CN111527419A

CN111527419A - Sampling circuit, sampling method, distance measuring device and mobile platform

Info

Publication number: CN111527419A
Application number: CN201880068016.2A
Authority: CN
Inventors: 黄森洪; 梅雄泽; 刘祥; 洪小平
Original assignee: SZ DJI Technology Co Ltd
Current assignee: SZ DJI Technology Co Ltd
Priority date: 2018-12-03
Filing date: 2018-12-03
Publication date: 2020-08-11
Also published as: WO2020113360A1

Abstract

A sampling circuit (130), a method for using the same, a distance measuring device (200) and a mobile platform are provided. The sampling circuit (130) comprises: the sampling circuit (130) also comprises a control module; the time-to-digital conversion module is used for receiving an electric signal obtained by converting the optical pulse signal, comparing the electric signal with a preset threshold value, and acquiring time information corresponding to the electric signal; the analog-to-digital conversion module is used for receiving the electric signal obtained by converting the optical pulse signal and acquiring the amplitude of the electric signal corresponding to the acquisition time in the sampling clock frequency; and the control module is used for selecting and calculating the signals acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module to obtain the parameter values of the optical pulse signals.

Description

Sampling circuit, sampling method, distance measuring device and mobile platform

Technical Field

The invention relates to the technical field of laser radars, in particular to a sampling circuit, an application method, a distance measuring device and a mobile platform.

Background

The laser radar is a radar system that detects a characteristic amount such as a position and a velocity of a target by emitting a laser beam. The photosensitive sensor of the laser radar can convert the acquired optical pulse signal into an electric signal, and the time information corresponding to the electric signal is acquired based on the comparator, so that the distance information between the laser radar and the target object is obtained.

However, in the products related to laser ranging, such as laser radar, it is generally necessary to extract various pulse information, such as energy, arrival time, shape parameters, etc., so as to more comprehensively and accurately reflect the object information of the detected scene. Sampling and processing of pulsed signals is often a bottleneck technique related to system performance.

Therefore, further improvements in the current apparatus and methods for acquiring pulse information are needed.

Disclosure of Invention

A first aspect of the present invention provides a sampling circuit, comprising: the sampling circuit comprises a time-to-digital conversion module, an analog-to-digital conversion module and a control module, wherein the time-to-digital conversion module and the analog-to-digital conversion module are arranged in parallel;

the time-to-digital conversion module is used for receiving an electric signal obtained by converting an optical pulse signal, comparing the electric signal with a preset threshold value, and acquiring time information corresponding to the electric signal;

the analog-to-digital conversion module is used for receiving the electric signal obtained by converting the optical pulse signal and acquiring the amplitude of the electric signal corresponding to the acquisition time in the sampling clock frequency;

and the control module is used for selecting and calculating the signals acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module to obtain the parameter values of the optical pulse signals.

Optionally, the time-to-digital conversion module includes a plurality of channels, each of which includes a comparator and a time-to-digital converter, wherein a first input end of the comparator is configured to receive an electrical signal converted from the optical pulse signal, a second input end of the comparator is configured to receive a preset threshold of the comparator, an output end of the comparator is configured to output a result of the comparison operation, and the time-to-digital converter is electrically connected to an output end of the comparator and is configured to extract time information corresponding to the electrical signal according to the result of the comparison operation output by the comparator;

and the preset thresholds of the comparators in the different channels are different.

Optionally, the analog-to-digital conversion module comprises at least one analog-to-digital converter for acquiring an amplitude of the electrical signal corresponding to the acquisition time.

Optionally, the control module is configured to calculate the selected signal in a fitting manner to restore a graph of the optical pulse signal;

or the control module is used for calculating the selected signal in an explicit statistic manner to obtain a parameter value of the optical pulse signal.

Optionally, the control module collects at least part of the signals of the time-to-digital conversion module and at least part of the signals collected by the analog-to-digital conversion module to perform the fitting.

Optionally, the control module is further configured to convert the samples of the time-to-digital conversion module into samples of the analog-to-digital conversion module;

or the control module is also used for converting the sampling of the analog-to-digital conversion module into the sampling of the time-to-digital conversion module.

Optionally, the control module is configured to calculate a sampled signal of the analog-to-digital conversion module in a fitting manner to obtain a graph of the optical pulse signal, and then calibrate a preset threshold and corresponding time information on the graph of the optical pulse signal.

Optionally, when the control module selects the signal:

when the width of the optical pulse signal is smaller than a pulse width set value, selecting a signal acquired by the time-to-digital conversion module; and/or

When the pulse height of the optical pulse signal is smaller than a pulse height set value, selecting a signal acquired by the analog-to-digital conversion module; and/or

When the width of the optical pulse signal is greater than a pulse width set value and the pulse height of the optical pulse signal is greater than a pulse height set value, if the accuracy required by the arrival time and the pulse width information of the optical pulse signal is higher, at least selecting a signal acquired by the time-to-digital conversion module; and at least selecting the signal acquired by the analog-to-digital conversion module if the pulse energy and amplitude information of the optical pulse signal requires higher precision.

Optionally, the parameter values comprise at least one of pulse arrival time, pulse width, pulse energy and amplitude.

The invention also provides a sampling method based on the sampling circuit, which comprises the following steps:

receiving an electric signal obtained by converting the optical pulse signal through a time-to-digital conversion module, comparing the electric signal with a preset threshold value, and acquiring time information corresponding to the electric signal;

receiving an electric signal obtained by converting the optical pulse signal through an analog-to-digital conversion module, and acquiring an amplitude signal of the electric signal corresponding to acquisition time in sampling clock frequency;

and selecting and calculating the signals acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module to obtain the parameter values of the optical pulse signals.

Optionally, the time-to-digital conversion module includes a plurality of channels, and the plurality of channels receive the electrical signal in parallel, perform comparison operation on the electrical signal, and acquire time information corresponding to the electrical signal.

Optionally, the plurality of channels are respectively provided with different preset thresholds so as to receive the electrical signals in parallel and perform comparison operation on the electrical signals.

Optionally, the step of selecting a signal and calculating to obtain a parameter value of the optical pulse signal includes:

calculating the selected signal in a fitting mode to restore the graph of the optical pulse signal;

or calculating the selected signal by adopting an explicit statistic method to obtain a parameter value of the optical pulse signal.

Optionally, at least a part of the signals of the time-to-digital conversion module and a part of the signals collected by the analog-to-digital conversion module are selected for the fitting.

Optionally, after selecting the signals acquired by the time-to-digital conversion module and the analog-to-digital conversion module, before performing the calculation, the method further includes:

converting the sampling of the time-to-digital conversion module into the sampling of the analog-to-digital conversion module;

Optionally, a fitting manner is adopted to calculate the sampled signal of the analog-to-digital conversion module to obtain a graph of the optical pulse signal, and then a preset threshold and corresponding time information are calibrated on a graph structure of the optical pulse signal.

Optionally, when the signal is selected,

Optionally, the parameter values comprise at least one of pulse arrival time, pulse width, pulse energy and pulse amplitude.

The present invention also provides a ranging apparatus, comprising:

a light emitting circuit for emitting a light pulse signal;

the optical receiving circuit is used for receiving at least part of optical signals reflected by an object from the optical pulse signals emitted by the optical emitting circuit and converting the received laser signals into electric signals;

the sampling circuit is used for sampling the electric signal from the laser receiving circuit to obtain a sampling result;

and the arithmetic circuit is used for calculating the distance between the object and the distance measuring device according to the sampling result.

The present invention also provides a mobile platform, comprising:

the above-mentioned distance measuring device; and

the platform body, range unit's optical transmission circuit installs on the platform body.

Optionally, the mobile platform comprises at least one of an unmanned aerial vehicle, an automobile, and a robot.

According to the sampling circuit, the sampling method, the distance measuring device and the mobile platform, the time-to-digital conversion module and the analog-to-digital conversion module are arranged in parallel in the sampling circuit, sampling is performed in the two modes, more sampling points are obtained, the recovery degree of pulse shapes is better, and a better basis is provided for extraction of pulse information. In addition, the sampling circuit and the sampling method have the advantages of integrating the two types of sampling, and achieve the effect of complementary advantages. On one hand, multiple information such as energy, time and the like can be considered, for example, higher energy precision and the like can be obtained while time precision is ensured, and the advantages of the analog-to-digital conversion module on energy acquisition and the advantages of the time-to-digital conversion module on time acquisition are exerted; on the other hand, the requirements on the pulse shape can be widened, for example, low-amplitude wide pulses which cannot be processed by the time-to-digital conversion module can be processed by the analog-to-digital conversion module, and narrow pulses which cannot be processed by the analog-to-digital conversion module can be processed by the time-to-digital conversion module. The pulse with proper amplitude and pulse width can obtain better effect than any scheme of the analog-digital conversion module and the time-digital conversion module. For the pulse, the analog-to-digital conversion module and the time-to-digital conversion module can contribute more sampling points, and the accuracy of pulse information extraction can be improved by comprehensively using the analog-to-digital conversion module and the time-to-digital conversion module.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a sampling signal obtained by a time-to-digital conversion method according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a sampling signal obtained by an analog-to-digital conversion method according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a sampling circuit according to an embodiment of the present invention;

FIG. 4 is a schematic frame diagram of a distance measuring device provided by an embodiment of the present invention;

fig. 5 is a schematic diagram of an embodiment of a distance measuring device using a coaxial optical path according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In laser ranging related products such as laser radar, it is generally necessary to extract various pulse information such as energy, arrival Time, shape parameters, etc., and at present, two methods of digitizing optical pulses mainly include a Time-to-Digital Converter (for example, using a Time-to-Digital Converter (TDC)) and an Analog-to-Digital Converter (for example, using an Analog-to-Digital Converter (ADC)).

However, the TDC and the ADC have merits and disadvantages, and it is generally difficult to obtain the extraction accuracy of a plurality of kinds of information at the same time. The TDC can only realize parallel acquisition of N channels, and then can only acquire N +1 amplitude values at most, and the sampling precision and discrimination of the TDC in terms of voltage amplitude are low, especially the amplitude sampling of pulse signals is missing. In addition, near the baseline, due to the influence of baseline noise, the conventional TDC scheme cannot continuously measure for many times, and if the threshold is too low, once the TDC is triggered by the noise and meets the real pulse signal, the TDC cannot respond to the real pulse signal.

Whereas for ADCs the sampling rate is very high (or the sampling interval is very small). Available ADC sampling rates are typically of the GHz order, i.e. taking a point every 1 ns. In the pulse signal of about 10ns, only about 10 points can be collected, and the pulse information acquisition is not enough. In addition, the sampling time of the ADC is random with respect to the pulse signal, that is, the positions of sampling points of pulses arriving at different times with respect to the arrival time are not fixed, and in practical applications, accurate measurement distance can be obtained only by acquiring accurate pulse time information, and the sampling precision is slightly poor with respect to a sampling mode in which the pulse time is random.

In particular, on the faster edge of the pulse signal, the number of the acquisition points of the ADC is limited, the faster the edge of the pulse signal, the fewer the acquisition points, and the worse the recovery of the pulse signal, and in the TDC scheme, the points that can be triggered can be acquired no matter how fast the edge of the signal is.

In laser ranging application, pulse signals received by a detector are different along with different distances, reflectivity, diffuse reflection paths and the like of a measured object, and the amplitude and the pulse width of light pulses are changed to different degrees, so that a digital circuit and a processing method need to adapt to the pulse signals with different pulse widths and different amplitudes which change in a large range, and higher requirements are provided for the current TDC scheme or ADC scheme.

In order to solve the above problems, the present invention provides a sampling circuit, in which a time-to-digital conversion module and an analog-to-digital conversion module are arranged in parallel in the sampling circuit, and the sampling mode is arranged in parallel in the sampling circuit, so that the advantages of the two sampling methods are complemented to obtain the parameter value of the optical pulse signal. Wherein the parameter values include, but are not limited to, the following information: pulse arrival time, pulse width, pulse energy and amplitude, etc.

As shown in fig. 3, in an embodiment of the present invention, two sampling manners of ADC and TDC are combined, including an ADC module of a single channel and a TDC module of N channels. The ADC module has a sampling rate of f and quantization digits of M bits; the TDC of each channel comprises a comparator, and each channel sets different thresholds according to requirements to obtain the rising edge time and the falling edge time of the pulse under different amplitudes.

In the time-to-digital conversion module, a multi-channel design is usually adopted, each channel is provided with different amplitude thresholds, and the rising edge time and the falling edge time of the pulse under corresponding values are intercepted. TDC is a given threshold acquisition time, and sampling of TDC is triggered only when a pulse arrives and reaches a threshold, enabling high precision time measurements on the order of picoseconds.

As shown in fig. 1, the time-to-digital conversion module includes a plurality of channels, for example, 1 to N channels, where N is a natural number greater than 2. And the preset thresholds of the comparators in the different channels are different, for example, setting the threshold 1 to the threshold N.

Each channel comprises a comparator and a time-to-digital converter (TDC), wherein a first input end of the comparator in each channel is used for receiving an electric signal converted from an optical pulse signal, a second input end of the comparator is used for receiving a preset threshold value of the comparator, an output end of the comparator is used for outputting a comparison operation result, and the TDC is electrically connected with an output end of the comparator and is used for extracting time information corresponding to the electric signal according to the comparison operation result output by the comparator

In an example of the present invention, as shown in fig. 1, the preset thresholds set in different channels are respectively a threshold 1, a threshold 2, and up to a threshold N, the electrical signal input to the first input terminal of the comparator includes an electrical pulse signal, and when the preset threshold is the threshold 1 and the intensity of the electrical pulse signal exceeds the threshold 1, the electrical pulse signal triggers the comparator to output a high level signal, so as to obtain time information corresponding to triggering the threshold 1.

As shown in fig. 1, the principle of the time extraction method provided by the embodiment of the present invention is as follows: the electrical signal input to the comparator is compared with the threshold N to obtain a first square wave signal as shown by a dotted line, and the time TN of the transition edge of the first square wave signal can be considered as the time when the electrical signal passes through the comparator. Similarly, the electrical signal input to the comparing circuit is compared with the preset threshold 1 to obtain a second square wave signal as shown by a dotted line, and the time T1 of the transition edge of the second square wave signal can be considered as the time when the electrical signal passes through the comparator. The other channels acquire the time signals in the same way.

The TDC scheme has high time resolution (tens of ps), and particularly has enough advantages in faster pulse signal edge acquisition, thereby contributing more to accurate acquisition of pulse signal time. Therefore, when the pulse height and the pulse width are moderate, and the two kinds of sampling are more, the TDC scheme can be adopted for obtaining higher-precision information such as arrival time and pulse width information.

Among them, the ADC method has advantages of higher voltage acquisition accuracy, and more contribution in amplitude and energy of the pulse. The sampling method of the ADC module is shown in fig. 2, where the sampling clock frequency is f, and there is one amplitude sampling value every interval t is 1/f. If the sampling rate is high enough, the digital signal of the ADC can restore the time course of the amplitude of the optical pulse signal. If the amplitude information is quantized into M bits, the energy precision can reach 1/2M, and the amplitude information of the optical pulse can be accurately measured. In one example of the invention, the ADC sampling rate is on the order of 1-10GHz, e.g., one point every 1 ns.

Illustratively, sampling is performed at a time point t to obtain a first amplitude signal, sampling is performed at a time point 2t to obtain second amplitude information, and so on, sampling is performed at a time point Kt to obtain a kth amplitude signal, so as to obtain an amplitude of the electrical signal corresponding to the acquisition time.

In the embodiment of the invention, the two adoption modes are integrated, so that the method has enough advantages in the rapid pulse signal edge acquisition, can also ensure higher voltage acquisition precision, and has better acquisition capability in the aspects of pulse amplitude and energy.

As shown in fig. 3, in an example of the present invention, an ADC module and an N-channel TDC module operate in parallel to generate digital sampling data of a1, B1, B2, and … BN respectively, and transmit the digital sampling data to a control module for processing, where the control module is configured to select and calculate signals acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module to obtain parameter values of the optical pulse signal.

Optionally, in an example of the present invention, the control module uses a Microprogram Control Unit (MCU) to process data.

Optionally, the method for selecting the signal acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module by the control module may include any one of the following schemes or a combination of at least two of the following schemes:

first, the classification is selected, making full use of the advantages of each module when processing. Such as:

1. and when the width of the optical pulse signal is smaller than the pulse width set value, extracting pulse information by using a TDC scheme, and extracting the signal acquired by the time-to-digital conversion module. The pulse width setting value is used for representing the extent to which the width of the optical pulse signal can be extracted by using a TDC scheme, and the specific value can be selected according to actual needs and is not limited to a certain value range. By adopting the TDC method, the condition that ADC sampling is insufficient due to small pulse width can be avoided.

2. When the pulse height of the optical pulse signal is smaller than a pulse height set value, extracting pulse information by using an ADC scheme, where the pulse height set value is used to represent the degree to which the height of the optical pulse signal can be extracted by using the ADC scheme, and a specific value of the pulse height set value may be selected according to actual needs, and is not limited to a certain range of values. By adopting the ADC method, the condition that TDC sampling is insufficient due to too small pulse height can be avoided.

3. When the width of the optical pulse signal is greater than the pulse width set value and the pulse height of the optical pulse signal is greater than the pulse height set value, at least one of the ADC method and the TDC method may be selected, or both schemes may be used for sampling. When two kinds of sampling with moderate pulse height and width are more, the TDC scheme is adopted for obtaining higher-precision information by the TDC scheme such as arrival time and pulse width information, and the ADC scheme is adopted for obtaining higher-precision information by the ADC scheme such as pulse energy/amplitude.

Certainly, the selection may also be performed according to the required parameters and precision of the optical pulse signal, for example, if the precision required for the arrival time and the pulse width information of the optical pulse signal is higher, at least the signal acquired by the time-to-digital conversion module is selected; and at least selecting the signal acquired by the analog-to-digital conversion module if the pulse energy and amplitude information of the optical pulse signal requires higher precision. Of course, two signals obtained by the modules can be simultaneously selected.

After acquiring the signals acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module, the control module is configured to calculate the selected signals, and the calculation method includes any one of the following schemes or a combination of the two schemes:

and I, calculating the selected signal in a fitting mode, wherein the fitting mode is to label the corresponding position of the acquired pulse signal in the graph of the optical pulse signal so as to restore the pulse graph of the optical pulse signal, and after the pulse graph of the pulse signal is obtained, required information such as at least one of pulse arrival time, pulse width, pulse energy and amplitude can be further read on the pulse graph.

And II, the control module calculates the selected signal in an explicit statistic manner, and correspondingly calculates each selected sampling point in the calculation method to obtain a parameter value of the optical pulse signal corresponding to each sampling point so as to obtain a plurality of point values.

It should be noted that the above two methods of calculating the selected signal by the control module are also applicable to any combination of the following two processing methods or other processing methods, and the fitting process and the explicit statistic method are explained with reference to the above explanation without specific description.

And secondly, processing in a direct depth fusion mode. In the method, sampling points of two types of sampling modules are fitted together to obtain a pulse pattern of a pulse signal. Of course, certain sampling points may be extracted to perform fitting, for example, the sampling points on the rising edge are all selected to perform fitting. And extracting the pulse arrival time, the pulse width, the pulse energy and the like according to the fitting result. Together, the two types of sampling can provide more sampling points than either way, so that the accuracy of fitting can be improved, and the extraction accuracy of pulse information can be improved.

Thirdly, the depth fusion is performed after the conversion, wherein the conversion refers to the conversion of one of the adopted results into another mode, and then the processing is performed, and the method specifically comprises the following steps:

1. and converting the sampling result of the ADC into sampling in a TDC mode, or/and converting the sampling result of the TDC into sampling in the ADC mode. Then the converted result and another sampling point are put together, and the pulse information is extracted in a certain mode uniformly. Such as at least one of a fitting process and a manner of explicit statistics.

In an example of the present invention, if the ADC samples are converted into TDC-mode samples, a method of a TDC scheme is adopted for information extraction; otherwise, if the TDC sampling is converted into the sampling in the ADC mode, the information is extracted by using the method of the ADC scheme. The statistics used in the extraction should include two types of samples: TDC sampling + sampling from ADC conversion, or ADC sampling + sampling from TDC conversion.

2. For the conversion between ADC and TDC sampling, a first fitting/interpolation and then sampling may be used. In an example of the present invention, for example, fitting is performed on the ADC samples first to obtain a graph of the optical pulse signal, and then threshold is given to acquire time in a manner simulating the TDC.

The invention provides a sampling circuit, wherein a time digital conversion module and an analog-digital conversion module are arranged in parallel in the sampling circuit, sampling is carried out in the two modes, more sampling points are obtained, the recovery degree of pulse shapes is better, and a better basis is provided for extracting pulse information. In addition, the sampling circuit and the sampling method have the advantages of integrating the two types of sampling, and achieve the effect of complementary advantages. On one hand, multiple information such as energy, time and the like can be considered, for example, higher energy precision and the like can be obtained while time precision is ensured, and the advantages of the analog-to-digital conversion module on energy acquisition and the advantages of the time-to-digital conversion module on time acquisition are exerted; on the other hand, the requirements on the pulse shape can be widened, for example, low-amplitude wide pulses which cannot be processed by the time-to-digital conversion module can be processed by the analog-to-digital conversion module, and narrow pulses which cannot be processed by the analog-to-digital conversion module can be processed by the time-to-digital conversion module. The pulse with proper amplitude and pulse width can obtain better effect than any scheme of the analog-digital conversion module and the time-digital conversion module. For the pulse, the analog-to-digital conversion module and the time-to-digital conversion module can contribute more sampling points, and the accuracy of pulse information extraction can be improved by comprehensively using the analog-to-digital conversion module and the time-to-digital conversion module.

In another embodiment of the present invention, a sampling method based on a sampling circuit is provided, including:

The sampling mode is parallelly arranged in the adopted circuit by arranging the time digital conversion module and the analog-to-digital conversion module in parallel in the adopted circuit, so that the advantages of the two adopted methods are complemented to obtain the parameter value of the optical pulse signal. Wherein the parameter values include, but are not limited to, the following information: pulse arrival time, pulse width, pulse energy and amplitude, etc.

As shown in fig. 3, in an embodiment of the present invention, two sampling modes, i.e., ADC and TDC, are combined. The ADC sampling method is characterized in that the sampling rate is f, and the quantization digit is M bits; the TDC of each channel comprises a comparator, and each channel sets different thresholds according to requirements to obtain the rising edge time and the falling edge time of the pulse under different amplitudes.

Wherein each of said channels comprises a comparator and a time-to-digital converter TDC. In an example of the present invention, as shown in fig. 1, the preset thresholds set in different channels are respectively a threshold 1, a threshold 2, and up to a threshold N, the electrical signal input to the first input terminal of the comparator includes an electrical pulse signal, and when the preset threshold is the threshold 1 and the intensity of the electrical pulse signal exceeds the threshold 1, the electrical pulse signal triggers the comparator to output a high level signal, so as to obtain time information corresponding to triggering the threshold 1.

It should be noted that the above two methods of calculating the selected signal by the control module are also applicable to the following two processing methods or any combination of the other processing methods, and the fitting process and the explicit statistic method are explained with reference to the above explanation without specific description.

The sampling circuit provided by each embodiment of the invention can be applied to a distance measuring device, and the distance measuring device can be electronic equipment such as a laser radar, laser distance measuring equipment and the like. In one embodiment, the ranging device is used to sense external environmental information, such as distance information, orientation information, reflected intensity information, velocity information, etc. of environmental targets. In one implementation, the ranging device may detect the distance of the probe to the ranging device by measuring the Time of Flight (TOF), which is the Time-of-Flight Time, of light traveling between the ranging device and the probe. Alternatively, the distance measuring device may detect the distance from the probe to the distance measuring device by other techniques, such as a distance measuring method based on phase shift (phase shift) measurement or a distance measuring method based on frequency shift (frequency shift) measurement, which is not limited herein.

For ease of understanding, the following describes an example of the ranging operation with reference to the ranging apparatus 100 shown in fig. 4.

As shown in fig. 4, the ranging apparatus 100 may include a transmitting circuit 110, a receiving circuit 120, a sampling circuit 130, and an operation circuit 140.

The transmit circuitry 110 may transmit a sequence of light pulses (e.g., a sequence of laser pulses). The receiving circuit 120 may receive the optical pulse train reflected by the detected object, perform photoelectric conversion on the optical pulse train to obtain an electrical signal, process the electrical signal, and output the electrical signal to the sampling circuit 130. The sampling circuit 130 may sample the electrical signal to obtain a sampling result. The arithmetic circuit 140 may determine the distance between the distance measuring device 100 and the detected object based on the sampling result of the sampling circuit 130.

Optionally, the distance measuring apparatus 100 may further include a control circuit 150, and the control circuit 150 may implement control of other circuits, for example, may control an operating time of each circuit and/or perform parameter setting on each circuit, and the like.

It should be understood that, although the distance measuring device shown in fig. 4 includes a transmitting circuit, a receiving circuit, a sampling circuit and an arithmetic circuit for emitting a light beam to detect, the embodiments of the present application are not limited thereto, and the number of any one of the transmitting circuit, the receiving circuit, the sampling circuit and the arithmetic circuit may be at least two, and the at least two light beams are emitted in the same direction or in different directions respectively; the at least two light paths may be emitted simultaneously or at different times. In one example, the light emitting chips in the at least two transmitting circuits are packaged in the same module. For example, each transmitting circuit comprises a laser emitting chip, and die of the laser emitting chips in the at least two transmitting circuits are packaged together and accommodated in the same packaging space.

In some implementations, in addition to the circuit shown in fig. 4, the distance measuring apparatus 100 may further include a scanning module for changing the propagation direction of at least one laser pulse sequence emitted from the emitting circuit.

Here, a module including the transmission circuit 110, the reception circuit 120, the sampling circuit 130, and the operation circuit 140, or a module including the transmission circuit 110, the reception circuit 120, the sampling circuit 130, the operation circuit 140, and the control circuit 150 may be referred to as a ranging module, which may be independent of other modules, for example, a scanning module.

The distance measuring device can adopt a coaxial light path, namely the light beam emitted by the distance measuring device and the reflected light beam share at least part of the light path in the distance measuring device. For example, at least one path of laser pulse sequence emitted by the emitting circuit is emitted by the scanning module after the propagation direction is changed, and the laser pulse sequence reflected by the detector is emitted to the receiving circuit after passing through the scanning module. Alternatively, the distance measuring device may also adopt an off-axis optical path, that is, the light beam emitted by the distance measuring device and the reflected light beam are transmitted along different optical paths in the distance measuring device. FIG. 5 shows a schematic diagram of one embodiment of the ranging device of the present invention using coaxial optical paths.

The ranging apparatus 200 comprises a ranging module 210, the ranging module 210 comprising an emitter 203 (which may comprise the transmitting circuitry described above), a collimating element 204, a detector 205 (which may comprise the receiving circuitry, sampling circuitry and arithmetic circuitry described above) and a path-altering element 206. The distance measuring module 210 is configured to emit a light beam, receive return light, and convert the return light into an electrical signal. Wherein the emitter 203 may be configured to emit a sequence of light pulses. In one embodiment, the transmitter 203 may emit a sequence of laser pulses. Optionally, the laser beam emitted by the emitter 203 is a narrow bandwidth beam having a wavelength outside the visible range. The collimating element 204 is disposed on an emitting light path of the emitter, and is configured to collimate the light beam emitted from the emitter 203, and collimate the light beam emitted from the emitter 203 into parallel light to be emitted to the scanning module. The collimating element is also for converging at least a portion of the return light reflected by the detector. The collimating element 204 may be a collimating lens or other element capable of collimating a light beam.

In the embodiment shown in fig. 5, the transmit and receive optical paths within the distance measuring device are combined by the optical path altering element 206 before the collimating element 204, so that the transmit and receive optical paths may share the same collimating element, making the optical path more compact. In other implementations, the emitter 203 and the detector 205 may use respective collimating elements, and the optical path changing element 206 may be disposed in the optical path after the collimating elements.

In the embodiment shown in fig. 5, since the beam aperture of the light beam emitted from the emitter 203 is small and the beam aperture of the return light received by the distance measuring device is large, the optical path changing element can adopt a small-area mirror to combine the emission optical path and the reception optical path. In other implementations, the optical path changing element may also be a mirror with a through hole, wherein the through hole is used for transmitting the outgoing light from the emitter 203, and the mirror is used for reflecting the return light to the detector 205. Therefore, the shielding of the bracket of the small reflector to the return light can be reduced in the case of adopting the small reflector.

In the embodiment shown in fig. 5, the optical path altering element is offset from the optical axis of the collimating element 204. In other implementations, the optical path altering element may also be located on the optical axis of the collimating element 204.

The ranging device 200 also includes a scanning module 202. The scanning module 202 is disposed on the emitting light path of the distance measuring module 210, and the scanning module 202 is configured to change the transmission direction of the collimated light beam 219 emitted by the collimating element 204, project the collimated light beam to the external environment, and project the return light beam to the collimating element 204. The return light is converged by the collimating element 204 onto the detector 205.

In one embodiment, the scanning module 202 may include at least one optical element for altering the propagation path of the light beam, wherein the optical element may alter the propagation path of the light beam by reflecting, refracting, diffracting, etc., the light beam. For example, the scanning module 202 includes a lens, mirror, prism, galvanometer, grating, liquid crystal, Optical Phased Array (Optical Phased Array), or any combination thereof. In one example, at least a portion of the optical element is moved, for example, by a driving module, and the moved optical element can reflect, refract, or diffract the light beam to different directions at different times. In some embodiments, multiple optical elements of the scanning module 202 may rotate or oscillate about a common axis 209, with each rotating or oscillating optical element serving to constantly change the direction of propagation of an incident beam. In one embodiment, the multiple optical elements of the scanning module 202 may rotate at different rotational speeds or oscillate at different speeds. In another embodiment, at least some of the optical elements of the scanning module 202 may rotate at substantially the same rotational speed. In some embodiments, the multiple optical elements of the scanning module may also be rotated about different axes. In some embodiments, the multiple optical elements of the scanning module may also rotate in the same direction, or in different directions; or in the same direction, or in different directions, without limitation.

In one embodiment, the scanning module 202 includes a first optical element 214 and a driver 216 coupled to the first optical element 214, the driver 216 configured to drive the first optical element 214 to rotate about the rotation axis 209, such that the first optical element 214 redirects the collimated light beam 219. The first optical element 214 projects the collimated beam 219 into different directions. In one embodiment, the angle between the direction of the collimated beam 219 after it is altered by the first optical element and the rotational axis 109 changes as the first optical element 214 is rotated. In one embodiment, the first optical element 214 includes a pair of opposing non-parallel surfaces through which the collimated light beam 219 passes. In one embodiment, the first optical element 214 includes a prism having a thickness that varies along at least one radial direction. In one embodiment, the first optical element 214 comprises a wedge angle prism that refracts the collimated beam 219.

In one embodiment, the scanning module 202 further comprises a second optical element 215, the second optical element 215 rotating around a rotation axis 209, the rotation speed of the second optical element 215 being different from the rotation speed of the first optical element 214. The second optical element 215 is used to change the direction of the light beam projected by the first optical element 214. In one embodiment, the second optical element 115 is coupled to another driver 217, and the driver 217 drives the second optical element 215 to rotate. The first optical element 214 and the second optical element 215 may be driven by the same or different drivers, such that the first optical element 214 and the second optical element 215 rotate at different speeds and/or turns, thereby projecting the collimated light beam 219 into different directions in the ambient space, which may scan a larger spatial range. In one embodiment, the controller 218 controls the

drivers

216 and 217 to drive the first optical element 214 and the second optical element 215, respectively. The rotation speed of the first optical element 214 and the second optical element 215 can be determined according to the region and the pattern expected to be scanned in the actual application. The

drives

216 and 217 may include motors or other drives.

In one embodiment, second optical element 215 includes a pair of opposing non-parallel surfaces through which the light beam passes. In one embodiment, second optical element 215 includes a prism having a thickness that varies along at least one radial direction. In one embodiment, second optical element 215 comprises a wedge angle prism.

In one embodiment, the scan module 202 further comprises a third optical element (not shown) and a driver for driving the third optical element to move. Optionally, the third optical element comprises a pair of opposed non-parallel surfaces through which the light beam passes. In one embodiment, the third optical element comprises a prism having a thickness that varies along at least one radial direction. In one embodiment, the third optical element comprises a wedge angle prism. At least two of the first, second and third optical elements rotate at different rotational speeds and/or rotational directions.

Rotation of the optical elements in the scanning module 202 may project light in different directions, such as the direction of the projected light 211 and the direction 213, thus scanning the space around the ranging device 200. When the light 211 projected by the scanning module 202 hits the detection object 201, a part of the light is reflected by the detection object 201 to the distance measuring device 200 in the opposite direction to the projected light 211. The return light 212 reflected by the object 201 passes through the scanning module 202 and then enters the collimating element 204.

The detector 205 is placed on the same side of the collimating element 204 as the emitter 203, and the detector 205 is used to convert at least part of the return light passing through the collimating element 204 into an electrical signal.

In one embodiment, each optical element is coated with an antireflection coating. Optionally, the thickness of the antireflection film is equal to or close to the wavelength of the light beam emitted by the emitter 203, which can increase the intensity of the transmitted light beam.

In one embodiment, a filter layer is coated on a surface of a component in the distance measuring device, which is located on the light beam propagation path, or a filter is arranged on the light beam propagation path, and is used for transmitting at least a wave band in which the light beam emitted by the emitter is located and reflecting other wave bands, so as to reduce noise brought to the receiver by ambient light.

In some embodiments, the transmitter 203 may include a laser diode through which laser pulses in the order of nanoseconds are emitted. Further, the laser pulse reception time may be determined, for example, by detecting the rising edge time and/or the falling edge time of the electrical signal pulse. In this manner, the ranging apparatus 200 may calculate TOF using the pulse reception time information and the pulse emission time information, thereby determining the distance of the probe 201 to the ranging apparatus 200.

The distance and orientation detected by ranging device 200 may be used for remote sensing, obstacle avoidance, mapping, modeling, navigation, and the like. In one embodiment, the distance measuring device of the embodiment of the invention can be applied to a mobile platform, and the distance measuring device can be installed on a platform body of the mobile platform. The mobile platform with the distance measuring device can measure the external environment, for example, the distance between the mobile platform and an obstacle is measured for the purpose of avoiding the obstacle, and the external environment is mapped in two dimensions or three dimensions. In certain embodiments, the mobile platform comprises at least one of an unmanned aerial vehicle, an automobile, a remote control car, a robot, a camera. When the distance measuring device is applied to the unmanned aerial vehicle, the platform body is a fuselage of the unmanned aerial vehicle. When the distance measuring device is applied to an automobile, the platform body is the automobile body of the automobile. The vehicle may be an autonomous vehicle or a semi-autonomous vehicle, without limitation. When the distance measuring device is applied to the remote control car, the platform body is the car body of the remote control car. When the distance measuring device is applied to a robot, the platform body is the robot. When the distance measuring device is applied to a camera, the platform body is the camera itself.

Technical terms used in the embodiments of the present invention are only used for illustrating specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the use of "including" and/or "comprising" in the specification is intended to specify the presence of stated features, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. The embodiments described herein are further intended to explain the principles of the invention and its practical application and to enable others skilled in the art to understand the invention.

The flow chart described in the present invention is only an example, and various modifications can be made to the diagram or the steps in the present invention without departing from the spirit of the present invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified. It will be understood by those skilled in the art that all or a portion of the above-described embodiments may be practiced and equivalents thereof may be resorted to as falling within the scope of the invention as claimed.

Claims

A sampling circuit, comprising: the sampling circuit comprises a time-to-digital conversion module, an analog-to-digital conversion module and a control module, wherein the time-to-digital conversion module and the analog-to-digital conversion module are arranged in parallel;

the time-to-digital conversion module is used for receiving an electric signal obtained by converting an optical pulse signal, comparing the electric signal with a preset threshold value, and acquiring time information corresponding to the electric signal;

the analog-to-digital conversion module is used for receiving the electric signal obtained by converting the optical pulse signal and acquiring the amplitude of the electric signal corresponding to the acquisition time in the sampling clock frequency;

and the control module is used for selecting and calculating the signals acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module to obtain the parameter values of the optical pulse signals.
The sampling circuit according to claim 1, wherein the time-to-digital conversion module includes a plurality of channels, each of the channels includes a comparator and a time-to-digital converter, wherein a first input terminal of the comparator is configured to receive an electrical signal converted from the optical pulse signal, a second input terminal of the comparator is configured to receive a preset threshold of the comparator, an output terminal of the comparator is configured to output a result of the comparison operation, and the time-to-digital converter is electrically connected to the output terminal of the comparator and is configured to extract time information corresponding to the electrical signal according to the result of the comparison operation output by the comparator;

and the preset thresholds of the comparators in the different channels are different.
The sampling circuit of claim 1, wherein the analog-to-digital conversion module comprises at least one analog-to-digital converter for acquiring an amplitude of the electrical signal corresponding to the acquisition time.
The sampling circuit of claim 1, wherein the control module is configured to calculate the selected signal by fitting to restore a pattern of the optical pulse signal;

or the control module is used for calculating the selected signal in an explicit statistic manner to obtain a parameter value of the optical pulse signal.
The sampling circuit of claim 4, wherein the control module collects at least a portion of the signals of the time-to-digital conversion module and at least a portion of the signals collected by the analog-to-digital conversion module for the fitting.
The sampling circuit of claim 1, wherein the control module is further configured to convert the samples from the time-to-digital conversion module into the samples from the analog-to-digital conversion module;

or the control module is also used for converting the sampling of the analog-to-digital conversion module into the sampling of the time-to-digital conversion module.
The sampling circuit of claim 6, wherein the control module is configured to calculate the sampled signal of the analog-to-digital conversion module by using a fitting method to obtain a graph of the optical pulse signal, and then calibrate a preset threshold and corresponding time information on the graph of the optical pulse signal.
The sampling circuit of claim 1, wherein the control module, when selecting the signal:

when the width of the optical pulse signal is smaller than a pulse width set value, selecting a signal acquired by the time-to-digital conversion module; and/or

When the pulse height of the optical pulse signal is smaller than a pulse height set value, selecting a signal acquired by the analog-to-digital conversion module; and/or

When the width of the optical pulse signal is greater than a pulse width set value and the pulse height of the optical pulse signal is greater than a pulse height set value, if the accuracy required by the arrival time and the pulse width information of the optical pulse signal is higher, at least selecting a signal acquired by the time-to-digital conversion module; and at least selecting the signal acquired by the analog-to-digital conversion module if the pulse energy and amplitude information of the optical pulse signal requires higher precision.
The sampling circuit of claim 1, wherein the parameter value comprises at least one of a pulse arrival time, a pulse width, a pulse energy, and an amplitude.
A sampling method based on a sampling circuit, comprising:

receiving an electric signal obtained by converting the optical pulse signal through a time-to-digital conversion module, comparing the electric signal with a preset threshold value, and acquiring time information corresponding to the electric signal;

receiving an electric signal obtained by converting the optical pulse signal through an analog-to-digital conversion module, and acquiring an amplitude signal of the electric signal corresponding to acquisition time in sampling clock frequency;

and selecting and calculating the signals acquired by the time-to-digital conversion module and/or the analog-to-digital conversion module to obtain the parameter values of the optical pulse signals.
The sampling method of claim 10, wherein the time-to-digital conversion module comprises a plurality of channels that receive the electrical signals in parallel and compare the electrical signals to collect time information corresponding to the electrical signals.
The sampling method according to claim 11, characterized in that said plurality of channels are respectively provided with different preset thresholds to receive in parallel said electrical signals and to perform a comparison operation on said electrical signals.
The sampling method of claim 10, wherein the step of selecting a signal and calculating to obtain a parameter value of the optical pulse signal comprises:

calculating the selected signal in a fitting mode to restore the graph of the optical pulse signal;

or calculating the selected signal by adopting an explicit statistic method to obtain a parameter value of the optical pulse signal.
The sampling method according to claim 13, wherein at least a portion of the signals from the time-to-digital conversion module and a portion of the signals from the analog-to-digital conversion module are selected for the fitting.
The sampling method of claim 10, wherein after selecting the signals collected by the time-to-digital conversion module and the analog-to-digital conversion module, and before performing the calculation, the method further comprises:

converting the sampling of the time-to-digital conversion module into the sampling of the analog-to-digital conversion module;

or the control module is also used for converting the sampling of the analog-to-digital conversion module into the sampling of the time-to-digital conversion module.
The sampling method according to claim 15, wherein a fitting manner is adopted to calculate the sampled signal of the analog-to-digital conversion module to obtain a graph of the optical pulse signal, and then a preset threshold and corresponding time information are calibrated on a graph structure of the optical pulse signal.
The sampling method of claim 10, wherein, when selecting the signal,

when the width of the optical pulse signal is smaller than a pulse width set value, selecting a signal acquired by the time-to-digital conversion module; and/or

When the pulse height of the optical pulse signal is smaller than a pulse height set value, selecting a signal acquired by the analog-to-digital conversion module; and/or

When the width of the optical pulse signal is greater than a pulse width set value and the pulse height of the optical pulse signal is greater than a pulse height set value, if the accuracy required by the arrival time and the pulse width information of the optical pulse signal is higher, at least selecting a signal acquired by the time-to-digital conversion module; and if the precision required by the pulse energy and amplitude information of the optical pulse signal is higher, at least selecting the signal acquired by the analog-to-digital conversion module.
The sampling method of claim 10, wherein the parameter value comprises at least one of a pulse arrival time, a pulse width, a pulse energy, and a pulse amplitude.
A ranging apparatus, comprising:

a light emitting circuit for emitting a light pulse signal;

the optical receiving circuit is used for receiving at least part of optical signals reflected by an object from the optical pulse signals emitted by the optical emitting circuit and converting the received laser signals into electric signals;

the sampling circuit according to any one of claims 1 to 9, for sampling the electrical signal from the laser receiving circuit to obtain a sampling result;

and the arithmetic circuit is used for calculating the distance between the object and the distance measuring device according to the sampling result.
A mobile platform, comprising:

a ranging apparatus as claimed in claim 19; and

the platform body, range unit's optical transmission circuit installs on the platform body.
The mobile platform of claim 20, wherein the mobile platform comprises at least one of an unmanned aerial vehicle, an automobile, and a robot.