Optical beam steering device, method for performing beam steering and optical detection system

Abstract

The present disclosure relates to an optical beam steering device (8) for an optical detection system (10), wherein the beam steering device (8) comprises a mirror device (4) and a prism device arranged in an optical path of an optical signal, wherein the mirror device (4) comprises at least one mirror (SF1, SF2), which is configured to deflect the optical signal, and wherein the mirror device (4) is configured to perform a first rotating movement, wherein the prism device comprises at least one prism (5, 6), which is configured to rotate the optical signal, and wherein the prism device is configured to perform a second rotating movement, wherein the optical signal comprises an optical transmit signal (L1) and / or an optical receive signal (L2), wherein the mirror device (4) and the prism device are optically coupled, thereby causing the optical transmit signal (L1) to perform a scanning movement in a scan area (12) and / or thereby capturing the optical receive signal (L2) reflected from the scan area (12), the optical transmit signal (L1) having performed a scanning movement. The disclosure further relates to an optical detection system (10) comprising the optical beam steering device (8), the use of the optical beam steering device in the optical detection system (10) and a method for performing beam steering of an optical signal.

Description

[0001] OPTICAL BEAM STEERING DEVICE, METHOD FOR PERFORMING BEAM STEERING AND OPTICAL DETECTION SYSTEM

[0002] Field

[0003] The present disclosure relates to the field of optical beam steering devices for optical detection systems, in particular lidar systems, and to optical detection systems in particular for vehicles. Beam steering devices may comprise light deflecting arrangements to change the direction of an optical signal.

[0004] Background

[0005] Modern vehicles like cars, vans, trucks, motorcycles, etc. may comprise sensor systems, whose data are used for driver information and / or are used by driver assistance systems.

[0006] Sensor systems are constantly being developed for various functions, e. g. for the acquisition of environmental information in the near and far range of vehicles, such as passenger cars or commercial vehicles. Based on the acquired data, a model of the vehicle environment may be generated and a reaction to changes in this vehicle environment is possible. Sensor systems may also serve as sensors for driver assistance systems, in particular assistance systems for autonomous or semi-autonomous vehicle control. They may for example be used to detect obstacles and / or other road users in the front, rear, or blind spot areas of a vehicle. Sensor systems may be based on different sensor principles, such as radar, ultrasound, optics.

[0007] An important optical sensor principle for environment detection, e. g. of vehicles, is the lidar technology (lidar: light detection and ranging). A lidar system comprises an optical transmission device and an optical reception device. The transmission device emits an optical signal, which can be continuous or pulsed. The optical signal may also be modulated. Electromagnetic waves in the form of laser beams in the ultraviolet, visual or infrared range may be used as optical signals in a lidar system. The light of the optical signal is received by the optical reception device after reflection from an object in a detection area of the lidar system. The optical signal can for example be evaluated according to a time-of-flight method and the spatial position and distance of the object on which the reflection occurred can be determined. In addition, it may be possible to determine a relative velocity. Reflection or reflected light is understood to mean any light that is reflected back and should also include, in particular, light that is reflected back by scattering or absorption emission.

[0008] Scanning lidar systems emit optical signals that move in a scanning direction within a scan area. The scanning movement may be achieved by steering the light beam of the optical signal using an optical light deflecting arrangement which may also be referred to as a beam steering device. The optical light deflecting arrangement of an optical detection system like a lidar system may be configured to direct or steer the emitted and / or received optical signals. The light deflection may for example be effected using one or more mirrors. In scanning lidar systems the optical light deflecting arrangement may serve to direct the light beam sequentially over the scan area.

[0009] In US20220342044A1 a lidar system is described which comprises an oscillating mirror and an oscillating prism. The oscillation of both, the prism and the mirror is controlled to steer one or more light beams both vertically and horizontally to perform a scan of the field-of-view.

[0010] In US20200158829A1 a lidar system is described that uses a combination of a rotating polygonal mirror and a rotatable prism to scan an area of an object. The polygonal mirror and the prism are rotated in combination to generate a scanning pattern.

[0011] Summary

[0012] An optical beam steering device for an optical detection system comprises a mirror device and a prism device arranged in an optical path of an optical signal. The optical signal comprises an optical transmit signal and / or an optical receive signal. The optical path comprises a transmit path, where the optical transmit signal travels towards the scan area and a receive path, where the optical receive signal travels from the scan area. The optical transmit signal becomes the optical receive signal after reflection in the scan area.

[0013] The optical detection system may comprise a lidar system, wherein the optical transmit signal is transmitted by an optical transmission device of the lidar system and the optical receive signal is received by an optical reception device of the lidar system.

[0014] The mirror device comprises at least one mirror, which is configured to deflect the optical signal. The mirror device may be configured to deflect the optical transmit signal and / or the optical receive signal. The mirror device is configured to perform a first rotating movement. The prism device comprises at least one prism, which is configured to rotate the optical signal. The prism device may be configured to rotate the optical transmit signal and / or the optical receive signal. The prism device is configured to perform a second rotating movement.

[0015] The mirror device and the prism device are optically coupled such, that the optical transmit signal travelling on the optical transmit path is caused to perform a scanning movement in a scan area. Alternatively or additionally, the mirror device and the prism device are optically coupled such, that the optical receive signal reflected from the scan area travelling on the optical receive path is captured, the associated optical transmit signal having performed a scanning movement in the scan area. The association of the optical receive signal with the optical transmit signal is formed by the reflection in the scan area.

[0016] A method for performing beam steering of an optical signal using the described optical beam steering device comprises:

[0017] • the prism of the prism device rotating the optical signal,

[0018] • the at least one mirror of the mirror device deflecting the optical signal,

[0019] • wherein the mirror device and the prism device are optically coupled, o thereby causing the optical transmit signal to perform a scanning movement in a scan area and / or o thereby capturing the optical receive signal reflected from the scan area, the optical transmit signal having performed the scanning movement.

[0020] The scan area of the optical detection system is the area range in which objects may be detected by the optical detection system. The scan area is located in the surrounding area of the optical detection system. In embodiments, where the optical detection system is installed in a vehicle, the scan area is located in the surrounding area of the vehicle and may be used, for example, to monitor a closerange or long-range area in the front, rear or blind spot area of the vehicle. The described optical beam steering device and associated method allows to set up an optical detection system, e. g. a lidar sensor, that may use a rotating mirror comprised in the mirror device for the scanning. The optical signal, e. g. the laser beams, are deflected by the mirror and scanning is carried out by rotating the mirror. The described arrangement comprises the prism device in addition to the mirror device. The at least one prism comprised in the prism device is configured to rotate the optical signal. Such a prism may also be referred to as an image rotating prism or rotation prism. The prism is arranged and configured such that it rotates the optical signal using internal refraction and / or reflection. The prism device rotates and performs the second rotating movement. Such a configuration of the prism comprised in the prism device will allow to influence the speed at which the optical signal at the output of the prism device is rotated. The prism device and the mirror device are configured to be optically coupled thus influencing the optical path of the optical signal.

[0021] The first and second rotating movement of the optically coupled mirror device and prism device allows steering the light beam of the optical signal of the detection system such that a scanning system may be realized. Such systems may operate at long range. Examples of long-range lidar systems may for example be able to operate with a detection distance from about 10 m to up to 200 m to 2000 m.

[0022] The optical coupling in between the prism device performing the second rotating movement and the mirror device performing the first rotating movement may for example allow to generate an illumination field that can be kept straight during the scanning movement. A rotation of the illumination field of the optical signal in an undesired direction may be avoided.

[0023] The described optical beam steering device allows the packaging of the optical detection system to be small and vertical. This increases the placement flexibility and higher compatibility with different applications within the vehicle.

[0024] The described optical beam steering device allows to design a scanning detection system where the optical transmission device and the optical reception device may be kept static during scanning. This makes the system less sensitive to damage and more robust.

[0025] Also, the optical components comprised in the beam steering device to manipulate the optical path during the scanning are configured such to reduce losses and misalignments. The optical detection system may be configured with fixed transmission device and fixed reception device. The optical signal on the optical path is optically controlled by few optical components. Such a design offers robustness and compactness.

[0026] In an embodiment of the optical beam steering device, the prism device precedes the mirror device in the optical path. The prism device is placed in the optical path before the mirror device. The optical signal is thus rotated by the prism device before being deflected by the at least one mirror of the mirror device.

[0027] In an embodiment of the optical beam steering device, the optical transmit signal is caused to perform the scanning movement in one scan direction in the scan area. The optical coupling of the prism device and the mirror device is such that the resulting optical transmit signal may perform a scanning movement in one single direction. The scanning movement of the optical transmit signal in the one direction may be effected jointly and simultaneously by the prism device and the mirror device. This allows to simplify the construction of the optical beam steering device, as only one scan direction needs to be performed.

[0028] In an embodiment of the optical beam steering device, a first axis of rotation of the first rotating movement of the mirror device and a second axis of rotation of the second rotating movement of the prism device are parallel to each other. The optical coupling of the prism device and the mirror device is such that the first and second rotating movement has the same direction, thus contributing to the one scan direction.

[0029] In an embodiment of the optical beam steering device, the speed of rotation of the prism device is half the speed of rotation of the mirror device. The prism device may for example be configured such that due to the second rotating movement the optical signal output by the prism device rotates at twice the speed of the second rotating movement. By rotating the prism device at half the speed of the mirror device, the rotation of the optical signal may be the same again - resulting in a desired scan movement in the scan area.

[0030] In an embodiment of the optical beam steering device, the rotating movement of the mirror device comprises a full rotation around its first axis of rotation and / or the rotating movement of the prism device comprises a full rotation around its second axis of rotation. In this embodiment, the first and second rotating movement each is a full rotation. This allows for a more even movement without the need to handle changes in the direction of the rotation. This may result in an overall higher optical quality of the beam steering device. This further enables energy conservation during the rotating movement. It can be performed in a particularly energy-efficient manner. The first and second rotating movement may be at the same or at different speeds. In some embodiments the first and second rotating movement is at different speeds, the second rotating movement for example having half the speed of the first rotating movement.

[0031] The described beam steering device has the further advantage that it may be placed in between the optical transmission device and the optical reception device of the optical detection system. The optical transmission device and the optical reception device may for example be comprised in a lidar system. The optical transmission device and the optical reception device may be placed opposite each other on opposing sides of the beam steering device. This has the further advantage that the packaging size, for example the packaging height, of the lidar system can be reduced because the transmission device and the reception device may be placed in one line. Thus, a slim design with a large field-of-view may be realized.

[0032] In an embodiment of the optical beam steering device, the optical signal entering the optical beam steering device is collimated. This may allow to avoid the introduction of unwanted optical effects by the prism. When convergent light is passed through the prism this may introduce astigmatism for example. This can be avoided by passing collimated light through the optical beam steering device. The optical signal passed through the optical beam steering device may for example be the optical transmit signal that is transmitted by the optical transmission device in a collimated manner.

[0033] In an embodiment of the optical beam steering device, the prism device comprises a Dove prism. The Dove prism is an optical device shaped like a wedge. It is designed to rotate the optical signal. When the Dove prism performs the second rotating movement, the optical signal rotates at twice the speed of the second rotating movement.

[0034] In an embodiment of the optical beam steering device, the prism device comprises a Pechan prism. The Pechan prism may also be referred to as Schmidt-Pechan- prism or Pechan roof prism. The Pechan prism comprises a plurality of prisms in- terfacing at their hypotenuse faces. The optical signal undergoes total internal reflection at the interface or the interfaces before exiting. This allows for a reversion and inversion of the optical signal. The Pechan prism may be designed in a compact way. The Pechan prism is designed to rotate the optical signal. When the Pechan prism performs the second rotating movement, the optical signal rotates at twice the speed of the second rotating movement.

[0035] In an embodiment of the optical beam steering device, the optical signal entering the optical beam steering device has the shape of a line. The line shaped optical signal may for example be an optical transmit signal generated by the optical transmission device of the optical detection system. The line shaped optical transmit signal may then undergo beam steering by the beam steering device and perform a scanning movement in the scan area.

[0036] The optical signal performing the scanning movement may then also have the shape of a scan line. This allows for the scanning of the scan area using the scan line that is moved in the one scan direction. This allows for an efficient line-wise scanning of the scan area.

[0037] In an embodiment of the optical beam steering device, the direction of the scan line shape of the optical transmit signal performing the scanning movement is parallel to the first and / or second axis of rotation. This allows for an orientation of the scan line which is parallel to the rotation axis of the beam steering device. Also, the beam steering device may be placed in an upright orientation with the scan direction in the horizontal. Placing the prism device and the mirror device in a vertical position allows to reduce the overall space of the optical detection system. This leads to a slimmer and more compact design.

[0038] In an embodiment of the optical beam steering device, the scan direction of the scanning movement is perpendicular to the scan line of the optical transmit signal performing the scanning movement. This allows for an efficient coverage and linewise scanning of the scan area.

[0039] In an embodiment of the optical beam steering device, a diffuser is arranged in the optical path in between the prism device and the mirror device, wherein the diffuser is optically coupled to the prism device and the mirror device. The diffuser may be used to diffuse the optical signal, thereby leading to a diffused optical signal and broadening it. This may for example mean that the line shape of the optical signal is lengthened. In an embodiment of the optical beam steering device, the mirror device comprises a first and a second mirror, wherein the first mirror is arranged such that the optical transmit signal which is incident from a first direction is deflectable by the first mirror in the direction of the scan area, wherein the second mirror is arranged such that the optical receive signal being reflected from the scan area is deflectable by the second mirror in a second direction.

[0040] In embodiments of the beam steering device, the first direction and the second direction are longitudinal to each other. The first direction and the second direction may in particular be the same direction. This means that the transmission device and the reception device are aligned against each other in such a way that the respective optical transmit signal and optical receive signal are substantially parallel to each other. In other embodiments, the transmission device and the reception device may be inclined with respect to each other.

[0041] The first rotating movement may be common to the first and second mirror. The first rotating movement of the mirrors may then have the same first axis of rotation. The mirrors may also be fixedly mounted together and may perform the first rotating movement together.

[0042] In an embodiment of the mirror device, the angle between the first mirror and the first direction is fixed during the first rotating movement and the angle between the second mirror and the second direction is fixed during the first rotating movement. The first axis of rotation may in particular be longitudinal to the first direction and the second direction. The angle between the mirror and the first direction may be between around 30° and around 60°, preferably around 45°. The angle between the second mirror and the second direction may be between around 30° and around 60°, preferably around 45°.

[0043] The angle between the first mirror and the first direction may for example be the same as the angle between the second mirror and the second direction. The angle may for example be between 30° and 60°, in particular around 45°.

[0044] The angle in between the first mirror and the second mirror may be between around 80° and around 100°, preferably around 90°.

[0045] In an embodiment of the optical beam steering device, the optical path comprises a transmit path, where the optical transmit signal travels towards the scan area and a receive path, where the optical receive signal travels from the scan area, wherein the prism device is placed in the transmit path of the optical path and / or in the receive path of the optical path. The prism device may in particular be placed in the transmit path between an optical transmission device and the mirror device.

[0046] In an embodiment of the optical beam steering device, one prism device is arranged in the transmit path and in the receive path. A path separation device may be arranged in the optical path to separate the optical transmit signal from the optical receive signal. A path combination device may be arranged in the optical path to combine the optical transmit signal and the optical receive siganl. The separation device and / or the combination device may be based on polarization and comprise in particular a wave plate like e. g. a polarization plate and / or a quarterlambda-plate.

[0047] The described optical beam steering device may be used in an optical detection system, e. g. a lidar system.

[0048] An optical detection system, e. g. lidar system, comprises the optical transmission device, the optical reception device and the described optical beam steering device.

[0049] Depending on the first and second rotating movement, a field of view of more than 180° may be achieved for scanning optical detection systems, in particular lidar systems, comprising the described beam steering device.

[0050] In an embodiment of the optical detection system, the optical transmission device comprises a light source which has the shape of a line. The light source emits the optical transmit signal, which is line shaped. The optical transmit signal entering the optical beam steering device is also line shaped. Using the optical beam steering device, the optical detection system is configured to cause the line shaped optical transmit signal, the scan line, to perform a scanning movement in the scan direction. The scanning movement is performed such that the scan area of the optical detection system is at least partially covered by the scan line of the optical transmit signal.

[0051] In an embodiment of the optical detection system, the optical transmission device comprises a light source which emits a collimated optical transmit signal. The optical transmit signal that enters the optical beam steering device is collimated. This helps avoiding unwanted optical effects. In an embodiment of the optical detection system, the optical reception device comprises an optical sensor which has the shape of a rectangle, in particular a square. The optical reception device may thus be arranged to capture the optical receive signal on the receive path after reflection from the scan area.

[0052] In an embodiment of the optical detection system, the optical transmission device and the optical reception device are arranged on opposing sides of the beam steering device. This has the advantage that the packaging size, in particular the packaging height, of the optical detection system may be reduced because the transmission device and the reception device may be placed in one line.

[0053] In an embodiment of the optical detection system, the optical transmission device, the optical beam steering device and the optical reception device are arranged in one line, which is parallel to the scan line of the optical transmit signal performing the scanning movement. This may have further advantages with respect to packaging in the vehicle.

[0054] Brief description of the figures

[0055] Embodiments will now be described with reference to the attached drawing figures by way of example only. Like reference numerals are used to refer to like elements throughout. The illustrated structures and devices are not necessarily drawn to scale.

[0056] Fig. 1 schematically illustrates an optical detection system comprising a first embodiment of a beam steering device.

[0057] Fig. 2 schematically illustrates an optical detection system comprising a second embodiment of a beam steering device.

[0058] Fig. 3 schematically illustrates a vehicle comprising the optical detection system.

[0059] Fig. 4 schematically illustrates a scan area with a scan line.

[0060] Detailed Description

[0061] Fig. 1 schematically illustrates an optical detection system 10 comprising a first embodiment of a beam steering device 8.

[0062] An optical transmission device 1 emits an optical transmit signal LI. The optical transmit signal LI is a laser light signal emitted in a first direction DI by a laser light source. The optical transmit signal LI is line shaped and collimated. The light source may for example be configured with a 0,05° and 26 ° field of illumination.

[0063] The beam steering device 8 comprises a mirror device 4. The mirror device 4 comprises a first mirror SF1 and a second mirror SF2. The two mirrors SF1, SF2 are in a fixed and tilted position with respect to each other. They have an angle of 90° in between them. The first and second mirror SF1, SF2 have a tilt of 45° with respect to the first direction DI each. The mirror device 4 performs a first rotating movement around a first axis of rotation. The first and the second mirror SF1, SF2 perform the same first rotating movement around the first axis of rotation. The first axis of rotation traverses the first and the second mirror SF1, SF2. The first and the second mirror SF1, SF2 remain fixed with respect to each other during the first rotating movement.

[0064] The optical transmit signal LI is deflected by the first mirror SF1. After this deflection the scan area 12 is illuminated by a scan line H. The optical transmit signal LI is reflected from e. g. an object O and hits the second mirror SF2 as an optical receive signal L2. The second mirror SF2 reflects the optical receive signal L2 in a second direction D2 to a square shaped optical sensor comprised in the optical reception device 2. The first and second mirror SF1, SF2 have a tilt of 45° with respect to the second direction D2 each.

[0065] The scanning of the scan area 12 in a scan direction 7 is done using the rotation of the set of first and second mirrors SF1, SF2. For an embodiment, where the arrangement of the beam steering device 8 is vertical, the scanning movement of the scan line H is horizontal with the horizontal scan direction 7. The horizontal illumination field of the scan line H may for example be 0,05° and the vertical illumination field of the scan line H may for example be 26°. The Dove prism 5 may have dimensions of between 5 and 15 cm in each dimension, like e. g. 7x7x13 cm.

[0066] As the set of mirrors SF1, SF2 rotates and performs the first rotating movement, the scan area 12 may be illuminated by scanning in a 180° or more horizontal field of view.

[0067] A prism device comprising a rotation prism, e. g. a Dove prism 5, is arranged in an optical transmit path between the optical transmission device 1 and the mirror device 4. The optical transmit path is comprised in the optical path and extends from the optical transmission device 1 to the scan area 12, where the optical transmit signal LI is reflected back as the optical receive signal L2. The optical transmit signal LI emitted from the transmission device 1 is collimated. The collimated optical transmit signal LI enters the Dove prism 5, the collimation thus reducing illumination aberrations. The rotation prism rotates the optical transmit signal LI making used of internal refractions and / or reflections. This means that the image of the optical transmit signal LI as it leaves the optical transmission device 1 is rotated at the output of the Dove prism 5 before arriving at the mirror device 4. The Dove prism 5 for example may be configured to only need one internal reflection to rotate the optical transmit signal LI. This reduces the optical losses within the prism 5.

[0068] The Dove prism 5 itself performs a second rotating movement around a second axis of rotation. This rotation is configured such that the first mirror SF1 receives the same image of the optical transmit signal LI as the optical transmit signal LI that leaves the optical transmission device 1 throughout the whole rotating movement.

[0069] To assure that the first mirror SF1 receives the same image of the optical transmit signal LI for each x degree of the first rotating movement, the Dove prism 5 is configured to rotate x / 2 degrees of the second rotating movement. This choice is adapted to the property of the Dove prism 5, for which the rotation of the output image is twice as large as the second rotating movement.

[0070] A diffuser 3 is arranged in between the Dove prism 5 and the mirror device 4. The optical transmit signal LI is thus diffused by the diffuser 3 after the Dove prism 5 and before hitting the mirror device 4. As a result, the field of illumination comprises the vertical scan line H moving in the scan direction 7.

[0071] The optical transmission device 1 and the optical reception device 2 may be aligned in the same optical access of the optical detection system 10, which may reduce mismatch between them during the scanning.

[0072] The prism device may be used on the optical receive path in a similar fashion as described above. The optical receive path is comprised in the optical path and extends from the scan area 12 to the optical reception device 2. The optical receive path and the optical transmit path may share the same Dove prism 5 with an optical combination and separation element like e. g. a polarisation plate or a quarter lambda plate. Fig. 2 schematically illustrates an optical detection system 10 comprising a second embodiment of the beam steering device 8.

[0073] The optical transmission device 1 emits the optical transmit signal LI. The optical transmit signal LI is a laser light signal emitted in a first direction DI by a laser light source. The optical transmit signal LI is line shaped and collimated. The light source may for example be configured with a 0,05° and 26 ° field of illumination.

[0074] The beam steering device 8 comprises the mirror device 4 as described with respect to figure 1.

[0075] For the embodiment, where the arrangement of the beam steering device 8 is vertical, the scanning movement of the scan line H is horizontal with the horizontal scan direction 7. The horizontal illumination field of the scan line may for example be 0,05° and the vertical illumination field of the scan line H may for example be 26°.

[0076] As the set of mirrors SF1, SF2 rotates and performs the first rotating movement, the scan area 12 may be illuminated by the scan line H performing a scan with a 180° or more horizontal field of view.

[0077] The prism device comprises the rotation prism, e. g. a Pechan prism 6. The Pechan prism 6 is arranged in the optical transmit path between the optical transmission device 1 and the mirror device 4. The optical transmit signal LI emitted from the transmission device 1 is collimated. The collimated optical transmit signal LI enters the Pechan prism 6, the collimation thus reducing illumination aberrations. The rotation prism rotates the optical transmit signal LI making use of internal refractions and / or reflections. This means that the image of the optical transmit signal LI as it leaves the optical transmission device 1 is rotated at the output of the Pechan prism 6 before arriving at the mirror device 4.

[0078] The Pechan prism 6 may be configured to need five internal reflections to rotate the optical transmit signal LI. The Pechan prism 6 may be designed with a vertical dimension that is compact, reducing the total height of the optical detection system 10. The vertical dimension is the dimension of the Pechan prism 6 in the first direction DI or parallel to the second axis of rotation. The Pechan prism 6 may have dimensions of between 5 and 15 cm in each dimension, like e. g. 7x7x10 cm.

[0079] The Pechan prism 6 itself performs a second rotating movement around the second axis of rotation. This rotation is configured such that the first mirror SF1 receives the same image of the optical transmit signal LI as it leaves light source of the optical transmission device 1 throughout the whole rotating movement.

[0080] To assure that the first mirror SF1 receives the same image of the optical transmit signal LI for each x degree of the first rotating movement, the Pechan prism 6 is configured to rotate x / 2 degrees of the second rotating movement. This choice is adapted to the property of the Pechan prism 6, for which the rotation of the output image is twice as large as the second rotating movement.

[0081] A diffuser 3 is arranged in between the Pechan prism 6 and the mirror device 4. The optical transmit signal LI is thus diffused by the diffuser 3 after the Pechan prism 6 and before hitting the mirror device 4. As a result, the field of illumination is a vertical scan line H moving in the scan direction 7.

[0082] The optical transmission device 1 and the optical reception device 2 may be aligned in the same optical access of the optical detection system 10, which may reduce mismatch between them during the scanning.

[0083] The prism device may be used on the receive path in a similar fashion as described above. The optical receive path is comprised in the optical path and extends from the scan area 12 to the optical reception device 2. The optical receive path and the optical transmit path may share the same Pechan prism 6 with an optical combination and separation element like e. g. a polarisation plate or a quarter lambda plate.

[0084] Fig. 3 schematically illustrates a vehicle 20, for example a passenger car. The optical detection system 10, e. g. a lidar system, is arranged in a front area of the vehicle 20. The optical detection system 10 comprises the optical transmission device 1 and the optical reception device 2. The beam steering device 8 is arranged between the transmission device 1 and the reception device 2. In a control unit 9, the optical transmit signal LI and the optical receive signal L2 may be evaluated e. g. using time-of-flight measurements. The evaluation may serve to detect objects O in the scan area 12. The control unit 9 may also be used to monitor and control the transmitting process in the transmission device 1, the receiving process in the reception device 2 and the first and second rotating movement.

[0085] In the embodiment shown in figure 3, the scan area 12 is located in front of the vehicle 20. Thus, in the example shown, an area in front of the vehicle 20 in the direction of travel may be monitored. It is also possible to arrange the optical detection system 10 in other areas of the vehicle 20, for example in the rear area and / or in lateral areas. It is also possible to arrange several optical detection systems 10 on the vehicle 20, in particular also in corner areas of the vehicle 20. The desire to place several optical detection systems 10 on the vehicle 20 makes the compact, slim design and a possible vertical arrangement of the optical detection systems 10 even the more beneficial. The horizontal field of view and the associated scan area 12 for the described optical detections system 10 may extend well beyond 180° and achieve a horizontal field of view of up to 270° when arranged in corner areas of the vehicle 20, for example.

[0086] The optical detection system 10 may be used to detect stationary or moving objects O in the scan area 12. Objects O may be vehicles, persons, animals, plants, obstacles, roadway unevenness, in particular potholes or stones, roadway boundaries, traffic signs, open spaces, in particular parking spaces, precipitation, or the like.

[0087] Fig. 4 schematically illustrates the scan area 12 with the scan line H.

[0088] As described in connection with the preceding figures, it is possible to deflect the optical transmit signal LI by means of the beam steering device 8 in such a way that the optical transmit signal LI slides as a scan line H over the scan area 12 as the optical transmit signal LI is rotated by the prism device and deflected by the first mirror SF1. The prism device performs the second rotating movement, the mirror device 4 performs the first rotating movement. The optical transmit signal LI thereby scans the scan area 12, e. g. illuminates it step by step, in the scan direction 7. The optical transmit signal LI is then reflected back by objects O and / or by the environment in the scan area 12 as the optical receive signal L2. The optical receive signal L2 is then deflected by the second mirror SF2 of the mirror device 4 in the second direction D2 onto the reception device 2. The reception of the optical receive signal L2 is then performed by the reception device 2.

[0089] The described optical detection system 10 can be compactly designed with the transmission device 1 and the reception device 2 located in roughly one line on opposing sides of the beam steering device 8. This allows for a vertical form factor of the optical detection system 10 with the transmission device 1 and the reception device 2 in one vertical optical axis. This means that installation space in the vehicle 20 may be reduced. The described form factor may in particular be advantageous when installing the optical detection system 10 e. g. at bumper height of e. g. a passenger car. At the same time, precise and efficient scanning of the scan area 12 may be realized. The described optical detection system 10 may even achieve a 360° field of view and associated scan area 12, when e. g. arranged on the top of the vehicle 20. This so called "spinner" behaviour may be achieved with the described beam steering device 8, where the transmission and reception device 1, 2 may remain at a fixed position during the spinning movement.

Claims

CLAIMS1. Optical beam steering device (8) for an optical detection system (10), wherein the beam steering device (8) comprises a mirror device (4) and a prism device arranged in an optical path of an optical signal, wherein the mirror device (4) comprises at least one mirror (SF1, SF2), which is configured to deflect the optical signal, and wherein the mirror device (4) is configured to perform a first rotating movement, wherein the prism device comprises at least one prism (5, 6), which is configured to rotate the optical signal, and wherein the prism device is configured to perform a second rotating movement, wherein the optical signal comprises an optical transmit signal (LI) and / or an optical receive signal (L2), wherein the mirror device (4) and the prism device are optically coupled, thereby causing the optical transmit signal (LI) to perform a scanning movement in a scan area (12) and / or thereby capturing the optical receive signal (L2) reflected from the scan area (12), the optical transmit signal (LI) having performed a scanning movement.

2. Optical beam steering device according to claim 1, wherein the prism device precedes the mirror device (4) in the optical path.

3. Optical beam steering device according to claim 1 or 2, wherein the optical transmit signal (LI) is caused to perform the scanning movement in one scan direction (7) in the scan area (12).

4. Optical beam steering device according to one of the preceding claims, wherein a first axis of rotation of the first rotating movement of the mirror device (4) and a second axis of rotation of the second rotating movement of the prism device are parallel to each other.

5. Optical beam steering device according to one of the preceding claims, wherein the speed of rotation of the prism device is half the speed of rotation of the mirror device (4).

6. Optical beam steering device according to one of the preceding claims, wherein the first rotating movement of the mirror device (4) comprises a full rotation around its first axis of rotation and / or wherein the second rotating movement of the prism device comprises a full rotation around its second axis of rotation.

7. Optical beam steering device according to one of the preceding claims, wherein the optical signal entering the optical beam steering device (8) is collimated.

8. Optical beam steering device according to one of the preceding claims, wherein the prism device comprises a Dove prism (5).

9. Optical beam steering device according to one of the preceding claims, wherein the prism device comprises a Pechan prism (6).

10. Optical beam steering device according to one of the preceding claims, wherein the optical signal entering the optical beam steering device (8) has the shape of a line.

11. Optical beam steering device according to one of the preceding claims, wherein the optical transmit signal (LI) performing the scanning movement has the shape of a scan line (H).

12. Optical beam steering device according to claim 11, wherein the direction of the scan line (H) performing the scanning movement is parallel to the first and / or second axis of rotation.

13. Optical beam steering device according to claim 11 or 12, wherein the scan direction (7) of the scanning movement is perpendicular to the line shape of the optical transmit signal (LI) performing the scanning movement.

14. Optical beam steering device according to one of the preceding claims, wherein a diffuser (3) is arranged in the optical path in between the prism device and the mirror device (4), wherein the diffuser (3) is optically coupled to the prism device and the mirror device (4).

15. Optical beam steering device according to one of the preceding claims, wherein the mirror device (4) comprises a first and a second mirror (SF1, SF2), wherein the first mirror (SF1) is arranged such that the optical transmit signal (LI) which is incident from a first direction (DI) is deflectable by the first mirror (SF1) in the direction of the scan area (12), wherein the second mirror (SF2) is arranged such that the optical receive signal (L2) being reflected from the scan area (12) is deflectable by the second mirror (SF2) in a second direction (D2).

16. Optical beam steering device according to claim 15, wherein the angle in between the first mirror (SF1) and the second mirror (SF2) is between around 80° and around 100°, preferably around 90°.

17. Optical beam steering device according to one of the preceding claims, wherein the optical path comprises a transmit path, where the optical transmit signal (LI) travels towards the scan area (12) and a receive path, where the optical receive signal (L2) travels from the scan area (12), wherein the prism device is placed in the transmit path of the optical path and / or in the receive path of the optical path.

18. Optical beam steering device according to claim 17, wherein one prism device is arranged in the transmit path and in the receive path, wherein a path separation device is arranged in the optical path to separate the optical transmit signal (LI) from the optical receive signal (L2) and / or a path combination device is arranged in the optical path to combine the optical transmit signal (LI) and the optical receive signal (L2).

19. Optical beam steering device according to claim 18, wherein the separation device and / or the combination device is based on polarization and comprises in particular a wave plate.

20. Use of the optical beam steering device of one of the previous claims in an optical detection system (10), e. g. a lidar system.

21. Optical detection system (10), e. g. lidar system, comprising an optical transmission device (1), an optical reception device (2) and an optical beam steering device (8) according to one of claims 1 to 19.

22. Optical detection system according to claim 21, wherein the optical transmission device (1) comprises a light source which has the shape of a line.

23. Optical detection system according to claim 21 or 22, wherein the optical reception device (2) comprises an optical sensor which has the shape of a rectangle, in particular a square.

24. Optical detection system according to one of claims 21 to 23, wherein the optical transmission device (1) and the optical reception device (2) are arranged on opposing sides of the beam steering device (8).

25. Optical detection system according to one of claims 21 to 24, wherein the optical transmission device (1), the optical beam steering device (8) and the optical reception device (2) are arranged in one line, which is parallel to the scan line (H) performing the scanning movement.

26. Method for performing beam steering of an optical signal using an optical beam steering device (8), wherein the optical beam steering device (8) comprises a mirror device (4) comprising at least one mirror (SF1, SF2) and performing a first rotating movement and wherein the optical beam steering device (8) comprises a prism device comprising a prism (5, 6) and performing a second rotating movement, wherein the optical signal comprises an optical transmit signal (LI) and / or an optical receive signal (L2), the method comprising:• the prism rotating the optical signal,• the at least one mirror (SF1, SF2) deflecting the optical signal, wherein the mirror device (4) and the prism device are optically coupled• thereby causing the optical transmit signal (LI) to perform a scanning movement in a scan area (12) and / or• thereby capturing the optical receive signal (L2) reflected from the scan area (12), the optical transmit signal (LI) having performed the scanning movement.

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