LIDAR Device, System and Method

Abstract

A light detection and ranging (LIDAR) device having a sensor for detecting input signals and an emitter for emitting output signals. A controller controls the emitter to emit output signals and reads the input signals from the sensor during a plurality of scan cycles. Each scan cycle is separated by a spacer period, and the controller is configured to vary the length of the spacer periods between the plurality of scan cycles. The LIDAR device may form part of a LIDAR system. Methods for reducing interference in a LIDAR system, and methods and software for controlling a LIDAR device are also disclosed.

Claims

1. A light detection and ranging (LIDAR) device comprising: a sensor configured to detect input signals; an emitter configured to emit output signals; and a controller configured to control the emitter to emit the output signals and control the sensor to read the input signals during a plurality of scan cycles, each scan cycle being separated from another scan cycle by a spacer period, the controller configured to vary a length of spacer periods between the plurality of scan cycles.

2. The LIDAR device according to claim 1, wherein the controller is configured to set the length of each spacer period to be within a predetermined range.

3. The LIDAR device according to claim 2, wherein the predetermined range has at least one of: a minimum spacer period above approximately 5 nanoseconds (ns); or a maximum spacer period of approximately 100 (ns).

4. The LIDAR device according to claim 1, wherein the controller is configured to set the length of each spacer period to be different from the length of at least one adjacent spacer period.

5. The LIDAR device according to claim 1, wherein the controller is configured to randomly set the length of each spacer period.

6. The LIDAR device according to claim 1, wherein the controller is configured to pseudo-randomly set the length of each spacer period.

7. The LIDAR device according to claim 1, wherein: the sensor comprises an array of pixels arranged in a plurality of lines; and the controller is configured to read each line of the plurality of lines non-sequentially.

8. The LIDAR device according to claim 7, wherein the controller is configured to: randomly generate a line read order for each scan cycle; and read input signals from individual lines of the plurality of lines based on the line read order.

9. The LIDAR device according to claim 7, wherein each line of the plurality of lines comprises at least one of a row or a column.

10. The LIDAR device according to claim 1, wherein the sensor comprises a Single-Photon Avalanche Diode (SPAD) array.

11. The LIDAR device according to claim 1, wherein the LIDAR device comprises an automotive LIDAR device.

12. A method for controlling at least one LIDAR device, the method comprising: driving a plurality of scan cycles in which output signals from an emitter are coordinated with reading input signals from a sensor; separating each scan cycle by a spacer period; and varying a length of spacer periods between the plurality of scan cycles.

13. The method according to claim 12, further comprising: accumulating time of flight data for detected input signals over the plurality of scan cycles for the at least one LIDAR device; and noise filtering the accumulated time of flight data.

14. The method according to claim 12, further comprising: controlling a respective emitter and sensor of each LIDAR device of a plurality of LIDAR devices to perform a respective plurality of scan cycles, each scan cycle being separated by a spacer period; and varying the length of the spacer periods of the at least one LIDAR device of the plurality of LIDAR devices such that the plurality of scan cycles for each of the plurality of LIDAR devices are out of phase with respect to each other.

15. The method according to claim 12, further comprising: setting the length of each spacer period to be different from the length of at least one adjacent spacer period.

16. The method according to claim 12, further comprising: setting the length of each spacer period at least one of randomly or pseudo-randomly.

17. The method according to claim 12, further comprising: non-sequentially reading each line of a plurality of lines of an array of pixels of the sensor.

18. A light detection and ranging (LIDAR) device comprising: a sensor comprising an array of pixels arranged in a plurality of lines, each line of pixels configured to detect input signals; and a controller configured to read the input signals from each line of pixels, the controller configured to read each line of the plurality of lines non-sequentially.

19. The LIDAR device according to claim 18, wherein the controller is configured to: randomly generate a line read order for each scan cycle of a plurality of scan cycles; and read the input signals from individual lines of the plurality of lines based on the line read order.

20. The LIDAR device according to claim 18, wherein each line of the plurality of lines comprises at least one of a row or a column of the array of pixels of the sensor.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] Illustrative embodiments will now be described with reference to the accompanying drawings in which:

[0027] FIG. 1 shows accumulated histogram counts of a single SPAD pixel over time;

[0028] FIG. 2A shows an isometric view of a scanning LIDAR architecture;

[0029] FIG. 2B shows an isometric view of a flash LIDAR architecture;

[0030] FIG. 3 shows a schematic illustration of an automotive LIDAR system according to an illustrative embodiment;

[0031] FIG. 4A shows a schematic illustration of a scanning sequence according to the illustrative embodiment;

[0032] FIG. 4B shows a schematic illustration of an illustrative scenario where a parasitic signal is present during an illustrative scanning sequence; and

[0033] FIGS. 5A and 5B show schematic illustrations of a detector matrix array readout order according to a second illustrative embodiment.

DETAILED DESCRIPTION

[0034] FIG. 3 shows a schematic illustration of an automotive vehicular LIDAR system 3 according to an illustrative embodiment. The LIDAR system 3 includes a plurality of LIDAR devices 31-34 mounted around the vehicle, with devices mounted on the front 37 and rear 39 as well as the side wing mirrors 38. Each of the LIDAR devices 31-34 includes an emitter 30a, a sensor 30b, and a controller 30c (as shown with respect to the LIDAR device 31). The system 3 also includes an electronic control unit 35 connected through a network of wiring 36 to each of the LIDAR devices.

[0035] It will be understood that different arrangements of LIDAR devices may be employed. For example, depending on the vehicle and system requirements, LIDAR devices may be mounted to the vehicle in different locations or alternative configurations.

[0036] In use, the controller 30c of each LIDAR device 31-34 controls its respective emitter 30a to emit a series of output signals or light pulses for illuminating the field of view of the respective LIDAR device. At the same time, the controller 30c synchronises the reading of detected reflected light onto the sensor 30b with the output light pulses. As such, each LIDAR device performs a plurality of scan cycles in which it emits an output light pulse and reads the reflected light as an input signal to determine ToF data. As described above in reference to FIG. 1, the ToF data accumulated over a plurality of scan cycles is used to calculate the distance between each LIDAR device and objects in its respective field of view.

[0037] As is described in further detail below, the controllers 30c of each LIDAR device are configured to apply variable length spacer periods between each scan cycle. That is, after each scan cycle, the controller applies a variable period in which no scanning occurs. This thereby acts to shift the timing window of the next scan cycle so that the position of the timing windows do not follow a consistent frequency. As such, both the synchronised emit and read operations associated with each cycle are time shifted. In this embodiment, the controller is configured to vary the duration of the spacer periods randomly within a predetermined range. It will be understood that in other embodiments, the controller may alternatively apply a pseudo random sequence of spacer periods.

[0038] To explain the above further, FIG. 4A illustrates a scanning sequence of three consecutive scan cycles 41a-c that take place over time t. Whilst the scan cycles 41a-c have the same duration, they are separated by spacer periods 42,43 which vary in length. In this illustrated example, the spacer period 42 between the first and second scan cycles is significantly less than spacer period 43 between the second and third. It will be understood that the pattern of scan cycles spaced by periods of different durations will continue for a plurality of further cycles.

[0039] FIG. 4B shows a schematic illustration of an illustrative scenario where a parasitic signal having a regular pulse frequency is present during an illustrative scanning sequence. In this example, three consecutive scan cycles are shown, illustrated by timing windows 44a-c associated with the LIDAR device's sensor 30b. The scan cycles are separated again by spacer periods 45,46 which vary in length. As shown in the timing windows 44a-c, a first peak 47a-c appears at the same point in each timing window and hence can be identified as a signal of interest in that it corresponds to the output light pulse being reflected back from a detected object a set distance away from the sensor 30b.

[0040] In contrast, the parasitic signal arising from another LIDAR device will produce a peak 48a-d which varies its position relative to each timing window 44a-c. That is, as the controller varies the length of each spacer period 45,46, the timing windows 44a-c are shifted relative to any externally generated signals. This shifting does not affect the target signal because this remains synchronised with the timing window 44a-c itself. Over time, the peaks 48a-d associated with the parasitic signal stemming from an interfering sensor are shifted across the timing window and in some instances arise outside the window. As such, they are effectively pushed out of the timing window. In this respect, it can be seen that in this example, the third parasitic peak 48c is completely outside of the timing windows 44a-c. In this way, when the sensor signals are accumulated within the histogram count, the parasitic signals are spread throughout the different time bins such that the they are perceivable only as an increased noise floor, rather than appearing as high intensity peaks. This noise may be filtered using conventional noise filtering within the controllers 30c or the electronic control unit 35. The above-described devices and system thereby provide for interference generated by parasitic signals to be mitigated in both scanning and flash LIDAR architectures.

[0041] FIGS. 5A and 5B are used to describe a second embodiment of the invention, which operates to further mitigate interference in scanning LIDAR architectures. In this embodiment, in addition to the controller 30c varying the spacer periods between scan cycles, the controller 30c further randomises the scanning order of both the emitter 30a and the corresponding pixel lines on the sensor 30b within the LIDAR devices 31-34. That is, the sensor 30b includes an array of pixels arranged in a matrix having a plurality of rows and columns 50a-50n, as shown in FIG. 5A. In this embodiment, the controller 30c is configured to read each of the plurality of columns non-sequentially during each scan cycle, with the corresponding column in the field of view being illuminated by the emitter 30a. For this, the controller may generate a randomised read order for each scan cycle, or may apply a pseudo random read order, for the columns. For instance, FIG. 5A shows a first cycle, where the image frame is scanned beginning with the column on the far right.

[0042] FIG. 5B shows a read order for a second cycle where the image frame is scanned beginning with the column on the left. As such, the read order changes in each scan cycle. Accordingly, parasitic signals arising from interfering sensors within the LIDAR system as a whole are strongly mitigated. This is because the probability that the specific part of the sensor 30b is being actively read at the same time as an interfering signal is received on that portion of the sensor is decreased. That is, even in the presence of an interfering signal, the chances of this being synchronised with the scanning read order is reduced and, even where interfering signals are captured, the randomisation means that their accumulation in the histogram count will merely increase the noise level.

[0043] In this second embodiment, the variable read out order method is applied in combination with the variable spacer period method employed in the first embodiment. However, it will be understood that the variable read out order method may be used independently of the variable spacer period method in some arrangements.

[0044] With the above, an improved LIDAR device and associated methods may be provided, either alone or as part of a LIDAR system which includes a plurality of LIDAR devices. In particular, the problem of parasitic signals originating from other LIDAR devices interfering with signals of interest may be mitigated. This thereby allows for a more accurate system and method of LIDAR imaging.

[0045] It will be understood that the embodiments illustrated above show applications only for the purposes of illustration. In practice, embodiments may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

[0046] For example, it will be understood that embodiments may be implemented in combination with other monitoring systems, such as camera-based systems. In such arrangements, a camera may be directed to a corresponding or overlapping field of view as an associated LIDAR device(s). The feeds from both devices may be combined to, for example, provide a video feed augmented with distance and other LIDAR derived information.

Example Implementations

[0047] Example 1: A LIDAR device comprising: a sensor for detecting input signals; an emitter for emitting output signals; a controller for controlling the emitter to emit output signals and for reading the input signals from the sensor during a plurality of scan cycles, wherein each scan cycle is separated by a spacer period and the controller is configured to vary the length of the spacer periods between the plurality of scan cycles.

[0048] Example 2: A LIDAR device according to example 1, wherein the controller is configured to set the length of each spacer period within a predetermined range.

[0049] Example 3: A LIDAR device according to example 2, wherein the predetermined range has a minimum spacer period above 5 ns and/or a maximum spacer period of 100 ns.

[0050] Example 4: A LIDAR device according to any preceding example, wherein the controller is configured to set the length of each spacer period to be different from the length of adjacent spacer periods.

[0051] Example 5: A LIDAR device according to any preceding example, wherein the controller is configured to randomly set the length of each spacer period.

[0052] Example 6: A LIDAR device according to any preceding example, wherein the sensor comprises an array of pixels arranged in a plurality of lines and wherein the controller is configured to read each of the plurality of lines non-sequentially.

[0053] Example 7: A LIDAR device according to example 6, wherein the controller is configured to randomly generate a line read order for each scan cycle, and wherein the controller is configured to read input signals from individual ones of the plurality of lines based on the line read order.

[0054] Example 8: A LIDAR device according to any preceding example, wherein the sensor is a Single-Photon Avalanche Diode, SPAD, array.

[0055] Example 9: A LIDAR system comprising: a plurality of LIDAR devices, each comprising an emitter for emitting output signals and a sensor for detecting input signals; one or more controllers for controlling each of the plurality of LIDAR devices to control their respective emitter and sensor during a plurality of scan cycles, where each scan cycle is separated by a spacer period; and wherein the one or more controllers vary the length of the spacer periods of least one of the LIDAR devices such that the plurality of scan cycles for each of the plurality of LIDAR devices are out of phase.

[0056] Example 10: A LIDAR system according to example 9, wherein the LIDAR system is an automotive LIDAR system.

[0057] Example 11: A method for reducing interference in a LIDAR system, the method comprising: controlling a respective emitter and sensor of each of a plurality of LIDAR devices to perform a respective plurality of scan cycles, where each scan cycle is separated by a spacer period; and varying the length of the spacer periods of least one of the LIDAR devices such that the plurality of scan cycles for each of the plurality of LIDAR devices are out of phase.

[0058] Example 12: A method according to example 11, further comprising the step of: accumulating time of flight data for detected input signals over the plurality of scan cycles for each of the plurality of LIDAR devices; and noise filtering the accumulating time of flight data.

[0059] Example 13: A method for controlling a LIDAR device, the method comprising: driving a plurality of scan cycles in which output signals from an emitter are coordinated with the reading input signals from a sensor; separating each scan cycle by a spacer period; and varying the length of the spacer periods between the plurality of scan cycles.

[0060] Example 14: A computer program product comprising instructions which, when executed by a computer, cause the computer to control a LIDAR device carry out the steps of: driving a plurality of scan cycles in which output signals from an emitter are coordinated with the reading input signals from a sensor; separating each scan cycle by a spacer period; and varying the length of the spacer periods between the plurality of scan cycles.

[0061] Example 15: A LIDAR device comprising: a sensor comprising an array of pixels arranged in a plurality of lines, each for detecting input signals; and a controller for reading the input signals from each line of pixels, wherein the controller is configured to read each of the plurality of lines non-sequentially.

[0062] The use of “example,” “advantageous,” and grammatically related terms means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” Items represented in the accompanying figures and terms discussed herein may be indicative of one or more items or terms, and thus reference may be made interchangeably to single or plural forms of the items and terms in this written description. The use herein of the word “or” may be considered use of an “inclusive or,” or a term that permits inclusion or application of one or more items that are linked by the word “or” (e.g., a phrase “A or B” may be interpreted as permitting just “A,” as permitting just “B,” or as permitting both “A” and “B”), unless the context clearly dictates otherwise. Also, as used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. For instance, “at least one of a, b, or c” can cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, c-c-c, or any other ordering of a, b, and c).