LiDAR Devices with Accelerated Time-of-Flight Analysis

Abstract

A laser radar device for scanning a scanning area is disclosed, the laser radar device having a transmitting unit and a receiving unit, the transmitting unit being used to generate a beam and to deflect the beam along the scanning area, the receiving unit having at least one detector for receiving a reflected beam, wherein individual sections of the detector can be activated successively at defined time intervals for detecting the reflected beam, or the reflected beam can be deflected to individual sections of the detector at a variable deflection angle by a deflection device. In addition, a control unit and a receiving unit are disclosed.

Description

Technical Field

[0001] The invention relates to a laser radar device for scanning a scanning area, the laser radar device having a transmitting unit and a receiving unit, the transmitting unit being used to generate a beam and to deflect the beam along the scanning area, the receiving unit having at least one detector for receiving the reflected beam. The invention also relates to a control unit and a receiving unit. Background Art

[0002] A laser radar (light detection and ranging) device has a transmitting unit for emitting a beam and a receiving unit for detecting a beam previously reflected in a scanning area. Detectors are used to detect the reflected beams. These reflected beams are usually arranged to determine the propagation time of the arriving beams to the corresponding image points of the detector. For example, photodiodes or CCD sensors can be used as detectors.

[0003] In order to achieve a high depth resolution or range resolution of the detector, it is necessary to read out the detector accordingly quickly and frequently. In this case, the corresponding pixels or diodes can ideally be read out in parallel.

[0004] Until now, CCD sensors could only be used conditionally as detectors, since the readout speed was slow compared to detector arrays, resulting in a limited depth resolution. Summary of the invention

[0005] The object on which the present invention is based can be seen as, in particular, to specify a lidar device which enables a propagation time analysis with the unrestricted use of conventional CCD sensors.

[0006] This object is achieved by means of the respective subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0007] According to one aspect of the present invention, a laser radar device for scanning a scanning area is provided. The laser radar device has a transmitting unit for generating a beam and for deflecting the beam along the scanning area. In addition, the laser radar device has a receiving unit, which has at least one detector for receiving a reflected beam, wherein the individual segments of the detector can be activated successively at defined time intervals to detect the reflected beam, or the reflected beam can be deflected to the individual segments of the detector at a variable deflection angle by a deflection device.

[0008] According to another aspect of the present invention, a control unit for operating a laser radar device is provided, wherein the control unit is configured to control a deflection device of the laser radar device or a detector of the laser radar device. In addition, the control unit can be configured as an analysis unit. Preferably, the control unit can use the signal obtained by the detector for further processing. In particular, the further processing can be carried out in a highly parallel manner and can have a processor (e.g., a GPU or FPGA) working in parallel.

[0009] According to another aspect of the invention, a receiving unit is provided, in particular a receiving unit for a laser radar device, which has a detector, wherein individual segments of the detector can be activated successively at a uniform speed to detect a reflected beam, or individual segments of the detector can be irradiated with the reflected beam by a deflection device with a uniformly varying degree of deflection.

[0010] The laser radar device and the receiving unit used make it possible to steer the beam to different positions on the chip or detector at different times using a deflection device. This makes it possible to dispense with the propagation time analysis in the chip itself, so that fast-moving detectors are not required. In particular, the requirements for the readout speed can be reduced by the laser radar device.

[0011] The propagation time can thus be encoded as a position within the detector, so that a propagation time analysis can be converted into an image analysis. Alternatively or additionally, instead of scanning with the reception beam on the detector or sensor, individual rows of the detector can be switched to activation one after the other.

[0012] Preferably, the beam is deflected across the detector with a constantly changing degree of deflection. As a result, the reflected beam from the smallest distance can be imaged, for example, in an edge section of the detector, and the beam reflected back from the largest distance can be diverted to the opposite edge section. Thus, the entire surface of the detector can be used as an indicator for the different possible propagation times of the reflected beam. Based on the position or section at which the reflected beam is detected, the propagation time of the respective beam can be derived.

[0013] The deflection device can, for example, change the degree of deflection of the incoming beam at a constant speed along the surface of the detector. For example, when emitting a beam, the deflection device can adjust the degree of deflection so that the reflected beam is diverted to an edge section or corner of the detector. As time increases, the degree of deflection continues to change continuously until the time required for the reflected beam to return to the detector from the maximum distance of the laser radar device is reached. The deflection device can then direct the degree of deflection again to the edge of the detector surface. Here, the deflection device can adjust the degree of deflection as desired, thereby diverting the incoming beam to a defined position or section of the detector according to the propagation time of the incoming beam. Here, the deflection of the beam arriving at the detector can be configured in two dimensions along the entire surface of the detector.

[0014] Based on the position of the beam detected at the detector, the propagation time can be assigned in a technically simple manner, so that the detector no longer needs to be completely read out by the evaluation unit. Instead, the identification of the section of the detector that has perceived the beam is sufficient to determine the propagation time of the respective beam and thus the distance.

[0015] The beam can be deflected onto the detector by the action of the deflection device or by corresponding activation and deactivation of individual regions of the detector. By activating and deactivating different sections of the detector, the deflection function of the deflection device can be simulated by controlling individual image points or surface sections of the detector.

[0016] According to one embodiment, at least one detector is configured as a CCD sensor or a detector array. By using a detector array instead of a single detector, the measurement of the incoming beam can be designed to be highly parallel and thus more efficient. In particular, the detector no longer has to be able to be read quickly and frequently to generate a corresponding depth resolution. The depth resolution comes only from the beam motion on the sensor.

[0017] By using CCD sensors or CCD chips, a low-cost and high-resolution alternative to detector arrays can be realized. The CCD sensor can be activated segment by segment or row by row. The activated segment can detect the incoming light or the incoming beam. By changing the activated segment after a defined constant or variable time period, the propagation time can be assigned to the beam to be detected according to the segment in which the incoming beam is detected. In this case, the complete signal or the reflected beam can be imaged on the entire CCD sensor. In this case, the detector pixels can be switched to be sensitive, for example row by row. The advantage of this embodiment is that the deflection device can be omitted.

[0018] According to another embodiment, individual segments of the detector are shaped in a point-like, planar or linear manner, so that the segments can be activated flexibly by the control unit or the evaluation unit.

[0019] For example, this principle can be used to detect an entire laser line (so-called vertical flash). Here, the entire laser line is deflected and thus the propagation time is detected in one direction and the position in the other direction on a two-dimensional sensor. As a result, the principle is designed to be highly parallel and the signals obtained are preferably suitable for further processing in a parallel processor (e.g. GPU or FPGA).

[0020] According to another embodiment, the deflection device is an acousto-optic modulator. Depending on the configuration, the receiving unit may also have a deflection device in addition to the detector. Here, the deflection device may be implemented in different ways. For example, an acousto-optic deflection device, a micromirror or other deflection devices may be used. These deflection devices may preferably be coupled to a control unit and may be controlled by the control unit. The incident light is deflected to one or more selected pixels or selected rows of the detector by the deflection device. Here, the deflection device changes the degree of deflection at a constant speed. As a result, the propagation time of the arriving beam is encoded as a pixel or row position and can then be processed by image processing. Based on the positional distribution of the detected beam on the detector surface, the propagation time can be assigned to the detected beam.

[0021] According to another embodiment, the laser radar device has a control unit, which is connected to the detector and / or the deflection device. The deflection device and / or the detector can thus be actively controlled by the control unit. In particular, a continuous change of the illuminated area or activated area of ​​the detector can be achieved by the control unit.

[0022] According to another embodiment, each segment of the detector can be activated or irradiated at least once within a propagation time interval corresponding to the range of the laser radar device. The achievable depth resolution of the detector solution (or how many different propagation times can be detected) generally depends on the number of detector pixels in the scanning direction along the detector surface and on the scanning frequency. For example, for a laser radar range in the range of about 10 to 200 m, a light propagation time of 0.07 to 1.3 μs can be expected. Therefore, the entire detector can be scanned within this time interval. This means that, according to this example, the deflection device frequency is in the range of about 770 kHz. As a result, non-mechanical deflection devices can preferably be used in laser radar applications. Such deflection devices can be, for example, acousto-optic modulators.

[0023] According to another embodiment, at least two reflected beams offset in time can be detected by different activation sections of the detector or can be diverted by a deflection device to different sections of the detector or can be diverted to the detector one after the other. The repetition rate can thus be reduced at the expense of resolution by detecting multiple signals within one detector revolution. The principle can be freely extended and adapted to the technical specifications. Multiple beams can be diverted in parallel or in an offset manner to different areas of the detector.

[0024] Alternatively or additionally, the generated beam can be emitted successively in pulse form into the scanning region. These beam pulses can be measured within a measuring cycle and can therefore be imaged temporally successively in a scanning manner on a detector.

[0025] A corresponding receiving unit is not limited to lidar devices or lidar applications but can generally be used in all applications in which a propagation time measurement of a beam is carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] A preferred embodiment of the present invention is further described below based on a highly simplified schematic diagram. It is shown here:

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

[0028] Figure 2 A schematic diagram showing a receiving unit according to a first embodiment,

[0029] Figure 3 A schematic diagram of a receiving unit according to a second embodiment is shown, and

[0030] Figure 4 A schematic diagram showing a receiving unit according to a third embodiment is shown. DETAILED DESCRIPTION

[0031] Figure 1 A schematic diagram of a lidar device 1 according to an exemplary embodiment is shown. The lidar device 1 has a transmitting unit 2 and a receiving unit 4 .

[0032] The transmission unit 2 is used to generate and emit a beam 6 along a scanning area A. For example, the generated beam 6 can be configured as a laser beam. For this purpose, the transmission unit 4 has a laser, which is not shown for simplicity. The transmission unit 2 can generate and emit the beam 6 at a defined pulse frequency. This can be coordinated and activated by the control unit 8.

[0033] The receiving unit 4 has a detector 10 and a deflection device 12 . A reflected beam 14 which reaches the receiving unit 4 or is in the scanning area A is deflected by the receiving unit 4 onto the deflection device 12 .

[0034] Deflection device 12 is designed as an acousto-optic modulator and is controlled by control unit 8. By deflection device 12, incoming beam 14 is deflected onto continuously changing sections of detector 10, so that a propagation time analysis can be performed based on the position of detected beam 14 on detector 10.

[0035] exist Figure 2 A schematic diagram of a receiving unit 4 according to a first exemplary embodiment is shown in . The degree of deflection of the impinging beam 14 caused by the deflection device 12 changes at a constant speed.

[0036] For the sake of clarity, the detector 10 is shown as a line detector in order to illustrate the principle of operation. However, the detector 10 is not limited to this exemplary embodiment.

[0037] Since the deflection degree of the arriving beam 14 varies with time, the time required for the arrival of the beam 14 can be assigned to each detector segment 16 starting from the time point t0 of the beam generation. According to this example, the segments 16 of the detector 10 are configured as detector pixels. Thus, the first detector pixel corresponds to the time point t1, which corresponds to the shortest propagation time of the beam 14 and thus to the shortest measurable distance. Accordingly, all detector pixels 16 are connected with propagation times t1 to t N The encoding takes place so that the propagation time can be determined depending on which detector pixel 16 detects the incoming beam 14 .

[0038] According to this embodiment, the incident light or beam 14 can be deflected by the deflection device 12 depending on the propagation time of the light 14. Thus, depending on the propagation time, the light strikes different pixels 16 of the detector 10. The propagation time can then be derived from the intensity distribution.

[0039] Figure 3 A schematic diagram of a receiving unit 4 according to a second exemplary embodiment is shown. In contrast to the first exemplary embodiment, the receiving unit 4 has an incoming beam 14 in the form of a vertical laser line which is deflected by a deflection device 12 onto the detector 10 .

[0040] The detector 10 can be designed as a CCD sensor. The beam 14 is deflected as a vertical line onto a segment 18 of the detector 10. The segment 18 is designed as a line of the detector 10, so that the line 18 is assigned time information or a respective propagation time t1 to t N The corresponding columns x1 to x N Can be used for additional functions. For example, travel times and different positions can be detected in parallel.

[0041] Figure 4 A schematic diagram of a receiving unit 4 according to a third exemplary embodiment is shown. In contrast to the exemplary embodiments already described, different sections 17 , 18 , 19 of the detector 10 are activated or deactivated again by the control unit 4 sequentially or in parallel with one another.

[0042] This can be implemented as an extension of the second exemplary embodiment. The difference is that the deflection device 12 images the first pulse onto the detector 10 in the time period t1 to t3 and then continues the scan instead of returning to the beginning of the detector 10. As a result, the second pulse and respectively the third pulse can be imaged onto the detector 10 in the subsequent region.

[0043] According to this exemplary embodiment, the sensor array or detector 10 is subdivided to detect a plurality of beams 14, 20, 22. In this case, the temporal resolution of each individual pulse 14, 20, 22 is reduced to one third, but the necessary deflection frequency is also reduced, for example, from 770 kHz to 256 kHz. Thus, three signals 14, 20, 22 can be detected simultaneously in the detector image. For each signal 14, 20, 22, a plurality of segments 17, 18, 19 are available, which are encoded with corresponding propagation times t1 to t3.

Claims

1. A laser radar device (1) for scanning a scanning area (A), the laser radar device having a transmitting unit (2) for generating a beam (6) and for deflecting the beam (6) along the scanning area (A), and the laser radar device having a receiving unit (4) having at least one detector (10) for receiving a reflected beam (14), characterized in that: The individual segments (16, 18) of the detector (10) can be activated successively at defined time intervals to detect the reflected beam (14), or the reflected beam (14) can be deflected by a deflection device (12) at a variable deflection angle onto the individual segments (16, 18) of the detector (10), wherein the individual segments (16, 18) of the detector (10) are configured as detector pixels, wherein the time required for the reflected beam (14) is allocated to the individual segments (16, 18) of the detector (10) starting from the time of beam generation, so that a propagation time is determined depending on which detector pixel detects the reflected beam (14), wherein the propagation time can be allocated to the detected reflected beam (14) based on the position distribution of the detected reflected beam (14) on the detector surface.

2. The laser radar device according to claim 1, wherein: The at least one detector (10) is configured as a CCD sensor or a detector array.

3. The laser radar device according to claim 1 or 2, wherein: The individual sections (16, 18) of the detector (10) are shaped in a point-like, planar or linear manner.

4. The laser radar device according to claim 1 or 2, wherein: The deflection device (12) is an acousto-optic modulator.

5. The laser radar device according to claim 1 or 2, wherein: The laser radar device (1) has a control unit (8) which is connected to the detector (10) and / or the deflection device (12).

6. The laser radar device according to claim 1 or 2, wherein: In the propagation time interval (t1-t2) corresponding to the effective range of the laser radar device (1), N ), each segment (16, 18) of the detector (10) can be activated or irradiated at least once.

7. The laser radar device according to claim 1 or 2, wherein: At least two reflected beams (14, 20, 22) offset in time can be detected by different activation sections (17, 18, 19) of the detector (10), or can be deflected by the deflection device (12) to different sections (17, 18, 19) of the detector (10) or can be deflected successively to the detector (10).

8. A control unit (8) for operating a lidar device (1) according to any one of the preceding claims, wherein: The control unit (8) is configured to control a deflection device (12) of the laser radar device (1) or a detector (10) of the laser radar device (1).

9. A receiving unit (4) for a laser radar device (1) according to any one of claims 1 to 7, the receiving unit having a detector (10), wherein: The individual segments (16, 18) of the detector (10) can be activated successively at a uniform speed to detect the reflected beam (14), or the individual segments (16, 18) of the detector (10) can be irradiated with the reflected beam (14) by a deflection device (12) with a varying degree of deflection, wherein the individual segments (16, 18) of the detector (10) are configured as detector pixels, wherein the time required for the reflected beam (14) is allocated to the individual segments (16, 18) of the detector (10) starting from the time of generation of the beam (6), so that a propagation time is determined depending on which detector pixel detects the reflected beam (14), wherein the propagation time can be allocated to the detected reflected beam (14) based on the positional distribution of the detected reflected beam (14) on the detector surface.

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