JP5644437B2 - Distance measuring device and distance measuring method - Google Patents

Description

  The present invention relates to a distance measuring apparatus and a distance measuring method for measuring a distance to a measuring object by irradiating the measuring object with a light beam.

  Currently, in order to improve the safety of traveling vehicles, measure the distance between vehicles to keep the distance between traveling vehicles constant, or measure the distance to obstacles ahead of the traveling vehicle, and take the risk to the driver. The development of a system that can inform is in progress. For example, in order to measure the distance to another measurement object such as another traveling vehicle or an obstacle located in front of the traveling vehicle, the distance of the measurement object in front of the vehicle is scanned using a polygon mirror. Various distance measuring devices that measure the distance have been proposed.

As shown in FIG. 13, in the distance measuring apparatus 100, the laser light source 102 irradiates the pulsed laser beam L toward the front of the traveling vehicle, and the laser beam L is irradiated to return from the measurement object 104. The light receiver 106 receives the reflected beam R, which is the scattered light, and measures the time T from the emission of the laser beam L to the reception of the reflected beam R, thereby obtaining the distance information of the measurement object 104.
At this time, as shown in FIG. 14, the laser beam L emitted from the laser light source 102 is deflected in the irradiation direction of the laser beam L using the polygon mirror 108 to scan the front of the traveling vehicle. Thereby, in the distance measuring apparatus 100, the scanning range of the laser beam L becomes a range of several tens of degrees around the polygon mirror 108.

  On the other hand, recently, camera systems that provide drivers with information on objects to be measured such as vehicles and obstacles positioned in front of or behind a traveling vehicle are being installed in many vehicles. In this in-vehicle camera system, as shown in FIG. 15, the field of view taken in front of the traveling vehicle 110 is often over 180 degrees by using an ultra-wide angle lens. It is preferable for the driver to provide the driver with information on the distance to the measurement object in addition to providing the driver with image information relating to the measurement object such as a vehicle or an obstacle.

  Under such circumstances, laser range detection devices that use a pulse travel time method to determine the position of an object in the spatial domain are known. The laser range detection device considers a light beam, a pulse laser that sends a light pulse to a measurement region while controlling the light pulse, a light detection unit that receives a light pulse reflected from a measurement object arranged in the measurement region, and a light beam. And an evaluation circuit for determining a distance signal characteristic with respect to the distance from the pulse laser to the object from the time between the transmission and reception of the light pulse. At this time, a rotating mirror is used for laser scanning, but the reflecting surface of the rotating mirror is inclined so as to form an angle of 45 degrees with respect to the rotation axis.

In addition, a laser radar and a boundary monitoring method using a laser radar are known that can perform a wide range of monitoring along the boundary while suppressing an increase in monitoring cost.
The laser radar includes a scanning unit that scans laser light emitted from two light projecting units and two light receiving units that receive reflected laser light reflected and returned from the measurement target region. The scanning unit includes a polygon mirror, In addition, scanning laser beams from the two light projecting portions reflected by the polygon mirror are provided, and a oscillating mirror for individually returning the reflected laser beams reflected by the measurement object and returning to the light receiving portion through the polygon mirror is provided. One light projecting unit and light receiving unit and the other light projecting unit and light receiving unit are arranged with a polygon mirror interposed therebetween, and the angle formed by each optical axis is set to an acute angle.

Japanese Patent Laid-Open No. 6-214027 JP 2010-71725 A

In the laser range detection apparatus described above, the incident optical path of the laser from the laser light source to the rotating mirror is parallel to the rotation axis direction and orthogonal to the irradiation direction of the laser to be scanned. For example, when irradiating the laser in the horizontal direction, The laser light source is provided at a position vertically above or vertically below the rotating mirror. As a result, the laser range detection device is bulky and has a large occupied volume, and the laser range detection device may not be mounted compactly in front of or behind the vehicle.
In addition, since the laser radar used in the above-described boundary monitoring method uses a polygon mirror, a part of the region is not irradiated with the laser and cannot be measured. Further, the laser radar is wider than 180 degrees around the rotation axis of the polygon mirror. The laser beam cannot scan the area.

  Therefore, the present invention provides a distance measuring apparatus and a distance measuring method for irradiating a measurement object with a light beam and measuring the distance to the measurement object, and can widen the scanning range of the light beam as compared with the related art. An object of the present invention is to provide a distance measuring device and a distance measuring method that can be used.

One embodiment of the present invention is a distance measurement device that measures a distance to a measurement target by irradiating the measurement target with a light beam.
The distance measuring device is
A beam emitting unit for emitting a plurality of light beams having different directions to irradiate the measurement object;
A light receiving unit for receiving the reflected beam reflected from the measurement object and returned;
A data processing unit for obtaining distance information of a measurement object using a reflected beam received by the light receiving unit;
A beam scanning unit that scans each of the plurality of light beams emitted from the beam emitting unit.
The beam scanning unit includes a plurality of reflection mirrors, and a rotation driving unit that rotates the reflection mirror so as to have a rotation axis along a reflection surface of the reflection mirror, and the plurality of light beams reflect the reflection light. The light enters the position of the rotation axis on the reflection surface of the mirror from different directions.
The reflecting mirrors are arrayed mirrors arranged in multiple stages in the direction of the rotation axis, and the directions of the reflecting surfaces are different from each other, and each of the arraying mirrors receives incident one of the plurality of light beams. Receive .

Another embodiment of the present invention is a distance measurement method for measuring a distance to a measurement object by irradiating the measurement object with a light beam.
The distance measurement method is
Each of a plurality of light beams having different directions is emitted from the beam emitting unit,
Measuring by reflecting the plurality of light beams at a position of the rotation axis on a reflection surface of one or more reflection mirrors having a rotation axis along the reflection surface and rotating about the rotation axis. Irradiate the object with each of the light beams;
The reflected beam reflected and returned by the measurement object by irradiation of the light beam is reflected by the reflecting mirror and received.
Using the received reflected beam, distance information to the measurement object is obtained.
At this time, each of the array mirrors arranged in a plurality of stages in the direction of the rotation axis and having different reflective surfaces from each other receives one incidence of the plurality of light beams, so that each of the array mirrors is the reflection mirror. Used as

  According to the distance measuring apparatus and the distance measuring method of the above-described aspect, the scanning range of the light beam can be widened as compared with the conventional case.

It is a figure which shows the form which mounted the distance measuring device of this embodiment in the passenger car. 1 is a perspective view showing a configuration of a distance measuring device according to a first embodiment. (A)-(c) is a figure explaining incident and reflection of a reflective mirror and a laser beam. It is a figure explaining the scanable range of the laser beam of 1st Embodiment. It is a figure which shows the flow of the distance measuring method performed in the distance measuring device of 1st Embodiment. (A), (b) is a figure explaining the reflective mirror of the beam scanning part of the modification of 1st Embodiment. (A), (b) is a figure explaining the modification of 1st Embodiment. It is a figure which shows the structure of the outline of the distance measuring device of 2nd Embodiment. It is a figure which shows the flow of the distance measuring method in the distance measuring device of 2nd Embodiment. It is a figure which shows the structure of the outline of the distance measuring device of 3rd Embodiment. It is a figure explaining the polarization state of the laser beam of 3rd Embodiment, and a reflected beam. It is a figure which shows the flow of the distance measuring method in the distance measuring device of 3rd Embodiment. It is a figure explaining distance measurement of the conventional distance measuring device. It is a figure explaining the scanning method of the laser beam in the conventional distance measuring device. It is a figure explaining the scanning range in the conventional distance measuring device, and the visual field range of a vehicle-mounted camera system.

Hereinafter, the distance measuring device and the distance measuring method of the present invention will be described.
FIG. 1 is a diagram showing a form in which a distance measuring device 10 is mounted on a passenger car 1. The distance measuring device 10 according to the present embodiment is a device that is mounted in front of the passenger car 1 and obtains distance information of an object to be measured such as another passenger car or an obstacle located in front of the passenger car 1. The distance measuring device 10 outputs the obtained distance information to a data processing device of an in-vehicle camera system (not shown). This distance information is used as a distance to an object to be photographed in an image photographed by the in-vehicle camera system, and is used to issue a warning or an alarm to the driver that the object is too close to the measurement object.

Similar to the conventional distance measuring device, the distance measuring device 10 emits a pulsed laser beam to irradiate the measuring object, and receives the reflected beam reflected and returned by the measuring object. At this time, the distance measuring device 10 measures the distance of the measurement object using the time difference between the emission of the laser beam and the reception of the reflected beam, similarly to the conventional distance measuring device 100 shown in FIG. The distance measuring device 10 measures a distance of a measuring object located in a wide range in front of the vehicle by using a laser beam around the distance measuring device 10 and exceeding 180 degrees around the front direction X of the passenger car 1. Scan to range. This scanning range is wider than the scanning range when using a conventional polygon mirror, and is equivalent to the visual field range of an image captured by the in-vehicle camera system. For this reason, the actual distance information of the measurement object in the image captured by the in-vehicle camera system can be provided to the driver, and the driver can be alerted and alarmed reliably.
In each embodiment described below, a laser beam is used. However, the present invention is not limited to the laser beam, and may be a light beam including infrared rays and ultraviolet rays emitted from various light sources such as LEDs.

(First embodiment)
FIG. 2 is a perspective view showing the configuration of the distance measuring device 10 of the first embodiment. The distance measuring device 10 scans a laser beam over a wider range than the conventional distance measuring device 100. The distance measuring device 10 includes a beam emitting unit 12, a light receiving unit 14, a data processing / control unit 16, and a beam scanning unit 18.
Beam emitting portion 12 is provided with a pulsed laser beam (hereinafter, a beam of) the laser light source 12a that emits L _1, a laser light source 12b for emitting a pulsed beam L _2, the. The laser light source 12a and the laser light source 12b intermittently emit beams in directions different from each other. The laser beam is emitted from the beam emitting unit 12 in accordance with a control signal supplied from the data processing / control unit 16.
As the laser light sources 12a and 12b, for example, semiconductor laser light sources that emit laser light in the near infrared region having a wavelength of 780 nm to 950 nm are used.

The light receiving unit 14 includes half mirrors 14a and 14b and photodiodes 15a and 15b. The half mirrors 14a and 14b are optical elements that transmit approximately half of the incoming light and reflect the other approximately half. The half mirrors 14 a and 14 b are provided between the beam emitting unit 12 and the beam scanning unit 18, and reflect a reflected beam coming from the measurement object as a result of the beam being reflected by the measurement object. The beams L ₁ and L ₂ emitted from the laser light sources 12 a and 12 b are transmitted through the half mirrors 14 a and 14 b and guided to the beam scanning unit 18. In Figure 2, the beam L ₁ is emitted from the laser light source 12a, it shows a state in which the beam L ₂ is not emitted from the laser light source 12b.
The photodiodes 15a and 15b are elements that receive a pulsed reflected beam obtained by reflecting the pulsed beams L ₁ and L ₂ by the measurement object and output a light reception signal. In the present embodiment, the photodiodes 15a and 15b are used as light receiving sensors in the light receiving unit 14, but other known photoelectric conversion elements can be used.

The data processing / control unit 16 uses the reflected beam received by the light receiving unit 14 to obtain distance information from the distance measuring device 10 to the measurement object. Further, the data processing / control unit 16 generates a laser beam emission on / off control signal and supplies it to the laser light sources 12a and 12b. Specifically, the data processing / control unit 16 intermittently transmits the beams L ₁ and L ₂ in accordance with position information of reflection mirrors 18 a and 18 b (see FIG. 2) provided from a rotation driving unit 20 described later. On / off control signals for the emission of the beams L ₁ and L ₂ are generated so as to be emitted.
When obtaining the distance information to the measurement object, the data processing / control unit 16 receives a pulsed light reception signal obtained by receiving light with the photodiodes 15a and 15b, and receives the pulsed beams L ₁ and L ₂ . The delay time of the pulsed light reception signal with respect to the emission timing is calculated. Since the data processing / control unit 16 generates on / off control signals for laser beam emission, the data processing / control unit 16 obtains information on the emission timings of the beams L ₁ and L ₂ . Further, the data processing / control unit 16 calculates distance information from the distance measuring device 10 to the measurement object by multiplying the calculated delay time by the speed of light, and this distance information is used as data of an in-vehicle camera system (not shown). Provide to processing equipment.

The beam scanning unit 18 includes two reflecting mirrors 18 a and 18 b, a rotation driving unit 20, and a rotating body stage 21. A rotation shaft 19 extending from the rotation drive unit 20 on which the reflection mirrors 18a and 18b rotate is provided on the reflection surface of the reflection mirrors 18a and 18b along the reflection surface. FIGS. 3A to 3C are diagrams illustrating the incidence and reflection of the reflection mirrors 18a and 18b and the beams L ₁ and L ₂ .
Specifically, the reflection mirrors 18 a and 18 b of the beam scanning unit 18 are placed and fixed on the rotating body stage 21. The rotator stage 21 is fixed by the rotation drive unit 20 and a rotating shaft (not shown), and the rotator stage 21 and the reflection mirrors 18a and 18b rotate about the axis. The reflection mirrors 18a and 18b are array mirrors that are arranged in multiple stages on the rotating body stage 21 in the axial direction of the rotation shaft 19, and are arranged so that the directions of the reflection surfaces are different from each other. As shown in FIG. 3C, beams L ₁ and L ₂ enter the position of the rotation axis 19 on the reflection surfaces of the reflection mirrors 18a and 18b.

The reflection mirror 18a, depending on the orientation of the reflecting surface of the 18b, the beam _{L 1} and the beam L ₂ is selectively used. Specifically, as described later, the range of the left scanning beam L ₁ from the front direction X when viewed forward direction X in the front, the range from the front direction X of the right side viewed forward direction X in the front beam L ₂ is scanned. Further, when the direction of the rotary shaft 19 is the height direction Z, the optical paths of the beam L ₁ and the beam L ₂ between the beam emitting unit 12 and the beam scanning unit 18 are formed on a plane orthogonal to the height direction Z. Has been. That is, the laser light sources 12a and 12b are arranged such that the positions of the laser light sources 12a and 12b in the height direction Z are the same as the positions in the height direction Z of the beam incident points 22a and 22b on the reflection mirrors 18a and 18b. Is provided. In the example shown in FIG. 2, since the reflection mirror 18b is higher in the height direction Z than the reflection mirror 18a, the laser light source 12b is higher in the height direction Z than the laser light source 12a.
Thus, when the direction of the reflecting surface of the reflecting mirror 18a is shown in FIG. 3 (a), it receives the incident light beam L ₁ on the reflecting surface of the rotary shaft 19 a reflection mirror 18a, the reflection of the reflection mirror 18b When the orientation of the surface is as shown in FIG. 3B, the reflection mirror 18 b receives the light beam L ₂ on the reflection surface on the rotation shaft 19.

  The rotation drive unit 20 includes a drive motor (not shown) that rotates at a constant speed, and a rotation angle detector (not shown), such as a rotary encoder, for detecting the orientation of the reflection mirrors 18a and 18b. The pulse signal output from the rotation angle detector is sent to the data processing / control unit 16 and used to detect the orientation of the reflection mirrors 18a and 18b.

FIG. 4 is a diagram illustrating the scannable range of the beams L ₁ and L ₂ .
The scanning range of the beams L ₁ and L ₂ by the beam scanning unit 18 is a range around the rotation axis 19 with the forward direction X as the center, and the laser light sources 12a and 12b of the beam emitting unit 12 have the beam L ₁ , Each of L ₂ is emitted from the rear side with respect to the front direction X toward the position of the rotation shaft 19 on the reflection surfaces of the reflection mirrors 18a and 18b. Thus, the beam L ₁ reflected by the reflecting mirror 18a, as shown in FIG. 4, the range of theta = theta _in1 from 180 degrees + theta _in1, i.e., it is possible to scan the range A. In FIG. 4, the right axis among the left and right directions in the figure is θ = 0 degrees.
On the other hand, the beam L ₂ reflected by the reflecting mirror 18b, as shown in FIG. 4, it is possible to scan the range of theta = - [theta] _in2 from 180 - [theta] _in2, i.e. the range B. Here, θ _in1 represents the incident angle of the beam L ₁ with respect to the direction of θ = 180 degrees in FIG. 4, and θ _in2 represents the incident angle of the beam L ₂ with respect to the direction of θ = 0 degrees in FIG. .

The distance measuring device 10 uses a range A of the beam L _{1 and} a range B of the beam L ₂ as a scannable range that exceeds 180 degrees. One of the beams is emitted. More specifically, when θ = 90 degrees or less, the beam L ₂ is emitted, and when θ = 90 degrees is exceeded, the beam L ₁ is emitted. Thus, the emission of the laser light sources 12a and 12b is turned on / off. Are switched according to the orientation of the reflecting surfaces of the reflecting mirrors 18a, 18b. In the present embodiment, the beams L ₁ and L ₂ are not emitted at the same time, but the beams L ₁ and L ₂ can be emitted at the same time to calculate distance information at the same time.

FIG. 5 is a diagram illustrating a flow of a distance measuring method performed in the distance measuring apparatus 10.
In the distance measuring device 10, the motor of the rotation driving unit 20 starts driving in accordance with a driving instruction from the data processing / control unit 16 (step S10). Along with this, the data processing / control unit 16 receives a pulse signal output from a rotation angle detector such as a rotary encoder, and acquires information on the rotation angle of the motor (step S20). Since the pulse signal output from the rotation angle detector outputs several thousand pulse signals during one rotation of the rotating shaft 19, information on the rotation angle can be obtained accurately by counting the pulses.
The data processing / control unit 16 obtains the directions of the reflecting surfaces of the reflecting mirrors 18a and 18b using the acquired information on the rotation angle, and further emits beams L ₁ and L ₂ from the direction of the reflecting surfaces. A measurement angle representing the expected scanning position is calculated (step S30). Alternatively, the measurement angles of the beams L ₁ , L ₂ are rotation angles obtained from a rotation angle detector using a previously recorded relationship between the rotation angle of the rotary shaft 19 and the measurement angle of the laser beam as a reference table. The measurement angle can be obtained from the information.

Next, the data processing / control unit 16 determines whether or not the measurement angle θ ₁ of the beam L ₁ is more than 90 degrees and within 180 degrees + θ _in1 when the beam L ₁ is emitted (step S40). .
In the above determination, if the measured angle theta ₁ is within 180 degrees + theta _in1 beyond 90 degrees (in the case of Yes is selected in step S40), the control signal to the laser light source 12a such that the laser light source 12a emits a beam _{L 1} provide. Thus the beam _{L 1} is emitted from the laser light source 12a (step S50). Beam L ₁ is transmitted through the half mirror 14a, reflected by the reflecting mirror 18a, it is emitted in the direction of the measurement angle theta _1. The reflected beam is a reflected light beam L ₁ in the measurement object positioned to measure the angle theta ₁ is returned to the reflecting mirror 18a, the flow returns to the half mirror 14a passes through the same optical path as beam L _1. The reflected beam reflected by the half mirror 14a is received by the photodiode 15a and a light reception signal is output (step S60).

On the other hand, in the determination (in the case of No in step S40) measured when the angle theta ₁ is not within a range of 180 degrees + theta _in1 beyond 90 degrees, the data processing and control unit 16, upon exiting the beam L ₂ or measuring angles theta ₂ of the beam L ₂ is within 90 degrees from the - [theta] _in2, judges whether (step S70). In the determination, measurement (Yes in Step S70) angle theta ₂ be in a range within 90 degrees from the - [theta] _in2, as the laser light source 12b emits a beam L _2, the data processing and control unit 16 The control signal is provided to the laser light source 12b. Thus the beam L ₂ is emitted from the laser light source 12b (step S80). Beam L ₂ passes through the half mirror 14b, is reflected by the reflecting mirror 18b, is irradiated in the direction of the measurement angle .theta.2. The reflected beam, which is the reflected light of the beam L _{2 on} the measurement object, returns to the reflecting mirror 18 b and returns to the half mirror 14 b through the same optical path as the beam L ₂ . The reflected beam reflected by the half mirror 14b is received by the photodiode 15b and a received light signal is output (step S90).

On the other hand, in the judgment in the step S70, (the case of No in step S70) beam if the measurement angle theta ₂ of the beam L ₂ when L ₂ has the emission is not within the range of - [theta] _in2 within 90 degrees, the beam _{L 1} and any of the beam L ₂ is not emitted, the process returns to step S20, the beam _L 1, L ₂ is not emitted until the determination of step S40 or step S70 is affirmative.

Next, the data processing / control unit 16 measures the distance of the measurement object (step S100). Specifically, using a photo diode 15a or the light receiving signal of the shaped pulse outputted from the photo diode 15b, and calculates the delay time for the timing of the pulsed beam L ₁ or beam L ₂ emitted, this delay time By multiplying the speed of light and dividing by 2, the distance information from the distance measuring device 10 to the measurement object is obtained. The obtained distance information data is output to a data processing device of an in-vehicle camera system (not shown) (step S110). The delay time is obtained by correcting a control signal for emission of the beam L ₁ and the beam L ₂ , a delay time due to transmission of the received light signal, a response delay time in the apparatus, and the like. Above steps S20~S100 after start of driving the motor is performed continuously, the distance measurement because performed each time the output beam L ₁ and the beam L _2, the data of the distance information is output in real time.

As described above, the rotation shaft 19 of the reflection mirrors 18a and 18b is provided on the reflection surfaces of the reflection mirrors 18a and 18b of the distance measuring device 10 along the reflection surface, and the beams L ₁ and L ₂ are reflected by the reflection mirrors. The light beams are incident on the rotary shaft 19 on the reflecting surfaces 18a and 18b from different directions. For this reason, the distance measuring apparatus 10 can scan the beams L ₁ and L ₂ in the range from −θ _in2 to 180 degrees + θ _in1 without a blind spot. That is, the scanning range of the laser beam can be widened compared to the conventional case.
Light beam scanning unit 19, and a multi-stage arrangement in the direction of the rotary shaft 19, different sequences mirror the orientation of the reflective surface each other, the reflection mirror 18a, includes a 18b, each of the array mirrors, beam L _1, L ₂ One of the beams is incident. For this reason, the scanning range can be controlled separately by the beams L ₁ and L ₂ , and the scanning can be efficiently performed using the two beams.
Beam emitting portion 12, the beam _L 1, L ₂ each emission on and off, the reflecting mirror 18a, to switch according to the orientation of the reflecting surface of the 18b, intermittently any one of the beams _L 1, L ₂ Therefore, the distance of the measurement object in the desired scanning range can be measured.
In addition, since the optical path between the beam emitting unit 12 and the beam scanning unit 18 is formed on a plane perpendicular to the height direction Z along the rotation axis 19, the distance measuring device 10 is compared with the conventional one. And can be fixed in an empty space in front of the passenger car 1.
Since the beam emitting unit 12 emits each of the beams L ₁ and L ₂ from the rear side with respect to the front direction X toward the position of the rotation shaft 19, the distance measuring device 10 includes the beams L ₁ and L 2. ₂ can scan a range of 180 degrees or more around the rotation axis.
The distance measuring apparatus 10 is provided between the beam emitting unit 12 and the beam scanning unit 18, and reflects the reflected beam from the measurement object, and the reflected beam reflected by the half mirrors 14a and 14b. And photodiodes 15a and 15b that receive light. For this reason, the optical path of the reflection mirror can be shared with the optical paths of the beams L ₁ and L ₂ , and the distance measuring device 10 can be made compact.

FIGS. 6A and 6B are diagrams illustrating the configuration of the reflection mirror of the beam scanning unit 18, which is a modification of the first embodiment.
6A and 6B, unlike the first embodiment, two reflection mirrors 18a and 18b are not provided, and one of the reflection mirrors 18a is provided on the rotary stage 21. Since the configuration other than the reflection mirror 18a is the same as the configuration of the first embodiment, the description of the configuration other than the reflection mirror 18a is omitted.
The rotating shaft 19 on which the reflection mirror 18a rotates is provided on the reflection surface of the reflection mirror 18a of the beam scanning unit 18 along the reflection surface, and the beams L ₁ and L ₂ are on the reflection surface of the reflection mirror 18a. The light enters the position of the rotating shaft 19 from different directions.
Accordingly, as shown in FIG. 6 (a), when the reflecting mirror 18a to rotate a predetermined direction, the beam L ₁ laser light source 12a is emitted, measured angle theta ₁ of the beam L ₁ is greater than 90 degrees Scan to within 180 degrees + θ _in1 . Further, as shown in FIG. 6 (b), when the reflecting mirror 18a to rotate a predetermined direction, the beam L ₂ laser light source 12b is emitted, measured angle theta ₂ of the beam L ₂ from - [theta] _in2 90 Scan to within degrees.

As described above, the laser light sources 12a and 12b switch on and off the emission of the beams L ₁ and L ₂ in accordance with the direction of the reflection surface of the reflection mirror 18a, so that one of the beams L ₁ and L ₂ is selected. Since one beam is emitted intermittently, scanning can be performed by effectively using one reflecting mirror 18a.
At this time, since the optical path between the laser light sources 12a and 12b and the beam scanning unit 18 is formed on a plane orthogonal to the rotation axis 19, the distance measuring device 10 is not a bulky device. It can be arranged and fixed in an empty space in front of the passenger car 1.

FIG. 7A is a diagram for explaining a modification of the first embodiment. In the beam scanning unit 18 shown in FIG. 7A, a transparent body 24 is provided on a rotary stage 21 and is fixed. The transparent body 24 is made of, for example, quartz. In the transparent body 24, reflection mirrors 18a and 18b made of a metal thin film layer are formed. The reflection mirrors 18 a and 18 b are array mirrors arranged in multiple stages in the direction of the rotation shaft 19 and having different reflection surface directions. Reflection mirrors 18a receives the incident beam _{L 1,} reflective mirror 18b receives a incident beam L _2.
The reflection mirrors 18a and 18b are different from the reflection mirrors 18a and 18b shown in FIG. 2 only in that they are provided on the transparent body 24, and the transparent mirror 24 has the same configuration except for the transparent body 24. Description and operation of the other devices will be omitted.

FIG. 7B is a diagram for explaining another modified example of the first embodiment. In the beam scanning unit 18 shown in FIG. 7B, a transparent body 24 is provided on a rotary stage 21 and fixed. In the transparent body 24, a reflective mirror 18a is formed on one surface by a metal thin film layer, and a reflective mirror 18b is formed on the other surface. Since the metal thin film is thin, the rotation shaft 19 is provided on the reflection surfaces of the reflection mirror 18a and the reflection mirror 18b along the reflection surfaces.
Reflection mirrors 18a receives the incident beam _{L 1,} reflective mirror 18b receives the incident beam L _2. Unlike the reflection mirrors 18 a and 18 b shown in FIG. 2, the reflection mirrors 18 a and 18 b are provided in the transparent body 24, and the positions of the reflection mirror 18 a and the reflection mirror 18 b in the height direction Z along the rotation axis 19 are set. They are the same as each other. For this reason, the racer light sources 12a and 12b, the half mirrors 14a and 14b, and the photodiodes 15a and 15b are provided at the same position in the height direction Z, and the bulk in the height direction Z can be reduced. Can be made more compact. Since the configuration other than the transparent body 24 is the same as that of the distance measuring apparatus 10 shown in FIG. 2, description and operation of the apparatus other than the transparent body 24 are omitted.
In this modification, the reflecting mirror 18a receives the incident beam _{L 1,} the reflection mirror 18b receives the incident beam L _2, the reflecting mirror 18a, none of the 18b, the beam _L 1, L ₂ is incident May be. In this case, the beam scanning unit 18 can scan the range from −θ _in2 to 180 degrees + θ _in1 while the reflection mirrors 18a and 18b are rotated halfway.

(Second Embodiment)
FIGS. 8A and 8B are diagrams illustrating a schematic configuration of the distance measuring device 10 according to the second embodiment. In the second embodiment shown in FIGS. 8A and 8B, the beam emitting unit 12 uses one laser light source 12 a together with the collimator lens 13. In the second embodiment, shutters 25 a and 25 b and adjustment mirrors 26 a and 26 b are provided on the optical path between the beam emitting unit 12 and the beam scanning unit 18.
The collimator lens 13 converts the laser beam emitted from the laser light source 12a into parallel light. A half mirror 28 is provided in front of the laser light source 12a. The half mirror 28 is an optical element that separates the _two beams L ₁ and L ₂ by reflecting and transmitting one beam emitted from one laser light source 12a.

A rotating shaft 19 on which the reflecting mirrors 18a and 18b rotate is provided on the reflecting surfaces of the reflecting mirrors 18a and 18b of the beam scanning unit 18 along these reflecting surfaces. The reflection mirrors 18a and 18b receive the beams L ₁ and L ₂ from different directions at the position of the rotation axis 19 on the reflection surfaces of the reflection mirrors 18a and 18b.
As the reflection mirrors 18a and 18b, in addition to the first embodiment shown in FIG. 3A, the modification shown in FIGS. 6A and 6B, the modification shown in FIG. 7A, or FIG. 7B. Each form of the example may be used.
As shown in FIG. 8 (a), the beam _{L 1} is when entering the beam scanning unit 18, the shutter 25a is opened, is reflected by the adjustment mirror 26a, the beam _{L 1} is directed to a beam scanning unit 18. Incident to the reflective mirror 18a of the beam L ₁ is measured angle theta ₁ of the beam L ₁ when the emitted beam L ₁ is performed when it is within 180 degrees + theta _in1 beyond 90 degrees. As shown in FIG. 8B, when the beam L ₂ is incident on the beam scanning unit 18, the shutter 25 b is opened, reflected by the adjustment mirror 26 _b , and the beam L ₂ is guided to the beam scanning unit 18. Incident to the reflective mirror 18b of the beam L ₂ is measured angle theta ₂ of the beam L ₂ when the emitted beam L ₂ is performed when it is within 90 degrees from the - [theta] _in2. The beam L ₂ is emitted from the same laser light source 12 a as the beam L ₁ and is incident on the reflection mirror 18 b whose position in the height direction Z of the rotating shaft 19 is different from the reflection mirror 18 a, but the beam L ₂ is the adjustment mirror. The light is reflected so as to enter the reflection mirror 18b at 26b. Therefore, strictly speaking, the optical path of the beam L ₂ is not formed on a plane orthogonal to the rotation axis 19, and is inclined with respect to the plane by the positional deviation in the height direction Z of the reflection mirrors 18 a and 18 b. Yes. However, the reflection mirror 18a, the deviation amount of the position in the height direction Z of 18b, since sufficiently smaller than the optical path length, substantially, the optical path of the beam L ₂ has, on a plane perpendicular to the rotation axis 19 It can be said that it is formed.

FIG. 9 is a diagram illustrating a flow of a distance measurement method in the distance measurement device 10 of the second embodiment. Among the distance measurement methods in the second embodiment, steps S10 to S40, S60, S70, S90 to S110 shown in FIG. 9 are the same as steps S10 to S40, S60, S70, and S90 to S110 shown in FIG. The description is omitted. In the flow shown in FIG. 9, step S45 and step S75 are provided.
In step S45, (Yes in step S40) beam if the measurement angle theta ₁ of the beam _{L 1} when the _{L 1} emitted is within 180 degrees + theta _in1 beyond 90 degrees, open shutter 25a is, the shutter 25b is Close (step S45). In this state, pulsed laser beam is emitted from the laser light source 12a (step S50), is a parallel light through a collimator lens 13, the half mirror 28 is separated into beams L ₁ and the beam L _2. Beam L ₂ is progression to the beam scanning unit 18 is blocked by the shutter 25b is closed, only the beam L ₁ is directed to a beam scanning unit 18 passes through the shutter 25a opened.
Similarly, in step S75, the case measured angle theta ₂ of the beam L ₂ when the emitted beam L ₂ is within 90 degrees from the - [theta] _in2 (Yes in step S70), opens the shutter 25b is, the shutter 25a is Close (step S75). In this state, pulsed laser beam is emitted from the laser light source 12a (step S80), is a parallel light through a collimator lens 13, the half mirror 28 is separated into beams L ₁ and the beam L _2. Beam L ₁ is progression to the beam scanning unit 18 is blocked by the shutter 25a is closed, only the beam L ₂ is guided to the beam scanning unit 18 passes through the shutter 25b is opened.
Thus, the distance measuring apparatus 10 measures the distance of the measurement object by irradiating the measurement object from the beam scanning unit 18 intermittently with the pulsed beams L ₁ and L ₂ .
Step S20~S100 in Figure 9, after the start of the driving of the motor, is continuously performed, the distance measurement is performed for each of the outgoing beam L ₁ and the beam L _2, the data of the distance information is output in real-time (Step S110).

Therefore, the distance measuring device 10 of the second embodiment has the same effect as the distance measuring device 10 of the first embodiment. Furthermore, since the distance measuring device 10 of the second embodiment reflects and transmits the beam emitted from the laser light source 12a using the half mirror 28 and separates it into the beams L ₁ and L ₂ , the laser light source used is A single distance measuring device 10 can be provided.

(Third embodiment)
FIG. 10 is a diagram illustrating a schematic configuration of the distance measuring device 10 according to the third embodiment. In the third embodiment shown in FIG. 10, the beam emitting unit 12 uses one laser light source 12 a together with the collimator lens 13 as in the second embodiment. The light receiving unit 14 receives the reflected beam of the beam L ₁ coming from the measurement object and the reflected beam of the beam L ₂ coming from the measurement object by one photodiode 14.
Specifically, the beam emitting unit 12 includes a laser light source 12a, a collimator lens 13, a polarization beam splitter 29, and a liquid crystal plate 30. Quarter-wave plates 32 a and 32 b are provided on the optical paths of the beams L ₁ and L ₂ between the beam emitting unit 12 and the beam scanning unit 18. The light receiving unit 14 includes a photodiode 15a that receives the reflected beam.
The collimator lens 13 converts the laser beam emitted from the laser light source 12a into parallel light. The liquid crystal plate 30 is a polarization rotating element that controls the polarization state of one linearly polarized laser beam emitted from the beam emitting unit 12. The liquid crystal plate 30 is connected to a data processing / control unit 18 (see FIG. 2) similar to that of the first embodiment for measuring a measurement object for controlling the polarization state of the laser beam. In accordance with an instruction from the control unit 18, the polarization state of the laser beam is controlled. The polarization beam splitter 29 reflects or transmits the laser beam whose polarization state is controlled by the liquid crystal plate 30 and separates it into linearly polarized beams L ₁ and L ₂ having different polarization states from each other. An optical element that transmits or reflects a reflected beam from an object in accordance with the polarization state. Only the reflected beam that has passed through the polarization beam splitter 29 is received by the photodiode 15a.
The quarter-wave plates 32a and 32b convert the linearly polarized beams L ₁ and L ₂ polarized by the liquid crystal plate 30 into circularly polarized light and the circularly polarized reflected beam coming from the measurement object into linearly polarized light.
The photodiode 15 a receives the reflected beam from the measurement object transmitted or reflected by the polarization beam splitter 29 through the reflection mirrors 18 a and 18 b and the quarter-wave plates 32 a and 32 b of the beam scanning unit 18.

FIG. 11 illustrates the polarization state of the beam after the laser light source 12a emits the laser beam with 90-degree linearly polarized light until the reflected beam is received by the photodiode 15a.
Beams _L 1, L _2, like the first embodiment, the measurement angle theta ₁ of the beam _{L 1,} by measuring the angle theta ₂ of the beam L _2, the reflection mirror 18a of the beam scanning unit 18, is incident to 18b control Is done. More specifically, as measured angle theta ₁ of the beam L ₁ when the beam L ₁ is emitted is, if it is within 180 degrees + theta _in1 beyond 90 degrees, the beam L ₁ is incident on the beam scanning section 18 The liquid crystal plate 30 is controlled. Similarly, measuring the angle theta ₂ of the beam L ₂ when the beam L ₁ is emitted is the case within 90 degrees from the - [theta] _in2, so that the beam L ₂ is incident on the beam scanning unit 18, the liquid crystal panel 30 is controlled Is done.

That is, when the beam L ₁ is used, a 90-degree linearly polarized laser beam is transmitted through the liquid crystal plate 30 while maintaining the polarization state. In the polarization beam splitter 29, the laser beam of the linearly polarized light of 90 degrees is reflected, is separated as beam L _1. The beam L ₁ becomes circularly polarized state at wave plate 32a quarter. In this state, the beam L ₁ is projected by the reflecting mirror 18a through an adjusting mirror 26a, and is irradiated to the measurement object. The reflected beam coming from the object of measurement beam L ₁ is irradiated, maintaining the circular polarization state, when passing through the wave plate 32a quarter, out of phase by 45 degrees in the polarization state 0 ° linear polarization become. For this reason, the reflected beam incident on the polarization beam splitter 29 passes through the polarization beam splitter 29 and is received by the photodiode 15a.

Similarly, when the beam L ₂ is used, the liquid crystal plate 30 is controlled, and the 90-degree linearly polarized laser beam is changed to a 0-degree polarization state by the liquid crystal plate 30. In the polarization beam splitter 29, the laser beam of the 0-degree linearly polarized light is transmitted, is separated as beam L _2. The beam L ₂ becomes circularly polarized light in one wave plate 32b quarter. In this state, the beam L ₂ is projected by the reflecting mirror 18b via the adjustment mirror 26b, it is irradiated to the measurement object. The reflected beam coming from the measurement object irradiated with the beam L ₂ maintains a circular polarization state, and when passing through the quarter-wave plate 32b, the polarization state is shifted by 45 degrees and linearly polarized light of 90 degrees. become. For this reason, the reflected beam incident on the polarization beam splitter 29 is reflected by the polarization beam splitter 29 and received by the photodiode 15a.

  FIG. 12 is a diagram illustrating a flow of a distance measuring method in the distance measuring apparatus according to the third embodiment. Of the distance measurement method according to the third embodiment, steps S10 to S40, S70, S100, and S110 shown in FIG. 12 are the same as steps S10 to S40, S70, S100, and S110 shown in FIG. In the flow shown in FIG. 12, step S45 and step S75 are provided.

Step S45, the measurement angle θ1 of the beam _{L 1} when the emitted beam _{L 1} is performed when it is within 180 degrees + Shitain1 beyond 90 degrees (Yes in step S40). Specifically, a data processing / control unit (not shown) similar to the data processing / control unit 16 of the first embodiment applies a voltage to the liquid crystal plate 30 so that the 90-degree linearly polarized laser beam is maintained at 90 degrees. Is applied (step S45). In this state, a laser beam is emitted from the laser light source 12a (step S50), the polarization state beam L ₁ of tuned circularly polarized light is irradiated to the measurement object as shown in FIG. 11.
Step S75, the measurement angle θ2 of the reflection mirror L ₂ when the emitted beam L ₂ is performed when it is within 90 degrees from the - [theta] _in2 (Yes in step S70). Specifically, a data processing / control unit (not shown) similar to the data processing / control unit 16 of the first embodiment uses a liquid crystal so that the polarization state of a 90-degree linearly polarized laser beam becomes 0-degree linearly polarized light. A voltage is applied to the plate 30 (step S75). In this state, the laser beam of the linearly polarized light of 90 degrees is emitted from the laser light source 12a (step S50), the polarization state is adjusted beam L ₂ of the circularly polarized light is irradiated to the measurement object as shown in FIG. 11 .

The reflected beam that arrives as reflected light from the irradiated measurement object is transmitted or reflected through the polarization beam splitter 29 and received by the photodiode 15a (step S60).
In this way, the distance measuring device 10 intermittently irradiates the measurement object from the beam scanning unit 18 with the pulsed beams L ₁ and L ₂ and measures the distance of the measurement object.
Step S20~S100 in Figure 12, after the start of the driving of the motor, is continuously performed, the distance measurement is performed for each of the outgoing beam L ₁ and the beam L _2, the data of the distance information is output in real-time (Step S110).

Therefore, the distance measuring device 10 of the third embodiment has the same effect as the distance measuring device 10 of the first embodiment. Further, the distance measuring device 10 of the third embodiment reflects or transmits the laser beam at the polarization beam splitter 29 by adjusting the polarization state of the laser beam emitted from the laser light source 12 a using the liquid crystal plate 29. , Beams L ₁ and L ₂ are generated. The distance measuring device 10 of the third embodiment further adjusts the polarization state of the reflected beam using the quarter-wave plates 32a and 32b and reflects or transmits the reflected beam at the polarization beam splitter 30, thereby making the reflected beam a photodiode. Light is received at 15a. For this reason, the distance measuring apparatus 10 of 3rd Embodiment can complete | finish only one laser light source and a photodiode, and can provide the compact distance measuring apparatus 10. FIG. Further, as in the second embodiment, the reflected light is received as compared with the case where the half mirror 28 is used to irradiate a part of the laser beam to the measurement object and the half mirrors 14a and 14b are used to receive a part of the reflected beam. Since the light intensity of the beam does not decrease, the light intensity of the laser beam of the laser light source 12a can be suppressed in the third embodiment.

The said embodiment discloses the content shown below.
(Appendix 1)
A distance measuring device (10) for measuring a distance to a measurement object by irradiating the measurement object with a light beam,
A beam emitting unit for emitting a plurality of light beams having different directions to irradiate the measurement object;
A light receiving unit for receiving the reflected beam reflected from the measurement object and returned;
A data processing unit for obtaining distance information of a measurement object using a reflected beam received by the light receiving unit;
A beam scanning unit that scans each of the plurality of light beams emitted from the beam emitting unit,
The beam scanning unit includes one or a plurality of reflection mirrors, and a rotation driving unit that rotates the reflection mirror so as to have a rotation axis along a reflection surface of the reflection mirror, and the plurality of light beams Is incident on the position of the rotation axis on the reflection surface of the reflection mirror from different directions.

(Appendix 2)
The beam light scanning unit includes, as the reflection mirror, an array of mirrors arranged in multiple stages in the direction of the rotation axis and having different directions of reflection surfaces.
The distance measuring device according to appendix 1, wherein each of the array mirrors receives incidence of one of the plurality of light beams.

(Appendix 3)
The beam emitting unit intermittently emits any one of the plurality of light beams by switching on / off of each of the plurality of light beams according to the direction of the reflecting surface of the reflecting mirror. The distance measuring device according to appendix 1 or 2.

(Appendix 4)
4. The distance measuring device according to claim 1, wherein an optical path between the beam emitting unit and the beam scanning unit is formed on a plane orthogonal to the rotation axis.

(Appendix 5)
A scanning range by the plurality of light beams by the beam scanning unit is a range around the rotation axis centering on a first direction,
The beam emitting unit emits each of the plurality of light beams from the rear side with respect to the first direction toward the position of the rotation axis on the reflection surface of the reflection mirror. 5. The distance measuring device according to any one of 4 above.

(Appendix 6)
The beam emitting unit includes one beam light source and an optical system including a first optical element that separates the two light beams by reflection and transmission of one light beam emitted from the beam emitting unit. 6. The distance measuring device according to any one of 5 above.

(Appendix 7)
The light receiving unit is provided between the beam emitting unit and the beam scanning unit, and receives a second optical element that reflects a reflected beam from an object to be measured, and the reflected beam reflected by the second optical element. The distance measuring device according to any one of appendices 1 to 6, comprising a light receiving sensor.

(Appendix 8)
The beam emitting unit includes one beam light source, a polarization control element that controls a polarization state of one light beam emitted from the beam emitting unit, and a light beam whose polarization state is controlled, and the polarization state of the light beam. A third optical element that reflects or transmits the reflected light from the object to be measured and transmits or reflects the reflected beam from the measurement object according to the polarization state of the reflected beam,
A quarter wave plate is provided between the beam emitting unit and the beam scanning unit,
The light receiving unit includes a light receiving sensor that receives the reflected beam from the measurement object that has passed or reflected by the third optical element through the reflection mirror and the quarter-wave plate. The distance measuring device according to any one of claims.

(Appendix 9)
A distance measurement method for measuring a distance to a measurement object by irradiating the measurement object with a light beam,
Each of a plurality of light beams having different directions is emitted from the beam emitting unit,
Measuring by reflecting the plurality of light beams at a position of the rotation axis on a reflection surface of one or more reflection mirrors having a rotation axis along the reflection surface and rotating about the rotation axis. Irradiate the object with each of the light beams;
The reflected beam reflected and returned by the measurement object by irradiation of the light beam is reflected by the reflecting mirror and received.
A distance measurement method characterized in that distance information to a measurement object is obtained using the received reflected beam.

(Appendix 10)
When measuring the distance of the object to be measured, one of the plurality of light beams is intermittently switched by switching on and off the irradiation of the plurality of light beams in accordance with the direction of the reflecting surface of the reflecting mirror. The distance measuring method according to appendix 9, wherein the distance is emitted.

(Appendix 11)
Each of the array mirrors arranged in multiple stages in the direction of the rotation axis and having different reflecting surface directions receives one incidence of the plurality of light beams, whereby each of the array mirrors is used as the reflection mirror. The distance measuring method according to appendix 9.

(Appendix 12)
The scanning range of each of the plurality of light beams is a range around the rotation axis centering on a first direction;
Each of the plurality of light beams is emitted from a rear side with respect to the first direction toward the position of the rotation axis on the reflection surface of the reflection mirror, and any one of appendices 9 to 11 The distance measuring method according to item.

(Appendix 13)
The distance measuring method according to any one of appendices 9 to 12, wherein the plurality of light beams are formed by transmitting and reflecting one light beam using a first optical element.

(Appendix 14)
The reflected beam from the measurement object travels in the reverse direction of each of the plurality of light beams between the reflection mirror and the beam emitting unit, and uses the second optical element provided on the optical path. 14. The distance measuring method according to any one of appendices 9 to 13, wherein the reflected beam is received by a light receiving sensor at a position off the optical path by reflecting the reflected beam.

(Appendix 15)
Each of the plurality of light beams is controlled in polarization state by using a polarization control element, and further reflected or transmitted according to the polarization state by using a third optical element, so that different timings can be obtained from the beam emitting unit. At
Each of the polarized light beams is adjusted to a circularly polarized state using a quarter-wave plate and is incident on the reflection mirror.
The reflected beam from the measurement object is guided to the third optical element through the reflection mirror and the quarter-wave plate, and is reflected by the third optical element according to the polarization state of the reflected beam. Alternatively, the distance measuring method according to any one of appendices 9 to 12, wherein the distance is transmitted and received by a light receiving sensor.

  Although the distance measuring device and the distance measuring method of the present invention have been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course.

DESCRIPTION OF SYMBOLS 1 Passenger car 10,100 Distance measuring device 12 Beam emission part 12a, 12b, 102 Laser light source 13 Collimator lens 14,106 Light-receiving part 14a, 14b, 28 Half mirror 15a, 15b Photodiode 16 Data processing / control part 18 Beam scanning part 18a , 18b Reflective mirror 19 Rotating shaft 20 Rotating drive unit 21 Rotating body stage 22a, 22b Incident point 24 Transparent body 25a, 25b Shutter 26a, 26b Adjusting mirror 29 Polarizing beam splitter 30 Liquid crystal plate 32a, 32b Quarter wave plate 104 Measurement Object 108 Polygon mirror 110 Traveling vehicle

Claims (6)

A distance measuring device that irradiates a measurement object with a light beam and measures the distance to the measurement object,
A beam emitting unit for emitting a plurality of light beams having different directions to irradiate the measurement object;
A light receiving unit for receiving the reflected beam reflected from the measurement object and returned;
A data processing unit for obtaining distance information of a measurement object using a reflected beam received by the light receiving unit;
A beam scanning unit that scans each of the plurality of light beams emitted from the beam emitting unit,
The beam scanning unit includes a plurality of reflection mirrors, and a rotation driving unit that rotates the reflection mirror so as to have a rotation axis along a reflection surface of the reflection mirror, and the plurality of light beams reflect the reflection light. Incident from different directions to the position of the rotation axis on the reflecting surface of the mirror ,
The reflecting mirrors are arrayed mirrors arranged in multiple stages in the direction of the rotation axis, and the directions of the reflecting surfaces are different from each other, and each of the arraying mirrors receives incident one of the plurality of light beams. A distance measuring device characterized by receiving . The beam emitting unit intermittently emits any one of the plurality of light beams by switching on / off of each of the plurality of light beams according to the direction of the reflecting surface of the reflecting mirror. The distance measuring device according to claim 1 . The optical path between the beam emitting portion and the beam scanning unit is formed on a plane perpendicular to the rotation axis, the distance measuring apparatus according to claim 1 or 2. A scanning range by the plurality of light beams by the beam scanning unit is a range around the rotation axis centering on a first direction,
The beam emitting unit emits each of the plurality of light beams from a rear side with respect to the first direction toward a position of the rotation axis on a reflection surface of the reflection mirror. The distance measuring device according to any one of to 3 . A distance measurement method for measuring a distance to a measurement object by irradiating the measurement object with a light beam,
Each of a plurality of light beams having different directions is emitted from the beam emitting unit,
By reflecting the plurality of light beams at the position of the rotation axis on the reflection surface of the plurality of reflection mirrors having a rotation axis along the reflection surface and rotating about the rotation axis, Irradiating each of the light beams;
The reflected beam reflected and returned by the measurement object by irradiation of the light beam is reflected by the reflecting mirror and received.
Using the received reflected beam, obtain distance information to the measurement object ,
Each of the array mirrors arranged in multiple stages in the direction of the rotation axis and having different reflecting surface directions receives one incidence of the plurality of light beams, whereby each of the array mirrors is used as the reflection mirror. A distance measuring method characterized by that. When measuring the distance of the object to be measured, one of the plurality of light beams is intermittently switched by switching on and off the irradiation of the plurality of light beams in accordance with the direction of the reflecting surface of the reflecting mirror. The distance measuring method according to claim 5 , wherein the distance is emitted.