Optical device with improved aberration characteristics and laser radar equipment having the same

Abstract

An optical device is disclosed, in particular for a laser radar device, comprising a lens array with a plurality of microlenses and an objective lens for deflecting a beam from a scanning area or deflecting the beam into the scanning area, wherein the objective lens is arranged in the beam path between the scanning area and the lens array, wherein the device comprises at least one wedge array arranged in front of or behind the lens array in the radiation direction, wherein the at least one wedge array comprises a plurality of wedge elements, wherein the number of the wedge elements is equal to the number of the microlenses. In addition, a laser radar device is disclosed.

Description

Technical Field

[0001] The invention relates to an optical device, in particular for a laser radar device, comprising a lens array and an objective lens, wherein the lens array comprises a plurality of microlenses and the objective lens is used to deflect a beam from a scanning area or to deflect the beam into the scanning area, wherein the objective lens is arranged in a beam path between the scanning area and the lens array. In addition, the invention relates to a laser radar device. Background Art

[0002] Lidar devices implemented as laser scanner systems are known. Systems of this type usually use micro-optics on the transmission side to produce a beam expansion. This occurs without angular losses of the field of view or of the scanning area. The beam expansion serves, on the one hand, to increase the system robustness against local contamination of the transmission and / or reception objective, and, on the other hand, to increase eye safety and the possibility of transmitting more optical power.

[0003] However, a problem with such a lidar device is the fact that, when scanning microlens elements remote from the optical axis on the transmission side, depending on the design of the extended transmission beam diameter and the distance of the illuminated microlens elements from the optical axis, regions of different sizes of the transmission signal are deflected directly into the aperture of the transmission-receiving lens. As a result, these "cut-off" parts no longer enter the scanning area, whereby gaps or shadows of different sizes can occur in the target distance of the measuring area between adjacent light spots, depending on the scanning angle. Summary of the invention

[0004] The object on which the present invention is based can be seen as providing a lidar device and an optical arrangement which can scan a scanning area using the full field of view of the objective lens without light spot shadows and with minimized aberrations.

[0005] This object is achieved by the technical solution according to the present invention. Advantageous configurations of the present invention are preferred embodiments.

[0006] According to one aspect of the present invention, an optical device, in particular for a laser radar device, is provided. The optical device has a lens array and an objective lens, the lens array having a plurality of microlenses, and the objective lens is used to deflect a beam from a scanning area or to deflect the beam into the scanning area. The objective lens is preferably arranged in the beam path between the scanning area and the lens array. In addition, the device has at least one wedge array, which is arranged in front of or behind the lens array in the radiation direction and has a plurality of wedge elements. The number of wedge elements is preferably equal to the number of microlenses.

[0007] According to another aspect of the present invention, a laser radar device is provided, which is used to generate a beam and to scan a scanning area by means of the beam. The laser radar device has a transmitting unit and a receiving unit, the transmitting unit is used to generate the beam and to deflect the beam along the scanning area, and the receiving unit has at least one detector for receiving the reflected beam. The transmitting unit and / or the receiving unit have an optical device according to the present invention.

[0008] The objective lens may be composed of one or more lenses. In addition, the objective lens may have an aperture integrated or arranged on the objective lens to limit the maximum exit area.

[0009] By using a lens array and a wedge array in combination, the beam can be influenced in such a way that so-called light spot segments or light spot shadows no longer occur in the edge region of the objective. One advantage is that parts of the transmission signal and the reception signal that are emitted into the aperture of the objective without such an optical device can be deflected and pass through the objective.

[0010] This optical function can be realized, for example, by a wedge array arranged as a wedge structure on the back side or in front of the back side of the lens array used. Alternatively or additionally, the optical function can be realized by a grating or a diffractive optical element or a holographic optical element.

[0011] When using a lens array with an additionally placed or integrated wedge array, the edge area of ​​the transmission light spot can be deflected by a matching wedge angle or grating, so that the aperture of the objective lens is no longer irradiated by the light spot or beam. The light spot is turned in such a way that it can still pass through the area of ​​the objective lens that allows light to pass. After passing through the objective lens, the light spot areas affected by the wedge array or diffractive optical element and those not affected by the wedge array or diffractive optics can overlap immediately. However, in the target distance of the area to be detected or the scanning area, these light spot areas accurately form the desired beam diameter again. As a result, the full field angle of the objective lens can be used to scan the scanning area without a light spot segment on the transmission side. In particular, more effective and full utilization of the transmission power can be achieved. Alternatively or additionally, the transmission light spot can also be guided out of the objective lens at an angle offset relative to the optical axis. As a result, the desired light spot position can be reached again in the set target distance, wherein beam overlap is avoided at the same time.

[0012] The optical device can preferably be used in a lidar device on the transmitting side and / or on the receiving side.

[0013] Preferably, a combination of a lens array and a wedge array of the optical device can be used to optimize the aberration characteristics of the optical device. For this purpose, for example, the microlenses of the lens array can be rotated relative to the wedge elements of the wedge array, or the wedge elements can be arranged behind the microlenses in the emission direction of the beam. Despite these measures, the emission angle of the generated beam can remain essentially unchanged.

[0014] According to one embodiment, the wedge array is designed as a diffractive optical element or holographic optical element, which is applied to the lens array at least on one side or is arranged in the beam path of the beam at a distance from the lens array. This measure can be used to prevent light spot segments both on the transmission side and on the reception side. Such an optical function can be realized, for example, with the aid of a diffractive optical device. Instead of an optical or conventional wedge array, a grating array can be used, which deflects the transmission beam or the reception beam to the desired angle.

[0015] According to another embodiment, the wedge elements of the wedge array have a triangular cross section with an inclined face and a flat face, wherein the flat face of the wedge element faces the flat face of the microlens. If the wedge element is arranged behind the microlens in the emission direction of the beam from a lidar device having such an optical arrangement, particularly advantageous aberration characteristics of the optical arrangement can be achieved. Therefore, the generated beam must pass through the microlens in a first step and can then be additionally corrected or deflected by the wedge element. As a result, the aberrations of the optical arrangement can be minimized.

[0016] At least one face of the wedge array is preferably oriented radially away from the axis of symmetry and away from the lens or lens array. As a result, the wedge array can be directly aligned with the incoming beam. The incoming beam can be a beam generated by the transmission unit or a beam reflected or backscattered in the scanning area.

[0017] According to a further embodiment, at least one wedge element has a height that is equal to the height of at least one microlens or is smaller than the height of at least one microlens. As a result, a portion of the beams that expose the microlenses can be deflected or all beams can be deflected via the respective wedge element. This results in, among other things, greater flexibility and design freedom in the construction of the optical arrangement.

[0018] The height of the corresponding wedge structure or wedge element can correspond to the used pitch of the microlenses. Depending on the embodiment of the optical device, this height can be configured in particular to be constant or variably along the extension of the wedge array. Since the angle of incidence of the signal becomes steeper depending on the distance to the optical axis, the wedge angle must be adapted accordingly. As the distance to the optical axis becomes greater, the distance between the wedges or faces also increases. Advantageously, the entire structure can be designed to be radially symmetrical with respect to the optical axis or the axis of symmetry.

[0019] According to another embodiment, the wedge array is spaced apart from the lens array in the radiation direction or connected to the lens array. In addition to the configuration of the wedge-shaped segments or surfaces, the influence of the optical element on the radiation can thus also be adapted by the distance to the lens. The separate optical element can be configured in particular as a retrofit solution and can be installed in an already operating lidar device as a supplement.

[0020] According to another embodiment, the wedge array is integrally formed with the lens array. Alternatively, the wedge array can be connected to the lens array in a material-locking manner. In particular, the wedge array or the wedge element can be applied to the back side of the lens array so that the usually flat surface of the lens array is formed as a wedge array. Thus, a compact array or optical element equipped with optical functions on both sides can be provided, which can be optimally matched to the field of view of the objective.

[0021] According to another embodiment, at least one microlens of the lens array is tilted at a rotation angle relative to at least one wedge element of the wedge array. As a result, the beam deflected by the wedge element can impinge on the flat surface of the corresponding microlens at right angles, thereby, in particular, minimizing the occurrence of aberrations. Preferably, a wedge element can be assigned to each microlens. Thus, an optical element with an equal number of microlenses and wedge elements can be provided.

[0022] According to an advantageous embodiment, each microlens of the lens array has an independent rotation angle. This makes it possible to achieve an arrangement in which the angle of exit of the beam through the objective into the scanning area corresponds to the angle without the wedge element. The exit angle of the beam is therefore not affected by the use of a wedge array.

[0023] In order to align the respective focal points of the microlenses with the focal plane of the objective despite the rotation of the individual microlens elements, a concave design of the entire lens array or of the microlens array is advantageous. This minimizes the space required between the objective and the wedge array and the microlens array.

[0024] According to a further embodiment, the rotation angle of at least one microlens corresponds to the deflection angle of at least one wedge element, which is assigned to the respective at least one microlens. The rotation angle of at least one microlens can preferably be varied for each individual microlens element and depends on the radial spacing to the optical axis. With increasing radial spacing to the optical axis, the rotation angle and the deflection angle can be selected to be larger, for example. The exit angle of the beam can be varied by the selected rotation center or the optical axis in the focal plane of the objective.

[0025] Preferably, the optical device can be used in automotive lidar systems, in the consumer sector, in the construction industry, in the craftsman sector, in trains, in drones, in industry, such as automation technology, in production environments, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The preferred embodiment of the present invention is described in more detail below based on a highly simplified schematic diagram. The accompanying drawings show:

[0027] Figure 1 A schematic diagram showing a laser radar device according to an embodiment;

[0028] Figure 2 , 3 is a schematic diagram showing a desired transmission spot arrangement and an actual transmission spot arrangement in a target distance in a scanning area;

[0029] Figure 4 shows a detailed view of an optical device according to one embodiment;

[0030] Figure 5 shows a detailed view of an optical device according to another embodiment;

[0031] Figure 6 A cross-sectional view showing a microlens array;

[0032] Figure 7 Shown from Figure 6 and Figure 7 A stereogram of a microlens array;

[0033] Figure 8-17 Schematic diagram showing a microlens with an optical device wedge element. DETAILED DESCRIPTION

[0034] Figure 1 A schematic diagram of a lidar device 1 according to an exemplary embodiment is shown. The lidar device 1 is used to generate a beam 2 and to scan a scanning area A using the beam 2 . The lidar device 1 has a transmission unit 4 which has a laser 6 as a radiation source for generating the beam 2 .

[0035] The generated beam 2 is continuously deflected by a movable mirror 8 of the transmission unit 4 . The movable mirror 8 can be designed as a pivotable micromirror and oscillates periodically, thereby scanning the scanning area A. The mirror 8 is used by the transmission unit 4 together with the reception unit 10 .

[0036] The beam 2 deflected by the mirror 8 is focused or shaped as parallel as possible by a collimator lens 12 and deflected by a deflection mirror 14 transversely to the emission direction of the laser 6. The deflected beam 3 is emitted to an optical device 16 along a first optical axis OA1.

[0037] The optical device 16 has a microlens array 17 and will be described in more detail below. The optical device 16 acts on the beam 3 before it is directed to a beam splitter 18 and a transmission optics 20. The transmission optics 20 serve to emit the beam 3 into a scanning area A.

[0038] According to this exemplary embodiment, the transmitting optical system 20 is designed as a combined transmitting-receiving optical system 20 and is also used by the receiving unit 10. The transmitting-receiving optical system 20 has an objective 22 and an aperture 24. The objective 22 can also be designed as a component of the optical device 16. Depending on the configuration of the lidar device 1, in particular only one optical device 16 can be provided, which can also be used for the generated beam 3 and the received beam 28.

[0039] The backscattered or reflected beam 28 in scanning region A, for example at object 26, is received by transmit-receive optics 20 and directed via beam splitter 18 to optics 16 of receive unit 10. The optics of receive unit 10 and of transmit unit 4 may be of identical or different design.

[0040] After passing through the optical device 16, the beam 28 is directed to a deflection mirror 30. The deflected beam is deflected by the deflection mirror 30 to a second optical axis OA2, wherein the second optical axis OA2 can extend parallel to the first optical axis OA1. The deflected beam 29 is directed again to a detector 34 via a focusing lens 32 and via a pivotable mirror 8.

[0041] By the movement of the mirror 8 and its alternating movement, the transmission beams 2, 3 are scanned by the optical device 16. The divergent transmission beam is then projected onto the transmission-reception optical device 20 by each microlens element of the lens array 17, before the transmission beam is expanded, it can leave the lidar device 1 into the scanning area A. After reflection / scattering at the object 26 located in the field A, the signal 28 passes through the transmission-reception optical device 20 again and is deflected to the detector 34 via the above-mentioned optical elements.

[0042] Figure 2 and Figure 3 A desired transmission spot arrangement and an actual transmission spot arrangement in a target distance in a scanning area A are schematically shown to clarify the problems in the prior art. Figure 2 Three different desired light spot arrangements are shown. Figure 3 Shown in Figure 2 The actual desired light spot arrangement is shown in . An inherent problem of conventional scanner systems is the fact that when scanning on the transmission side at microlens elements remote from the optical axis, different sized areas of the transmission signal are deflected directly into the aperture 24 of the transmission-receiving lens, depending on the design of the extended transmission beam diameter and the spacing of the illuminated microlens elements from the optical axis. This is Figure 4Therefore, the "cut-off" part 36 no longer enters the scanning area A or the objective lens 22 of the transmitting-receiving optical device 20, thereby generating 8 gaps of different sizes in the target distance of the measuring area between adjacent light spots depending on the scanning angle of the mirror 8. Figure 3 The "cut-off" spot is shown on the left.

[0043] This means that the full field angle of the objective 22 used can never be used without generating a light spot segment 36 which is at most half the original diameter.

[0044] Depending on the diameter of the expanded transmission beam 3, the transmission beam 3 is cut off from a certain microlens height about the optical axis OA1 by the aperture 24 of the transmission-receiving optical system 20. The distance of the microlens element 17 to the optical axis OA1 is converted into a deflection angle in the field (field of view angle, abbreviated FoV). The larger the transmission beam diameter, the smaller the field of view angle that has cut off the entire diameter of the transmission spot 3.

[0045] Figure 4 Detailed view of an optical device 16 according to an embodiment is shown. A wedge element 42 of a wedge array 40 is shown here, which is not integrated into a microlens 17 of a microlens array, but is spaced apart from the corresponding microlens 17. For the sake of simplicity, Figure 4 Only one wedge element 42 and one microlens 17 are shown, which are part of the optical device 16. However, the optical device 16 has a plurality of wedge elements 42 and microlenses 17, which are each arranged in an array in a planar manner. In particular, the optical function of the optical device 16 with and without the wedge element 42 is explained. The beam path is represented on the transmission side or on the reception side by the microlens 17 and the downstream objective 22. In particular, the beam path is shown in the comparison between the beam 3 'without the wedge element 42 and the beam 3 with the wedge element 42.

[0046] Not only the part of the signal 3 passing through the microlens 17 , but the entire signal 3 is deflected at an angle in such a way that it does not impinge on the objective aperture 24 .

[0047] The signal 3 is guided on the transmission side to the objective 22 by means of an angular difference through the wedge element 42, whereby the signal impinges on different positions on the objective 22 and not into the objective aperture 24. The angular difference is selected such that the beam or the transmission signal illuminates the same object point at the target distance of the detection space A.

[0048] Therefore, it is also possible for LiDAR device 1 to collect light 28 backscattered from illuminated object point 26 again at exactly the same angle without light spot segment 36 and to deflect light 28 axially parallel to wedge array 40 in the direction of detector 34 .

[0049] Figure 5 A detailed view of an optical device 16 according to another embodiment is shown. Figure 4 Differently, in the case of the optical device 16, the beam is deflected by an angle δ due to the wedge element 42 K , the beam 3 does not strike the microlens 17 parallel to the optical axis OA. This avoids the generation of aberrations, in particular astigmatism. The imaging errors lead to a deterioration in the imaging quality of the emitted beam 3 in the scanning area A, and a defined light spot can no longer be projected when the object distance increases. As a result, the system range and the system angular resolution are significantly reduced.

[0050] In the case of an optical device 16 with a wedge element-microlens combination, the problem of imaging errors can be eliminated by rotating the corresponding microlenses 17. The rotation angle δ of the microlenses 17 is μL The deflection angle δ of the wedge element 42 always corresponds to K The rotation angle δ μL can be varied for each individual wedge element 42 or each individual microlens 17 and depends on the distance to the optical axis OA1 ( Figure 6 ) radial spacing. The beam exit angle δ Obj,MK The angle of departure of the beam 3 with the wedge element 42 is shown for illustration. Obj,MK and the exit angle δ of the beam 3 without the wedge element 42 Obj,OK .

[0051] According to the exemplary embodiment shown, the beams 3 , 3 ′ are guided in a radiation direction Z onto the optical device 16 .

[0052] Figure 6 and Figure 7 1 shows a diagram of a microlens array 27. In order to be able to place the corresponding focal point on the focal plane of the objective lens 22 despite the rotation of the individual microlenses 17, a concave structural form of the entire microlens array 27 is necessary. As a result, the distance between the objective lens 22 and the microlens array 27 can be minimized. In order to illustrate the curvature of the microlens array 27, Figure 7 The microlens 27 is not shown.

[0053] Depending on the distance from the optical axis OA1 in the x-direction and / or the y-direction, the corresponding microlenses 27 have different rotation angles δ μL . Rotation angle δ μL In particular, it can be chosen to be larger as the distance increases.

[0054] Figures 8 to 17A schematic diagram of a microlens 17 with corresponding wedge elements 42 of an optical device 16 is shown. In particular, different structural forms of the combination of individual elements are shown.

[0055] Figure 8 , 10 , 12, and 14 show the following structural form: in the structural form, first the wedge element 42 and then the microlens 17 are connected behind in the beam direction Z. In this case, the wedge element 42 can be spaced apart from the corresponding microlens 17 or can be connected to the corresponding microlens 17 in an integral manner. Since the beam deflected by the wedge element 42 impinges obliquely on the flat surface 44 of the microlens 17, aberrations may occur, because the beam deflection angle δ by the wedge element 40 only occurs after the microlens 17. K .

[0056] Fig. 9 , 11 , 13, 15 relative to Figure 8 , 10 , 12, and 14 show a mirror-inverted arrangement of microlenses 17 and wedge elements 42. Thus, the microlenses 17 are arranged first and the wedge elements 42 are then arranged in the radiation direction Z. The microlenses 17 are arranged in such a way that the flat surface 44 faces away from the beam incident from the radiation direction Z. As a result, for each microlens 17, the incident beam 3 can be kept parallel to the optical axis OA. This can be achieved without rotating the corresponding microlens 17. Since the microlens array 27 can be implemented flat or plate-shaped in this way, standard components can be used.

[0057] exist Fig.16 and 17 In the embodiment, the microlens 17 and the wedge element 42 are similar to Figure 8 , 10 , 12, 14 are arranged, but the microlens 17 is provided to be rotated relative to the wedge element 42, thereby minimizing the structural space requirement and the occurrence of imaging errors.

Claims

1. An optical device (16), comprising a lens array (27) having a plurality of microlenses (17) and an objective lens (22), the lens array comprising a plurality of microlenses (17), the objective lens being used to deflect a beam (3) from a scanning area (A) or to deflect the beam (3) into the scanning area (A), wherein: The objective lens (22) is arranged in the beam path between the scanning area (A) and the lens array (17), characterized in that the device (16) has at least one wedge array (40), which is arranged in the radiation direction (Z) before or after the lens array (17) and has a plurality of wedge elements (42), wherein the number of the wedge elements (42) is equal to the number of the microlenses (17), wherein the entire lens array (27) has a concave structural form and each microlens (17) of the lens array (27) has its own rotation angle (δ μL ), wherein the rotation angle (δ μL ) corresponds to a deflection angle (δ) of the at least one wedge element (42) K ), the at least one wedge element being assigned to the corresponding microlens (17).

2. The device according to claim 1, wherein: The wedge array (40) is designed as a diffractive optical element or a holographic optical element which is applied to the lens array (27) at least on one side or is arranged spaced apart from the lens array (27) in the beam path of the beam (3).

3. The device according to claim 1 or 2, wherein: The wedge elements (42) of the wedge array (40) have a triangular cross section having an inclined surface and a flat surface, wherein the flat surface of at least one wedge element (42) faces the flat surface (44) of the at least one microlens (17).

4. The device according to claim 3, wherein: The at least one wedge element (42) has a height that is equal to or smaller than a height of the at least one microlens (17).

5. The device according to claim 1 or 2, wherein: The wedge array (40) is spaced apart from the lens array (27) in the radiation direction (Z) or is connected to the lens array (27).

6. The device according to claim 1 or 2, wherein: The wedge array (40) is integrally configured with the lens array (27).

7. The device according to claim 1 or 2, wherein: At least one microlens (17) of the lens array (27) is tilted relative to at least one wedge element (42) of the wedge array (40) by a rotation angle (δ μL ).

8. The device according to claim 1, wherein: The optical device is used in a laser radar device (1).

9. A laser radar device (1), which is used to scan a scanning area (A) by means of a beam, and has a transmitting unit (4) and a receiving unit (10), wherein the transmitting unit is used to generate a beam (2) and to deflect the beam (3) along the scanning area (A), and the receiving unit has at least one detector (34) for receiving a reflected beam (28), characterized in that The transmitting unit (4) and / or the receiving unit (10) has an optical device (16) according to any one of the preceding claims.

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