Apparatus and method for encoding and capturing information about the signal shape

Abstract

According to various aspects, a detection device (100) may comprise: a processing circuit (102) configured to: receive a detection signal (106) representing a received signal (108) detected at the detection device (100), wherein the received signal (108) is associated with a corresponding predefined transmitted signal (122) and / or with one or more expected signal characteristics; generate a differentiation signal (110) representing a rate of change of a signal level of the detection signal (106) over time; determine times (112) corresponding to a change of a sign of the differentiation signal (110); and encode the determined times (112) to generate an output signal (106) representative of one or more characteristic properties of the received signal (108) detected by the detection device (100).

Description

[0001] This application claims priority from application No. DE 10 2022 127 081.5 filed on October 17, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Various aspects relate to a detection device suitable for detecting and reconstructing a signal, as well as to corresponding methods (e.g., a method for performing the signal detection and reconstruction).

[0003] In general, direct time-of-flight systems measure the distance between a detector and an object based on the time difference between the emission of a light pulse and the return of its echo(es) to the detector. Direct time-of-flight systems are often implemented using a time-to-digital converter (TDC), which digitally represents the time between the emission of a light pulse (associated with a start signal) and the detection of its echo (associated with a stop signal). Due to the simplicity of this approach, TDC-based systems typically do not provide information about the shape (or amplitude) of the received pulse. However, this information would be beneficial for improving detector performance and unlocking new features.

[0004] There are solutions for sampling the full waveform to determine amplitude and pulse shape, mostly in the field of LIDAR (Light Detection and Ranging). However, these typically require a high-speed analog-to-digital converter (ADC) and a powerful processing stage, both of which are expensive and result in high power consumption, making this option prohibitive for mobile devices and / or consumer market applications. An example approach involves a multitude of N comparators, each connected to an independent TDC stage, but this results in a significant number of hardware components (to illustrate, the higher the number of comparators, the greater the number of TDCs).

[0005] The present disclosure relates to an improved signal processing scheme based on analyzing the temporal rate of change of an acquired signal to simply yet accurately derive relevant signal information (e.g., shape information, amplitude information) that would otherwise be lost in a conventional TDC approach. Analyzing the rate of change over time can provide an efficient coding scheme for identifying and characterizing relevant parts of the acquired signal without requiring complex and costly hardware components.

[0006] From various perspectives, the improved signal acquisition scheme can be based on derivatives (e.g., first- and / or second-order derivatives) of the acquired signal. This has the advantage that important information about the pulse shape, such as the number and position of peaks in the echo, which is of greatest interest, is captured more accurately and encoded more efficiently. Furthermore, because the information about the derivatives is processed independently, easier access to the relevant information about the pulse shape (e.g., the number and position of peaks) is possible, so that the required signal processing can be further minimized. The configuration described here allows for a simplification of the overall design of the acquisition device and the use of fewer components overall compared to a conventional full-waveform sampling approach.

[0007] In the context of time-of-flight measurements, for example, the additional information can be beneficial to estimate the reflectivity or other surface properties of an object (e.g., by measuring or estimating the pulse amplitude). The additional information can also be used for multiple-echo detection to distinguish between objects at different distances within the field of view (e.g., including transparent objects such as glass with partial reflections). As a further example, the additional information can be used for signal averaging and advanced signal processing purposes, e.g., for tracking error compensation (e.g., based on the echo peak), for detecting spurious signals and crosstalk suppression (e.g., or correlation receiver concepts), or for other downstream processing steps such as object detection, object tracking, and sensor fusion stages (e.g.,by detecting object edges or the inclination of the object, both of which can be derived from the received signal pulse shape).

[0008] The present disclosure is therefore based on the finding that the analysis of the temporal rate of change of a detected signal offers a direct and resource-efficient way to derive or estimate various signal properties, e.g., in connection with TDC-based detection, which properties can then be used for further processing purposes.

[0009] The most relevant use case for the approach described here is time-of-flight systems, e.g., in the context of LIDAR detection, since rate-of-change analysis can be easily integrated into a time-of-flight detector or LIDAR device without requiring modification of the underlying circuitry. Furthermore, signal reconstruction capabilities can enhance time-of-flight detection by providing information about signal properties that would not be derivable using a simple direct time-of-flight detector. Therefore, some aspects are described below with a particular focus on time-of-flight detection and LIDAR devices. However, the approach described here is not limited to time-of-flight or LIDAR applications, but can generally be implemented in any scenario where a temporal signal is digitized for processing.Other example applications may include radar detectors, sound wave-based detectors, motion detectors, and the like.

[0010] In general, the present disclosure relates to an adapted processing scheme for processing a detected signal. The type of detected signal may vary, as long as the signal is provided in a form that enables the processing described herein. Various aspects described below relate in particular to light signals (e.g., for time-of-flight or LIDAR applications), but it is understood that the adapted signal processing can in principle also be applied to other types of signals, such as radio waves, audio signals, position tracking, etc., with an adaptation of the way the signal is originally detected and generated.

[0011] According to various aspects, a detection device may include: a processing circuit configured to: receive a detection signal representative of a receive signal detected at the detection device, wherein the receive signal is associated with a corresponding predefined transmit signal and / or is associated with one or more expected signal characteristics; generate a differentiation signal representative of a rate of change of a signal level of the detection signal over time; determine times corresponding to a change of a sign of the differentiation signal; and encode the determined times to generate an output signal representative of one or more characteristic properties of the receive signal detected at the detection device.

[0012] According to various aspects, a detection device may include: a processing circuit configured to: receive a detection signal representative of a receive signal detected at the detection device, the receive signal being associated with a corresponding predefined transmit signal; generate a differentiation signal representative of a rate of change of a signal level of the detection signal over time; determine times corresponding to a change of a sign of the differentiation signal; and encode the determined times to generate an output signal representative of one or more characteristic properties of the receive signal detected at the detection device.

[0013] According to various aspects, a detection device may include: a processing circuit configured to: receive a detection signal representing a received signal detected at the detection device; generate a differentiation signal representing a rate of change of a signal level of the detection signal over time; determine times corresponding to a change of a sign of the differentiation signal; and encode the determined times to generate an output signal representing one or more characteristic properties of the received signal detected at the detection device.

[0014] The present disclosure may be based on the recognition that times at which the differentiation signal changes sign may correspond to temporal positions within the detection signal of one or more characteristic portions of the detection signal (e.g., peaks, valleys), such that the identification of such times may provide a direct yet reliable approximation to a waveform of the detection signal (and accordingly, the signal detected by the detection device), which may then enable the derivation or estimation of various properties of the signal.

[0015] According to various aspects, a method for performing signal detection may comprise: generating a differentiation signal representative of a rate of change of a signal level of a detection signal over time, wherein the detection signal is representative of a detected receive signal, wherein the receive signal is associated with a corresponding predefined transmit signal and / or is associated with one or more expected signal features; determining times corresponding to a change of a sign of the differentiation signal; and encoding the determined times to generate an output signal representative of one or more characteristic properties of the detected receive signal.

[0016] The approach described here can therefore be based on characterising a signal acquired at a sensing device in a simple way by analyzing the rate of change of the signal level over time and combining the information obtained with an ‘a priori’ knowledge of expected features or properties of the acquired signal in order to perform a simple but accurate reconstruction of the signal shape and enable further processing.

[0017] In a preferred configuration, the processing circuitry may be configured to differentiate the detection signal in an analog manner (e.g., using an analog differentiator). Using an analog differentiator to generate a signal representative of the rate of change provides a simple implementation, allowing operation of the detection device without expensive high-speed analog-to-digital converters for sampling the signal. The analog implementation may be particularly advantageous in the context of TDC-based detection, e.g., for direct time-of-flight measurements, as it allows maintaining a cost-effective overall configuration for the detector.

[0018] According to various aspects, the processing circuitry may be further configured to determine (e.g., calculate or measure) a time-of-flight associated with the received signal, e.g., based on knowledge of a transmission time of a corresponding transmitted signal. The processing circuitry may be configured to use the additional information obtained by analyzing the rate of change of the detected signal to refine the time-of-flight measurement, e.g., to adjust the determined value, to eliminate interference, and the like. The approach described here may thus provide an efficient way to obtain information that can be used to adjust a time-of-flight measurement, e.g., a TDC-based direct time-of-flight measurement.

[0019] According to various aspects, a time-of-flight detector may comprise: a processing circuit configured to: receive a start signal representative of a start time of emission of a transmission signal; receive a detection signal representative of a reception signal detected at the time-of-flight detector, wherein the reception signal includes a (direct) reflection of the transmission signal toward the time-of-flight detector; generate a stop signal representative of an arrival time of the reception signal at the time-of-flight detector; perform a time-to-digital conversion to calculate a time of flight associated with the transmission signal based on the start signal and the stop signal; generate a differentiation signal representing a rate of change of a signal level of the detection signal over time; determine times corresponding to a change of a sign of the differentiation signal;and modifying a value of the calculated term based on the determined points in time;

[0020] As mentioned above, conventional implementations attempt to capture the pulse shape using an array of comparators in conjunction with a TDC and then derive information about the pulse properties from the captured temporal pulse shape, e.g., by "fitting" a mathematical representation of the expected pulse shape to the acquired data. An example of this approach is described in DE 10 2021 101 790 A1. However, in many cases, only certain aspects of the pulse shape are important, e.g., the peak of the pulse or other characteristic points.The present disclosure may therefore be based on the recognition that it is not necessary to acquire the complete pulse shape data, but that directly acquiring only the timing of these characteristic points not only increases accuracy but also greatly simplifies data post-processing, and that such direct acquisition can be easily realized by determining the temporal rate of change of the acquired signal. For example, for signal reconstruction (and for time-of-flight measurement), it may be sufficient to identify the peaks of the acquired signal without having to sample every point of the signal waveform, as in a conventional approach.

[0021] The strategy described here may be based on converting (analog) acquired signals prior to encoding. In some aspects, the processing circuitry may be configured to derive derivatives (or approximations) of the acquired signal and use them as a more appropriate representation and as a basis for subsequent signal encoding steps. For example, the processing circuitry may be configured to use the first and / or second derivatives as the basis for signal encoding. Depending on the implementation objective, the first and / or second derivatives may be chosen to efficiently capture the relevant information about the pulse shape. For example, if the number and position of the peak(s) in the echo are of utmost importance, the first derivative may be determined, and the processing circuitry may search for zero crossings in the signal.Since the leads themselves can be coded, the approach described here provides easier access to the relevant information and thus allows minimizing the required signal processing that normally follows signal acquisition.

[0022] The derivative-based strategy thus provides a simple means of acquiring pulse shape information, which can improve the overall performance of the acquisition device, for example, to compensate for runout error and improve the accuracy of time-of-flight measurements. This additional information can enable new features, such as providing information about the detected object based on the pulse shape, the ability to differentiate between objects, the possibility of edge detection, etc. Furthermore, the entire acquisition device can retain the advantages of a TDC-based approach, such as a simple system design that reduces the number of expensive components while being suitable for high-speed implementations. Compared to full-waveform sampling solutions, a high-speed ADC is not required, which has a beneficial impact on power consumption and cost.Given the event-based nature of TDC detection techniques, the amount of data generated is relatively small. This means less data needs to be processed (e.g., less CPU load is generated) and therefore less CPU power is required, which in turn reduces power consumption and system costs.

[0023] In the drawings, like reference characters generally refer to the same parts throughout the several views. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the principles of the present disclosure. In the following description, various aspects are described with reference to the following drawings, in which: Fig. 1A to Fig. 1C each show a detection device in a schematic view according to different aspects; Fig. 2A to Fig. 2F illustrate various aspects of the operation and configuration of a processing circuit of a sensing device in a schematic view according to various aspects; Fig. 3 shows a series of diagrams illustrating exemplary operation of a sensing device and processing circuitry of the sensing device according to various aspects; Fig. 4A and Fig. 4B each show a detection device in a schematic view, according to various aspects; Fig. 5A and Fig. 5B each show an analog part of the processing circuit of a detection device in a schematic view, according to various aspects; Fig. 5C to Fig. 5G illustrate various aspects of the operation of the processing circuitry of a sensing device according to various aspects; Fig. Figure 6 shows a time-to-digital converter circuit in schematic representation corresponding to various aspects; and Fig. 7 shows a LIDAR system with a detection device according to various aspects.

[0024] The following detailed description refers to the accompanying drawings, which, for illustrative purposes, show specific details and implementations in which the aspects disclosed herein may be practiced. These aspects are described in sufficient detail to enable those skilled in the art to practice the disclosed implementations. Other aspects may be used, and structural, logical, and electrical changes may be made without departing from the scope of the disclosed implementations. The various aspects are not necessarily mutually exclusive, as some aspects may be combined with one or more other aspects to form new aspects. Various aspects are described in the context of methods, and various aspects are described in the context of devices (e.g., a sensing device, a processing circuit, a time-of-flight detector, etc.).However, it is understood that aspects described in connection with methods may similarly apply to the devices, and vice versa.

[0025] The figures contain various diagrams depicting different signals and waveforms. It is understood that the signals and waveforms depicted in the figures are for illustrative purposes only, and the various signals and waveforms may vary depending on the application, the type of signal, the environmental scenario, etc.

[0026] Fig. 1A shows a detection device 100 in a schematic view according to various aspects. The detection device 100 may generally be configured to perform the detection and processing of a temporal signal, e.g., it may be configured to digitize a temporal signal and perform digital processing of the digitized signal. In a preferred configuration, the detection device 100 may be a time-of-flight detector (see also Fig. 1B and Fig. 1C), e.g., for use in a LIDAR system (see Fig. 7). In an exemplary application scenario, the detection device 100 can be integrated into a vehicle (e.g., a vehicle capable of at least partially autonomous driving, e.g., an electric car) or into an interior monitoring system.

[0027] The detection device 100 may include a processing circuit 102 configured to perform the customized signal processing described herein (). By way of example, the processing circuit 102 may be configured to perform a customized method 104 for signal detection and processing. Various references herein to the operation of the processing circuit 102 may be understood as corresponding method steps of the method 104, and vice versa.

[0028] The processing circuit 102 may be configured to receive a detection signal 106 s(t) representative of a signal 108 detected by the detection device 100. The detection signal 106 may represent the signal 108 received by the detection device 100 in a format that enables processing by the processing circuit 102. In general, the detection signal 106 may be a digital signal or an analog signal, depending on the configuration of the processing circuit 102. In a preferred configuration, the detection signal 106 processed by the processing circuit 102 may be an analog signal (e.g., a voltage or current encoding information in an analog manner) to enable a simpler implementation of the processing circuit 102. The signal 108 detected by the detection device 100 may also be referred to herein as a received signal, received signal, or detected signal.Hereinafter, references to properties of the detection signal 106 (e.g., with respect to the waveform, the signal level, etc.) may apply correspondingly to the receive signal 108 representing the detection signal 106, and vice versa.

[0029] According to various aspects, the detection device 100 may include a detector 118 configured to detect the received signal 108 and generate a corresponding detection signal 106. The detector 118 may be coupled to the processing circuit 102 and configured to provide the detection signal 106 to the processing circuit 102. In general, the detector 118 may be configured to be sensitive to a type of energy of interest, e.g., a type of radiation of interest such as light, sound, radio, etc. The configuration of the detector 110 may be adapted depending on the desired application. In the context of the present disclosure, the term "detector" may be used in the same manner as the term "sensor."

[0030] For example, in the context of ToF measurements and LIDAR, the detector 118 may be a light detector configured to detect light (e.g., the detector 118 may include one or more photodiodes, a transimpedance amplifier, and the like), and the signal 108 may be a light signal. As another example, the detector 118 may be a radio receiver configured to detect radio waves (e.g., the detector 118 may include one or more antennas, frequency converters, and the like), and the signal 108 may be a radio signal. As another example, the detector 118 may be an ultrasonic detector configured to detect sound waves (e.g., the detector 118 may include a membrane, a transducer element, and the like), and the signal 108 may be a sound wave.

[0031] The detection signal 106 may therefore contain the radiation detected by the detector 118, e.g., during a predefined detection period. For light detection, the detection signal 106 may, for example, contain the number of photons over an integration time of the detector 118. The received signal 108 may therefore contain a noise component and a signal component. The noise component may include noise from external sources, such as ambient light associated with the light detection.

[0032] In various aspects, processing circuitry 102 may be configured to filter detection signal 106 prior to further processing (e.g., prior to generating a differentiation signal 110) to reduce a noise level in detection signal 106 provided by detector 118. By way of example, processing circuitry 102 may include a filter circuit configured to receive an input signal (detection signal 106) and output a filtered signal corresponding to a noise-filtered version of the input signal.In one example configuration, processing circuitry 102 may include a low-pass filter configured to filter out components of detection signal 106 having a frequency greater than a predefined threshold frequency, or a high-pass filter configured to filter out components of detection signal 106 having a frequency less than a predefined threshold frequency. As another example configuration, processing circuitry 102 may include a band-pass filter configured to filter out components of the detection signal having a frequency outside a predefined frequency range. The threshold frequency and / or the frequency range may be adjusted according to an expected frequency of the noise component and / or the signal component of received signal 108 to pass the signal component and filter out the noise component.In a preferred configuration, the filter circuit may be an analog circuit.

[0033] The processing circuit 102 may be configured to generate a differentiation signal 110 s'(t) representative of a rate of change of a signal level of the detection signal 106 over time. The processing circuit 102 may be configured to perform differentiation of the detection signal 106 (in some aspects, differentiation of a filtered version of the detection signal 106) to obtain the differentiation signal 110 as a result of the processing. The signal level of the differentiation signal 110 may therefore vary over time according to the rate of change of the signal level of the detection signal 106. By way of example, a signal level of the differentiation signal 110 at a particular time may correspond to a value of the rate of change of the signal level of the detection signal 106 at that time. In the case of an analog implementation, the differentiation signal 110 may be an analog signal.

[0034] The term "signal level" may be used herein to describe a parameter associated with a signal (e.g., a detection signal, a differentiation signal, etc.) or with a portion of a signal (e.g., a peak or a valley). A "signal level," as used herein, may include at least a power level, a current level, a voltage level, or an amplitude level (also referred to herein as amplitude). In a preferred configuration for an analog implementation of the operation of the processing circuit, a signal level of a signal during processing may be expressed as a voltage level. In general, a "signal level" may represent a magnitude of the corresponding signal, e.g., over time or at a specific instant in time. A "signal level," in some aspects, may have a magnitude and a sign (positive or negative), depending on the type of signal, the representation of the signal, etc.

[0035] The processing circuit 102 may further be configured to determine (e.g., identify) times 112 that correspond to a change in the sign of the differentiation signal 110, e.g., from positive to negative or from negative to positive. The processing circuit 102 may therefore be configured to determine whether and where the differentiation signal 110 changes its sign. For example, the processing circuit 102 may be configured to determine times 112 at which the signal level of the differentiation signal 110 becomes zero, e.g., from positive to zero before becoming negative, or from negative to zero before becoming positive. A sign change in the differentiation signal 110 may correspond to a change in the behavior of the detection signal 106, e.g., from a signal level that increases over time to a signal level that decreases over time, or vice versa.

[0036] The times 112 corresponding to a change in the sign of the differentiation signal 110 may correspond to the respective times of one or more characteristic portions 114 of the detection signal 106. The characteristic portions 114 of the detection signal 106 may, for example, include one or more peaks and / or one or more valleys. By way of example, a time 112 corresponding to a change in the sign of the differentiation signal 110 may coincide with a time at which the detection signal 106 (and accordingly, the received signal 108) has a peak or a valley. The processing circuit 102 may therefore be configured to determine (e.g., identify) a respective temporal location of the characteristic portions of the detection signal 106 based on the determined times 112.The characteristic portions of the detection signal 106 may correspond to the respective characteristic portions of the received signal 108.

[0037] The present disclosure may be based on the recognition that the information provided by identifying the sign changes of the differentiation signal 110 sufficiently characterizes the detected signal 108 to enable more advanced and refined processing and that it can be obtained with a simple and readily available circuit configuration (see, e.g., Fig. 2A). The determination of the “zero crossing” times 112 in the differentiation signal 110 allows a simple but sufficiently accurate approximation of the temporal evolution of the detection signal 106 (and accordingly of the reception signal 108) for carrying out further processing and refinements of other measurements (e.g., a time-of-flight measurement, as with respect to Fig. 1B and Fig. 1C).

[0038] In various aspects, processing circuitry 102 may be configured to generate an output signal 116 representative of the determined times 112. Processing circuitry 102 may be configured to encode the determined times 112 to generate output signal 116 representative of one or more characteristic properties of received signal 108.

[0039] The processing circuit 102 may use the output signal 116 for further processing and / or be configured to provide the output signal to other processing circuits outside the detection device 100. The output signal 116 may thus encode information representative of the times at which a sign change of the differentiation signal 110 occurs, and may accordingly encode information representative of the times at which the detection signal 106 has a characteristic component (illustratively, a characteristic element or feature). The processing circuit 102 may be configured to provide the output signal 116 in various forms, as described with respect to the Fig. 2A to Fig. 2F. The output signal 116 can also be referred to as a coded differentiation signal.

[0040] According to various aspects, processing circuitry 102 may be configured to store output signal 116, e.g., in a memory of processing circuitry 102 (e.g., in a buffer), and retrieve the stored output signal 116 during subsequent processing. In this scenario, processing circuitry 102 may be configured to convert output signal 116 into any suitable format for storage and subsequent retrieval, e.g., via a digital-to-analog converter.

[0041] In general, the Fig. 1A may be performed for each signal that can be detected by the detection device 100. However, in various aspects, the received signal 108 may be associated with a corresponding transmitted signal 122, the characteristics of which may be known to the processing circuitry 102. As an additional or alternative example, the received signal 108 may be provided with or associated with one or more expected signal features. For example, the processing circuitry 102 may have a priori knowledge of features and / or properties of the received signal 108, such as an expected waveform, an expected number of peaks, and the like.

[0042] In an example configuration, as in Fig. 1B and Fig. 1C, the received signal 108 may be or include a reflection of the transmitted signal 122 toward the sensing device 100. The transmitted signal 122 may be incident upon an object 124 (or a plurality of objects) within a field of view of the sensing device 100, and the received signal 108 may be or include a reflection (e.g., a specular reflection, also referred to as a direct reflection) from the object 124 toward the sensing device 100. However, it should be understood that the received signal 108 may be generally understood as the transmitted signal 122 as received at the sensing device after propagation in a medium (e.g., in air, in a liquid, etc.), so the original properties of the transmitted signal 122 may vary due to propagation conditions (e.g., obstacles, viscosity of the medium, reflectivity of the encountered objects, etc.).The received signal 108 may therefore correspond to the associated transmitted signal 122 after propagation and, in a relevant application, after reflection.

[0043] According to various aspects, the processing circuit 102 can be configured to reconstruct the signal 108 detected by the detection device 100 based on the determined times 112, for example based on the determined time locations of the characteristic sections 114. The processing circuit 102 can be configured to further reconstruct the received signal 108 based on one or more predefined properties of the corresponding transmitted signal 122. Illustratively, the processing circuit 102 can be configured to determine one or more properties of the received signal 108 based on the times 112 and one or more expected properties for the received signal 108 according to the (original) properties of the corresponding transmitted signal 122 (and / or according to the expected signal characteristics).Further signals and / or properties that the processing circuit 102 can use for reconstruction are described in connection with . Fig. 2A to Fig. 5G. In other words, the processing circuit 102 may be configured to generate a reconstructed signal representative of the received signal 108 by using the determined time positions and one or more predefined (illustratively predetermined) characteristics of the corresponding transmitted signal 122.

[0044] As an example, the one or more predefined (illustratively, known to processing circuitry 102) characteristics of the transmit signal 122 may include a number of peaks in the transmit signal 122, a signal level of the transmit signal 122, a signal level at the peaks of the transmit signal, a time interval between consecutive peaks in the transmit signal 122, a duration of a peak (e.g., FWHM of the peak), and / or a total duration of the transmit signal 122. In the context of time-of-flight detection using light, the peaks in the transmit signal 122 may correspond to light pulses in the transmit signal 122.

[0045] As another example, the one or more characteristics of the received signal 108 that the processing circuit 102 may determine based on the times 112 may include: a number of peaks in the received signal 108, a number of valleys in the received signal 108, a time interval between consecutive peaks in the received signal 108, a slope of the received signal 108, a time interval between a reference time (e.g., an initial time of emission of the transmitted signal 122) and one or more peaks and / or valleys in the received signal 108.

[0046] In general, the transmit signal 122 may contain one or more peaks, e.g., a single peak in a simple configuration or multiple peaks in a more advanced coding scheme. In this configuration, the first time point 112 (e.g., the earliest time point 112 within the differentiating signal 110) may be assumed to correspond to a first peak in the sense signal 106, i.e., the first detectable change in the rate of change over time may be assumed to occur at the first peak. In this scenario, the subsequent time point 112 (if any) may correspond to a valley, the further subsequent time point 112 (if any) may correspond to a second peak, and so on.In various aspects, processing circuitry 102 may be configured to connect time points 112 at an odd position in the sequence of time points 112 to a peak of the detection signal 106 and time points at an even position to a valley of the detection signal 106. Therefore, the number of "odd" time points 112 may indicate a number of peaks in the detection signal, and a number of "even" time points 112 may indicate a number of valleys. Accordingly, a time difference between odd time points 112 may represent a time difference between peak values ​​of the detection signal 106.

[0047] According to various aspects, the processing circuit 102 may be configured to reconstruct the received signal 108 based on one or more predefined points in time of one or more predefined received signals, e.g., based on one or more predefined characteristic portions of one or more predefined received signals. For example, the processing circuit 102 may be configured to reconstruct the signal 108 using one or more predefined (e.g., known) patterns for the temporal location of the characteristic portions. For example, the processing circuit 102 may estimate a modification of the transmitted signal 122 during propagation based on a current environmental scenario (e.g., weather conditions, number of obstacles in the field of view, lighting conditions, etc.), and thus predict expected properties or features (e.g., shape, signal level, etc.).) of the received signal 108 for use in reconstruction. For example, in the context of light detection in a densely populated field of view, the received signal 108 is likely to contain numerous peaks corresponding to reflections from multiple objects.

[0048] In an exemplary configuration, the processing circuit 102 may be configured to reconstruct the received signal 108 by comparing the determined times 112 with the predefined times of the predefined received signals. The processing circuit 102 may be configured to compare the pattern defined by the determined times 112 (e.g., a number of times 112, a time interval between consecutive times 112, and the like) with one or more predefined (e.g., expected) patterns and may be configured to reconstruct the received signal 108 according to the result of the comparison. For example, the received signal 108 may approximately correspond to the predefined received signal with the most similar pattern.

[0049] In an exemplary configuration, the reconstruction of the received signal 108 may be performed in the digital domain. For example, the processing circuit 102 may include an analog portion configured to perform the initial reception of the detection signal 106, the generation of the differentiation signal 110, and the identification of the time points 112. The processing circuit 102 may further include a digital portion (e.g., a digital signal processing circuit) configured to receive the information extracted by the analog circuit (encoded in the output signal 116) and configured to perform the reconstruction of the received signal 108 based on this additional information.

[0050] As mentioned above, a relevant application of the approach described here can be for time-of-flight measurements. As in Fig. 1B, the processing circuit 102 may be further configured to perform a direct time-of-flight measurement, and may be configured to modify a result of the time-of-flight measurement based on the determined times 112 (e.g., using the information encoded in the output signal 116). In this configuration, the processing circuit may be configured to receive a start signal 120 representative of an emission of the transmit signal 122. The start signal 120 may, for example, represent or indicate a start time for the emission of the transmit signal 122. The start signal 120 may thus represent a starting time for the measurement of the time-of-flight of the transmit signal 122. Time-of-flight measurements may typically be based on light emission and detection, so that the transmit signal 122 may be a light signal in a relevant application. However, time-of-flight measurements may also be based on other signal types, such as light waves.B. sound waves, so that the transmission signal 122 can alternatively also be a sound wave or another signal type.

[0051] For a direct time-of-flight measurement, the processing circuit 102 may be configured to generate a stop signal 126 representing an arrival (e.g., reception) of the received signal 108 at the detection device 100, and may be configured to determine (e.g., calculate) the time of flight as the time difference between the start signal 120 and the stop signal 126 (e.g., a time difference between the times represented by the start signal and the stop signal). The stop signal 126 may represent or indicate a time at which the reflection of the transmitted signal 122 is detected at the detection device 100. The stop signal 126 may, for example, represent the time of arrival of the signal component of the received signal 108 at the detection device 100 (e.g., at the detector 118).

[0052] There may be various strategies for generating the stop signal 126 based on the detection signal 106 provided by the detector 118. For example, the processing circuit 102 may implement various methods for generating a stop signal 128. In a simple implementation, the processing circuit 102 may be configured to compare a signal level of the detection signal 106 with a predefined threshold (e.g., an average noise level) and may be configured to generate the stop signal 126 if the signal level of the detection signal 106 is greater than the predefined threshold.More generally, the processing circuit 102 may be configured to generate the stop signal 126 when the signal level of the detection signal 106 is within a predefined signal range (illustratively, a range for which the detection signal 106 can be assumed to correspond to a reflection of the transmission signal 122 and not to noise from the environment). In an analog implementation, the processing circuit 102 may include a comparator configured to compare the detection signal 106 to a reference signal (e.g., a reference voltage) representative of the predefined threshold, and the stop signal 126 may be the output signal of the comparator (which goes high when the signal level of the detection signal 106 is greater than the threshold). Other possible configurations are described in connection with the . Fig. 5A to Fig. 5G is described in more detail.

[0053] The processing circuit 102 may be configured to determine the flight time associated with the transmit signal 122 based on the start signal 120 and the stop signal 126. In a preferred configuration, the processing circuit 102 may be configured to perform a time-to-digital conversion 130 using the start signal 120 and the stop signal 126 to calculate the flight time, e.g., to generate a digital signal 132 representing the flight time. The time-to-digital conversion 130 may digitally express the time difference between the reception of the start signal 120 and the generation of the stop signal 126. In an exemplary configuration, the processing circuit 102 may be configured to determine the flight time associated with the transmit signal 122 as a number of clock cycles from the reception of the start signal 120 to the generation of the stop signal 126, e.g.,a number of clock cycles from a rising edge of the start signal 120 to a rising edge of the stop signal 126. In some aspects, the processing circuit 102 may include a time-to-digital converter circuit configured to receive the start signal 120 and the stop signal 126 and generate a corresponding digital output signal 132. A more detailed description of one possible configuration of the time-to-digital converter circuit is provided with reference to FIG. Fig. 6 given.

[0054] The processing circuit 102 may be configured to use the analysis of the rate of change of the signal level of the detection signal 106 to refine the time-of-flight measurement. The processing circuit 102 may be configured to generate one or more adjustment values ​​for the time-of-flight measurement based on the output signal 116. The adjustment may be based on the characteristic properties of the received signal 108 (e.g., shape information) encoded by the output signal 116, e.g., on the temporal position of the characteristic portions 114 of the detection signal 106 (and, accordingly, the received signal 108). The processing circuit 102 may therefore be configured to modify the time-of-flight value based on the determined times 112, e.g., in accordance with the determined time positions of the one or more characteristic portions 114.

[0055] For example, the processing circuit 102 may be configured to determine the value of the determined time of flight based on the timing of a first peak of the detection signal 106 (and this information may be encoded in the output signal 116, as described with respect to Fig. 2A to Fig. 2F further explained), corresponding to a first peak of the received signal 108. In general, the shape information encoded in the output signal 116 can enable a correction of the timing of the generation of the stop signal 126. For example, it can be the case that the signal level of the detection signal 106 is reduced by environmental conditions, e.g., by reflection from a particularly absorbent surface, by particular noise conditions, and the like. In this case, the stop signal 126 can be generated with a delay compared to the actual arrival of the reflection of the transmitted signal 122 at the detection device 100, since the signal level of the detection signal 106 remains below the noise threshold longer than usual. The shape information encoded in the output signal 116 can correct such a delay, e.g.,by estimating the time at which the stop signal 126 should have been generated, thereby adjusting the determined flight time. The processing circuit 102 may therefore be configured to correct a delay in generating the stop signal 126 based on the determined times 112.

[0056] It should be understood that using the temporal position of the first peak in the detection signal 106 to adjust the time-of-flight measurement is only one example, and that other adjustments may be made based on the reconstructed characteristics of the received signal 108. As another example, the processing circuit 102 may be configured to modify the determined time-of-flight value based on a number of peaks in the detection signal 106. In a direct light time-of-flight measurement, the transmitted signal 122 may contain a single light pulse, so the presence of more than one peak in the received signal 108 may indicate reflections from multiple objects in the field of view. The number of peaks may represent the number of objects from which the transmitted signal 122 reflected.Accordingly, the processing circuit 102 may be configured to use a temporal separation between two peaks in the detection signal 106 to determine (e.g., estimate or calculate) a relative distance between two objects in the field of view, and optionally adjust a particular time-of-flight value based on this relative separation.

[0057] To illustrate, the processing circuit may include a stop signal generation circuit 140, a signal differentiation circuit 142, and a time-of-flight determination circuit 144 configured to perform the respective operations mentioned above. In an exemplary configuration, the stop signal generation circuit 140 and the signal differentiation circuit 142 may be part of an analog section 150a of the processing circuit 102, i.e., they may include analog components to perform the respective operation in an analog manner. The time-of-flight determination circuit 144 may be part of a digital section 150b of the processing circuit 102 and may be configured to perform the respective operation in a digital manner. The analog section of the processing circuit 102 may be an analog signal processing stage, and the digital section may be a digital signal processing stage.

[0058] Fig. 1C shows the sensing device 100, which further includes a signal emission circuit 100a configured to emit the transmission signal 122. In this configuration, the processing circuit 102 may be part of a signal detection circuit 100b of the sensing device 100. The transmission signal 122 may also be referred to herein as a transmission signal. However, it should be understood that the transmission signal 122 may generally be emitted by an entity other than the sensing device 100, e.g., by a light emission system external to the sensing device 100.

[0059] The signal emission circuit 100a may include a signal source 134 configured to emit (in some aspects also radiate) the transmission signal 122, and a control unit 136 configured to control the signal source 134 to control (e.g., cause) the emission of the transmission signal 122. In the following, particular reference is made to the emission of a light signal 122, so that the signal source 134 may be a light source. However, it is understood that the aspects described with respect to a light source may also apply correspondingly to sources of other signal types, e.g., a radio transmitter for emitting radio waves, a membrane for radiating sound waves, etc.

[0060] In various aspects, the signal source 134 may be or include a light source configured to emit light. The light source 134 may be configured to emit light at a predefined wavelength, e.g., in the visible range (e.g., from about 380 nm to about 700 nm), in the infrared and / or near-infrared range (e.g., in the range from about 700 nm to about 5000 nm, e.g., in the range from about 860 nm to about 1600 nm, or e.g., at 905 nm or 1550 nm), or in the ultraviolet range (e.g., from about 100 nm to about 400 nm). In some aspects, the light source 134 may be or include an optoelectronic light source (e.g., a laser source). For example, the light source 134 may include one or more light-emitting diodes. As another example, the light source may include one or more laser diodes, e.g., B.one or more edge-emitting laser diodes or one or more vertical-cavity surface-emitting laser diodes. In various aspects, the light source 134 may include a plurality of emitter pixels. For example, the light source 134 may include an emitter array having a plurality of emitter pixels. For example, the plurality of emitter pixels may be or include a plurality of laser diodes.

[0061] The controller 136 may be configured to provide a control signal 138 to the light source 134 to cause the emission of light, e.g., the emission of the transmit signal 122. In various aspects, the controller 136 may be configured to encode the control signal 138 to cause the emission of a modulated transmit signal. In a simple configuration, e.g., for a time-of-flight measurement, the transmit signal 122 may include a light pulse, the echo of which is received as the receive signal 108. In a more advanced configuration, the transmit signal 122 may include a plurality of light pulses, and the properties of the light pulses (e.g., a number, a spacing between the pulses, etc.) may be selected according to a predefined modulation scheme (e.g., to encode data into the transmitted light signal 122, to uniquely characterize the light signal, and the like).In some aspects, the transmitted signal 122 may be a light signal modulated to include one or more characteristic components according to a predefined modulation scheme. In an example configuration, the light source 134 may include a driver circuit configured to drive the light emission, and the controller 136 may be configured to provide the control signal 138 to the driver circuit.

[0062] The control signal 138 may include the start signal 120 provided to the processing circuit 102. For example, the controller 134 may be configured to send the control signal 138 to the light source 132 and indicate the start of light emission to the processing circuit 102 via the start signal 120.

[0063] In an example configuration, the controller 136 may be located external to the signal output circuit 100a and / or external to the sensing device 100. In this scenario, the sensing device 100 may be communicatively connected to the external controller 136. The controller 136 may, for example, be a measurement control circuit of a LIDAR system. Another example is a central processing circuit of a vehicle.

[0064] In the context of light detection, detector 118 may include one or more photodiodes, such as a one-dimensional array of photodiodes or a two-dimensional array of photodiodes. Detector 118 may, for example, include at least one PIN photodiode, an avalanche photodiode (APD), a single-photon avalanche photodiode (SPAD), or a silicon photomultiplier (SiPM). A photodiode may generate a corresponding current when light strikes the photodiode, and the current(s) generated by one or more photodiodes may be provided to processing circuitry 102 as a detection signal 106 (or as a voltage after conversion via a transimpedance amplifier).

[0065] In an exemplary configuration that can provide targeted illumination of the field of view and, accordingly, an increased signal-to-noise ratio for regions of interest, the detector 118 can include a two-dimensional array of (detector) pixels, and light detection can occur by activating only some of the pixels during a detection interval. In this scenario, the detector 118 can include a processor configured to control the detector 118 to sequentially activate pixels of the pixel array such that, during a detection interval, one or more pixels are active (illustratively: sensitive to the incident light) and one or more other pixels are inactive (insensitive to the incident light). Activating a pixel can, for example, involve applying a bias voltage to the pixel.The processor may be configured to activate the pixels of the pixel array pixel by pixel, row by row, or column by column, for example, to sequentially detect light from different areas of the field of view of the detection device 100. In this configuration, the detection signal 106 may include a plurality of sub-detection signals, each corresponding, for example, to the active pixels during a respective detection interval.

[0066] The sequential pixel activation can be coordinated with sequential illumination of the field of view. In this configuration, the light source 134 can comprise an array of emitter pixels, e.g., an array of light-emitting diodes or laser diodes. The arrangement of the emitter pixels can be one-dimensional or two-dimensional. For example, a two-dimensional emitter array can enable 2D flood, 1D row, 1D column, or pixel-by-pixel illumination. The controller 136 can be configured to control the emitter pixels such that during an emission interval (e.g., corresponding in duration to an acquisition interval), one or more emitter pixels are active and emitting light, while one or more other emitter pixels are inactive and not emitting light.In an example configuration, the controller 136 may be configured to send a synchronization signal to the light source 134, and the synchronization signal may be representative of the emitter pixels to be activated during a respective emission interval. The synchronization signal may, for example, indicate the temporal sequence for activating the emitter pixels, e.g., pixel by pixel, row by row, or column by column. The controller 136 may also be configured to send the synchronization signal to the detector 118 to synchronize the activation of the detector pixels with the activation of the emitter pixels (and thus reduce the overall measurement noise). The synchronization signal may thus also be representative of the detector pixels to be activated during a corresponding acquisition interval, e.g., pixel by pixel, row by row, or column by column.

[0067] In this scenario, processing circuitry 102 may be configured to generate multiple partial differentiation signals (and corresponding output signals) and, in some aspects, multiple partial stop signals, e.g., a partial detection / stop signal for each partial detection signal.

[0068] In general, the reconstruction of the received signal 108 can also be used for other purposes besides time-of-flight measurement, which represents a relevant application. For example, the reconstruction of the received signal 108 can enable the estimation of properties of the environment in which the transmitted signal 122 propagates, or the decoding of information encoded in the transmitted signal.

[0069] Various aspects of the operation of the processing circuit 102 are described with respect to the Fig. 2A to Fig. 2F. In general, the parameters related to Fig. 2A to Fig. 2F may be part of the signal differentiation circuit 142 of the processing circuit 102.

[0070] As in Fig. 2A, the processing circuit 102 may include a differentiation circuit 202 configured to receive as input the detection signal 106 (or its filtered version if the processing circuit 102 optionally includes a filter circuit 204 configured as described with respect to Fig. 1) and generates the differentiation signal 110 as output. The differentiation circuit 202 may generally be part of a differentiation stage, optionally including filtering to perform signal conditioning before and / or during the differentiation process. In an exemplary configuration, the filter circuit 204 may include aggressive low-pass filters to reduce noise power and provide a "clean" signal as input to the differentiation stage 202. Additionally or alternatively, the differentiation circuit 202 itself may be designed to perform filtering as part of the differentiation process. For example, in operational amplifier-based implementations, the role of the components may be chosen to avoid some instabilities, which also affects the bandwidth of the differentiation stage 202.

[0071] As with regard to Fig. 1A, the various operations of processing circuitry 102 may generally be performed in the digital domain or in the analog domain. In a digital implementation, processing circuitry 102 may, for example, include an analog-to-digital converter (ADC) to convert the analog detection signal 106 from detector 118 into a digital signal before further processing. However, for ToF measurements, an ADC capable of sampling the detected signal may require high speed and thus represent a complex and expensive component. Therefore, in a preferred configuration, differentiation circuitry 202 may be or include an analog differentiation circuit (e.g., an analog differentiator). As shown in inset 210 in Fig. 2A, which shows an exemplary implementation, the analog differentiation circuit may include an operational amplifier 212 configured to receive the detection signal 106 at an input, perform analog differentiation of the detection signal, and provide the differentiation signal 110 at the output.

[0072] In a preferred configuration, the processing circuit 102 may be configured to generate the differentiation signal 110 by determining (e.g., calculating or generating) a first-order derivative of the acquisition signal 106. In the analog configuration, this function may be implemented by the analog differentiator, which is configured to perform analog differentiation of the acquisition signal 106 and provide as an output the differentiation signal 110 representing the first-order derivative. However, it should be understood that, in general, other (e.g., more complex) approaches may also exist to evaluate the rate of change of the acquisition signal 106 over time, e.g., in the digital domain based on image analysis of a graphical representation of the acquisition signal 106.

[0073] The times 112 corresponding to the change in sign of the differentiation signal 106 can be representative of local minima and / or local maxima in the detection signal 106. The change in sign in the temporal rate of change of the detection signal 106 can indicate, for example, that the signal level of the detection signal 106 has stopped increasing and is beginning to decrease (local maximum) or vice versa (local minimum). The times 112 at which the rate of change is zero (for illustration: the times 112 at which the signal level of the differentiation signal 110 is zero) can correspond to the times at which a local maximum or a local minimum is present in the detection signal 106.

[0074] According to various aspects, the processing circuit 102 may be configured to determine the times 112 by determining one or more zero crossings of the differentiation signal 110. Illustratively, the portions of the detection signal 110 where the signal level is zero and then becomes positive may correspond to a local minimum (e.g., a valley in the detection signal 106), while the portions of the detection signal 110 where the signal level is zero and then becomes negative may correspond to a local maximum (e.g., a peak in the detection signal 106). A zero crossing may correspond to an intersection of the time axis in a graph representing the differentiation signal 110.

[0075] To implement the zero-crossing detection, the processing circuit 102 may include a zero-crossing detector 206 configured to receive as input the differentiation signal 110 and to provide (e.g., generate or deliver) as output a zero-crossing signal 208 ZC_s'(t) representative of the zero crossings of the differentiation signal 110 (and, accordingly, of the times 112). The zero-crossing detector 206 may be configured to compare the signal level of the detection signal 110 with a predefined threshold value (e.g., zero, e.g., expressed in volts, considering an analog implementation), and may be configured to output the zero-crossing signal 208 with a first signal level (e.g.,, a high level) when the signal level of the differentiation signal 110 is equal to or above the predefined threshold, and may be configured to output the zero-crossing signal 208 with a second signal level (e.g., a low level lower than the first level, e.g., zero) when the signal level of the differentiation signal 110 is lower than the predefined threshold. As shown in . Fig. As shown in Figure 2A, the zero-crossing signal 208 may have a rectangular waveform that transitions from high to low or vice versa according to times 112. This type of representation of the zero-crossing represents one approach that can be conveniently implemented, but it should be understood that other types of representation (e.g., other types of encoding) may also be provided. The zero-crossing signal 208 may also be referred to herein as the zero-crossing output signal 208.

[0076] In an analog implementation, the zero crossing detector 206 may be or include an analog comparator, as shown in the Fig. illustrated, e.g., with a differential amplifier 222 configured to compare the differentiation signal 110 with a reference signal 224 and generate a corresponding output zero-crossing signal 208. For example, the differential amplifier 222 may be configured to compare a voltage corresponding to the differentiation signal 110 with a reference voltage (e.g., 0 volts).

[0077] The zero-crossing signal 208 can encode the information representing the times 112 and can thus encode the temporal positions of the characteristic portions 114 of the detection signal 106 in a direct and easily obtainable manner. The processing circuit 102 can be configured to determine the times 112 corresponding to a change in the sign of the differentiation signal 110 based on the times corresponding to the output of the zero-crossing detector 206 switching from the first signal level to the second signal level, or vice versa. Considering the exemplary scenario in Fig. 2A, a falling edge of the zero-crossing signal 208 may correspond to a peak in the detection signal 106, and a rising edge of the zero-crossing signal 208 may correspond to a valley in the detection signal 106. The zero-crossing signal 208 thus generated may thus provide a compact and convenient representation of relevant shape characteristics of the detection signal 106 (and, accordingly, the received signal 108) to enable further, more advanced processing (e.g., in the digital signal processing stage).

[0078] In other words, the zero crossing of the first derivative s'(t) can make it possible to find a peak or a valley (a local maximum or minimum). The output of the zero crossing detector 206 ZC_s'(t) can alternate between a "high" and a "low" state when the input signal s'(t) changes from positive to negative. This behavior can be realized, for example, with a comparator that has a reference level of zero (or close to zero). The change from "high" to "low" or from "low" to "high" provides information about whether the derived signal s'(t) had a negative or positive slope at the zero crossing. In the case of s'(t), for example, it provides information about whether there was a local minimum or maximum.

[0079] In a simple configuration, the zero-crossing signal 208 may therefore be provided as output signal 116 for further processing. However, in other aspects, the processing circuit 102 may be configured to further process the information (e.g., to further process the zero-crossing signal 208) to facilitate subsequent decoding by a digital circuit. In some cases, the processing circuit 102 may include encoding circuitry configured to encode the information representing the time points 112 in a format that is more easily decoded in the digital domain. This optional signal encoding stage allows the first-derivative zero-crossing signals to be represented in a manner that simplifies subsequent signal processing steps (e.g., to produce a sparser signal that can be more easily compressed).

[0080] As in Fig. 2B and Fig. 2C, the processing circuit 102 may be further configured to generate an encoded sparse signal 216 representing the times 112 corresponding to the change in sign of the differentiation signal 110. The signal 216 may be a sparse signal that only includes signal components corresponding to the times 112 (and may otherwise be zero). By way of example, the encoded sparse signal 216 may have a first signal level (e.g., a signal level different from zero, e.g., a signal level greater than zero) corresponding to the times 112 and may have a second signal level (e.g., a signal level of substantially zero) in the remaining portions of the encoded sparse signal 216 (e.g., corresponding to other portions of the detection signal 106).For example, the encoded sparse signal 216 may contain one or more peaks or pulses corresponding to the times 112. The encoded sparse signal 216 may thus be provided as the output signal 116 for further processing (alternatively or in addition to the zero-crossing signal 208), providing a more compact representation of the relevant information of the detection signal 106. For example, the processing circuit 102 may be configured to generate the output signal 116 by encoding the determined times 112 via the encoded sparse signal 216.

[0081] In some aspects, processing circuitry 102 may be configured to perform reconstruction of received signal 108 (and / or time-of-flight refinement, as described below) using encoded sparse signal 216. In general, processing circuitry 102 may include encoding circuitry 214 configured to generate encoded sparse signal 216.

[0082] There are various ways to generate a sparse signal 216. Two exemplary configurations, each providing coded sparse signals 216a, 216b, are shown in Fig. 2B and Fig. 2C. Such exemplary configurations provide a simple integration of this functionality into the processing circuit 102, but it should be understood that other solutions are also possible.

[0083] In an example configuration, as in Fig. 2B, the encoding circuit 214 may be configured to detect the edges of the zero-crossing signal 208 to generate the encoded sparse signal 216a u'(t) (an example of an encoded sparse signal 216). The encoding circuit 214 may thus be configured as an edge detection circuit that receives the output 208 of the zero-crossing detector 206 and generates an encoded zero-crossing signal 216a. The encoded sparse signal 216a may, for example, include signal pulses corresponding to the rising / falling edges of the zero-crossing signal 208. As shown in Fig. 2B, the coding circuit 214 may be configured to generate the encoded sparse signal 216a as a unipolar signal u'(t) or as a signal pair comprising a first encoded signal p_s'(t) representing the rising edges of the zero-crossing signal 208 and a second encoded signal n_s'(t) representing the falling edges of the zero-crossing signal 208.

[0084] In an analog implementation, as in the Fig. As shown, the encoding circuit 214 may include an analog edge detector, e.g., a flip-flop 242 configured to receive the zero-crossing signal 208 at a first input (d) and a clock signal 244 at a second input (clk), and an XOR logic gate 246 configured to receive as inputs the zero-crossing signal 208 and the output (q) of the flip-flop 242. The encoded signal 216a may correspond to the output of the XOR logic gate 246. The configuration in the Fig. may provide for the detection of both rising and falling edges of the zero-crossing signal 208. The configuration may be adapted accordingly to detect only the rising edges (e.g., to provide the first coded signal p_s'(t)) and / or only the falling edges (e.g., to provide the second coded signal n_s'(t)).

[0085] As another example configuration, as in Fig. 2C, the coding circuit 214 may be configured to differentiate the zero-crossing signal 208 to generate the encoded sparse signal 216b diff_s'(t) (an example of an encoded sparse signal 216). The coding circuit 214 may therefore be configured as a differentiator circuit (e.g., including an analog differentiator, which may be used, for example, as the differentiator in the Fig. configured) that is configured to receive the output 208 of the zero-crossing detector 206 and generate a differentiated zero-crossing signal 216b. Given the square waveform of the zero-crossing signal 208, its derivative may be (essentially) zero except in accordance with the rising or falling edges, thereby providing sparse encoding of the relevant portions of the zero-crossing signal 208. As shown in Fig. 2C, the encoding circuit 214 may be configured to generate the encoded sparse signal 216b as a single signal diff_s'(t) or as a pair of signals including a first encoded signal p_s'(t) representing the rising edges of the zero-crossing signal 208 and a second encoded signal n_s'(t) representing the falling edges of the zero-crossing signal 208. For example, the encoding circuit 214 may include a rectifier configured to rectify the output of the differentiator to provide the first and second encoded

[0086] Depending on the architecture of the detection device 100 (e.g., the time-to-digital converter), the pulse-like (or "event-like") representation of the zero-crossing information provided by the encoded sparse signal 216a, 216 may be more suitable for processing. Also in this example, it is possible to encode the direction of the zero crossing (from positive to negative or vice versa) in the polarity of the encoded pulse-like signal.

[0087] According to various aspects, as in Fig. 2D to Fig. 2F, the processing circuit 102 may be further configured to determine a rate of change of the differentiation signal 110 to obtain additional information for signal reconstruction (and / or time-of-flight refinement).

[0088] The processing circuit 102 may be configured to generate a further (e.g., second) differentiation signal 252 s''(t) representative of a rate of change of a signal level of the differentiation signal 110 over time. The second differentiation signal may thus change over time in accordance with the change in the signal level of the differentiation signal 110. In a preferred configuration, the processing circuit 102 may be configured to generate the second differentiation signal 252 by determining (e.g., calculating or generating) a second-order derivative of the detection signal 106 (or a first-order derivative of the differentiation signal 110).

[0089] The processing circuit 102 may be further configured to determine (e.g., identify) further (e.g., second) times 254 corresponding to a change in the sign of the second differentiation signal 252, e.g., from positive to negative or from negative to positive. The processing circuit 102 may be configured to encode the determined second times 254 to generate a second output signal representative of one or more second characteristic properties of the received signal detected by the detection device. The second output signal may be a separate signal or a part of the (first) output signal 116. According to various aspects, the processing circuit 102 may be configured to store the second output signal, e.g., in a memory of the processing circuit 102 (e.g., in a buffer), and to retrieve the stored second output signal during subsequent processing.

[0090] The second time points 254 may correspond to local minima or local maxima in the (first) differentiation signal 110 and may represent inflection points in the acquisition signal 106. The second time points 254 may, for example, correspond to portions of the acquisition signal 106 in which the concavity of the acquisition signal 106 (e.g., its representation in a graph) changes.

[0091] The characterization of the second differentiation signal 252 may thus provide additional information about the waveform of the detection signal 106 (and correspondingly, the received signal 108). The processing circuit 102 may further be configured to perform the reconstruction of the received signal 108 (additionally or alternatively) based on the determined second times 254. In some aspects, the reconstruction may further be based on predefined second times of the predefined received signals (e.g., on knowledge of the expected time positions of inflection points within predefined received signals). In some aspects, the processing circuit 102 may further be configured to use the determined second times 254 to modify the value of the determined time of flight associated with the transmitted signal 122, as described with respect to Fig. 1B and Fig. 1C discussed.

[0092] As in Fig. 2D, the processing circuit 102 may include a further (second) differentiation circuit 202b configured to receive as input the differentiation signal 110 and to generate as output the second differentiation signal 252. In some aspects, the differentiation circuit 202 and the second differentiation circuit 202b may together be understood as a differentiation stage. As described for the differentiation circuit 202, the second differentiation circuit 202b may generally operate in the digital domain or in the analog domain. In a preferred configuration, the second differentiation circuit 202b may be an analog circuit, e.g., an analog differentiation (e.g., configured as shown in inset 210 in Fig. 2A for the first differentiation circuit 202). The second analog differentiation circuit 202b may be configured, by way of example, to perform an analog differentiation of the differentiation signal 110 to determine the second-order derivative of the detection signal 106 and to provide as an output the second differentiation signal 252 representing the second-order derivative.

[0093] As described with respect to the (first) differentiation signal 110, the processing circuit 102 may be configured to determine the times 254 corresponding to a change of sign of the second differentiation signal 252 by determining one or more zero crossings of the second differentiation signal 252. The times 254 (and correspondingly the times 112) may thus correspond to points on the time axis at which a function representing the second differentiation signal 252 intersects the time axis.

[0094] As in Fig. 2D, the processing circuit 102 may include a second zero-crossing detector 206b, which may be configured in the same or similar manner as the (first) zero-crossing detector 206. In short, the second zero-crossing detector 206b may be configured to receive the second differentiation signal and provide (e.g., generate or deliver) as an output a zero-crossing signal 256 ZC_s''(t) having a first signal level when the signal level of the second differentiation signal 252 is equal to or greater than a predefined threshold (e.g., a threshold of zero), and at a second signal level (less than the first signal level, e.g., zero) when the signal level of the second differentiation signal 252 is less than the predefined threshold. The zero-crossing signal 256 may also be referred to as a zero-crossing output signal 256.

[0095] The processing circuit 102 may be configured to determine the times 254 based on the times corresponding to the output of the second zero-crossing detector 206b changing from the first signal level to the second signal level or vice versa. Given the exemplary scenario in Fig. 2D, a rising edge of the second zero-crossing signal 256 may correspond to an inflection point in the detection signal 106 where the concavity changes from upward to downward, and a falling edge of the second zero-crossing signal 256 may correspond to an inflection point in the detection signal 106 where the concavity changes from downward to upward. The second zero-crossing signal 256 may thus provide a compact and convenient representation of relevant shape characteristics of the detection signal 106 (and, accordingly, the received signal 108) to enable further processing.

[0096] In a simple configuration, the second zero-crossing signal 256 may therefore be provided as part of the second output signal (or as part of the output signal 116) for further processing, e.g., alone or together with the zero-crossing signal 208. In other aspects, the processing circuit 102 may be configured in a similar manner as described with respect to Fig. 2B and Fig. 2C, may be configured to further encode the second zero-crossing signal 256 to facilitate subsequent (digital) processing.

[0097] As in Fig. 2E and Fig. 2F, the processing circuit 102 may be further configured to generate another (second) encoded sparse signal 258 representative of the times 254 corresponding to the change in sign of the second differentiation signal 252. The signal 258 may be a sparse signal, e.g., the second encoded sparse signal 258 may be at a first signal level (e.g., a high level different from zero, e.g., greater than zero) in accordance with the times 254 and may be at a second signal level (e.g., a low level, such as substantially zero) in the remaining portions of the second encoded sparse signal 258 (e.g., in accordance with other portions of the differentiation signal 110).The processing circuit 102 may therefore be configured to generate the second output signal by encoding the determined times 252 via the second encoded sparse signal 258. The second encoded sparse signal 258 may thus be provided for further processing (alternatively or in addition to the zero-crossing signal 256). The processing circuit 102 may therefore, in some aspects, be configured to perform the reconstruction of the received signal 108 (and / or time-of-flight refinement) using the second encoded signal 258. In general, the processing circuit 102 may include a second encoding circuit 214b configured to receive the output of the second zero-crossing detector 206b and generate the second encoded sparse signal 258.

[0098] As with regard to Fig. 2B and Fig. 2C, there may be various options for generating a sparsely coded signal 258. In an exemplary configuration, as shown in Fig. 2E, the second encoding circuit 214b may be configured to detect the edges of the second zero-crossing signal 256 to generate the encoded sparse signal 258a. Thus, the encoding circuit 214 may be configured as an edge detection circuit. As shown in Fig. 2E, the second encoding circuit 214b may be configured to generate the encoded sparse signal 258a as a unipolar signal u''(t) or as a pair of signals including a first encoded signal p_s''(t) representing the rising edges of the second zero-crossing signal 256 and a second encoded signal n_s''(t) representing the falling edges of the second zero-crossing signal 256.

[0099] As another example configuration, as in Fig. 2F, the second coding circuit 214b may be configured to differentiate the second zero-crossing signal 256 to generate the second encoded sparse signal 258b diff_s'(t). As shown in Fig. 2F, the second coding circuit 214b may be configured to generate the second encoded sparse signal 258b as a single signal diff_s'(t) or as a pair of signals including a first encoded signal p_s'(t) and a second encoded signal n_s'(t).

[0100] The processing circuit 102 (e.g., its digital portion) may be configured to perform subsequent data processing to derive the measures of interest, such as: determining the number and (temporal) position of the peak(s) in the echo using the encoded second derivative zero-crossing signal; using the position of the main peak to refine the time-of-flight measurement to reduce the running error; determining the number of detected objects in the field of view; and the like.

[0101] Fig. 3 shows a series of diagrams 300a-300f that illustrate the operation of the detection device 100. The diagrams 300a-300f may describe the various processing steps in an exemplary scenario to illustrate the various functionalities that may be related to Fig. 1A to Fig. 2F. The diagrams can represent a signal level of the various signals (in arbitrary units) over time.

[0102] Diagram 300a shows an emitted light pulse 302 (an example of the transmitted signal 122) corresponding to the signal e(t). The emitted light pulse 302 may, for example, be a Gaussian pulse with a pulse duration of approximately 15 ns (FWHM).

[0103] Graph 300b shows an example received signal 304, d(t) (an example of received signal 108). The signal d(t) may correspond to the received light signal, including the attenuated echo(es) of the transmitted pulse 302 after it has struck an object. In the example scenario in Fig. 3, the received signal 304 may contain two overlapping echoes that appear as two peaks in the received light signal d(t), e.g., indicating the reflection of two objects in the field of view.

[0104] As shown in diagram 300c, the received light signal d(t) is converted by the detector into an electrical signal 306 (the signal 306 may be an example of the detection signal 106). After detection, the noisy detected signal s(t) is obtained. In the example scenario in Fig. 3, the noise can have a signal-to-noise ratio of 6 dB, which is filtered by a low-order low-pass filter that replicates the typical bandwidth of the input transimpedance amplifier. In this example, the detected signal s(t) can also be used to generate the stop signal for the time-of-flight measurement, stop(t), using a threshold value ref1.

[0105] Since the received signal is very noisy, heavy low-pass filtering can be applied to produce a "smooth" filtered signal 308 f(t) suitable for differentiation (see graph 300d). To prepare the signal for differentiation, a filter, such as a low-pass filter, can be applied before the differentiation stage to reduce the effects of noise in the derived signal.

[0106] The filtered signal is then differentiated to obtain the differentiated signal 310 s'(t), shown in diagram 300e. The signal 310 s'(t) may be an example of the differentiation signal 110. The input signal s(t) or f(t) may be differentiated, e.g., as a first-order and / or second-order derivative. In analog electronics, an operational amplifier-based circuit may be used. The outputs of the differentiation stage(s) may be the first derivative of the signal, s'(t), and / or the second derivative of the signal, s''(t).

[0107] After detecting the zero crossing, the zero crossing signal 312 enc'(t), illustrated in diagram 300f, may be obtained. The zero crossing signal 312 may be an example of the output signal 116. In this example, no further encoding of the zero crossing signal is performed. In this case, the output signals enc'(t) may correspond to the zero crossing signal ZC_s'(t). To determine an inflection point, a zero crossing of the second derivative s''(t) may be determined (and optionally encoded) in a similar manner.

[0108] Despite its simplicity, the proposed setup allows accurate detection of peaks in the received signal, allowing, for example, correction of the ToF measurement, e.g., to correct the running error.

[0109] Fig. 4A and Fig. 4B show further aspects of the detection device 100 that can be used with the Fig. 1A to Fig. 2F described configuration can be combined.

[0110] According to various aspects, the processing circuit 102 may be configured to delay the generation of the differentiation signal 110 by a predefined time delay from the detection of the received signal 108 by the detection device 100. For example, the processing circuit 102 may be configured to delay the generation of the differentiation signal 110 with respect to the time at which the processing circuit 102 receives the detection signal 106. The predefined time delay may be selected based on an expected duration of the received signal 108, e.g., an expected duration of a signal component of the received signal 108. In some aspects, the predefined time delay may be selected based on a predefined (e.g., known) duration of the transmitted signal 122 corresponding to the received signal 108.The delay can ensure that the signal component of the received signal 108 is fully captured in the detection device 100 before further processing (differentiation, zero-crossing detection, etc.) is performed. The processing circuit 102 can be configured to adjust the propagation time value based on the predefined time delay (if implemented), e.g., it can be configured to subtract the predefined time delay from the measured propagation time.

[0111] In an example implementation, processing circuitry 102 may include an analog delay circuitry 402 configured to impose the predefined time delay on the sense signal 106. The analog delay circuitry 402 may be located upstream of the other components of processing circuitry 102 with respect to the propagation of the sense signal 106 within processing circuitry 102. By way of example, analog delay circuitry 402 may be configured to receive the sense signal 106 and, after the predefined time delay, forward (e.g., provide) the sense signal 106 to the differentiating circuitry(s) of processing circuitry 102. As example components, analog delay circuitry 402 may include an analog delay line or a printed circuit board (PCB) design.

[0112] Depending on the application, it may be desirable to capture a received pulse in its entirety, e.g., including the portion of the signal before s(t) reaches the trigger threshold to generate the stop signal 126. To achieve this while keeping the implementation complexity of the TDC circuit as low as possible, an analog delay can be inserted into the signal path of the derived signal to be captured. Adding an analog delay can serve to balance the implementation complexity of the analog delay against the complexity of the TDC implementation.

[0113] According to various aspects, the processing circuit 102 may be configured to generate the differentiation signal 110 only for those parts of the detection signal 106 whose signal level is greater than a predefined threshold. This configuration may enable the signal processing to be performed without wasting resources on irrelevant parts of the signal, e.g., parts with only noise or excessive noise. In this configuration, the processing circuit 102 may be configured to determine (e.g., measure or evaluate) a signal level of the detection signal 106 and determine a starting time for generating the differentiation signal 110 based on the time at which the signal level of the detection signal becomes greater than a predefined threshold level. The processing circuit 102 may then perform the generation of the differentiation signal from the starting time. The predefined threshold may, for example, beB. be an average noise level.

[0114] In an example implementation, as in Fig. 4B, the processing circuit 102 may include a switching element 404 (e.g., an activation switch) operable to connect or disconnect a signal path to the differentiating circuit(s) of the processing circuit 102. The switching element 404 may thus be operable to connect the signal path to enable the delivery of the detection signal 106 to the differentiating circuit(s) and to interrupt the signal path to prevent the delivery of the detection signal 106 to the differentiating circuit(s). The processing circuit 102 may be configured to provide a control signal to activate the switching element 404 when the signal level of the detection signal 106 is or becomes greater than the predefined threshold level.

[0115] For example, the control signal for activating switching element 404 may be the output signal of a comparator of stop signal generation circuit 140. In an exemplary configuration, stop signal 126 may be provided to switching element 404 as a control signal for activating switching element 404 (and connecting the signal path) when the signal level of detection signal 106 becomes greater than the predefined threshold. For example, stop signal 126 may switch to "high" when the signal level of detection signal 106 becomes greater than the threshold, and such a "high" switching of signal 126 may be a control signal for activating switching element 404.

[0116] The activation switch 404 can be added to the system 100 to perform signal encoding only for portions of the received signal where the received signal is above a certain threshold, since random noise exhibits noise-like zero crossings of the first and second derivatives. In the exemplary configuration mentioned above, the differentiation stages are only activated via the activation switch 404 when the comparator is activated, since there is a sufficient probability of receiving an actual signal.

[0117] In the following, various aspects of the generation of the stop signal 126 as well as further possibilities of coding and reconstructing the received signal 108 with respect to Fig. 5A to Fig. 5G described.

[0118] Fig. 5A and Fig. 5B each show a corresponding exemplary configuration of an analog part 500a, 500b of the processing circuit 102 (e.g., an exemplary configuration of the analog part 150a). Fig. 5A and Fig. 5B illustrate possible configurations for the stop signal generation circuit 502a, 502b of the processing circuit 102 (illustrative, exemplary configurations of the stop signal generation circuit 140). The operation of the stop signal generation circuit 502a, 502b will be described with reference to the Fig. 5C to Fig. 5G. As shown, the stop signal generation circuit 502a, 502b may be part of the analog portion 500a, 500b of the processing circuit 102 together with the signal differentiation circuit 142, which may be configured according to each of the embodiments described with respect to Fig. 1A to Fig. 4B described aspects can be configured.

[0119] According to various aspects, the processing circuit 102 (e.g., the stop signal generation circuit 502a, 502b) may be configured to generate a plurality of quantization signals 510-1...510-N (q1(t)-q N (t)) is generated as in Fig. 5C and Fig. 5D. Each quantization signal 510-1...510-N can be assigned to a respective threshold value 508-1...508-N (ref1-ref N ) and may be representative of the portions of the detection signal 106 that have a signal level within a corresponding range defined by the respective threshold 508-1...508-N. For example, each quantization signal 510-1...510-N may be representative of the portions of the detection signal 106 that have a signal level greater than the corresponding threshold 508-1...508-N.

[0120] As in Fig. 5A and Fig. 5B, the processing circuit 102 (e.g., as part of the stop signal generation circuit 502a, 502b) may include a plurality of comparators 506-1...506-N, each configured to compare the detection signal 106 with one of the threshold values ​​508-1...508-N ref1-ref N compare. The plurality of quantization signals 510-1...510-N may correspond to the output signals of the plurality of comparators 506-1...506-N. Each comparator 506-1...506-N may be configured to generate the respective output signal with a first (e.g., high) level when the signal level of the detection signal is equal to or greater than the respective threshold, or with a second (e.g., low) level when the signal level of the detection signal is equal to or greater than the respective threshold.

[0121] Each comparator 506-1...506-N may be configured to receive the detection signal 106 and a reference signal defining the respective threshold value 508-1...508-N. In one exemplary configuration, the plurality of comparators 506-1...506-N may form a comparator array. For illustration, the plurality of comparators 506-1...506-N may be part of a quantization stage 504a, 504b of the stop signal generation circuit 502a, 502b.

[0122] The plurality of threshold values ​​508-1...508-N may have different values ​​in order to detect the detection signal 106 (and accordingly the received signal 108) in quantized form. For example, the plurality of threshold values ​​508-1...508-N may be spaced from each other at regular intervals. The number of threshold values ​​508-1...508-N (and the corresponding number of comparators 506-1...506-N) may be adjusted depending on the desired granularity of the quantization. The comparator array with N comparators and appropriately selected reference levels may thus be used to detect the signal 106 s(t) in a quantized manner using the comparator output signals 510-1...510-N q1(t), q2(t), ..., q N (t) as in Fig. 5D shown.

[0123] The plurality of quantization signals 510-1...510-N can thus provide a quantized representation of the detection signal 106.

[0124] In an exemplary configuration, the processing circuitry may be configured to encode the quantization signals to generate 510-1...510-N a third output signal representative of one or more third characteristic properties of the received signal detected by the detection device. The third output signal may be a single signal or provided as part of the first or second output signals. According to various aspects, the processing circuitry 102 may be configured to store the third output signal, e.g., in a memory of the processing circuitry 102 (e.g., in a buffer), and retrieve the stored third output signal during subsequent processing.

[0125] According to various aspects, the processing circuit 102 may be configured to perform the reconstruction of the received signal 108 using the plurality of quantization signals 510-1...510-N. For example, the processing circuit 102 may be configured to estimate a signal level of a characteristic portion of the received signal 108 (e.g., a peak or a valley) based on the determined times 112 and the plurality of quantization signals 510-1...510-N, e.g., based on which quantization signal(s) is / are at a high level corresponding to the time 112 of interest.

[0126] As with regard to Fig. 1B and Fig. 1C, comparing the signal level of the detection signal 106 with a threshold value may define a stop signal 126 for the time-of-flight measurement. In the configuration with a plurality of comparators 506-1...506-N, the processing circuit 102 may be configured to determine the arrival time of the received signal 108 and generate the corresponding stop signal 126 based on one of the quantization signals 510-1, e.g., the quantization signal 510-1 associated with the smallest threshold value among the quantization signals 510-1...510-N. By way of example, the processing circuit 102 may be configured to use the output signal of one of the comparators 506-1 as the stop signal 126, e.g., the comparator receiving the reference signal with the lowest value (e.g., the lowest voltage). The output signal of this comparator 506-1, which assumes a high value, can determine the arrival time of the received signal 108 (e.g.its signal component). According to various aspects, the quantization signal 510-1 used as stop signal 126 may also be provided as a control signal for a switching element 404 of the signal differentiation circuit 142 (e.g., to differentiate only relevant parts of the detection signal).

[0127] The comparator arrangement can therefore perform a comparison of the instantaneous signal level with corresponding reference levels ref1(t). The reference levels can be either constant or time-varying, e.g., they can be increased or decreased with increasing time relative to the start(t) signal 120. The reference levels can also be adjusted based on the timing or other signal characteristics (amplitude) of previously measured signals, or based on signal characteristics derived from some form of knowledge about the expected signal.

[0128] In other cases, however, the processing circuit 102 may have a simpler configuration with only one comparator 506-1, whose output signal 510-1 may be used as the stop signal 126 (see Fig. 5C). In such a configuration, the at least one comparator 508-1 can be used to detect pulse events to generate a stop signal 126 for the ToF measurement and to trigger the TDC readout process.

[0129] According to various aspects, the processing circuit 102 may be configured to further process the quantization signals 510-1...510-N to generate a sparser representation that may facilitate subsequent processing. There may be various options and configurations for generating the sparse representation, similar to the description with respect to Fig. 2B and Fig. 2C. In general, the processing circuit 102 (e.g., as part of the stop signal generation circuit 502a, 502b) may include an encoding stage 520a, 520b configured to receive the quantization signal(s) 510-1...510-N and provide as output a coded sparse signal 522g(t) providing a sparse and compact representation of the quantization signals 510-1...510-N.

[0130] In various aspects, the processing circuit 102 (e.g., the stop signal generation circuit 502a, 502b) may be configured to generate a plurality of edge detection signals 512-1...512-N d1(t)-d N (t) generated (see Fig. 5F). Each edge detection signal 512-1...512-N may be associated with a corresponding quantization signal 510-1...510-N and may be representative of times at which the corresponding quantization signal 510-1...510-N has a (rising or falling) edge. For example, each edge detection signal 512-1...512-N may be representative of times at which the signal level of the detection signal 106 becomes greater or less than the threshold level of the corresponding quantization signal 510-1...510-N. Such times may correspond to the signal level of the acquisition signal 106 changing from less than / greater than the threshold level to greater than / less than the threshold level. The edge detection signals 512-1...512-N thus encode further information about the waveform of the detection signal 106 (and the reception signal 108), so that in some aspects, the processing circuit 102 may be further configured to perform the reconstruction of the reception signal 108 using the plurality of edge detection signals 512-1...512-N. The processing circuit 102 may be configured to generate the third output signal by encoding the plurality of quantization signals 510-1...510-N over the plurality of edge detection signals 512-1...512-N.

[0131] To generate the edge detection signals 512-1...512-N, as in Fig. 5A, the coding stage 520a may include an edge detection stage 524a. In this configuration, the comparator output signals 510-1...510-N q1(t), q2(t), ..., q N (t) each pass through the edge detection stage 524a, which generates the output signals 512-1...512-N d1(t), d2(t), ..., dN (t). The edge detection stage 524a can be implemented in various ways and with varying degrees of accuracy. In a simple configuration, the edge detection stage 524a can comprise a plurality of simple high-pass filters 526-1...526-N, e.g., a plurality of low-order RC filters, with an appropriately chosen time constant to approximately perform differentiation of the comparator output signals 510-1...510-N.

[0132] The idea behind performing edge detection is to generate a signal 522 that encodes the changes in the comparator output signals and to generate a signal that is "sparse" in the sense that it is in the zero state most of the time. Assuming that the detected signal is continuous with a finite slope, the edges of the comparator output signals 510-1...510-N q1(t), q2(t), ..., q N(t) do not coincide in time, which in turn means that the sparse signals 512-1...512-N d1(t), d2(t), ..., d N (t) will not be in a non-zero state at the same time.

[0133] Based on this observation, the sparse signals 512-1...512-N d1(t), d2(t), ..., d N (t) without overlap (ie without matching non-zero states) into a single signal 522, e.g. by summation, and we obtain the merged signal g(t) = d1(t) + d2(t) + ...+ d N (t), see Fig. 5E. In the configuration in Fig. 5A, the processing circuit 102 may include (as part of the encoding stage 520a) a summing stage 528a configured to combine the edge detection signals 512-1...512-N into a single encoded signal 522.

[0134] As an alternative approach, as in Fig. 5B, the edge detection and merging steps can be inverted (see also Fig. 5F). In this configuration, the encoding stage 520b may include a summing stage 528b configured to receive the quantization signals 510-1...510-N and combine them (all) into a summing signal 532. The encoding stage 520b may further include an edge detection stage 530b configured to receive the summing signal 532 and generate an encoded sparse signal 528 by detecting the edges of the summing signal 532 sum(t). In an exemplary configuration, the edge detection stage 530b may be implemented as a differentiator, given the quadratic shape of the summing signal 532.

[0135] In both configurations, the coding stage 520a, 520b can provide as output the encoded sparse signal 522, which can provide a compact representation of the waveform of the detection signal 106. The encoded sparse signal 522 can represent a plurality of events (a plurality of pulses), each corresponding to a change in the signal level of the detection signal 106, e.g., from less than a threshold value 508-1...508-N to more than a threshold value 508-1...508-N (a positive pulse) or vice versa (a negative pulse). The sequence of events / pulses in the encoded signal 522 can thus enable an estimation of the temporal behavior of the detection signal 106. In various aspects, the processing circuit 102 may be configured to (further) use the encoded signal 522 to reconstruct the received signal 108.

[0136] As in Fig. 5E and Fig. 5F, the encoded sparse signal 522 may include pulses of positive or negative polarity, depending on the variation of the detection signal 106. To provide a more convenient representation for digital processing, the processing circuit 102 may, in some aspects, be configured to generate one or more unipolar representations of the encoded signal (see Fig. 5G).

[0137] In the configuration of Fig. 5A, the processing circuit 102 may, for example, include a rectifier stage 534a (a rectifier circuit) configured to receive the encoded signal 522 and provide as an output a rectified unipolar signal 536. For example, the sum signal 522 is used after summation to generate the unipolar signal 536 u(t), e.g., by rectification. In another embodiment, Fig. 5B, the processing circuit 102 may include a polarity separation and rectification stage 538b configured to receive the encoded signal 522 and provide as output two unipolar signals p(t), n(t) (as output 536b), e.g., one signal p(t) containing the positive pulses of the encoded branch signal 522 and another signal n(t) containing the rectified negative pulses of the encoded branch signal 522.

[0138] In one exemplary configuration, the unipolar signal(s) 536, 536b may be provided as output 540a, 540b of the stop signal generation circuit 502a, 502b, which encodes information about the shape of the detection signal 106 that the processing circuit 102 may use to reconstruct the received signal. In other configurations, the encoded sparse signal 522 itself may be provided as output 540a, 540b, as mentioned above.

[0139] The unipolar signal 536 provides a compact and sparse representation, allowing for convenient digital processing. Since the resulting unipolar signal 536 u(t) has only two states (i.e., a zero state and a non-zero state), it is suitable, for example, as input to a subsequent (binary) TDC stage. As shown in Fig. 5G, however, during this processing stage, the information about the polarity of the non-zero states in the coded signal 522 and thus the direction of the edge change in the edge detection signals 512-1...512-N d1(t), d2(t), ..., d N (t) and the quantization signals 510-1...512-0 q1(t), q2(t), ..., q N(t) is lost. Therefore, according to various aspects, the processing circuit 102 may be configured to recover the information about the "polarity" of the signal level changes encoded in the unipolar signal 536 from the determined times 112 corresponding to the sign changes of the differentiation signal 110.

[0140] For example, the processing circuit 102 can be configured to use the unipolar signal 536 in combination with the output 116 of the signal differentiation circuit 142 to reconstruct the received signal 108. In a preferred configuration, as shown in Fig. 5G, processing circuitry 102 may be configured to use unipolar signal 536 in combination with zero-crossing signal 208. As illustrated, the information encoded in zero-crossing signal 208 enables recovery of encoded signal 522 from unipolar signal 536.

[0141] To illustrate, the zero-crossing signal 208 encodes the zero crossings of the first derivative 110, which can be used, for example, to determine the position of peaks in the acquisition signal 106 (and in the acquired signal 108). The unipolar signal 536, on the other hand, encodes the sample points of the acquisition signal 106. However, because information was lost during the encoding process of the unipolar signal 536, the unipolar signal 536, when used alone, can only provide a partial and crude reconstruction of the acquired signal 108. However, using the derivative signal 110 or the zero-crossing signal 208, which essentially also represents the direction of the edge transitions, the processing circuit 102 can reconstruct the polarity information in the coded signal 522 and thus the sparse signals 512-1...512-N d1(t), d2(t), ..., d N (t) and the comparator signals 510-1,...510-N q1(t), q2(t), ..., q N (t).

[0142] The approach described here can thus complement and improve the capabilities of an approach based solely on a detector with a comparator array used to quantify the amplitude information. For many practical applications, it is not the exact shape or amplitude curve of the signal that is relevant, but only certain pulse characteristics such as peaks or inflection points, which can be determined by differentiation.

[0143] The differentiation-based strategy allows the time of local minima and maxima of the signal to be determined directly by using a preprocessing stage that determines the first derivative, which is used as input for signal acquisition via a TDC delay chain. Likewise, the time of the signal's inflection points can be determined based on the second derivative. This allows the signal acquisition setup to be simplified, for example, in cases where certain properties of the signal shape are known in advance. Furthermore, it is also possible to use the comparator array approach (see Fig. 5A and Fig. 5B) with the signal derivative(s) approach to enable a more robust determination of the signal shape, e.g., in the case of overlapping double pulses. In general mathematical terms, as many sample points can be used to reconstruct a signal shape as there are free variables in the mathematical expression describing the signal. These sample points can be either direct instantaneous amplitude values ​​or special points based on the first and / or second derivative, or a combination of both approaches.

[0144] In the present disclosure, the additional features can be captured via an easy-to-implement analog preprocessing stage based on differentiation, a low-complexity digitization stage using zero-crossing detectors, and signal acquisition via a (fine) TDC stage. Furthermore, the acquisition of the additional signal properties can be realized through a synergistic use of components, resulting in cost-effective implementations. In general, the implementation of the adapted method described here enables the acquisition of specific pulse characteristics, which can significantly simplify the interpretation or processing of the pulse data if, for example, the expected pulse shape is known. Furthermore, it is conceivable to adequately reconstruct a signal by combining amplitude information and other pulse characteristics.Essentially, the first derivative coding presented here makes it possible to use a simplified coding scheme that allows to reduce the number of processing steps for acquiring the acquired signal sample points.

[0145] Fig. 6 shows a digital processing circuit 600 in a schematic view, according to various aspects. The digital processing circuit 600 may be an exemplary configuration of the digital portion 150b of the processing circuit 102, e.g., an exemplary configuration of the time-of-flight determination circuit 144.

[0146] According to various aspects, the digital processing circuit 600 may include a coarse TDC circuit 602, a fine TDC circuit 604, a time-of-flight calculation circuit 606, and a signal reconstruction circuit 608.

[0147] For example, coarse TDC circuitry 602 may be implemented by counting clock cycles to determine the propagation time of a transmit signal (e.g., transmit signal 122) with a lower granularity. Coarse TDC circuitry 602 may be configured to receive a start signal 610 (start(t), e.g., start signal 120), a stop signal 612 (stop(t), e.g., stop signal 126), and a clock signal 614, and may be configured to provide (e.g., generate) a coarse timing signal 616 based on start signal 610, stop signal 612, and clock signal 614. For example, the coarse timing signal 616 may include a number N of clock cycles between a first rising edge of the start signal 610 and a first rising edge of the stop signal 612. In an example configuration, the start signal 610 may be provided by a higher-level system, e.g., the transmitter of a LIDAR system.In the case of a LIDAR, the start signal 610 may indicate the time at which the light pulse was emitted. Other applications may provide different start signals depending on the type and timing of the application.

[0148] For example, the fine TDC circuit 604 may include a tapped delay line to determine the propagation time with finer granularity. When implementing a tapped delay line, the input signal may be fed (serially) into the tapped delay line, thereby digitizing it, storing it, and making it available for parallel readout.

[0149] The fine TDC circuit 604 may be configured to receive the stop signal 612, the clock signal 614, and one or more encoded signals 618, 620. For example, the fine TDC circuit 604 may be configured to receive a first encoded signal 618 (e.g., the encoded signal 538a, 538b) from a stop signal generation circuit and / or a second encoded signal 620 (e.g., the output signal 116) from a signal differentiation circuit.

[0150] The fine TDC circuit 604 may be configured to generate a fine time measurement signal 622 based on the stop signal 612, the clock signal 614, and the information encoded in the one or more encoded signals 618, 620, e.g., using time points encoded therein. For example, the fine time measurement signal 622 may include a number M of elementary time units (with a given time duration) representing a fine time, which may be generated based on the time points encoded in the one or more encoded signals 618, 620 and used as adjustment values ​​for the coarse time measurement signal 616.

[0151] The flight time calculation circuit 606 may be configured to receive the coarse time measurement signal 616 and the fine time measurement signal 622 and to calculate the flight time associated with the transmission signal based on the coarse time measurement signal 616 and the fine time measurement signal 622. The flight time calculation circuit 606 may be configured to generate a (digital) measurement signal 624 representing the determined flight time.

[0152] The fine TDC circuit 604 may be further configured to perform a time-to-digital conversion of the encoded signals 618, 620 to provide one or more corresponding digitized signals 618d, 620d. The fine TDC circuit 604 may be configured to provide the one or more digitized signals 618d, 620d to the signal reconstruction circuit 608, which may be configured to generate a reconstructed signal 626 based on the received digitized signals 618d, 620d that encodes information about the characteristics of a received signal detected by the detection device. The reconstructed signal 626 may thus be a reconstructed version of the received signal based on the characteristic properties encoded in the encoded signals 618, 620.

[0153] Fig.Figure 7 shows a LIDAR system 700 in a schematic view, according to various aspects. The LIDAR system 700 may be an exemplary application scenario for the detection device and detection method described herein.

[0154] The LIDAR system 700 may include a LIDAR transmitter 702 (e.g., an example of the signal emission circuit 100a) and a LIDAR receiver 704 (an example of the signal detection circuit 100b).

[0155] The LIDAR transmitter 702 may include a laser source 706 and a driver 708 configured to control the laser emission of the laser source 706. The LIDAR system 700 may further include emission optics 710 to direct the laser light toward the field of view of the LIDAR system. The LIDAR transmitter 702 may thus emit a laser signal 712 toward the field of view of the LIDAR system 700. The laser signal 712 (an example of the transmission signal 122) may be incident on an object 714 in the field of view and reflected back to the LIDAR system 700.

[0156] The LIDAR receiver 704 may receive a reflected signal 716 (an example of the received signal 108) corresponding to the back reflection of the laser signal 712. The LIDAR system 700 may further include receive optics 718 to direct light from the field of view to the LIDAR receiver.

[0157] The LIDAR receiver 704 may include a detector 720 with one or more photodiodes 722 and an amplifier 724 (e.g., a transimpedance amplifier). The detector 720 may be configured to provide a detection signal 726 (an example of the detection signal 106) to a processing circuit 728 (an example of the processing circuit 102) of the LIDAR transmitter 704.

[0158] The processing circuit 728 may include an analog signal processing circuit 730a and a digital signal processing circuit 730b.

[0159] The analog signal processing circuit 730a may include one or more comparators 732 (e.g., a comparator array) configured to generate a stop signal 734 for measuring the time of flight of the laser signal 712. Optionally, the analog signal processing circuit 730a may include an encoding circuit 736 configured to encode the output signal of the comparator(s) 732 and generate an encoded signal 738.

[0160] According to the configuration proposed here, the analog signal processing circuit 730a may include a first differentiation circuit 740 and an encoding circuit 742 to generate a first-order derivative of the detection signal 726 and generate a first encoded signal 744 representative of the times corresponding to the sign changes of the first derivative. Additionally, the processing circuit 730a may include a second differentiation circuit 746 and an encoding circuit 748 to generate a second-order derivative of the detection signal 726 and generate a second encoded signal 750 representative of the times corresponding to the sign changes of the second derivative.

[0161] The digital processing circuit 730b may include a coarse TDC circuit 752 and one or more fine TDC stages 754-1, 754-2, 754-3. The coarse TDC circuit 752 may be configured to generate a coarse measurement signal 756 based on the stop signal 734 and a start signal 758 provided by a measurement control circuit 760 of the LIDAR system 700. The fine TDC stages 754-1, 754-2, 754-3 may be configured to generate a corresponding digitized version 762-1, 762-2, 762-3 of the encoded signals from the analog processing circuit 730a for subsequent signal reconstruction and processing.

[0162] In various respects, time-of-flight sensor applications, including LIDAR, can leverage certain characteristics of the acquired signals to improve sensor performance or unlock new functionality. For example, knowing the amplitude of the detected signal allows for inferences about channel attenuation. This, in turn, can be used, for example, in a LIDAR application to infer the properties of a detected object. Similarly, knowing the exact position of the peak in an acquired signal helps improve the accuracy of time-of-flight measurements (i.e., the so-called "walk error" can be reduced). Another example: knowing multiple peaks in an acquired signal can allow inferences about whether the edge of an object was hit by the emitted light pulse.

[0163] The approach described here enables the direct measurement of specific features of the signal, e.g., the exact timing of the peak(s), using a different signal processing chain than conventional configurations. The proposed approach significantly reduces the amount of data processing required after signal acquisition by providing the ability to directly capture relevant timing information in the observed signal, e.g., by directly capturing the timing information associated with peaks or inflection points. In a highly simplified approach, no data processing may be required at all, as the acquired output of the first and / or second differentiating stages is sufficient to determine the desired signal characteristic.

[0164] The term "amplitude" can be used here to describe the height of a peak, e.g., the height of a pulse. The term "amplitude" can describe the signal level of the signal at the peak relative to a reference value for the signal level. The term "amplitude" can also be used here in reference to a signal that is not a symmetrical periodic wave, e.g., also in reference to an asymmetrical wave (e.g., in reference to a signal with periodic pulses in one direction). In this context, the term "amplitude" can be understood to describe the amplitude of the signal (e.g., the peak value) measured from the reference value of the signal level.

[0165] The term "processor" or "processing circuit" as used herein can be understood as any type of technological unit that enables the processing of data. The data can be processed according to one or more specific functions performed by the processor or processing circuit. Furthermore, a processor or processing circuit can be understood as any type of circuit, e.g., any type of analog or digital circuit. A processor or processing circuit can therefore be or include an analog circuit, a digital circuit, a mixed-signal circuit, a logic circuit, a processor, a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field-programmable gate array (FPGA), an integrated circuit, an application-specific integrated circuit (ASIC), etc., or any combination thereof.Any other implementation of the respective functions may also be understood as a processor or processing circuit. It is understood that two (or more) of the processors or processing circuits described herein may be implemented as a single unit with equivalent functionality or the like, and conversely, that a single processor or processing circuit described herein may be implemented as two (or more) separate units with equivalent functionality or the like.

[0166] The term "calculate" as used here includes both "direct" calculations using a mathematical expression / formula / relationship and "indirect" calculations using lookup or hash tables and other array indexing or searching operations.

[0167] The terms "differential," "differentiating," and "differentiated" can be used here in their general mathematical sense to refer to a process of determining the derivative of a function. The terms "differential," "differentiating," and "differentiated" can be used here with respect to signal processing to refer to a process of determining changes in the signal level (e.g., its amplitude) over time, e.g., a process of determining changes in the signal's slope over time.

[0168] While various embodiments have been particularly shown and described with reference to certain aspects, it should be apparent to those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope as defined by the appended claims. The scope of applicability is therefore indicated by the appended claims, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be embraced. LIST OF REFERENCE SYMBOLS 100 detection device 100a circuit for signal output 100b signal detection circuit 102 Processing cycle 104 signal processing methods 106 detection signal 108 Received signal 110 Differentiation signal 112 Time 114 Characteristic part 116 Output signal 118 Detector 120 Start signal 122 transmit signal 124 objects 126 Stop signal 128 Methods for generating stop signals 130 Time-to-digital conversion 132 Digital Signal 134 Signal source 136 controllers 138 Control signal 140 Circuit for generating a stop signal 142 Circuit for signal differentiation 144 Circuit for determining the flight time (Time-fo-Flight) 150a Analogue part 150b Digital Part 202 Differentiation circuit 202b Differentiation circuit 204 filter circuit 206 Zero crossing detector 206b zero crossing detector 208 Zero crossing signal 210 Supplement 212 operational amplifiers 214 encoder circuit 214b encoder circuit 216 Coded sparse signal 216a Coded sparse signal 216b Coded sparse signal 220 deposit 222 differential amplifiers 224 Reference signal 240 supplement 242 flip-flops 244 clock signal 246 XOR logic gates 252 Second differentiation signal 254 Time 256 zero crossing signal 258 Coded sparse signal 258a Coded sparse signal 258b Coded sparse signal 300a graphics 300b graphics 300c graphics 300d graphics 300e graphics 300f graphics 302 light pulse 304 Received signal 306 Electrical Signal 308 Filtered signal 310 Differentiated signal 312 zero crossing signal 402 Analog delay circuit 404 switching element 500a Analogue part 500b Analogue part 502a Circuit for generating a stop signal 502b Circuit for generating a stop signal 504a Quantization level 504b Quantization level 506-1 Comparator 506-N Comparator 508-1 Threshold 508-N threshold 510-1 Quantization signal 510-2 Quantization signal 510-3 Quantization signal 510-4 Quantization signal 510-5 Quantization signal 510-6 Quantization signal 510-7 Quantization signal 510-N quantization signal 512-1 Signal for edge detection 512-2 Edge detection signal 512-3 Edge detection signal 512-4 Edge detection signal 512-5 Edge detection signal 512-6 Edge detection signal 512-7 Edge detection signal 512-N edge detection signal 520a coding level 520b coding level 522 Coded sparse signal 524a Edge detection stage 526-1 High-pass filter 526-N high-pass filter 528a Summation phase 528b Summation phase 530b Edge detection stage 532 Summation signal 534a Rectifier stage 536 Unipolar signal 536b Unipolar signal 538b Rectifier stage 600 Digital processing circuit 602 coarse TDC circuit 604 Fine TDC circuit 606 Circuit for flight time calculation 608 Signal reconstruction circuit 610 Start signal 612 Stop signal 614 clock signal 616 Coarse measurement signal 618 Coded Signal 618d Digitized signal 620 Coded Signal 620d Digitized Signal 622 Fine measuring signal 624 measurement signal 626 Reconstructed signal 700 LIDAR system 702 LIDAR transmitters 704 LIDAR receivers 706 Laser Source 708 drivers 710 emission optics 712 Laser Signal 714 Object 716 Reflected signal 718 receiving optics 720 detector 722 photodiodes 724 amplifiers 726 detection signal 728 processing circuit 730a Circuit for processing analog signals 730b Digital Signal Processing Circuit 732 comparators 734 Stop signal 736 coding circuit 738 Coded Signal 740 Differentiation circuit 742 coding circuit 744 Coded signal 746 Differentiation circuit 748 coding circuit 750 Coded Signal 752 coarse TDC circuit 754-1 Fine TDC stage 754-2 Fine TDC stage 754-3 Fine TDC stage 756 Coarse measurement signal 758 start signal 760 Control circuit for measurement 762-1 Digitized signal 762-2 Digitized signal 762-3 Digitized signal QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 127 081.5

[0001] DE 10 2021 101 790 A1

[0020]

Claims

[1] A detection device (100) comprising: a processing circuit (102) configured to: to receive a detection signal (106) representative of a received signal (108) detected by the detection device (100), wherein the received signal (108) is associated with a corresponding predefined transmitted signal (122) and / or with one or more expected signal features; generate a differentiation signal (110) representative of a rate of change of a signal level of the detection signal (106) over time; Determining times (112) corresponding to a change in the sign of the differentiation signal (110); and to encode the determined times (112) in order to generate an output signal (106) which is representative of one or more characteristic properties of the received signal (108) detected by the detection device (100). [2] The detection device (100) according to claim 1, wherein the processing circuit (102) is further configured to: receive a start signal (120) representing a start time for the transmission of the predefined transmission signal (122); generate a stop signal (126) indicating an arrival time of the received signal (108) at the detection device (100); Calculating a flight time associated with the predefined transmission signal (122) based on the start signal (120) and the stop signal (126); and to change a value of the calculated propagation time based on the one or more characteristic properties of the received signal (108) encoded in the output signal (116). [3] The detection device (100) according to claim 2, wherein, to calculate the time of flight, the processing circuit (102) is configured to perform a time-to-digital conversion to generate a digital signal representative of a time difference between the start signal (120) and the stop signal (126). [4] The detection device (100) according to claim 2 or 3, wherein the one or more characteristic properties comprise temporal positions within the received signal (108) of one or more peaks and / or one or more valleys of the received signal (108) in accordance with the determined times (112); and wherein the processing circuit (102) is configured to modify the value of the calculated time of flight based on the temporal position of a first peak within the received signal (108). [5] The detection device (100) according to one of claims 1 to 4, wherein the processing circuit (102) is further configured to: generate a second differentiation signal (252) representing a rate of change of a signal level of the differentiation signal (110) over time; Determining second times (254) corresponding to a change in the sign of the second differentiation signal (252) from positive to negative or from negative to positive; and to encode the determined second times (254) to generate a second output signal representing one or more second characteristic properties of the received signal (108) detected by the detection device (100). [6] The detection device (100) according to one of claims 1 to 5, wherein the processing circuit (102) comprises an analog differentiation circuit configured to: receive the detection signal (106); perform an analog differentiation of the detection signal (106) and provide the differentiation signal (110) as the output of the analog differentiation. [7] The detection device (100) according to one of claims 1 to 6, wherein the one or more characteristic properties of the received signal (108) comprise a number of peaks in the received signal (108) and / or a number of valleys in the received signal (108) and / or a time interval between successive peaks in the received signal (108) and / or a slope of the received signal (108) and / or a time interval between a reference time and one or more peaks and / or valleys in the received signal (108). [8] The detection device (100) of any one of claims 1 to 7, wherein the processing circuit (102) is further configured to filter the received detection signal (106) prior to generating the differentiation signal (110) to reduce the noise level in the detection signal (106). [9] The detection device (100) according to any one of claims 1 to 8, wherein the processing circuit (102) is configured to determine the times (112) corresponding to a change of a sign of the differentiation signal (110) by determining one or more zero crossings of the differentiation signal (110). [10] The detection device (100) according to claim 9, wherein the processing circuit (102) comprises a zero-crossing detector (206) configured to provide a zero-crossing output signal (208) having a first signal level when the signal level of the differentiation signal (100) is equal to or greater than a predefined threshold, and to provide the zero-crossing output signal (208) having a second signal level when the signal level of the differentiation signal (100) is less than the predefined threshold; and wherein the processing circuit (102) is configured to determine the times (112) corresponding to a change of a sign of the differentiation signal (110) based on the times corresponding to the zero-crossing output signal (208) switching from the first signal level to the second signal level, or vice versa. [11] The detection device (100) according to one of claims 1 to 10, wherein the processing circuit (102) is further configured to: to generate the output signal (116) by coding the determined times (112) via a coded sparse signal (216), wherein the coded sparse signal (216) has a signal level other than zero in accordance with the times (112) corresponding to the change in sign of the differentiation signal (110) and has a signal level of substantially zero in the remaining portions of the coded sparse signal (216). [12] The detection device (100) according to one of claims 1 to 11, wherein the processing circuit (102) is further configured to: generate a plurality of quantization signals (510); wherein each quantization signal (510) is associated with a corresponding threshold value (508); wherein each quantization signal (510) is representative of the portions of the detection signal (106) having a signal level within a corresponding range defined by the respective threshold level (508); and encode the quantization signals (510) to generate a third output signal representing one or more third characteristic properties of the received signal (108) detected by the detection device (100). [13] The detection device (100) according to claim 12, wherein the processing circuit (102) is further configured to: Generating the third output signal by encoding the plurality of quantization signals (510) via a plurality of edge detection signals (512), wherein each edge detection signal (512) is connected to a corresponding quantization signal (510) and the corresponding threshold value (508), wherein each edge detection signal (512) is representative of times at which the signal level of the detection signal (106) becomes greater than the corresponding threshold value (508) or becomes less than the corresponding threshold value (508). [14] The detection device (100) according to one of claims 1 to 13, wherein the transmission signal (122) is an emitted light signal, and wherein the received signal (108) is a reflected light signal corresponding to a reflection of the transmitted light signal in the direction of the detection device (100). [15] A time-of-flight detector (100) comprising: a processing circuit (102) configured to: receive a start signal (120) indicating a start time for the transmission of a transmission signal (122); receive a detection signal (106) representative of a received signal (108) detected at the time-of-flight detector (100), the received signal (108) comprising a reflection of the transmitted signal (122) toward the time-of-flight detector (100); to generate a stop signal (126) indicating an arrival time of the received signal (108) at the time of flight detector (100); perform a time-to-digital conversion to calculate a propagation time associated with the transmission signal (122) based on the start signal (120) and the stop signal (126); generate a differentiation signal (110) representing a rate of change of a signal level of the detection signal (110) over time; Determining times (112) corresponding to a change in the sign of the differentiation signal (110); and change a value of the calculated flight time on the basis of the determined times (112).

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