DE102018129152A1 - Device for two-dimensionally scanning beam deflection of a light beam - Google Patents

Abstract

The invention relates to a device for two-dimensionally scanning beam deflection of a light beam, having a spectrally tunable light source (10) for emitting a light beam with a wavelength that varies over time, a first optical component (13) for generating a first beam deflection, in which partial beams resulting from the light beam are wavelength-dependent are deflected in each case in a first direction, the deflection angles generated in the first beam deflection periodically varying with spectral tuning of the wavelength, and a second optical component (16) for generating a second beam deflection, in which the partial beams deflected by the first optical component before or after this deflection, depending on the wavelength, are deflected in a second direction different from the first direction, the deflection angles generated in this second beam deflection being monotonically spectral Wavelength vary.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a device for two-dimensionally scanning beam deflection of a light beam. The device can be used in particular for scanning beam deflection when determining distances between both moving and still objects and for determining the topography or shape of one or more spatially extended three-dimensional objects.

State of the art

For optical distance measurement of objects, a measuring principle also known as LIDAR is known, in which an optical signal that is continuously changed in frequency with respect to the object in question is emitted and evaluated after back reflection on the object.

5a shows only a schematic representation of a known basic structure, in which a spectrally tunable light source 50 emitted signal 51 is split into two partial signals at a frequency which has changed over time (also referred to as “chirp”), this split taking place via a beam splitter (not shown) (for example a partially transparent mirror or a fiber-optic splitter). The two partial signals are via a signal coupler 57 coupled and to a detector 58 superimposed on one another, the first partial signal being the reference signal 53 without reflection on the with " 56 “Designated object to the signal coupler 57 and to the detector 58 reached. The second on the signal coupler 57 or at the detector 58 incoming partial signal, however, runs as a measurement signal 52 via an optical circulator 54 and a scanner 55 to the object 56 , is reflected back by it and thus comes in comparison to the reference signal 53 with a time delay and a correspondingly changed frequency to the signal coupler 57 and to the detector 58 .

The detector detects this via an evaluation device (not shown) 58 delivered detector signal relative to the measuring device or the light source 50 evaluated, the one recorded at a certain point in time in the diagram of 5b difference frequency shown 59 between measurement signal 52 and reference signal 53 characteristic of the distance of the object 56 from the measuring device or the light source 50 is. According to 5b can be used to obtain additional information regarding the relative speed between the object 56 and the measuring device or the light source 50 the time-dependent frequency response of the light source 50 emitted signal 51 also be such that there are two sections in which the time derivative of the from the light source 50 generated frequency is opposite to each other.

In practice, there is a need to implement a distance measurement that is as accurate and reliable as possible, even in the case of objects located at greater distances (possibly also moving), which may be vehicles in road traffic, for example. In view of the highest possible reliability and service life of the device for determining the distance, it is further desirable to avoid or minimize the use of movable components such as scanning or deflecting mirrors when scanning the respective object. One possible approach involves designing the scanner 55 using a dispersive optical element, for example in the form of an AWG (= "Arrayed Waveguide Grating" = "Waveguide Structure Array"). With such a "dispersive scanner" they can be from the light source 50 Partial beams emitted light, which have different frequencies, are spatially separated and at different angles to the object 56 be directed. Depending on the application, there is a need for realizing as large a field of view as possible (FOV = Field of View "), which must be" scanned "by the respective measuring beam in a spatially resolved manner. For example, use in road traffic requires a two-dimensional spatial resolution (perpendicular to the measurement beam direction) of N * M measurement points or pixels, N and M each preferably being greater than 100.

In practice, this results in the problem that on the one hand the achievable angular resolutions of an AWG are limited, but on the other hand mechanical scanning processes, e.g. are unable to cover the required angular ranges of several tens of degrees due to the inertia or the too slow reactivity of mirrors used here. In particular, it proves to be problematic to carry out two-dimensional scanning processes with a sufficiently high speed and high resolution using mechanically movable components, e.g. using galvanometer mirrors or rotary scanners).

The realization of a sufficiently fast three-dimensional data acquisition e.g. when scanning objects such as vehicles, this is a demanding challenge in practice.

The state of the art is only given as an example US 2018/024246 A1 , WO 2018/107237 A1 as well as the publication M. Shirasaki: "Virtually Imaged Phased Array", FUJITSU Sci. Tech. J. 35, pp. 113-125 (1999) referred.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention to provide a device for two-dimensionally scanning beam deflection of a light beam, which enables a sufficiently fast two-dimensional scanning process while avoiding the problems described above.

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

• - eine spektral durchstimmbare Lichtquelle zum Aussenden eines Lichtstrahls mit zeitlich variierender Wellenlänge,
• - eine erste optische Komponente zur Erzeugung einer ersten Strahlablenkung, bei welcher aus dem Lichtstrahl hervorgegangene Teilstrahlen wellenlängenabhängig jeweils in einer ersten Richtung abgelenkt werden, wobei die bei der ersten Strahlablenkung erzeugten Ablenkwinkel mit spektraler Durchstimmung der Wellenlänge periodisch variieren, und
• - eine zweite optische Komponente zur Erzeugung einer zweiten Strahlablenkung, bei welcher die von der ersten optischen Komponente abgelenkten Teilstrahlen vor oder nach dieser Ablenkung wellenlängenabhängig jeweils in einer von der ersten Richtung verschiedenen zweiten Richtung abgelenkt werden, wobei die bei dieser zweiten Strahlablenkung erzeugten Ablenkwinkel mit spektraler Durchstimmung der Wellenlänge monoton variieren.

A device according to the invention for two-dimensionally scanning beam deflection of a light beam has:

• a spectrally tunable light source for emitting a light beam with a wavelength that varies over time,
• a first optical component for generating a first beam deflection, in which partial beams emerging from the light beam are deflected in a first direction depending on the wavelength, the deflection angles generated in the first beam deflection varying periodically with spectral tuning of the wavelength, and
• - A second optical component for generating a second beam deflection, in which the partial beams deflected by the first optical component are deflected before or after this deflection depending on the wavelength in each case in a second direction different from the first direction, the deflection angles generated in this second beam deflection being spectral Vary the wavelength monotonically.

The invention is based in particular on the concept of realizing a two-dimensional scanning beam deflection in that, in combination with a light source which can be spectrally tuned in terms of its wavelength, at least two optical components which are arranged one after the other in relation to the direction of light propagation or successively traversed by the light, each of which is used by the Generate wavelength-dependent deflection angles, the respective variation of the deflection angle being periodic in one component and wavelength monotonous in the other with the spectral tuning.

With regard to the periodic variation of the deflection angle with the wavelength occurring in one of the two optical components, the invention is based on the consideration that a "simple combination" of two dispersive components - e.g. by using two crossed gratings - would not be expedient for the intended realization of a two-dimensional (i.e. horizontal and vertical) beam deflection, since the spectral tuning of the light source over the entire spectral range would only lead to the scanning of a diagonal line.

Rather, the invention is based on the consideration that for the realization of a two-dimensional scanning beam deflection or a two-dimensional scanning of an object, an optical component acting continuously or monotonously with respect to the wavelength-dependent beam deflection, such as e.g. a grating or prism is to be combined with another component, which just does not show a characteristic of the wave dependence of the deflection angle that runs monotonously over the entire spectral range, but rather, with regard to the deflection angle provided in each case, repeatedly runs through one and the same deflection angle range with spectral tuning of the light source.

In contrast to a "simple" arrangement of two crossed gratings - as not stated above - the combination according to the invention of a spectrally "periodically operating" angle-deflecting optical component with a continuously or "monotonously operating" angle-deflecting optical component ( "periodic" and "monotonous" each refer to the wavelength dependence of the deflection angle) a real two-dimensional scanning process can be achieved at high speed.

In embodiments of the invention, the first optical component can be a VIPA (= “Virtually Imaged Phased Array”). Such a VIPA can be constructed in a manner known per se and, as will be described further below, from a semi-cylindrical lens and a glass plate subsequently tilted in the beam path, with “line-focused” light entering the glass plate via the semi-cylindrical lens and from this at a wavelength dependent deflection angles emerges.

However, the invention is not limited to the use of a VIPA, with other embodiments of the spectrally “periodically operating” angle-deflecting optical component, e.g. in the form of an Echelle grating.

In the second (with regard to the wavelength dependency of the deflection angle generated above the spectral range "monotonous" optical component can be a grating, a prism or a combination of these elements. In particular, in embodiments, the second component for enlarging the realizable angular range can also be constructed from two grids.

It should be pointed out that the second optical component (which works monotonously with regard to the wavelength dependency of the generated deflection angles) can alternatively be arranged after or also before the first optical component (which operates periodically with regard to the wavelength dependency of the generated deflection angles).

The invention further relates to the use of a device with the features described above in a LIDAR system for scanning the distance of an object.

• - einer spektral durchstimmbaren Lichtquelle zum Aussenden eines Lichtstrahls mit zeitlich variierender Wellenlänge,
• - einer Auswerteeinrichtung zur Ermittlung eines Abstandes des Objekts auf Basis von aus den optischen Signalen jeweils hervorgegangenen, an dem Objekt reflektierten Messsignalen und nicht an dem Objekt reflektierten Referenzsignalen, und
• - einer Scaneinrichtung, welches eine wellenlängenabhängige Winkelverteilung der zu dem Objekt gelenkten Messsignale bewirkt, wobei diese Scaneinrichtung aufweist:
• - eine erste optische Komponente zur Erzeugung einer ersten Strahlablenkung, bei welcher aus dem Lichtstrahl hervorgegangene Teilstrahlen wellenlängenabhängig jeweils in einer ersten Richtung abgelenkt werden, wobei die bei der ersten Strahlablenkung erzeugten Ablenkwinkel mit spektraler Durchstimmung der Wellenlänge periodisch variieren, und
• - eine zweite optische Komponente zur Erzeugung einer zweiten Strahlablenkung, bei welcher die von der ersten optischen Komponente abgelenkten Teilstrahlen vor oder nach dieser Ablenkung wellenlängenabhängig jeweils in einer von der ersten Richtung verschiedenen zweiten Richtung abgelenkt werden, wobei die bei dieser zweiten Strahlablenkung erzeugten Ablenkwinkel mit spektraler Durchstimmung der Wellenlänge monoton variieren.

The invention further relates to a LIDAR system for scanning the distance determination of an object, with

• a spectrally tunable light source for emitting a light beam with a wavelength that varies over time,
• an evaluation device for determining a distance of the object on the basis of measurement signals, which originate from the optical signals and are reflected on the object and not on the object, and
• a scanning device which effects a wavelength-dependent angular distribution of the measurement signals directed to the object, this scanning device having:
• a first optical component for generating a first beam deflection, in which partial beams emerging from the light beam are deflected in a first direction depending on the wavelength, the deflection angles generated in the first beam deflection varying periodically with spectral tuning of the wavelength, and
• - A second optical component for generating a second beam deflection, in which the partial beams deflected by the first optical component are deflected before or after this deflection depending on the wavelength in each case in a second direction different from the first direction, the deflection angles generated in this second beam deflection being spectral Vary the wavelength monotonically.

Further refinements of the invention can be found in the description and the subclaims.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the attached figures.

Figure list

• 1a-b schematische Darstellungen zur Erläuterung des möglichen Aufbaus einer erfindungsgemäßen Vorrichtung;
• 2 ein Diagramm zur Erläuterung der Funktionsweise eines in der Vorrichtung von 1 eingesetzten VIPA (=„Virtually Imaged Phased Array“ = virtuell abgebildetes phasengesteuertes array);
• 3-4 schematische Darstellungen zur Erläuterung weiterer Ausführungsformen der Erfindung; und
• 5a-5b schematische Darstellungen zur Erläuterung von Aufbau und Wirkungsweise einer herkömmlichen Vorrichtung zur Abstandsermittlung.

Show it:

• 1a-b schematic representations to explain the possible structure of a device according to the invention;
• 2nd a diagram for explaining the operation of a in the device of 1 VIPA used (= "Virtually Imaged Phased Array" = virtually mapped phased array);
• 3-4 schematic representations for explaining further embodiments of the invention; and
• 5a-5b schematic representations for explaining the structure and mode of operation of a conventional device for determining the distance.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Furthermore, the structure which is possible in principle and the mode of operation of a device according to the invention for two-dimensionally scanning beam deflection are first described with reference to the schematic illustrations of 1a-1b such as 2nd described.

According to 1a-1b the device according to the invention has a spectrally tunable (ie variable with respect to the wavelength of the emitted light) light source 10th for emitting a light beam with a wavelength that varies over time. This light beam is made according to 1a-1b over a fiber or an optical fiber 11 a collimator 12 supplied in the form of a converging lens, for example, and collimates a first optical component 13 to generate a first beam deflection which, as explained below, runs periodically with regard to the wavelength dependence of the deflection angles provided.

This first component 13 is designed in the exemplary embodiment as a VIPA (= “Virtually Imaged Phased Array”) and comprises a half-cylinder lens 14 and a glass plate 15 . In this context, the publication M. Shirasaki: "Virtually Imaged Phased Array", FUJITSU Sci. Tech. J. 35, pp. 113-125 (1999) referred. The coupling of the collimated beam via the half-cylinder lens 14 into the glass plate 15 leads in a manner known per se and as in 1a indicated for multiple reflection as well as constructive interference to a plane wave, the direction of propagation or angle of which depends on the wavelength and the “diffraction order” for this interference. The result is, for example, that in the diagram of 2nd dependence depicted on the first optical component 13 each provided deflection angle. This will be like 2nd evidently, with increasing wavelength, one and the same deflection angle ranges are repeated and run through periodically (a change in the wavelength by 15 nm in the illustrated embodiment corresponding to a change in the deflection angle by approximately 25 ° merely by way of example).

The one from the first optical component 13 or the glass plate 15 emerging partial beams meet accordingly 1a-1b to a second optical component 16 , which in the exemplary embodiment - but without the invention being restricted to this - is designed as a grating and a beam deflection of the partial beams in question relative to the beam deflection of the first optical component 13 vertical direction. In contrast to the first optical component 13 or the VIPA, the second optical component works 16 such that the deflection angles generated in each case vary monotonically with the wavelength, so that the result is the spectral tuning of the light source 10th a two-dimensional scanning process is realized.

In further embodiments, instead of a single grating for increasing the angular deflection or increasing the realizable angular range of the angular deflection, an arrangement of several gratings on the side of the second (ie the “monotonously working”) angle-deflecting optical component 16 be used.

An exemplary suitable embodiment is shown schematically in 3rd shown, with two flat grids 31 , 32 on edge surfaces of a prism 30th are trained. Such a multiple grid configuration can thus be referenced in particular with reference to the embodiment of FIG 1a-1b replacing the existing grid 16 as a second optical component (which generates deflection angles that vary monotonically with the wavelength).

The two-dimensionally scanning beam deflection according to the invention can be used in an exemplary advantageous application in a LIDAR system on the basis of the 5a-5b described conventional structure (with appropriate design of the scanner 55 with the arrangement of the first optical component according to the invention 13 and second optical component 16 ) are used.

However, the invention is not limited to this application, but can be implemented very advantageously in general in applications in which a two-dimensional beam deflection for wavelength-based (ie by spectral tuning of a light source) control of different locations or points in space without mechanically moving components is desired (although the wavelength of the light directed to the respective locations is not relevant itself and is only used for the above-described realization of the scanning process).

4th shows only a schematic representation of a further advantageous arrangement for realizing a two-dimensional scanning beam deflection, which is also based on the use of a spectrally tunable light source 40 based. According to 4th includes one about an axis 46 as indicated rotatable component a parabolic mirror 44 in combination with a grid 45 . This is one of the tunable light source 40 generated, the component via a fiber 41 supplied light beam first via a collimator 42 eg in the form of a converging lens on a focal point of the parabolic mirror 44 focused and therefore from the parabolic mirror 44 converted into a collimated beam that hits the grid 45 meets. During the spectral tuning of the light source 40 without spectral effect on the parabolic mirror 44 remains, results from the dispersion of the lattice 45 a beam deflection depending on the respective wavelength, which, in combination with said rotation of the entire component, can also result in a two-dimensional scanning process.

Although the invention has been described in terms of specific embodiments, numerous variations and alternative embodiments, e.g. by combining and / or exchanging features of individual embodiments. Accordingly, it is understood by those skilled in the art that such variations and alternative embodiments are included in the present invention and the scope of the invention is only limited within the meaning of the appended claims and their equivalents.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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.

Patent literature cited

• US 2018024246 A1 [0008]
• WO 2018/107237 A1 [0008]

Non-patent literature cited

• M. Shirasaki: "Virtually Imaged Phased Array", FUJITSU Sci. Tech. J. 35, pp. 113-125 (1999) [0008, 0027]

Claims (10)

Device for two-dimensionally scanning beam deflection of a light beam, with • a spectrally tunable light source (10) for emitting a light beam with a wavelength that varies over time; • a first optical component (13) for generating a first beam deflection, in which partial beams emerging from the light beam are deflected in a first direction depending on the wavelength, the deflection angles generated in the first beam deflection varying periodically with spectral tuning of the wavelength; and • a second optical component (16) for generating a second beam deflection, in which the partial beams deflected by the first optical component (13) are deflected before or after this deflection, depending on the wavelength, in each case in a second direction different from the first direction, with the latter being different second deflection generated deflection angle vary monotonically with spectral tuning of the wavelength. Device after Claim 1 , characterized in that the first optical component has a VIPA (= "Virtually Imaged Phased Array" = virtually depicted phase-controlled array). Device after Claim 1 , characterized in that the first optical component has an Echelle grating. Device according to one of the Claims 1 to 3rd , characterized in that the second optical component (16) has at least one grating. Device after Claim 4 , characterized in that the second optical component (16) has at least two gratings. Device according to one of the preceding claims, characterized in that the second optical component (16) has at least one prism. Device according to one of the preceding claims, characterized in that the second direction is in each case perpendicular to the first direction. Device according to one of the preceding claims, characterized in that the second component (16) is arranged after the first component (13) with respect to the direction of light propagation. Use of a device according to one of the preceding claims in a LIDAR system for scanning distance determination of an object. LIDAR system for scanning the distance of an object, with • a spectrally tunable light source (50) for emitting a light beam (51) with a wavelength that varies over time; • An evaluation device for determining a distance of the object (56) on the basis of measurement signals (52), which originate from the optical signals and are reflected on the object (56) and not on the object (56); and • a scanning device which effects a wavelength-dependent angular distribution of the measurement signals (52) directed to the object (56), this scanning device having: - A first optical component (13) for generating a first beam deflection, in which partial beams emerging from the light beam (51) are deflected in a first direction depending on the wavelength, the deflection angles generated in the first beam deflection varying periodically with spectral tuning of the wavelength; and - A second optical component (16) for generating a second beam deflection, in which the partial beams deflected by the first optical component (13) are deflected before or after this deflection, depending on the wavelength, in each case in a second direction different from the first direction, the second direction being different second deflection generated deflection angle vary monotonically with spectral tuning of the wavelength.

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