Method and device for expanding frequency-modulated continuous wave ranging range

Abstract

The present invention describes a method and device for expanding a frequency-modulated continuous wave ranging range. A ranging device comprises a delay network used for dividing the ranging range into a plurality of distance intervals, and the delay network comprises a plurality of preset delay parameters matched with the plurality of distance intervals. The method for expanding the ranging range comprises: outputting measurement light to a target and obtaining return light formed by scattering the measurement light by the target; inputting reference light into a delay network, so that the delay network outputs at least one path of delay reference light, wherein the delay reference light has a preset delay parameter matched with the reference light; obtaining at least one interference signal on the basis of the at least one path of delay reference light and the return light, wherein the at least one interference signal is matched with the distance interval where the target is located; and obtaining the distance of the target on the basis of the distance interval and the at least one interference signal. Therefore, an intermediate frequency of the interference signal can be reduced while the ranging range is expanded, thereby improving the ranging resolution.

Description

Method and device for extending frequency modulated continuous wave ranging range Technical Field

[0001] The present invention relates to the field of laser measurement technology, and in particular to a method and device for extending a frequency modulated continuous wave ranging range. Background Art

[0002] In laser ranging, distance measurement based on linear frequency-modulated continuous wave (LFMCW) is a common technique. Specifically, an LFMCW-based ranging device transmits light with a linearly varying frequency (i.e., linear frequency-modulated continuous wave) toward the object being measured (also known as the target) within a frequency modulation period. The target scatters the emitted light to form return light, which interferes with the emitted light to produce an interference signal that carries the target's distance information. The corresponding interference signal is a time-varying sine and cosine signal that varies at a fixed frequency (also referred to as the intermediate frequency). By measuring the intermediate frequency of the interference signal, the measured distance between the target and the ranging device can be obtained, and the intermediate frequency is proportional to the measured distance.

[0003] In existing technologies, when measuring distances, the intermediate frequency of the interference signal also increases, requiring the design of processing circuits with higher sampling rates. This higher sampling rate often increases the complexity of circuit design, requiring, for example, improved electromagnetic compatibility, larger storage capacity, higher data transmission bandwidth, and stricter timing analysis, thereby reducing the reliability of the processing circuits.

[0004] Furthermore, according to prior art, the measured distance is also limited by the frequency modulation period. To achieve a larger measurement distance, another prior art approach extends the ranging range of the ranging system by reducing the frequency modulation bandwidth of the emitted light and increasing the frequency modulation period. Although this prior art reduces the intermediate frequency of the interference signal, it suffers from low ranging resolution.

[0005] Summary of the Invention

[0006] The present invention has been developed in view of the above-mentioned state of the prior art, and its purpose is to provide a method and apparatus for extending the range of frequency modulated continuous wave ranging, which can reduce the intermediate frequency of the interference signal while expanding the ranging range, thereby simplifying the design of the processing circuit and improving the reliability of the circuit. At the same time, it can reduce the limitations of the frequency modulation bandwidth and frequency modulation period on the measurement distance range, thereby improving the resolution of the ranging.

[0007] To this end, a first aspect of the present invention provides a method for extending the range of frequency modulated continuous wave ranging, which is a method for measuring the distance of a target using a ranging device, the ranging device including a delay network for dividing the ranging range of the ranging device into multiple distance intervals, the delay network including multiple preset delay parameters matching the multiple distance intervals. The method for extending the range of frequency modulated continuous wave ranging includes: outputting measuring light to the target and obtaining return light formed by scattering the measuring light by the target; inputting reference light into the delay network so that the delay network outputs at least one delayed reference light, the delayed reference light having the preset delay parameters matching the reference light; obtaining at least one interference signal based on the at least one delayed reference light and the return light, the at least one interference signal matching the distance interval in which the target is located; and obtaining the distance of the target based on the distance interval and the at least one interference signal.

[0008] In a first aspect of the present invention, a method for extending the range of frequency modulated continuous wave (FMCW) ranging is provided. By outputting measurement light to a target and obtaining return light, reference light is input into a delay network to obtain at least one delayed reference light beam. Compared to the reference light beam before inputting the delay network, the delayed reference light beam has a predetermined delay parameter that matches the reference light beam and is known. In other words, the delay network acts to maintain the position of the target while indirectly moving the ranging device a known distance closer to the target. This reduces the frequency difference between the reference light beam and the return light beam. Specifically, the intermediate frequency of the interference signal generated by the delayed reference light beam and the return light beam is correspondingly reduced compared to the interference signal generated by the interference between the reference light beam and the return light beam. Furthermore, in the method for extending the range of the first aspect of the present invention, the ranging range is divided into multiple distance intervals by determining whether the return light beam and the at least one delayed reference light beam interfere to generate an interference signal. Thus, when measuring the distance to a target, the distance interval in which the target distance falls can be determined, thereby facilitating the selection of the matching interference signal to calculate the target distance. Therefore, the method for extending the ranging range provided by the first aspect of the present invention can reduce the sampling rate of the processing circuit of the ranging device and the complexity of the related circuit design, thereby being able to overcome the limitations of the interference signal's intermediate frequency, frequency modulation bandwidth, and frequency modulation period on the ranging range, thereby being able to extend the ranging range of the ranging device. Moreover, since the ranging range is divided into multiple small distance intervals, it is possible to increase the ranging resolution by increasing the frequency modulation bandwidth within each distance interval.

[0009] Furthermore, according to the method for extending the range of frequency modulated continuous wave ranging according to the first aspect of the present invention, the delay network optionally includes multiple delay paths, each delay path having a preset delay parameter corresponding to each of the distance intervals. In this case, a delayed reference light with an appropriate preset delay parameter can be selected to interfere with the return light according to the target distance. For example, when the target distance is short, a delayed reference light with a smaller preset delay parameter can be selected to interfere with the return light, while when the target distance is long, a delayed reference light with a larger preset delay parameter can be selected to interfere with the return light. This helps overcome the limitations of the interference signal's intermediate frequency, frequency modulation bandwidth, and frequency modulation period on the ranging range, thereby extending the ranging range of the ranging device. Furthermore, since the ranging range is divided into multiple small distance intervals, the ranging resolution can be increased within each distance interval by increasing the frequency modulation bandwidth.

[0010] Furthermore, the method for extending the FMCW ranging range according to the first aspect of the present invention optionally includes obtaining, based on the at least one interference signal, a combined code indicating whether the delayed reference light output by the delay network interferes with the return light, and obtaining the distance interval within which the target is located based on the combined code. In this case, when measuring the distance to the target, the ranging device can determine the distance interval within which the target's distance falls by obtaining the combined code. The combined code facilitates the implementation of the method for extending the ranging range through digital processing.

[0011] In addition, according to the method for extending the range of frequency modulated continuous wave ranging involved in the first aspect of the present invention, optionally, the delay network includes multiple delay paths, and the method for extending the range of frequency modulated continuous wave ranging includes dividing the multiple delay paths into at least two types of range paths based on the multiple distance intervals, the range paths matching the at least one distance interval; obtaining the range path matching the distance interval in which the target is located based on the at least one interference signal; obtaining a combination code matching the range path based on the at least one interference signal and the range path; and obtaining the distance interval in which the target is located based on the combination code matching the range path. In this case, when measuring the distance to the target, the range and corresponding range path of the target distance can be preliminarily determined based on the interference signal, and the delay path to be used can be determined based on the range, thereby reducing the workload of interference signal detection and reducing the number of bits of the combination code, thereby improving the efficiency of ranging.

[0012] In addition, the method for expanding the FMCW ranging range according to the first aspect of the present invention optionally includes obtaining, based on the distance interval, a preset delay parameter that matches a preset condition as a target delay parameter, wherein the preset condition is that the interference signal is not less than a preset threshold; and obtaining the target distance based on the target delay parameter, the at least one interference signal, and the system parameters of the measurement light. In this case, once the distance interval within which the target distance falls is determined, the interference signal that meets the preset condition can be selected to calculate the target distance, thereby improving ranging accuracy.

[0013] Furthermore, according to the method for extending the FMCW ranging range involved in the first aspect of the present invention, the preset delay parameters are optionally configured so that at least one of the relationship curves corresponding to the distance intervals has a monotonic interval, and the types and combinations of the interference signals involved in different distance intervals are different. This facilitates the division of distance intervals and simplifies the calculation process of the measured distance.

[0014] A second aspect of the present invention provides a device for extending the range of frequency modulated continuous wave ranging, which is a device for measuring the distance of a target, comprising: a generating module, a delay network for dividing the ranging range of the device into multiple distance intervals, a coupling module, and a processing module, wherein the delay network includes multiple preset delay parameters matching the multiple distance intervals; the light wave emitted by the generating module includes measurement light and reference light, the measurement light is output to the target, and the device obtains return light formed by the measurement light scattered by the target; the reference light is input to the delay network, and the delay network outputs at least one delayed reference light, the delayed reference light having the preset delay parameters matching the reference light; the at least one delayed reference light is transmitted to the coupling module respectively with the return light, the coupling module outputs at least one interference signal to the processing module, the at least one interference signal matching the distance interval in which the target is located; the processing module obtains the distance of the target based on the distance interval and the at least one interference signal.

[0015] In the device provided in the second aspect of the present invention, by providing a delay network and dividing the ranging range into multiple distance intervals based on the interference signal, the sampling rate of the processing circuit and the complexity of the related circuit design can be reduced, thereby being able to overcome the limitations of the interference signal's intermediate frequency, frequency modulation bandwidth, and frequency modulation period on the ranging range, thereby expanding the ranging range of the ranging device. Moreover, since the ranging range is divided into multiple small distance intervals, it is possible to increase the ranging resolution by increasing the frequency modulation bandwidth within each distance interval.

[0016] In addition, according to the device involved in the second aspect of the present invention, optionally, the delay network includes multiple delay paths, and the device includes a range optical switch that divides the multiple delay paths into at least two types of range paths based on the multiple distance intervals. The range optical switch includes an input end and multiple output ends corresponding to different range paths. The output end of the range optical switch is connected to the matching delay path, and the reference light is input into the delay network via the range optical switch. In this case, when measuring the distance to the target, the delay path corresponding to the range can be obtained by controlling the range optical switch, thereby reducing the workload of interference signal detection and improving the efficiency of distance measurement.

[0017] Furthermore, according to the apparatus of the second aspect of the present invention, optionally, if the processing module does not receive the at least one interference signal, the processing module controls the range optical switch to switch the range path. In this case, when measuring the distance to a target, if the processing module does not receive the interference signal, it determines that the target distance is not within the range defined by the delay path connected to the output end of the current range optical switch. The processing module can then switch the range optical switch to another range path, thereby enabling switching between different range paths.

[0018] Furthermore, according to the apparatus of the second aspect of the present invention, the delay network optionally includes multiple delay paths, which are arranged in parallel or in series. In this case, when the delay paths are arranged in parallel, the delay network structure is simple, which facilitates the individual design of each delay path. Furthermore, by arranging the delay paths in parallel, a failure in one delay path does not affect other delay paths, which also facilitates maintenance. When the delay paths are arranged in series, the number of components in the distance measuring device can be reduced, thereby facilitating portability and miniaturization of the distance measuring device.

[0019] According to the present invention, a method and apparatus for extending the range of frequency modulated continuous wave ranging can be provided. The method and apparatus can reduce the intermediate frequency of the interference signal while extending the ranging range, thereby simplifying the design of the processing circuit and improving the reliability of the circuit. Furthermore, the method can reduce the limitations of the frequency modulation bandwidth and frequency modulation period on the measurement distance range, thereby improving the resolution of the ranging. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention will now be explained in further detail, by way of example only, with reference to the accompanying drawings.

[0021] FIG1 is a diagram showing an application scenario of a distance measuring device according to an example of the present invention.

[0022] FIG. 2A is a schematic diagram showing a sawtooth linear frequency modulation continuous wave according to an example of the present invention.

[0023] FIG. 2B is a schematic diagram showing a triangular linear frequency modulation continuous wave according to an example of the present invention.

[0024] FIG2C is a schematic diagram showing triangular linear frequency modulation continuous wave ranging according to an example of the present invention.

[0025] FIG3 is a flow chart illustrating a method for extending a ranging range according to an example of the present invention.

[0026] FIG4 is a schematic diagram showing the principle of a method for extending a ranging range according to an example of the present invention.

[0027] FIG5 is a schematic diagram showing a first embodiment of a distance measuring device according to an example of the present invention.

[0028] FIG6 is a schematic diagram showing a curve of the relationship between the intermediate frequency of the interference signal formed by the delayed reference light and the return light and the distance to the target according to an example of the present invention.

[0029] FIG7 is a schematic diagram showing a second embodiment of a distance measuring device according to an example of the present invention.

[0030] FIG8 is a schematic diagram showing a third embodiment of a distance measuring device according to an example of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments filled in by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] It should be noted that the terms "first", "second", "third" and "fourth" in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices. In the following description, the same symbols are given to the same components, and repeated descriptions are omitted. In addition, the drawings are only schematic diagrams, and the ratio of the sizes of the components to each other or the shapes of the components may be different from the actual ones.

[0033] The method for extending the range of frequency modulated continuous wave ranging provided in the first aspect of the present invention can be applied to measuring the distance of a target using a ranging device. In the present invention, the method for extending the range of frequency modulated continuous wave ranging can also be referred to as a method for extending the ranging range, a method for expanding the ranging range, a method for expanding the measured distance, and a method for expanding the measured distance.

[0034] A second aspect of the present invention provides a device for extending the range of frequency modulated continuous wave ranging, which is a device for measuring the distance to a target (hereinafter referred to as a ranging device). In the present invention, the ranging device may also be referred to as a distance measuring device or a device for measuring the distance to a target.

[0035] In the present invention, the target may be referred to as a measured object, a measured target, a measured workpiece, or a measured component. The distance to the target may refer to the distance from a measuring point on the surface of the target to a distance measuring device, and may also be referred to as the measured distance of the target, or simply the measured distance.

[0036] In the present invention, the distance measurement range may refer to the maximum measurement distance that the distance measurement device can measure. In the present invention, the distance measurement resolution of the distance measurement device may refer to the minimum difference between two different measurement distances that can be distinguished and obtained.

[0037] FIG1 is a diagram illustrating an application scenario of a ranging device 20 according to an example of the present invention. FIG2A is a schematic diagram illustrating a sawtooth linear frequency modulation continuous wave according to an example of the present invention. FIG2B is a schematic diagram illustrating a triangular linear frequency modulation continuous wave according to an example of the present invention. FIG2C is a schematic diagram illustrating ranging based on a triangular linear frequency modulation continuous wave according to an example of the present invention.

[0038] 1 , in some examples, the distance measuring device 20 may measure the distance D of the target 40 based on a frequency-modulated continuous wave (FMCW) ranging method.

[0039] In some examples, the ranging device 20 can measure the distance D of the target 40 based on a linear frequency modulated continuous wave ranging method. In this case, the ranging device 20 transmits a linear frequency modulated continuous wave signal (also referred to as measuring light 10), whose frequency changes linearly with time. The measuring light 10 is emitted to a measuring point P on the surface of the target 40. The ranging device 20 then receives the signal scattered back from the measuring point P (also referred to as return light 11). The distance D of the target 40 causes the frequency of the return light 11 to change relative to the measuring light 10. By measuring this frequency change, the distance D of the target 40 can be calculated (see Figure 1).

[0040] It should be noted that, in the present invention, scattering may refer to a phenomenon in which the measurement light 10 is deflected on the surface of the target 40. In some examples, scattering may include reflection or diffuse reflection.

[0041] In some examples, the chirp continuous wave may be a sawtooth chirp continuous wave (see FIG. 2A ). In some examples, the chirp continuous wave may be a triangle chirp continuous wave (see FIG. 2B ).

[0042] In some examples, the relationship between the frequency and time of the linear frequency modulated continuous wave can be described by a frequency function, that is, the frequency function can describe the change of the frequency of the linear frequency modulated continuous wave over time. (See Figures 2A and 2B)

[0043] In some examples, the linear frequency modulation continuous wave frequency function may include a frequency modulation bandwidth BW and a frequency modulation period T (see Figures 2A and 2B). The frequency modulation bandwidth BW may represent the linear change range of frequency over time, and the frequency modulation period T may represent the time required for the frequency to change from the starting value to the final value. The frequency modulation bandwidth BW is also called the sweeping bandwidth, and the frequency modulation period T is also called the sweeping period.

[0044] In the present invention, the ranging method based on triangular linear frequency modulation continuous wave is taken as an example to introduce the method for extending the ranging range provided by the first aspect of the present invention and the ranging device 20 provided by the second aspect.

[0045] In some examples, the light beam emitted by the distance measuring device 20 may be a laser. In some examples, the light beam emitted by the distance measuring device 20 may be output as measurement light 10 to a measurement point P on the surface of the target 40 and scattered by the measurement point P to form return light 11.

[0046] In some examples, the light beam emitted by the distance measuring device 20 can also serve as reference light 12 (also called local oscillator light) to interfere with the return light 11, forming an interference signal. In this case, an interference signal carrying information about the measured distance D can be formed. In FIG2C , the frequency difference f0 is the intermediate frequency of the interference signal reflecting the measured distance D. Based on the intermediate frequency of the interference signal, the distance D to the target 40 can be calculated.

[0047] 2C , in some examples, the return light 11 acquired by the ranging device 20 can have a flight time t relative to the reference light 12 that is related to the measured distance D. In some examples, the flight time t can be understood as the time required for the measurement light 10 to travel from the ranging device 20 to the surface of the target 40, be scattered to form the return light 11, and then for the return light 11 to return to the ranging device 20.

[0048] According to prior art, the distance D of the target 40 is proportional to the intermediate frequency of the interference signal (i.e., the frequency difference f0 in FIG2C ). As the distance D of the target 40 increases, the flight time t increases, and the intermediate frequency of the interference signal also increases. This places higher demands on the components of the ranging device 20 (such as the analog-to-digital converter 323, described later) and the signal processing speed. Consequently, the ranging range of the ranging device 20 is limited by the intermediate frequency of the interference signal.

[0049] In some existing technologies, the limitation of the intermediate frequency of the interference signal on the ranging range can be reduced by reducing the frequency modulation bandwidth BW of the measuring light 10. In other words, the limitation of the intermediate frequency of the interference signal on the ranging range can be reduced by reducing the slope of the frequency function of the measuring light 10. However, based on existing technologies, it can be known that the ranging resolution of the ranging device 20 is negatively correlated with the frequency modulation bandwidth BW of the linear frequency modulation continuous wave, that is, the smaller the frequency modulation bandwidth BW, the smaller the ranging resolution.

[0050] Based on the above considerations, a first aspect of the present invention provides a method for extending a ranging range.

[0051] FIG3 is a flow chart illustrating a method for extending the ranging range according to an example of the present invention. FIG4 is a schematic diagram illustrating the principle of the method for extending the ranging range according to an example of the present invention. FIG5 is a schematic diagram illustrating a first embodiment of a ranging device 20 according to an example of the present invention. FIG6 is a schematic diagram illustrating a curve showing the relationship between the intermediate frequency of the interference signal formed by the delayed reference light 14 and the return light 11 according to an example of the present invention and the distance D to the target 40. FIG7 is a schematic diagram illustrating a second embodiment of a ranging device 20 according to an example of the present invention. FIG8 is a schematic diagram illustrating a third embodiment of a ranging device 20 according to an example of the present invention.

[0052] 3 , in some examples, a method for extending a ranging range may include: outputting a measuring light 10 to a target 40 and acquiring a return light 11 formed by scattering the measuring light 10 by the target 40 (step S10); inputting a reference light 12 to a delay network 21 of a ranging device 20 so that the delay network 21 outputs at least one delayed reference light 14 (step S20); acquiring at least one interference signal based on the at least one delayed reference light 14 and the return light 11 (step S30); and acquiring a distance D of the target 40 based on the distance interval and the at least one interference signal (step S40).

[0053] In some examples, in step S10, measurement light 10 may be output to target 40 and return light 11 may be obtained, which is formed by scattered measurement light 10 by target 40. In this case, return light 11 may be subsequently interfered with reference light 12 (described later) to form an interference signal, and the distance D to target 40 may be obtained from the interference signal.

[0054] 5 , in some examples, the distance measuring device 20 may include a generating module 22 , and the generating module 22 may output the emission light 13 .

[0055] In some examples, the distance measuring device 20 may include an isolator 23. In this case, the isolator 23 can reduce the situation where the emission light 13 is reflected to the generating module 22, thereby protecting the generating module 22.

[0056] In some examples, the emitted light 13 may be linear frequency modulated continuous light. In this case, by using the linear frequency modulated continuous light to measure the distance D of the target 40, the accuracy of distance measurement can be improved.

[0057] In some examples, the emitted light 13 may be a triangle wave linear frequency modulated continuous wave. In some examples, the emitted light 13 may be a sawtooth linear frequency modulated continuous wave.

[0058] In some examples, emitted light 13 can be split into measurement light 10 and reference light 12. Measurement light 10 can be output to target 40, and distance measuring device 20 can obtain return light 11 formed by scattered measurement light 10 by target 40. Thus, return light 11 can interfere with reference light 12 to form an interference signal that carries information about the distance D to target 40.

[0059] In some examples, the measuring light 10 may be linear frequency modulated continuous light, in some examples, the measuring light 10 may be triangle wave linear frequency modulated continuous light, or in some examples, the measuring light 10 may be sawtooth wave linear frequency modulated continuous light.

[0060] In some examples, the reference light 12 may be linear frequency modulated continuous light, in some examples, the reference light 12 may be triangle wave linear frequency modulated continuous light, or in some examples, the reference light 12 may be sawtooth wave linear frequency modulated continuous light.

[0061] In some examples, the measuring light 10 and the reference light 12 may be linear frequency modulated continuous light. In this case, the measuring light 10 and the reference light 12 may have the same frequency characteristics, which can reduce the processing requirements for the interference signal and thus simplify the design.

[0062] In some examples, the distance measuring device 20 may include a plurality of beam splitters 24. In this case, the beam splitters 24 may be provided to split a beam of light into a plurality of beams of light according to design requirements.

[0063] In some examples, beam splitter 24 may be an optical device that splits an incident light beam into two or more light beams. In some examples, beam splitter 24 may not change the polarization state of the incident light. In this case, the consistency of measurement light 10 and reference light 12 can be maintained as much as possible.

[0064] In some examples, beam splitter 24 can also function as a beam combiner. In other words, the input and output of beam splitter 24 can be interchanged. In this case, multiple beams can be input into beam splitter 24 according to design requirements, and beam splitter 24 can combine the multiple beams into a single output beam.

[0065] In the present invention, beam splitters and beam combiners can be collectively referred to as beam splitters. In Figures 5, 7 and 8, beam splitter 241, beam splitter 242, beam splitter 243, beam splitter 244, beam splitter 245 and beam splitter 246 are used as beam splitters; in Figure 7, beam splitter 247 is used as a beam combiner.

[0066] In some examples, beam splitter 24 may be a polarization-maintaining beam splitter, in which case beam splitter 24 is capable of maintaining the polarization state of the light beam.

[0067] In some examples, the measuring light 10 and the reference light 12 can be emitted by the same generating module 22. In this way, the consistency of the measuring light 10 and the reference light 12 can be better maintained.

[0068] In some examples, the measurement light 10 and the reference light 12 can be emitted by different generating modules 22. In this case, compared to a single generating module 22, there is no need to use a beam splitter 241 to split the emitted light 13. This reduces the loss of light intensity of the emitted light 13 caused by the beam splitter 241. This allows the measurement light 10 to be output to a farther target 40, and stronger return light 11 is obtained. This makes the signal of the return light 11 easier to detect and resolve, thereby obtaining a stronger interference signal, thereby improving the accuracy and sensitivity of ranging.

[0069] In some examples, the ranging device 20 may include a lens module 25. The measuring light 10 may be transmitted to the lens module 25. The lens module 25 may transmit the measuring light 10 to the target 40 and obtain return light 11 formed by scattered measurement light 10 by the target 40. In this case, the lens module 25 may output the measuring light 10 to the surface of the target 40 in a well-focused state, thereby facilitating the acquisition of stronger return light 11. The lens module 25 may also accurately obtain the return light 11.

[0070] In some examples, the distance measuring device 20 may include a circulator 26, which can guide the measurement light 10 to be transmitted to the lens module 25 and simultaneously guide the return light 11 to be transmitted to the coupling module 27 (described later). In this case, the use of the circulator 26 can conveniently change the direction of the light beam, thereby simplifying the optical path design of the distance measuring device 20.

[0071] In some examples, the return light 11 may be split into at least one path of return light.

[0072] In some examples, in step S20 , the reference light 12 may be input to the delay network 21 of the distance measuring device 20 , so that the delay network 21 outputs at least one delayed reference light 14 (see FIG. 4 and FIG. 5 ).

[0073] 5 , in some examples, the distance measuring device 20 may include a delay network 21. In some examples, the delay network 21 may include a plurality of preset delay parameters.

[0074] In some examples, the reference light 12 can be input into the delay network 21 of the distance measuring device 20. The delay network 21 can output at least one delayed reference light 14. The delayed reference light 14 can have preset delay parameters that match the reference light 12. In other words, compared with the reference light 12, each delayed reference light 14 output by the delay network 21 has its own preset delay parameter that matches the delay parameters of the reference light 12.

[0075] In this case, referring to FIG4 , by inputting the reference light 12 into the delay network 21, at least one delayed reference light 14 is obtained, which has preset delay parameters that match the reference light 12 and are known. In other words, the delay network 21 functions to keep the position of the target 40 unchanged, and in disguise moves the distance measuring device 20 toward the target 40 by a known distance.

[0076] It should be noted that in actual operation, the ranging device 20 is not actually moved in the direction approaching the target 40. Instead, based on the known preset delay parameters, the actual flight time t1 of the return light 11 relative to the reference light 12 is disguisedly shortened to the flight time t2 of the return light 11 relative to the delayed reference light 14 through the delay network 21. The shortened time t3 can be obtained based on the known preset delay parameters, thereby reducing the frequency difference between the reference light 12 and the return light 11. That is, compared with the interference signal formed by the interference between the reference light 12 and the return light 11, the intermediate frequency of the interference signal formed by the interference between the delayed reference light 14 and the return light 11 is correspondingly reduced (that is, the intermediate frequency f01 shown in FIG4 is reduced to the intermediate frequency f02). As a result, the sampling rate of the processing circuit of the ranging device 20 and the complexity of the related circuit design can be reduced. At the same time, a larger frequency modulation bandwidth BW can be set to achieve a higher ranging resolution, thereby extending the ranging range.

[0077] Referring to FIG5 , in some examples, the delay network 21 may include multiple delay paths. For example, the delay network 21 may include two delay paths, three delay paths, four delay paths, five delay paths, six delay paths, or more delay paths. For ease of description, the following description assumes that the delay network 21 includes six delay paths.

[0078] In some examples, multiple delay paths can be arranged in parallel. In this case, the delay network 21 has a simple structure, which can facilitate the independent design of each delay path. Moreover, by arranging the delay paths in parallel, when a delay path fails, it will not affect other delay paths, which is also convenient for maintenance.

[0079] 5 , in some examples, multiple delay paths may include a first delay path 211 , a second delay path 212 , a third delay path 213 , a fourth delay path 214 , a fifth delay path 215 , and a sixth delay path 216 , and each delay path may be arranged in parallel.

[0080] In some examples, the reference light 12 split by the beam splitter 243 can be transmitted to the delay paths to form delayed reference light 14. Specifically, the reference light 12 can be split by the beam splitter 243 into six reference light beams 12. The six reference light beams 12 can be input into the six delay paths, and after passing through the six delay paths, the six delayed reference light beams 14 can be output.

[0081] For ease of explanation, the six delayed reference lights 14 output by the six delay paths are named respectively: the first delay path 211 corresponds to the output of the first delayed reference light 2111, the second delay path 212 corresponds to the output of the second delayed reference light 2121, the third delay path 213 corresponds to the output of the third delayed reference light 2131, the fourth delay path 214 corresponds to the output of the fourth delayed reference light 2141, the fifth delay path 215 corresponds to the output of the fifth delayed reference light 2151, and the sixth delay path 216 corresponds to the output of the sixth delayed reference light 2161.

[0082] In some examples, the first delay path 211 , the second delay path 212 , the third delay path 213 , the fourth delay path 214 , the fifth delay path 215 , and the sixth delay path 216 may have different preset delay parameters, respectively.

[0083] In some examples, the delay path of the distance measuring device 20 can be a delay fiber. In some examples, the delay fiber can be a polarization-maintaining delay fiber. In this case, the delay fiber can delay the propagation of the reference light 12 while maintaining the polarization state of the reference light 12.

[0084] In some examples, the preset delay parameter can be represented by the length of the delay fiber. In other words, based on the known length of the delay fiber, the reduction in the actual flight time t1 of the return light 11 (ie, time t3 shown in FIG4 ) can be determined.

[0085] In some examples, the lengths of the delay fibers used in the first delay path 211, the second delay path 212, the third delay path 213, the fourth delay path 214, the fifth delay path 215, and the sixth delay path 216 may be known, i.e., each delay path may have a known delay distance (i.e., the length of the delay fiber). In some examples, the delay distance may be used to characterize a preset delay parameter.

[0086] In some examples, the delay distance of each delay path may be different, in other words, the preset delay parameters of each delayed reference light 14 may be different. Thus, different delay paths can be selected according to different ranging ranges.

[0087] For the sake of convenience, the six delay distances corresponding to the six delay paths are named respectively, that is, the first delay path 211 can have a first delay distance, the second delay path 212 can have a second delay distance, the third delay path 213 can have a third delay distance, the fourth delay path 214 can have a fourth delay distance, the fifth delay path 215 can have a fifth delay distance, and the sixth delay path 216 can have a sixth delay distance.

[0088] In some examples, in step S30 , at least one interference signal may be obtained based on at least one delayed reference light 14 and the return light 11 .

[0089] 5 , in some examples, the ranging device 20 may include a coupling module 27 .

[0090] In some examples, at least one delayed reference light 14 can be transmitted to the coupling module 27 separately with the return light 11 , and the coupling module 27 can output at least one interference signal.

[0091] In some examples, coupling module 27 may be a mixer. In some examples, coupling module 27 may be a beam combiner.

[0092] In some examples, the return light 11 can be divided into six paths of return light 11 by the beam splitter 242, and the six paths of return light 11 can respectively interfere with the first delayed reference light 2111, the second delayed reference light 2121, the third delayed reference light 2131, the fourth delayed reference light 2141, the fifth delayed reference light 2151, and the sixth delayed reference light 2161 in the coupling module 27 to obtain the first interference signal 21111, the second interference signal 21211, the third interference signal 21311, the fourth interference signal 21411, the fifth interference signal 21511, and the sixth interference signal 21611, respectively.

[0093] In some examples, the intermediate frequency of the interference signal formed by the interference between the delayed reference light 14 and the return light 11, the distance D of the target 40, and the delay distance of the delay path may have a relationship as shown in Formula 1:

[0094] Wherein, f represents the intermediate frequency of the interference signal formed by the interference between the delayed reference light 14 and the return light 11; D represents the distance D of the target 40, REF represents the delayed distance of the delay path, c represents the speed of light, n represents the refractive index of the delay path, BW represents the frequency modulation bandwidth BW, and T represents the frequency modulation period T.

[0095] In some examples, when the delay path is a delay fiber, n may represent the refractive index of the delay fiber.

[0096] In some examples, a relationship curve between the intermediate frequency and the distance D of the target 40 (hereinafter referred to as the relationship curve) can be obtained based on Formula 1. Taking the relationship curve between the intermediate frequency and the distance D of the target 40 shown in FIG6 as an example, the relationship curve can be obtained by setting the following parameters, namely: the first delay distance REF1 is 10 meters, the second delay distance REF2 is 20 meters, the third delay distance REF3 is 30 meters, the fourth delay distance REF4 is 45 meters, the fifth delay distance REF5 is 55 meters, the sixth delay distance REF6 is 66 meters, and the speed of light c is 3×10 8 m / s, BW / T is 82.7THz / s, and n is 1.48.

[0097] 6 , in some examples, the relationship curve between the intermediate frequency f1 of the first interference signal 21111 and the distance D of the target 40 can be a first curve P1, the relationship curve between the intermediate frequency f2 of the second interference signal 21211 and the distance D of the target 40 can be a second curve P2, the relationship curve between the intermediate frequency f3 of the third interference signal 21311 and the distance D of the target 40 can be a third curve P3, the relationship curve between the intermediate frequency f4 of the fourth interference signal 21411 and the distance D of the target 40 can be a fourth curve P4, the relationship curve between the intermediate frequency f5 of the fifth interference signal 21511 and the distance D of the target 40 can be a fifth curve P5, and the relationship curve between the intermediate frequency f6 of the sixth interference signal 21611 and the distance D of the target 40 can be a sixth curve P6.

[0098] In some examples, the preset delay parameters of a measurement range (described later) can be set in various ways, where M represents the length of the distance D between the intermediate frequency of any interference signal 0 and the low-pass cutoff frequency (described later) of the filter 322. For example, if a measurement range includes two delay paths, the range of the distance D involved in the first interference signal 21111 can be expressed as (REF1×n / 2-M, REF1×n / 2+M), where REF1×n / 2 can be no greater than M; and the range of the distance D involved in the second interference signal 21211 can be expressed as (REF2×n / 2-M, REF2×n / 2+M), where REF2×n / 2-M can be equal to REF1×n / 2. If a measurement range includes three delay paths, the range of distance D involved in the first interference signal 21111 can be expressed as (REF1×n / 2-M, REF1×n / 2+M), and REF1×n / 2 may not be greater than M; the range of distance D involved in the second interference signal 21211 can be expressed as (REF2×n / 2-M, REF2×n / 2+M), and REF2×n / 2-M may not be greater than REF1×n / 2; the range of distance D involved in the third interference signal 21311 can be expressed as (REF3×n / 2-M, REF3×n / 2+M), and REF3×n / 2-M may not be less than REF1×n / 2.

[0099] It should be noted that there is no single way to set the preset delay parameters. In some examples, the preset delay parameters can be configured so that at least one of the relationship curves corresponding to the distance intervals has a monotonic interval, and the types and combinations of interference signals involved in different distance intervals can be different. This can facilitate the division of distance intervals and simplify the calculation process of the measured distance (described later).

[0100] In the present invention, a "combination of interference signal types" may also be referred to as a "composition of interference signals," and specifically refers to the following: when measuring the distance D to the target 40, the interference signal obtained includes only interference signals generated by matching the delay path within the distance interval in which the distance D to the target 40 lies. For example, referring to FIG6 , when the distance interval in which the distance D to the target 40 lies is distance interval D2, the "combination of interference signal types" or "composition of interference signals" may include only the first interference signal 21111 and the second interference signal 21211; and when the distance interval in which the distance D to the target 40 lies is distance interval D3, the "combination of interference signal types" or "composition of interference signals" may include only the first interference signal 21111, the second interference signal 21211, and the third interference signal 21311.

[0101] 6 , in some examples, the delay network 21 may be used to divide the ranging range of the ranging device 20 into multiple distance intervals.

[0102] In some examples, at least one interference signal can match the distance interval in which the target 40 is located. In other words, the distance interval in which the distance D of the target 40 is located can be known through the obtained interference signal. For example, the ranging range of Figure 6 (i.e., 60 meters) can be divided into 11 distance intervals (i.e., distance interval D1 to distance interval D11 shown in Figure 6). In this case, by determining whether the return light 11 interferes with at least one delayed reference light 14 to generate an interference signal, the ranging range can be divided into multiple distance intervals. Therefore, when measuring the distance D of the target 40, the distance interval in which the distance D of the target 40 is located can be known, so that it is convenient to select the matched interference signal to calculate the distance D of the target 40.

[0103] In some examples, the relationship curves may overlap. In other words, adjacent relationship curves may cover the same measured distance D. This allows the entire ranging range to be fully covered. That is, for any measured distance D within the ranging range, the corresponding intermediate frequency can be obtained, facilitating calculation of the distance D to the target 40.

[0104] In some examples, in the distance interval, the corresponding relationship curve may have a monotonic interval. In other words, in each distance interval, as the distance D of the target 40 changes, the corresponding intermediate frequency of the interference signal may monotonically increase or monotonically decrease (see FIG6 ). In this case, the calculation process of the measured distance D can be simplified; if in the distance interval, as the distance D of the target 40 changes, the corresponding intermediate frequency includes both an ascending interval and a descending interval (for example, the second curve P2 corresponding to the distance interval D2 in FIG6 ), then using the relationship curve to calculate the measured distance D will increase the complexity of the calculation (it is necessary to determine whether the distance D of the target 40 corresponds to the ascending segment or the descending segment of the corresponding relationship curve), and the intermediate frequency corresponding to the relationship curve is low, which is not conducive to obtaining a more accurate measurement of the distance D.

[0105] In some examples, at least adjacent relationship curves can cover the same measured distance D and have the same monotonic interval. For example, in distance interval D2 in Figure 6 , the first curve P1 and the second curve P2 overlap and cover part of the same measured distance D, and both have a decreasing segment. This facilitates the division of distance intervals, ensuring that the relationship curves corresponding to each distance interval have a monotonic increasing or decreasing interval, thereby simplifying the calculation process of the measured distance D and improving distance measurement accuracy.

[0106] In some examples, the distance intervals can be divided based on the low-pass cutoff frequency used to filter the interference signal. Specifically, in the relationship curve, the distance intervals can be divided based on the measured distance D corresponding to the low-pass cutoff frequency as the boundary. Taking Figure 6 as an example, the low-pass cutoff frequency is 3×10 6 Hz, you can select the frequency 3×10 6 The corresponding measured distance D is the limit of each distance interval. In this case, it is advantageous to make the composition of the interference signal corresponding to each distance interval unique, thereby facilitating the determination of the distance interval in which the distance D of the target 40 lies.

[0107] In some examples, the low-pass cutoff frequency may be determined by the filter 322 of the distance measuring device 20 (described later). In this case, a more appropriate intermediate frequency can be obtained to calculate the distance D of the target 40.

[0108] In some examples, the method for extending the ranging range may include obtaining, based on at least one interference signal, a combined code that indicates whether the delayed reference light 14 output by the delay network 21 interferes with the return light 11. In this case, when measuring the distance D to the target 40, the combined code facilitates digital processing to achieve the method for extending the ranging range.

[0109] In some examples, a combination code having 6 digits may be formed based on the first interference signal 21111, the second interference signal 21211, the third interference signal 21311, the fourth interference signal 21411, the fifth interference signal 21511, and the sixth interference signal 21611. Taking the first interference signal 21111 as an example, when measuring the distance D of the target 40, if the first interference signal 21111 is detected, the code corresponding to the first interference signal 21111 in the combination code is set to 1; otherwise, the code corresponding to the first interference signal 21111 is set to 0.

[0110] In some examples, the code corresponding to the first interference signal 21111 can be set as the first code, the code corresponding to the second interference signal 21211 can be set as the second code, the code corresponding to the third interference signal 21311 can be set as the third code, the code corresponding to the fourth interference signal 21411 can be set as the fourth code, the code corresponding to the fifth interference signal 21511 can be set as the fifth code, and the code corresponding to the sixth interference signal 21611 can be set as the sixth code.

[0111] In some examples, the first code, the second code, the third code, the fourth code, the fifth code, and the sixth code may be sequentially arranged to form a combined code. For example, when the first code is 1, the second code is 0, the third code is 0, the fourth code is 0, the fifth code is 0, and the sixth code is 0, the combined code may be 100000.

[0112] In some examples, the method of extending the ranging range may include obtaining the distance interval of the target 40 based on the combined code. In this case, when measuring the distance D of the target 40, the ranging device 20 can determine the distance interval of the target 40 by obtaining the combined code.

[0113] 6 , in some examples, when the combined code is 100000, the distance D of the target 40 may be located in the distance interval D1.

[0114] In some examples, when the combined code is 110000, the distance D of the target 40 may be located in the distance interval D2.

[0115] In some examples, when the combined code is 111000, the distance D of the target 40 may be located in the distance interval D3.

[0116] In some examples, when the combined code is 011000, the distance D of the target 40 may be located in the distance interval D4.

[0117] In some examples, when the combined code is 011100, the distance D of the target 40 may be located in the distance interval D5.

[0118] In some examples, when the combined code is 001100, the distance D of the target 40 may be located in the distance interval D6.

[0119] In some examples, when the combined code is 001110, the distance D of the target 40 may be located in the distance interval D7.

[0120] In some examples, when the combined code is 000110, the distance D of the target 40 may be located in the distance interval D8.

[0121] In some examples, when the combined code is 000111, the distance D of the target 40 may be located in the distance interval D9.

[0122] In some examples, when the combined code is 000011, the distance D of the target 40 may be located in the distance interval D10.

[0123] In some examples, when the combined code is 000001, the distance D of the target 40 may be located in the distance interval D11.

[0124] In some examples, multiple distance intervals can be matched with multiple preset delay parameters. For example, in distance interval D2 of FIG6 , distance interval D2 can correspond to first interference signal 21111 and second interference signal 21211. First interference signal 21111 can correspond to first delayed reference light 2111, and second interference signal 21211 can correspond to second delayed reference light 2121. Distance interval D2 can be matched with the preset delay parameters corresponding to first delayed reference light 2111 and second delayed reference light 2121, respectively.

[0125] In some examples, each delay path has a preset delay parameter corresponding to each distance interval. In this case, the delayed reference light 14 with the appropriate preset delay parameter can be caused to interfere with the return light 11 according to the distance D of the target 40. For example, when the distance D of the target 40 is small, the delayed reference light 14 with a smaller preset delay parameter (i.e., a smaller time t3 in FIG. 4 ) can be caused to interfere with the return light 11. When the distance D of the target 40 is large, the delayed reference light 14 with a larger preset delay parameter (i.e., a larger time t3 in FIG. 4 ) can be caused to interfere with the return light 11. This can help overcome the limitations of the interference signal's intermediate frequency, the frequency modulation bandwidth BW, and the frequency modulation period T on the ranging range, thereby expanding the ranging range of the ranging device 20. Moreover, since the ranging range is divided into multiple small distance intervals, it is advantageous to increase the frequency modulation bandwidth BW within each distance interval to increase the ranging resolution.

[0126] In some examples, the method for extending the ranging range may include dividing multiple delay paths into at least two types of range paths based on multiple distance intervals, where the range paths may match at least one distance interval. Taking Figure 6 as an example, distance intervals D1 to D6 may be divided into a first range, and the corresponding first delay path 211, second delay path 212, and third delay path 213 may be divided into first range paths; distance intervals D7 to D11 may be divided into a second range, and the corresponding fourth delay path 214, fifth delay path 215, and sixth delay path 216 may be divided into second range paths.

[0127] In this case, when measuring the distance D of the target 40, the range and corresponding range path of the distance D of the target 40 can be preliminarily determined based on the interference signal, and the delay path to be used can be determined based on the range, thereby reducing the workload of interference signal detection and improving the efficiency of ranging. For example, when the distance D of the target 40 is detected to be within the first range based on the interference signal, it is only necessary to subsequently determine the distance interval within which the distance D of the target 40 is located based on the first interference signal 21111, the second interference signal 21211, and the third interference signal 21311.

[0128] In some examples, the method for extending the ranging range may include obtaining a range path that matches the distance interval of target 40 based on at least one interference signal. In this case, when measuring the distance D of target 40, the range of distance D of target 40 and the corresponding range path can be preliminarily determined based on the interference signal.

[0129] In some examples, the method for extending the ranging range may include obtaining a combined code that matches the range path based on at least one interference signal and the range path. In this case, the number of bits in the combined code can be reduced. Taking Figure 6 as an example, when determining that the distance D of target 40 is within the first range, only the first range path corresponding to the first range is required to form the combined code, thereby reducing the combined code from six digits to three digits, thereby reducing the computational complexity and improving the ranging speed.

[0130] In some examples, the method for extending the ranging range may include obtaining the distance interval of the target 40 based on the combined code matching the range path. Thus, the distance D of the target 40 can be calculated based on the distance interval where the distance D of the target 40 is located by selecting a matching interference signal.

[0131] In some examples, within the same measurement range, at least adjacent relationship curves may cover the same measurement distance D and have the same monotonic interval.

[0132] In some examples, the relationship curves belonging to different ranges may overlap at the intersection of two adjacent ranges, thereby enabling the two adjacent ranges to completely cover the distance D of the target 40 .

[0133] 7 , in some examples, the distance measuring device 20 may include a range optical switch 28 that divides multiple delay paths into at least two types of range paths based on a plurality of distance intervals.

[0134] In some examples, the range optical switch 28 may include an input terminal and multiple output terminals corresponding to different range paths. In this case, the input terminal of the range optical switch 28 can only be connected to one output terminal at a time, thereby dividing the multiple delay paths into range paths belonging to different ranges.

[0135] In some examples, the output end of the range optical switch 28 can be connected to a matching delay path, and the reference light 12 can be input into the delay network 21 via the range optical switch 28. In this case, when measuring the distance D to the target 40, the range optical switch 28 can be controlled to obtain a delay path corresponding to the range, thereby reducing the workload of interference signal detection and improving the efficiency of distance measurement.

[0136] In some examples, the range optical switch 28 may have one input and two outputs (i.e., a one-to-two range optical switch), and the two outputs may be connected to two range paths, respectively, via two beam splitters 245. In this case, by using a one-to-two range optical switch, the ranging range can be divided into two ranges and corresponding two range paths.

[0137] 5 and 7 , in some examples, the ranging device 20 may include a processing module 29 .

[0138] In some examples, if the processing module 29 does not receive at least one interference signal, it can control the range optical switch 28 to switch the range path. In this case, when measuring the distance D of the target 40, if the processing module 29 does not receive the interference signal, it determines that the distance D of the target 40 is not within the range defined by the delay path connected to the output end of the current range optical switch 28. The processing module 29 can then switch the range optical switch 28 to another range path, thereby enabling switching between different range paths.

[0139] In some examples, if the processing module 29 detects no interference signal after the range optical switch 28 switches on all range paths, it is determined that the distance D of the target 40 exceeds the ranging range of the ranging device 20. In this case, the distance between the target 40 and the ranging device 20 needs to be shortened so that the target 40 is within the ranging range.

[0140] 8 , in some examples, multiple delay paths can be connected in series. In this case, the number of components in the distance measuring device 20 can be reduced, thereby facilitating portability and miniaturization of the distance measuring device 20 .

[0141] Referring to Figure 8 , in some examples, the ranging device 20 may include a time-delay network optical switch 31. In some examples, the time-delay network optical switch 31 may include a multi-input, multi-output optical switch. For example, the two-input, two-output optical switch 311 shown in Figure 8 may have connection logic that allows the first input to be connected to the first output, and the second input to be connected to the second output; or the first input to be connected to the second output, and the second input to be connected to the first output.

[0142] In some examples, the time-delay network optical switch 31 may include a single-input multiple-output optical switch 312 .

[0143] Referring to Figure 8 , in some examples, delay paths can be arranged in series using multiple two-input, two-output optical switches 311 and multiple single-input, two-output optical switches 312. In this case, by switching between multiple two-input, two-output optical switches 311 and multiple single-input, two-output optical switches 312, multiple delay paths that meet design requirements can be formed, and corresponding interference signals can be obtained.

[0144] In the present invention, the single-input two-output optical switch 312 can also be used as a two-input single-output optical switch.

[0145] Referring to Figure 8, in some examples, when measuring the distance D of the target 40, the first delay path 211 is first connected, and a first interference signal 21111 is obtained; then the first delay path 211 is closed, and the second delay path 212 is connected, and a second interference signal 21211 is obtained; and by controlling the delay network optical switch 31 in turn, a third interference signal 21311, a fourth interference signal 21411, a fifth interference signal 21511 and a sixth interference signal 21611 are obtained, thereby obtaining a relationship diagram between the interference signal and the distance D of the target 40 as shown in Figure 6.

[0146] In some examples, the switching logic of the delay network optical switch 31 can be adaptively designed to adjust the preset delay parameters of the delay path. For example, by configuring the switching logic of the delay network optical switch 31, the first delay path 211 and the second delay path 212 can be combined to form a new delay path, thereby generating a new interference signal. In this case, the preset delay parameters of the delay network 21 can be flexibly adjusted, thereby improving the flexibility of ranging and enabling timely adjustment of the preset delay parameters of the delay network 21 based on the requirements of the ranging range.

[0147] In some examples, the processing module 29 can control the switching logic of the delay network optical switch 31 .

[0148] In some examples, in step S40 , the distance D of the target 40 may be obtained based on the distance interval and at least one interference signal.

[0149] In some examples, the method for expanding the ranging range may include obtaining a preset delay parameter that matches a preset condition based on the distance interval as a target delay parameter. The preset condition may be that the interference signal is not less than a preset threshold. In this case, once the distance interval within which the distance D of the target 40 falls is determined, the interference signal that meets the preset condition can be selected to calculate the distance D of the target 40, thereby improving ranging accuracy.

[0150] In some examples, the target delay parameter may be a preset delay parameter of a delay path corresponding to an interference signal that meets preset conditions.

[0151] In some examples, the target delay parameter may include one or more. For example, in distance interval D1 of FIG6 , the target delay parameter may include only the preset delay parameter of the first delay path 211 corresponding to the first interference signal 21111; in distance interval D3, the target delay parameter may include the preset delay parameter of the first delay path 211 corresponding to the first interference signal 21111 and the preset delay parameter of the third delay path 213 corresponding to the third interference signal 21311.

[0152] In some examples, the target delay parameter may be the length of the delay optical fiber, that is, the delay distance. For example, the target delay parameter may be at least one of the first delay distance to the sixth delay distance.

[0153] In some examples, the preset condition may include the intensity of the interference signal being no less than a preset threshold. In this case, since reference light 12 and return light 11 experience intensity loss after passing through multiple optical components in ranging device 20, selecting an interference signal with a higher intensity to calculate distance D to target 40 can improve ranging accuracy.

[0154] In some examples, the preset condition may include that the intermediate frequency of the interference signal is not less than a preset threshold. In this case, the interference signal with a lower intermediate frequency is more susceptible to noise, thereby reducing the signal-to-noise ratio. For example, when the distance D of the target 40 is close to the first delay distance, the distance D of the target 40 can be located in the distance interval D2, and the first interference signal 21111 formed by the return light 11 and the first delayed reference light 2111, and the second interference signal 21211 formed by the return light 11 and the second delayed reference light 2121 can be detected. At this time, since the intermediate frequency of the second interference signal 21211 is higher, it has a higher signal-to-noise ratio. According to the preset condition, the second delay distance can be selected as the target delay parameter (that is, when the distance D of the target 40 is in the distance interval D2, the distance D of the target 40 can be calculated based on the second delay distance and the second interference signal 21211, see Formula 3 described later). Thus, by selecting an interference signal with a larger intermediate frequency to calculate the distance D of the target 40, the resolution and accuracy of the ranging can be improved.

[0155] In some examples, the preset condition may include that the amplitude of the interference signal is not less than a preset threshold. In this case, a smaller amplitude may make it impossible to detect the interference signal, especially in an environment with high background noise. By setting the preset condition and selecting the interference signal with a larger amplitude to calculate the distance D of the target 40, the accuracy, precision, and sensitivity of the distance measurement can be improved.

[0156] In some examples, the method for extending the ranging range may include obtaining a distance D of the target 40 based on a target delay parameter, at least one interference signal, and a system parameter of the measurement light 10 .

[0157] In some examples, the system parameters of the measurement light 10 may include a frequency modulation bandwidth BW and a frequency modulation period T.

[0158] For ease of explanation, in the formula involved in the present invention, the formula parameters used to calculate the distance D of the target 40 may include:

[0159] D represents the distance D of the target 40;

[0160] REF1 represents the first delay distance; REF2 represents the second delay distance; REF3 represents the third delay distance; REF4 represents the fourth delay distance; REF5 represents the fifth delay distance; REF6 represents the sixth delay distance;

[0161] f1 represents the intermediate frequency of the first interference signal 21111; f2 represents the intermediate frequency of the second interference signal 21211; f3 represents the intermediate frequency of the third interference signal 21311; f4 represents the intermediate frequency of the fourth interference signal 21411; f5 represents the intermediate frequency of the fifth interference signal 21511; f6 represents the intermediate frequency of the sixth interference signal 21611;

[0162] c represents the speed of light, and its specific value can be 3×10 8 m / s;

[0163] n represents the refractive index of the delay path. In some examples, n may be the refractive index of the delay fiber of the delay path.

[0164] a represents the ratio of the frequency modulation bandwidth BW of the linear frequency modulation continuous wave to the frequency modulation period T, that is, a=BW / T (see FIG1 ). a can also be called the slope of the frequency function of the linear frequency modulation continuous wave.

[0165] 6 , in some examples, when the distance D of the target 40 is within the distance interval D1, the distance D of the target 40 can be obtained based on the first interference signal 21111 (i.e., the first curve P1). In some examples, the distance D of the target 40 can be calculated using Formula 2: D = 0.5 × (REF1 × n - f1 × c / a) ... Formula 2

[0166] In some examples, when the distance D of the target 40 is within the distance interval D2, the distance D of the target 40 can be obtained based on the second interference signal 21211 (i.e., the second curve P2). In some examples, the distance D of the target 40 can be calculated using Formula 3: D = 0.5 × (REF2 × n - f2 × c / a) ... Formula 3

[0167] In some examples, when the distance D of the target 40 is within the distance interval D3, the distance D of the target 40 can be obtained based on the third interference signal 21311 (i.e., the third curve P3). In some examples, the distance D of the target 40 can be calculated using Formula 4: D = 0.5 × (REF3 × n - f3 × c / a) ... Formula 4

[0168] In some examples, when the distance D of the target 40 is within the distance interval D3, the distance D of the target 40 can be obtained based on the first interference signal 21111. In some examples, the distance D of the target 40 can be calculated using Formula 5: D = 0.5 × (REF1 × n + f1 × c / a) ... Formula 5

[0169] In some examples, when the distance D of the target 40 is within the distance interval D4, the distance D of the target 40 can be obtained based on the second interference signal 21211. In some examples, the distance D of the target 40 can be calculated using Formula 6: D = 0.5 × (REF2 × n + f2 × c / a) ... Formula 6

[0170] In some examples, when the distance D of the target 40 is within the distance interval D5, the distance D of the target 40 can be obtained based on the second interference signal 21211. In some examples, the distance D of the target 40 can be calculated using Formula 7: D = 0.5 × (REF2 × n + f2 × c / a) ... Formula 7

[0171] In some examples, when the distance D of the target 40 is within the distance interval D5, the distance D of the target 40 can be obtained based on the fourth interference signal 21411 (i.e., the fourth curve P4). In some examples, the distance D of the target 40 can be calculated using Formula 8: D = 0.5 × (REF4 × n - f4 × c / a) ... Formula 8

[0172] In some examples, when the distance D of the target 40 is within the distance interval D6, the distance D of the target 40 can be obtained based on the third interference signal 21311. In some examples, the distance D of the target 40 can be calculated using Formula 9: D = 0.5 × (REF3 × n + f3 × c / a) ... Formula 9

[0173] In some examples, when the distance D of the target 40 is within the distance interval D6, the distance D of the target 40 can be obtained based on the fourth interference signal 21411. In some examples, the distance D of the target 40 can be calculated using Formula 10: D = 0.5 × (REF4 × n - f4 × c / a) ... Formula 10

[0174] In some examples, when the distance D of the target 40 is within the distance interval D7, the distance D of the target 40 can be obtained based on the third interference signal 21311. In some examples, the distance D of the target 40 can be calculated using Formula 11: D = 0.5 × (REF3 × n + f3 × c / a) ... Formula 11

[0175] In some examples, when the distance D of the target 40 is within the distance interval D7, the distance D of the target 40 can be obtained based on the fifth interference signal 21511 (i.e., the fifth curve P5). In some examples, the distance D of the target 40 can be calculated using Formula 12: D = 0.5 × (REF5 × n - f5 × c / a) ... Formula 12

[0176] In some examples, when the distance D of the target 40 is within the distance interval D8, the distance D of the target 40 can be obtained based on the fifth interference signal 21511. In some examples, the distance D of the target 40 can be calculated using Formula 13: D = 0.5 × (REF5 × n - f5 × c / a) ... Formula 13

[0177] In some examples, when the distance D of the target 40 is within the distance interval D9, the distance D of the target 40 can be obtained based on the fourth interference signal 21411. In some examples, the distance D of the target 40 can be calculated using Formula 14: D = 0.5 × (REF4 × n + f4 × c / a) ... Formula 14

[0178] In some examples, when the distance D of the target 40 is within the distance interval D9, the distance D of the target 40 can be obtained based on the sixth interference signal 21611 (i.e., the sixth curve P6). In some examples, the distance D of the target 40 can be calculated using Formula 15: D = 0.5 × (REF6 × n - f6 × c / a) ... Formula 15

[0179] In some examples, when the distance D of the target 40 is within the distance interval D10, the distance D of the target 40 can be obtained based on the fifth interference signal 21511. In some examples, the distance D of the target 40 can be calculated using Formula 16: D = 0.5 × (REF5 × n + f5 × c / a) ... Formula 16

[0180] In some examples, when the distance D of the target 40 is within the distance interval D11, the distance D of the target 40 can be obtained based on the sixth interference signal 21611. In some examples, the distance D of the target 40 can be calculated using Formula 17: D = 0.5 × (REF6 × n + f6 × c / a) ... Formula 17

[0181] In some examples, the distance measuring device 20 may include a detection module 32 , which may receive at least one interference signal output by the coupling module 27 and convert the signal into an electrical signal.

[0182] In some examples, the detection module 32 may include a photodetector 321. In this case, the photodetector 321 is capable of converting an optical signal into an electrical signal.

[0183] In some examples, the detection module 32 may include a filter 322. In some examples, the filter 322 may be a low-pass filter. In this case, the filter 322 can filter out high frequencies of the interference signal, thereby simplifying the design of the processing circuit in the ranging device 20 and removing high-frequency noise.

[0184] In some examples, the detection module 32 may include an analog-to-digital converter 323. In this case, the interference signal in analog form can be converted into a digital form signal for digital processing.

[0185] In some examples, at least one interference signal may be output to the processing module 29 of the distance measuring device 20 , and the processing module 29 may obtain the distance D of the target 40 based on the distance interval and the at least one interference signal.

[0186] In some examples, the distance measuring device 20 may include a correction module 33. In this case, the linearity of the light wave emitted by the generating module 22 can be monitored and fed back to the processing module 29 to compensate or correct the nonlinearity of the emitted light wave.

[0187] In some examples, correction module 33 may be a Mach-Zehnder interferometer. In this case, the operating conditions of the Mach-Zehnder interferometer can be changed by adjusting the relative path length or introducing a phase shift. This adjustability allows the Mach-Zehnder interferometer to adapt to different correction requirements, providing a certain degree of flexibility.

[0188] In some examples, the measurement light 10 may be split into two beams of measurement light 10 by the beam splitter 244 , wherein one beam of measurement light 10 may be output to the target 40 , and the other beam of measurement light 10 may be input to the correction module 33 .

[0189] In some examples, the optical components of the distance measuring device 20 may be connected via optical fibers. In some examples, the optical components of the distance measuring device 20 may be connected via polarization-maintaining single-mode optical fibers.

[0190] A first aspect of the present invention provides a method for extending a ranging range, which is a method for measuring a distance D of a target 40 using a ranging device 20. The ranging device 20 may include a delay network 21 for dividing the ranging range into multiple distance intervals. The delay network 21 may include multiple preset delay parameters matching the multiple distance intervals. The method for extending the ranging range may include: outputting a measuring light 10 to the target 40 and obtaining a return light 11 formed by the measuring light 10 scattered by the target 40; inputting a reference light 12 into the delay network 21 so that the delay network 21 outputs at least one delayed reference light 14, the delayed reference light 14 having a preset delay parameter matching the reference light 12; obtaining at least one interference signal based on the at least one delayed reference light 14 and the return light 11, the at least one interference signal matching the distance interval in which the target 40 is located; and obtaining the distance D of the target 40 based on the distance interval and the at least one interference signal.

[0191] In this case, by outputting the measuring light 10 to the target 40 and obtaining the return light 11, the reference light 12 is input into the delay network 21 to obtain at least one delayed reference light 14. Compared with the reference light 12 before inputting the delay network 21, the delayed reference light 14 has a preset delay parameter that matches the reference light 12 and is preset and known. In other words, the function of the delay network 21 is equivalent to keeping the position of the target 40 unchanged, and in disguise moving the ranging device 20 a known distance toward the target 40, thereby reducing the frequency difference between the reference light 12 and the return light 11. That is, compared with the interference signal formed by the interference between the reference light 12 and the return light 11, the intermediate frequency of the interference signal formed by the interference between the delayed reference light 14 and the return light 11 is correspondingly reduced.

[0192] In addition, in the method of extending the ranging range, the ranging range can be divided into multiple distance intervals by determining whether the return light 11 interferes with at least one delayed reference light 14 to generate an interference signal. Therefore, when measuring the distance D of the target 40, the distance interval in which the distance D of the target 40 is located can be known, thereby facilitating the selection of the matching interference signal to calculate the distance D of the target 40.

[0193] Therefore, the method for extending the ranging range provided by the first aspect of the present invention can reduce the sampling rate of the processing circuit of the ranging device 20 and the complexity of the related circuit design, thereby being able to overcome the limitations of the intermediate frequency of the interference signal and the frequency modulation bandwidth BW and frequency modulation period T on the ranging range, thereby being able to expand the ranging range of the ranging device 20. Moreover, since the ranging range is divided into multiple small distance intervals, it is possible to increase the ranging resolution by increasing the frequency modulation bandwidth BW within each distance interval.

[0194] A second aspect of the present invention provides a device 20 for extending the range of frequency modulated continuous wave ranging, which is a device for measuring the distance D of a target 40. The device may include: a generating module 22, a delay network 21 for dividing the ranging range of the ranging device 20 into multiple distance intervals, a coupling module 27, and a processing module 29. The delay network 21 includes multiple preset delay parameters matching the multiple distance intervals; the light wave emitted by the generating module 22 includes a measuring light 10 and a reference light 12. The measuring light 10 is output to the target 40, and the ranging device 20 obtains the scattered light of the target 40. The return light 11 is formed by the incident measurement light 10; the reference light 12 is input to the delay network 21, and the delay network 21 outputs at least one delayed reference light 14, and the delayed reference light 14 has a preset delay parameter that matches the reference light 12; the at least one delayed reference light 14 is transmitted to the coupling module 27 together with the return light 11, and the coupling module 27 outputs at least one interference signal to the processing module 29, and the at least one interference signal matches the distance interval in which the target 40 is located; the processing module 29 obtains the distance D of the target 40 based on the distance interval and the at least one interference signal.

[0195] In this case, by providing a delay network 21 and dividing the ranging range into multiple distance intervals based on the interference signal, the device of the second aspect of the present invention can reduce the sampling rate of the processing circuit and the complexity of the related circuit design, thereby being able to overcome the limitations of the intermediate frequency of the interference signal and the frequency modulation bandwidth BW and frequency modulation period T on the ranging range, thereby being able to expand the ranging range of the ranging device 20. Moreover, since the ranging range is divided into multiple small distance intervals, it is possible to increase the frequency modulation bandwidth BW within each distance interval to increase the ranging resolution.

[0196] Although the present invention has been specifically described above with reference to the accompanying drawings and examples, it will be understood that the above description does not limit the present invention in any form. Those skilled in the art may modify and alter the present invention as needed without departing from the spirit and scope of the present invention, and such modifications and alterations all fall within the scope of the present invention.

Claims

1. A method for extending the range of frequency modulated continuous wave ranging is a method for measuring the distance of a target using a ranging device, characterized in that: The distance measuring device includes a delay network for dividing the distance measuring range of the distance measuring device into multiple distance intervals, and the delay network includes multiple preset delay parameters matching the multiple distance intervals. The method for expanding the frequency modulated continuous wave distance measuring range includes: outputting measuring light to the target and obtaining return light formed by the target scattering the measuring light; inputting reference light to the delay network so that the delay network outputs at least one delayed reference light, and the delayed reference light has the preset delay parameters matching the reference light; obtaining at least one interference signal based on the at least one delayed reference light and the return light, and the at least one interference signal matches the distance interval where the target is located; and obtaining the distance of the target based on the distance interval and the at least one interference signal.

2. The method for extending the FMCW ranging range according to claim 1, characterized in that: The delay network includes multiple delay paths, and each of the delay paths has the preset delay parameters corresponding to each of the distance intervals.

3. The method for extending the FMCW ranging range according to claim 1, characterized in that: The method comprises obtaining, based on the at least one interference signal, a combined code for characterizing whether the delayed reference light output by the delay network interferes with the return light, and obtaining, based on the combined code, the distance interval at which the target is located.

4. The method for extending the FMCW ranging range according to any one of claims 1 to 3, characterized in that: The delay network includes multiple delay paths, and the method for expanding the frequency modulated continuous wave ranging range includes dividing the multiple delay paths into at least two types of range paths based on the multiple distance intervals, and the range path matches the at least one distance interval; obtaining the range path matching the distance interval where the target is located based on the at least one interference signal; obtaining a combined code matching the range path based on the at least one interference signal and the range path; and obtaining the distance interval where the target is located based on the combined code matching the range path.

5. The method for extending the FMCW ranging range according to claim 1, characterized in that: The method includes obtaining the preset delay parameter matching the preset condition based on the distance interval as the target delay parameter, wherein the preset condition is that the interference signal is not less than a preset threshold; and obtaining the distance of the target based on the target delay parameter, the at least one interference signal, and the system parameter of the measuring light.

6. The method for extending the FMCW ranging range according to claim 1, characterized in that: The preset delay parameter is configured so that at least one of the relationship curves corresponding to the distance intervals has a monotonic interval, and the type combinations of the interference signals involved in different distance intervals are different.

7. A device for extending the range of frequency modulated continuous wave ranging, which is a device for measuring the distance of a target, characterized in that: include: A generating module, a delay network for dividing the ranging range of the device into a plurality of distance intervals, a coupling module, and a processing module, wherein the delay network includes a plurality of preset delay parameters matching the plurality of distance intervals; The light waves emitted by the generating module include measuring light and reference light, the measuring light is output to the target, and the device obtains the return light formed by the measuring light scattered by the target; the reference light is input to the delay network, and the delay network outputs at least one delayed reference light, and the delayed reference light has the preset delay parameter matching the reference light; the at least one delayed reference light is respectively transmitted to the coupling module with the return light, and the coupling module outputs at least one interference signal to the processing module, and the at least one interference signal matches the distance interval where the target is located; the processing module obtains the distance of the target based on the distance interval and the at least one interference signal.

8. The device according to claim 7, characterized in that The delay network includes multiple delay paths, and the device includes a range optical switch that divides the multiple delay paths into at least two types of range paths based on the multiple distance intervals. The range optical switch includes an input end and multiple output ends corresponding to different range paths. The output end of the range optical switch is connected to the matching delay path, and the reference light is input into the delay network via the range optical switch.

9. The device according to claim 8, characterized in that If the processing module does not receive the at least one interference signal, the range optical switch is controlled to switch the range path.

10. The device according to claim 7, characterized in that The delay network includes multiple delay paths, and the multiple delay paths are arranged in parallel or in series.

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