This application claims priority under 35 U.S.C. Section 119 of Japanese Patent Application No. 2009-54152 filed Mar. 6, 2009, entitled “BEAM IRRADIATION DEVICE AND POSITION DETECTING DEVICE”. The disclosure of the above application is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a beam irradiation device for irradiating laser light onto a targeted area, and more particularly to a beam irradiation device to be loaded in a laser radar system. The present invention also relates to a position detecting device for optically detecting a moved position of a moving section using servo light.
2. Disclosure of Related Art
In recent years, a laser radar system for irradiating laser light in a forward direction with respect to a driving direction to detect presence or absence of an obstacle or a distance to the obstacle in a targeted area, based on a state of reflection light of the laser light, has been loaded in a family automobile or the like to enhance security in driving. Generally, the laser radar system is so configured as to scan a targeted area with laser light to detect presence or absence of an obstacle at each of scanning positions, based on presence or absence of reflection light at each of the scanning positions. The laser radar system is also configured to detect a distance to the obstacle at each of the scanning positions, based on a required time from an irradiation timing of laser light to a light receiving timing of reflection light at each of the scanning positions.
It is necessary to properly scan a targeted area with laser light, and properly detect each of scanning positions of laser light to enhance detection precision of the laser radar system. Heretofore, there have been known scan mechanisms using laser light, such as a scan mechanism incorporated with a polygon mirror, and a scan mechanism incorporated with a scanning lens to be driven two-dimensionally. In addition, there has also been known a scan mechanism incorporated with a pivotal mirror for making laser light to scan a scanning area.
In the scan mechanism incorporated with a pivotal mirror, the mirror is supported to be driven about two axes, and the mirror is pivotally moved about the respective drive axes by an electromagnetic driving force between a coil and a magnet. Laser light is entered into the mirror in an oblique direction, and the mirror is driven about each of the two drive axes, whereby reflection light of laser light from the mirror scans a targeted area in a two-dimensional direction.
In the scan mechanism having the above arrangement, a scanning position of laser light in a targeted area has a one-to-one correspondence to a pivotal position of the mirror. Accordingly, the scanning position of laser light can be detected by detecting the pivotal position of the mirror. In the above arrangement, the pivotal position of the mirror can be detected by e.g. detecting a pivotal position of another member which is pivotally moved with the mirror.
However, in the arrangement shown in
A first aspect of the invention is directed to a beam irradiation device. The beam irradiation device according to the first aspect includes: a laser light source which emits laser light; an actuator which pivotally moves an optical element into which the laser light is entered to thereby scan a targeted area with the laser light; a servo light source which emits servo light; a transparent member which is pivotally moved with the pivotal movement of the optical element, and into which the servo light is entered; a photodetector which receives the servo light transmitted through the transparent member to output a signal depending on a light receiving position of the servo light; and a diffracting portion which is pivotally moved with the transparent member, and diffracts the servo light in a pivotal direction of the transparent member.
A second aspect of the invention is directed to a position detecting device for detecting a pivotal position of an object. The position detecting device according to the second aspect includes: a servo light source which emits servo light; a transparent member which is pivotally moved with a pivotal movement of the object, and into which the servo light is entered; a photodetector which receives the servo light transmitted through the transparent member to output a signal representing a light receiving position of the servo light; and a diffracting portion which is pivotally moved with the transparent member, and diffracts the servo light in a pivotal direction of the transparent member.
These and other objects, and novel features of the present invention will become more apparent upon reading the following detailed description of the embodiment along with the accompanying drawings.
The drawings are provided mainly for describing the present invention, and do not limit the scope of the present invention.
Referring to
As described above, the hologram element 200 of a parallel flat plate shape is mounted on the support shaft 112 through the bracket portion 112a. In this example, the hologram element 200 is mounted on the support shaft 112 in such a manner that two flat surfaces of the hologram element 200 are aligned in parallel to a mirror surface of the mirror 113.
The reference numeral 120 indicates a movable frame which pivotally supports the mirror holder 110 about axes of the support shafts 111 and 112. The movable frame 120 is formed with an opening 121 for accommodating the mirror holder 110 therein. The movable frame 120 is also formed with grooves 122 and 123 to be engaged with the support shafts 111 and 112 of the mirror holder 110. Support shafts 124 and 125 each having a retainer at an end thereof are formed on side surfaces of the movable frame 120, and a coil 126 is mounted on a rear surface of the movable frame 120. The coil 126 is wound in a rectangular shape.
The reference numeral 130 indicates a fixed frame which pivotally supports the movable frame 120 about axes of the support shafts 124 and 125. The fixed frame 130 is formed with a recess 131 for accommodating the movable frame 120 therein. The fixed frame 130 is also formed with grooves 132 and 133 to be engaged with the support shafts 124 and 125 of the movable frame 120. Magnets 134 for applying a magnetic field to the coil 114, and magnets 135 for applying a magnetic field to the coil 126 are mounted on inner surfaces of the fixed frame 130. The grooves 132 and 133 each extends from a front surface of the fixed frame 130 to a position in a clearance between the upper and lower two magnets 135.
The reference numeral 140 indicates a pressing plate for pressing the support shafts 111 and 112 in a rearward direction to prevent the support shafts 111 and 112 of the mirror holder 110 from disengaging from the grooves 122 and 123 of the movable frame 120. The reference numeral 141 indicates a pressing plate for pressing the support shafts 124 and 125 in the rearward direction to prevent the support shafts 124 and 125 of the movable frame 120 from disengaging from the grooves 132 and 133 of the fixed frame 130.
In the case where the mirror actuator 100 is assembled, the support shafts 111 and 112 of the mirror holder 110 are engaged in the grooves 122 and 123 of the movable frame 120, and the pressing plate 140 is mounted on a front surface of the movable frame 120 in such a manner as to press front surfaces of the support shafts 111 and 112. Accordingly, the mirror holder 110 is pivotally supported on the movable frame 120.
After the mirror holder 110 is mounted on the movable frame 120 in the above-described manner, the support shafts 124 and 125 of the movable frame 120 are engaged in the grooves 132 and 133 of the fixed frame 130, and the pressing plate 141 is mounted on the front surface of the fixed frame 130 in such a manner as to press front surfaces of the support shafts 132 and 133. Accordingly, the movable frame 120 is pivotally mounted on the fixed frame 130. Thus, the mirror actuator 100 is assembled.
As the mirror holder 110 is pivotally rotated with respect to the movable frame 120 about the axes of the support shafts 111 and 112, the mirror 113 is pivotally rotated. Further, as the movable frame 120 is pivotally rotated with respect to the fixed frame 130 about the axes of the support shafts 124 and 125, the mirror holder 110 is pivotally rotated, and as a result, the mirror 113 is pivotally rotated with the mirror holder 110. Thus, the mirror holder 110 is pivotally supported in a two-dimensional direction about the axes of the support shafts 111 and 112, and the support shafts 124 and 125 orthogonal to each other, and the mirror 113 is pivotally rotated in the two-dimensional direction in accordance with the pivotal rotation of the mirror holder 110. During the pivotal rotation, the hologram element 200 mounted on the support shaft 112 is also pivotally rotated in accordance with the pivotal rotation of the mirror 113.
In the assembled state shown in
Further, in the assembled state shown in
Referring to
An optical system 400 for guiding laser light to the mirror 113 is mounted on a top surface of the base plate 500. The optical system 400 includes a laser light source 401, and lens 402 and 403 for beam shaping. The laser light source 401 is mounted on a substrate 401a for a laser light source, and the substrate 401a is provided on the top surface of the base plate 500.
Laser light emitted from the laser light source 401 is subjected to convergence in a horizontal direction and a vertical direction by the lenses 402 and 403, respectively. The lenses 402 and 403 are designed in such a manner that the beam shape in a targeted area (e.g. an area defined at a position 100 m away in a forward direction from a beam exit port of a beam irradiation device) has predetermined dimensions (e.g. dimensions of about 2 m in the vertical direction and 1 m in the horizontal direction).
The lens 402 is a cylindrical lens having a lens function in the vertical direction, and the lens 403 is an aspherical lens for emitting laser light as substantially parallel light. A beam emitted from a laser light source has different divergence angles from each other in the vertical direction and the horizontal direction. The first lens 402 changes a ratio between divergence angles of laser light in the vertical direction and the horizontal direction. The second lens 403 changes magnifications of divergence angles (both in the vertical direction and the horizontal direction) of an emitted beam.
Laser light transmitted through the lenses 402 and 403 is entered into the mirror 113 of the mirror actuator 100, and reflected on the mirror 113 toward a targeted area. The targeted area is scanned in the two-dimensional direction with the laser light when the mirror 113 is two-dimensionally driven by the mirror actuator 100.
The mirror actuator 100 is disposed at such a position that laser light from the lens 403 is entered into the mirror surface of the mirror 113 at an incident angle of 45 degrees with respect to the horizontal direction, when the mirror 113 is set to a neutral position. The term “neutral position” indicates a position of the mirror 113, wherein the mirror surface is aligned in parallel to the vertical direction, and laser light is entered into the mirror surface at an incident angle of 45 degrees with respect to the horizontal direction.
A circuit board 300 is provided underneath the base plate 500. Further, circuit boards 301 and 302 are provided on a back surface and a side surface of the base plate 500.
As shown in
A light collecting lens 304, an aperture 305, and a ND (neutral density) filter 306 are mounted on the flat surface 503 on the back surface of the base plate 500 by an attachment member 307. The flat surface 503 is formed with an opening 503a, and the hologram element 200 mounted on the mirror actuator 100 is projected from the back surface of the base plate 500 through the opening 503a.
The hologram element 200 is set to such a position that the two flat surfaces of the hologram element 200 are aligned in parallel to the vertical direction, and are inclined with respect to an optical axis of emission light from the semiconductor laser 303 by 45 degrees, when the mirror 113 of the mirror actuator 100 is set to the neutral position. Further, a blazed diffraction pattern for diffracting servo light in plus direction (upward direction) of X-axis in an in-plane direction of X-Z plane, when the mirror 113 is set to the neutral position, is integrally formed on the exit surface of the hologram element 200.
Laser light (hereinafter, called as “servo light”) emitted from the semiconductor laser 303 transmitted through the light collecting lens 304 has the beam diameter thereof reduced by the aperture 305, and has the light intensity thereof reduced by the ND filter 306. Further, the servo light is converted into parallel light by the collimator lens 308, and then, entered into the hologram element 200.
Servo light to be entered into the hologram element 200 is refracted and diffracted by the hologram element 200, as will be described later. Accordingly, plus first-order light of servo light generated by the refraction function and the diffraction function is emitted from the hologram element 200 in a state that the propagating direction thereof is changed, as shown in
Servo light to be entered into the hologram element 200 is at first refracted on an incident surface of the hologram element 200. Then, the refracted servo light is diffracted and refracted on an exit surface of the hologram element 200. Specifically, servo light is divided into zero-order light (not shown), and plus first-order light diffracted in plus direction (upward direction) of X-axis on the exit surface of the hologram element 200 by the aforementioned diffraction pattern. Simultaneously, the zero-order light and the plus first-order light are respectively refracted on the exit surface of the hologram element 200, and emitted from the exit surface of the hologram element 200. As a result of the above operation, the plus first-order light is emitted from the hologram element 200 in a state that the propagating direction thereof in plus direction (upward direction) of X-axis is further changed, as compared with the servo light before incidence into the hologram element 200.
The diffraction efficiency and the diffraction angle of the hologram element 200 are respectively determined by the blaze height and the pitch width of the diffraction pattern. Accordingly, it is necessary to set the positions of the diffraction pattern and the optical system in advance so that only the plus first-order light is properly received on the PSD 309. Further, it is desirable to set the diffraction pattern of the hologram element 200 in such a manner that the diffraction efficiency of plus first-order light is maximized. The above arrangement enables to obtain a position detection signal of high precision, because the light amount of plus first-order light to be received on the PSD 309 is increased.
Referring to
When laser light is irradiated onto the light receiving surface of the substrate, an electric charge proportional to a light amount is generated at an irradiated position on the light receiving surface. The electric charge is received by the resistive layer as a photocurrent, and the photocurrent is divided in inverse proportion to a distance to the respective corresponding electrodes, and outputted from the electrodes X1, X2, Y1, and Y2. In this example, currents to be outputted from the electrode X1, X2, Y1, and Y2 each has a magnitude obtained by dividing a photocurrent in inverse proportion to a distance from the laser light irradiated position to the respective corresponding electrodes. Thus, the light irradiated position on the light receiving surface can be detected, based on current values to be outputted from the electrodes X1, X2, Y1, and Y2.
For instance, let it be assumed that plus first-order light is irradiated to a position P in
where Ix1, Ix2, Iy1, and Iy2 are amounts of current to be outputted from the electrodes X1, X2, Y1, and Y2, respectively, and Lx and Ly are distances between the electrodes in X direction and Y direction, respectively.
As shown in
In the servo optical system 1, as described above, after the servo light emitted from the semiconductor laser 303 is refracted and diffracted by the hologram element 200, the plus first-order light is entered into the light receiving surface of the PSD 309. Accordingly, current signals (current signals to be outputted from the electrodes X1, X2, Y1, and Y2 shown in
The I/V conversion circuit 2 converts the inputted current signals into voltage signals, and outputs the voltage signals to the PSD signal processing circuit 3. The PSD signal processing circuit 3 generates a signal representing a light receiving position of the plus first-order light based on the inputted voltage signals by the computations described referring to
The DSP control circuit 5 detects a scanning position of laser light within a targeted area, based on the inputted position detection signal representing a light receiving position of the plus first-order light, controls driving of the mirror actuator 100, and executes e.g. drive-control of a laser light source 401.
Specifically, the DSP control circuit 5 outputs, to the scan laser driving circuit 9 through the D/A conversion circuit 8, a pulse drive signal at a timing when a scanning position of laser light within a targeted area reaches a predetermined position. Accordingly, the laser light source 401 emits pulse light to irradiate the laser light onto the targeted area. Further, the DSP control circuit 5 outputs, to the actuator driving circuit 11 through the D/A conversion circuit 10, a servo signal for tracing the scanning position of laser light within the targeted area along a predetermined trajectory. In response to receiving the servo signal, the actuator driving circuit 11 drives the mirror actuator 100 to scan the targeted area in such a manner that the laser light follows the predetermined trajectory.
Further, the DSP control circuit 5 outputs a control signal to the servo laser driving circuit 7 through the D/A conversion circuit 6. Accordingly, the semiconductor laser 303 in the servo optical system 1 constantly emits light at a predetermined power level.
In the case of
Δd0=d0′−d0 (3)
Next, in the case of
In the case of
Accordingly, a varied amount Δd1 of the incident position on the light receiving plane in X-axis direction, in the case where the hologram element 200 is pivotally moved from the state shown in
Δd1=(d0′−d0)+(α′−α)=Δd0+(α′−α) (4)
where α is a difference between d1 and d0, and α′ is a difference between d1′ and d0′.
In this example, referring to
As described above, according to the embodiment, since the scan width of servo light (plus first-order light) in X-axis direction is increased, the resolution performance at a scanning position in X-axis direction can be enhanced. Accordingly, detection precision on a light receiving position of servo light in X-axis direction can be enhanced. Further, even if the thickness of the hologram element 200 is small, the pivotal position of the hologram element 200 can be detected substantially with the same precision as in a case of using a transparent member having a large thickness. Accordingly, the embodiment enables to precisely detect a scanning position of laser light within a targeted area, using the lightweight and thin hologram element 200.
The beam irradiation device in the embodiment is suitably applied to e.g. a laser radar system to be loaded in a vehicle. Normally, a targeted area in a laser radar system to be loaded in a vehicle has a longer size in the horizontal direction, and it is necessary to accurately detect an irradiated position of scanning laser light in the horizontal direction. Accordingly, in the case where the beam irradiation device of the embodiment is mounted in a laser radar system to be loaded in a vehicle, as shown in
The embodiment of the invention has been described as above. The invention, however, is not limited to the embodiment, and may be modified in various ways other than the above.
For instance, a semiconductor laser is used as a light source for servo light in the embodiment. Alternatively, an LED (Light Emitting Diode) may be used in place of the semiconductor laser.
The hologram element 200 integrally formed with a blazed diffraction pattern is used in the embodiment. Alternatively, as shown in
Similarly to the embodiment, in the above modification, the hologram element 220 is integrally formed with a diffraction pattern for diffracting incident servo light in an in-plane direction of X-Z plane. Further, the servo light is divided into zero-order light, plus first-order light, and minus first-order light by the hologram element 220. Since the diffraction efficiency and the diffraction angle are respectively determined by the step height and the pitch width of the diffraction pattern, the positions of the diffraction pattern and the optical system may be set in advance in such a manner that plus first-order light is properly entered into the PSD 309.
Further alternatively, as shown in
Similarly to the embodiment, in the above modification, the hologram element 222 has a diffraction pattern for diffracting incident servo light in an in-plane direction of X-Z plane. Accordingly, servo light to be entered into the transparent member 221 has its propagating direction changed by a refraction function of the transparent member 221, and refracted and diffracted by the hologram element 222. Servo light is divided into zero-order light (not shown) and plus first-order light by the diffraction function, and the plus first-order light is received by the PSD 309. As a result of the above operation, substantially the same effect as the embodiment can be obtained, although the number of parts is increased, as compared with the embodiment.
Further alternatively, as shown in
In the arrangements of the embodiment and
The PSD 309 is used as a photodetector for receiving servo light in the embodiment. Alternatively, a four-division sensor may be used in place of the PSD 309.
where S1, S2, S3, and S4 are output signals from sensing portions of the four-division sensor 310, as shown in
In the above modification, signals (current signals) from the sensing portions may also be converted into voltage signals by I/V conversion, and position detection signals representing a light receiving position may be generated based on the voltage signals after I/V conversion by computations substantially equivalent to the foregoing computations.
The hologram element 200 for diffracting servo light only in X-axis direction is used in the embodiment. Alternatively, it is possible to use a hologram element for diffracting servo light in Y-axis direction as well as in X-axis direction. In the modification, for instance, a diffraction pattern substantially the same as the aforementioned diffraction pattern is formed on the exit surface of the hologram element, and a diffraction pattern for diffracting servo light in Y-axis direction is formed on the incident surface of the hologram element. Further alternatively, another hologram element having a diffraction pattern for diffracting servo light in Y-axis direction may be integrally formed with the hologram element 200. The modification enables to enhance detection precision of servo light in Y-axis direction in addition to X-axis direction, because the scan width of servo light is increased in Y-axis direction as well as X-axis direction.
In the foregoing embodiment, described is a beam irradiation device for scanning a targeted area with laser light by pivotally moving a mirror. The invention is also applicable to a beam irradiation device for scanning a targeted area with laser light by pivotally moving a lens into which laser light is entered.
The optical system for use in position detection, as described in the embodiment and the modifications, is applicable to various detecting devices for detecting a pivotal position of an object which is pivotally moved about a predetermined axis, as necessary, other than the aforementioned beam irradiation device. In the modification, for instance, the hologram element is directly mounted on an object whose pivotal position is to be detected, or the hologram element is mounted on the object through an interconnecting member which is pivotally movable with a pivotal movement of the object. A light source for servo light is disposed at such a position that servo light is entered into the hologram element, and servo light transmitted through the hologram element is received on a PSD. Accordingly, in the similar manner as described in the embodiment and the modifications, the above modification enables to increase a scan width of servo light at the time of pivotally moving the object to thereby precisely detect a pivotal position of the object.
The embodiment of the invention may be changed or modified in various ways as necessary, as far as such changes and modifications do not depart from the scope of the present invention hereinafter defined.
Number | Date | Country | Kind |
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2009-54152 | Mar 2009 | JP | national |