Laser Swept-Frequency Ranging Device and Method

Abstract

The present invention provides a laser frequency-swept ranging device and method. The device includes a laser, an electro-optic modulator, a beam splitter prism, a first detector, a second detector, an analog phase detector, a measurement control circuit, and a modulation frequency source. The laser is used to emit a laser signal. The electro-optic modulator is used to intensity-modulate the laser signal to output a modulated signal. The beam splitter prism divides the modulated signal into two paths. One path is received by the first detector to generate a reference signal. The other path is reflected back by the target to be measured and then received by the second detector after being reflected by the beam splitter prism to generate a measurement signal. The analog phase detector is used to detect the phase difference between the reference signal and the measurement signal. The measurement control circuit is used to perform frequency-sweeping control on the output frequency of the modulation frequency source to generate a high-frequency modulated signal that changes according to a preset step size and feedback it to the electro-optic modulator. It is also used to determine two adjacent modulation frequencies by detecting the zero-phase difference signal and calculate the measurement distance of the target to be measured based on the two adjacent modulation frequencies.

Description

Technical Field

[0001] The present invention relates to the technical field of laser ranging, and in particular, to a laser swept-frequency ranging device and method. Background Art

[0002] Laser ranging technology modulates the intensity, frequency or polarization state of the emitted laser signal, converts the round-trip flight time of the laser over the measured distance into a change in the modulated laser signal, and accurately measures the change in the modulated laser signal to obtain the flight time of the laser signal for distance measurement.

[0003] Existing laser ranging technologies mainly include pulsed laser ranging, phase laser ranging, frequency-modulated continuous-wave laser ranging, and polarization swept-frequency laser ranging, etc. Among them, pulsed laser ranging has a large measurement range (up to the km level), but the ranging accuracy is at the centimeter level, and it is mainly used in fields such as topographic mapping, large-scale three-dimensional scanning measurement, and obstacle avoidance measurement. Phase laser ranging has a smaller measurement range (hundred-meter level), and the measurement accuracy is at the millimeter level, and it is mainly used in fields such as building measurement and civil surveying and mapping. Frequency-modulated continuous-wave laser ranging and polarization swept-frequency laser ranging have a larger measurement range (up to 1 km) and high measurement accuracy, up to the ten-micron level, and have important applications in the fields of large-scale industrial measurement and high-end manufacturing.

[0004] Traditional pulsed laser ranging and phase laser ranging technologies are relatively mature. Restricted by factors such as measurement principles and implementation costs, it is difficult to significantly improve the measurement accuracy. Frequency-modulated continuous-wave laser ranging and polarization swept-frequency laser ranging have high measurement accuracy, but the system is complex, the implementation cost is high, and there are high requirements for the measurement application scenario, which restricts their wide application in the fields of large-scale industrial measurement and high-end manufacturing.

[0005] In recent years, the development of femtosecond laser ranging technology has provided a new implementation solution for high-precision laser ranging. Femtosecond ranging has the performance advantages of fast measurement speed and high measurement accuracy, and can replace laser interferometers. However, at present, femtosecond laser ranging systems are restricted by factors such as poor stability of femtosecond light sources and high implementation costs, and have not reached the system maturity required for practical applications. Summary of the Invention

[0006] In view of the above technical problems, the present invention provides a laser swept-frequency ranging device and method that can improve the measurement accuracy and reduce the system complexity.

[0007] On the one hand, the present invention provides a laser frequency-swept ranging device for ranging a target to be measured, including a laser, an electro-optic modulator, a beam splitter prism, a first detector, a second detector, an analog phase detector, a measurement control circuit, and a modulation frequency source, wherein: the laser is used to emit a laser signal with stable power; the electro-optic modulator is used to intensity-modulate the laser signal to output a modulation signal; the beam splitter prism divides the modulation signal into two paths, one path is received by the first detector to generate a reference signal; the other path is returned by the target to be measured and reflected by the beam splitter prism and then received by the second detector to generate a measurement signal; the analog phase detector is used to detect the phase difference between the reference signal and the measurement signal; the measurement control circuit is used to perform frequency-sweeping control on the modulation frequency source to generate a high-frequency modulation signal that changes according to a preset step size and feedback it to the electro-optic modulator, and is also used to determine two adjacent modulation frequencies by detecting the zero-phase difference signal output by the analog phase detector, and calculate the measurement distance of the target to be measured according to the two adjacent modulation frequencies.

[0008] According to an embodiment of the present invention, the laser is a high-frequency intensity-modulated laser source for emitting a continuously frequency-swept high-frequency intensity-modulated laser signal.

[0009] According to an embodiment of the present invention, the electro-optic modulator is an electro-optic intensity modulator for performing high-frequency intensity modulation on the laser signal emitted by the laser.

[0010] According to an embodiment of the present invention, the measurement control circuit calculates the measurement distance of the target to be measured according to the following formula based on the two adjacent modulation frequencies:

[0011]

[0012] wherein, L is the measurement distance of the target to be measured; c is the speed of light; f1 is the first modulation frequency among the two adjacent modulation frequencies; f2 is the second modulation frequency among the two adjacent modulation frequencies.

[0013] On the other hand, the present invention provides a laser frequency-swept ranging method using the above laser frequency-swept ranging device, including: S1, the measurement control circuit generates a preset modulation frequency control signal to control the modulation frequency source to generate a preset modulation frequency; S2, the modulation frequency source outputs the preset modulation frequency to drive the electro-optic modulator to intensity-modulate the laser signal emitted by the laser; S3, the electro-optic modulator outputs the intensity-modulated laser signal, which is divided by the beam splitter prism into a reference signal and a measurement signal, and the reference signal and the measurement signal are respectively received by the first detector and the second detector and output to the analog phase detector; S4, the analog phase detector detects the phase difference between the reference signal and the measurement signal; S5, the measurement control circuit determines two adjacent modulation frequencies by detecting the zero-phase difference signal output by the analog phase detector, and calculates the measurement distance of the target to be measured according to the two adjacent modulation frequencies.

[0014] According to an embodiment of the present invention, step S4 specifically includes: S41, the analog phase detector detects the phase difference between the reference signal and the measurement signal and outputs the voltage amplitude related to the phase difference; S42, the measurement control circuit collects the voltage amplitude and determines whether the voltage amplitude is the minimum voltage amplitude. If so, record the current modulation frequency and denote it as the specific modulation frequency; S43, the measurement control circuit continuously changes the specific modulation frequency according to a preset step length, and repeats the above steps S41 to S42 to obtain the first modulation frequency and the second modulation frequency respectively related to the minimum voltage amplitude.

[0015] According to an embodiment of the present invention, when the measurement control circuit collects the voltage amplitude, it further includes: performing normalization processing on the voltage amplitude.

[0016] According to an embodiment of the present invention, step S43 specifically includes: S431, the measurement control circuit changes the specific modulation frequency according to a preset step length. When the voltage amplitude output by the analog phase detector is the minimum voltage amplitude, record the current modulation frequency and denote it as the first modulation frequency; S432, the measurement control circuit continues to change the specific modulation frequency according to a preset step length. When the voltage amplitude output by the analog phase detector is the minimum voltage amplitude, record the current modulation frequency and denote it as the second modulation frequency.

[0017] According to an embodiment of the present invention, the measured distance of the target to be measured is calculated according to the following formula:

[0018]

[0019] where L is the measured distance of the target to be measured; c is the speed of light; f1 is the first modulation frequency; f2 is the second modulation frequency.

[0020] Compared with the prior art, the laser swept-frequency ranging device and method provided by the present invention have at least the following beneficial effects:

[0021] (1) The laser swept-frequency ranging device of the present invention has high measurement accuracy, a simple system structure, and strong measurement applicability.

[0022] (2) Compared with the traditional phase laser ranging method, the present invention can greatly increase the modulation frequency, while avoiding the high-frequency signal processing circuit, improving the measurement accuracy, and reducing the implementation cost of the phase measurement circuit.

[0023] (3) Compared with the polarization swept-frequency ranging system, the present invention does not require secondary modulation of the modulation signal, does not require a linearly polarized laser light source and polarization-maintaining optical devices, simplifies the structure of the measurement system, and reduces the implementation difficulty and implementation cost of the system.

[0024] (4) In the measurement optical path, there is no need to consider the change of the polarization state of the laser signal, and at the same time, the influence of the modulation intensity change on the phase difference measurement accuracy is avoided, expanding the application range of the entire device and method. Brief Description of the Drawings

[0025] Through the following description of the embodiments of the present invention with reference to the accompanying drawings, the above and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0026] Figure 1 Schematically shows a principle block diagram of a laser swept-frequency ranging device according to an embodiment of the present invention;

[0027] Figure 2 Schematically shows a flowchart of a laser swept-frequency ranging method according to an embodiment of the present invention;

[0028] Figure 3 Schematically shows a detection flowchart of a reference signal and a measurement signal by an analog phase discriminator according to an embodiment of the present invention;

[0029] Figure 4 Schematically shows a waveform diagram of the correspondence between the modulation frequency and the voltage amplitude output by the analog phase discriminator according to an embodiment of the present invention;

[0030] Figure 5 Schematically shows a flowchart for obtaining a first modulation frequency and a second modulation frequency according to an embodiment of the present invention.

[0031]

Description of the Reference Numerals

[0032] 1 - Laser; 2 - Electro-optic modulator; 3 - Beam splitter prism; 4 - Target to be measured; 5 - First detector; 6 - Second detector; 7 - Analog phase discriminator; 8 - Modulation frequency source; 9 - Measurement control circuit. Detailed Embodiments

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further describes the present invention in detail with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0034] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0035] In the present invention, unless otherwise clearly specified and defined, terms such as "installation", "connection", "linkage", "fixation", etc. shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection, an electrical connection, or a connection allowing mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal communication between two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0037] Currently, a phase laser ranging system intensity-modulates the emitted laser signal, and mainly measures the distance by measuring the phase difference between the emitted signal and the returned signal. To improve the ranging accuracy, it is necessary to increase the modulation signal frequency and the phase difference measurement accuracy. However, increasing the modulation signal frequency requires increasing the response bandwidth of the entire signal processing link, which will significantly increase the system cost and complexity. At the same time, the change in signal intensity has a great impact on the phase difference measurement accuracy, making it difficult to effectively improve the ranging accuracy of the ranging system.

[0038] In view of this, the present invention provides a laser frequency-sweeping ranging device and method with high measurement accuracy and a simple system structure. By performing high-frequency frequency-sweeping modulation on the intensity of the emitted laser signal, the modulation frequency at the zero-phase point of the emitted laser signal and the returned signal is measured to obtain the measured distance of the target to be measured.

[0039] Figure 1 The principle block diagram of the laser frequency-sweeping ranging device according to an embodiment of the present invention is schematically shown.

[0040] As Figure 1 shown, the laser frequency-sweeping ranging device according to an embodiment of the present invention is used to range a target to be measured 4. The device includes a laser 1, an electro-optic modulator 2, a beam splitter prism 3, a first detector 5, a second detector 6, an analog phase discriminator 7, a measurement control circuit 9, and a modulation frequency source 8. Among them, the laser 1 is used to emit a laser signal with stable power, the electro-optic modulator 2 is used to intensity-modulate the laser signal to output a modulation signal, the beam splitter prism 3 divides the modulation signal into two paths, one path is received by the first detector 5 to generate a reference signal; the other path is returned by the target to be measured 4 and reflected by the beam splitter prism 3 and then received by the second detector 6 to generate a measurement signal.

[0041] The analog phase discriminator 7 is used to detect the phase difference between the reference signal and the measurement signal.

[0042] The measurement control circuit 9 is configured to calculate the measurement distance of the target to be measured 4 based on the first modulation frequency and the second modulation frequency, and control the modulation frequency source 8 to generate a high-frequency modulation signal that varies according to a preset step size, and feedback it to the electro-optic modulator 2.

[0043] Furthermore, the laser 1 is a high-frequency intensity modulation laser source for emitting a continuously frequency-swept high-frequency intensity modulation laser signal. The electro-optic modulator 2 can be an electro-optic intensity modulator for performing high-frequency intensity modulation on the laser signal emitted by the laser 1.

[0044] It can be seen that in the embodiment of the present invention, by performing high-frequency frequency-swept modulation on the intensity of the emitted laser signal, the modulation frequency at the zero-phase point of the emitted laser signal and the returned signal is measured, and the measurement distance of the target to be measured is obtained.

[0045] Specifically, the working principle of the laser frequency-swept ranging device in this embodiment is as follows: First, the laser 1 emits a laser signal with stable power. After passing through the electro-optic modulator 2, a high-frequency intensity modulation laser signal is generated. After entering the beam splitter prism 3, it is divided into two paths. One path is received by the first detector 5 to generate a reference signal; the other path is emitted to the target to be measured 4 and then returns to the beam splitter prism 3. After being reflected by the beam splitter prism 3, it is received by the second detector 6 to generate a measurement signal. Then, the reference signal and the measurement signal enter the analog phase discriminator 7. The analog phase discriminator 7 detects the phase difference between the two signals to generate a voltage signal related to the phase difference, and then inputs it to the measurement control circuit 9. Finally, the measurement control circuit 9 controls the modulation frequency source 8 to generate a high-frequency modulation signal that varies according to a preset step size, and drives the electro-optic modulator 2 to perform intensity modulation on the laser signal.

[0046] The measurement control circuit 9 calculates the measurement distance of the target to be measured 4 based on the first modulation frequency and the second modulation frequency. Specifically, it can be calculated according to the following formula:

[0047]

[0048] In the formula, L is the measurement distance of the target to be measured; c is the speed of light; f1 is the first modulation frequency; f2 is the second modulation frequency.

[0049] Through the embodiment of the present invention, a laser with stable power is used as the measurement light source, an electro-optic intensity modulator is used as the modulation device, a continuously frequency-swept high-frequency signal is input into the electro-optic intensity modulator to perform frequency-swept intensity modulation on the emitted laser signal, a beam splitter prism is used to divide the emitted modulated laser signal into a reference signal and a measurement signal, and the distance of the target to be measured is calculated by detecting the modulation frequency at the zero-phase point of the reference signal and the measurement signal returned by the target to be measured.

[0050] Moreover, the laser swept-frequency ranging device is mainly an intensity detection component, eliminating the need for a linearly polarized laser light source and polarization-maintaining devices. In the measurement optical path, there is no need to consider the change in the polarization state of the laser signal, and at the same time, the influence of the modulation intensity change on the phase difference measurement is avoided, expanding the application scope of the entire device.

[0051] Based on the same inventive concept, on the other hand, the present invention provides a laser swept-frequency ranging method. The following specifically describes the specific operation steps of the laser swept-frequency ranging method in conjunction with Figures 2 to 5 to specifically illustrate the specific operation steps of the laser swept-frequency ranging method.

[0052] Figure 2 Schematically shows a flowchart of the laser swept-frequency ranging method according to an embodiment of the present invention.

[0053] As Figure 2 shown, the laser swept-frequency ranging method according to an embodiment of the present invention includes the following steps S1 to S5.

[0054] Step S1, the measurement control circuit generates a preset modulation frequency control signal to control the modulation frequency source to generate a preset modulation frequency.

[0055] Step S2, the modulation frequency source outputs a preset modulation frequency to drive the electro-optic modulator to perform intensity modulation on the laser signal emitted by the laser.

[0056] Step S3, the electro-optic modulator outputs the intensity-modulated laser signal, which is divided into a reference signal and a measurement signal by a beam splitter prism. The reference signal and the measurement signal are respectively received by a first detector and a second detector and output to an analog phase discriminator.

[0057] Step S4, the analog phase discriminator detects the phase difference between the reference signal and the measurement signal.

[0058] Step S5, the measurement control circuit determines two adjacent modulation frequencies by detecting the zero-phase difference signal output by the analog phase discriminator, and calculates the measurement distance of the target to be measured according to the two adjacent modulation frequencies.

[0059] Analysis shows that compared with the traditional phase laser ranging method, the method of this embodiment calculates the distance of the target to be measured by measuring the modulation frequencies of the zero-phase points of the transmitted signal and the returned signal. The measurement accuracy can be improved by increasing the modulation signal frequency, avoiding the requirements for the response bandwidth of the signal processing circuit and the influence of the light intensity change on the measurement phase difference, and simplifying the signal processing system.

[0060] Compared with the existing polarization swept-frequency ranging method, the method of this embodiment does not require secondary modulation of the modulated laser signal, avoiding the design and construction of the secondary modulation optical path structure, simplifying the measurement system and reducing the implementation difficulty. At the same time, the embodiment of the present invention performs analog modulation on the laser intensity signal. There is no need for a linearly polarized light source and polarization-maintaining devices in the system, and the measurement optical path is not affected by the change of polarization state, having a wider applicability.

[0061] Figure 3 Schematically shows the detection flow chart of the reference signal and the measurement signal by the analog phase detector according to an embodiment of the present invention.

[0062] As Figure 3 shown, the above step S4 may specifically include the following sub-steps S41 to S43.

[0063] Step S41, the analog phase detector detects the phase difference between the reference signal and the measurement signal, and outputs a voltage amplitude related to the phase difference.

[0064] Step S42, the measurement control circuit collects the voltage amplitude and determines whether the voltage amplitude is the minimum voltage amplitude. If so, records the current modulation frequency and designates it as the specific modulation frequency.

[0065] Step S43, the measurement control circuit continuously changes the specific modulation frequency according to a preset step length, and repeats the above steps S41 to S42 to obtain a first modulation frequency and a second modulation frequency respectively related to the minimum voltage amplitude.

[0066] Further, the measurement control circuit in the above step S42 collecting the voltage amplitude may further include: performing normalization processing on the voltage amplitude. The normalization processing can limit the voltage amplitude collected in real time within a certain range, such as [0, 1], so as to eliminate the adverse effects caused by singular sample data and solve the data comparability between different voltage amplitudes.

[0067] Figure 4 Schematically shows the waveform diagram of the corresponding relationship between the modulation frequency and the voltage amplitude output by the analog phase detector according to an embodiment of the present invention.

[0068] The measurement control circuit controls the modulation frequency source to output a continuously changing modulation frequency, and at the same time, real-time detects the voltage amplitude output by the analog phase detector. When the measured target is stationary, the voltage amplitude output by the analog phase detector is as Figure 4 shown, where the horizontal axis represents the modulation frequency and the vertical axis represents the voltage amplitude output by the analog phase detector, and the voltage amplitude has undergone the above normalization processing.

[0069] Figure 5 Schematically shows the flow chart for obtaining the first modulation frequency and the second modulation frequency according to an embodiment of the present invention.

[0070] As Figure 5 shown, the above step S43 may specifically include the following sub-steps S431 to S432.

[0071] In step S431, the measurement control circuit changes a specific modulation frequency according to a preset step length. When the voltage amplitude output by the analog phase discriminator is the minimum voltage amplitude, record the current modulation frequency and denote it as the first modulation frequency.

[0072] Thus, when the voltage amplitude output by the analog phase discriminator is the minimum voltage amplitude in the first cycle, the phase difference between the reference signal and the measurement signal is zero. Record the modulation frequency at this time and denote it as the first modulation frequency f1.

[0073] In step S432, the measurement control circuit continues to change the specific modulation frequency according to the preset step length. When the voltage amplitude output by the analog phase discriminator is the minimum voltage amplitude, record the current modulation frequency and denote it as the second modulation frequency.

[0074] Thus, when the voltage amplitude output by the analog phase discriminator is the minimum voltage amplitude in the second cycle immediately following the first cycle, the phase difference between the reference signal and the measurement signal is also zero. Record the modulation frequency at this time and denote it as the second modulation frequency f2.

[0075] Finally, the measured distance of the target to be measured can be calculated according to the following formula:

[0076]

[0077] In the formula, L is the measured distance of the target to be measured; c is the speed of light; f1 is the first modulation frequency; f2 is the second modulation frequency.

[0078] Thus, the embodiment of the present invention uses an analog phase discriminator to implement the detection of the zero phase point of the reference signal and the measurement signal. By detecting two adjacent zero phase points, two modulation frequency data are obtained. Substituting the two modulation frequency data into the formula, the measured distance of the target to be measured can be calculated.

[0079] It should be noted that the embodiment manners of the device part are similar to those of the method part, and the achieved technical effects are also similar. For specific details, reference can be made to the device embodiment manner part above, and details will not be repeated here.

[0080] The above is only an exemplary illustration, and the embodiments of the present invention are not limited thereto. For example, the above-described intensity modulation laser signal generation method and phase difference detection method are special cases. In other embodiments, using other intensity modulation laser signal generation methods and / or phase difference detection methods as effective implementation manners of the embodiments of the present invention should all be included in the protection scope of the present invention.

[0081] In summary, the embodiments of the present invention provide a laser frequency-swept ranging device and method. By performing high-frequency frequency-swept modulation on the intensity of the transmitted laser signal, measuring the modulation frequency at the zero-phase point of the transmitted laser signal and the returned signal, the distance to be measured of the target is obtained, with high measurement accuracy, a simple system structure, and strong measurement applicability.

[0082] Some block diagrams and / or flowcharts are shown in the drawings. It should be understood that some blocks or combinations of blocks in the block diagrams and / or flowcharts can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when executed by the processor, these instructions can create a device for implementing the functions / operations illustrated in these block diagrams and / or flowcharts.

[0083] Therefore, the technology of the present invention can be implemented in the form of hardware and / or software (including firmware, microcode, etc.). Additionally, the technology of the present invention can take the form of a computer program product on a computer-readable medium storing instructions, which can be used by or in conjunction with an instruction execution system. In the context of the present invention, a computer-readable medium can be any medium that can contain, store, transmit, propagate, or transport instructions. For example, a computer-readable medium can include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, components, or propagation media. Specific examples of computer-readable media include: magnetic storage devices, such as magnetic tapes or hard disk drives (HDDs); optical storage devices, such as compact discs (CD-ROMs); memories, such as random access memories (RAMs) or flash memories; and / or wired / wireless communication links.

[0084] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the protection scope of the present invention. The appended method claims present the elements of various steps in an exemplary order and are not intended to be limited to a specific order or hierarchy.

[0085] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "front", "rear", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. Throughout the drawings, the same elements are represented by the same or similar reference numerals. When it may cause confusion in the understanding of the present invention, conventional structures or configurations will be omitted. And the shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual sizes, proportions, and actual positional relationships.

[0086] Similarly, to streamline the present invention and assist in understanding one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together in a single embodiment, figure, or description thereof. Descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0087] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. In addition, the words "a" or "an" preceding an element do not exclude the existence of a plurality of such elements. Unless otherwise specified, the expressions "about", "approximately", "substantially", and "around" mean within 10%, preferably within 5%.

[0088] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser swept-frequency ranging device for ranging a target to be measured (4), characterized in that, It includes a laser (1), an electro-optic modulator (2), a beam splitter prism (3), a first detector (5), a second detector (6), an analog phase detector (7), a measurement control circuit (9), and a modulation frequency source (8), where: The laser (1) is a stable-power laser source for emitting a laser signal with stable power. The electro-optic modulator (2) is an intensity electro-optic modulator for performing high-frequency intensity modulation on the laser signal to output an intensity-modulated laser signal. The beam splitter prism (3) divides the intensity-modulated laser signal into two paths. One path is received by the first detector (5) to generate a reference signal; the other path is returned by the target under test (4) and reflected by the beam splitter prism (3) and then received by the second detector (6) to generate a measurement signal. The analog phase detector (7) is used to detect the phase difference between the reference signal and the measurement signal. The measurement control circuit (9) is used to perform frequency-sweeping control on the output frequency of the modulation frequency source (8) to generate a high-frequency modulation signal that changes according to a preset step size and feedback it to the electro-optic modulator (2). It is also used to determine two adjacent modulation frequencies by detecting the zero-phase difference signal output by the analog phase detector (7), and calculate the measurement distance of the target under test (4) according to the two adjacent modulation frequencies.

2. The laser swept-frequency ranging device according to claim 1, characterized in that, The measurement control circuit (9) calculates the measurement distance of the target under test (4) according to the following formula: In the formula, L is the measurement distance of the target under test; c is the speed of light; f1 is the first modulation frequency among the two adjacent modulation frequencies; f2 is the second modulation frequency among the two adjacent modulation frequencies.

3. A laser swept-frequency ranging method using the laser swept-frequency ranging device according to claim 1 or 2, characterized in that, It includes: Step S1, the measurement control circuit generates a preset modulation frequency control signal to control the modulation frequency source to generate a preset modulation frequency. Step S2, the modulation frequency source outputs a preset modulation frequency to drive the electro-optic modulator to perform intensity modulation on the laser signal emitted by the laser. Step S3, the electro-optic modulator outputs an intensity-modulated laser signal, which is divided by the beam splitter prism into a reference signal and a measurement signal. The reference signal and the measurement signal are respectively received by the first detector and the second detector and output to the analog phase detector. Step S4, the analog phase detector detects the phase difference between the reference signal and the measurement signal. Step S5, the measurement control circuit determines two adjacent modulation frequencies by detecting the zero-phase difference signal output by the analog phase detector, and calculates the measurement distance of the target under test according to the two adjacent modulation frequencies. Among them, the specific content of step S4 includes: Step S41, the analog phase detector detects the phase difference between the reference signal and the measurement signal and outputs a voltage amplitude related to the phase difference. Step S42, the measurement control circuit collects the voltage amplitude and judges whether the voltage amplitude is the minimum voltage amplitude. If so, record the current modulation frequency and denote it as a specific modulation frequency. Step S43, the measurement control circuit continuously changes the specific modulation frequency according to a preset step size, and repeats the above steps S41 to S42 to obtain a first modulation frequency and a second modulation frequency respectively related to the minimum voltage amplitude.

4. The laser swept-frequency ranging method according to claim 3, characterized in that, The measurement control circuit acquires the voltage amplitude and further includes: Performing normalization processing on the voltage amplitude.

5. The laser swept-frequency ranging method according to claim 3, characterized in that, The specific steps of step S43 include: Step S431: The measurement control circuit changes the specific modulation frequency according to the preset step length. When the voltage amplitude output by the analog phase discriminator is the minimum voltage amplitude, record the current modulation frequency and denote it as the first modulation frequency. Step S432: The measurement control circuit continues to change the specific modulation frequency according to the preset step length. When the voltage amplitude output by the analog phase discriminator is the minimum voltage amplitude, record the current modulation frequency and denote it as the second modulation frequency.

6. The laser swept-frequency ranging method according to claim 3, characterized in that, The measured distance of the target to be measured is calculated according to the following formula: In the formula, L is the measured distance of the target to be measured; c is the speed of light; f1 is the first modulation frequency among two adjacent modulation frequencies; f2 is the second modulation frequency among two adjacent modulation frequencies.

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