LASER SCANNER FOR SCANNING AN ENVIRONMENT AROUND ONE AXIS

Description

[0001] The present invention relates to a laser scanner for scanning an environment around an axis, which comprises a base with a laser transmitter for emitting a transmission beam, a laser receiver for receiving the transmission beam reflected from the environment as a reception beam, a common rotating mirror inclined to the axis for the transmission and reception beams, and a motor for rotating the rotating mirror around the axis, an annular window carried by the base and arranged around the rotating mirror for the passage of the transmission and reception beams, and a head carried away from the annular window facing away from the base, which head contains a first deflection for the transmission beam aligned with the rotating mirror and a second deflection for the reception beam aligned with the rotating mirror.

[0002] Such laser scanners for environmental detection are used as so-called "all-round scanners" in a variety of applications, particularly for scanning buildings, tunnels, mines, etc., and can be used either stationary, e.g., on a tripod, or mobile, e.g., mounted on a vehicle. The laser transmitter in the base emits a pulsed or modulated transmission beam, which is deflected by the first deflection in the head onto the rotating mirror. As it rotates, the rotating mirror fans out the transmission beam rotationally symmetrically around its axis into the shape of a scanning disk or cone, which is used to scan the environment to be measured through the annular window. The received beam, reflected back from the environment, is deflected by the rotating mirror and the second deflection in the head toward the base to the receiver.Based on time-of-flight measurements of the receiving beam reflected from the surroundings, distance measurement points are determined in a known manner, and from these and the respectively assigned rotating mirror alignment, a scanning point cloud (a "3D model") of the environment is created in a coordinate system. Laser scanners are known, for example, from US 2008 / 0316463 A1 and from EP 2 293 013 A2.

[0003] Since all electrically powered ("active") components of the laser scanner, such as the laser transmitter, laser receiver, motor, and electronics, are housed in the base, and only "passive" mechanical and optical components are located in the head, a compact design with short cable runs is achieved. However, this requires the transmit and receive beams between the base and head to cross the beam path of the scanning disk or cone, respectively, which requires the transmit and receive beams to travel a clear distance in this area. To avoid losses, it is necessary to precisely align the head and base during assembly of the laser scanner so that the transmit beam emitted by the laser transmitter precisely hits the first deflection point, and the receive beam deflected by the second deflection point precisely hits the receiver. Such alignment is extremely complex and requires the intervention of specialist personnel. If, for example, a misalignment occurs during operation,If vibrations cause a slight twisting or displacement of the head relative to the base and thus a misalignment of the transmit and receive beams, a complex realignment is required.

[0004] The invention aims to create a compact laser scanner that is easy to assemble and robust in operation.

[0005] This aim is achieved with a laser scanner of the type mentioned in the introduction, which is characterized according to the invention in that a flexible first optical fiber is connected to the laser transmitter and a flexible second optical fiber is connected to the laser receiver, wherein the head carries a first mount for the output of the flexible first light guide and a second mount for the input of the flexible second light guide, and wherein the first mount rigidly aligns the output with the first deflection and the second mount rigidly aligns the input with the second deflection.

[0006] The invention breaks with the paradigm that the space extending between the base and head of the laser scanner around the rotating mirror must be kept free of any components. However, thick, electrically conductive cables are avoided: only two thin, flexible fiber optic cables are routed through this space. The inventors also recognized for the first time that these flexible fiber optic cables have little or no impact on the results of scanning the environment, due to the vibrations of the laser scanner, which can never be completely eliminated during stationary operation, and even more so during mobile operation on a vehicle exposed to constant movement and vibration.Conversely, the flexibility of the light guides means that precise alignment of the head relative to the base is not necessary, which significantly simplifies assembly of the laser scanner and also makes it robust against any vibrations or similar that may occur during operation. In their mounted positions, the ends of the light guides on the head side are rigidly connected to the holders. d.h. fixed and in the desired position, aligned with the respective deflection point. Thus, the first fiber optic cable guides the transmitted beam from the connected laser transmitter to the first deflection point with almost no loss, and the second fiber optic cable guides the received beam from the second deflection point to the receiver with almost no loss, regardless of the relative position of the head to the base.

[0007] As a result, the flexibility of the fiber optics enables simple and quick assembly and greater robustness of the laser scanner without the need for complex alignment of the head and base. Due to the rigid alignment of the head ends of the fiber optics in the mounts, misalignment is permanently eliminated by design.

[0008] In a preferred embodiment, the first deflection is designed to direct the transmitted beam parallel to the axis onto the rotating mirror, and the second deflection is designed to receive the received beam parallel to the axis from the rotating mirror. The axis-parallel transmitted beam forms the same angle with the rotating mirror throughout its entire rotation, so that the surroundings are scanned evenly. Likewise, the laser receiver receives the received beam via the rotating mirror from the direction of the transmitted beam and is thus directed at the currently scanned point in the surroundings.

[0009] It is advantageous if the first deflection comprises a first fixed mirror arranged upstream of the rotating mirror in the beam path of the transmitted beam, and the second deflection comprises a second fixed mirror arranged downstream of the rotating mirror in the beam path of the received beam, wherein the two fixed mirrors are each inclined at 45° to the axis in opposite directions. Due to the opposite inclination of the two fixed mirrors to the axis, the beam paths of the transmitted beam upstream of the first fixed mirror and the received beam downstream of the second fixed mirror run diametrically opposite one another when viewed from the axis. Consequently, the transmit and receive channels can be relatively far apart from each other both in the head and in the base, which reduces mutual influence between the laser transmitter and laser receiver and facilitates their space-saving arrangement in the base.In addition, the beam paths of the transmit and receive beams can be accommodated in the head of the laser scanner in a space-saving manner, so that the head can be built small.

[0010] It is particularly advantageous if the second fixed mirror has an axially centered opening in which the first fixed mirror is located. This places the two fixed mirrors at the same axial height, further reducing the axial space required for the beam paths and enabling a particularly small head. Furthermore, the axially centered first fixed mirror allows the transmitted beam to be directed onto the rotating mirror, allowing the surrounding area to be scanned particularly evenly with the scanning disk or scanning cone—depending on the rotating mirror's inclination.

[0011] To collimate the transmitted beam downstream of the first optical fiber, the first deflection preferably comprises collimating optics in the beam path of the transmitted beam. The collimating optics reduce the divergence of the transmitted beam, allowing the surroundings to be scanned with particularly small sampling points and thus with precision. In embodiments with a first fixed mirror, this collimating optics is advantageously arranged in the beam path of the transmitted beam between the first mount and the first fixed mirror in order to minimize the axial space requirement of the first deflection and to space the collimating optics from the received beam.

[0012] For particularly low-loss coupling of the received beam into the second optical fiber, the second deflection preferably comprises a focusing optic in the beam path of the received beam, e.g. one or more converging lenses, spherical lenses, etc. In embodiments with a second fixed mirror, this focusing optic is advantageously arranged in the beam path of the received beam between the second fixed mirror and the second holder in order to keep the axial space requirement of the second deflection particularly low and to space the focusing optic from the transmitted beam.

[0013] It is advantageous if the second deflection comprises at least one third fixed mirror arranged downstream of the focusing optics in the beam path of the received beam for axially normal folding of the received beam. The third fixed mirror extends the path of the received beam between the focusing optics and the input of the second optical fiber through folding. This allows the received beam to exhibit low convergence and, at a small coupling angle, be coupled into the input with low loss, entirely within an acceptance angle of the input. Conversely, this allows the use of a second optical fiber with a smaller acceptance angle. Since the received beam is guided in the axially normal plane, the axial space requirement is kept to a minimum.

[0014] In an advantageous embodiment, the first mount aligns the output parallel to the axis toward a fourth fixed mirror of the first deflection, which is inclined at 45° to the axis. In this way, the first optical fiber can run without bending, for example, approximately parallel to the axis from the base to the first mount, and the transmitted beam can have an at least approximately axially normal, space-saving beam path after the fourth fixed mirror.

[0015] Similarly, in another advantageous embodiment, the second mount aligns the input parallel to the axis to a fifth fixed mirror of the second deflection device, which is inclined at 45° to the axis. This allows the second optical fiber to run bend-free, for example, approximately parallel to the axis, from the second mount to the laser receiver.

[0016] The ring window can have different cross-sectional shapes, e.g. the shape of an ellipse, a regular or irregular polygon, etc. The ring window preferably has the shape of a circular ring concentric with the axis in order to achieve a radial exit of the transmitted beam and entry of the received beam that is always normal to the ring window.

[0017] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the accompanying drawings. In the drawings: Fig. 1 an embodiment of a laser scanner according to the invention in a schematic longitudinal section; Fig. 2 the laser scanner from Fig. 1 in a schematic cross-section along a section line I - I; and Fig. 3 an alternative embodiment of a head of the laser scanner of Fig. 1 in a schematic longitudinal section.

[0018] Fig. 1 shows a laser scanner 1 scanning an environment 2. For stationary scanning of the environment 2, the laser scanner 1 is mounted on a tripod or the like; for mobile scanning of the environment 2, the laser scanner 1 is alternatively mounted on a vehicle, e.g., a land vehicle or aircraft.

[0019] The laser scanner 1 has a base 3, which contains the active, i.e., the electrically powered, components of the laser scanner 1, and a head 4, which is offset from the base 3 along an axis A and contains only passive, i.e., non-electrically powered, optical and mechanical components of the laser scanner 1. The base 3 has a cylindrical housing 5, for example, and therein electro-optical components of the laser scanner 1, in particular a laser transmitter 6, which emits a pulsed or modulated transmitted beam 7, and a laser receiver 8, which receives a reflection of the transmitted beam 7 from the environment 2 as a received beam 9. The base 3 further has a common rotating mirror 10, which is inclined relative to the axis A and is arranged in an axial section B between the housing 5 of the base 3 and the head 4.The rotating mirror 10 is rotated about the axis A via a shaft 11 by a motor 12 of the base 3 arranged in the housing 5, so that the transmission beams 7 are fanned out and emitted in successive directions R around the axis A in a disc-like or conical manner at the mirror surface 10' of the rotating mirror 10, and the reception beams 9 reflected at scanning points 13 of the environment 2 are received via the rotating mirror 10.

[0020] In the axial section B, the base 3 carries a window arranged around the rotating mirror 10, i.e. an annular window 14, for the passage of the transmitting and receiving beams 7, 9. The annular window 14 serves to protect the rotating mirror 10 and the head and base components and to support the head 4 on the base 3. The base 3, the annular window 14 and the head 4 can be connected to each other in many ways, z.B. screwed into or together, clamped into each other, locked together, bayonet-like coupled, etc. or simply stacked on top of each other.

[0021] The head 4 also has a cylindrical housing 15, for example. The housing 15 contains a first deflection 16, which is aligned with the rotating mirror 10 and thus deflects the transmission beam 7 emitted by the laser transmitter 6 toward the rotating mirror 10. The housing 15 further contains a second deflection 17, which is also aligned with the rotating mirror 10 and thus deflects the reception beam 9 received via the rotating mirror 10 toward the laser receiver 8.

[0022] In the laser scanner 1, two flexible light guides 18, 19 are guided through section B, either within the ring window 14 ( Fig. 1 ), outside of it or through the ring window 14 (not shown), and in associated holders 20, 21 ( Fig. 2 ) is held on the head 4. The first light guide 18 is connected to the laser transmitter 6, runs from the laser transmitter 6 to the first holder 20, and thus guides the transmitted beam 7 from the base 3 to the head 4. The second light guide 19 runs from the second holder 21 to the laser receiver 8, to which it is connected, and thus guides the received beam 9 from the head 4 to the base 3.

[0023] The light guides 18, 19 are, for example, optical fibers, e.g., glass fibers made of quartz glass or plastic, or liquid-core fibers. They optionally have a diameter that is smaller than that of the transmitted beam 7 in order to be able to measure the environment 2 even where one of the light guides 18, 19 is located in the beam path. For example, the light guides 18, 19 can each have a diameter of less than 1 mm. In particular, the first light guide 18 can be a single-mode fiber and the second light guide 19 a multi-mode fiber. If the laser transmitter 6 is optionally a fiber laser, the first light guide 18 can be formed integrally therewith.

[0024] The light guides 18, 19 are fixed in a predefined position, ie rigidly aligned, on the holders 20, 21, which are, for example, socket or plug holders, e.g., fiber optic connectors, and can optionally be released again if required.

[0025] In the Fig. 1 - 3 In the fixed position shown, the first holder 20 rigidly aligns the output 22 of the first light guide 18 with the first deflection 16 and the second holder 20 rigidly aligns the input 23 of the second light guide 19 with the second deflection 17.

[0026] In this embodiment, when the laser transmitter 6 emits the transmitted beam 7, it passes through an input 24 into the first optical fiber 18 and via the first optical fiber 18 to the head 4, where the output 22, due to its rigid orientation, directs the transmitted beam 7 to the first deflector 16. The first deflector 16 then deflects the transmitted beam 7 onto the mirror surface 10' of the rotating mirror 10, which deflects the transmitted beam 7 through the annular window 14 to the current scanning point 13 of the environment 2, which depends on the respective rotational position of the rotating mirror 10. As a result of the rotation of the rotating mirror 10, the environment 2 is scanned scanning point 13 by scanning point 13. At the scanning point 13, the transmission beam 7 is reflected and coupled as a reception beam 9 through the ring window 14, via the rotating mirror 10 and the second deflection 17 into the rigidly aligned input 23 of the second optical fiber 19.The receiving beam 9 is then guided by the second optical fiber 19 to the laser receiver 8 and there finally converted into receiving signals. d.h. received.

[0027] An electronics unit 26 integrated into or connected to the laser scanner 1 controls the laser scanner 1 and evaluates received signals from the laser receiver 8 in order to determine the travel time of the transmitted and received beams 7, 9. The electronics unit 26 optionally controls the rotational movement of the motor 12 or the rotating mirror 10. From the determined travel time, the electronics unit 26 can determine the distance from the laser scanner 1 to the scanning point 13 and, from the respective rotational position of the rotating mirror 10 when transmitting the transmitted beam 7, the direction of the scanning point 13 from the perspective of the laser scanner 1, as is known in the prior art. From this, either the electronics unit 26 or a separate computing unit can calculate the position of the scanning point 13 relative to the laser scanner 1 and, in a known manner, create a 3D point cloud or a 3D map from a large number of scanning points and, if applicable, the position and orientation of the laser scanner 1 in the environment 2.create a 3D model of environment 2.

[0028] Each of the deflectors 16, 17 can be configured in various ways to deflect the transmitted or received beam 7, 9, e.g., comprising one or more optical elements such as mirrors, prisms, lenses, etc., and can be aligned at different angles to the rotating mirror 10 and the mounts 20, 21. Likewise, each mount 20, 21 and the rotating mirror 10 can have different orientations.

[0029] In the example of Fig. 1 and 2 the first deflection 16 directs the transmission beam 7 parallel to the axis A (here: along the axis A) onto the rotating mirror 10 and the second deflection 17 receives the reception beam 9 from the rotating mirror 10 also parallel to the axis A; in the example shown, the transmission and reception beams 7, 9 each run along the axis A and are thus coaxial in this area.

[0030] In the illustrated embodiment, an angle α, which the transmitted beam 7 forms with the axis A upon leaving the rotating mirror 10, is 90°, since the rotating mirror 10 is inclined here by an angle β of 45° to the axis A. The environment 2 is thus scanned in a plane, i.e., in a disk shape. Alternatively, the first deflection 16, the second deflection 17, and / or the rotating mirror 10 can have a different inclination to the axis A, resulting in a different scanning shape, e.g., conical, etc.

[0031] According to the Fig. 1 and 2the first deflection 16 in the beam path of the transmitted beam 7 optionally has a first fixed mirror 27, which is inclined by an angle γ (here: 45°) to the axis A and directs the transmitted beam 7 onto the rotating mirror 10. Furthermore, the second deflection 17 in the beam path of the received beam 9 has a second fixed mirror 28, which is optionally inclined opposite to the first fixed mirror 27 by an angle δ (here: 45°) to the axis A, which is opposite to the angle γ, and directs the received beam 9 to the input 23 of the second optical fiber 19. As in Fig. 2 As shown, the transmitting beam 7 and the receiving beam 9 are therefore diametrically opposite each other in the head 4 with respect to the fixed mirrors 27, 28, whereby the laser transmitters and receivers 6, 8 can also be diametrically opposite each other in the base 3.

[0032] In the example of Fig. 1 and 2The fixed mirrors 27, 28 are optionally nested within each other to save space. For this purpose, the second fixed mirror 28 has an axially central opening 29 in which the first fixed mirror 27 is arranged. Alternatively, the two fixed mirrors 27, 28 could be arranged side by side, as seen in the direction of axis A, or one above the other along axis A in order to guide the transmit and receive beams 7, 9 on different axially normal planes (not shown).

[0033] In the embodiment of the Fig. 1 and 2 The first deflection device 16 has an optional collimation optics 30 in the beam path of the transmitted beam 7 for its collimation. The collimation optics 30 are arranged between the first holder 20 and the rotating mirror 10, i.e. in the direction of the transmitted beam 7 from (as here) or after the optional first fixed mirror 27.

[0034] To adapt the receiving beam 9 to the numerical aperture of the second light guide 19, the second deflection 17 in the example of Fig. 1 and 2 an optional focusing optics 31 (here: in the form of a single converging lens) in the beam path of the receiving beam 9. This is arranged between the rotating mirror 10 of the second holder 21, i.e. in the direction of the receiving beam 9 before or (as here) after the optional second fixed mirror 28.

[0035] Optionally, the receiving beam 9 is further folded before the entrance 23 of the second optical fiber 19. For this purpose, the second deflection 17 has at least a third fixed mirror 32, which is arranged downstream of the focusing optics 31 in the beam path of the receiving beam 9 and z.B. folds in a plane normal to axis A ( Fig. 2 ).

[0036] Fig. 3 shows a further embodiment of the head 4 of the laser scanner 1 with a different position of the holders 20, 21 and the light guides 18, 19 to avoid bending of the light guides 18, 19. The same reference numerals designate the same elements as in the example of Fig. 1 and 2 .

[0037] On the transmission side, in this embodiment, the first deflection device 16 has a fourth fixed mirror 33 inclined at 45° to the axis A, which deflects the transmission beam 7 received from the output 22 of the first optical fiber 19 toward the optional first fixed mirror 27. The first holder 16 aligns the output 22 parallel to the axis A onto the fourth fixed mirror 33, and the first optical fiber 18 extends essentially parallel to the axis.

[0038] Alternatively or in addition, in the example of Fig. 3The second deflection 17 has a fifth fixed mirror 34 inclined at 45° to the axis A, which deflects the reception beam 9 received here from the optional second fixed mirror 28 towards the input 23. The second holder 17 aligns the input 23 parallel to the axis A to the fifth fixed mirror 34, and the second light guide 19 also runs essentially parallel to the axis.

[0039] The invention is not limited to the embodiments shown, but includes all variants, modifications and combinations thereof that fall within the scope of the appended claims.

Claims

1. A laser scanner for scanning an environment (2) about an axis (A), comprising a base (3) with a laser transmitter (6) for transmitting a transmission beam (7), a laser receiver (8) for receiving the transmission beam (7) reflected from the environment as a reception beam (9), a shared rotating mirror (10) for the transmission and reception beams (7, 9), which is inclined towards the axis (A), and a motor (12) for rotating the rotating mirror (10) about the axis (A); an annular window (14) for the passage of the transmitting and reception beams (7, 9), which is supported by the base (3) and arranged all around the rotating mirror (10); and a head (4), which is supported by the annular window (14) so that it is facing away from the base and which contains a first deflector (16) for the transmission beam (7), said first deflector being directed towards the rotating mirror (10) and a second deflector (17) for the reception beam (9), said second deflector being directed towards the rotating mirror (10); wherein a flexible first light guide (18) is connected to the laser transmitter (6) and a flexible second light guide (19) is connected to the laser receiver (8), wherein the head (3) supports a first support (20) for the outlet (22) of the flexible first light guide (18) and a second support (21) for the inlet (23) of the flexible second light guide (19), and wherein the first support (20) rigidly directs the outlet (22) towards the first deflector (16) and the second support (21) rigidly directs the inlet (23) towards the second deflector (17).

2. The laser scanner according to claim 1, characterized in that the first deflector (16) is configured to direct the transmission beam (7) parallel to the axis (A) towards the rotating mirror (10), and the second deflector (17) is configured to receive the reception beam (9) parallel to the axis (A) from the rotating mirror (10).

3. The laser scanner according to claim 1 or 2, characterized in that the first deflector (16) comprises a first fixed mirror (27) which is arranged upstream of the rotating mirror (10) in the beam path of the transmission beam (7) and the second deflector (17) comprises a second fixed mirror (28) which is arranged downstream of the rotating mirror (10) in the beam path of the reception beam (9), wherein the two fixed mirrors (27, 28) are each inclined in opposing directions by 45° with respect to the axis (A).

4. The laser scanner according to claim 3, characterized in that the second fixed mirror (28) has an axis-centred opening (29) in which the first fixed mirror (27) is arranged.

5. The laser scanner according to any one of claims 1 to 4, characterized in that the first deflector (16) comprises a collimation optics (30) in the beam path of the transmission beam (7).

6. The laser scanner according to claims 3 and 5, characterized in that the collimation optics (30) is arranged in the beam path of the transmission beam (7) between the first support (20) and the first fixed mirror (27).

7. The laser scanner according to any one of claims 1 to 6, characterized in that the second deflector (17) comprises a focussing optics (31) in the beam path of the reception beam (9).

8. The laser scanner according to claims 3 and 7, characterized in that the focussing optics (31) is arranged in the beam path of the reception beam (9) between the second fixed mirror (28) and the second support (21).

9. The laser scanner according to claim 7 or 8, characterized in that the second deflector (17) comprises at least one third fixed mirror (32) arranged downstream of the focussing optics (31) in the beam path of the reception beam (9) for axial-normal folding of the reception beam (9).

10. The laser scanner according to any one of claims 1 to 9, characterized in that the first support (20) directs the outlet (22) parallel to the axis (A) towards a fourth fixed mirror (33) of the first deflector (16), said fourth fixed mirror being inclined at 45° with respect to the axis.

11. The laser scanner according to any one of claims 1 to 10, characterized in that the second support (21) directs the input (23) parallel to the axis (A) towards a fifth fixed mirror (34) of the second deflector (17), said fifth fixed mirror being inclined at 45° with respect to the axis (A).

12. The laser scanner according to any one of claims 1 to 11, characterized in that the annular window (14) has the shape of a circular ring which is concentric to the axis (A).