DE102020211468A1 - LIDAR device and LIDAR system - Google Patents

Abstract

The invention relates to a LIDAR device for scanning a scanning area. The LIDAR device has a first radiation source for generating electromagnetic radiation and a first detector for receiving radiation backscattered and/or reflected from the scanning area. The scanning area has a first direction of extension and a second direction of extension, the first radiation source having different emission directions in the first direction of extension and the different emission directions can be set by changing a parameter by means of an interference effect. The LIDAR device also has a controller, the controller being set up to change the parameter, the parameter being changed in such a way that the electromagnetic radiation generated is emitted in each emission direction for a predetermined period of time.

Description

The invention relates to a LIDAR device and a LIDAR system.

State of the art

LIDAR devices are known from the prior art, in which electromagnetic radiation is emitted into a scanning area and distances to objects can be detected using backscattered and/or reflected radiation. In this case, transit time measurements can generally be used, in which case a pulse is then transmitted and the transit time up to the arrival of a backscattered and/or reflected pulse is used to determine the distance. With so-called FMCW LIDAR, continuous, frequency-modulated radiation is emitted instead and a distance is determined by superimposing the currently emitted radiation and the backscattered and/or reflected radiation, analogous to FMCW radar. In order to cover the entire deflection range, the emitted radiation is sent out in different directions, with either mechanically movable mirrors (including micromechanical mirrors) being used or interference effects, for example on gratings, being used for the deflection. The movement of the beams is continuous. Due to the continuous change in the direction of radiation, it is necessary, especially with FMCW LIDAR, but also with runtime measurements, not to change the direction of radiation too quickly in order to achieve reliable distance measurements, especially when used in vehicles, for example for driver assistance systems or for autonomous driving.

Disclosure of Invention

One object of the invention is to provide a LIDAR device and a LIDAR system in which the emitted radiation is emitted in one emission direction for a predetermined measurement time and only then is a further emission direction selected.

These objects are solved with the subject matter of the independent patent claim. Advantageous developments are specified in the dependent patent claims.

A LIDAR device for scanning a scanning area has a first radiation source for generating electromagnetic radiation and a first detector for receiving radiation backscattered and/or reflected from the scanning area. The scanning area has a first direction of extension and a second direction of extension, the first radiation source having different emission directions in the first direction of extension and the different emission directions can be set by changing a parameter by means of an interference effect. The LIDAR device also has a controller, the controller being set up to change the parameter, the parameter being changed in such a way that the electromagnetic radiation generated is emitted in each emission direction for a predetermined period of time.

The LIDAR device can determine distances by measuring the transit time or by superimposing the currently emitted radiation and the backscattered and/or reflected radiation (FMCW). It can be provided that the interference effect is used in such a way that the effective refractive index of a grating is changed, for example by changing the polarization direction of a liquid crystal. Alternatively, the first radiation source can be designed as an optical phase array and the direction of emission can be adjusted by means of a phase shift.

The specified period of time can in particular be selected in such a way that an envisaged range, the speed of light and a specified integration time are taken into account. After that, the direction of emission can be changed.

In one embodiment of the LIDAR device, the parameter is changed in such a way that the emission direction over time corresponds to a step function. In particular, this can be achieved by changing the parameter in steps. For example, the effective refractive index of a grating filled with liquid crystal could also be increased following a step function in order to achieve different emission directions.

In one embodiment of the LIDAR device, the first radiation source comprises a tunable laser and a first Bragg grating, the electromagnetic radiation generated being emitted by the first Bragg grating for different wavelengths in different emission directions. The tunable laser can be operated in such a way that the wavelength of the laser is changed after the predetermined period of time has elapsed, thereby adjusting the direction of emission. The wavelength can also follow a step function. This enables a simple and inexpensive construction of the LIDAR device.

In one embodiment of the LIDAR device, the tunable laser has a resonator, with the resonator being formed from two resonator gratings, with a grating constant of the resonator gratings differing. Due to the different grating constants of the resonator gratings, discrete wavelengths of the tunable laser can be set as the resonance wavelength.

In one embodiment of the LIDAR device, this also has a second radiation source, the second radiation source also comprising a tunable laser and the first radiation source and the second radiation source each covering a partial area of the emission area with regard to the first direction of extent. Furthermore, more than two radiation sources can also be provided, each of which includes a tunable laser. Provision can also be made for each radiation source to have its own Bragg grating. The first Bragg grating is assigned to the first radiation source, and a second Bragg grating can be assigned to the second radiation source. This enables increased measurement accuracy in the first direction of extent, since measurements can be carried out in parallel using a plurality of radiation sources.

In one embodiment of the LIDAR device, the electromagnetic radiation generated by the first radiation source and the second radiation source is emitted in different directions by means of the first Bragg grating. This enables a particularly simple structure since only the first Bragg grating is necessary.

In the embodiments with a tunable laser, it can be provided that an optical waveguide is arranged between the radiation source or sources and the Bragg grating or Bragg gratings and the emitted radiation is coupled out of the optical waveguide by means of the Bragg grating.

It can be provided that a deflection in the second direction of extent also takes place by means of an interference effect analogous to the methods described.

In one embodiment of the LIDAR device, the generated electromagnetic radiation is deflected in the second direction of extent by means of a movable mirror. This enables a simple construction of the LIDAR device and represents a good compromise between measurement accuracy and effort.

In one embodiment of the LIDAR device, the change in the direction of emission in the first direction of extent occurs quickly compared to the change in the direction of emission in the second direction of extent.

In one embodiment of the LIDAR device, a first angular range of between 20 and 30 degrees is covered in the first direction of extent, with more than one hundred and fifty different emission directions being able to be set in the first direction of extent.

The invention also includes a LIDAR system consisting of several LIDAR devices according to the invention. It can be provided in particular that each of the LIDAR devices covers a partial area of the emission area with regard to the second direction of extension. Provision can be made for a second angular range of between 120 and 180 degrees, in particular 150 degrees, to be covered in the second direction of extent and for three LIDAR devices, each covering 40 to 60 degrees, in particular 50 degrees, to be used.

• 1 eine schematische Ansicht einer LIDAR-Vorrichtung;
• 2 eine weitere schematische Ansicht der LIDAR-Vorrichtung;
• 3 eine Stufenfunktion einer Abstrahlrichtung;
• 4 eine Strahlenquelle mit durchstimmbarem Laser und Bragg-Gitter;
• 5 einen Laserresonator mit zwei Resonatorgittern;
• 6 eine schematische Ansicht einer weiteren LIDAR-Vorrichtung;
• Fig. '7 eine weitere schematische Ansicht der weiteren LIDAR-Vorrichtung;
• 8 ein LIDAR-System;
• 9 eine Ablenkung in einer ersten Erstreckungsrichtung für das LIDAR-System;
• 10 eine Ablenkung in einer zweiten Erstreckungsrichtung für das LIDAR-System; und
• 11 eine Strahldrift des LIDAR-Systems.

Exemplary embodiments of the invention are explained with reference to the following drawings. In the schematic drawing show:

• 1 a schematic view of a LIDAR device;
• 2 another schematic view of the LIDAR device;
• 3 a step function of a radiation direction;
• 4 a radiation source with tunable laser and Bragg grating;
• 5 a laser resonator with two resonator gratings;
• 6 a schematic view of another LIDAR device;
• 7 shows a further schematic view of the further LIDAR device;
• 8th a LIDAR system;
• 9 a deflection in a first span direction for the LIDAR system;
• 10 a deflection in a second span direction for the LIDAR system; and
• 11 a beam drift of the LIDAR system.

1 shows a LIDAR device 1 for scanning a scanning area 2, having a first radiation source 11 for generating electromagnetic radiation 17 and a first detector 14 for receiving radiation 18 backscattered and/or reflected from the scanning area 2. The scanning area 2 has a first direction of extent 3 (upward in the image plane) and a second direction of extent 4 (perpendicular to the image plane), the first radiation source 11 in the first Extension direction 3 has different emission directions 5 . The different emission directions 5 can be adjusted by changing a parameter by means of an interference effect. This is in the embodiment of 1 achieved by means of a beam deflector 20, wherein a controller 6 assigned to the LIDAR device 1 is set up to change the parameter by changing a parameter of the beam deflector 20. The parameter is changed in such a way that the generated electromagnetic radiation 17 is emitted in each emission direction 5 for a predetermined period of time.

The beam deflector 20 can, for example, comprise an optical grating, in which case the effective refractive index of the grating can be changed, for example by embedded liquid crystal material, using a signal output by the control unit 6 . It can thereby be achieved that the generated electromagnetic radiation 17 is emitted in the different emission directions 5 .

also in 1 it is shown that the beam deflector 20 can optionally be rotated about an axis of rotation 21 and thus a deflection of the generated electromagnetic radiation 17 in the second direction of extension 4 can be achieved.

2 FIG. 1 shows a plan view of essentially the LIDAR device 1 of FIG 1 corresponding LIDAR device 1. The beam deflector 20 is non-rotatable. Furthermore, in 2 the first direction of extension 3 perpendicular to the image plane, so that the electromagnetic radiation 17 emitted in the different emission directions 5 is generated in the projection of the 2 each one above the other and is therefore indistinguishable. A movable mirror 30, designed here as a facet wheel 31 with six facets and a diameter in the centimeter range, is used to deflect the generated electromagnetic radiation 17 in the second direction of extension 4, with a different number of facets or an alternative mechanically movable mirror being able to be provided.

The LIDAR device 1 of 1 and 2 can determine distances by measuring the transit time or by superimposing the currently generated electromagnetic radiation 17 and the backscattered and/or reflected radiation 18 (FMCW). Alternatively, the first radiation source 11 can be designed as an optical phase array and the direction of emission can be adjusted by means of a phase shift. The specified period of time can in particular be selected in such a way that an envisaged range, the speed of light and a specified integration time are taken into account. After that, the emission direction 5 can be changed.

The LIDAR device 1 of 1 and 2 is designed in such a way that the backscattered and/or reflected radiation 18 within the LIDAR device 1 has the same beam path as the generated electromagnetic radiation 17 and the first detector 14 is arranged spatially close to the first radiation source 11 . As a result, the backscattered and/or reflected radiation 18 can also be deflected in the direction of the first detector 14 by means of the beam deflector 20 .

3 shows a diagram 100 in which a radiation angle 102 is plotted over a time axis 101 . The radiation angle 102 is set in the form of a step function, which can be done by the beam deflector 20 remaining unchanged for the predetermined period of time and then a parameter of the beam deflector 20 being changed. The width of the in 3 The stages shown then corresponds to the predetermined period of time in which the generated electromagnetic radiation 17 is radiated in the individual emission directions 5.

4 1 shows a first radiation source 11 that can be used in the LIDAR devices 1 already described and replaces the first radiation source 11 and the beam deflector 20 described there. The first radiation source 11 consists here of a tunable laser 41 connected to the controller 6, a light guide 42 and a first Bragg grating 43. If a wavelength of the generated electromagnetic radiation 17 is changed, as is possible with the tunable laser 41, then it changes the Bragg relationship of the first Bragg grating 11 and the generated electromagnetic radiation 17 is radiated in the different emission directions 5. A first light source 11 can thus be used, which already emits in the different emission directions 5 and the LIDAR device 1 can therefore be configured more simply. The light guide 42 is not absolutely necessary, provided that the first radiation source 11 has a corresponding geometry.

In contrast to the representation of 4 the light guide 42 can also be omitted and the electromagnetic radiation generated by the first radiation source 11 impinge directly on the first Bragg grating 41, for example at a predetermined angle.

5 shows a tunable laser 41 in which a resonator 46 is formed from a first resonator grating 47 and a second resonator grating 48 . A lattice constant of the first Resonator grating 47 differs from a grating constant of the second resonator grating 48. Due to the different grating constants of the resonator gratings 47, 48, discrete wavelengths of the tunable laser 41 can be set as the resonance wavelength.

6 shows a LIDAR device 1, which essentially corresponds to the already described LIDAR devices 1 of FIG 1 and 2 provided that no differences are described below. A first radiation source 11 and a second radiation source 12 emit generated electromagnetic radiation 17 in the direction of the beam deflector 20. The overall system made up of the radiation sources 11, 12 and the beam deflector 20 is designed in such a way that the electromagnetic radiation 17 generated, starting from the first radiation source 11, a first sub-area 7 and the electromagnetic radiation 17 generated is deflected from the second radiation source 12 into a second sub-area 8 of the scanning area 2, with several emission directions 5 being provided for each sub-area 7, 8 analogously to the methods described above.

For clarity in 6 To increase, the backscattered and / or reflected radiation (BZ 18 in the previous figures) is not shown here, but can be analogous. Furthermore, a second detector 15 is arranged, radiation backscattered and/or reflected from the first partial area 7 being able to be detected by the first detector 14 and radiation backscattered and/or reflected from the second partial area 8 being able to be detected by the second detector 15 .

In general, the number of radiation sources can be further increased so that, for example, three or eight radiation sources are provided. At the same time, the number of detectors can also be increased accordingly.

7 shows a portion of a further embodiment with a first radiation source 11 and a second radiation source 12, the radiation sources 11, 12 being analogous to FIG 4 are constructed. The tunable laser 41 and another tunable laser 51 emit radiation into the waveguide and the first Bragg grating 43 is arranged in such a way that radiation emitted by the first tunable laser 41 goes into the first subregion 7 and radiation generated by the other tunable laser 51 goes into the second portion 8 is radiated. In both partial areas 7, 8, a plurality of emission directions 5 are again provided analogously to the methods described above. Provision can also be made to use an additional light guide and a second Bragg grating for the additional tunable laser 51 .

In one embodiment, the change in the direction of emission 5 in the first direction of extent 3 occurs quickly compared to the change in the direction of emission 5 in the second direction of extent 4. This is the case in particular when a movable mirror 30 is used for the deflection for the second direction of extent 4.

In one exemplary embodiment, a first angular range of between 20 and 30 degrees is covered in the first direction of extension 3 . More than one hundred and fifty different emission directions 5 can be set in the first extension direction 3 . This is possible in particular when three radiation sources are used and each of the radiation sources covers a third of the angular range.

8th 1 shows a LIDAR system 9 consisting of three LIDAR devices 1. Each LIDAR device 1 comprises a first radiation source 11, a second radiation source 12 and a third radiation source 13, which, for example, are analogous to FIG 7 can be constructed. Alternatively, for each radiation source 11, 12, 13 or for the radiation sources 11, 12, 13 of a LIDAR device, a 7 analog beam deflector 20 may be provided. The generated electromagnetic radiation 17 of the radiation sources 11, 12, 13 can in the first extension direction 3 perpendicular to the image plane in different emission directions 5 analogous to the 7 and 8th be given. A movable mirror 30, again designed as a facet wheel 31, is used to deflect the generated electromagnetic radiation 17 in the second direction of extension 4. This arrangement is well suited for use in LIDAR systems in vehicles, since the scanning area 2 with such a LIDAR system 9 can be scanned sufficiently quickly. For example, each radiation source 11, 12, 13 can cover between 7.5 and 9 degrees in the first direction of extent, so that in the first direction of extent 3 together between 22.5 and 27 degrees are covered. In the second direction of extent 4, each LIDAR device 1 can cover between 40 and 60 degrees, so that a total of between 120 and 180 degrees are covered.

9 shows a diagram 100 of a profile of the radiation angle 102 over a time axis 101 of the three radiation sources 11, 12, 13 of one of the LIDAR devices 1 with three radiation sources 11, 12, 13, in particular that of 8th . A step function is used for each radiation source 11, 12, 13 and the radiation angle 102 is defined accordingly. After a time T, the step function is run through again. For example, between 50 and 60 steps can be provided for each of the radiation sources 11, 12, 13, so that, for example, a resolution between 0.125 degrees and 0.225 degrees. The time T can be between 0.2 and 0.3 milliseconds.

10 FIG. 10 shows a diagram 100 of a profile of the emission angle 102 over a time axis 101 of the three LIDAR devices 1 of FIG 8th . The use of the facet wheel 31, which rotates at a constant angular velocity, results in a sawtooth-like progression. After a time T', the sawtooth is run through again. Provision can be made for a total of between 300 and 400 measurement points to be recorded for each facet pass, so that a resolution of between 0.1 degree and 0.2 degree results, for example. The time T' can be between 0.08 and 0.15 seconds.

With the in the 9 and 10 With the deflection functions shown and the parameters mentioned, a LIDAR system 9 can be implemented which, for example, has a total beam angle 103 of 24.3 degrees with 162 pixels resolution in the first direction of extent 3 and a total beam angle 103 of 150 degrees with 1002 pixels in the second direction of extent has resolution.

A spot is advanced by the facet wheel 31 during the measurement. 11 shows respectively a backscattered and/or reflected radiation at the beginning of an integration 104 (vertical lines) and a backscattered and/or reflected radiation at the end of an integration 105 (horizontal lines) for three different distances of an object to the LIDAR device, above in the near range, in the middle for about half a maximum range and at the bottom for an object in the range of the maximum range. Because T is significantly smaller than T', the deflection caused by moving the facet wheel further is negligible, since even at the maximum range, there is a large overlap between the backscattered and/or reflected radiation at the beginning of an integration 104 and the backscattered and/or reflected radiation yields 105 at the end of an integration. This is particularly advantageous when using the LIDAR system 9 as an FMCW LIDAR, since here the emitted radiation is compared with the backscattered and/or reflected radiation and the emitted radiation corresponds to the backscattered and/or reflected radiation at the end of an integration 105 due to the principle , while the backscattered and/or reflected radiation at the beginning of an integration 104 is used as the backscattered and/or reflected radiation.

Although the invention has been described in detail by the preferred embodiments, the invention is not limited to the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (10)

LIDAR device (1) for scanning a scanning area (2), having a first radiation source (11) for generating electromagnetic radiation (17) and a first detector (14) for receiving radiation backscattered and/or reflected from the scanning area (2). Radiation (18), the scanning region (2) having a first direction of extent (3) and a second direction of extent (4), the first radiation source (11) having different emission directions (5) in the first direction of extent (3), the different Emission directions (5) can be adjusted by means of an interference effect by changing a parameter, the LIDAR device (1) also having a controller (6), the controller (6) being set up to change the parameter, the change in the parameter takes place in such a way that the generated electromagnetic radiation (17) is emitted in each emission direction (5) for a predetermined period of time. LIDAR device (1) according to claim 1 , wherein the parameter is changed in such a way that the emission direction (5) corresponds to a step function over time. LIDAR device (1) according to claim 1 or 2 , wherein the first radiation source (11) comprises a tunable laser (41), wherein the LIDAR device comprises a first Bragg grating (43), wherein the generated electromagnetic radiation (17) through the first Bragg grating (43) for different Wavelengths in different emission directions (5) is emitted. LIDAR device (1) according to claim 3 , the tunable laser (41) having a resonator (46), the resonator being formed from (46) two resonator gratings (47, 48), a grating constant of the resonator gratings (47, 48) being different. LIDAR device (1) according to claim 3 or 4 , further having a second radiation source (12), wherein the second radiation source (12) comprises a further tunable laser (51) and wherein the first radiation source (11) and the second radiation source (12) each have a partial area (7, 8) of the emission area (2) cover with respect to the first direction of extent (3). LIDAR device (1) according to claim 5 , Wherein the generated electromagnetic radiation (17) of the first radiation source (11) and the second radiation source (12) by means of the first Bragg grating (43) is radiated in different directions. LIDAR device (1) one of Claims 1 until 6 , wherein the generated electromagnetic radiation (17) is deflected in the second direction of extent (4) by means of a movable mirror (30). LIDAR device (1) one of Claims 1 until 7 , wherein the change in the direction of emission (5) in the first direction of extent (3) occurs quickly compared to the change in the direction of emission (5) in the second direction of extent (4). LIDAR device (1) one of Claims 1 until 8th , wherein in the first direction of extent (3) a first angular range between 20 and 30 degrees is covered and wherein in the first direction of extent (3) more than one hundred and fifty different emission directions (5) can be set. LIDAR system (9) consisting of several LIDAR devices (1) according to one of Claims 1 until 9 .

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