Optical scanner

Abstract

An optical scanner for determining the distance of an object relative to the scanner comprises at least one light source, a receiver, and a deflection device. The light source is designed to emit an optical signal. The receiver is stationary and configured to receive light generated by the signal reflected or re-emitted from the object. The deflection device deflects light reflected or re-emitted from the object to focus it onto a receiving element of the receiver. Furthermore, the light source and the deflection device are configured to rotate about a common axis.

Description

[0001] The invention relates to an optical scanner which is intended to determine the distance of an object relative to the optical scanner.

[0002] The distance of an object relative to a reference position can be determined, for example, using optical sensors that operate according to the triangulation principle or that perform time-of-flight (ToF) measurements. However, sensors with time-of-flight measurements are more complex and therefore more expensive than sensors that utilize the triangulation principle, since light travel times in the picosecond to nanosecond range typically require technically sophisticated equipment.

[0003] Optical scanners that operate according to the triangulation principle typically scan a spatial area, with a light beam from the scanner running along a line (1D scanners) or scanning a surface area (2D scanners). However, such scanners only provide sufficient depth information for a very limited angular range.

[0004] This limitation complicates the use of such scanners, for example, in autonomous vehicles or robot grippers, where it is necessary to determine the distance or proximity of objects within a monitoring area that should extend over a large angular range. Such a large angular range of the monitoring area can, for example, cover almost 360°.

[0005] From DE 10 2015 008 310 A1 an optical scanner and a method according to the respective preamble of claim 1 and 12 are known.

[0006] An object of the invention is to provide an optical scanner and a method for determining the distance of an object relative to the optical scanner, which allow scanning of a surveillance area over a large angular range, if possible of almost 360°.

[0007] This object is achieved by an optical scanner and a method having the features of the independent claims. Advantageous developments of the invention are specified in the subclaims, the description, and the drawings.

[0008] The optical scanner is designed to determine the distance of an object relative to the optical scanner and comprises at least one light source, a receiving device, and a deflection device. The light source is designed to emit an optical transmission signal. The receiving device is stationary and designed to receive light generated by the transmission signal reflected or remitted by an object. The deflection device deflects at least a portion of the light reflected or remitted by the object for imaging onto a receiving element of the receiving device. Furthermore, the light source is designed to rotate together with the deflection device about a common axis.

[0009] The distance of the object can be determined relative to a predefined reference position on the optical scanner by an evaluation device assigned to the receiving device, for example, using the triangulation principle and calculating the distance of the object based on a position of the image of the reflected or remitted transmission signal on the receiving element with known dimensions within the scanner.

[0010] The transmitted signal can be a light beam, which is emitted, for example, by a light-emitting diode (LED) or, preferably, by a laser and thus illuminates the object almost point-like. The optical scanner can therefore scan a predefined monitoring area one- or two-dimensionally using such a light beam. For two-dimensional scanning, the optical scanner can have multiple light sources that are intended to scan a respective position or plane and are therefore arranged one above the other, for example. In order to be able to differentiate between the transmitted signals of the multiple light sources reflected or remitted by one or more objects using the receiving device, it is useful if the light sources each emit light with a different wavelength or color, or if temporal multiplexing is used to control the multiple light sources and the receiving device.

[0011] The optical scanner is characterized by the fact that the light source is coupled to the deflection device in such a way that they execute a synchronous rotational movement around the common axis. For this purpose, the light source and the deflection device can be mechanically connected to one another, for example. As mentioned above, the receiving device, in contrast, is arranged in a stationary manner. The light source, the deflection device, and the stationary receiving device are arranged in such a way that light reflected or remitted from the object is imaged onto one or more receiving elements of the receiving device even during the rotational movement of the light source and the deflection device. The receiving element can be two-dimensional, for example, as a light-sensitive surface.

[0012] Because the light source rotates with the deflection device, there are no restrictions on the angular range that the light source or optical scanner can scan. Consequently, the optical scanner is capable of scanning a large angular range of nearly or equal to 360°. The optical scanner with joint rotation of the light source and deflection device, utilizing the triangulation principle, enables the determination of an object's distance with minimal effort and therefore in a cost-effective manner.

[0013] Furthermore, the joint rotation of the light source and the deflection device allows for a compact arrangement or construction of the scanner components. Furthermore, if the receiving device's receiving element is designed for the visible spectral range, it can capture a camera image of the optical scanner's field of view or detection range in addition to determining the distance.

[0014] According to the invention, the optical scanner additionally comprises an evaluation device designed to determine the distance of the object relative to the optical scanner based on a distance between an imaging position of the object on the receiving element of the receiving device and a reference point on the receiving element. In other words, the distance of the object relative to the optical scanner is determined using the triangulation principle by means of the scanner's evaluation unit. This enables efficient determination of the object distance, for example, compared to sensors that determine the object distance based on the light travel time. Optical scanners or sensors that determine the distance or distance of an object based on the light travel time require technically sophisticated and expensive receiving and evaluation units in order to be able to measure light travel times in the picosecond to nanosecond range.

[0015] In contrast to known triangulation sensors, the scannable angular range of the optical scanner according to the invention is subject to virtually no restrictions. All that is required is to determine a reference point on the receiving element as the origin of a polar coordinate system, for example, in order to determine the distance of the object relative to the sensor based on the distance between the object's imaging position and the origin of the coordinate system. The origin of the coordinate system can be determined, for example, by means of a calibration measurement using a distant object whose imaging position should be located almost at the center of the coordinate system.

[0016] Typically, optical scanners can only determine distances or distances between objects up to a few meters using the triangulation principle. Therefore, for example, an object located outside such a typical measurement or monitoring range of the optical scanner is suitable for determining the reference point on the receiving element of the receiving device. The distances on the receiving element between the imaging position and the reference point are inversely proportional to the distances to be determined between the objects relative to the optical scanner, i.e., to the actual distances between the objects within the monitoring range of the optical scanner.

[0017] A receiving optics system can also be provided between the deflection device and the receiving element. The receiving optics system can, for example, comprise only a diaphragm or additional imaging elements, such as lenses.

[0018] According to a further embodiment, an angular position of the object relative to a predetermined direction can be determined based on an imaging position on the receiving element. Due to the synchronous rotation of the light source and the deflection device, no reference is required to determine the angular position of the object. Instead, for example, only the installation position of the rotating light source relative to the deflection device can be specified, so that the angular position of an object during a scan unambiguously corresponds to the angular position of the imaging position on the receiving element and is, in a sense, encoded by it.

[0019] Typically, the imaging position for determining the angular position is the same as the imaging position for determining the distance. In other words, using a single imaging position of the object, both the distance and the angular position of the object relative to the optical scanner can be determined. In this embodiment, the optical scanner can thus simultaneously provide the distance and angular position of the object with relatively little effort.

[0020] According to a further embodiment, the light source is attached to the deflection device. The light source can, for example, be attached to a top or bottom of the deflection device or behind the deflection device and mechanically connected to it. If the light source is arranged behind the deflection device, the deflection device can, for example, comprise small openings or semi-transparent segments or regions.

[0021] The light source can be offset relative to the rotation axis in a direction perpendicular to the rotation axis. A mechanical connection of the light source to the deflection device for their joint rotation can be facilitated by such an offset. This can be particularly the case if the deflection device is arranged at a predetermined angle relative to the rotation axis, for example, as an obliquely arranged mirror. In such a case, the light source can be arranged on the top side or at an upper edge of the deflection device, while the rotation axis runs near a center of the deflection device.

[0022] Furthermore, the light source may be inclined by a predefined angle with respect to a horizontal plane perpendicular to the axis of rotation.

[0023] In particular, the inclination of the light source can be adjustable. Such an inclination of the light source can enable the definition of a specific monitoring area for the optical scanner, which can be located, for example, on the ground or in a road area near the optical scanner. This can be particularly relevant if the optical scanner is intended for an autonomously driving vehicle.

[0024] In this embodiment, the transmitted signal from the light source thus impinges on a floor area in the vicinity of the optical scanner or a device on which the optical scanner is installed at an adjustable angle. Changing the inclination of the light source also enables an expansion of the scanning range or monitoring area of ​​the optical scanner. In other words, the one-dimensional scanning process, which is carried out by means of the joint rotational movement of the light source and the deflection device, can be extended to a second dimension perpendicular to the original one-dimensional rotation or scanning direction.

[0025] If the light of the transmitted signal has a wavelength in the visible spectral range, the light source in this embodiment can additionally be used to mark a protection or monitoring area on the floor in the vicinity of the optical scanner. Alternatively, the optical scanner can also have another light source for this purpose, which is intended exclusively for illuminating the floor. Such optical marking of a protection area is relevant, for example, when the optical scanner is used on an autonomous vehicle or a robot gripper.

[0026] According to a further embodiment, the deflection device comprises a mirror. The mirror can be designed as a planar mirror or as a concave mirror. Designing the deflection device as a mirror enables cost-effective production of the optical scanner.

[0027] If the mirror is designed as a planar mirror, it can be positioned at an angle to the rotation axis that ranges from 40° to 50°, preferably 45°. An angle of 45° enables a symmetrical and clear optical image structure within the optical scanner.

[0028] According to another embodiment, the light source comprises a laser that illuminates the object in a point-like manner. Such point-like illumination by means of a scanner enables a clearly defined scanning process with high resolution. Alternatively or additionally, however, the light source can also comprise a light-emitting diode (LED).

[0029] The invention further relates to a method for determining the distance of an object relative to an optical scanner, such as the one described above, which comprises a light source for emitting an optical transmission signal, a stationary receiving device, and a deflection device. The receiving device is configured to receive light generated by the transmission signal reflected or remitted by an object, while the deflection device deflects light reflected or remitted by the object for imaging onto a receiving element of the receiving device.

[0030] According to the method, the light source is rotated together with the deflection device about a common axis. Furthermore, the distance of the object relative to the optical sensor is determined based on a distance between an imaging position of the object on the receiving element and a reference point on the receiving element, in particular using the triangulation principle. In addition, an angular position of the object relative to a predetermined direction is determined based on the imaging position.

[0031] The method can thus be carried out using the optical scanner described above. The statements regarding the optical scanner therefore apply accordingly to the method, particularly with regard to advantages and preferred embodiments. Furthermore, it is understood that all features mentioned herein can be combined with one another, unless explicitly stated otherwise.

[0032] The invention is described below by way of example using an advantageous embodiment with reference to the accompanying figures. They show, schematically: Fig. 1 a side view of an optical scanner according to the invention, Fig. 2 a top view of the optical scanner together with two objects arranged at different distances and different angular positions relative to the optical scanner, and Fig. 3 a representation of an image of the objects of Fig. 2 on a receiving element of the optical scanner.

[0033] Fig. 1 shows a schematic representation of an optical scanner 100 according to the invention, which is provided for determining a respective distance 110, 112, 114 of a corresponding object 120, 122, 124 relative to the optical scanner 100. The objects 120, 122, 124 are merely illustrated by markings at their respective distances 110, 112, 114. In the present example, the distances 110, 112, 114 refer to a rotation axis 105 of the optical scanner 100.

[0034] The optical scanner 100 comprises a light source 130, which is configured as a laser and emits an optical transmission signal 132 radially outward. In other words, the light source 130 acts like a laser pointer, generating an illumination spot on the respective object 120, 122, 124. If the light spot of the laser pointer points directly toward an object, its light is remitted by the object, i.e., typically diffusely reflected.

[0035] The optical scanner 100 further comprises a deflection device 140 in the form of a planar mirror and a receiving device 150. The planar mirror 140 is arranged at an angle 142 of 45° with respect to the rotation axis 105.

[0036] The mirror 140 is provided to deflect light reflected or remitted by the respective object 120, 122, 124 for imaging onto a receiving element 152 of the receiving device 150. Light striking the rotating mirror 140 is specularly reflected by it. To image the respective illumination point on the respective object 120, 122, 124 onto the receiving element 152, a receiving optics 154, designed as a diaphragm, is provided between the mirror 140 and the receiving element 152. However, the receiving optics 154 can comprise additional imaging elements, such as one or more lenses.

[0037] The receiving element 152 of the receiving device 150 can also be configured as an imager, with which the entire respective object 120, 122, 124, and not just a single illumination point, can be imaged onto the receiving element 152 by means of the receiving optics 154. Thus, with appropriate application, camera images of the objects 120, 122, 124 can be captured by means of the receiving element 152 of the optical scanner 100.

[0038] The light source or laser 130 is attached to the mirror 140 and arranged at its upper end. As a result, the laser 130 is offset by a displacement distance 134 relative to the rotation axis 105.

[0039] During operation of the optical scanner 100, the light source or laser 130, together with the mirror 140, performs a joint rotation about the rotation axis 105, since the laser 130 is attached to the mirror 140. The receiving device 150, however, is arranged in a stationary manner, so that during operation of the optical scanner 100, the laser 130 and the mirror 140 rotate about the rotation axis 105 relative to the stationary receiving device 150. The rotational movement of the laser 130 together with the mirror 140 is illustrated by the rotation arrow 160.

[0040] Due to the joint rotational movement of the laser 130 and the mirror 140, it is not only possible to determine the respective distance 110, 112, 114 of the objects 120, 122, 124 relative to the rotation axis 105 using the triangulation principle. Likewise, an angular position of the respective objects 120, 122, 124 relative to a predetermined direction can also be determined, as will be explained below in connection with Fig. 2 and Fig. 3. The distances 110, 112, 114 and the angular positions of the objects 120, 122, 124 are determined by means of an evaluation unit (not shown) based on electrical signals output by the receiving element 152.

[0041] The determination of the respective distances 110, 112, 114 of the objects 120, 122, 124 is carried out using the triangulation principle, as described in Fig. 1. If the respective distances between the mirror 140, the aperture 154 and the receiving element or imager 152 as well as the orientation of the mirror 140 with respect to the axis of rotation 105, which is given by the angle 142, are known, the distances 110, 112, 114 can be determined in a manner known per se based on the distances and angles in respective similar triangles if respective distances between imaging positions 320, 322, 324 of the objects 120, 122, 124 and a reference point 325 on the receiving element 152 are determined.

[0042] Fig. Figure 2 shows a schematic top view of the optical scanner 100 of Fig. 1 together with the two objects 120, 122. The objects 120, 122 are arranged not only at different distances 110, 112 relative to the rotation axis 105, but additionally at different angles 230, 232 relative to a reference direction 220.

[0043] Fig. 3 shows a schematic plan view of the two-dimensional receiving element or imager 152. For the sake of clarity, Fig. 2 and Fig. 3 only the objects 120 and 122 with the respective distances 110 and 112, the corresponding imaging positions 320, 322 and their distances 310, 312 relative to the reference point 325 are shown. Due to the optical imaging via the mirror 140, the imaging positions 320, 322 of Fig. 3 related to the positions of objects 120 and 122 of Fig. 2 is rotated by 180° in the top view. How best to see in the side view of Fig. 1, the positions of the objects 120, 122 on the one hand and the imaging positions 320, 322 on the other hand are on opposite sides with respect to the axis of rotation 105.

[0044] At positions 320 and 322, respectively, the receiving element 152 detects the respective image of the points on the object 120 and 122, respectively, which are illuminated by the laser 130 by means of the transmission signal 132 (cf. Fig. 1). Based on the respective distances 310, 312 (cf. Fig. 3) relative to the reference point 325, the respective distance 110 or 112 can be determined by means of the triangulation principle, as explained above.

[0045] The two-dimensional receiving element or imager 152 is configured as an array with a two-dimensional array of light-sensitive pixels. This enables the imager 152 to determine one or more pixels and their positions, where the imaging positions 320, 322 are located. Based on the position of the pixels, the position of the image points 320, 322 in the plane of the imager 152 is thus known. The reference point 325 can be determined by means of calibration, for example, using one or more objects illuminated from a large distance by the laser 130.

[0046] How to Fig. 1, the distances 110, 112, 114 of the objects 120, 122, 124 are inversely proportional to the distances of the corresponding imaging points 320, 322, 324 relative to the reference point 325. In other words, the imaging points move further and further towards the reference point 325 as the distance of the respective object increases.

[0047] To illustrate this relationship between the distances 110, 112 of the objects 120, 122 relative to the rotation axis 105 and the distances 310, 312 in the plane of the imager 152, Fig. 2 additionally shows circles 210, 212, the center of which is the rotation axis 105 and the radius of which corresponds to the respective distance 110 or 112 of the objects 120, 122 relative to the rotation axis 105. In Fig. 3 shows corresponding circles 311, 313, the center of which is the reference point 325 and the radius of which corresponds to the distance 310 or 312 of the imaging points 320 or 322 with respect to the reference point 325 in the plane of the imager 152.

[0048] All objects arranged on the respective circle 210 or 212 and thus have the same distance 110 or 112 relative to the axis of rotation 105 generate corresponding imaging points which lie in the plane of the imager 152 on the corresponding circle 311 or 313 with the radius 310 or 312. The objects with the greater distance 112, which are correspondingly arranged on the dashed circle 212 with the larger radius 112, are assigned image points in the plane of the imager 152 with the distance 312 on the dashed circle 313 with the smaller radius 312. Conversely, the objects with the smaller distance 110, which are arranged on the solid circle 210, are assigned imaging positions in the plane of the imager 152 on the larger solid circle with the radius 310.The dashed and solid circles thus illustrate the inversely proportional relationship of the real distances 110, 112 to the distances 310, 312 in the plane of the imager 152.

[0049] Since the light source or laser 130 together with the mirror 140 (cf. Fig. 1) performs a common rotational movement around the rotation axis 105 (see the rotation arrow 160 in Fig. 1 and Fig. 2), the objects 120, 122 are illuminated by the laser 130 by means of the transmission signal 132 as soon as the joint rotational movement of the laser 130 and the mirror 140 reaches the angle 230 or 232 (cf. Fig. 2). In the plane of the receiving element or imager 152, when the laser 130 is aligned at an angle 230 or 232 relative to the reference direction 220 during the rotational movement and illuminates the respective object 120, 122, the corresponding image point 320 or 322 is created, which is in each case Fig. 3 is shown.

[0050] Due to the optical imaging, the reference direction 220 corresponds to Fig. 2 an imaging reference direction 305 in Fig. 3, which is rotated by 180° with respect to the reference direction 220. If, for example, the reference direction 220 marks the beginning of a respective rotation scan and thus defines an angle of 0°, the rotation scan begins in the direction shown in Fig. 3, which thus defines the corresponding angle of 0° in the plane of the receiving element 152. Respective angles 330, 332 of the imaging positions 320, 322 are therefore to be determined in the plane of the receiving element 152 relative to the imaging reference direction 305.

[0051] If the reference direction 220 is given, for example, as the initial alignment of the laser 130 and the mirror 140 for the rotary scan or the rotary movement, it is possible to determine the respective angle 230, 232 of the objects 120, 122 with respect to the reference direction 220 based on the respective image of the illuminated objects 120, 122 (cf. Fig. 1) or the pixels of the image positions 320, 322 (cf. Fig. 2) or based on their angles 330, 332 relative to the imaging reference direction 305. The angular position of the laser 130 during its rotational movement together with the mirror 140 is thus permanently assigned to a corresponding angular position on the receiving element 152 or the imager, so that the angular position in the plane of the imager 152 is uniquely encoded. The angles 330, 332 in the plane of the imager 152 thus directly correspond to the angles 230, 232 at which the respective object 120 or 122 is illuminated by the laser 130 during its rotational movement.

[0052] The advantage of the optical scanner 100 is, on the one hand, that it is not limited to a specific angular range, but rather enables scanning of objects 120, 122, 124 over a full angle of 360°. This is due to the joint rotational movement of the laser 130 and the mirror 140. Furthermore, the optical scanner 100 allows the determination of the respective angular position of objects 120, 122, 124, since an angular position in the plane of the imager 152 is uniquely encoded by the joint rotational movement of the laser 130 and the mirror 140.

[0053] If the pixels of the receiving element 152 are sensitive in the visible spectral range, the receiving device 150 can capture a camera image of the respective objects 120, 122, 124 in addition to the distance and angle determination. However, if no camera images of the objects 120, 122, 124 are to be taken, data compression can be performed directly at the receiving device 150, since only a portion of the pixels are relevant for the distance and angle determination.

[0054] Furthermore, it is also possible for the optical scanner 100 to include additional lasers in addition to the laser 130 in order to simultaneously determine multiple distances between different objects 120, 122, 124. Furthermore, by using multiple lasers as a light source, the distance resolution can be improved compared to using a single laser 130. List of reference symbols 100 optical scanners 105 axis of rotation 110, 112, 114 respective distance of an object 120, 122, 124 Object 130 light source, laser 132 transmission signal 134 Displacement distance 140 mirrors 142 Angle of the mirror relative to the axis of rotation 150 reception facility 152 Receiving element, imager 154 aperture, receiving optics 160 Rotating arrow 210, 212 Circle with center on the axis of rotation 220 Reference direction 230, 232 Angle of the object 305 Image reference direction 310, 312 Distance between image position and reference point 311, 313 Circles with the reference point as center 320, 322 Image position 325 Reference point 330, 332 Angle of the imaging position in the plane of the receiving element

Claims

[1] Optical scanner (100) for determining the distance (110, 112, 114) of an object (120, 122, 124) relative to the optical scanner (100), comprising: at least one light source (130) for emitting an optical transmission signal (132), a stationary receiving device (150) which is designed to receive light which is generated by the transmission signal (132) reflected or remitted by an object (120, 122, 124), and a deflection device (140) which deflects light reflected or remitted from the object (120, 122, 124) for imaging onto a receiving element (152) of the receiving device (150), wherein the light source (130) is designed to perform a rotational movement about a common axis (105) together with the deflection device (140), characterized byan evaluation device for determining the distance (110, 112, 114) of the object (120, 122, 124) relative to the optical scanner (100) based on a distance (310, 312) between an imaging position (320, 322) of the object (120, 122, 124) on the receiving element (152) and a reference point (325) on the receiving element (152). [2] Optical scanner (100) according to claim 1, characterized by that a receiving optics (154) is provided between the deflection device (140) and the receiving element (152). [3] Optical scanner (100) according to claim 1 or 2, characterized by that an angular position (230, 232) of the object (120, 122, 124) relative to a predetermined direction (220) can be determined on the basis of an imaging position (320, 322) on the receiving element (152). [4] Optical scanner (100) according to one of the preceding claims, characterized by that the light source (130) is attached to the deflection device (140). [5] Optical scanner (100) according to one of the preceding claims, characterized by that the light source (130) is offset relative to the axis of rotation (105) in a direction perpendicular to the axis of rotation (105). [6] Optical scanner (100) according to one of the preceding claims, characterized by that the light source (130) is inclined by a predefined angle with respect to a horizontal plane which is perpendicular to the axis of rotation (105). [7] Optical scanner (100) according to claim 6, characterized by that the inclination of the light source (130) is adjustable. [8] Optical scanner (100) according to one of the preceding claims, characterized by that the deflection device (140) comprises a mirror. [9] Optical scanner (100) according to claim 8, characterized by that the mirror (140) is designed as a planar mirror. [10] Optical scanner (100) according to claim 9, characterized bythat the mirror (140) is arranged at an angle of 40 to 50 degrees, preferably 45 degrees, relative to the axis of rotation (105). [11] Optical scanner (100) according to one of the preceding claims, characterized by that the light source (130) comprises a laser which illuminates the object (120, 122, 124) in a point-like manner. [12] Method for determining the distance (110, 112, 114) of an object (120, 122, 124) relative to an optical scanner (100), wherein the optical scanner (100) comprises: a light source (130) for emitting an optical transmission signal (132), a stationary receiving device (150) which is designed to receive light which is generated by the transmission signal (132) reflected or remitted by an object (120, 122, 124), and a deflection device (140) which deflects light reflected or remitted from the object (120, 122, 124) for imaging onto a receiving element (152) of the receiving device (150), the method comprising: the light source (130) is rotated together with the deflection device (140) about a common axis (105), characterized by , that the distance (110, 112, 114) of the object (120, 122, 124) relative to the optical scanner (100) is determined based on a distance (310, 312) between an imaging position (320, 322) of the object (120, 122, 124) on the receiving element (152) and a reference point (325) on the receiving element (152), and an angular position (230, 232) of the object (120, 122, 124) relative to a predetermined direction (220) is determined based on the imaging position (320, 322).

Images