Dispersion interferometry ranging system that can eliminate distance ambiguity

Abstract

The present invention provides a dispersion interference ranging system that can eliminate ranging ambiguity, including a beam splitter, a dispersion unit and a spectrometer. The beam splitter divides the input optical signal into two paths, one of which is transmitted to a reference mirror through the dispersion unit. The dispersion unit makes different adjustments to the optical path of spectral components with different wavelengths in the optical signal. After receiving each spectral component, the reference mirror returns the first reflected light to the beam splitter through the dispersion unit according to the original path; the other path is transmitted to a target to be measured, and the target to be measured returns the second reflected light to the beam splitter. The first reflected light and the second reflected light interfere with each other at the beam splitter to generate interference light; the spectrometer collects the interference spectrum and processes the interference spectrum to obtain the phase of the interference spectrum; the actual distance is obtained according to the drift amount of the phase mutation point in the interference spectrum. The present invention fundamentally solves the problem of fuzzy relationship between the measured distance and the actual distance at the end point and turning point of the cycle of the waveform.

Description

Technical Field

[0001] The invention belongs to the field of distance measurement, and in particular relates to a dispersion interference distance measurement system capable of eliminating distance measurement ambiguity. Background Art

[0002] For interferometric ranging, the theoretical measurement distance can reach thousands of kilometers, and the measurement accuracy can be below the micron level. Existing interferometric ranging systems usually use Michelson interferometer structure for distance sensing. When the reference light and the sensing light meet, interference will occur. There is a linear relationship between the measured distance and the free spectral range (FSR) of the interference spectrum. The FSR of the interference spectrum decreases with the increase of the optical path difference between the two interference arms; it increases with the decrease of the optical path difference between the two interference arms. Therefore, the current measurement distance is mostly reflected based on the density of the FSR of the interference spectrum.

[0003] However, the measured distance is not the actual distance. In fact, there is a certain correspondence between the measured distance and the actual distance. The correspondence is fixed and represented by a waveform. After determining the measured distance, the actual distance corresponding to the measured distance can be found from the waveform. The horizontal axis of the waveform is the actual distance and the vertical axis is the measured distance. As the actual distance increases, the waveform of the measured distance will change periodically. The length of a cycle can be Lpp, and there is a turning point within the cycle length, such as Figure 1 As shown. In order to obtain the measured distance, two methods are usually used to demodulate the interference spectrum: the first is to use two Fourier transforms to extract the measured distance information, in which the Fourier transform spectrum (FTS) is filtered out by filtering after the first Fourier transform, and then the corresponding measured distance information is obtained by a series of operations such as inverse Fourier transform, phase unwrapping, and phase slope. Although this method can extract the measured distance information with high accuracy, when the distance difference between the two interference arms is very small, the FTS and the zero frequency are blurred due to overlap and cannot be extracted; in addition, when filtering, the type of filter will also affect the accuracy of the final measured distance solution. The second method is to use a single Fourier transform to solve the measured distance information. Although this method can easily obtain the measured distance information, it is special that at the end point and turning point of the waveform cycle, the relationship between the measured distance and the actual distance is relatively vague. Even if the measured distance is obtained by demodulation, it is difficult to accurately find the corresponding actual distance from the waveform. Summary of the invention

[0004] The present invention provides a dispersion interferometry ranging system capable of eliminating ranging ambiguity, so as to solve the problem that the relationship between the measured distance and the actual distance in the waveform diagram used to represent the relationship between the measured distance and the actual distance in the current interferometry ranging system is relatively vague at the end point and turning point of the cycle.

[0005] According to a first aspect of an embodiment of the present invention, a dispersion interferometry ranging system capable of eliminating ranging ambiguity is provided, comprising a beam splitter, a dispersion unit and a spectrometer, wherein the beam splitter splits an input optical signal into two paths, one of which is transmitted to a reference mirror through the dispersion unit, and the dispersion unit makes different adjustments to the propagation directions of spectral components with different wavelengths in the optical signal, and after receiving each spectral component, the reference mirror returns a first reflected light to the beam splitter through the dispersion unit along the original path, and the optical paths of the spectral components in the first reflected light are different; the beam splitter transmits another optical signal to a target to be measured, and the target to be measured returns a second reflected light to the beam splitter, and the first reflected light and the second reflected light interfere with each other at the beam splitter to generate interference light;

[0006] The spectrometer collects the interference spectrum of the interference light, and processes the interference spectrum to obtain the phase of the interference spectrum; and obtains the actual distance according to the drift amount of the phase mutation point in the interference spectrum.

[0007] In an optional implementation, the actual distance is obtained based on the drift amount of the phase mutation point in the interference spectrum, which can avoid the need to resolve the measured distance and then find the actual distance corresponding to the measured distance from the waveform diagram, thereby avoiding the need to find the actual distance corresponding to the resolved measured distance based on the cycle turning points and cycle end points of the waveform diagram. The waveform diagram is used to represent the relationship between the measured distance and the actual distance.

[0008] In another optional implementation, the phase mutation point includes a phase mutation lowest point and a phase mutation highest point, the phase mutation lowest point is used to locate the cycle turning point, and the drift of the phase mutation lowest point is used to characterize the change of the actual distance at the cycle turning point; the phase mutation highest point is used to locate the cycle end point, and the drift of the phase mutation highest point is used to characterize the change of the actual distance at the cycle end point.

[0009] In another optional implementation, a laser rangefinder is further included. The laser rangefinder roughly measures the distance between itself and the target to be measured to obtain a roughly measured distance. The roughly measured distance is divided by the actual distance range and rounded down to obtain an integer N. N*actual distance range is added to the obtained actual distance to obtain the distance to be measured. The actual distance range is the actual distance measurement range that can be obtained according to the drift amount of the phase mutation point in the interference spectrum.

[0010] In another optional implementation, obtaining the actual distance according to the drift amount of the phase mutation point in the interference spectrum includes:

[0011] According to the drift of the lowest point of the phase mutation in the interference spectrum, the actual distance change L is calculated according to the following formula: L = cΔw / 4nb, where c is the speed of light in a vacuum, Δw is the frequency drift corresponding to the lowest point of the phase mutation, n is the refractive index of air, and b is the chirp coefficient of the center frequency of the optical signal;

[0012] The obtained actual distance is determined according to the actual distance change and the actual distance range.

[0013] In another optional implementation, the waveform in the waveform diagram is a triangular wave, the period turning point of the triangular wave is on its central axis, the actual distance value range corresponding to the period starting point of the triangular wave to the period turning point is set to [0, -Lpp / 2], the actual distance value range corresponding to the period turning point of the triangular wave to the period ending point is set to [0, +Lpp / 2], and the actual distance range is Lpp / 2;

[0014] The coarse measurement distance is divided by (Lpp / 2) and rounded down to obtain an integer N. N*Lpp / 2 is added to the obtained actual distance to obtain the distance to be measured.

[0015] In another optional implementation, when N is an odd number, the actual distance obtained is the calculated actual distance change, and the distance to be measured can be obtained by adding N*Lpp / 2 to the calculated actual distance change;

[0016] When N is an even number, -Lpp / 2 is added to the calculated actual distance change, and the absolute value of the added result is taken as the actual distance obtained. N*Lpp / 2 plus the absolute value can obtain the distance to be measured.

[0017] In another optional implementation, the spectrometer collects the interference spectrum of the interference light, and processes the interference spectrum, and obtaining the phase of the interference spectrum includes:

[0018] The spectrometer first samples the interference light at equal intervals in wavelength to obtain a first interference spectrum, then interpolates and resamples the first interference spectrum to obtain a second interference spectrum at equal intervals in frequency, and finally performs a Fourier transform or a Hilbert transform on the second interference spectrum to obtain the phase of the interference spectrum.

[0019] In another optional implementation, the optical signal is a high repetition rate optical frequency comb.

[0020] In another optional implementation, it also includes a first collimator and a second collimator, wherein the optical signal is transmitted to the beam splitter after being collimated by the first collimator, and the interference light output by the beam splitter is transmitted to the spectrometer after being collimated by the second collimator; and the dispersion unit is a grating pair or a prism pair.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention can make the optical path of each spectral component in the first reflected light returned by the reference mirror different by adding a dispersion unit. After the corresponding spectral component interferes with the second reflected light returned by the target to be measured, the interference spectrum can show an obvious phase mutation. Compared with the method of mechanically scanning the uneven reference mirror to change the optical path of the reference light, the present invention uses a dispersion unit to change the optical path of the reference light, which is simpler. When obtaining the actual distance, the present invention does not need to first parse the measured distance and then query the waveform diagram used to represent the relationship between the measured distance and the actual distance. Instead, the actual distance is directly obtained based on the drift of the phase mutation point. The determination of the actual distance does not require the use of the corresponding relationship between it and the measured distance. Furthermore, it can avoid finding the corresponding actual distance based on the period turning point and period end point of the waveform diagram by measuring the distance, thereby fundamentally solving the problem that the relationship between the measured distance and the actual distance is relatively vague at the period end point and turning point of the waveform diagram.

[0023] 2. The present invention combines the phase mutation measurement method with the coarse distance measurement method. The coarse distance measurement method can solve the problem of cross-cycle positioning measurement that cannot be achieved by the phase mutation measurement method. The measured coarse measurement distance is divided by the actual distance range in the phase mutation measurement method, and the result is rounded down to obtain the number of complete cycles N. After N*actual distance range, the actual distance obtained in the phase mutation measurement method is added to achieve the result of cross-cycle long-distance measurement. The present invention sets the actual distance value range corresponding to the cycle starting point to the cycle turning point of the triangle wave in the waveform diagram as [0, -Lpp / 2], and the actual distance value corresponding to the cycle turning point to the cycle end point of the triangle wave is [0, -Lpp / 2]. The actual distance value range is [0, +Lpp / 2], that is, the actual distance range of the phase mutation measurement method is Lpp / 2, and the movement of the period turning point in different directions is given a positive and negative sign, so that the actual distance obtained by the phase mutation measurement method can be quickly identified. When the number of cycles N is an odd number, the actual distance change calculated by the formula is the real actual distance, and there is no need to perform additional calculation processing on the calculated actual distance change. When the number of cycles N is an even number, the absolute value of -Lpp / 2 plus the actual distance change calculated by the formula is taken as the actual distance obtained. Therefore, the distance measurement of the present invention is simpler and faster, and has higher real-time performance.

[0024] 3. The spectrometer of the present invention first samples the interference light at equal wavelength intervals to obtain a first interference spectrum, and then interpolates and resamples the first interference spectrum to obtain a second interference spectrum at equal frequency intervals, thereby improving the extraction accuracy of the spectral interference phase;

[0025] 4. The present invention adopts a high-repetition-rate optical frequency comb, which can improve the ranging resolution and ranging length, and reduce the resolution requirements for the spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a conventional waveform diagram for representing the relationship between the measured distance and the actual distance;

[0027] Figure 2 It is a schematic diagram of the structure of an embodiment of a dispersion interferometry ranging system capable of eliminating ranging ambiguity of the present invention;

[0028] Figure 3 is a waveform diagram of an embodiment of the present invention for representing the relationship between the measured distance and the actual distance;

[0029] Figure 4 It is a waveform comparison diagram under two conditions of the present invention;

[0030] Figure 5 It is a schematic diagram of the structure of another embodiment of the dispersion interferometry ranging system of the present invention that can eliminate ranging ambiguity. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0032] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0033] See also Figure 2, is a schematic diagram of an embodiment of a dispersion interferometer ranging system capable of eliminating ranging ambiguity of the present invention. The dispersion interferometer ranging system capable of eliminating ranging ambiguity may include a beam splitter, a dispersion unit and a spectrometer, wherein the beam splitter splits an input optical signal into two paths, one of which is transmitted to a reference mirror through the dispersion unit, and the dispersion unit makes different adjustments to the propagation directions of spectral components with different wavelengths in the optical signal, and after receiving each spectral component, the reference mirror returns the first reflected light to the beam splitter through the dispersion unit along the original path, and the optical paths of each spectral component in the first reflected light are different; the beam splitter transmits another optical signal to a target to be measured, and the target to be measured returns the second reflected light to the beam splitter, and the first reflected light and the second reflected light interfere with each other at the beam splitter to generate interference light; the spectrometer collects the interference spectrum of the interference light, and processes the interference spectrum to obtain the phase of the interference spectrum; the actual distance is obtained according to the drift amount of the phase mutation point in the interference spectrum.

[0034] In this embodiment, the input end of the beam splitter is used to input the optical signal, the second output end can be connected to the reference mirror through the dispersion unit, the third output end can be connected to the target to be measured, and the third output end can be connected to the spectrometer. The beam splitter divides the input optical signal into two paths, one of which is transmitted to the reference mirror as the reference light after dispersion processing, wherein the dispersion unit can be a grating pair or a prism pair. Taking the grating pair as an example, the dispersion amount τ chirp It can be expressed as:

[0035]

[0036] Where D is the grating spacing, m is the diffraction order, and λ c is the central wavelength of the light source, Δλ is the spectral bandwidth of the light source, c is the speed of light in vacuum, d is the grating constant, and i is the angle of incidence. After the optical signal is dispersed, the propagation direction of each spectral component in the optical signal changes. The reference mirror is a plane mirror, so the optical path of each spectral component from the beam splitter to the reference mirror is different. After receiving each spectral component, the reference mirror returns the first reflected light to the beam splitter, wherein each spectral component in the first reflected light is returned to the beam splitter according to the original path, so the optical path of each spectral component from the reference mirror back to the beam splitter is also different. After the first reflected light and the second reflected light are returned to the beam splitter, the corresponding spectral components in the first reflected light interfere with the second reflected light at the beam splitter to generate interference light. Since the optical paths of each spectral component in the first reflected light are different, the interference of the corresponding spectral components with the second reflected light can cause an obvious phase mutation in the interference spectrum.

[0037] The spectrometer collects the interference spectrum of the interference light and processes the interference spectrum. When obtaining the phase of the interference spectrum, the interference light can be first sampled at equal intervals in wavelength to obtain a first interference spectrum, then the first interference spectrum is interpolated and resampled to obtain a second interference spectrum with equal intervals in frequency, and finally the second interference spectrum is subjected to a Fourier transform or a Hilbert transform to obtain the phase of the interference spectrum. After obtaining the phase of the interference spectrum, the actual distance can be directly obtained according to the drift of the phase mutation point in the interference spectrum. Since the present invention directly obtains the actual distance according to the drift amount of the phase mutation point in the interference spectrum, it can avoid the need to parse out the measured distance, and then find out the actual distance corresponding to the measured distance from the waveform diagram, thereby avoiding the need to find out the actual distance corresponding to the measured distance parsed based on the period turning point and the period end point of the waveform diagram, and the waveform diagram is used to represent the relationship between the measured distance and the actual distance, thereby fundamentally solving the problem that the relationship between the measured distance and the actual distance is relatively vague at the period end point and the turning point of the waveform diagram.

[0038] The phase mutation point includes the lowest point of the phase mutation and the highest point of the phase mutation. The lowest point of the phase mutation is used to locate the period turning point, and the drift of the lowest point of the phase mutation is used to characterize the change of the actual distance at the period turning point; the highest point of the phase mutation is used to locate the period end point, and the drift of the highest point of the phase mutation is used to characterize the change of the actual distance at the period end point. For the waveform diagram used to measure the relationship between the distance and the actual distance, the horizontal axis is the actual distance, the vertical axis is the measured distance, and the corresponding waveform can be a triangular wave, which can be an isosceles triangular wave, and the period turning point is on its central axis.

[0039] It can be seen from the above embodiments that the present invention can make the optical path of each spectral component in the first reflected light returned by the reference mirror different by adding a dispersion unit. After the corresponding spectral components interfere with the second reflected light returned by the target to be measured, the interference spectrum can show an obvious phase mutation. Compared with the method of mechanically scanning the uneven reference mirror to change the optical path of the reference light, the present invention uses a dispersion unit to change the optical path of the reference light, which is simpler. When obtaining the actual distance, the present invention does not need to first parse the measured distance and then query the waveform diagram used to represent the relationship between the measured distance and the actual distance. Instead, the actual distance is directly obtained based on the drift of the phase mutation point. The determination of the actual distance does not require the use of the corresponding relationship between it and the measured distance. Furthermore, it can avoid finding the corresponding actual distance based on the period turning point and period end point of the waveform diagram by measuring the distance, thereby fundamentally solving the problem that the relationship between the measured distance and the actual distance is relatively vague at the period end point and turning point of the waveform diagram.

[0040] Although the phase mutation measurement method in the above embodiment can obtain the actual distance without the corresponding relationship between the measured distance and the actual distance, as the actual distance increases, the waveform in the waveform diagram will repeat periodically (such as Figure 1 As shown, the basic waveform in the waveform diagram is a triangular wave, and the triangular wave repeats periodically). The above-mentioned phase mutation measurement method can still accurately obtain the actual distance within a single cycle, but it is difficult to distinguish whether it is a cross-cycle distance measurement. To this end, the present invention introduces a laser rangefinder (such as a laser phase rangefinder), which roughly measures the distance between it and the target to be measured to obtain a rough measurement distance, and divides the rough measurement distance by the actual distance range in the phase mutation measurement method, rounds down, and obtains a complete number of cycles N. After N*actual distance range, plus the actual distance obtained in the phase mutation measurement method, cross-cycle long-distance measurement can be achieved. The actual distance range is the actual distance measurement range that can be obtained according to the drift amount of the phase mutation point in the interference spectrum. Among them, the distance to be measured can be obtained according to the following formula: L real =L DPI +N×L0

[0041] Among them, L real Indicates the distance to be measured, L DPI It represents the actual distance obtained in the phase mutation measurement method, N represents the number of cycles, and L0 represents the actual distance range in the phase mutation measurement method.

[0042] Among them, in the phase mutation measurement method, when obtaining the actual distance according to the drift of the lowest point of the phase mutation in the interference spectrum, the actual distance change L can be first calculated according to the following formula: L = cΔw / 4nb, where c is the speed of light in a vacuum, Δw is the frequency drift corresponding to the lowest point of the phase mutation, n is the refractive index of air, and b is the chirp coefficient of the center frequency of the optical signal; then the actual distance obtained is determined according to the actual distance change and the actual distance range. However, if Figure 1 As shown in the figure, the actual distance corresponding to the starting point of the cycle in the triangular wave is set to 0, the actual distance corresponding to the turning point of the cycle is set to Lpp / 2, and the actual distance corresponding to the end point of the cycle is set to Lpp. The actual distance range is set to Lpp. After calculating the actual distance change amount according to the drift amount at the lowest point of the phase mutation each time, it is necessary to perform addition and subtraction operations on Lpp / 2 and the actual distance change amount according to the moving direction of the actual distance. When the actual distance moves toward the end point of the cycle, the actual distance change amount is added to Lpp / 2, and when the actual distance moves toward the starting point of the cycle, the actual distance change amount is subtracted from Lpp / 2. The execution process of the addition and subtraction program is relatively complex and the execution speed is slow, so the real-time performance of the distance measurement is poor.

[0043] To this end, the present invention has made improvements to the waveform diagram, such as Figure 3 As shown, the actual distance value range corresponding to the cycle starting point to the cycle turning point of the triangular wave is set to [0, -Lpp / 2], and the actual distance value range corresponding to the cycle turning point to the cycle ending point of the triangular wave is set to [0, +Lpp / 2]. Therefore, the present invention sets the actual distance range to Lpp / 2, and assigns positive and negative signs to the movement of the cycle turning point in different directions. When the cycle turning point moves toward the cycle ending point, the corresponding actual distance at the cycle turning point is positive; when the cycle turning point moves toward the cycle starting point, the corresponding actual distance at the cycle turning point is negative. Based on this, the laser rangefinder roughly measures the distance between itself and the target to be measured to obtain a rough measured distance. The rough measured distance is divided by (Lpp / 2) and rounded down to obtain an integer N. N*Lpp / 2 plus the actual distance obtained is obtained to obtain the distance to be measured. Among them, N has two cases: odd and even. When N is an odd number, as Figure 4 As shown in (a), the actual distance obtained is the actual distance change calculated by the formula. The distance to be measured can be obtained by directly adding N*Lpp / 2 to the calculated actual distance change. When N is an even number, such as Figure 4 As shown in (b), -Lpp / 2 is added to the calculated actual distance change, and the absolute value of the added result is taken as the actual distance obtained. N*Lpp / 2 plus the absolute value can obtain the distance to be measured.

[0044] The present invention combines the phase mutation measurement method with the coarse distance measurement method. The coarse distance measurement method can solve the problem of cross-cycle positioning measurement that cannot be achieved by the phase mutation measurement method. The measured coarse measurement distance is divided by the actual distance range in the phase mutation measurement method, and the obtained result is rounded down to obtain the number of complete cycles N. After N*actual distance range, the actual distance obtained in the phase mutation measurement method is added to achieve the result of cross-cycle long-distance measurement. The present invention takes the actual distance value range corresponding to the cycle starting point to the cycle turning point of the triangular wave in the waveform diagram as [0, -Lpp / 2], and the actual distance value corresponding to the cycle turning point to the cycle end point of the triangular wave is taken as The range is [0, +Lpp / 2], that is, the actual distance range of the phase mutation measurement method is Lpp / 2, and the movement in different directions of the period turning point is given a positive and negative sign, so that the actual distance obtained in the phase mutation measurement method can be quickly identified. When the number of cycles N is an odd number, the actual distance change calculated by the formula is the real actual distance, and there is no need to perform additional calculation processing on the calculated actual distance change. When the number of cycles N is an even number, -Lpp / 2 is added to the calculated actual distance change, and the absolute value of the result after the addition is taken as the actual distance obtained. Therefore, the distance measurement of the present invention is simpler and faster, and has higher real-time performance.

[0045] In the phase mutation measurement method, the actual distance is obtained according to the drift of the highest point of the phase mutation in the interference spectrum, such as Figure 1 As shown, Lpp is used as the actual distance range in the phase mutation measurement method. Each time the actual distance change is calculated based on the drift of the highest point of the phase mutation, the actual distance change must be subtracted from Lpp to obtain the actual distance obtained in the phase mutation measurement method. It can be seen that when the highest point of the phase mutation is used to obtain the actual distance, the subtraction program execution process is relatively complex, the speed is slow, and the real-time performance of the distance measurement is poor. At this time, the laser rangefinder performs a rough measurement of the distance between it and the target to be measured to obtain a rough measurement distance, which is divided by Lpp and rounded down to obtain an integer N. N*Lpp plus the actual distance obtained can obtain the distance to be measured.

[0046] It should be noted that: when solving the problem of the fuzzy relationship between the measured distance and the actual distance at the end point of the cycle, the present invention obtains the actual distance based on the drift amount of the lowest point of the phase mutation in the interference spectrum, taking Lpp / 2 as the actual distance range, and obtains the distance to be measured based on the actual distance, the rough measurement distance and the actual distance range as a preferred implementation method; however, the present invention can also obtain the actual distance based on the drift amount of the lowest point of the phase mutation in the interference spectrum, taking Lpp / 2 as the actual distance range, and obtain the distance to be measured based on the actual distance, the rough measurement distance and the actual distance range as a preferred implementation method; it can also obtain the actual distance based on the drift amount of the highest point of the phase mutation in the interference spectrum, taking Lpp as the actual distance range, and obtain the distance to be measured based on the actual distance, the rough measurement distance and the actual distance range. For other positions of the waveform clock except the cycle turning point and the cycle end point, the existing method can also be used to first obtain the measured distance, and then find the actual distance corresponding to the measured distance from the waveform. Similarly, the rough measured distance measured by the laser rangefinder is divided by Lpp, and the smaller one is taken to obtain the cycle number N. The cycle number N*Lpp is added to the obtained actual distance to obtain the distance to be measured. Compared with the phase laser rangefinder, the beam splitter is closer to the target to be measured, and the measurement light signals provided by the phase laser rangefinder and the beam splitter are both incident on the same plane of the target to be measured.

[0047] In addition, the resolution of the interferometric ranging system is mainly determined by the spectral range of the light source. The wider the spectral range, the higher the ranging resolution. Theoretically, for an optical frequency comb with a spectral range of hundreds of nm, its ranging resolution can reach several microns. For an optical frequency comb, it appears as a series of pulses with equal time intervals in the time domain, and has a repetition frequency of tens of GHz; in the frequency domain, it appears as a series of comb tooth structures with equal frequency intervals. One pulse contains rich spectral components of tens or even hundreds of nanometers, which is an ideal light source for the present invention. The optical signal of the present invention can use a high-repetition-rate optical frequency comb. At this time, the theoretical measurement limit of the ranging system of the present invention is only limited by the line width of the optical frequency comb. For an optical frequency comb with a line width of more than ten Hz, its measurement distance can reach hundreds of kilometers. Since the repetition rate of the optical frequency comb used is very high, its corresponding L pp The measurement rate of the dispersion interferometry ranging system of the present invention is mainly limited by the refresh frame rate of the spectrometer. In practical applications, if there is a higher requirement for the measurement rate, it is only necessary to replace the spectrometer with a higher refresh rate.

[0048] See also Figure 5 FIG. 2 is a schematic diagram of the structure of another embodiment of a dispersion interferometry ranging system that can eliminate ranging ambiguity according to the present invention. Figure 5 and Figure 4 The difference between the illustrated embodiment is that it further comprises a first collimator and a second collimator, wherein the optical signal is transmitted to the beam splitter after being collimated by the first collimator, and the interference light output by the beam splitter is transmitted to the spectrometer after being collimated by the second collimator.

[0049] In one example, an optical frequency comb with a central wavelength of 1560nm, a spectral bandwidth of 100nm, and a repetition frequency of 50GHz is divided into two paths by an 80:20 beam splitter after passing through the first collimator. The low-power path is used as a reference light after being dispersed by a prism pair or a grating (1200 lines) pair, and the high-power path is used as a signal arm and directly irradiated on the target to be measured. The second reflected light of the target to be measured and the first reflected light of the reference mirror return to the original path and meet at the beam splitter, thereby generating an interference light signal. The interference light is coupled to the optical fiber through the second collimator, and the signal is collected and stored by the spectrometer.

[0050] It can be seen from the above embodiments that the present invention can make the optical path of each spectral component in the first reflected light returned by the reference mirror different by adding a dispersion unit. After the corresponding spectral components interfere with the second reflected light returned by the target to be measured, the interference spectrum can show an obvious phase mutation. Compared with the method of mechanically scanning the uneven reference mirror to change the optical path of the reference light, the present invention uses a dispersion unit to change the optical path of the reference light, which is simpler. When obtaining the actual distance, the present invention does not need to first parse the measured distance and then query the waveform diagram used to represent the relationship between the measured distance and the actual distance. Instead, the actual distance is directly obtained based on the drift of the phase mutation point. The determination of the actual distance does not require the use of the corresponding relationship between it and the measured distance. Furthermore, it can avoid finding the corresponding actual distance based on the period turning point and period end point of the waveform diagram by measuring the distance, thereby fundamentally solving the problem that the relationship between the measured distance and the actual distance is relatively vague at the period end point and turning point of the waveform diagram.

[0051] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0052] It will be appreciated that the invention is not limited to the precise construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from its scope. The scope of the invention is governed solely by the appended claims.

Claims

1. A dispersion interferometry ranging system capable of eliminating ranging ambiguity, characterized in that: It includes a beam splitter, a dispersion unit and a spectrometer, wherein the beam splitter splits an input optical signal into two paths, one of which is transmitted to a reference mirror through the dispersion unit, and the dispersion unit makes different adjustments to the propagation directions of spectral components with different wavelengths in the optical signal. After receiving each spectral component, the reference mirror returns a first reflected light to the beam splitter through the dispersion unit along the original path, and the optical paths of the spectral components in the first reflected light are different; the beam splitter transmits another optical signal to a target to be measured, and the target to be measured returns a second reflected light to the beam splitter, and the first reflected light and the second reflected light interfere with each other at the beam splitter to generate interference light; The spectrometer collects the interference spectrum of the interference light, and processes the interference spectrum to obtain the phase of the interference spectrum; the actual distance is obtained according to the drift amount of the phase mutation point in the interference spectrum; It also includes a laser rangefinder, which roughly measures the distance between the laser rangefinder and the target to be measured to obtain a roughly measured distance, the roughly measured distance is divided by the actual distance range, rounded down to obtain an integer N, N*actual distance range is added to the obtained actual distance to obtain the distance to be measured, and the actual distance range is the actual distance measurement range obtained according to the drift amount of the phase mutation point in the interference spectrum.

2. The dispersion interferometry ranging system capable of eliminating ranging ambiguity according to claim 1, characterized in that: The phase mutation point includes a phase mutation lowest point and a phase mutation highest point, the phase mutation lowest point is used to locate the cycle turning point, and the drift of the phase mutation lowest point is used to characterize the change of the actual distance at the cycle turning point; the phase mutation highest point is used to locate the cycle end point, and the drift of the phase mutation highest point is used to characterize the change of the actual distance at the cycle end point.

3. The dispersion interferometry ranging system capable of eliminating ranging ambiguity according to claim 1, characterized in that: The actual distance is obtained according to the drift of the phase mutation point in the interference spectrum: According to the drift of the lowest point of the phase mutation in the interference spectrum, the actual distance change L is calculated according to the following formula: L = cΔw / 4nb, where c is the speed of light in a vacuum, Δw is the frequency drift corresponding to the lowest point of the phase mutation, n is the refractive index of air, and b is the chirp coefficient of the center frequency of the optical signal; The obtained actual distance is determined according to the actual distance change and the actual distance range.

4. The dispersion interferometry ranging system capable of eliminating ranging ambiguity according to claim 3, characterized in that: The waveform in the waveform diagram for representing the relationship between the measured distance and the actual distance is a triangular wave, the period turning point of the triangular wave is on its central axis, the actual distance value range corresponding to the period starting point to the period turning point of the triangular wave is set to [0, -Lpp / 2], the actual distance value range corresponding to the period turning point to the period ending point of the triangular wave is set to [0, +Lpp / 2], and the actual distance range is Lpp / 2; The coarse measurement distance is divided by Lpp / 2 and rounded down to obtain an integer N. N*Lpp / 2 is added to the obtained actual distance to obtain the distance to be measured.

5. The dispersion interferometry ranging system capable of eliminating ranging ambiguity according to claim 4, characterized in that: When N is an odd number, the actual distance obtained is the calculated actual distance change, and the distance to be measured is obtained by adding N*Lpp / 2 to the calculated actual distance change; When N is an even number, -Lpp / 2 is added to the calculated actual distance change, and the absolute value of the added result is taken as the actual distance obtained. N*Lpp / 2 plus the absolute value is used to obtain the distance to be measured.

6. The dispersion interferometry ranging system capable of eliminating ranging ambiguity according to claim 1, characterized in that: The spectrometer collects the interference spectrum of the interference light, and processes the interference spectrum to obtain the phase of the interference spectrum, which includes: The spectrometer first samples the interference light at equal intervals in wavelength to obtain a first interference spectrum, then interpolates and resamples the first interference spectrum to obtain a second interference spectrum at equal intervals in frequency, and finally performs a Fourier transform or a Hilbert transform on the second interference spectrum to obtain the phase of the interference spectrum.

7. The dispersion interferometry ranging system capable of eliminating ranging ambiguity according to claim 3, characterized in that: The optical signal is an optical frequency comb with a high repetition rate.

8. The dispersion interferometry ranging system capable of eliminating ranging ambiguity according to claim 1, characterized in that: It also includes a first collimator and a second collimator, wherein the optical signal is transmitted to the beam splitter after being collimated by the first collimator, and the interference light output by the beam splitter is transmitted to the spectrometer after being collimated by the second collimator; and the dispersion unit is a grating pair or a prism pair.

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