JP4489038B2 - Beam irradiation device - Google Patents

Description

  The present invention relates to a beam irradiation apparatus, and is suitable for use in, for example, an inter-vehicle detector, a distance detector, and the like.

  2. Description of the Related Art In recent years, a detection device that detects an obstacle in a target area by irradiating a laser beam is mounted on a domestic passenger car or the like. Such a detection device scans a laser beam in a horizontal direction and a vertical direction within a target area, and detects an obstacle and a distance to the obstacle from a light receiving state of the reflected light.

Such a detection device is provided with a so-called beam irradiation device for scanning a laser beam. Here, the scanning of the laser beam can be performed using, for example, a lens actuator disclosed in Patent Document 1. In this actuator, laser light (diffused light) from the light source is converted into parallel light or light slightly diffused by the scanning lens. The scanning lens is two-dimensionally driven in the direction perpendicular to the optical axis of the laser beam in accordance with the driving of the actuator, thereby scanning the laser beam within the target area.
Japanese Patent Laid-Open No. 11-83988

  In this type of beam irradiation apparatus, generally, the target area is divided into a matrix in the horizontal direction and the vertical direction, and the emission level of the laser beam is pulsed at the timing when the scan position of the laser beam reaches each grid position. The grid position is raised and the laser beam is irradiated. Then, depending on whether the reflected light from the target area is detected at each grid position, the presence or absence of an obstacle at the grid position is detected, and further, based on the time difference between the laser light emission timing and the light reception timing, The distance to the obstacle is detected.

  In this case, the grid resolution affects the obstacle detection accuracy. That is, the higher the grid resolution, the higher the obstacle detection accuracy in the target area. On the other hand, if the resolution of the grid is increased, the frequency of laser light emission increases and the scan control becomes complicated. On the other hand, in a passenger car for home use, it is necessary to increase the detection accuracy in the horizontal direction compared to the detection accuracy in the vertical direction. Therefore, it is desirable to set the grid resolution to be high in the horizontal direction and low in the vertical direction.

  Therefore, an object of the present invention is to provide a beam irradiation apparatus that can irradiate laser light having an appropriate contour shape according to the resolution of the grid.

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

  According to a first aspect of the present invention, a light source that emits laser light, a first lens that receives laser light from the light source, and the first lens are driven in a direction perpendicular to the optical axis of the laser light. A scanning unit that includes an actuator and scans at least the horizontal direction of the laser light emitted from the light source; and an incident surface on which the laser light that has passed through the first lens is incident is perpendicular to a horizontal focal length. A second lens composed of a concave lens with a different focal length in the direction and a spherical exit surface, and the laser beam in the target area is elongated in a direction perpendicular to the horizontal direction. And a beam irradiation device.

  According to the present invention, the contour of the laser beam on the target region is adjusted to be elongated in one direction by the optical action provided by the optical means. Therefore, as described above, even if the resolution of the grid set in the target area changes, it is possible to irradiate the target area with laser light having a contour suitable for the grid shape. Therefore, according to the present invention, an efficient and stable scanning operation can be realized.

  The significance or effect of the present invention will become more apparent from the following description of embodiments.

  The scanning means in the present invention is embodied by the lens actuator 300 in the following embodiments. The optical means in the present invention is embodied by an attachment lens 700 in the following embodiments.

However, the following embodiment is merely an exemplary form of the present invention, and the meaning of the terminology of the present invention or each constituent element is not limited to that described in the following embodiment. Absent.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, FIG. 1 shows a configuration of a beam irradiation apparatus according to the embodiment. In the figure, the head portion (beam irradiation head) of the beam irradiation apparatus is shown, and the configuration of the control circuit is not shown.

  The beam irradiation head includes a semiconductor laser 100, an aperture 200, a lens actuator 300, a beam splitter 400, a servo lens 500, a PSD (Position Sensitive Detector) 600, an attachment lens 700, and an exit window 800. .

  Laser light emitted from the semiconductor laser 100 is shaped into a desired shape by the aperture 200 and then incident on the scanning lens 301. The scanning lens 301 is composed of a double-sided aspherical convex lens, and converges the laser light incident from the semiconductor laser 100 more than the parallel light. The scanning lens 301 is supported by a lens actuator 300 so as to be displaceable in the YZ plane direction of FIG. The emission angle of the laser light that has passed through the scanning lens 301 changes in the YZ plane direction according to the driving of the lens actuator 300. The scanning lens 301 is adjusted by the lens actuator 300 so that the central axis thereof coincides with the central axis of the attachment lens 700 when in the neutral position.

  After passing through the scanning lens 301, a part of the laser light is reflected by the beam splitter 400 and separated from the laser light irradiated to the target area (hereinafter referred to as “irradiated laser light”). The separated laser light (hereinafter referred to as “separated light”) is converged on the PSD 600 via a servo lens (focusing lens) 500.

  The PSD 600 has a light receiving surface parallel to the XY plane of the figure, and outputs a current corresponding to the convergence position of the separated light on the light receiving surface. Here, the convergence position of the separated light on the light receiving surface and the irradiation position of the irradiation laser light on the target area have a one-to-one correspondence. Therefore, the current output from the PSD 60 corresponds to the irradiation position of the irradiation laser light on the target area.

  This current signal is processed by a signal processing circuit (not shown), and the irradiation position of the irradiation laser beam is detected. Based on the detection result, scan control of the irradiation laser light is performed. The configuration of the PSD 600 and the current output operation will be described in detail later with reference to FIGS.

  The irradiated laser light that has passed through the beam splitter 400 is incident on the attachment lens 700. The attachment lens 700 is composed of a concave lens whose incident surface is a toroidal surface and whose exit surface is a spherical surface, and converts irradiated laser light incident as convergent light into substantially parallel light. The irradiated laser light converted into parallel light by the attachment lens 700 passes through the emission window 800 and is irradiated onto the target area. As will be described later, the focal length in the horizontal direction (z-axis direction in FIG. 1) is different from the focal length in the vertical direction (y-axis direction in FIG. 1).

  FIG. 2 shows a configuration (disassembled perspective view) of the lens actuator 300.

  With reference to the figure, the scanning lens 301 is attached to the central opening of the lens holder 302. The lens holder 302 is provided with coils on four side surfaces, and a protrusion at the center of the yoke 303 is inserted into each coil as shown by the arrows in the drawing. As for each yoke 303, the tongue piece of both sides is inserted in the recessed part of a pair of yoke fixing member 305. FIG. Further, the magnet 304 is fixed to each yoke fixing member 305 so as to sandwich the tongue piece of the yoke 303. In this state, the yoke fixing member 305 is attached to the base (not shown) together with the magnet 304.

  Further, a pair of wire fixing members 306 are attached to the base, and the lens holder 302 is elastically supported by the wire fixing members 306 via the wires 307. The lens holder 302 has holes for fitting the wires 307 at the four corners. After the wires 307 are inserted into the holes, both ends of the wire 307 are fixed to the wire fixing member 306. As a result, the lens holder 302 is elastically supported by the wire fixing member 306 via the wire 307.

  At the time of driving, a driving signal is supplied from the actuator driving circuit to each coil mounted on the lens holder 302. Thereby, an electromagnetic driving force is generated, and the scanning lens 301 is two-dimensionally driven together with the lens holder.

  FIG. 3 shows the structure of the PSD 600. This figure shows the structure of the PSD 600 in FIG. 1 when viewed from the Y-axis direction.

  As shown in the figure, PSD 600 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. Electrodes X1 and X2 for outputting photocurrent in the X direction in FIG. 1 and electrodes Y1 and Y2 (not shown in the figure) for outputting photocurrent in the Y direction in FIG. 1 are provided on the resistance layer surface. Is formed. A common electrode is formed on the back side.

  When the separated light is converged on the light receiving surface, an electric charge proportional to the amount of light is generated at the convergence 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 convergence position of the separated light to each electrode. Therefore, the convergence position on the light receiving surface can be detected based on the current values output from the electrodes X1, X2, Y1, and Y2.

  FIG. 4A is a diagram showing an effective light receiving surface of the PSD 600. 4B shows the position detection voltage generated by the PSD signal processing circuit 60 based on the currents output from the electrodes X1, X2, Y1, and Y2, and the convergence of the separated light on the effective light receiving surface. It is a figure which shows the relationship of a position. In FIG. 4A, the effective light receiving surface is a square. FIG. 4B shows the relationship between the amount of displacement in the X and Y directions of the convergence position with respect to the reference position and the output voltage, with the center position of the effective light receiving surface as the reference position (0 position).

  The signal processing circuit generates a voltage Xout corresponding to the X-direction displacement amount of the convergence position and a voltage Yout corresponding to the Y-direction displacement amount based on the currents output from the electrodes X1, X2, Y1, and Y2. The data is output to a DSP (Digital Signal Processor) control circuit via an ADC (Analog Digital Converter). The DSP control circuit detects the X-direction displacement amount and the Y-direction displacement amount of the convergence position from the input voltages Xout and Yout.

  In the present embodiment, as described above, the incident surface of the attachment lens 700 is a toroidal surface, so that the beam spot on the target region is deformed into an elongated shape in the vertical direction (y-axis direction in FIG. 1).

  5 to 7 are simulations of the beam intensity on the target area when the following conditions are set in the optical system of FIG. Here, the target area is set 100 m away from the attachment lens 700.

<Scanning lens 301>
Double-sided aspheric focal length: 13.4912 mm
Effective diameter: Φ16 mm (Aperture)
Center thickness: 5 mm
Refractive index: 1.517
<Attachment lens 700>
Incident side: Toroidal surface / Outgoing side: spherical Focal length: Horizontal -23.0359 mm, Vertical -20.9278 mm
Effective diameter: Φ14.0 mm
Center thickness: 1 mm
Refractive index: 1.517
<Others>
Distance from laser diode to attachment lens: 52.81 mm
Scan lens displacement: ± 2 mm

  Note that the scanning lens 301 and the attachment lens 700 have laser beams emitted from the attachment lens 700 in the horizontal direction when the center axes of the two lenses coincide, that is, when the scanning lens 301 is in the neutral position (see FIG. 1 in the z-axis direction), and the beam diameter (according to the ray tracing method) is an abbreviation of the beam diameter (also according to the ray tracing method) when entering the scanning lens 301 in the horizontal direction. It is assumed that it is arranged at a position that becomes 1/2.

  5 to 7 show the beam intensity distribution (left) when the irradiation direction of the irradiation laser light is swung by a predetermined angle in the horizontal direction by displacing the scanning lens 301 in the horizontal direction (z-axis direction in FIG. 1). The figure shows a beam profile (middle figure) in the horizontal direction (left and right direction in the drawing) and a beam profile (right figure in the vertical direction (up and down direction)) for each beam intensity distribution. The horizontal axis of the beam profile is the distance from the beam center position (the position where the beam intensity is highest), and the vertical axis is the intensity level when the maximum intensity is 100. The horizontal axis is set so that the beam center position becomes zero.

  As can be seen with reference to FIGS. 5 to 7, by making the incident surface of the attachment lens 700 a toroidal surface, the beam shape of the irradiated laser light can be elongated in the vertical direction (y-axis direction in FIG. 1). . As a result, the cover range of the irradiation laser beam in the vertical direction can be expanded. Therefore, when this configuration is used for an obstacle detection apparatus, as shown in FIG. 8B, the number of scan stages in the vertical direction in the target area (the number of block stages when the target area is divided into a matrix) is reduced. be able to. FIG. 8A is a diagram illustrating a beam shape and a division state of the target region when both the incident surface and the exit surface of the attachment lens 700 are spherical surfaces.

  The attachment lens 700 according to the simulation conditions can be formed based on the following lens data.

<Scanning lens 301>
a. Incident surface (aspheric surface)
・ Curvature radius 16.8777649771835 mm
-Aspheric coefficient (aspheric generator polynomial):
Conic constant (K) −8.48832199279343
Fourth-order coefficient (A) −4.27096033316007e-007
6th order coefficient (B) 1.17521904684828e-006
8th order coefficient (C) -2.111559547426e-008
b. Output surface (aspheric surface)
・ Curvature radius −10.4603963534906 mm
-Aspheric coefficient (aspheric generator polynomial):
Conic constant (K) 0.0947470811575341
Fourth-order coefficient (A) 7.4254388113816e-005
6th order coefficient (B) 2.33700944147862e-006
8th order coefficient (C) -1.55061157703029e-008
c. Material: Glass / BK7 (refractive index = 1.517)
<Attachment lens 701>
a. Incident surface (toroidal surface)
·curvature radius:
Horizontal direction −60.16068895769 mm
Vertical direction −40 mm
b. Output surface (spherical surface)
・ Curvature radius 14.68847686175 mm
c. Material Glass / BK7 (refractive index = 1.517)

  By the way, as can be seen with reference to FIGS. 5 to 7, when the scanning lens 301 is displaced in a direction perpendicular to the optical axis of the laser light in order to scan the laser light in the target area, the irradiated laser light on the target area Aberration occurs. For example, in the case of following the above simulation conditions, the state of occurrence of aberration becomes conspicuous after the irradiation laser beam is scanned about 15 ° in the horizontal direction from the neutral position, and the intensity distribution of the irradiation laser beam is distorted in the horizontal direction. It will be in a state (refer to Drawing 6 (b)). Furthermore, when the scanning angle is about 20 °, the distortion of the intensity distribution becomes considerably large (see FIG. 7). Such distortion also occurs when the irradiated laser beam is scanned in the vertical direction.

  However, in an in-vehicle beam irradiation apparatus, generally, the swing angle of laser light required for monitoring the front of the vehicle is about ± 10 degrees, and thus aberration is conspicuous when the swing angle is in the range of ± 10 degrees. If it does not increase, there will be no problem in the accuracy of the distance detection operation. Therefore, when the optical system is designed under the simulation conditions, a scan operation without any problem can be realized.

  According to the present embodiment, in addition to the above effects, the effect that the swing angle of the laser light in the horizontal and vertical directions can be expanded by the optical action of the attachment lens 700 can be achieved.

  FIG. 9A shows a simulation of the fluctuation of the irradiated laser beam by the ray tracing method when the scanning lens 301 is displaced in the direction of arrow A in FIG. FIG. 9B shows a simulation of the fluctuation of the separated light when the scanning lens 301 is displaced in the same direction (arrow A direction) as that in FIG. In FIG. 9B, only the locus of laser light incident on the servo lens 500 is shown for convenience.

  As shown in FIG. 5A, by moving the scanning lens 301, the traveling direction of the irradiation laser light immediately after passing through the scanning lens is bent by a predetermined angle. Thereafter, the irradiation laser light passes through the attachment lens 700, and the traveling direction thereof is further bent by a predetermined angle in the same direction. Therefore, the deflection angle of the irradiation laser light finally emitted from the emission window 800 becomes larger by the amount of the deflection angle provided by the attachment lens 700 than in the case where the attachment lens 700 is not provided. Since the attachment lens 700 is composed of a concave lens whose entrance surface is a toroidal surface and whose exit surface is a spherical surface, the effect of increasing the deflection angle (wide-angle action) is the entire circumference of the attachment lens 700. Occurs in the direction.

  FIG. 10 shows a simulation result when the relationship between the horizontal movement amount of the scanning lens 301 and the scanning angle of the irradiation laser light is simulated under the same conditions as those set in the simulation. The scanning angle on the vertical axis is an angle between the optical axis of the laser light emitted from the semiconductor laser 100 and the optical axis of the laser light when emitted from the emission window 800. In addition, in the figure, as a comparative example, the relationship between the amount of movement of the scanning lens 301 and the scanning angle when the attachment lens 700 is omitted is shown.

  As shown in the figure, according to the present embodiment, it is possible to obtain a scanning angle approximately twice as large at each scanning lens position as compared with the comparative example. In other words, according to the present embodiment, the irradiation laser light can be scanned with a large swing angle even if the scanning lens 301 is displaced small.

  In the present embodiment, the beam diameter of the laser light emitted from the attachment lens 700 (by the ray tracing method) is 1 / of the beam diameter (also by the ray tracing method) when entering the scanning lens 301. When the conditions of the optical system are set so as to be n, it is possible to scan the irradiation laser light with a deflection angle n times that of the comparative example.

  Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments, and various other modifications are possible.

  For example, in the above-described embodiment, the incident surface of the attachment lens 700 is a toroidal surface, but it can be a cylindrical surface instead. In this case, it is necessary to adjust the direction of the cylindrical surface so that the beam shape is elongated in a desired direction in the target region. In addition, it is necessary to design the surface shape of the cylindrical surface (incident surface) and the surface shape of the spherical surface (exit surface) so that the beam size becomes a desired size in the target region.

  In the above embodiment, the beam shape is adjusted by devising the incident surface of the attachment lens 700, but a lens for adjusting the beam shape may be added to the optical system separately. However, in this case, the number of parts increases and the cost increases.

  Furthermore, in the above-described embodiment, the lens actuator 300 is used as the beam scanning unit. However, as shown in FIG. 11, the polygon mirror 900 can be used to scan the beam.

  Here, the polygon mirror 900 has a polygonal cross section, and a mirror surface is formed on each side surface. Polygon mirror 900 receives a driving force from a motor (not shown) and is rotated in the direction of the arrow in FIG. When laser light is irradiated on the side surfaces while rotating the polygon mirror 900, the incident angle of the laser light on each side surface changes. Thereby, the laser beam (irradiation laser beam) reflected by the side surface of the polygon mirror 900 is scanned in the rotation direction of the polygon mirror.

  Here, in the polygon mirror 900, the horizontal scan trajectory is shifted by one block in the vertical direction on the target area as the incident position of the laser beam moves from one mirror surface to the next mirror surface. As described above, the inclination angle of each mirror surface with respect to the rotation axis is adjusted. Also, the tilt angle of the mirror surface is such that when the horizontal scan trajectory is at the lowest block position, the horizontal scan trajectory will change accordingly when the incident position of the laser beam moves to the next mirror surface. Also, adjustment is made to shift from the lowermost block position to the uppermost block position.

  Since the tilt angle of the mirror surface of the polygon mirror 900 is adjusted in this way, the irradiation laser light moves, for example, from the left to the right in the irradiation block shown in FIG. 8B according to the rotation of the polygon mirror 900. Scan one step at a time.

  In this case, the beam splitter 400, the servo lens 500, and the PSD 600 in FIG. 1 can be omitted. This is because the irradiation position of the laser beam can be detected from the rotational position of the polygon mirror 900. That is, in the configuration example of FIG. 11, for example, the rotational position of the polygon mirror 900 is sequentially detected based on the rotation synchronization signal output from the motor. Based on the detected rotational position, the irradiation position of the irradiation laser light on the target area is detected.

  The present invention can be applied to a beam irradiation apparatus for various uses other than in-vehicle use. In addition to the obstacle detection device and the distance detection device, it can be mounted on an image reading device or the like.

  The embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

The figure which shows the structure of the beam irradiation apparatus which concerns on embodiment The figure which shows the structure of the lens actuator which concerns on embodiment The figure which shows the structure of PSD which concerns on embodiment The figure explaining the structure and voltage characteristic of PSD which concern on embodiment Simulation result of intensity distribution of laser beam according to embodiment Simulation result of intensity distribution of laser beam according to embodiment Simulation result of intensity distribution of laser beam according to embodiment The figure explaining the irradiation state of the laser beam which concerns on embodiment Simulation results obtained by the ray tracing method for the fluctuation of the irradiation laser beam and the separated light when the scanning lens 301 according to the embodiment is displaced in one direction The figure which shows the relationship between the moving amount of the scanning lens and scanning angle which concern on embodiment The figure which shows the other structural example of the beam irradiation apparatus which concerns on embodiment

Explanation of symbols

300 Lens actuator 301 Scan lens 700 Attachment lens 900 Polygon mirror

Claims (1)

A light source that emits laser light;
A first lens on which the laser light from the light source is incident; and an actuator for driving the first lens in a direction perpendicular to the optical axis of the laser light, the laser light emitted from the light source being a target region Scanning means for scanning in the horizontal direction at least
A second lens composed of a concave lens in which the incident surface on which the laser light that has passed through the first lens is incident is a toroidal surface having a horizontal focal length and a vertical focal length different from each other, and the emission surface is a spherical surface. comprising an optical means for elongated deforming the laser beam in the target area in a direction perpendicular to the contour to the horizontal direction,
A beam irradiation apparatus comprising:

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