplifiers 31, 32, 33, 34. The addition circuits 35, 36, 37, and 38 perform operations (S1 + S2), (S3 + S4), (S1 + S4), and (S2 + S3), respectively, and the subtraction circuits 39 and 40 respectively (S1 + S2). -(S3 + S4) and (S1 + S4)-(S2 + S3) are calculated. Further, the addition circuit 41 calculates (S1 + S2 + S3 + S4). The division circuits 42 and 43 respectively divide the left sides of the equations (3) and (4), and the division circuits 42 and 43 indicate the positions where the servo light is received in the x and y directions. A detection signal (output x, y) is output. Further, since the total light quantity does not change, only the difference may be calculated with (S1 + S2) − (S3 + S4) = X and (S1 + S4) − (S2 + S3) = Y.

  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 which shows the structure of the periodic structure which concerns on embodiment The figure explaining the effect | action of the periodic structure which concerns on embodiment The figure which shows the structure of PSD which concerns on embodiment The figure explaining the production | generation method of the position detection signal which concerns on embodiment The figure which shows the measuring method of the verification example which concerns on embodiment The figure which shows the verification result which concerns on embodiment The figure which shows the example of a change of the photodetector which concerns 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 112 Support shaft 113 Mirror 120 Movable frame 130 Fixed frame 200 Transparent body 210 Periodic structure 210a Protrusion 303 Semiconductor laser 306 PSD
310 quadrant sensor

Claims (6)

In a beam irradiation apparatus that scans a laser beam in a target area,
An optical element that changes the traveling direction of the laser light by being rotated in a predetermined direction;
An actuator for rotating the optical element in the direction;
A photorefractive element that is disposed in the actuator and rotates with the rotation of the optical element;
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;
A periodic structure is formed at a pitch equal to or lower than the wavelength band of the servo light on the incident surface and the exit surface of the servo light of the photorefractive element,
A beam irradiation apparatus characterized by that. In claim 1,
The periodic structure consists of a tapered cone.
A beam irradiation apparatus characterized by that. In claim 1 or 2,
The photorefractive element is a flat plate-shaped translucent member.
A beam irradiation apparatus characterized by that. In any one of Claims 1 thru | or 3,
The optical element is a mirror;
A beam irradiation apparatus characterized by that. In any one of Claims 1 thru | or 4,
The actuator is
A first support portion that supports the optical element so as to be rotatable in a first direction;
A second support portion that rotatably supports the first support portion in a second direction different from the first direction;
An electromagnetic drive unit that drives the first support unit and the second support unit in the first direction and the second direction;
A beam irradiation apparatus characterized by that. In any one of Claims 1 thru | or 5,
The photorefractive element is mounted on a rotation shaft that rotates the optical element.
A beam irradiation apparatus characterized by that.

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