JP7024212B2 - Distance measuring device - Google Patents

Description

The present invention relates to a distance measuring device that measures the position of an object by scanning a laser beam.

A distance measuring device called LIDAR (Light Detection and Ranging) is known. LIDAR is a sensor that optically measures the distance to a surrounding object. LIDAR irradiates an object with a pulsed laser beam and measures the distance from the round-trip time until the laser beam reflected by the object returns. Recently, LIDAR has been used for advanced driver assistance systems (ADAS) and autonomous driving.

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

Since the polygon mirror (Patent Document 1) and the MEMS mirror (Patent Document 2) used in the coaxial optical system system have moving parts, there is a concern about long-term reliability due to the vibration of the vehicle. Further, since the polygon mirror and the MEMS mirror are optical components, the cost is high.

In the separation optical system method, a method of changing the emission angle of light by electrically changing the phase has been proposed (Patent Documents 3 and 4). This configuration has no moving parts and may be cheaper to manufacture, but there are concerns about measurement distance. One of the factors that shortens the measurement distance is that the intensity of ambient light such as sunlight becomes stronger than the laser light that is a signal among the light incident on the photodiode, that is, the signal-to-noise ratio (SN ratio). ) Decreased. When the signal-to-noise ratio decreases, it is not possible to receive and detect signals with high accuracy.

Japanese Unexamined Patent Publication No. 2010-38859 Japanese Unexamined Patent Publication No. 2009-216789 International Publication No. 2014/110017 International Release 2016/022220

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

The distance measuring device according to one aspect of the present invention includes a light emitting element that emits laser light, a first deflection element that has a plurality of first phase shifters and refracts the laser light emitted by the light emitting element, and a plurality of first phase shifters. The second phase shifter is provided with a second deflection element that refracts the laser light reflected by the object, and a light receiving element that detects the laser light transmitted through the second deflection element. The first pitch of the first phase shifter is different from the second pitch of the second phase shifter.

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

The schematic diagram explaining the structure of the light projection part which concerns on this invention. The schematic diagram explaining the structure of the light receiving part which concerns on a comparative example. The schematic diagram explaining the structure of the light receiving part which concerns on this invention. The block diagram of the distance measuring apparatus which concerns on embodiment of this invention. Schematic sectional view showing the structure of the light projection part which concerns on embodiment. Top view of the scanning element. FIG. 6 is a cross-sectional view of the scanning element along the AA'line of FIG. FIG. 5 is a cross-sectional view illustrating another configuration example of the scanning element. Schematic sectional view showing the structure of the light receiving part which concerns on embodiment. Top view of the angle limiting element. FIG. 10 is a cross-sectional view of the angle limiting element along the BB'line of FIG. The schematic diagram explaining the basic operation of a distance measuring device. The figure explaining the waveform of the laser beam by the distance measuring device. A flowchart illustrating the operation of a distance measuring device. The schematic diagram explaining the operation of a scanning element. The schematic diagram which shows the structure of the light projection part which concerns on Example. The schematic diagram which shows the structure of the light receiving part which concerns on Example.

Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and ratios of each drawing are not always the same as the actual ones. Further, even when the same part is represented between the drawings, the relationship and ratio of the dimensions of each other may be represented differently. In particular, some embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and depending on the shape, structure, arrangement, etc. of the components, the technical idea of the present invention. Is not specified. In the following description, elements having the same function and configuration are designated by the same reference numerals, and duplicate explanations will be given only when necessary.

[1] Outline of the present invention First, an outline of the present invention will be described.

The present invention relates to a distance measuring device. The distance measuring device is also called LIDAR (Light Detection and Ranging). LIDAR uses a laser beam to scan, for example, a range in front of the vehicle and detects the laser beam reflected by an object present in this scanning range. Then, LIDAR uses the projected laser beam and the received laser beam to detect the object and measure the distance from the vehicle to the object.

FIG. 1 is a schematic view illustrating the configuration of the light projecting unit 11 according to the present invention. The light projecting unit 11 has a function of projecting laser light. The light projecting unit 11 includes a light emitting element (LD) 12 and a deflection element 13.

The deflection element 13 is composed of an optical phased array. The optical phased array includes a plurality of phase shifters PS1 that change the phase of light. The plurality of stepped quadrangles shown in the deflection element 13 of FIG. 1 schematically show a plurality of phase shifters PS1. The plurality of phase shifters PS1 are arranged for each arrangement pitch d1. The length of the quadrangle representing the phase shifter PS1 represents the magnitude of the refractive index, and the longer the length of the quadrangle in the vertical direction, the larger the refractive index.

The deflection element 13 can change the refractive index for each arrangement pitch d1. In the example of FIG. 1, the deflection element 13 has a refractive index distribution (refractive index gradient) in which the refractive index decreases in order toward the right side. The laser light emitted from the light emitting element LD is refracted by the deflection element 13 and emitted from the deflection element 13 at a desired emission angle.

Since the deflection element 13 includes regularly arranged phase shifters PS1, the light passing through the deflection element 13 is diffracted. That is, the deflection element 13 emits diffracted light such as 0th-order light, + 1st-order light, and -1st-order light. The 0th-order light is a desired laser beam emitted by the light projecting unit 11. The +1st order light, the -1st order light, and the like are diffracted light unnecessary for the scanning operation.

FIG. 2 is a schematic view illustrating the configuration of the light receiving unit 14 according to the comparative example. The light receiving unit 14 has a function of receiving the laser light (reflected light) reflected by the object from the laser light projected by the light projecting unit 11. The light receiving unit 14 includes a deflection element 15'and a light receiving element (PD) 16.

The deflection element 15'of the light receiving unit 14 has the same configuration as the deflection element 13 of the light projecting unit 11. The gradient of the refractive index in the deflection element 15'is set to be the same as the gradient of the refractive index in the deflection element 13. As a result, the emission angle of the light projecting unit 11 and the incident angle of the light receiving unit 14 can be made the same, so that the signal intensity incident on the light receiving element 16 can be increased.

In the comparative example, the arrangement pitch d1 in the deflection element 13 of the light projecting unit 11 and the arrangement pitch d1 in the deflection element 15 of the light receiving unit 14 are the same. When the arrangement pitch is the same for the light receiving unit 14 and the light projecting unit 11, in addition to the 0th-order light, the diffracted light such as the +1st-order light and the -1st-order light is also reflected by an unintended object other than the object. It is incident on the light receiving element PD. As a result, the ratio of the intensity of the required signal to the light incident on the light receiving element PD decreases, and the SN ratio decreases.

Therefore, in the present invention, the arrangement pitch in the deflection element of the light receiving unit is set to be different from the arrangement pitch in the deflection element of the light projecting unit.

FIG. 3 is a schematic view illustrating the configuration of the light receiving unit 14 according to the present invention. The deflection element 15 is composed of an optical phased array. The optical phased array includes a plurality of phase shifters PS2. The deflection element 15 has an array pitch d2. The arrangement pitch d2 on the light receiving side is different from the arrangement pitch d1 on the light emitting side. That is, it has a relationship of "d1 ≠ d2". Further, the gradient of the refractive index of the deflection element 15 of the light receiving unit 14 is set to be the same as the gradient of the refractive index of the deflection element 13 of the light projecting unit 11.

As a result, in addition to the 0th-order light, the reflected light such as the +1st-order light and the -1st-order light reflected by an unintended object other than the object is not incident on the light receiving element 16. Therefore, unnecessary light that becomes noise can be reduced, and the SN ratio can be improved.

In the present invention, an optical phased array is used for each of the light projecting unit and the light receiving unit, the gradients of the refractive indexes of each are the same, and the arrangement pitch of the phase shifters has different periodicities. Then, while effectively taking in the main signal component to be projected, it suppresses the reception of diffracted light that becomes noise.

[2] Configuration of Distance Measuring Device [2-1] Block Configuration of Distance Measuring Device FIG. 4 is a block diagram of a distance measuring device 10 according to an embodiment of the present invention.

The distance measuring device 10 is located 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 arranged on the upper part of the vehicle such as a roof or a bonnet.

The distance measuring device 10 includes a light emitting 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 a laser beam and scans (also referred to as steering) the laser beam. The light projecting unit 11 includes a light emitting element 12 and a scanning element (deflection element) 13.

The light emitting element 12 emits laser light toward the scanning element 13. The light emitting element 12 is composed of a laser diode or the like. As the laser light, for example, infrared laser light (for example, wavelength λ = 905 nm) is used. Further, 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. Further, the scanning element 13 scans the laser beam by controlling the emission angle of the laser beam from the light emitting element 12.

The light receiving unit 14 detects the laser beam reflected by the object 2. At this time, the light receiving unit 14 limits the laser light incident from a specific direction and performs a laser light detection operation. The light receiving unit 14 includes an angle limiting element (deflection 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 beam 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.

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 the pulse included in the laser beam. The timing of the pulse 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 light from the pulse timing control unit 17, the information on the emission angle of the laser light from the main control unit 19, and the timing information and the light intensity of the received laser light. Information is received from the light receiving element 16. The distance calculation unit 18 uses this information to calculate the distance from the vehicle to the object. Specifically, the distance calculation unit 18 calculates a linear distance, a horizontal distance, and a vertical distance by 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 by 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, for example, data DOUT.

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.

[2-2] Configuration of the Floodlighting Unit 11 Next, the configuration of the floodlighting unit 11 will be described. FIG. 5 is a schematic cross-sectional view showing the configuration of the light projecting unit 11. The light projecting unit 11 includes a light emitting element (LD) 12, a collimator 20, and a scanning element 13.

The light emitting element 12 emits a laser beam toward the collimator 20. The collimator 20 is composed of a lens and produces parallel rays. The laser beam emitted from the collimator 20 has high directivity, is coherent, and has a narrow width. When the light emitting element 12 emits a laser beam having high directivity, the collimator 20 is unnecessary. The laser beam from the collimator 20 travels in the direction perpendicular to the emission surface of the scanning element 13.

It is assumed that the scanning element 13 scans the laser beam within a scanning range of an angle of 2α. The angle α is greater than 0 degrees and less than 90 degrees. The scanning element 13 projects laser light at an emission angle θ. The angle θ is equal to or less than the angle α. For example, assuming that the angle of the laser beam traveling in the direction perpendicular to the emission surface of the scanning element 13 is 0 degrees, the right side is the angle “+ θ” in the vertical direction, and the left side is the angle “−θ” in the vertical direction. It is possible to emit the laser beam to the right side with respect to the emission angle "+ θ", that is, the vertical direction, and it is also possible to emit the laser beam to the left side with respect to the emission angle "-θ", that is, the vertical direction. be. The emission angle of the laser beam from the scanning element 13 is controlled by the main control unit 19.

The scanning element 13 is composed of an optical phased array. The optical phased array includes a plurality of phase shifters that change the phase of light. The scanning element 13 is composed of, for example, a liquid crystal element. The scanning element 13 includes a plurality of regions divided along one direction, and it is possible to control the phase of light in each of the plurality of regions.

(Structure of scanning element 13)
Next, the configuration of the scanning element 13 will be described. FIG. 6 is a plan view of the scanning element 13. FIG. 7 is a cross-sectional view of the scanning element 13 along the AA'line of FIG.

The scanning element 13 is a transmissive liquid crystal element. The scanning element 13 includes substrates 30 and 31 arranged opposite to 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 arranged to face the light emitting element 12, and the laser light from the light emitting element 12 is incident on 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 enclosed in a region surrounded by the substrates 30 and 31 and the sealing material 33. The ellipse illustrated in the liquid crystal layer 32 of FIG. 7 schematically represents a liquid crystal molecule. The sealing material 33 is made of, for example, an ultraviolet curable resin, a thermosetting resin, an ultraviolet / heat combined type curable resin, or the like, and is applied to the substrate 30 or the substrate 31 in the manufacturing process and then cured by ultraviolet irradiation, heating, or the like. Be done.

The liquid crystal material constituting the liquid crystal layer 32 changes its optical characteristics by manipulating the orientation of the liquid crystal molecules according to the voltage (electric field) applied between the substrates 30 and 31. The scanning element 13 of the present embodiment has a homogeneous mode. That is, a positive (P-type) nematic liquid crystal having a positive dielectric anisotropy is used as the liquid crystal layer 32, and the liquid crystal molecules are oriented substantially horizontally with respect to the substrate surface when no voltage (electric field) is applied. do. In the homogenous mode, the long axis (director) of the liquid crystal molecule is substantially oriented in the horizontal direction when no voltage is applied, and the long axis of the liquid crystal molecule is tilted in the vertical direction when the voltage is applied. The tilt angle of the liquid crystal molecule changes depending on the effective voltage applied. The initial orientation of the liquid crystal layer 32 is controlled by two alignment films (not shown) provided on the substrates 30 and 31 so as to sandwich the liquid crystal layer 32.

As the liquid crystal mode, a vertical alignment (VA: Vertical Alignment) mode using a negative type (N type) nematic liquid crystal may be used. In the VA mode, the major axis of the liquid crystal molecule is oriented substantially vertically when no electric field is applied, and the major axis of the liquid crystal molecule is tilted in the horizontal direction when a voltage is applied.

On the liquid crystal layer 32 side of the substrate 30, a plurality of electrodes 34, each of which extends in the Y direction and is arranged in the X direction orthogonal to the Y direction, are provided. FIG. 7 illustrates five electrodes 34-1 to 34-5, but the number of electrodes 34 can be set arbitrarily. The plurality of electrodes 34 are electrically separated from each other, and voltage control can be performed individually for the plurality of electrodes 34. The voltage control of the electrode 34 is performed by the main control unit.

On the liquid crystal layer 32 side of the substrate 31, a plurality of electrodes 35, each extending in the Y direction and lining up in the X direction, are provided. FIG. 7 illustrates five electrodes 35-1 to 35-5. The plurality of electrodes 35 are provided corresponding to the plurality of electrodes 34. That is, the plurality of electrodes 35 each have the same wiring width and the same length as the plurality of electrodes 34, and are arranged so as to overlap each other in a plan view. The distance between the plurality of electrodes 35 is the same as the distance between the plurality of electrodes 34. The plurality of electrodes 35 are electrically separated from each other, and voltage control can be performed individually for the plurality of electrodes 35. The voltage control of the electrode 35 is performed by the main control unit.

The plurality of electrodes 34 have an array pitch d1. Taking the electrode 34-1 as an example, the arrangement pitch is the sum of the width of the electrode 34-1 and the distance between the electrode 34-1 and the electrode 34-2. Similarly, the plurality of electrodes 35 have an array pitch d1.

The pair of electrodes 34 and 35 facing each other and the liquid crystal layer provided between the pair of electrodes 34 and 35 form one phase shifter. Therefore, the scanning element 13 can control the phase of light for each pair of electrodes 34 and 35.

As shown in FIG. 8, the electrode 35 may be composed of a planar electrode having a size covering a plurality of electrodes 34. Further, although not shown, the electrode 34 may be composed of a planar electrode having a size covering a plurality of electrodes 35. Even with such an electrode structure, it is possible to perform the same voltage control on the liquid crystal layer.

As the scanning element 13, a transmissive liquid crystal element (transmissive LCOS) using an LCOS (Liquid Crystal on Silicon) method may be used. By using the transmissive LCOS, the electrodes 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 the transparent substrate) is used. Since the silicon substrate transmits light (including infrared rays) having a wavelength equal to or higher than a specific wavelength in relation to the band gap, LCOS can be used as a transmissive liquid crystal element. By using LCOS, the cell electrode can be made into a smaller liquid crystal element, so that the size can be further reduced. Further, since the mobility of the liquid crystal molecules is high, it is possible to scan the laser beam at high speed.

[2-3] Configuration of the light receiving unit 14 Next, the configuration of the light receiving unit 14 will be described. FIG. 9 is a schematic cross-sectional view showing the configuration of the light receiving unit 14. The light receiving unit 14 includes an angle limiting element 15, a condenser lens 21, and a light receiving element (PD) 16.

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

When 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, at a refraction angle of 0 degrees. When the emission angle by the scanning element 13 is 0 degrees, 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 an optical phased array. The optical phased array includes a plurality of phase shifters that change the phase of light. The angle limiting element 15 is composed of, for example, a liquid crystal element. The angle limiting element 15 includes a plurality of regions divided along one direction, and it is possible to control the phase of light in each of the plurality of regions. The specific configuration of the angle limiting element 15 will be described later.

The laser beam transmitted through the angle limiting element 15 passes through the condenser lens 21. The condenser lens 21 is composed of, for example, a biconvex lens. The condenser lens 21 concentrates the laser beam at a predetermined refraction angle. By providing the condenser lens 21, the size of the light receiving element 16 can be reduced. The laser beam transmitted through the condenser lens 21 is incident on the light receiving element 16.

(Structure of angle limiting element 15)
Next, the configuration of the angle limiting element 15 will be described. FIG. 10 is a plan view of the angle limiting element 15. FIG. 11 is a cross-sectional view of the angle limiting element 15 along the BB'line of FIG.

The angle limiting element 15 has the same configuration as the scanning element 13 described above, except that the arrangement pitch is different.

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 electrodes 44. Although FIG. 11 illustrates five electrodes 44-1 to 44-5, the number of electrodes 44 can be set arbitrarily. A plurality of electrodes 45 are provided on the substrate 41. FIG. 11 illustrates five electrodes 45-1 to 45-5.

The plurality of electrodes 45 are provided corresponding to the plurality of electrodes 44. That is, the plurality of electrodes 45 each have the same wiring width and the same length as the plurality of electrodes 44, and are arranged so as to overlap each other in a plan view. The distance between the plurality of electrodes 45 is the same as the distance between the plurality of electrodes 44.

The plurality of electrodes 44 are electrically separated from each other, and voltage control can be performed individually for the plurality of electrodes 44. The voltage control of the electrode 44 is performed by the main control unit. Similarly, the plurality of electrodes 45 are electrically separated from each other, and voltage control can be performed individually for the plurality of electrodes 45. The voltage control of the electrode 45 is performed by the main control unit.

The plurality of electrodes 44 have an array pitch d2. Similarly, the plurality of electrodes 45 have an array pitch d2.

The pair of electrodes 44 and 45 facing each other and the liquid crystal layer provided between the pair of electrodes 44 and 45 form one phase shifter. Therefore, the angle limiting element 15 can control the phase of light for each pair of electrodes 44 and 45.

As in the case of the scanning element 13, the electrode 45 may be composed of a planar electrode having a size that covers the plurality of electrodes 44. Further, the electrode 44 may be composed of a planar electrode having a size covering a plurality of electrodes 45.

[2-4] Arrangement Pitch Conditions Next, the relationship between the arrangement pitch d1 of the scanning element 13 and the arrangement pitch d2 of the angle limiting element 15 will be described.

In the present embodiment, among the diffracted light emitted from the scanning element 13, even if the diffracted light other than the 0th-order light (+1st-order light, -1st-order light, etc.) is reflected by an unintended object, it is other than the 0th-order light. It suppresses the reflected light related to the diffracted light of the above from being incident on the light receiving element PD. Therefore, the arrangement pitch d1 of the scanning element 13 and the arrangement pitch d2 of the angle limiting element 15 have a relationship of “d1 ≠ d2”.

It is desirable that only the 0th-order light overlaps with the light-emitting side (scanning element 13) and the light-receiving side (angle limiting element 15), and the diffracted light of higher order does not overlap. The diffraction order m of the scanning element 13 and the diffraction order n of the angle limiting element 15 are set. m and n are natural numbers. The arrangement pitch d1 of the scanning element 13 and the arrangement pitch d2 of the angle limiting element 15 have a relationship of “m · d1 ≠ n · d2”.

When the light projection performance is emphasized, the arrangement pitch d1 is the minimum feasible phase shifter width, and the arrangement pitch d2 is set based on this value. As the arrangement pitch d2 increases, the angle of light taken into the light receiving element increases. Therefore, it is desirable that the arrangement pitch d2 be as small as possible. When "d2 / d1" becomes an integer p, the diffraction of any order q of d1 and the diffraction of the "p · q" order of d2 almost coincide with each other. Therefore, it is desirable that the array pitch d2 is larger than the array pitch d1 and is set in a range in which the order multiple of d1 and the order multiple of d2 do not match. Therefore, in the case of "d1 <d2", an appropriate arrangement pitch d2 can be obtained from the following equation (1).

d2 = d1 ・ (1 + 1 / (N + 1)) ・ ・ ・ (1)

N is the absolute value of the maximum diffraction order on the floodlight side that can be a noise factor.

On the other hand, when it is desired to minimize the arrangement pitch d2 on the light receiving side (angle limiting element 15), “d1> d2”. Further, an appropriate pitch d1 can be obtained from the following equation (2).

d1 = d2 ・ (1 + 1 / (M + 1)) ・ ・ ・ (2)

M is an absolute value of the maximum diffraction order on the light receiving side that can cause noise.

[3] Operation of the distance measuring device 10 [3-1] Basic operation of the distance measuring device 10 First, the basic operation of the distance measuring device 10 will be described. FIG. 12 is a schematic diagram illustrating the basic operation of the distance measuring device 10. Note that FIG. 12 shows, as an example, a mode in which the distance measuring device 10 scans the front of the vehicle 1.

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

FIG. 13 is a diagram illustrating a waveform of a laser beam generated by the distance measuring device 10. The upper side of FIG. 13 is the waveform of the projected light, and the lower side is the waveform of the received light. The horizontal axis of FIG. 13 is time, and the vertical axis of FIG. 13 is intensity (light intensity).

The light emitting element 12 emits a laser beam 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 a laser beam as a pulse signal. Let the period P of the pulse signal and the pulse width W. Let the delay amount Δ, which is the time from the transmission of one pulse to the reception of the pulse reflected by the object, and the speed of light C. 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.

[3-2] Scanning operation of the distance measuring device 10 In order to improve the signal strength, it is necessary to cut the disturbance light such as sunlight which becomes a disturbance. While the ambient light is incident from all angles, the signal is returned only from the angle emitted from the distance measuring device 10. Therefore, the signal strength is improved by receiving the laser beam by limiting the angle at which the signal is returned.

FIG. 14 is a flowchart illustrating the operation of the distance measuring device 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 with each other. Synchronization means that the refraction angle of the scanning element 13 and the refraction angle of the angle limiting element 15 are made the same.

FIG. 15 is a schematic diagram illustrating the operation of the scanning element 13. For example, the main control unit 19 applies an effective voltage that increases in this order to the electrodes 34-1 to 34-5. The voltage applied between the electrode 34 and the electrode 35 is an AC voltage. As a result, a gradient of the refractive index is generated in the scanning element 13.

Similarly, the main control unit 19 applies an effective voltage that increases in this order to the electrodes 44-1 to 44-5 of the angle limiting element 15. The voltage applied between the electrode 44 and the electrode 45 is an AC voltage. As a result, the angle limiting element 15 has the same refractive index gradient as the scanning element 13.

Subsequently, the main control unit 19 projects laser light from the light projecting unit 11 at an emission angle θ (step S101). Specifically, the pulse timing control unit 17 emits a pulsed laser beam from the light emitting element 12. The laser beam from the light emitting element 12 passes through the scanning element 13 and is refracted by an angle θ. In the example of FIG. 15, the refractive index of the scanning element 13 decreases toward the right side. Therefore, the laser beam incident from the substrate 30 side is refracted to the left side and emitted from the scanning element 13.

Subsequently, the light receiving unit 14 receives the laser light incident at the incident angle θ (step S102). Specifically, as shown in FIG. 9, the angle limiting element 15 refracts the laser beam incident at the incident angle θ in the direction perpendicular to the incident surface (at a refraction angle of 0 degrees). The laser beam transmitted through the angle limiting element 15 is incident on the light receiving element 16. As a result, the angle limiting element 15 can limit the laser light incident on the light receiving element 16 to the laser light incident on the incident angle θ.

Here, the laser light emitted from the scanning element 13 includes diffracted light such as +1st order light and -1st order light in addition to the desired laser light (0th order light). The emission angles of the +1st order light and the -1st order light are different from the emission angles of the 0th order light. For example, the +1st order light emitted from the scanning element 13 may be reflected by an unintended object, and this reflected light may be incident on the angle limiting element 15. However, in the present embodiment, since the arrangement pitch d1 of the scanning element 13 and the arrangement pitch d2 of the angle limiting element 15 are different, the reflected light of the +1st order light is not refracted by the angle limiting element 15 at a refraction angle of 0 degrees. That is, the reflected light of the +1st order light is not incident on the light receiving element 16. Similarly, other high-order diffracted light is not incident on the light receiving element 16.

Further, even when unwanted disturbance light (including sunlight) other than the 0th-order light is incident on the angle limiting element 15, it is possible to suppress the disturbance light from being incident on the light receiving element 16. In FIG. 9, desirable reflected light (light used as a signal) is indicated by a solid arrow, and unwanted disturbance light is indicated by a dashed arrow.

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 light from the pulse timing control unit 17, the information on the emission angle of the laser light from the main control unit 19, and the timing of the received laser light. Information and light intensity information are received from the light receiving element 16. The distance calculation unit 18 uses this information to calculate the distance from the vehicle to the object.

[4] Example Next, an embodiment of the light projecting unit 11 will be described. FIG. 16 is a schematic view showing the configuration of the light projecting unit 11 according to the embodiment. In FIG. 16, the collimator 20 is not shown.

A plano-concave lens 22 is provided on the exit surface side of the scanning element 13. The plano-concave lens 22 is arranged so that its plane faces the scanning element 13. The plano-concave lens 22 diffuses the laser beam. That is, the plano-concave lens 22 emits laser light at an emission angle (refraction angle) θ'that is 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. 17 is a schematic diagram showing the configuration of the light receiving unit 14 according to the embodiment.

A plano-concave lens 23 is provided on the incident surface side of the angle limiting element 15. The plano-concave lens 23 is arranged so that its plane faces the angle limiting element 15. The plano-concave lens 23 refracts the laser beam incident on the concave surface side at the incident angle θ'at the 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.

[5] Effects of the Embodiment As described in detail above, in the present embodiment, the distance measuring device 10 has a light emitting element 12 that emits laser light and a plurality of first phase shifters PS1, and the light emitting element 12 emits light. An angle limiting element (second deflection element) 15 having a scanning element (first deflection element) 13 for refracting the laser beam and a plurality of second phase shifters PS2 and refracting the laser beam reflected by the object. And a light receiving element 16 for detecting the laser beam transmitted through the angle limiting element 15. Then, the arrangement pitch d1 of the first phase shifter PS1 is set to be different from the arrangement pitch d2 of the second phase shifter PS2. Further, the scanning element 13 projects the laser light at the emission angle of the angle θ, and the angle limiting element 15 causes the laser light incident at the incident angle of the angle θ to be incident on the light receiving element 16.

Since the arrangement of the plurality of phase shifters PS1 of the scanning element 13 has periodicity, the laser light emitted from the scanning element 13 includes diffracted light including 0th-order light, +1st-order light, and -1st-order light. Is done. However, since the arrangement pitch d2 of the angle limiting element 15 is different from the arrangement pitch d1 of the scanning element 13, the reflected light caused by the +1st order light is not refracted toward the light receiving element 16 when passing through the angle limiting element 15. Similarly, other high-order diffracted light is not refracted toward the light receiving element 16.

Therefore, according to the present embodiment, it is possible to effectively capture the main signal component to be projected and suppress the reception of diffracted light that becomes noise. Thereby , the reception strength can be improved and the SN ratio can be improved.

Further, the distance measuring device 10 may receive the transmitted laser light limited to the laser light reflected by the object among the light incident on the distance measuring device 10 (including ambient light such as sunlight). can. Thereby, the reception strength can be improved. Further, since it is possible to detect a signal at a long distance, it is possible to improve the measurable distance.

In the above embodiment, the scanning element 13 that scans the laser beam one-dimensionally is described as an example. However, a passive matrix method arranged so that the plurality of lower electrodes and the plurality of upper electrodes intersect may be applied to the scanning element 13. By applying the passive matrix method to the scanning element 13, it is possible to scan in two dimensions. The angle limiting element 15 can be configured in the same manner as the scanning element 13.

Further, as another configuration example of the scanning element 13 and the angle limiting element 15, a plurality of first electrodes corresponding to a plurality of dots and electrically separated from each other are formed on the first substrate and face the first substrate. One planar common electrode is formed on the second substrate. Then, a plurality of first electrodes may be driven by using a plurality of switching elements composed of a TFT (Thin Film Transistor) or the like.

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

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

The present invention is not limited to the above embodiment, and the constituent elements can be modified and embodied within a range that does not deviate from the gist thereof. Further, the above-described embodiments include inventions at various stages, and by an appropriate combination of a plurality of components disclosed in one embodiment or by an appropriate combination of components disclosed in different embodiments. Various inventions can be constructed. For example, even if some components are deleted from all the components disclosed in the embodiment, if the problem to be solved by the invention can be solved and the effect of the invention is obtained, these components are deleted. The embodiment described above can be extracted as an invention.

10 ... distance measuring device, 11 ... light emitting unit, 12 ... light emitting element, 13 ... scanning element, 14 ... light receiving unit, 15 ... angle limiting element, 16 ... light receiving element, 17 ... pulse timing control unit, 18 ... distance calculation unit , 19 ... Main control unit, 20 ... Collimeter, 21 ... Condensing lens, 22, 23 ... Plano-concave lens, 30, 31 ... Substrate, 32 ... Liquid crystal layer, 33 ... Sealing material, 34, 35 ... Electrodes, 40, 41 ... Substrate, 42 ... Liquid crystal layer, 43 ... Sealing material, 44, 45 ... Electrodes

Claims (4)

A light emitting element that emits laser light and
A first deflection element that refracts the laser beam emitted by the light emitting element, and
A second deflection element that refracts the laser beam reflected by the object,
A light receiving element for detecting a laser beam transmitted through the second deflection element is provided.
The first deflection element is
1st and 2nd boards,
The first liquid crystal layer filled between the first and second substrates,
A plurality of first electrodes provided on the first substrate, each extending in the first direction,
A second electrode provided on the second substrate and having a size covering the plurality of first electrodes is included.
The second deflection element is
With the 3rd and 4th boards
The second liquid crystal layer filled between the third and fourth substrates, and
A plurality of third electrodes provided on the third substrate, each extending in the first direction,
A fourth electrode provided on the fourth substrate and having a size covering the plurality of third electrodes is included.
The plurality of first electrodes have the same width and are arranged at the same interval.
The plurality of third electrodes have the same width and are arranged at the same interval.
A distance measuring device in which the first pitch of the plurality of first electrodes is different from the second pitch of the plurality of third electrodes. The second electrode includes a plurality of electrode portions configured to overlap each of the plurality of first electrodes in a plan view.
The distance measuring device according to claim 1, wherein the fourth electrode includes a plurality of electrode portions configured to overlap each of the plurality of third electrodes in a plan view. The first deflection element projects a laser beam at an emission angle of the first angle.
The distance measuring device according to claim 1 or 2, wherein the second deflection element causes a laser beam incident at an incident angle of the first angle to be incident on the light receiving element. Assuming that the first pitch d1, the second pitch d2, the diffraction order m (m is a natural number) of the first deflection element, and the diffraction order n (n is a natural number) of the second deflection element, the first pitch d1 , And the second pitch d2
m ・ d1 ≠ n ・ d2
The distance measuring device according to any one of claims 1 to 3, which has the relationship of.

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