JP2018197680A - Distance measuring device and scanning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance measuring device capable of improving reception intensity.
A distance measuring device includes a light emitting element that emits laser light, a scanning element that projects laser light emitted from the light emitting element at a first emission angle, and a target that is reflected by an object. A light receiving element 16 for detecting the laser light, and an angle limiting element 15 for limiting the laser light incident on the light receiving element 16 to the laser light incident at the incident angle of the first angle.
[Selection] Figure 1

Description

  The present invention relates to a distance measuring apparatus and a scanning method for measuring the position of an object by scanning a laser beam.

  A distance measuring device called LIDAR (Light Detection and Ranging) is known. The LIDAR is a sensor that optically measures a distance from a surrounding object. LIDAR irradiates a target with pulsed laser light and measures the distance from the round trip time until the laser light reflected by the target returns. Recently, LIDAR has been used for Advanced Driving Assistant System (ADAS) and automatic driving.

  LIDAR includes a coaxial optical system, a separation optical system, and a CCD / CMOS image sensor system.

  Polygon mirrors (Patent Document 1) and MEMS mirrors (Patent Document 2) used in the coaxial optical system have a movable part, so there is a concern about long-term reliability due to vehicle vibration. Further, since the polygon mirror and the MEMS mirror are optical parts, the cost is increased.

  In the separation optical system method, a method of changing the light emission angle by electrically changing the phase has been proposed (Patent Documents 3 and 4). This configuration has no moving parts and may be manufactured at a lower cost, but there is a concern about the measurement distance. As a factor that shortens the measurement distance, the intensity of disturbance light such as sunlight is increased with respect to the laser light that is a signal among the light incident on the photodiode, that is, the signal-to-noise ratio. ). When the S / N ratio decreases, it is impossible to receive and detect signals with high accuracy.

JP 2010-38859 A JP 2009-216789 A International Publication No. 2014/110017 International Publication No. 2016/022220

  The present invention provides a distance measuring device and a scanning method capable of improving reception intensity.

  A distance measuring device according to one embodiment of the present invention is a light-emitting element that emits laser light, a scanning element that projects laser light emitted from the light-emitting element at an emission angle of a first angle, and is reflected by an object. A light receiving element for detecting the laser light, and an angle limiting element for limiting the laser light incident on the light receiving element to the laser light incident at the incident angle of the first angle.

  In the scanning method according to one aspect of the present invention, the step of projecting the laser beam at the first angle of emission and the laser beam incident on the light receiving element are limited to the laser beam incident at the incident angle of the first angle. The process to comprise.

  According to the present invention, it is possible to provide a distance measuring device and a scanning method capable of improving reception intensity.

1 is a block diagram of a distance measuring device according to a first embodiment of the present invention. The schematic diagram which shows the structure of a light projection part. The schematic diagram which shows the structure of a light-receiving part. The top view of a scanning element and an angle limiting element. FIG. 5 is a cross-sectional view of the scanning element along line AA ′ in FIG. 4. Sectional drawing of the angle limiting element along the BB 'line | wire of FIG. Schematic explaining the basic operation of the distance measuring device. The figure explaining the waveform of the laser beam by a distance measuring device. The flowchart explaining operation | movement of a distance measuring device. The schematic diagram which shows the structure of the light projection part which concerns on an Example. The schematic diagram which shows the structure of the light-receiving part which concerns on an Example. The top view of the scanning element and angle limit element which concern on 2nd Embodiment of this invention. FIG. 13 is a cross-sectional view of the scanning element and the angle limiting element along the line CC ′ in FIG. 12. Schematic explaining operation | movement of a scanning element and an angle limiting element.

  Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and ratios of the drawings are not necessarily the same as actual ones. Further, even when the same portion is represented between the drawings, the dimensional relationship and ratio may be represented differently. In particular, the following embodiments exemplify an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention depends on the shape, structure, arrangement, etc. of components. Is not specified. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

[First Embodiment]
[1] Configuration of Distance Measuring Device [1-1] Block Configuration of Distance Measuring Device FIG. 1 is a block diagram of a distance measuring device 10 according to the first embodiment of the present invention.

  The distance measuring device 10 is also called LIDAR (Light Detection and Ranging). The LIDAR scans a certain range, for example, in front of the vehicle using laser light, and detects the laser light reflected by the object existing in this scanning range. The LIDAR then uses the transmitted laser light and the received laser light to detect the object and measure the distance from the vehicle to the object.

  The distance measuring device 10 is provided on the front side of the vehicle (for example, the front bumper or the front grille), the rear side of the vehicle (for example, the rear bumper or the rear grille), and / or the side of the vehicle (for example, the side of the front bumper). Be placed. Further, the distance measuring device 10 may be disposed on the upper part of the vehicle, such as a roof or a hood.

  The distance measuring device 10 includes a light projecting unit 11, a light receiving unit 14, a pulse timing control unit 17, a distance calculation unit 18, and a main control unit 19.

  The light projecting unit 11 emits laser light and scans (also referred to as steering) the laser light. The light projecting unit 11 includes a light emitting element 12 and a scanning element 13.

  The light emitting element 12 emits laser light toward the scanning element 13. The light emitting element 12 is configured by a laser diode or the like. As the laser light, for example, infrared laser light (for example, wavelength λ = 905 nm) is used. The light emitting element 12 generates laser light as a pulse signal having a predetermined frequency.

  The scanning element 13 receives the laser light emitted from the light emitting element 12 and transmits the laser light. The scanning element 13 scans the laser light by controlling the emission angle of the laser light from the light emitting element 12.

  The light receiving unit 14 detects the laser light reflected by the object 2. At this time, the light receiving unit 14 performs a laser light detection operation by limiting the laser light incident on the light receiving unit 14 to laser light incident from a specific direction. The light receiving unit 14 includes an angle limiting element 15 and a light receiving element 16.

  The angle limiting element 15 receives the laser beam reflected by the object 2 and transmits the laser beam. At this time, the angle limiting element 15 refracts the laser light at a predetermined angle. In other words, the angle limiting element 15 refracts only the laser beam incident at a predetermined angle toward the light receiving element 16. Laser light incident at an angle other than a predetermined angle passes through the angle limiting element 15 but does not enter the light receiving element 16.

  The light receiving element 16 detects the laser light transmitted through the angle limiting element 15. The light receiving element 16 is composed of, for example, an infrared sensor. Infrared sensors include photodiodes and CMOS (complementary metal oxide semiconductor) photosensors. In addition, an infrared camera may be used as the light receiving element 16.

  The pulse timing control unit 17 controls the operation of the light emitting element 12. The light emitting element 12 emits laser light (that is, pulsed laser light) as a pulse signal. The pulse timing control unit 17 controls the timing of pulses included in the laser light. The pulse timing includes the period of the pulse signal, the frequency of the pulse signal, and the pulse width.

  The distance calculation unit 18 receives the timing information of the transmitted laser beam from the pulse timing control unit 17, receives the information of the emission angle of the laser beam from the main control unit 19, and receives the timing information and the light intensity of the received laser beam. Information is received from the light receiving element 16. The distance calculation unit 18 calculates the distance from the vehicle to the object using these pieces of information. Specifically, the distance calculation unit 18 calculates a linear distance, a horizontal distance, and a vertical distance using information such as an emission angle and a time from light emission to light reception. Further, the distance calculation unit 18 calculates the relative coordinates of the object using information such as the emission angle and the time from light emission to light reception. The distance and / or relative coordinates calculated by the distance calculation unit 18 can be output to the outside as data DOUT, for example.

  The main control unit 19 comprehensively controls the overall operation of the distance measuring device 10. The main control unit 19 controls the scanning operation of the scanning element 13 by applying a plurality of voltages to the scanning element 13. The main control unit 19 controls the angle limiting operation of the angle limiting element 15 by applying a plurality of voltages to the angle limiting element 15.

[1-2] Configuration of Projecting Unit 11 Next, the configuration of the projecting unit 11 will be described. FIG. 2 is a schematic diagram illustrating a configuration of the light projecting unit 11.

  The light emitting element 12 emits laser light toward the scanning element 13. Laser light from the light emitting element 12 travels in a direction perpendicular to the emission surface of the scanning element 13. The laser light emitted from the light emitting element 12 has high directivity, is a coherent and narrow laser light.

  It is assumed that the scanning element 13 scans the laser beam in a scanning range with an angle 2α. The angle α is larger than 0 degree and smaller than 90 degrees. The scanning element 13 projects laser light at an emission angle θ. The angle θ is equal to or smaller than the angle α. For example, if the angle of the laser beam traveling in the vertical direction with respect to the emission surface of the scanning element 13 is 0 degree, the right side with respect to the vertical direction is the angle “+ θ”, and the left side with respect to the vertical direction is the angle “−θ”. The laser beam can be emitted to the right side with respect to the emission angle “+ θ”, that is, the vertical direction, or the laser beam can be emitted to the left side with respect to the emission angle “−θ”, that is, the vertical direction. is there. The emission angle of the laser beam from the scanning element 13 is controlled by the main control unit 19.

  As the scanning element 13, various optical elements whose refractive index changes can be used. As the scanning element 13, a thermo-optical element, an electro-optical element, an electroabsorption optical element, a free carrier absorption optical element, a magneto-optical element, or the like can be used.

  In the present embodiment, the scanning element 13 is composed of, for example, a liquid crystal element. The scanning element 13 includes a plurality of regions divided in a matrix, and the phase of light can be controlled in each of the plurality of regions. A specific configuration of the scanning element 13 will be described later.

[1-3] Configuration of Light Receiving Unit 14 Next, the configuration of the light receiving unit 14 will be described. FIG. 3 is a schematic diagram illustrating the configuration of the light receiving unit 14.

  The angle limiting element 15 receives the laser beam reflected by the object and transmits the laser beam. In addition, the angle limiting element 15 causes the laser light incident at the same incident angle as the laser light emission angle by the scanning element 13 to be perpendicular to the incident surface of the angle limiting element 15 (with a refraction angle of 0 degree). Refract). The incident angle of the laser beam by the angle limiting element 15 is controlled by the main control unit 19.

  In the case of the emission angle θ by the scanning element 13, the angle limiting element 15 refracts the laser beam incident at the incident angle θ in the vertical direction, that is, with a refraction angle of 0 degree. When the emission angle by the scanning element 13 is 0 degree, the angle limiting element 15 transmits the laser light incident in the vertical direction without refracting it.

  The angle limiting element 15 is composed of a liquid crystal element. The angle limiting element 15 includes a plurality of regions divided into a matrix, and can control the phase of light in each of the plurality of regions. A specific configuration of the angle limiting element 15 will be described later.

  The laser light that has passed through the angle limiting element 15 passes through the condenser lens 20. The condensing lens 20 is constituted by a plano-convex lens, for example. The plano-convex lens 20 is disposed so that its plane faces the angle limiting element 15. The plano-convex lens 20 condenses laser light at a predetermined refraction angle. When the plano-convex lens 20 is not provided, the size of the light receiving element 16 may be approximately the same as that of the angle limiting element 15, but the provision of the plano-convex lens 20 is preferable because the size of the light receiving element 16 can be reduced. The laser light transmitted through the plano-convex lens 20 enters the light receiving element 16.

[1-4] Configuration of Scanning Element 13 and Angle Limiting Element 15 Next, the configuration of the scanning element 13 and the angle limiting element 15 will be described. FIG. 4 is a plan view of the scanning element 13 and the angle limiting element 15. FIG. 5 is a cross-sectional view of the scanning element 13 taken along the line AA ′ of FIG. FIG. 6 is a cross-sectional view of the angle limiting element 15 along the line BB ′ of FIG.

(Scanning element 13)
The scanning element 13 is a transmissive liquid crystal element. The scanning element 13 includes substrates 30 and 31 arranged to face each other and a liquid crystal layer 32 sandwiched between the substrates 30 and 31. Each of the substrates 30 and 31 is composed of a transparent substrate (for example, a glass substrate or a plastic substrate). The substrate 30 is disposed to face the light emitting element 12, and laser light from the light emitting element 12 enters the liquid crystal layer 32 from the substrate 30 side.

  The liquid crystal layer 32 is filled between the substrates 30 and 31. Specifically, the liquid crystal layer 32 is sealed in a region surrounded by the substrates 30 and 31 and the sealing material 33. The ellipse illustrated in the liquid crystal layer 32 in FIG. 5 schematically represents liquid crystal molecules. The sealing material 33 is made of, for example, an ultraviolet curable resin, a thermosetting resin, or an ultraviolet / heat combination type curable resin, and is applied to the substrate 30 or the substrate 31 in the manufacturing process and then cured by ultraviolet irradiation or heating. It is done.

  The liquid crystal material constituting the liquid crystal layer 32 changes the optical characteristics by manipulating the orientation of the liquid crystal molecules in accordance with the voltage (electric field) applied between the substrates 30 and 31. The scanning element 13 of this embodiment is a homogeneous mode. That is, a positive (P-type) nematic liquid crystal having positive dielectric anisotropy is used as the liquid crystal layer 32, and the liquid crystal molecules are aligned in a substantially horizontal direction with respect to the substrate surface when no voltage (electric field) is applied. To do. In the homogeneous mode, the major axis (director) of the liquid crystal molecules is aligned in a substantially horizontal direction when no voltage is applied, and the major axis of the liquid crystal molecules is inclined in the vertical direction when a voltage is applied. The tilt angle of the liquid crystal molecules changes according to the applied effective voltage. The initial alignment of the liquid crystal layer 32 is controlled by two alignment films (not shown) provided on the substrates 30 and 31 with the liquid crystal layer 32 interposed therebetween.

  As the liquid crystal mode, a vertical alignment (VA) mode using a negative (N-type) nematic liquid crystal may be used. In the VA mode, the major axis of the liquid crystal molecules is aligned in a substantially vertical direction when no electric field is applied, and the major axis of the liquid crystal molecules is inclined in the horizontal direction when a voltage is applied.

  A plurality of cell electrodes 34 each extending in the X direction are provided on the liquid crystal layer 32 side of the substrate 30. An arbitrary number of cell electrode groups constitute the unit electrode 35. FIG. 4 illustrates three unit electrodes 35-1 to 35-3, but the number of unit electrodes 35 can be arbitrarily set. In FIG. 4, one unit electrode 35 includes four cell electrodes 34, but the number of cell electrodes 34 included in one unit electrode 35 can be arbitrarily set. The unit electrode 35-1 is composed of cell electrodes 34-1 to 34-4. The unit electrode 35-2 is composed of cell electrodes 34-5 to 34-8. The unit electrode 35-3 includes cell electrodes 34-9 to 34-12.

  The length of the unit electrode 35 in the Y direction can be changed by changing the number of cell electrodes 34 constituting the unit electrode 35. The cell electrode 34 is composed of a transparent electrode, and for example, ITO (indium tin oxide) is used.

  The plurality of unit electrodes 35 are electrically separated from each other, and the plurality of cell electrodes 34 are electrically separated from each other. That is, voltage control can be individually performed on the cell electrode 34, and voltage control can be performed individually on the unit electrode 35.

  A plurality of cell electrodes 36 each extending in the Y direction orthogonal to the X direction are provided on the liquid crystal layer 32 side of the substrate 31. An arbitrary number of cell electrode groups constitute the unit electrode 37. FIG. 4 illustrates three unit electrodes 37-1 to 37-3, but the number of unit electrodes 37 can be arbitrarily set. In FIG. 4, one unit electrode 37 includes four cell electrodes 36, but the number of cell electrodes 36 included in one unit electrode 37 can be arbitrarily set. The unit electrode 37-1 includes cell electrodes 36-1 to 36-4. The unit electrode 37-2 is composed of cell electrodes 36-5 to 36-8. The unit electrode 37-3 includes cell electrodes 36-9 to 36-12.

  The length of the unit electrode 37 in the X direction can be changed by changing the number of cell electrodes 36 constituting the unit electrode 37. The cell electrode 36 is composed of a transparent electrode, and for example, ITO is used.

  The plurality of unit electrodes 37 are electrically separated from each other, and the plurality of cell electrodes 36 are electrically separated from each other. That is, voltage control can be individually performed on the cell electrode 36, and voltage control can be performed individually on the unit electrode 37.

  As understood from FIG. 4, the scanning element 13 is a passive matrix system (simple matrix system) and a dot matrix system. That is, the scanning element 13 has a dot matrix pattern. The scanning element 13 can control the liquid crystal alignment for each dot at which one cell electrode 34 and one cell electrode 36 intersect.

  One intersection region between the unit electrode 35 and the unit electrode 37 is a substantially square shape in the example of FIG. 4, and this intersection region is a unit for controlling the phase of light. Voltage control of the unit electrode 35 and the unit electrode 37 is performed by the main control unit.

(Angle limiting element 15)
Next, the configuration of the angle limiting element 15 will be described. The angle limiting element 15 has the same configuration as the scanning element 13 described above.

  As shown in FIGS. 4 and 6, the angle limiting element 15 includes a substrate 40, a substrate 41, a liquid crystal layer 42, and a sealing material 43. The substrate 40 is provided with a plurality of unit electrodes 45 (45-1 to 45-3). The substrate 41 is provided with a plurality of unit electrodes 47 (47-1 to 47-3).

  The unit electrode 45 is composed of a plurality of cell electrodes 44. As an example, the unit electrode 45-1 is composed of cell electrodes 44-1 to 44-4. The unit electrode 45-2 is composed of cell electrodes 44-5 to 44-8. The unit electrode 45-3 includes cell electrodes 44-9 to 44-12.

  The unit electrode 47 is composed of a plurality of cell electrodes 46. As an example, the unit electrode 47-1 includes cell electrodes 46-1 to 46-4. The unit electrode 47-2 is composed of cell electrodes 46-5 to 46-8. The unit electrode 47-3 includes cell electrodes 46-9 to 46-12.

  Note that a transmissive liquid crystal element (transmissive LCOS) using an LCOS (Liquid Crystal on Silicon) method may be used as the scanning element 13 (and the angle limiting element 15). By using the transmissive LCOS, the electrode can be finely processed, and a smaller scanning element 13 can be realized. In the transmissive LCOS, a silicon substrate (or a silicon layer formed on a transparent substrate) is used. Since the silicon substrate transmits light (including infrared rays) having a wavelength greater than a specific wavelength in relation to the band gap, LCOS can be used as a transmissive liquid crystal element. By using LCOS, a liquid crystal element having a smaller cell electrode can be obtained, and thus further downsizing can be achieved. In addition, since the mobility of the liquid crystal molecules is high, the laser beam can be scanned at a high speed.

[1-5] Circuit Configuration Next, a circuit configuration around the scanning element 13 and the angle limiting element 15 will be described with reference to FIG. 4 described above.

  The scanning element 13 is voltage-controlled by the main control unit 19. For this purpose, the scanning element 13 is electrically connected to the main control unit 19 via a plurality of signal lines.

  Specifically, the cell electrodes 34-1, 34-5, and 34-9 are electrically connected to the signal line SL1. Cell electrodes 34-2, 34-6, and 34-10 are electrically connected to signal line SL2. Cell electrodes 34-3, 34-7, and 34-11 are electrically connected to signal line SL3. Cell electrodes 34-4, 34-8, and 34-12 are electrically connected to signal line SL4.

  The cell electrodes 36-1, 36-5, 36-9 are electrically connected to the signal line SL5. Cell electrodes 36-2, 36-6, 36-10 are electrically connected to signal line SL6. The cell electrodes 36-3, 36-7, 36-11 are electrically connected to the signal line SL7. Cell electrodes 36-4, 36-8, and 36-12 are electrically connected to signal line SL8.

  With this connection relationship, the unit electrodes 35-1 to 35-3 are subjected to the same voltage control by the main control unit 19. Accordingly, each of the unit electrodes 35-1 to 35-3 can form the same refractive index gradient in the liquid crystal layer. The unit electrodes 37-1 to 37-3 are respectively subjected to the same voltage control by the main control unit 19. Therefore, each of the unit electrodes 37-1 to 37-3 can form the same refractive index gradient in the liquid crystal layer.

  The angle limiting element 15 is voltage-controlled by the main control unit 19. For this purpose, the angle limiting element 15 is electrically connected to the main control unit 19 via a plurality of signal lines.

  Specifically, the cell electrodes 34-1, 34-5, and 34-9 are electrically connected to the signal line SL1. Cell electrodes 34-2, 34-6, and 34-10 are electrically connected to signal line SL2. Cell electrodes 34-3, 34-7, and 34-11 are electrically connected to signal line SL3. Cell electrodes 34-4, 34-8, and 34-12 are electrically connected to signal line SL4.

  The cell electrodes 36-1, 36-5, 36-9 are electrically connected to the signal line SL5. Cell electrodes 36-2, 36-6, 36-10 are electrically connected to signal line SL6. The cell electrodes 36-3, 36-7, 36-11 are electrically connected to the signal line SL7. Cell electrodes 36-4, 36-8, and 36-12 are electrically connected to signal line SL8.

  With this connection relationship, the unit electrodes 35-1 to 35-3 are subjected to the same voltage control by the main control unit 19. Accordingly, each of the unit electrodes 35-1 to 35-3 can form the same refractive index gradient in the liquid crystal layer. The unit electrodes 37-1 to 37-3 are respectively subjected to the same voltage control by the main control unit 19. Therefore, each of the unit electrodes 37-1 to 37-3 can form the same refractive index gradient in the liquid crystal layer.

  Here, the scanning element 13 and the angle limiting element 15 are electrically connected to the main control unit 19 using common signal lines SL1 to SL8. Therefore, the main control unit 19 can reliably control the voltage of the scanning element 13 and the angle limiting element 15 and can set the refractive indexes of the scanning element 13 and the angle limiting element 15 to be the same. That is, the exit angle of the scanning element 13 and the incident angle of the angle limiting element 15 can be made the same. In other words, the laser beam incident on the angle limiting element 15 at the same incident angle as the emission angle of the scanning element 13 can be incident on the light receiving element 16.

  If the voltage control of the scanning element 13 and the angle limiting element 15 is the same, the scanning element 13 and the angle limiting element 15 are connected to the main control unit without connecting the scanning element 13 and the angle limiting element 15 with a common signal line. 19 may be electrically connected to each other by different signal lines.

[2] Operation of Distance Measuring Device 10 [2-1] Basic Operation of Distance Measuring Device 10 First, the basic operation of the distance measuring device 10 will be described. FIG. 7 is a schematic diagram illustrating the basic operation of the distance measuring device 10. In addition, in FIG. 7, the aspect which the distance measuring device 10 scans the front of the vehicle 1 is shown as an example.

  The light projecting unit 11 included in the distance measuring device 10 projects laser light within a scanning range of an angle 2α. The light receiving unit 14 receives the laser light reflected by the object 2. The distance L to the assumed object 2 and the scanning range R at the distance L are assumed. For example, when the angle 2α = 10 degrees and the distance L = 10 m, the scanning range R = 1.7 m, and when the angle 2α = 10 degrees and the distance L = 50 m, the scanning range R = 8.7 m. is there. The angle 2α, the distance L, and the scanning range R can be arbitrarily designed according to specifications required for the distance measuring device 10.

  FIG. 8 is a diagram for explaining the waveform of the laser beam by the distance measuring device 10. The upper side of FIG. 8 is a light emission waveform, and the lower side is a light reception waveform. The horizontal axis in FIG. 8 is time, and the vertical axis in FIG. 8 is intensity (light intensity).

  The light emitting element 12 emits laser light composed of a pulse signal. That is, the light emitting element 12 emits laser light in a time division manner. The distance measuring device 10 projects laser light as a pulse signal. It is assumed that the pulse signal has a period P and a pulse width W. A delay amount Δ, which is a time from when one pulse is transmitted to when a pulse reflected by an object is received, and a light velocity C are set. The delay amount Δ is calculated by “Δ = 2L / C”.

  For example, it is assumed that the pulse width W = 10 nsec and the period P = 10 μsec (that is, the frequency f = 100 kHz). When the delay amount Δ = 67 nsec, the distance L = 10 m is calculated.

  By such an operation, the object can be detected and the distance to the object can be calculated.

[2-2] Scanning operation of the distance measuring device 10 In order to improve the signal intensity, it is necessary to cut out disturbance light such as sunlight that becomes disturbance. While ambient light is incident from all angles, the signal returns only from the angle emanating from the distance measuring device 10. Therefore, the signal intensity is improved by receiving the laser beam by limiting the angle at which the signal returns.

  FIG. 9 is a flowchart for explaining the operation of the distance measuring apparatus 10. The main control unit 19 sets the emission angle of the scanning element 13 to the angle θ, and sets the incident angle of the angle limiting element 15 to the angle θ (step S100). That is, the main control unit 19 operates the scanning element 13 and the angle limiting element 15 in synchronization. Synchronous means that the refraction angle by the scanning element 13 and the refraction angle by the angle limiting element 15 are the same.

  For example, as illustrated in FIG. 5, the main control unit 19 applies an effective voltage that decreases in this order to the cell electrodes 36-1 to 36-4 in the unit electrode 37-1. The voltage applied between the cell electrode 34 and the cell electrode 36 is an alternating voltage. Also in the unit electrodes 37-2 and 37-3, the main control unit 19 applies the same voltage as that of the unit electrode 37-1. As a result, the same refractive index gradient is generated in each of the unit electrodes 37-1 to 37-3.

  Similarly, as shown in FIG. 6, the main control unit 19 applies an effective voltage that decreases in this order to the cell electrodes 46-1 to 46-4 in the unit electrode 47-1. The voltage applied between the cell electrode 44 and the cell electrode 46 is an alternating voltage. Also in the unit electrodes 47-2 and 47-3, the main control unit 19 applies the same voltage as that of the unit electrode 47-1. As a result, the same refractive index gradient occurs in each of the unit electrodes 47-1 to 47-3.

  Subsequently, the main control unit 19 projects laser light from the light projecting unit 11 at the emission angle θ (step S101). Specifically, the pulse timing control unit 17 causes the light emitting element 12 to emit pulsed laser light. The laser light from the light emitting element 12 passes through the scanning element 13 and is refracted by an angle θ. In the example of FIG. 5, the laser light incident from the substrate 30 side is emitted from the scanning element 13 so as to be refracted to the right side.

  Subsequently, the light receiving unit 14 receives the laser beam incident at the incident angle θ (step S102). Specifically, the angle limiting element 15 refracts laser light incident at an incident angle θ in a direction perpendicular to the incident surface (with a refraction angle of 0 degree). The laser light transmitted through the angle limiting element 15 enters the light receiving element 16. Thus, the angle limiting element 15 can limit the laser light incident on the light receiving element 16 to the laser light incident on the light receiving unit 14 at the incident angle θ. The laser light incident on the angle limiting element 15 at an angle other than the incident angle θ is not refracted toward the light receiving element 16 and is not incident on the light receiving element 16, so that the laser light is not detected by the light receiving element 16. .

  Subsequently, the distance calculation unit 18 calculates the distance to the object (step S103). Specifically, the distance calculation unit 18 receives the timing information of the transmitted laser beam from the pulse timing control unit 17, receives the information of the emission angle of the laser beam from the main control unit 19, and receives the timing of the received laser beam. Information and light intensity information are received from the light receiving element 16. The distance calculation unit 18 calculates the distance from the vehicle to the object using these pieces of information.

[3] Embodiment Next, an embodiment of the light projecting unit 11 will be described. FIG. 10 is a schematic diagram illustrating a configuration of the light projecting unit 11 according to the embodiment.

  A plano-concave lens 21 is provided on the exit surface side of the scanning element 13. The plano-concave lens 21 is arranged so that its plane faces the scanning element 13. The plano-concave lens 21 diffuses laser light. That is, the plano-concave lens 21 emits laser light at an emission angle (refraction angle) θ ′ larger than the incident angle θ. According to the embodiment, the scanning range of the laser beam can be widened.

  Next, an embodiment of the light receiving unit 14 will be described. FIG. 11 is a schematic diagram illustrating a configuration of the light receiving unit 14 according to the embodiment.

  A plano-concave lens 22 is provided on the incident surface side of the angle limiting element 15. The plano-concave lens 22 is arranged so that its plane faces the angle limiting element 15. The plano-concave lens 22 refracts laser light incident on the concave surface side at an incident angle θ ′ at a refraction angle θ. According to the embodiment, the light receiving range of the laser beam can be widened, and the emission angle θ ′ of the light projecting unit 11 and the incident angle θ ′ of the light receiving unit 14 can be made the same.

[4] Effects of First Embodiment As described in detail above, in the first embodiment, the distance measuring device 10 uses the light emitting element 12 that emits laser light and the laser light emitted by the light emitting element 12 at a first angle. A scanning element 13 that emits light at an emission angle of θ, a light receiving element 16 that detects laser light reflected by an object, and a laser that enters laser light incident on the light receiving element 16 at an incident angle of a first angle θ. And an angle limiting element 15 for limiting to light.

  Therefore, according to the first embodiment, the distance measuring device 10 converts the laser light transmitted from the light (including disturbance light such as sunlight) incident on the distance measuring device 10 into the laser light reflected by the object. Can be received with restrictions. Thereby, SN ratio can be improved. In addition, since the SN ratio is improved, even a minute laser beam reflected by a distant object can be detected with high accuracy, and a signal at a long distance can be detected. The measurable distance can be improved.

  Further, the scanning element 13 and the angle limiting element 15 are configured by liquid crystal elements having the same structure. Further, the scanning element 13 and the angle limiting element 15 are controlled by the same signal. Thereby, it is easy to synchronize the scanning element 13 and the angle limiting element 15, and the reception accuracy can be improved.

[Second Embodiment]
In the second embodiment, the scanning element 13 and the angle limiting element 15 are configured by a common liquid crystal element.

  FIG. 12 is a plan view of the scanning element 13 and the angle limiting element 15 according to the second embodiment of the present invention. 13 is a cross-sectional view of the scanning element 13 and the angle limiting element 15 taken along the line CC ′ of FIG.

  The substrates 30 and 31 and the liquid crystal layer 32 are shared by the scanning element 13 and the angle limiting element 15. The cell electrodes 34-1 to 34-12 are shared by the scanning element 13 and the angle limiting element 15. Further, the signal lines SL <b> 1 to SL <b> 8 are commonly connected to the scanning element 13 and the angle limiting element 15.

  FIG. 14 is a schematic diagram for explaining the operation of the scanning element 13 and the angle limiting element 15. The main control unit 19 sets the emission angle of the scanning element 13 to the angle θ, and sets the incident angle of the angle limiting element 15 to the angle θ. The light projecting unit 11 projects laser light at an emission angle θ. The light receiving unit 14 receives laser light incident at an incident angle θ.

  According to the second embodiment, the scanning element 13 and the angle limiting element 15 are integrally formed as a liquid crystal element. Thereby, the scanning element 13 and the angle limiting element 15 can cause errors in the manufacturing process such as the thickness of the liquid crystal layer (cell gap), the width of the cell electrodes, the space between the cell electrodes, and the material and thickness of the substrate. Can be the same. Therefore, the optical characteristics of the scanning element 13 and the angle limiting element 15 can be made the same. As a result, the receiving accuracy can be further improved.

  In each of the above embodiments, an infrared laser is used as the laser light handled by the distance measuring device. However, the present invention is not limited to this, and the distance measuring device according to the embodiment can be applied to light other than infrared rays.

  In the above embodiment, a distance measuring device mounted on a vehicle has been described. However, the present invention is not limited to this, and the distance measuring device can be applied to various electronic devices having a function of scanning laser light.

  In the above embodiment, the passive matrix method is applied to the angle limiting element 15, but other electrode structures may be used. For example, a plurality of first electrodes corresponding to a plurality of dots and electrically separated from each other are formed on the first substrate, and one planar common electrode is formed on the second substrate facing the first substrate. Then, a plurality of first electrodes may be driven using a plurality of switching elements constituted by TFTs (Thin Film Transistors) or the like. The same applies to the scanning element 13.

  The present invention is not limited to the above embodiment, and can be embodied by modifying the constituent elements without departing from the scope of the invention. Further, the above embodiments include inventions at various stages, and are obtained by appropriately combining a plurality of constituent elements disclosed in one embodiment or by appropriately combining constituent elements disclosed in different embodiments. Various inventions can be configured. For example, even if some constituent elements are deleted from all the constituent elements disclosed in the embodiments, the problems to be solved by the invention can be solved and the effects of the invention can be obtained. Embodiments made can be extracted as inventions.

  DESCRIPTION OF SYMBOLS 10 ... Distance measuring device, 11 ... Light projection part, 12 ... Light emitting element, 13 ... Scanning element, 14 ... Light receiving part, 15 ... Angle limiting element, 16 ... Light receiving element, 17 ... Pulse timing control part, 18 ... Distance calculating part , 19 ... main control unit, 20 ... plano-convex lens, 21, 22 ... plano-concave lens, 30, 31 ... substrate, 32 ... liquid crystal layer, 33 ... sealing material, 34, 36 ... cell electrode, 35, 37 ... unit electrode, 40 , 41 ... Substrate, 42 ... Liquid crystal layer, 43 ... Sealing material, 44, 46 ... Cell electrode, 45, 47 ... Unit electrode, SL1-SL8 ... Signal line

Claims (6)

A light emitting element that emits laser light;
A scanning element that projects laser light emitted by the light emitting element at an emission angle of a first angle;
A light receiving element for detecting the laser beam reflected by the object;
A distance measuring device comprising: an angle limiting element that limits laser light incident on the light receiving element to laser light incident at the incident angle of the first angle. The distance measuring device according to claim 1, wherein the angle limiting element and the scanning element are operated in synchronization. The distance measuring device according to claim 1, wherein the angle limiting element is configured by a liquid crystal element. The distance measuring device according to claim 1, wherein the scanning element is configured by a liquid crystal element. Each of the scanning element and the angle limiting element includes first and second liquid crystal elements,
The distance measuring device according to claim 1, wherein the first and second liquid crystal elements are integrally formed. Projecting laser light at an emission angle of the first angle;
And a step of limiting laser light incident on the light receiving element to laser light incident at the incident angle of the first angle.