WO2019031403A1

WO2019031403A1 - Optical device

Info

Publication number: WO2019031403A1
Application number: PCT/JP2018/029201
Authority: WO
Inventors: 亮出田; 柳澤　琢麿; 孝典落合; 佐藤　充; 小笠原　昌和
Original assignee: パイオニア株式会社
Priority date: 2017-08-10
Filing date: 2018-08-03
Publication date: 2019-02-14

Abstract

Provided is an optical device that can adapt to changes in the external environment. An optical device (1) comprises: a MEMS mirror (5) which radiates laser light emitted from a wavelength tunable light source (2) toward a prescribed region; and a line sensor (9) which receives light including reflected light comprising the laser light that has been reflected from a target object (100) present in the prescribed region, and ambient light from a region including the target object (100). In addition, the optical device (1) includes a control unit (10) which controls the wavelength or light intensity of the laser light emitted from the wavelength tunable light source (2), on the basis of ambient light information, which relates to the wavelength of the ambient light when the wavelength tunable light source (2) is not radiating the laser light.

Description

Optical device

The present invention relates to an optical device that receives reflected light obtained by reflecting emitted light from an object.

2. Description of the Related Art Conventionally, there has been put into practical use an apparatus that irradiates light onto an object and measures the distance to the object based on the round-trip time until the reflected light returns.

In this type of device, in order to separate reflected light used for this distance measurement from ambient light such as sunlight, a band pass filter is used that transmits only light of the wavelength of the irradiated light. The N ratio is improved (see, for example, Patent Document 1).

JP 2007-85832 A

In the invention described in Patent Document 1, although the band pass filter is used to cope with the wavelength fluctuation due to the temperature fluctuation of the light emitting element, it is to cope with the wavelength fluctuation of the light emitting element which it has. Therefore, when ambient light changes due to time zone, weather, etc., when the distribution or intensity of the wavelength of environmental light changes and the intensity of the same wavelength as the wavelength of the light emitting element increases, the reflected light of the light emitted by the light emitting element It may not be detected.

Further, when the optical radar device according to the invention described in Patent Document 1 is mounted on a moving body, light emitted from an optical radar device mounted on another moving body or reflected light obtained by reflecting the light on the object It is assumed that etc. will be incident. In this case, if the wavelengths of the light emitted from the device itself and the light emitted from the other device are the same, the reflected light of the light emitted from the device itself can not be distinguished from the light emitted from the other device or the reflected light thereof. possible.

As described above, in the invention described in Patent Document 1, there have been cases in which it has become difficult to cope with changes in the external environment.

One of the problems to be solved by the present invention is to cope with changes in the external environment as described above.

The invention according to claim 1 made for the purpose of solving the above-mentioned problems is characterized in that irradiation means for irradiating the emitted light emitted from the emitting portion toward a predetermined range, and the emitted light exists in the predetermined range The light emitting unit emits light from the light emitting unit based on a light receiving unit that receives light reflected by an object and light including environmental light from a region including the object, and environmental light information that is information on the wavelength of the environmental light And controlling means for controlling the wavelength or the light amount of the emitted light.

It is a schematic block diagram of the optical apparatus concerning the 1st Example of this invention. It is explanatory drawing which showed operation | movement of the light projection system of the optical apparatus shown by FIG. It is explanatory drawing which showed operation | movement of the light reception system of the optical apparatus shown by FIG. It is explanatory drawing which showed the effect | action of the diffraction grating at the time of single wavelength incidence. It is explanatory drawing which showed the effect | action of the diffraction grating at the time of multi-wavelength incidence. It is explanatory drawing which showed the basic operation | movement of an ambient light information acquisition part. It is explanatory drawing which showed the operation | movement before the wavelength change of an ambient light information acquisition part. It is explanatory drawing which showed the operation | movement after the wavelength change of an ambient light information acquisition part. It is the graph which showed the spectrum of sunlight, and a wavelength change. It is explanatory drawing which showed the operation | movement before the wavelength change of the environmental light information acquisition part in case other signals exist. It is explanatory drawing which showed the operation | movement after the wavelength change of the environmental light information acquisition part in case other signals exist.

Hereinafter, an optical device according to an embodiment of the present invention will be described. An optical device according to an embodiment of the present invention comprises: an irradiation unit that irradiates the emitted light emitted from the emitting portion toward a predetermined range; and the reflected light reflected by the object whose emitted light is present in the predetermined range And a light receiving unit that receives light including ambient light from a region including the target. Furthermore, it has a control means for controlling the wavelength or the light quantity of the emitted light emitted from the emitting unit based on the ambient light information which is the information on the wavelength of the ambient light. By doing this, ambient light information on the wavelength of ambient light can be obtained. Therefore, based on the information, it is possible to make the emitted light of the wavelength where the intensity of the environmental light is small. Therefore, the emitted light can be irradiated corresponding to the change of the external environment.

Further, the ambient light information may be information on the wavelength of the ambient light received by the light receiving unit when the emitting unit is not emitting the emitted light. By doing this, it is possible to obtain only information on the wavelength of ambient light.

Moreover, you may use the sunlight spectrum information according to the season / weather / time zone as environmental light information. By doing this, the wavelength of the outgoing light can be selected based on the appropriate sunlight spectrum information.

In addition, the control means may change the wavelength of the ambient light to a wavelength smaller than the wavelength currently emitted by the emitting unit. By doing this, the S / N can be improved because the intensity of ambient light is reduced compared to the present.

Further, the light receiving unit may have a plurality of light receiving elements and an optical element for guiding the light to any of the plurality of light receiving elements according to the wavelength of the incident light. By doing this, it is possible to easily acquire wavelength information of ambient light that has entered from the signals received by the plurality of light receiving elements.

An optical apparatus according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the optical device 1 according to the present embodiment includes the variable wavelength light source 2, the collimator lens 3, the beam splitter 4, the MEMS mirror 5, the light emitting and receiving lens 6, and the diffraction grating 7. A condenser lens 8, a line sensor 9, and a control unit 10 are provided.

The variable-wavelength light source 2 as the emission unit is configured of a variable-wavelength light source capable of changing the emitted laser light to a wavelength in a predetermined wavelength range. As the wavelength variable light source 2, one using a well-known Littrow external resonator or Littman external resonator may be mentioned, but other methods may be used without particular limitation. The wavelength variable light source 2 intermittently emits (irradiates) laser light as pulse light.

The collimator lens 3 converts the laser light emitted from the variable wavelength light source 2 into a parallel light flux. The beam splitter 4 outputs the laser light collimated by the collimator lens 3 to the MEMS mirror 5 and reflects reflected light and environmental light, which will be described later, reflected by the MEMS mirror 5 toward the diffraction grating 7.

The MEMS mirror 5 as an irradiation means scans the laser light transmitted through the beam splitter 4 in the horizontal direction and the vertical direction in the region where the object 100 is present. Further, the MEMS mirror 5 reflects, to the beam splitter 4, the incident light that the laser light or the like reflected by the object 100 has entered the light emitting and receiving lens 6. The MEMS mirror 5 is a mirror configured by MEMS (Micro Electro Mechanical Systems), and is driven by an actuator (not shown) integrally formed with the mirror. Also, the MEMS mirror 5 may be another beam deflection means such as a galvano mirror or a polygon mirror.

The light emitting and receiving lens 6 irradiates (projects) the laser light reflected by the MEMS mirror 5 to the area where the object 100 exists. Further, reflected light of laser light from the object 100 and environmental light such as sunlight (including light which is reflected by the object 100) enter the light emitting and receiving lens 6 as incident light (received). Further, in this embodiment, it is assumed that laser light emitted from another optical device as ambient light and reflected light of the laser light reflected by the object are also included.

The diffraction grating 7 as an optical element diffracts the incident light from the beam splitter 4 to the line sensor 9 at a diffraction angle corresponding to the wavelength component of the incident light. In the present embodiment, although a transmission-type diffraction grating will be described, it may be a reflection-type diffraction grating.

The condenser lens 8 is provided between the diffraction grating 7 and the line sensor 9 and condenses the incident light diffracted by the diffraction grating 7 onto the line sensor 9.

The line sensor 9 is a light receiving sensor in which a plurality of light receiving elements are formed in a line along a direction in which light incident on the diffraction grating 7 is diffracted. Each of the plurality of light receiving elements receives light of the incident light diffracted by the diffraction grating 7 according to the wavelength component. Each light receiving element of the line sensor 9 outputs a signal corresponding to the intensity (received light intensity) of the received light to the control unit 10. Further, the line sensor 9 can be configured by, for example, an avalanche photodiode (APD) as a light receiving element.

The control unit 10 as a control means detects the reflected light of the laser light emitted from the variable wavelength light source 2 based on the signal indicating the light reception intensity of each light receiving element of the line sensor 9. Further, when the variable wavelength light source 2 does not emit the laser light, the control unit 10 emits the laser from the variable wavelength light source 2 based on the result of the line sensor 9 receiving the environmental light incident from the light receiving and receiving lens 6. Determine the wavelength of light.

Next, the operation of the optical device 1 configured as described above will be described with reference to FIGS. 2 and 3. FIG. 2 is an explanatory view of the operation at the time of emission (light emitting system).

First, laser light emitted in a pulse form from the variable wavelength light source 2 is collimated by the collimator lens 3, and then passes through the beam splitter 4 and enters the MEMS mirror 5. Then, the laser beam reflected by the MEMS mirror 5 is irradiated toward the outside of the optical device 1 by the light emitting and receiving lens 6. At this time, by changing the angle of the MEMS mirror 5 at each irradiation timing, it is possible to temporally change the position of the beam spot to be irradiated toward the region where the object 100 exists, in the horizontal direction and A vertical scan is performed.

FIG. 3 shows the operation at the time of incidence (light receiving system). The laser light reflected (scattered) by the object 100 follows the light path opposite to that at the time of light projection through the light receiving and receiving lens 6, is reflected by the MEMS mirror 5, and is reflected by the beam splitter 4. It is incident on. The diffraction angle of the diffraction grating 7 is determined according to the groove pitch and the wavelength of the incident light. In this embodiment, a laser beam is used, and the wavelength of the light incident on the diffraction grating 7 is single. Therefore, after being diffracted in a predetermined direction determined by the wavelength of the laser beam, the line sensor is conducted by the condensing lens 8 The light is collected on a predetermined light receiving element on the reference numeral 9.

The above-described diffraction grating 7, condenser lens 8, and line sensor 9 constitute an ambient light information acquiring unit 20 as a light receiving unit. The ambient light information acquisition unit 20 is configured of the diffraction grating 7, the condenser lens 8, and the line sensor 9. However, for example, a spectroscope using a prism or the like is not limited. In other words, any other configuration may be used as long as it can acquire information on the wavelength of ambient light. Alternatively, the configuration may be such that the spectrum of sunlight according to the season, the weather, or the difference in time is held in advance as a table, and is used as ambient light information. That is, the light receiving unit may have a function of acquiring wavelength information of ambient light separately. In this case, the table is stored in storage means (not shown), and a table according to the season, weather, and time when using the optical device 1 is used. By doing so, the wavelength of the laser light can be selected based on appropriate sunlight spectrum information.

In the optical device 1 configured as described above, the light incident on the light emitting and receiving lens 6 is not only the reflected light of the laser light emitted from the wavelength variable light source 2. Any light that illuminates the object 100 such as sunlight or light on the street, or light that is reflected by the object 100 enters the light emitting / receiving lens 6 and enters the diffraction grating 7 via the MEMS mirror 5 . Ambient light such as sunlight is light including various wavelengths, and is diffracted in various directions by the diffraction grating 7 and is incident on a plurality of light receiving elements on the line sensor 9 according to the included wavelength range. Since light of various wavelengths is incident on the light emitting and receiving lens 6, light of high luminance (high intensity) having the same wavelength as the laser light emitted by itself may be incident depending on the situation. In this case, the reflected light of the laser light can not be detected. Therefore, by setting the wavelength of the laser beam emitted by itself to a wavelength range in which the influence of environmental light is reduced, the influence of environmental light can be suppressed (details will be described later).

The operation of the diffraction grating 7 (the ambient light information acquiring unit 20) will be described in detail with reference to FIGS. 4 to 6. The diffraction angle θ ₂ when monochromatic light of wavelength λ ₀ is made incident on the diffraction grating 7 with a groove spacing p from the direction of the angle θ ₁ is expressed by the following equation (1).

As shown in FIG. 4, the diffraction grating 7 diffracts only a specific direction theta ₂ in a situation for entering the monochromatic light (laser beam). In the following, diffracted light means + 1st order diffracted light unless otherwise specified. Further, in the present embodiment, a blazed diffraction grating having a sawtooth-like groove shape is used as the diffraction grating. The use of a blazed diffraction grating is desirable because the diffraction efficiency of + 1st order light can be theoretically made 100% by the blazed diffraction grating. On the other hand, as shown in FIG. 5, when light having a wavelength range of λ ₁ to λ ₂ is made incident on the same diffraction grating 7, light is diffracted in different directions for each wavelength component. That is, reflected light of laser light and environmental light are incident as incident light to the diffraction grating 7 (optical element), and the incident light is guided to one of the plurality of light receiving elements according to the wavelength. .

Next, the action of the condenser lens 8 will be described. Since even a laser beam is actually a beam having a predetermined width, in this embodiment, a condenser lens 8 is provided to condense the diffracted light diffracted by the diffraction grating 7 on the line sensor 9. Assuming that the focal length of the focusing lens 8 is f, the distance from the diffraction grating 7 to the focusing lens 8 and the distance from the focusing lens 8 to the line sensor 9 are both located at the focal length f (see FIG. 6 and FIG. 7), the diffracted light diffracted in the direction in which the line sensors 9 are aligned at a predetermined diffraction angle is collected at one point on the line sensor 9. When the incident light is monochromatic light (laser light), it is incident only on a specific light receiving element on the line sensor 9, and in the case of incident light having a certain wavelength range, it is incident on a plurality of light receiving elements. That is, of the diffracted light, the reflected light of the laser light emitted from the wavelength variable light source 2 is incident only on a specific light receiving element on the line sensor 9, and the environmental light is a plurality of light receiving elements corresponding to the included wavelength components. It will be incident.

The focal length f may be set to have appropriate wavelength resolution in accordance with the size of the line sensor 9 to be used and the number of light receiving elements.

In ambient light information acquisition unit 20 having such a configuration, when the wavelength of the laser light emitted from the wavelength variable light source 2 is lambda _0, a wavelength longer than lambda ₀ in addition to the reflected light having a wavelength of lambda ₀ lambda Suppose that light of ₀ 'enters. In this case, the diffraction angle of the incident light of wavelength λ ₀ is θ ₂ , the diffraction angle of the incident light of wavelength λ ₀ ′ is θ ₂ ′, and the light receiving position on the line sensor 9 as shown by the solid line and broken line in FIG. Changes. Therefore, by measuring and grasping the relationship between the light receiving position and the wavelength in advance, it is possible to distinguish between the reflected light of the laser beam emitted by itself and the environmental light.

The environmental light information acquisition unit 20 acquires wavelength information of environmental light when the variable wavelength light source 2 does not emit laser light at the time of initial startup or the like. As a result of acquisition, for example, as shown in the graph of FIG. 7, the same position on the line sensor 9 when the peak wavelength of the ambient light (dotted line) and the wavelength of the own signal (solid line) are the same or very close. Therefore, the S / N is deteriorated, and the reflected light of the laser light can not be detected.

Therefore, as shown in the graph of FIG. 8, the control unit 10 changes the wavelength of the laser light emitted by itself to λ ₃ based on the acquired wavelength information. By doing this, the S / N can be improved because signals are received at different positions on the line sensor 9. That is, the control unit 10 uses wavelength information related to the wavelength of the environmental light received by the line sensor 9 (light receiving unit) of the environmental light information acquiring unit 20 when the variable wavelength light source 2 (emitting unit) does not irradiate the emitted light. Based on this, the wavelength of the outgoing light emitted from the variable wavelength light source 2 (emitting part) is changed.

The above description will be described based on the sunlight spectrum shown in FIG. 9 changes, if the laser beam emitted in the initial wavelength variable light source 2 was lambda ₀ (about 1000 .mu.m), the intensity of the sunlight is small lambda ₃ based on the reception result of the line sensor 9 (approximately 930μm) Do. That is, the control unit 10 changes the wavelength of the ambient light to a wavelength smaller than the wavelength currently emitted by the variable wavelength light source 2 (emission unit).

According to the present embodiment, the optical device 1 is reflected by the MEMS mirror 5 that irradiates the laser light emitted from the wavelength variable light source 2 toward the predetermined range, and the object 100 in which the laser light is present in the predetermined range And a line sensor 9 for receiving light including ambient light from a region including the object 100. Furthermore, when the variable wavelength light source 2 does not irradiate the laser light, the control unit 10 controls the wavelength or the light quantity of the laser light emitted from the variable wavelength light source 2 based on the environmental light information which is information on the wavelength of the environmental light. Have. By doing this, it is possible to obtain environmental light information when not irradiating itself, and based on the information, it is possible to obtain laser light of a wavelength having a small intensity of environmental light. Therefore, laser light can be emitted in response to changes in the external environment.

Further, the control unit 10 changes the wavelength of the environmental light to a wavelength smaller than the wavelength currently irradiated by the variable wavelength light source 2. By doing this, the S / N can be improved because the intensity of ambient light is reduced compared to the present.

In addition, the ambient light information acquisition unit 20 includes a line sensor 9 having a plurality of light receiving elements, and a diffraction grating 7 for guiding the light to any of the plurality of light receiving elements according to the wavelength of the incident light. ,have. By doing this, it is possible to easily acquire wavelength information of ambient light that has entered from the signals received by the plurality of light receiving elements.

Further, the present optical device can use the distance to the object for measurement. That is, the CPU or the like of the distance measuring device on which the optical device is mounted measures the time from when the light source emits laser light to when it is received by the light receiving element as reflected light reflected by the object 100. The distance from the device to the object can be measured.

In the above-described embodiment, the ambient light is mainly described as light for illuminating the object 100 such as sunlight or street light, but when the optical device 1 is mounted on a movable body such as a vehicle, it is other than the own vehicle The laser beam emitted from the optical device 1 mounted on another vehicle or the reflected light may be incident. Then, if the wavelength of the laser beam emitted by itself and the wavelength of the laser beam emitted by the other optical device are the same, the reflected light of the laser beam emitted by itself and the laser beam emitted by the other optical device or its reflected light May not be distinguishable and may malfunction. Therefore, laser light and reflected light from such other optical devices are regarded as environmental light, and the above-mentioned embodiment is applied to change its wavelength to a wavelength different from that of the other optical devices 1 and cause malfunction. Can be prevented.

10 and 11 show an example where laser light from another optical device and its reflected light are incident. The solid line in FIG. 10 indicates the reflected light of the laser beam emitted by itself, and the broken line indicates the ambient light. In the graph of FIG. 10, although there are two peaks of broken lines, the peaks overlapping with the solid line indicate the wavelengths of the laser light from the other optical device and the reflected light thereof. In this case, the wavelength (λ ₃ ) of the laser beam emitted by itself overlaps with the wavelength of the laser beam emitted by another optical device. That is, the same light receiving element of the line sensor 9 receives the reflected light.

Therefore, as shown in FIG. 11, based on the acquired wavelength information of ambient light when the variable wavelength light source 2 is not irradiated with laser light, the control unit 10 of the other wavelengths of the variable wavelength light source 2 from lambda ₃ optical wavelength and the peak of such wavelength and solar laser beam of the device is changed to not lambda ₄ which overlap. By doing this, the light receiving element different from the line sensor 9 receives the own signal and the other signal, which makes it possible to prevent a malfunction.

In the embodiment, an example of acquiring wavelength information of ambient light at the first activation is shown, but for example, in a cycle of scanning a predetermined area by the MEMS mirror 5, a cycle not to irradiate the laser light is provided The wavelength information of the ambient light may be acquired at the time.

In the embodiment, the wavelength of the emitted light emitted by the variable-wavelength light source 2 (the output unit) is changed based on the wavelength information on the wavelength of the environmental light, but the light amount of the emitted light to be emitted is adjusted ) To make it easy to distinguish between the ambient light and the reflected light of the laser light.

Further, the present invention is not limited to the above embodiment. That is, those skilled in the art can carry out various modifications without departing from the gist of the present invention in accordance with conventionally known findings. As long as the configuration of the optical device of the present invention is provided even by such a modification, it is of course included in the scope of the present invention.

1 Optical device 2 Tunable light source (emitting part)
5 MEMS mirror (irradiation means)
7 Diffraction grating (light receiving part)
8 Condenser Lens (Receiver)
9 Line sensor (light receiving unit)
10 Control unit (control means)
100 objects

Claims

An irradiation unit that irradiates the emitted light emitted from the emission unit toward a predetermined range;
A light receiving unit that receives light reflected by the target whose emission light is present in the predetermined range and ambient light from a region including the target;
A control unit configured to control the wavelength or the light quantity of the emitted light emitted from the emission unit based on the ambient light information which is information on the wavelength of the ambient light;
An optical device comprising:
The optical device according to claim 1, wherein the ambient light information is information on a wavelength of the ambient light received by the light receiving unit when the emitting unit is not emitting the emitted light.
The optical device according to claim 1, wherein sunlight spectrum information according to at least one of a season / weather / time zone is used as the ambient light information.
The optical device according to claim 1, wherein the ambient light information is information on a spectrum of ambient light.
The optical device according to any one of claims 1 to 4, wherein the control unit changes the wavelength of the ambient light to a wavelength smaller than the wavelength currently emitted by the emitting unit.
The light receiving unit is
A plurality of light receiving elements,
An optical element for guiding the light to one of the plurality of light receiving elements according to the wavelength of the incident light;
The optical device according to any one of claims 1 to 5, characterized in that