DE102018203315A1 - Device for scanning distance determination of an object - Google Patents

Abstract

The invention relates to a device for scanning distance detection of an object, having a light source (110, 210, 310) for emitting an optical signal (111, 211, 311) with a time-varying frequency, an evaluation device for determining a distance of the object (140, 240 340) on the basis of a measurement signal (121, 221, 321) reflected from the signal and a reference signal (122, 222, 322) not reflected by the object, and a dispersive element (131, 231, 331) which effects a frequency-selective angular distribution of the measurement signal (121, 221, 321), whereby partial signals generated thereby are directed at different angles to the object (140, 240, 340).

Description

BACKGROUND OF THE INVENTION

Field of the invention

The invention relates to a device for scanning distance determination of an object. The device can be used for determining distances of both moving and still objects and in particular for determining the topography or shape of a spatially extended three-dimensional object.

State of the art

For optical distance measurement of objects u.a. a measuring principle, also referred to as lidar, in which a frequency-temporally changed optical signal is radiated toward the relevant object and evaluated after back-reflection at the object.

6a shows only a schematic representation of a known per se basic structure in which one of a light source 610 emitted signal 611 with temporally changed frequency (also referred to as "chirp") is split into two partial signals, this splitting takes place for example via a partially transparent mirror, not shown. The two sub-signals are via a signal coupler 650 coupled and to a detector 660 superimposed on each other, wherein the first sub-signal as a reference signal 622 without reflection on the " 640 "Designated object to the signal coupler 650 and to the detector 660 arrives. The second at the signal coupler 650 or at the detector 660 however incoming partial signal runs as a measuring signal 621 via an optical circulator 620 and a scanner 630 to the object 640 , is reflected back from this and thus comes in comparison to the reference signal 622 with a time delay and correspondingly changed frequency to the signal coupler 650 and to the detector 660 ,

An evaluation device (not shown) receives the signal from the detector 660 supplied detector signal relative to the measuring device or the light source 610 evaluated, with the recorded at a given time, in the diagram of 6b illustrated difference frequency 631 between measuring signal 621 and reference signal 622 characteristic of the distance of the object 640 from the measuring device or the light source 610 is. According to 6b can thereby obtain additional information regarding the relative speed between the object 640 and the measuring device or the light source 610 the time-dependent frequency response of the light source 610 emitted signal 611 also be such that there are two sections in which the time derivative of the light source 610 generated frequency is opposite to each other.

In practice, there is a need, even in larger spaced (possibly also moving) objects in which it is e.g. To act vehicles in traffic, to realize the most accurate and reliable distance measurement. It is further desirable in view of the highest possible reliability and lifetime of the device for distance determination to avoid or minimize the use of movable components such as scanning or deflection when scanning the respective object.

The prior art is merely an example US 2016/0299228 A1 directed.

SUMMARY OF THE INVENTION

Against the above background, it is an object of the present invention to provide a device for scanning distance detection of an object, which also enables a distance measurement which is as accurate and reliable as possible for an object located at a comparatively large distance (for example of several 100 m).

This object is solved by the features of independent claim 1.

• - eine Lichtquelle zum Aussenden eines optischen Signals mit zeitlich variierender Frequenz;
• - eine Auswerteeinrichtung zur Ermittlung eines Abstandes des Objekts auf Basis eines aus dem Signal hervorgegangenen, an dem Objekt reflektierten Messsignals und eines nicht an dem Objekt reflektierten Referenzsignals; und
• - ein dispersives Element, welches eine frequenzselektive Winkelverteilung des Messsignals bewirkt, wobei hierdurch erzeugte Teilsignale unter voneinander verschiedenen Winkeln zu dem Objekt gelenkt werden.

An apparatus according to the invention for scanning distance detection of an object has:

• a light source for emitting an optical signal having a time-varying frequency;
• an evaluation device for determining a distance of the object on the basis of a signal signal which has emerged from the signal and which is reflected on the object and a reference signal which is not reflected by the object; and
• - A dispersive element which causes a frequency-selective angular distribution of the measuring signal, thereby generated partial signals are directed at different angles to each other to the object.

The invention is based in particular on the concept, in a device for distance determination of an object, starting from the basis of FIG 6a-6b described principle to realize a scanning of the object in that in the signal path even before the object via a dispersives element, an angular distribution and optionally spatial distribution of the light emitted from a light source optical signal, different frequencies is effected, these frequencies (or the respective frequencies having partial beams) - as will be described later, possibly adjusted via an optional optical system - with different tilt or at different angles are directed to the object.

As a result, scanning of the object is effectively achieved in this manner without the need for moving components such as scanning or deflection mirrors. As a result, problems typically associated with the use of such movable components, particularly failure risks and concomitant reliability and device life limitations, are also avoided. At the same time, a particularly compact construction is made possible.

According to one embodiment, a collimating optical element is arranged relative to the signal path in front of the dispersive element. By means of such an optional collimating optical element, a possibly collimated beam path can be ensured, if necessary, when hitting the dispersive element.

According to one embodiment, an optical system is provided between the dispersive element and the object for adapting the respective angles at which the partial signals are directed to the object.

According to one embodiment, the optical system comprises a first lens and a second lens. In this case, in particular, the dispersive element can be arranged in a first focal plane of the first lens. According to one embodiment, a field plane of this optical system further corresponds to a first focal plane of the second lens.

In the construction described above, the different angles of the different angles of the partial signals generated by the frequency-selective angular distribution of the measurement signal are first translated from the first lens to different locations of a field plane, which in turn are translated via the second lens in an angular distribution. The partial beams corresponding to the different frequencies occur here at different times (i.e., the different locations provided via the dispersive element in a field plane illuminate at different times).

Also in this embodiment, the desired scanning of the object is thus achieved without the requirement of moving components such as scanning or deflection mirrors already in that corresponding to the temporal variation of the frequency of the optical signal emitted from the light source different field points (corresponding to the by the dispersive element and the first lens provided frequency-selective spatial distribution) sequentially light up in time, this local variation is translated by the second lens of the optical system in turn into an angular distribution.

In the context of the invention in terms of their distance from the device according to the invention measured objects may be only exemplary (and without the invention being limited thereto) to robot components such as robot arms or to relevant in the road or automotive sector objects (eg foreign vehicles). In addition to determining the distance, it is also possible, for example, to determine the speed (such as, for example, from US 2016/0299228 A1 known).

According to one embodiment, the dispersive element has an AWG (= "array waveguide grating"). The use of such an AWG is particularly advantageous insofar as a (wafer) integrated and thus particularly compact design is made possible. In particular, the AWG can have at least 120 channels, in particular at least 240 channels. With a correspondingly high number of channels, the dispersion of the dispersive element and thus the speed of the scanning can be further increased.

However, the invention is not limited to the realization of the frequency-selective spatial division via an AWG. In other embodiments, another dispersive element providing frequency selective spatial division, such as a prism, a diffraction grating or Bragg grating, or a spatial light modulator (e.g., an acoustic or electro-optic modulator) may also be used.

According to one embodiment, the dispersive element has an array of periodic structures extending in two mutually perpendicular spatial directions. In this case, a period length of these periodic structures can be in particular in the range from 50 μm to 150 μm, in particular in the range from 80 μm to 120 μm.

With such a two-dimensional configuration, a two-dimensional (ie in the x-direction as in y-direction) scanning of the object without requiring moving components such as scanning or deflection mirror can be performed with the result that overall high scan rates at the same time high reliability and compact structure can be achieved.

Further embodiments of the invention are described in the description and the dependent claims.

The invention will be explained in more detail with reference to embodiments shown in the accompanying drawings.

list of figures

• 1 eine schematische Darstellung zur Erläuterung des Aufbaus einer erfindungsgemäßen Vorrichtung in einer ersten Ausführungsform;
• 2 eine schematische Darstellung zur Erläuterung des Aufbaus einer erfindungsgemäßen Vorrichtung in einer weiteren Ausführungsform;
• 3a-3c schematische Darstellungen zur weiteren Erläuterung von Aufbau und Funktionsweise einer erfindungsgemäßen Vorrichtung in einer weiteren Ausführungsform;
• 4a-4b schematische Darstellungen zur Erläuterung möglicher Ausführungsbeispiele der Erfindung;
• 5 eine schematische Darstellungen einer weiteren Ausführungsform der Erfindung; und
• 6a-6b schematische Darstellung zur Erläuterung von Aufbau und Wirkungsweise einer herkömmlichen Vorrichtung zur Abstandsermittlung.

Show it:

• 1 a schematic representation for explaining the structure of a device according to the invention in a first embodiment;
• 2 a schematic representation for explaining the structure of a device according to the invention in a further embodiment;
• 3a-3c schematic representations to further explain the structure and operation of a device according to the invention in a further embodiment;
• 4a-4b schematic representations for explaining possible embodiments of the invention;
• 5 a schematic representations of another embodiment of the invention; and
• 6a-6b schematic representation for explaining the structure and operation of a conventional device for distance determination.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, construction and mode of operation of a device according to the invention in an exemplary embodiment will be described with reference to the schematic illustration in FIG 1 described.

According to 1 shows a device according to the invention first, starting from the already using 6a-6b described, conventional concept, a light source 110 for emitting an optical signal 111 with time varying frequency ("chirp") on. The light source 110 can only have a (central) wavelength of 1550 nm ± 100 nm by way of example. Other wavelengths or bandwidths (eg 910nm ± 50nm) are also possible. According to the in the upper left part of 1 Plotted diagram shows the optical signal 111 in the exemplary embodiment, a frequency response with linear time dependence. In embodiments of the invention, portions with mutually opposite time derivative of the frequency can be analogous to 6b be used.

In addition to the conventional concept of 6a-6b analogous manner according to 1 a splitting of the light source 110 emitted signal 111 for example, via a partially transparent mirror, not shown. Of these sub-signals, a "measuring signal" 121 designated sub-signal via an optical circulator 120 as described below on an object to be measured with regard to its distance from the device 140 whereas the other of the two sub-signals is referred to as a reference signal as described below 122 is used for further evaluation.

According to 1 arrives (the measuring signal 121 corresponding) beam 101 , which at different times different frequencies f ₁ . f ₂ . f ₃ . f ₄ , ..., on a dispersion element 131 , from which different frequencies (ie the respective frequencies having partial beams) in mutually different directions (corresponding to different angles φ ₁ , φ ₂ , φ ₃ , φ ₄ , ...) to the object 140 be distracted. This will effectively scan the object 140 achieved without the requirement of moving components such as scanning or deflection mirrors.

According to 1 takes place in a coupler 145 the merger of the measurement signal as described above 121 generated partial signals 121 . 121b . 121c . 121d , ... with the reference signal 122 with the result that by a subsequent detector arrangement 150 generated detector signals respectively - as in the lower right part of 1 indicated - are characteristic of the difference frequency between the frequency of the respective sub-signal and the frequency of the reference signal. In this case, in the lower right part of 1 diagram shown the sub-signals 121 . 121b . 121c or. 121d each the mean frequency f ₁ . f ₂ . f ₃ or f4. As a result, for each of the angles φ ₁ , φ ₂ , φ ₃ , φ ₄ ,... The corresponding difference signal and thus again the searched distance of the object 140 be determined.

2 shows a further embodiment, wherein 1 Analogous or substantially functionally identical components with " 100 "Increased reference numerals are designated. According to 2 is related to the signal path in front of the dispersive element 231 a collimating optical element 225 arranged, by which, if necessary, a possible collimated beam path can be ensured when hitting the dispersive element.

3a shows a further embodiment, wherein 1 Analogous or substantially functionally identical components with " 200 "Increased reference numerals are designated.

According to 3a is between the dispersive element 331 and the object 340 an optical system is provided. As described below, this optical system permits adaptation of the respective angles, among which the partial signals generated by frequency-selective spatial division of the measurement signal to the object 340 be steered.

According to 3a the optical system has a first lens 332 and a second lens 334 on. Here is the dispersive element 331 in a first focal plane FP1 the first lens 332 arranged. Furthermore corresponds to a field level 333 the optical system of a first focal plane of the second lens 334 ,

According to 3b arrives (the measuring signal 321 corresponding) beam 301 , which at different times different frequencies f ₁ . f ₂ . f ₃ . f ₄ , ..., on the dispersion element 331 , from which different frequencies (ie the respective frequencies having partial beams) in different directions (corresponding to each other different angles φ ₁ , φ ₂ , φ ₃ , φ ₄ , ...) are deflected. The dispersion element 331 is located in the first focal plane FP1 of the first lens 332 which is a field at the field level 333 generated. The different frequencies f ₁ . f ₂ . f ₃ . f ₄ , Sub-beams are here on different places in the field level 333 focused.

The field level 333 in turn corresponds to a first focal plane FP2 of the second lens 334 , The from different places in the field level 333 outgoing partial beams are transmitted through the second lens 334 again in mutually different directions (corresponding to each other different angles θ ₁ . θ ₂ . θ ₃ . θ ₄ , ...) distracted, which in turn different frequencies f ₁ . f ₂ . f ₃ . f ₄ ,... correspond. Because these each have different frequencies f ₁ . f ₂ . f ₃ . f ₄ , ... corresponding partial beams occur at different times (ie the different locations in the field level 333 at different times), this in turn effectively scanning the object 340 out 3a achieved.

3c shows a further schematic illustration for explaining the embodiment of 3a-3b underlying principle. Accordingly, they are located above the dispersive element 331 in the field level 333 provided different locations in the first focal plane of the (achromatic) second lens 334 (ie at a distance of the focal length F of the second lens) and illuminate sequentially (ie at different successive points in time) in accordance with the temporal frequency curve. One from a place in the field level 333 at a distance " X "From the optical system axis OA Outgoing beam gets a tilt here θ to the optical system axis OA , which is given by θ = x / F. The beam size D is in accordance with 3 determined by the numerical aperture NA and the focal length F according to D = 2 · F · NA, ie F = D / (2 · NA).

Exemplary quantitative values for the beam size D may be in the range of D = (10-15) mm for the aforementioned traffic applications. Set a typical value of the numerical aperture N / A of 0.12, suitable values for the focal length F are thus on the order of magnitude of approximately 50 mm, so that a comparatively compact system can be realized.

With regard to the angular resolution which can be achieved with the device according to the invention, typical values to be demanded for the above-mentioned applications in the road traffic or automobile sector can be, for example, 2 mrad. It follows with reference to 4a with the above-mentioned value of the focal length F = 50mm a period length in the field level 333 (ie, a distance of adjacent channels provided by the dispersive element) of about 0.1mm. Restricted by reference to 4b the free aperture of the lens 334 on CA = 70mm, so follows for the maximum distance x _max from the optical system axis OA, the one still from the lens 334 Shown bright spot in the field level 333 may in the above example X _max = (CA-D) / 2 = (70-12) / 2mm = 29mm. The numerical aperture NA _scan results in NA _scan = X _max /F=(29/50)mm=0.58. For the number of channels (or luminous "sources") in the field level 333 N _max = 2 • X _max • / dx = 580.

The value of the period length selected in the above example in the field level 333 (ie, the spacing of adjacent channels provided by the dispersive element) of about 0.1mm = 100μm also allows for a two-dimensional configuration corresponding to a two-dimensional array of channels (or luminous "sources"), as shown schematically in FIG 5 is shown. According to 5 Not only in the x-direction, but also in the y-direction is such a periodic sequence of channels (or luminous "sources") realized with the period length of a = 100 .mu.m. In this case, the fact can be exploited that the size of the (by in each case a diffractive structure 502 leading waveguide 501 Even with an AWG with an Si / SiO ₂ platform, only approx. b = 10 μm, with the result that a two-dimensionally staggered arrangement such as 5 is possible. For other platforms (eg a Si platform) even smaller channel sizes are possible, so that at the above period length of a = 100μm a even larger scan or angle range can be realized in a two-dimensional scanner.

With the basis of 5 a two-dimensional (ie, in the x-direction as in y-direction) scanning of the object without requiring moving components such as scanning or deflection mirror can be performed with the result that overall high scan rates at the same time high reliability and compact design can be achieved.

However, the invention is also in only one-dimensional design of the channels provided by the dispersive element (as with reference to 2 to 4 described) advantageous. This applies in addition to applications in which a one-dimensional (eg only in the x-direction) scanning of the object is sufficient anyway, even for applications with two-dimensional (ie in the x-direction as in y-direction take place) scanning of the object, since in this Trap for scanning in the not along the periodic sequence of channels extending spatial direction (in the example y-direction) is a comparatively slow moving scanning mirror for scanning in this spatial direction is sufficient.

While the invention has been described in terms of specific embodiments, numerous variations and alternative embodiments, e.g. by combination and / or exchange of features of individual embodiments. Accordingly, it will be understood by those skilled in the art that such variations and alternative embodiments are intended to be embraced by the present invention, and the scope of the invention is to be limited only in terms of the appended claims and their equivalents.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2016/0299228 A1 [0006, 0017]

Claims (11)

Apparatus for scanning distance determination of an object, with A light source (110, 210, 310) for emitting an optical signal (111, 211, 311) having a time-varying frequency; An evaluation device for determining a distance of the object (140, 240, 340) on the basis of a measurement signal (121, 221, 321) emerging from the signal (111, 211, 311) and reflected on the object (140, 240, 340) and a reference signal (122, 222, 322) not reflected on the object (140, 240, 340); and A dispersive element (131, 231, 331) which effects a frequency-selective angular distribution of the measurement signal (121, 221, 321), whereby partial signals generated thereby are directed at different angles to the object (140, 240, 340). Device after Claim 1 , characterized in that relative to the signal path in front of the dispersive element (231), a collimating optical element (225) is arranged. Device after Claim 1 or 2 characterized in that between the dispersive element (331) and the object (340) is provided an optical system for adjusting the respective angles at which the sub-signals are directed to the object (340). Device after Claim 3 , characterized in that the optical system comprises a first lens (332) and a second lens (334). Device after Claim 4 , characterized in that the dispersive element (331) in a first focal plane (FP1) of the first lens (332) is arranged. Device after Claim 4 or 5 , characterized in that a field plane (333) of this optical system corresponds to a first focal plane of the second lens (334). Device according to one of Claims 1 to 6 , characterized in that the dispersive element (131, 231, 331) has an AWG. Device after Claim 7 , characterized in that AWG has at least 120 channels, in particular at least 240 channels. Device according to one of Claims 1 to 6 , characterized in that the dispersive element (131, 231, 331) comprises a prism, a diffraction grating or a spatial light modulator, in particular an acoustic or electro-optical modulator. Device according to one of the preceding claims, characterized in that the dispersive element (131, 231, 331) has an array of periodic structures extending in two mutually perpendicular spatial directions. Device after Claim 10 , characterized in that a period length of these periodic structures in the range of 50μm to 150μm, in particular in the range of 80μm to 120μm, is located.

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