EXPANDING A DYNAMIC RANGE OF SPAD-BASED DETECTORS

Abstract

A method for operating a LIDAR device by a control unit is provided. At least one beam pulse is emitted into a sampling range by a beam source, and beams that are reflected and/or back-scattered from the sampling range are received by a detector that includes multiple SPAD cells, and converted into electrical counting pulses. The at least one beam pulse is generated with a lengthened falling intensity edge, and the detector is read out by a DC-coupled readout electronics system. Moreover, a control unit and a LIDAR device are provided.

Claims

1-8. (canceled)

9. A method for operating a LIDAR device by a control unit, the method comprising the following steps: emitting, by a beam source, at least one beam pulse into a sampling range by a beam source; and receiving, by a detector, beams that are reflected and/or back-scattered from the sampling range, the detector including multiple SPAD cells, and receive beings being converted into electrical counting pulses; wherein the at least one beam pulse is generated with a lengthened falling intensity edge, and the detector is read out by a DC-coupled readout electronics system.

10. The method as recited in claim 9, wherein the beam source is operated by the control unit in such a way that the at least one beam pulse is generated with an exponentially or quadratically or linearly, falling intensity edge.

11. The method as recited in claim 9, wherein the readout electronics system is an active or passive avalanche quenching circuit.

12. The method as recited in claim 9, wherein the SPAD cells of the detector are activated with a variably settable active time by the readout electronics system.

13. A control unit for operating a LIDAR device by a control unit, the control unit configured to: emit, by a beam source, at least one beam pulse into a sampling range by a beam source; and receive, by a detector, beams that are reflected and/or back-scattered from the sample range, the detector including multiple SPAD cells, and receive beings being converted into electrical counting pulses; wherein the at least one beam pulse is generated with a lengthened falling intensity edge, and the detector is read out by a DC-coupled readout electronics system.

14. A LIDAR device for sampling a sampling range, comprising: at least one beam source configured to generate electromagnetic beams; at least one detector configured to receive beams that are back-scattered and/or reflected from the sampling range; and a control unit connected to a readout electronics system, the detector being a SPAD array and being connected to the readout electronics system for operating the SPAD array, the control unit being configured to evaluate outputs of the readout electronics system and activate the at least one beam source.

15. The LIDAR device as recited in claim 14, wherein the evaluation electronics system is a DC-coupled evaluation electronics system.

16. The LIDAR device as recited in claim 14, wherein the at least one beam source is activatable by the control unit in such a way that the generated beams are emitted into the sampling range as beam pulses having a lengthened falling intensity edge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows a schematic illustration of a LIDAR device according to one specific embodiment of the present invention.

[0030] FIG. 2 shows a schematic diagram for illustrating a temporal voltage profile of an AC-coupled evaluation electronics system.

[0031] FIG. 3 shows a schematic diagram for illustrating a temporal voltage profile of a DC-coupled evaluation electronics system.

[0032] FIG. 4 shows a schematic diagram for illustrating an adapted intensity profile of a beam pulse.

[0033] FIG. 5 shows a diagram with photons that are received or counted by the detector as a function of time.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0034] FIG. 1 shows a schematic illustration of a LIDAR device 1 according to one specific example embodiment. LIDAR device 1 includes a beam source 2 that is used for generating beams or beam pulses 3.

[0035] Beam source 2 is designed as a laser, and may be electrically activated by a control unit 4 and excited to generate beams 3. Beam source 2 may, for example, generate beams 3 having a wavelength in the infrared, visible, or ultraviolet wavelength range.

[0036] In addition, LIDAR device 1 includes a detector 6. Detector 6 includes a plurality of SPAD cells 8 that are connected to an evaluation electronics system 10. Evaluation electronics system 10 is preferably designed as a DC-coupled evaluation electronics system 10 in which, for example, the DC components of voltage U that is applied to SPAD cells 8 are not filtered out by a capacitor. SPAD cells 8 of detector 6 are flatly situated, and may receive or detect beams 12 that are reflected and/or back-scattered from sampling range A.

[0037] Received beams 12 and in particular photons of received beams 12 are detected in the form of brief current pulses by evaluation electronics system 10 and converted into digital measured data. This step may alternatively or additionally take place in conjunction with control unit 6.

[0038] Due to the use of a DC-coupled evaluation electronics system 10, not only is a so-called count triggered by a received photon, as with an AC-coupled evaluation electronics system, but due to a lengthened active time Z it is also possible to detect, for example, six or more counts per active time.

[0039] FIG. 2 illustrates by way of example voltage U, applied to SPAD cells 8, in an example of an AC-coupled evaluation electronics system. Voltage U required for activating SPAD cells 8 is present only briefly due to the oscillation of voltage U.

[0040] As an alternative, FIG. 3 shows a schematic diagram for illustrating a temporal voltage profile U of DC-coupled evaluation electronics system 10.

[0041] FIG. 3 illustrates two different voltage profiles U that may be applied to SPAD cells 8 to allow detection of photons of received beams 12. Voltage profiles U differ in particular in active time Z, which is variably settable by DC-coupled evaluation electronics system 10.

[0042] In DC-coupled evaluation electronics system 10 the dynamic range is expanded, since the length of the voltage signal or active time Z delivers the information concerning the level of intensity I of a received beam 12. In the AC coupling shown in FIG. 2, after a short time this is no longer possible.

[0043] FIG. 4 shows a schematic diagram for illustrating an adapted intensity profile I of a generated beam pulse 3. In contrast to a Gaussian beam pulse, illustrated intensity profile I of beam pulse 3 has a lengthened falling intensity edge 14. In the illustrated exemplary embodiment, falling intensity edge 14 has an exponentially falling design. For example, after a time t of 30 ns, falling intensity edge 14 may have a remaining intensity I of 1%.

[0044] FIG. 5 shows a diagram with photons that are received or counted by detector 6 as a function of time. In particular, a photon number N is illustrated as a function of time t. A larger photon number N may be detected with increasing time t that is used to detect received beams 12.

[0045] The dynamic range may be described as a range between a minimum detectable photon number N and a maximum detectable photon number N. Expanding the dynamic range allows improved distinguishability of detectable photon number N. For example, due to a larger dynamic range, a smaller detectable photon number N may be distinguished from a larger detectable photon number N. This relationship and the distinguishability are schematically illustrated in FIG. 5.

[0046] The numerical figures in FIG. 5 are provided as an example, and are used solely to illustrate differences.