Frequency modulated continuous wave based measurement system

Abstract

The present disclosure describes a frequency-modulated continuous wave based measurement system for measuring the position of a movable part relative to a fixed part in a motion system, the measurement system comprising: a first generating module configured to emit a frequency-modulated continuous wave laser; a light splitting module configured to split the frequency-modulated continuous wave laser into a measurement beam and a reference beam, wherein the measurement beam is directed to the movable part and reflected by the movable part to form a first optical signal, and the reference beam is directed to the fixed part and reflected by the fixed part to form a second optical signal; a beam splitting module configured to receive the first optical signal and the second optical signal combined in the light splitting module and split the first optical signal and the second optical signal into two beams; and a detection module configured to receive the two beams and obtain the position of the movable part relative to the fixed part based on the two beams. Thus, the accuracy of measuring the position of the movable part relative to the fixed part can be improved.

Description

[0001] This application is a divisional application of the patent application filed on October 29, 2024, with application number 2024115219532 and invention title "Differential Fiber Laser Ruler Based on Frequency Modulated Continuous Wave". Technical Field

[0002] This disclosure generally relates to the intelligent manufacturing equipment industry, and specifically to a measurement system based on frequency-modulated continuous wave. Background Technology

[0003] Industrial production and measuring equipment typically features a motion platform, which generally includes a base, a stage, and a drive mechanism. The drive mechanism moves the stage relative to the base in the XY plane. To ensure machining or measurement accuracy, the motion accuracy of the stage needs to be improved. Therefore, during the control of the motion platform, it is necessary to monitor the position of the stage (i.e., the position of the stage relative to the base) in real time to ensure that the motion accuracy of the stage meets the machining or measurement requirements.

[0004] Traditional methods for detecting the position of a stage typically involve mounting an encoder on the drive mechanism (e.g., a servo motor) and using the encoder's output pulses to detect the stage's position in real time. However, due to the limited precision of transmission components in the drive mechanism (e.g., lead screw drives, synchronous belt drives, or belt drives), encoders often fail to accurately determine the stage's position. In such cases, a dedicated ranging device can be added to achieve high-precision measurement of the stage's position. In existing technology, a laser ruler, independent of the motion platform, can be installed outside the motion platform, enabling real-time and continuous measurement of the stage's position.

[0005] Because the motion platform inevitably vibrates during the movement of the stage (i.e., the entire motion platform vibrates), this vibration affects the accuracy of the laser ruler in measuring the stage's position. Specifically, existing laser rulers mainly use pulse or phase methods for measurement, without a reference optical path or with the reference optical path directly located inside the main unit. The measured distance is actually the relative distance between the stage and the laser ruler, which means that errors caused by stage vibration are also included, failing to accurately reflect the stage's position relative to the base. Therefore, the accuracy of measuring the stage's position using a frequency-modulated continuous wave laser ruler needs further improvement. Summary of the Invention

[0006] This disclosure is made in view of the above-mentioned situation, and its purpose is to provide a differential fiber laser ruler based on frequency-modulated continuous laser that can improve the accuracy of measuring the position of a stage.

[0007] Therefore, the first aspect of this disclosure provides a frequency-modulated continuous wave (FMCV)-based differential fiber laser ruler for measuring the position of a movable part relative to a fixed part in a motion system having a fixed part and a movable part. The differential fiber laser ruler includes: a first generating module, a beam splitting module, a beam splitting module, and a detection module. The first generating module is configured to emit an FMCV laser. The beam splitting module is configured to split the FMCV laser into a parallel measurement beam and a reference beam. The measurement beam is guided to the movable part and reflected by the movable part to form a first optical signal, and the reference beam is guided to the fixed part and reflected by the fixed part to form a second optical signal. The beam splitting module is configured to split the combined first and second optical signals into two beams and transmit the two beams to the detection module. The detection module is configured to perform differential processing on the signals of the two beams and obtain the position of the movable part relative to the fixed part based on the differential signal.

[0008] In the first aspect of this disclosure, since both the measuring beam and the reference beam are guided to the motion system, when the motion system vibrates, the movable part and the fixed part vibrate synchronously, so that the first optical signal and the second optical signal carry the same vibration signal (i.e., the common-mode vibration signal), so that the vibration error caused by the motion system becomes the common-mode error. By performing differential processing on the signals of the two beams, the vibration signal can be easily eliminated to achieve noise reduction, thereby improving the accuracy of measuring the position of the movable part relative to the fixed part based on the differential signal.

[0009] In addition, in the differential fiber laser ruler disclosed in the first aspect of this disclosure, optionally, the detection module includes a balance detector and a processor, the balance detector is configured to perform differential processing on the signals of the two beams of light, and the processor is configured to obtain the position of the movable part relative to the fixed part based on the differential signal.

[0010] Additionally, in the differential fiber laser ruler according to the first aspect of this disclosure, optionally, an optical fiber is included, through which the frequency-modulated continuous laser is transmitted to the beam splitter. In this case, guiding the frequency-modulated continuous laser to the beam splitter via the optical fiber enables the beam splitter to be independent of the host device and away from heat sources (such as the first generating module) within the host device, thereby minimizing the impact of heat sources on the optical fiber and the beam splitter.

[0011] Furthermore, in the differential fiber laser ruler according to the first aspect of this disclosure, optionally, a collimation module is included. The frequency-modulated continuous laser is transmitted sequentially to the beam splitting module via the optical fiber and the collimation module, and the collimation module is configured to collimate the beam. In this case, when the first optical signal and the second optical signal are transmitted sequentially to the detection module via the collimation module and the optical fiber, the intensity and energy density of the first and second optical signals can be increased by the collimation module, thereby enhancing the interference effect of the first and second optical signals, and thus enhancing the intensity of the interference signal.

[0012] Furthermore, in the differential fiber laser ruler according to the first aspect of this disclosure, optionally, the beam splitting module includes a beam splitting element and a reflecting element. The beam splitting element is configured to receive the frequency-modulated continuous laser and split the frequency-modulated continuous laser into a reference beam and a measurement beam. The measurement beam is reflected by the beam splitting element and guided to the movable part. The reference beam is transmitted through the beam splitting element to the reflecting element and reflected by the reflecting element and guided to the fixed part. In this case, it is easy to split the frequency-modulated continuous laser into two uniform and parallel reference beams and a measurement beam, and the internal structure of the beam splitting module can be simplified.

[0013] Furthermore, in the differential fiber laser ruler according to the first aspect of this disclosure, optionally, the fixing part is provided with a reference object corresponding to the reference beam, and the reference object is configured to reflect the reference beam. In this case, reflecting the reference beam through the reference object can increase the intensity of the second optical signal, which is beneficial to increasing the intensity of the interference signal obtained by the detection module.

[0014] Furthermore, in the differential fiber laser ruler according to the first aspect of this disclosure, optionally, the differential fiber laser ruler has a cooperative target measurement function and / or a non-cooperative target measurement function. In response to the cooperative target measurement function, the reference object is a reflective device; in response to the non-cooperative target measurement function, the reference object is the fixed part itself. In this case, using the cooperative target measurement function of the differential fiber laser ruler, the measured information of the reflective device can be used as the information of the fixed part, and the intensity of the second optical signal can be increased through the reflective device. Additionally, using the non-cooperative target measurement function of the differential fiber laser ruler, the information of the fixed part can be directly measured.

[0015] Furthermore, in the differential fiber laser ruler according to the first aspect of this disclosure, optionally, the propagation paths of the measuring beam and the reference beam are parallel to the direction of movement of the movable part relative to the fixed part. In this case, by making the propagation paths of the measuring beam and the reference beam parallel to the direction of movement of the movable part relative to the fixed part, the detection module can directly obtain the position of the movable part relative to the fixed part in the direction of movement based on the interference signal.

[0016] The second aspect of this disclosure provides a measurement method for measuring the position of a movable part relative to a fixed part in a motion system having a fixed part and a movable part using a differential fiber laser ruler as described in the first aspect of this disclosure.

[0017] Furthermore, in the measurement method according to the second aspect of this disclosure, optionally, the movable part can move relative to the fixed part in multiple directions, and at least one differential fiber laser ruler is provided in each of the multiple directions to obtain the position of the movable part relative to the fixed part in each direction. This improves the accuracy of measuring the position of the movable part relative to the fixed part in each direction.

[0018] According to this disclosure, a differential fiber laser ruler based on frequency-modulated continuous laser can be provided, which can improve the accuracy of measuring the position of a stage. Attached Figure Description

[0019] This disclosure will now be explained in further detail by way of example only with reference to the accompanying drawings.

[0020] Figure 1 This is a schematic diagram illustrating an application scenario of the differential fiber laser ruler involved in the examples of this disclosure.

[0021] Figure 2 This is a schematic diagram illustrating the motion system involved in the example of this disclosure.

[0022] Figure 3A This is a block diagram illustrating a first embodiment of the differential fiber laser ruler according to the examples of this disclosure.

[0023] Figure 3B This is a block diagram illustrating a second embodiment of the differential fiber laser ruler according to the examples of this disclosure.

[0024] Figure 4A This is a schematic diagram illustrating the working principle of the differential fiber laser ruler according to the first embodiment of the present disclosure.

[0025] Figure 4B This is a schematic diagram illustrating the working principle of the differential fiber laser ruler according to the second embodiment of the present disclosure.

[0026] Figure 5 This is a schematic diagram showing the positional relationship between the beam splitting module and the motion system involved in the example of this disclosure.

[0027] Figure 6 This is a schematic diagram illustrating the structure of the beam splitter module involved in the example of this disclosure.

[0028] Figure 7 This is a schematic diagram illustrating multiple differential fiber laser rulers arranged in the X-axis and Y-axis directions respectively, as described in the example of this disclosure.

[0029] Explanation of reference numerals in the attached figures: 1…Differential fiber laser ruler, 10…First generating module, 11…Beam splitting module, 112…Beam splitting element, 114…Reflecting element, 12…Detection module, 13…Coupled module, 14…Beam splitting module, 15…Fiber optic cable, 16…Collimation module, 17…Second generating module, 18…Feedback module, 19…Isolator, 3…Main unit, 2…Motion system, 22…Fixed part, 24…Movable part, 240…Through hole, 26…Column, 28…Reference object, L… Frequency-modulated continuous laser, L1… Measurement beam, L10… First optical signal, L2… Reference beam, L20… Second optical signal, A1… First landing point, A2… Second landing point, d… Distance between the movable part and the fixed part. Detailed Implementation

[0030] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0031] It should be noted that the terms "first," "second," "third," and "fourth," etc., in this disclosure, claims, and the aforementioned drawings are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include steps or modules not listed, or may optionally include other steps or modules inherent to these processes, methods, products, or devices. In the following description, the same reference numerals are used for the same parts, and repeated descriptions are omitted. Additionally, the drawings are merely schematic diagrams, and the scale of the dimensions of the parts or the shape of the parts may differ from the actual figures.

[0032] The differential fiber laser ruler based on frequency-modulated continuous wave disclosed herein can guide the measurement beam to the movable part of the motion system and guide the reference beam to the fixed part of the motion system. When the motion system vibrates, the reflected light of the measurement beam (i.e., the first optical signal) and the reflected light of the reference beam (i.e., the second optical signal) carry the same vibration signal. Therefore, the vibration error caused by the motion system is a common-mode error. By differentially processing the signals of the two beams formed by the first and second optical signals, the vibration signal can be easily eliminated to achieve noise reduction, thereby improving the accuracy of measuring the position of the movable part relative to the fixed part based on the differential signal.

[0033] The frequency-modulated continuous wave-based differential fiber laser ruler disclosed herein can be simply referred to as a differential fiber laser ruler, and sometimes it can also be called a differential fiber laser interferometer, differential fiber laser measurement system, laser ruler, or interferometer, etc.

[0034] The differential fiber laser ruler involved in this disclosure will be described below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic diagram illustrating an application scenario of the differential fiber laser ruler 1 involved in the examples of this disclosure. Figure 2 This is a schematic diagram illustrating the motion system 2 involved in the example of this disclosure.

[0036] See in some examples Figure 1 The differential fiber laser ruler 1 disclosed herein can be used to measure the position of the movable part 24 relative to the fixed part 22 in a motion system 2 having a fixed part 22 and a movable part 24. The movable part 24 can move relative to the fixed part 22 (for example, the movable part 24 can move relative to the fixed part 22 in multiple directions).

[0037] In some examples, the movable part 24 can move relative to the fixed part 22 under the drive of the driving part, and the movable part 24 can vibrate synchronously with the fixed part 22 when it moves.

[0038] In some examples, the drive unit may include at least one drive mechanism. For example, the drive unit may include an X-axis drive mechanism and a Y-axis drive mechanism. The X-axis drive mechanism can drive the movable part 24 to move relative to the fixed part 22 along the X-axis direction, and the Y-axis drive mechanism can drive the movable part 24 to move relative to the fixed part 22 along the Y-axis direction.

[0039] In some examples, the fixed part 22 can refer to any part of the motion system 2 other than the movable part 24 that is not driven by the drive part.

[0040] In some examples, for the motion system 2, the division of the fixed part 22 can be based on the direction in which the driving part drives the movable part 24 to move. In other words, the fixed part 22 can be determined based on the direction of movement of the movable part 24. For example, if a structure in the motion system 2 (e.g., the first structure) moves along with the movable part 24 when the movable part 24 moves along the X-axis, then the first structure should not be assigned to the fixed part 22. As another example, if a structure in the motion system 2 (e.g., the second structure) does not move along with the movable part 24 when the movable part 24 moves along the Y-axis, then the second structure can be assigned to the fixed part 22.

[0041] See in some examples Figure 1 or Figure 2 The motion system 2 may include a column 26 extending along the Z-axis. In addition, the movable part 24 may have a through hole 240 penetrating the front and back of the movable part 24, and the column 26 may be provided so as to pass through the through hole 240.

[0042] In some examples, the post 26 can serve as the fixing part 22. See also: Figure 2 The column 26 can belong to the fixed part 22 in both the X-axis direction and the Y-axis direction.

[0043] In some examples, the motion system 2 can be a motion platform, the fixed part 22 can be a fixed part of the motion platform, and the movable part 24 can be a platform that can move relative to the fixed part of the motion platform. In some examples, the fixed part 22 may not be limited to the motion platform; for example, the fixed part 22 can be a base that is securely mounted on the motion system 2.

[0044] In some examples, the differential fiber laser ruler 1 can remain relatively stationary with respect to the fixed part 22. In some examples, the differential fiber laser ruler 1 can be set independently of the motion system 2 and remain relatively stationary with respect to the fixed part 22 (see [reference]). Figure 1 ).

[0045] It should be noted that the relative stillness between the differential fiber laser ruler 1 and the fixed part 22 can refer to the relative stillness between the two at the macroscopic level. Vibrations at the microscopic level (such as the synchronous vibration of the movable part 24 and the fixed part 22) will not disrupt the relative stillness between the differential fiber laser ruler 1 and the fixed part 22.

[0046] Figure 3A This is a block diagram illustrating a first embodiment of the differential fiber laser ruler 1 according to the examples of this disclosure. Figure 3B This is a block diagram illustrating a second embodiment of the differential fiber laser ruler 1 as described in this disclosure. Figure 4A This is a schematic diagram illustrating the working principle of the differential fiber laser ruler 1 according to the first embodiment of the present disclosure. Figure 4B This is a schematic diagram illustrating the working principle of the differential fiber laser ruler 1 of the second embodiment involved in this disclosure. Figure 5 This is a schematic diagram showing the positional relationship between the beam splitting module 11 and the motion system 2 involved in the example of this disclosure.

[0047] See in some examples Figure 3A and Figure 4A The differential fiber laser ruler 1 may include a first generating module 10 and a detection module 12. In some examples, the first generating module 10 may be configured to emit a frequency-modulated continuous laser L. In some examples, the first generating module 10 may be configured to simultaneously emit a measurement beam L1 and a reference beam L2 toward a target (e.g., motion system 2) in the form of a frequency-modulated continuous wave, and the measurement beam L1 and the reference beam L2 may be reflected back to the differential fiber laser ruler 1 by the target after being emitted to it.

[0048] In some examples, the frequency-modulated continuous laser L can be characterized as a linear frequency-modulated continuous wave. Additionally, the linear frequency-modulated continuous wave can be a sawtooth linear frequency-modulated continuous wave or a triangular linear frequency-modulated continuous wave.

[0049] In some examples, the frequency and time of a linear frequency modulated (LFM) continuous wave can have a linear relationship. In some examples, the frequency function of the LFM continuous wave can include a frequency modulation bandwidth and a frequency modulation period. The frequency modulation bandwidth can represent the range of linear frequency variation over time, and the frequency modulation period can represent the time required for the frequency to change from its initial value to its final value.

[0050] Unlike existing interferometric laser rulers, the laser ruler disclosed herein uses a frequency-modulated continuous laser L for distance measurement. The measured distance is an absolute distance, and even if the light is interrupted during the measurement process, it will not affect subsequent measurements.

[0051] In some examples, the detection module 12 can be configured to measure the target based on the measurement beam L1 and the reference beam L2 reflected by the target (e.g., measuring the distance d of the movable part 24 relative to the fixed part 22 in the motion system 2).

[0052] See in some examples Figure 3A and Figure 4A The differential fiber laser ruler 1 may include a beam splitting module 11. The beam splitting module 11 may be configured to receive the frequency-modulated continuous laser L emitted by the first generating module 10 and split the frequency-modulated continuous laser L into two frequency-modulated continuous laser L beams.

[0053] See in some examples Figure 4AThe beam splitting module 11 can be configured to split the frequency-modulated continuous laser L into a measurement beam L1 and a reference beam L2, and the measurement beam L1 and the reference beam L2 can be parallel to each other. In some examples, the measurement beam L1 and the reference beam L2 can be frequency-modulated continuous waves.

[0054] In some examples, the propagation paths of the measurement beam L1 and the reference beam L2 can be parallel to the direction of movement of the movable part 24 relative to the fixed part 22. In other words, the movable part 24 can move relative to the fixed part 22 in the direction of propagation of the measurement beam L1 and the reference beam L2. For example, in Figure 1 In the example shown, the movable part 24 moves relative to the fixed part 22 in the X-axis or Y-axis direction, and the propagation paths of the corresponding measurement beam L1 and reference beam L2 can be parallel to the X-axis or Y-axis direction.

[0055] See in some examples Figure 5 The measurement beam L1 can be guided to the movable part 24, and the measurement beam L1 reaching the movable part 24 can be reflected by the movable part 24 to form a first optical signal L10. Additionally, the reference beam L2 can be guided to the fixed part 22, and the reference beam L2 reaching the fixed part 22 can be reflected by the fixed part 22 to form a second optical signal L20. In this case, when the motion system 2 vibrates, the movable part 24 and the fixed part 22 vibrate synchronously, causing the first optical signal L10 and the second optical signal L20 to simultaneously carry the same vibration signal (i.e., a common-mode vibration signal). This transforms the vibration error caused by the motion system 2 into a common-mode error, facilitating the elimination of the vibration signal through differential processing. In some examples, the first optical signal L10 and the second optical signal L20 can be frequency-modulated continuous waves.

[0056] In some examples, the path of the measurement beam L1 can be perpendicular to the side of the movable part 24. For example, when the movable part 24 is a stage in a motion platform, the path of the measurement beam L1 can be perpendicular to the side wall of the stage.

[0057] See in some examples Figure 2 or Figure 5 The fixing part 22 may be provided with a reference object 28 corresponding to the reference beam L2, and the reference object 28 is configured to reflect the reference beam L2. That is, the reference object 28 can receive and reflect the reference beam L2 to form a second optical signal L20. In this case, the intensity of the second optical signal L20 can be increased by reflecting the reference beam L2 through the reference object 28, which is beneficial to increasing the intensity of the interference signal obtained by the detection module 12.

[0058] See in some examples Figure 2 or Figure 5The reference 28 of the fixed part 22 may be parallel to the side of the movable part 24. For example, the plane in which the reference 28 is located may be parallel to the side wall of the stage. However, this disclosure is not limited to this, and in some other examples, the reference 28 of the fixed part 22 may not be parallel to the side of the movable part 24.

[0059] In some examples, the differential fiber laser ruler 1 may have cooperative target measurement capabilities. In some examples, the cooperative target may refer to a reflective device used in conjunction with the differential fiber laser ruler 1. In some examples, the cooperative target may be located on the target to be measured. In some examples, the differential fiber laser ruler 1 having cooperative target measurement capabilities means that the differential fiber laser ruler 1 can be used in conjunction with a reflective device located on the target to measure the target.

[0060] In some examples, the differential fiber laser ruler 1 can have non-cooperative target measurement capabilities. In some examples, the non-cooperative target can refer to the target being measured itself. In some examples, the differential fiber laser ruler 1 having non-cooperative target measurement capabilities means that the differential fiber laser ruler 1 can directly measure the target being measured.

[0061] In some examples, the differential fiber laser ruler 1 can simultaneously perform cooperative target measurement and non-cooperative target measurement functions.

[0062] In some examples, in response to the cooperative target measurement function of the differential fiber laser ruler 1, the reference object 28 can be a reflective device, and a reflective device can also be provided on the side of the movable part 24. In this case, by utilizing the cooperative target measurement function of the differential fiber laser ruler 1, the information of the measured reflective device can be used as the information of the fixed part 22, and the intensity of the second optical signal L20 can be increased by the reflective device. For example, the reference object 28 can be a retroreflector or a mirror, etc.

[0063] In some examples, in response to the non-cooperative target measurement function of the differential fiber laser ruler 1, the reference object 28 can be the fixed part 22 itself. Thus, by utilizing the non-cooperative target measurement function of the differential fiber laser ruler 1, information about the fixed part 22 can be directly measured.

[0064] In some examples, the first optical signal L10 and the second optical signal L20 can be combined in the beam splitter module 11 and then transmitted to the detector module 12. For details, see [link to relevant documentation]. Figure 4A The first optical signal L10 and the second optical signal L20 can return to the beam splitting module 11 along the propagation paths of the measurement beam L1 and the reference beam L2, respectively, and can be combined in the beam splitting module 11 and transmitted to the detection module 12.

[0065] See in some examples Figure 3B and Figure 4BThe differential fiber laser ruler 1 may include a coupling module 13, which can be configured to guide the transmission of a frequency-modulated continuous laser L to the beam splitting module 11, and simultaneously guide the transmission of a first optical signal L10 and a second optical signal L20 to the detection module 12. In some examples, the coupling module 13 may be located between the first generating module 10 and the beam splitting module 11 (see [reference]). Figure 4B In some examples, coupling module 13 can be a circulator.

[0066] In some examples, the detection module 12 can be configured to obtain the position of the movable part 24 relative to the fixed part 22 based on the first optical signal L10 and the second optical signal L20. Specifically, the detection module 12 can measure the distance d of the movable part 24 relative to the fixed part 22 based on the first optical signal L10 and the second optical signal L20, thereby obtaining the position of the movable part 24 relative to the fixed part 22.

[0067] For example, by making the paths (i.e. directions) of the measurement beam L1 and the reference beam L2 parallel to the direction in which the movable part 24 moves relative to the fixed part 22, the detection module 12 can measure the distance d of the movable part 24 relative to the fixed part 22 in the direction of movement based on the first optical signal L10 and the second optical signal L20, thereby obtaining the position of the movable part 24 relative to the fixed part 22 in the direction of movement.

[0068] In some examples, the distance d between the movable part 24 and the fixed part 22 can refer to the distance of the measuring beam L1 at the first landing point A1 of the movable part 24 in the direction of propagation of the measuring beam L1 and the reference beam L2, relative to the second landing point A2 of the reference beam L2 at the fixed part 22. Figure 5 The distance d1 between the first landing point A1 and the second landing point A2 in the X-axis direction and the distance d2 between the first landing point A1 and the second landing point A2 in the Y-axis direction are schematically shown.

[0069] In some examples, the position of the movable part 24 relative to the fixed part 22 may refer to the position of the first landing point A1 relative to the second landing point A2 in the direction of propagation of the measuring beam L1 and the reference beam L2.

[0070] In some examples, the detection module 12 can be configured to acquire interference signals based on the first optical signal L10 and the second optical signal L20. Specifically, the first optical signal L10 and the second optical signal L20 can be combined in the beam splitting module 11 to form interference light, and the detection module 12 can convert the interference light into the corresponding interference signal after receiving it.

[0071] In some examples, the interference signal can carry distance information of the movable part 24 relative to the fixed part 22. Specifically, since both the first optical signal L10 and the second optical signal L20 are frequency-modulated continuous waves, the interference signal is a sine and cosine time-varying signal that varies at a fixed frequency (also known as the intermediate frequency). By measuring the intermediate frequency of the interference signal, the distance d of the movable part 24 relative to the fixed part 22 can be obtained, and this distance d is positively correlated with the intermediate frequency.

[0072] In some examples, the intermediate frequency of the interference signal and the distance d between the movable part 24 and the fixed part 22 can have a relationship as shown in formula (1): ,...Formula (1) Where f represents the intermediate frequency of the interference signal, D represents the distance between the movable part 24 and the fixed part 22, c represents the speed of light, BW represents the frequency modulation bandwidth of the frequency-modulated continuous laser L, and T represents the frequency modulation period of the frequency-modulated continuous laser L. For detailed calculations, please refer to Chinese Patent CN202311564905.7, which will not be elaborated upon here.

[0073] In some examples, the detection module 12 can be configured to obtain the position of the movable part 24 relative to the fixed part 22 based on the interference signal. Specifically, the detection module 12 can obtain the distance d of the movable part 24 relative to the fixed part 22 based on the intermediate frequency of the interference signal and formula (1), thereby obtaining the position of the movable part 24 relative to the fixed part 22.

[0074] In this disclosure, since the laser emitted by the first generating module 10 is a frequency-modulated continuous laser L, the first optical signal L10 and the second optical signal L20 are also frequency-modulated continuous laser L. In this case, it is easy to improve the ranging resolution by increasing the laser bandwidth, thereby enabling precise measurement of minute distance changes between the movable part 24 and the fixed part 22, and further improving the accuracy of measuring the position of the movable part 24 relative to the fixed part 22.

[0075] In some examples, the detection module 12 can be configured to acquire the optical path difference between the reference beam L2 and the measurement beam L1 based on the interference signal. Further, based on this optical path difference, the distance d of the movable part 24 relative to the fixed part 22 in the propagation direction of the measurement beam L1 and the reference beam L2 can be acquired, thereby acquiring the position of the movable part 24 relative to the fixed part 22 in the propagation direction of the measurement beam L1 and the reference beam L2. In this case, by making the propagation direction of the measurement beam L1 and the reference beam L2 parallel to the direction of movement of the movable part 24 relative to the fixed part 22, the detection module 12 can directly acquire the position of the movable part 24 relative to the fixed part 22 in the movement direction based on the interference signal.

[0076] In some examples, the differential fiber laser ruler 1 may include a beam splitting module 14, which may be configured to split a beam of light into two beams. In some examples, the beam splitting module 14 may be configured to split a first optical signal L10 and a second optical signal L20, which are combined in the beam splitting module 11, into two beams.

[0077] As described above, the first optical signal L10 and the second optical signal L20 can be combined in the beam splitting module 11 to form interference light. In some examples, the beam splitting module 14 can split the interference light into a first interference light and a second interference light. Specifically, the first interference light may include the first optical signal L10 and the second optical signal L20, and the second interference light may include the first optical signal L10 and the second optical signal L20.

[0078] In some examples, the two beams of light may include a first interference beam and a second interference beam.

[0079] In some examples, the beam splitter module 14 can be configured to transmit two beams of light to the detector module 12.

[0080] In some examples, the beam splitter 14 can be positioned between the detector module 12 and the coupling module 13. In this case, during the process of the coupling module 13 guiding the first optical signal L10 and the second optical signal L20 (i.e., the interference light) to the detector module 12, the beam splitter 14 can split the interference light into two beams, which facilitates differential processing by the detector module 12 after the two beams enter the detector module 12.

[0081] In some examples, beam splitting module 14 can be a beam splitter.

[0082] In some examples, the detection module 12 may have two channels, which can respectively receive the first interference light and the second interference light. In other words, the first interference light and the second interference light can be received by the two channels of the detection module 12.

[0083] In some examples, the detection module 12 can be configured to perform differential processing on the signals of the two light beams. In this case, since both the first optical signal L10 and the second optical signal L20 carry common-mode vibration signals, differential processing of the two light beams can reduce or eliminate the vibration signals to achieve noise reduction. For example, the detection module 12 can first convert the first and second interference beams into corresponding first and second electrical signals, and then perform differential operations on the two electrical signals to obtain an interference signal with a higher signal-to-noise ratio.

[0084] In some examples, the signals from the two beams of light may include a first electrical signal and a second electrical signal.

[0085] In some examples, the detection module 12 can preprocess the first and second electrical signals (e.g., amplification, filtering, etc.) before performing differential processing.

[0086] In some examples, the detection module 12 may include a balanced detector configured to perform differential processing on the signals of the two beams of light. Alternatively, the balanced detector may be configured to acquire interference signals based on the two beams of light. For example, the balanced detector can convert the first and second interference beams into corresponding first and second electrical signals, and then perform differential processing on the two electrical signals to obtain an interference signal with a higher signal-to-noise ratio.

[0087] In some examples, the detection module 12 may include a processor. The processor may be configured to acquire the position of the movable part 24 relative to the fixed part 22 based on the differential signal. In some examples, the differential signal may be an interference signal.

[0088] In some examples, the processor can be configured to obtain the position of the movable part 24 relative to the fixed part 22 based on the interference signal.

[0089] In some examples, the first generating module 10, the detection module 12, and the beam splitting module 14 described above can be integrated into a single host device 3 (see [link to host device 3]). Figure 1 ).

[0090] See in some examples Figure 3B The differential fiber laser ruler 1 may include fiber 15, which can be used to transmit frequency-modulated continuous laser L. In some examples, the frequency-modulated continuous laser L emitted by the first generating module 10 can be transmitted to the beam splitting module 11 via fiber 15 (see [link to example]). Figure 1 In this case, the frequency-modulated continuous laser L is guided to the beam splitter 11 via the optical fiber 15, so that the beam splitter 11 is independent of the host device 3 and away from the heat source (e.g., the first generating module 10) in the host device 3, thereby minimizing the impact of the heat source on the optical fiber 15 and the beam splitter 11.

[0091] In some examples, the frequency-modulated continuous laser L can be transmitted to the beam splitter 11 via fiber optic cable 15, and the first optical signal L10 and the second optical signal L20 can be transmitted to the detector 12 via fiber optic cable 15. In this case, since the measurement beam L1 and the reference beam L2 share the same optical fiber path, and the first optical signal L10 and the second optical signal L20 also share the same optical fiber path, the error caused by the temperature of fiber optic cable 15 is a common-mode error. By performing differential processing on the signals of the two beams, the influence of the temperature of fiber optic cable 15 on the measurement results can be effectively reduced. In some examples, fiber optic cable 15 can be a polarization-maintaining fiber.

[0092] Figure 6This is a schematic diagram illustrating the structure of the beam splitter module 11 involved in the example of this disclosure.

[0093] See in some examples Figure 6 The beam splitting module 11 may include a beam splitting element 112 and a reflective element 114. In some examples, the beam splitting element 112 may be configured to receive a frequency-modulated continuous laser L and split the frequency-modulated continuous laser L into a reference beam L2 and a measurement beam L1.

[0094] See in some examples Figure 6 The measurement beam L1 can be guided to the movable part 24 by reflection from the beam splitter 112. Additionally, the reference beam L2 can be transmitted through the beam splitter 112 to the reflecting element 114, and then guided to the fixed part 22 by reflection from the reflecting element 114. In this configuration, it is easy to split the frequency-modulated continuous laser L into two uniform and parallel beams, the reference beam L2 and the measurement beam L1, and the internal structure of the beam splitter module 11 can be simplified.

[0095] However, this disclosure is not limited to this. In other examples, the reference beam L2 can be guided to the fixed part 22 by reflection from the beam splitter 112. In addition, the measurement beam L1 can be transmitted to the reflector 114 after being transmitted through the beam splitter 112, and the measurement beam L1 can be guided to the movable part 24 by reflection from the reflector 114.

[0096] In some examples, the beam-splitting element 112 can be a beam splitter. Additionally, the reflecting element 114 can be a reflector.

[0097] See in some examples Figure 3B and Figure 4B The differential fiber laser ruler 1 may include a collimation module 16, which can be configured to collimate the beam. For example, the collimation module 16 can adjust the shape of the beam to a collimated shape.

[0098] In some examples, the collimation module 16 can be configured to collimate a frequency-modulated continuous laser L. In some examples, the collimation module 16 can be configured to collimate a first optical signal L10 and a second optical signal L20.

[0099] In some examples, the frequency-modulated continuous laser L emitted by the first generating module 10 can be transmitted sequentially to the beam splitting module 11 via the optical fiber 15 and the collimation module 16. In some examples, the first optical signal L10 and the second optical signal L20 can be transmitted sequentially to the detection module 12 via the collimation module 16 and the optical fiber 15 (see [reference]). Figure 4BIn this case, the collimation module 16 can increase the intensity and energy density of the first optical signal L10 and the second optical signal L20, thereby enhancing the interference effect of the first optical signal L10 and the second optical signal L20, and thus enhancing the intensity of the interference signal. In some examples, the collimation module 16 can be an optical fiber collimator.

[0100] In some examples, the beam splitting module 11 and the collimation module 16 can constitute a sensing probe. In other words, the sensing probe may include the beam splitting module 11 and the collimation module 16. In some examples, the sensing probe can be connected to the first generating module 10 via optical fiber 15.

[0101] See in some examples Figure 3B and Figure 4B The differential fiber laser ruler 1 may include a second generating module 17, which may be configured to emit an indicator beam. In some examples, the indicator beam may coincide with the frequency-modulated continuous laser L emitted by the first generating module 10. In some examples, the indicator beam may be red visible light.

[0102] In some examples, the second generating module 17 can be configured to emit an indicator beam to indicate the fixed part 22 and the movable part 24, respectively. Specifically, before using the differential fiber laser ruler 1, the indicator beam can be aligned with the movable part 24 and the fixed part 22 to confirm the first landing point A1 of the measuring beam L1 on the movable part 24 and the second landing point A2 of the reference beam L2 on the fixed part 22, respectively.

[0103] See in some examples Figure 4A or Figure 4B The second generation module 17 can be located between the coupling module 13 and the beam splitting module 11. In some examples, the second generation module 17 can be coupled between the coupling module 13 and the beam splitting module 11 via a wavelength division multiplexer.

[0104] See in some examples Figure 3B and Figure 4B The differential fiber laser ruler 1 may include a feedback module 18, which may be configured to acquire the frequency information of the frequency-modulated continuous laser L emitted by the first generating module 10.

[0105] In some examples, the feedback module 18 can feed back the frequency information of the frequency-modulated continuous laser L to the processor in the detection module 12. The processor can be configured to correct the frequency of the frequency-modulated continuous laser L emitted by the first generating module 10 based on the frequency information so that the frequency of the frequency-modulated continuous laser L changes stably (e.g., linearly).

[0106] See in some examples Figure 3B and Figure 4BThe differential fiber laser ruler 1 may include an isolator 19, which may be disposed between the first generating module 10 and the coupling module 13.

[0107] In some examples, isolator 19 can be used to couple and isolate the first generating module 10 and the optical fiber 15 (e.g., polarization-maintaining fiber). In this case, isolator 19 can reduce the possibility of reduced spectral purity of the first generating module 10, unstable modulation of the frequency-modulated continuous laser L, or unstable output power caused by the back propagation of the first optical signal L10 and the second optical signal L20. In some examples, isolator 19 can be a polarization-maintaining fiber isolator.

[0108] Figure 7 This is a schematic diagram illustrating a plurality of differential fiber laser rulers 1 respectively arranged in the X-axis and Y-axis directions as described in the example of this disclosure.

[0109] In addition, this disclosure also relates to a measurement method, which is to use the above-described differential fiber laser ruler 1 to measure the position of the movable part 24 relative to the fixed part 22 in a motion system 2 having a fixed part 22 and a movable part 24.

[0110] In some examples, the movable part 24 can move relative to the fixed part 22 in multiple directions (also referred to as measurement directions, such as the X-axis, Y-axis, and Z-axis directions). In some examples, at least one differential fiber laser ruler 1 can be provided in each of the multiple directions, and the position of the movable part 24 relative to the fixed part 22 in each direction can be obtained by using at least one differential fiber laser ruler 1 provided in each direction. This improves the accuracy of measuring the position of the movable part 24 relative to the fixed part 22 in each direction.

[0111] In some examples, positioning the differential fiber laser ruler 1 in the direction in which the movable part 24 moves relative to the fixed part 22 can indicate that the measurement beam L1 and the reference beam L2 are parallel to the direction in which the movable part 24 moves relative to the fixed part 22. For example, if the movable part 24 moves relative to the fixed part 22 in the X-axis direction, the position of the differential fiber laser ruler 1 needs to satisfy that the measurement beam L1 and the reference beam L2 are parallel to the X-axis direction.

[0112] As described above, the movable part 24 can move relative to the fixed part 22 in three-dimensional space. See also: Figure 7In response to the movable part 24 moving relative to the fixed part 22 in the X-axis direction, multiple differential fiber laser scales 1 can be arranged in the X-axis direction and along the Z-axis direction, so that multiple pairs of measurement beams L1 and reference beams L2 are distributed along the Z-axis direction and parallel to the X-axis direction. In this case, when the movable part 24 moves relative to the fixed part 22 simultaneously or sequentially in the Z-axis and X-axis directions, the position of the movable part 24 relative to the fixed part 22 can be continuously and accurately measured by the multiple differential fiber laser scales 1.

[0113] Additionally, in some examples, see Figure 7 In response to the movable part 24 moving relative to the fixed part 22 in the Y-axis direction, multiple differential fiber laser rulers 1 can be set in the Y-axis direction and the multiple differential fiber laser rulers 1 are arranged along the Z-axis direction so that multiple pairs of measurement beams L1 and reference beams L2 are distributed along the Z-axis direction and parallel to the Y-axis direction.

[0114] In some examples, the differential fiber laser ruler 1 may be installed and debugged before performing the measurement methods of this disclosure.

[0115] In some examples, mounting the differential fiber laser ruler 1 may include aligning the measurement beam L1 and the reference beam L2 parallel to the measurement direction based on the direction of movement of the movable part 24 relative to the fixed part 22 (i.e., the measurement direction). For example, if it is necessary to measure the position of the movable part 24 relative to the fixed part 22 in the X-axis direction, the orientation of the beam splitting module 11 (or the sensing probe) can be adjusted so that both the measurement beam L1 and the reference beam L2 are parallel to the X-axis direction.

[0116] In some examples, making the measurement beam L1 parallel to the measurement direction can include aligning the measurement beam L1 with the movable part 24. For example, this can be achieved by adjusting the orientation of the beam splitter module 11 (or the sensing probe) so that the measurement beam L1 is aligned with the side of the movable part 24 and the side of the movable part 24 is perpendicular to the measurement beam L1. Additionally, making the reference beam L2 parallel to the measurement direction can include aligning the reference beam L2 with the reference object 28 of the fixed part 22. In some examples, the reference object 28 and the side of the movable part 24 can be parallel.

[0117] In some examples, commissioning the differential fiber laser ruler 1 may include checking whether the installation of the differential fiber laser ruler 1 is appropriate, that is, checking whether the orientation (or attitude) of the differential fiber laser ruler 1 meets the measurement requirements.

[0118] For example, when using two differential fiber laser rulers 1 (i.e., a first differential fiber laser ruler and a second differential fiber laser ruler) for measurement, if the first differential fiber laser ruler is used to measure the position of the movable part 24 relative to the fixed part 22 in the X-axis direction, and the second differential fiber laser ruler is used to measure the position of the movable part 24 relative to the fixed part 22 in the Y-axis direction, then the measuring beam L1 and reference beam L2 of the first differential fiber laser ruler need to be parallel to the X-axis direction, and the measuring beam L1 and reference beam L2 of the second differential fiber laser ruler need to be parallel to the Y-axis direction. When the movable part 24 moves relative to the fixed part 22 in the X-axis direction, the measurement result of the second differential fiber laser ruler should remain unchanged. If this is not met, the orientation (or posture) of the second differential fiber laser ruler needs to be adjusted until the above requirements are met. Similarly, the orientation (or posture) of the first differential fiber laser ruler can be adjusted to meet the measurement requirements.

[0119] While the present disclosure has been specifically described above in conjunction with the accompanying drawings and examples, it is to be understood that the foregoing description does not limit the present disclosure in any way. Those skilled in the art can make modifications and variations to the present disclosure as needed without departing from its essential spirit and scope, and all such modifications and variations shall fall within the scope of the present disclosure.

Claims

1. A measurement system based on frequency-modulated continuous wave, used for measuring the position of a movable part relative to a fixed part in a motion system, characterized in that, The measurement system includes: a first generating module, a beam splitting module, a beam splitting module, and a detection module. The first generating module is configured to emit a frequency-modulated continuous laser. The beam splitting module is configured to split the frequency-modulated continuous laser into a measurement beam and a reference beam. The measurement beam is guided to the movable part and reflected by the movable part to form a first optical signal, and the reference beam is guided to the fixed part and reflected by the fixed part to form a second optical signal. The beam splitting module is configured to receive the first optical signal and the second optical signal combined in the beam splitting module and split the first optical signal and the second optical signal into two beams. The detection module is configured to receive the two beams and obtain the position of the movable part relative to the fixed part based on the two beams.

2. The measurement system based on frequency-modulated continuous wave according to claim 1, characterized in that, The measuring beam and the reference beam are parallel to each other.

3. The differential fiber laser ruler according to claim 1 or 2, characterized in that, The propagation paths of the measuring beam and the reference beam are parallel to the direction of movement of the movable part relative to the fixed part.

4. The measurement system based on frequency-modulated continuous wave according to claim 1, characterized in that, The detection module is configured to perform differential processing on the signals of the two beams of light to obtain the position of the movable part relative to the fixed part.

5. The measurement system based on frequency-modulated continuous wave according to claim 4, characterized in that, The detection module includes a balanced detector and a processor. The balanced detector is configured to perform differential processing on the signals of the two beams of light, and the processor is configured to obtain the position of the movable part relative to the fixed part based on the differential signal.

6. The measurement system based on frequency-modulated continuous wave according to claim 1, characterized in that, The beam splitting module includes a beam splitting element and a reflective element. The beam splitting element is configured to receive the frequency-modulated continuous laser and split the frequency-modulated continuous laser into a reference beam and a measurement beam. The measurement beam is reflected by the beam splitting element and guided to the movable part. The reference beam is transmitted through the beam splitting element and transmitted to the reflective element, and is reflected by the reflective element and guided to the fixed part.

7. The measurement system based on frequency-modulated continuous wave according to claim 1, characterized in that, It also includes a second generating module, which is configured to emit an indicator beam that can indicate the fixed part and the movable part, the propagation path of the indicator beam coinciding with the propagation path of the frequency-modulated continuous wave.

8. The measurement system based on frequency-modulated continuous wave according to claim 1, characterized in that, Includes an optical fiber, through which the frequency-modulated continuous laser is transmitted to the beam splitter.

9. The measurement system based on frequency-modulated continuous wave according to claim 1, characterized in that, The first generating module, the beam splitting module, and the detection module are integrated in the host device of the measurement system, and the beam splitting module is located close to the motion system.

10. The measurement system based on frequency-modulated continuous wave according to claim 1, characterized in that, It also includes a coupling module, which is disposed before the first generating module and the beam splitting module. The coupling module is configured to guide the frequency-modulated continuous laser to be transmitted to the beam splitting module, and simultaneously guide the first optical signal and the second optical signal to be transmitted to the detection module via the beam splitting module.

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