Frequency-modulated continuous wave based differential fiber laser ruler

Abstract

The disclosure describes a frequency-modulated continuous wave-based differential fiber laser ruler, which is a differential fiber laser ruler for measuring the position of a movable part relative to a fixed part in a motion system, and comprises a first generating module, a light splitting module, a beam splitting module and a detection module. The first generating module is configured to emit a frequency-modulated continuous wave laser. The light splitting module is configured to split the frequency-modulated continuous wave 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. 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 optical signal and second optical signal into two beams of light and transmit the two beams of light to the detection module. The detection module is configured to differentially process the signals of the two beams of light and obtain the position of the movable part relative to the fixed part based on the differentially processed signals. Thus, the accuracy of measuring the position of the movable part relative to the fixed part can be improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the intelligent manufacturing equipment industry, in particular to a differential fiber laser ruler based on frequency-modulated continuous wave. BACKGROUND

[0002] The production equipment and the measuring equipment in the industry field generally have a motion platform, which generally comprises a base, a stage and a driving mechanism, and the driving mechanism can drive the stage to move relative to the base in an X-Y plane. In order to ensure the machining accuracy or the measuring accuracy, it is necessary to improve the motion accuracy of the stage, and therefore, the position of the stage (i.e. the position of the stage relative to the base) needs to be detected in real time in the control process of the motion platform to ensure that the motion accuracy of the stage meets the machining requirements or the measuring requirements.

[0003] The conventional method for detecting the position of the stage generally installs an encoder on the driving mechanism (such as a servo motor), and the position of the stage is detected in real time through the pulses output by the encoder. However, due to the limited accuracy of the transmission components (such as a screw transmission, a synchronous belt transmission or a belt transmission) in the driving mechanism, it is difficult to accurately obtain the position of the stage through the encoder. In this case, a special distance measuring device can be additionally provided to measure the position of the stage with high accuracy. In the prior art, a laser ruler independent of the motion platform can be provided outside the motion platform, and the position of the stage can be measured in real time and continuously through the laser ruler.

[0004] Since the motion platform will inevitably vibrate (i.e. the entire motion platform will vibrate) during the movement of the stage, the vibration of the motion platform will affect the accuracy of the laser ruler in measuring the position of the stage. Specifically, the existing laser ruler mainly uses the pulse method or the phase method for measurement, and no reference light path is provided or the reference light path is directly provided in the main machine. The distance measured is actually the relative distance between the stage and the laser ruler, which leads to the error caused by the vibration of the stage being counted in, and the position of the stage relative to the base cannot be accurately reflected. Therefore, the accuracy of the laser ruler based on frequency-modulated continuous wave in measuring the position of the stage needs to be improved. SUMMARY

[0005] The present disclosure is proposed in view of the above situation, and aims to provide a differential fiber laser ruler based on frequency-modulated continuous laser, which can improve the accuracy of measuring the position of the stage.

[0006] To this end, the first aspect of the present disclosure provides a differential fiber laser ruler based on frequency-modulated continuous wave, which is used for measuring the position of a movable part relative to a fixed part in a motion system having the movable part and the fixed part, and comprises a first generating module, a light splitting module, a beam splitting module and a detection module. The first generating module is configured to emit frequency-modulated continuous wave. The light splitting module is configured to split the frequency-modulated continuous wave into a measurement beam and a reference beam which are parallel to each other. The measurement beam is guided to the movable part and reflected by the movable part to form a first optical signal. 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 first optical signal and the second optical signal combined in the light splitting module into two beams of light and transmit the two beams of light to the detection module. The detection module is configured to differentially process the signals of the two beams of light and obtain the position of the movable part relative to the fixed part based on the differentially processed signals.

[0007] In the first aspect of the present disclosure, since the measurement beam and the reference beam are both 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 simultaneously carry the same vibration signal (i.e. common-mode vibration signal), so that the vibration error caused by the motion system becomes a common-mode error. By differentially processing the signals of the two beams of light, the vibration signal can be conveniently 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 differentially processed signals.

[0008] In addition, in the differential fiber laser ruler according to the first aspect of the present disclosure, the detection module comprises a balanced detector and a processor. The balanced detector is configured to differentially process the signals of the two beams of light. The processor is configured to obtain the position of the movable part relative to the fixed part based on the differentially processed signals.

[0009] In addition, in the differential fiber laser ruler according to the first aspect of the present disclosure, an optical fiber is further included. The frequency-modulated continuous wave is transmitted to the light splitting module via the optical fiber. In this case, by guiding the frequency-modulated continuous wave to the light splitting module through the optical fiber, the light splitting module can be independent of the host device, and can be far away from the heat source (e.g. the first generating module) in the host device, thereby minimizing the influence of the heat source on the optical fiber and the light splitting module.

[0010] In addition, in the differential fiber laser ruler according to the first aspect of the present disclosure, the collimating module can be further included, and the frequency-modulated continuous wave laser is transmitted to the light splitting module in sequence via the fiber and the collimating module, and the collimating module is configured to collimate the light beam. In this case, when the first light signal and the second light signal are transmitted to the detection module in sequence via the collimating module and the fiber, the intensity and the energy density of the first light signal and the second light signal can be improved by the collimating module, so that the interference effect of the first light signal and the second light signal is enhanced, and thus the intensity of the interference signal can be enhanced.

[0011] In addition, in the differential fiber laser ruler according to the first aspect of the present disclosure, the light splitting module can include a light splitting element and a reflecting element, the light splitting element is configured to receive the frequency-modulated continuous wave laser and split the frequency-modulated continuous wave laser into the reference light beam and the measurement light beam, the measurement light beam is guided to the movable part after being reflected by the light splitting element, and the reference light beam is transmitted to the reflecting element after being transmitted by the light splitting element and is guided to the fixed part after being reflected by the reflecting element. In this case, the frequency-modulated continuous wave laser can be easily split into two uniform and parallel reference light beams and measurement light beams, and the internal structure of the light splitting module can be simplified.

[0012] In addition, in the differential fiber laser ruler according to the first aspect of the present disclosure, the fixed part can be provided with a reference object corresponding to the reference light beam, and the reference object is configured to reflect the reference light beam. In this case, the intensity of the second light signal can be improved by reflecting the reference light beam by the reference object, which is conducive to improving the intensity of the interference signal obtained by the detection module.

[0013] In addition, in the differential fiber laser ruler according to the first aspect of the present disclosure, the differential fiber laser ruler can have a cooperative target measurement function and / or a non-cooperative target measurement function, the reference object is a reflecting device in response to the differential fiber laser ruler having the cooperative target measurement function, and the reference object is the fixed part itself in response to the differential fiber laser ruler having the non-cooperative target measurement function. In this case, by using the cooperative target measurement function of the differential fiber laser ruler, the information of the measured reflecting device can be used as the information of the fixed part, and the intensity of the second light signal can be improved by the reflecting device. In addition, by using the non-cooperative target measurement function of the differential fiber laser ruler, the information of the fixed part can be directly measured.

[0014] In addition, in the differential fiber laser ruler according to the first aspect of the present disclosure, optionally, the paths in which the measurement light beam and the reference light beam propagate are parallel to the direction in which the movable part moves relative to the fixed part. In this case, by making the paths in which the measurement light beam and the reference light beam propagate parallel to the direction in which the movable part moves relative to the fixed part, the detection module can directly obtain the position of the movable part relative to the fixed part in the moving direction based on the interference signal.

[0015] The second aspect of the present disclosure provides a measurement method for measuring the position of a movable part relative to a fixed part of a motion system having the movable part and the fixed part using the differential fiber laser ruler according to the first aspect of the present disclosure.

[0016] In addition, in the measurement method according to the second aspect of the present disclosure, optionally, the movable part can move relative to the fixed part in multiple directions, and at least one differential fiber laser ruler is arranged in each of the multiple directions to obtain the position of the movable part relative to the fixed part in each direction. In this way, the accuracy of measuring the position of the movable part relative to the fixed part in each direction can be improved.

[0017] According to the present disclosure, a differential fiber laser ruler based on a frequency-modulated continuous wave laser capable of improving the accuracy of measuring the position of a stage can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0018] The present disclosure will now be explained in further detail by way of example only with reference to the accompanying drawings.

[0019] Figure 1 FIG. 1 is a schematic diagram illustrating an application scenario of a differential fiber laser ruler according to an example of the present disclosure.

[0020] Figure 2 FIG. 2 is a schematic diagram illustrating a motion system according to an example of the present disclosure.

[0021] Figure 3A FIG. 3 is a block diagram illustrating a first embodiment of a differential fiber laser ruler according to an example of the present disclosure.

[0022] Figure 3B FIG. 4 is a block diagram illustrating a second embodiment of a differential fiber laser ruler according to an example of the present disclosure.

[0023] Figure 4A FIG. 5 is a schematic diagram illustrating the working principle of the differential fiber laser ruler according to the first embodiment of the present disclosure.

[0024] Figure 4B FIG. 6 is a schematic diagram illustrating the working principle of the differential fiber laser ruler according to the second embodiment of the present disclosure.

[0025] Figure 5 is a schematic diagram showing a positional relationship between a light splitting module and a motion system according to an example of the present disclosure.

[0026] Figure 6 is a schematic diagram showing a structure of a light splitting module according to an example of the present disclosure.

[0027] Figure 7 is a schematic diagram showing a plurality of differential fiber laser scales arranged in an X-axis direction and a Y-axis direction, respectively, according to an example of the present disclosure.

[0028] BRIEF DESCRIPTION OF DRAWINGS

[0029] 1… differential fiber laser scale, 10… first generation module, 11… light splitting module, 112… light splitting element, 114… reflecting element, 12… detection module, 13… coupling module, 14… beam splitting module, 15… optical fiber, 16… collimating module, 17… second generation module, 18… feedback module, 19… isolator, 3… host device, 2… motion system, 22… fixed part, 24… movable part, 240… through hole, 26… stand, 28… reference object,

[0030] L… frequency-modulated continuous wave 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 of the movable part relative to the fixed part. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present disclosure.

[0032] It should be noted that the terms “first”, “second”, “third”, and “fourth” and the like in the specification and claims of the present disclosure and the above-described drawings are used to distinguish different objects, and are not used to describe a specific order. In addition, the terms “include” and “have” 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 can optionally include steps or modules not listed, or can optionally include other steps or modules inherent to the process, method, product, or device. In the following description, the same symbols are assigned to the same components, and repeated descriptions are omitted. In addition, the drawings are only schematic diagrams, and the proportions of the sizes of the components relative to each other or the shapes of the components can be different from the actual ones.

[0033] The frequency-modulated continuous wave based differential fiber laser ruler according to the present disclosure can guide a measurement beam to a movable part of a motion system and guide a reference beam to a fixed part of the motion system. When the motion system vibrates, the reflected light of the measurement beam (i.e., a first light signal) and the reflected light of the reference beam (i.e., a second light signal) simultaneously carry the same vibration signal. Therefore, the vibration error caused by the motion system is a common-mode error. By differentiating the signals of the two light beams formed by the first light signal and the second light signal, the vibration signal can be conveniently 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 differentiated signal.

[0034] The frequency-modulated continuous wave based differential fiber laser ruler according to the present disclosure can be simply referred to as a differential fiber laser ruler, and sometimes can also be referred to as a differential fiber laser interferometer, a differential fiber laser measurement system, a laser ruler, or an interferometer, etc.

[0035] Hereinafter, the differential fiber laser ruler according to the present disclosure will be described in conjunction with the accompanying drawings.

[0036] Figure 1 FIG. 1 is a schematic diagram illustrating an application scenario of the differential fiber laser ruler 1 according to an example of the present disclosure. Figure 2 FIG. 2 is a schematic diagram illustrating a motion system 2 according to an example of the present disclosure.

[0037] In some examples, referring to FIG. 2, Figure 1 The differential fiber laser ruler 1 according to the present disclosure can be used to measure the position of the movable part 24 relative to the fixed part 22 in the motion system 2 having the fixed part 22 and the movable part 24. The movable part 24 can move relative to the fixed part 22 (e.g., the movable part 24 can move relative to the fixed part 22 in multiple directions).

[0038] In some examples, the movable part 24 can move relative to the fixed part 22 under the driving of the driving part, and the movable part 24 can vibrate synchronously with the fixed part 22 when moving.

[0039] In some examples, the driving part can include at least one driving mechanism. For example, the driving part can include an X-axis driving mechanism and a Y-axis driving mechanism. The X-axis driving mechanism can drive the movable part 24 to move relative to the fixed part 22 along the X-axis direction, and the Y-axis driving mechanism can drive the movable part 24 to move relative to the fixed part 22 along the Y-axis direction.

[0040] In some examples, the fixed part 22 can refer to any part of the motion system 2 other than the movable part 24, which is not driven by the driving part.

[0041] 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 in which the movable part 24 moves. For example, if a certain structure (e.g., a first structure) in the motion system 2 follows the movable part 24 to move when the movable part 24 moves along the X-axis direction, the first structure should not be divided into the fixed part 22. For another example, if a certain structure (e.g., a second structure) in the motion system 2 does not follow the movable part 24 to move when the movable part 24 moves along the Y-axis direction, the second structure can be divided into the fixed part 22.

[0042] In some examples, referring to Figure 1 or Figure 2 , the motion system 2 can include a column 26 extending along the Z-axis direction. In addition, the movable part 24 can have a through hole 240 passing through the front and back surfaces of the movable part 24, and the column 26 can be arranged in a manner of passing through the through hole 240.

[0043] In some examples, the column 26 can be the fixed part 22. In some examples, referring to Figure 2 , the column 26 can belong to the fixed part 22 with respect to both the X-axis direction and the Y-axis direction.

[0044] In some examples, the motion system 2 can be a motion platform, the fixed part 22 can be a fixed part in the motion platform, and the movable part 24 can be a stage that can move relative to the fixed part in the motion platform. In some examples, the fixed part 22 can also not be limited within the motion platform, for example, the fixed part 22 can be a base stably installed on the motion system 2.

[0045] In some examples, the differential fiber laser ruler 1 can be kept relatively stationary with respect to the fixed part 22. In some examples, the differential fiber laser ruler 1 can be arranged independently of the motion system 2 and kept relatively stationary with respect to the fixed part 22 (see Figure 1 ).

[0046] It should be noted that the differential fiber laser ruler 1 kept relatively stationary with respect to the fixed part 22 can mean that the two are kept relatively stationary at a macro level, and vibration at a micro level (e.g., synchronous vibration of the movable part 24 and the fixed part 22) does not destroy the relatively stationary state between the differential fiber laser ruler 1 and the fixed part 22.

[0047] Figure 3A is a constituent block diagram illustrating a first embodiment of the differential fiber laser ruler 1 involved in the examples of the present disclosure. Figure 3B is a constituent block diagram illustrating a second embodiment of the differential fiber laser ruler 1 involved in the examples of the present disclosure. Figure 4A is a schematic diagram illustrating the working principle of the differential fiber laser ruler 1 of the first embodiment involved in the examples of the present disclosure.Figure 4B is a schematic diagram showing the working principle of the differential fiber laser ruler 1 according to the second embodiment of the present disclosure. Figure 5 is a schematic diagram showing the positional relationship between the light splitting module 11 and the motion system 2 according to the second embodiment of the present disclosure.

[0048] In some examples, referring to Figure 3A and Figure 4A , the differential fiber laser ruler 1 can include a first generation module 10 and a detection module 12. In some examples, the first generation module 10 can be configured to emit a frequency-modulated continuous wave laser L. In some examples, the first generation module 10 can be configured to simultaneously emit a measurement beam L1 and a reference beam L2 to a target (e.g., a motion system 2) in the form of a frequency-modulated continuous wave, and the measurement beam L1 and the reference beam L2 can be reflected back to the differential fiber laser ruler 1 after being emitted to the target.

[0049] In some examples, the frequency-modulated continuous wave laser L can be characterized as a linear frequency-modulated continuous wave. In addition, the linear frequency-modulated continuous wave can be a sawtooth linear frequency-modulated continuous wave or a triangular linear frequency-modulated continuous wave.

[0050] In some examples, the frequency and time of the linear frequency-modulated continuous wave can have a linear relationship. In some examples, the frequency function of the linear frequency-modulated continuous wave can include a frequency modulation bandwidth and a frequency modulation period. The frequency modulation bandwidth can represent the range of linear change of frequency with time, and the frequency modulation period can represent the time required for the frequency to change from the initial value to the final value.

[0051] Unlike existing interferometric distance measurement laser rulers, the laser ruler according to the present disclosure uses a frequency-modulated continuous wave laser L for distance measurement, and the measured distance is an absolute distance, so that even if the light is interrupted during measurement, it will not affect subsequent measurement.

[0052] In some examples, the detection module 12 can be configured to measure the target (e.g., measure the distance d of the movable part 24 relative to the fixed part 22 in the motion system 2) based on the measurement beam L1 and the reference beam L2 reflected by the target.

[0053] In some examples, referring to Figure 3A and Figure 4A , the differential fiber laser ruler 1 can include a light splitting module 11. The light splitting module 11 can be configured to receive the frequency-modulated continuous wave laser L emitted by the first generation module 10 and split the frequency-modulated continuous wave laser L into two frequency-modulated continuous wave lasers L.

[0054] In some examples, referring to Figure 4AThe light 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.

[0055] In some examples, the paths in which the measurement beam L1 and the reference beam L2 propagate can be parallel to the direction in which the movable part 24 moves relative to the fixed part 22. In other words, the movable part 24 can move relative to the fixed part 22 in the direction in which the measurement beam L1 and the reference beam L2 propagate. For example, in the example shown in FIG. 1, the movable part 24 moves relative to the fixed part 22 in the X-axis or Y-axis direction, and the paths in which the corresponding measurement beam L1 and reference beam L2 propagate can be parallel to the X-axis or Y-axis direction. Figure 1

[0056] In some examples, referring to FIG. 1, Figure 5 the measurement beam L1 can be guided to the movable part 24, and the measurement beam L1 that reaches the movable part 24 can be reflected by the movable part 24 to form a first light signal L10. In addition, the reference beam L2 can be guided to the fixed part 22, and the reference beam L2 that reaches the fixed part 22 can be reflected by the fixed part 22 to form a second light signal L20. In this case, when the motion system 2 vibrates, the movable part 24 and the fixed part 22 vibrate synchronously, so that the first light signal L10 and the second light signal L20 simultaneously carry the same vibration signal (i.e., a common-mode vibration signal), so that the vibration error caused by the motion system 2 becomes a common-mode error, thereby facilitating the elimination of the vibration signal through differential processing. In some examples, the first light signal L10 and the second light signal L20 can be frequency-modulated continuous waves.

[0057] In some examples, the path in which the measurement beam L1 propagates can be perpendicular to the side surface of the movable part 24. For example, when the movable part 24 is a stage in a motion platform, the path in which the measurement beam L1 propagates can be perpendicular to the side wall of the stage.

[0058] In some examples, referring to FIG. 1, Figure 2 or Figure 5 the fixed part 22 can 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 the reference beam L2 and reflect the reference beam L2 to form the second light signal L20. In this case, reflecting the reference beam L2 by the reference object 28 can improve the intensity of the second light signal L20, which is conducive to improving the intensity of the interference signal obtained by the detection module 12.

[0059] In some examples, referring to FIG. 1, Figure 2 or Figure 5 ​In some examples, the reference 28 of the fixed part 22 can be parallel to the side surface of the movable part 24. For example, the plane in which the reference 28 is located can be parallel to the side wall of the object table. However, the present disclosure is not limited thereto, and in other examples, the reference 28 of the fixed part 22 can also be non-parallel to the side surface of the movable part 24.

[0060] In some examples, the differential fiber laser ruler 1 can have a cooperative target measurement function. In some examples, the cooperative target can refer to a reflecting device used in conjunction with the differential fiber laser ruler 1. In some examples, the cooperative target can be arranged on the target to be measured. In some examples, the differential fiber laser ruler 1 having the cooperative target measurement function means that the differential fiber laser ruler 1 can be used in conjunction with the reflecting device arranged on the target to be measured to measure the target to be measured.

[0061] In some examples, the differential fiber laser ruler 1 can have a non-cooperative target measurement function. In some examples, the non-cooperative target can refer to the target to be measured itself. In some examples, the differential fiber laser ruler 1 having the non-cooperative target measurement function means that the differential fiber laser ruler 1 can directly measure the target to be measured.

[0062] In some examples, the differential fiber laser ruler 1 can have both the cooperative target measurement function and the non-cooperative target measurement function.

[0063] In some examples, in response to the differential fiber laser ruler 1 having the cooperative target measurement function, the reference 28 can be a reflecting device, and the side surface of the movable part 24 can also be provided with a reflecting device. In this case, by using the cooperative target measurement function of the differential fiber laser ruler 1, the information of the measured reflecting device can be taken as the information of the fixed part 22, and the intensity of the second light signal L20 can be improved through the reflecting device. For example, the reference 28 can be a retroreflector or a mirror, etc.

[0064] In some examples, in response to the differential fiber laser ruler 1 having the non-cooperative target measurement function, the reference 28 can be the fixed part 22 itself. Thus, by using the non-cooperative target measurement function of the differential fiber laser ruler 1, the information of the fixed part 22 can be directly measured.

[0065] In some examples, the first light signal L10 and the second light signal L20 can be combined in the light splitting module 11 and then transmitted to the detection module 12. Specifically, referring to Figure 4A , the first light signal L10 and the second light signal L20 can return to the light splitting module 11 along the paths in which the measurement light beam L1 and the reference light beam L2 propagate, respectively, and can be combined in the light splitting module 11 and then transmitted to the detection module 12.

[0066] In some examples, referring to Figure 3B and Figure 4BThe differential fiber laser ruler 1 can include a coupling module 13, which can be configured to guide the frequency-modulated continuous wave laser L to the splitting module 11, and simultaneously guide the first light signal L10 and the second light signal L20 to the detection module 12. In some examples, the coupling module 13 can be disposed between the first generation module 10 and the splitting module 11 (see FIG. 1). Figure 4B In some examples, the coupling module 13 can be a circulator.

[0067] 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 light signal L10 and the second light 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 light signal L10 and the second light signal L20, thereby obtaining the position of the movable part 24 relative to the fixed part 22.

[0068] For example, when the paths (i.e., directions) of the measurement light beam L1 and the reference light beam L2 are 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 moving direction based on the first light signal L10 and the second light signal L20, thereby obtaining the position of the movable part 24 relative to the fixed part 22 in the moving direction.

[0069] In some examples, the distance d of the movable part 24 relative to the fixed part 22 can refer to the distance of the first landing point A1 of the measurement light beam L1 relative to the second landing point A2 of the reference light beam L2 in the direction in which the measurement light beam L1 and the reference light beam L2 propagate. Figure 5 The distance d1 of the first landing point A1 relative to the second landing point A2 in the X-axis direction and the distance d2 of the first landing point A1 relative to the second landing point A2 in the Y-axis direction are schematically shown.

[0070] In some examples, the position of the movable part 24 relative to the fixed part 22 can refer to the position of the first landing point A1 relative to the second landing point A2 in the direction in which the measurement light beam L1 and the reference light beam L2 propagate.

[0071] In some examples, the detection module 12 can be configured to obtain an interference signal based on the first light signal L10 and the second light signal L20. Specifically, the first light signal L10 and the second light signal L20 can form interference light after being combined in the splitting module 11, and the detection module 12 can convert the interference light into a corresponding interference signal after receiving the interference light.

[0072] In some examples, the interference signal can carry distance information of the movable part 24 relative to the fixed part 22. Specifically, since the first light signal L10 and the second light signal L20 are both frequency-modulated continuous waves, the interference signal is a positive-sine time-varying signal that varies at a fixed frequency (also referred to as intermediate frequency frequency). By measuring the intermediate frequency frequency of the interference signal, the distance d of the movable part 24 relative to the fixed part 22 can be obtained, and the distance d is positively correlated with the intermediate frequency frequency.

[0073] In some examples, the intermediate frequency frequency of the interference signal and the distance d of the movable part 24 relative to the fixed part 22 can have a relationship as formula (1):

[0074]

[0075] wherein f represents the intermediate frequency frequency of the interference signal, D represents the distance of the movable part 24 relative to 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. The specific calculation content can be referred to in Chinese patent CN202311564905.7, which will not be described here.

[0076] 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 frequency of the interference signal and formula (1), so as to obtain the position of the movable part 24 relative to the fixed part 22.

[0077] In the present disclosure, since the laser emitted by the first generation module 10 is a frequency-modulated continuous laser L, the first light signal L10 and the second light signal L20 are also frequency-modulated continuous lasers L. In this case, it is easy to increase the resolution of the distance measurement by increasing the bandwidth of the laser, so as to accurately measure the small distance change between the movable part 24 and the fixed part 22, and further improve the accuracy of measuring the position of the movable part 24 relative to the fixed part 22.

[0078] In some examples, the detection module 12 can be configured to obtain the optical path difference between the reference light beam L2 and the measurement light beam L1 based on the interference signal, and further obtain the distance d of the movable part 24 relative to the fixed part 22 in the direction in which the measurement light beam L1 and the reference light beam L2 propagate based on the optical path difference, so as to obtain the position of the movable part 24 relative to the fixed part 22 in the direction in which the measurement light beam L1 and the reference light beam L2 propagate. In this case, by allowing the direction in which the measurement light beam L1 and the reference light beam L2 propagate to be parallel to the direction in which the movable part 24 moves relative to the fixed part 22, the detection module 12 can directly obtain the position of the movable part 24 relative to the fixed part 22 in the moving direction based on the interference signal.

[0079] In some examples, the differential fiber laser ruler 1 can include a beam splitting module 14, which can be configured to split one beam of light into two beams of light. In some examples, the beam splitting module 14 can be configured to split the first light signal L10 and the second light signal L20 combined in the beam splitting module 11 into two beams of light.

[0080] As described above, the first light signal L10 and the second light signal L20 can form interference light after being combined in the beam splitting module 11. In some examples, the beam splitting module 14 can split the interference light into first interference light and second interference light. Specifically, the first interference light can include the first light signal L10 and the second light signal L20, and the second interference light can include the first light signal L10 and the second light signal L20.

[0081] In some examples, the two beams of light can include the first interference light and the second interference light.

[0082] In some examples, the beam splitting module 14 can be configured to transmit the two beams of light to the detection module 12.

[0083] In some examples, the beam splitting module 14 can be disposed between the detection module 12 and the coupling module 13. In this case, during the process of guiding the first light signal L10 and the second light signal L20 (i.e., the interference light) to the detection module 12 by the coupling module 13, the interference light can be split into two beams of light by the beam splitting module 14, and after the two beams of light enter the detection module 12, the detection module 12 can facilitate differential processing.

[0084] In some examples, the beam splitting module 14 can be a beam splitter.

[0085] In some examples, the detection module 12 can have two channels, and the two channels of the detection module 12 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.

[0086] In some examples, the detection module 12 can be configured to perform differential processing on the signals of the two beams of light. In this case, since the first light signal L10 and the second light signal L20 both carry common-mode vibration signals, differential processing of the two beams of light can reduce or eliminate the vibration signals to achieve noise reduction. For example, the detection module 12 can first convert the first interference light and the second interference light into corresponding first electrical signals and second electrical signals, and then perform differential operation on the two electrical signals to obtain an interference signal with higher signal-to-noise ratio.

[0087] In some examples, the signals of the two beams of light can include the first electrical signal and the second electrical signal.

[0088] In some examples, the probe module 12 can first pre-process (e.g. amplify, filter, etc.) the first electrical signal and the second electrical signal before performing the differential processing.

[0089] In some examples, the probe module 12 can include a balanced detector, which can be configured to perform the differential processing on the signals of the two beams of light. In addition, the balanced detector can also be configured to obtain the interference signal based on the two beams of light. For example, the balanced detector can convert the first interference light and the second interference light into corresponding first electrical signal and second electrical signal, and then perform the differential operation on the two electrical signals, thereby obtaining the interference signal with higher signal-to-noise ratio.

[0090] In some examples, the probe module 12 can include a processor. The processor can be configured to obtain the position of the movable part 24 relative to the fixed part 22 based on the differential signal. In some examples, the differential signal can be the interference signal.

[0091] 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.

[0092] In some examples, the above-mentioned first generation module 10, the probe module 12 and the beam splitting module 14 can be integrated in a host device 3 (see Figure 1 ).

[0093] In some examples, referring to Figure 3B , the differential fiber laser ruler 1 can include an optical fiber 15, which can be used to transmit the frequency-modulated continuous wave laser L. In some examples, the frequency-modulated continuous wave laser L emitted by the first generation module 10 can be transmitted to the beam splitting module 11 via the optical fiber 15 (see Figure 1 ). In this case, the frequency-modulated continuous wave laser L is guided to the beam splitting module 11 through the optical fiber 15, so that the beam splitting module 11 is independent of the host device 3, and is far away from the heat source (e.g. the first generation module 10) in the host device 3, thereby minimizing the influence of the heat source on the optical fiber 15 and the beam splitting module 11.

[0094] In some examples, the frequency-modulated continuous wave laser L can be transmitted to the beam splitting module 11 via the optical fiber 15, and the first optical signal L10 and the second optical signal L20 can be transmitted to the probe module 12 via the optical fiber 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 the optical fiber 15 is a common-mode error, and by performing the differential processing on the signals of the two beams of light, the influence of the temperature of the optical fiber 15 on the measurement result can be effectively reduced. In some examples, the optical fiber 15 can be a polarization maintaining optical fiber.

[0095] Figure 6is a structural schematic diagram showing the light splitting module 11 involved in the example of the present disclosure.

[0096] In some examples, referring to Figure 6 , the light splitting module 11 can include a light splitting element 112 and a reflecting element 114. In some examples, the light splitting element 112 can be configured to receive the frequency-modulated continuous wave laser L and split the frequency-modulated continuous wave laser L into a reference light beam L2 and a measurement light beam L1.

[0097] In some examples, referring to Figure 6 , the measurement light beam L1 can be reflected by the light splitting element 112 and guided to the movable part 24. In addition, the reference light beam L2 can be transmitted to the reflecting element 114 after being transmitted through the light splitting element 112, and the reference light beam L2 can be reflected by the reflecting element 114 and guided to the fixed part 22. In this case, it is easy to split the frequency-modulated continuous wave laser L into two beams of uniform and mutually parallel reference light beam L2 and measurement light beam L1, and the internal structure of the light splitting module 11 can be simplified.

[0098] However, the present disclosure is not limited thereto, and in other examples, the reference light beam L2 can be reflected by the light splitting element 112 and guided to the fixed part 22. In addition, the measurement light beam L1 can be transmitted to the reflecting element 114 after being transmitted through the light splitting element 112, and the measurement light beam L1 can be reflected by the reflecting element 114 and guided to the movable part 24.

[0099] In some examples, the light splitting element 112 can be a beam splitter. In addition, the reflecting element 114 can be a mirror.

[0100] In some examples, referring to Figure 3B and Figure 4B , the differential fiber laser ruler 1 can include a collimation module 16, which can be configured to collimate the light beams. For example, the collimation module 16 can adjust the shape of the light beams to a collimated shape.

[0101] In some examples, the collimation module 16 can be configured to collimate the frequency-modulated continuous wave laser L. In some examples, the collimation module 16 can be configured to collimate the first optical signal L10 and the second optical signal L20.

[0102] In some examples, the frequency-modulated continuous wave laser L emitted by the first generation module 10 can be transmitted to the light splitting module 11 in sequence 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 to the detection module 12 in sequence via the collimation module 16 and the optical fiber 15 (see Figure 4BIn this case, the intensity and energy density of the first light signal L10 and the second light signal L20 can be improved by the collimation module 16, so as to enhance the interference effect of the first light signal L10 and the second light signal L20, thereby enhancing the intensity of the interference signal. In some examples, the collimation module 16 can be a fiber collimator.

[0103] In some examples, the light splitting module 11 and the collimation module 16 can constitute a sensing probe. In other words, the sensing probe can include the light splitting module 11 and the collimation module 16. In some examples, the sensing probe can be connected to the first generation module 10 through the optical fiber 15.

[0104] In some examples, referring to Figure 3B and Figure 4B , the differential fiber laser ruler 1 can include a second generation module 17, which can be configured to emit an indication light beam. In some examples, the indication light beam can coincide with the frequency-modulated continuous wave laser L emitted by the first generation module 10. In some examples, the indication light beam can be a red visible light.

[0105] In some examples, the second generation module 17 can be configured to emit an indication light beam to indicate the movable part 24 and the fixed part 22, respectively. Specifically, before using the differential fiber laser ruler 1, the movable part 24 and the fixed part 22 can be aligned by the indication light beam, so as to respectively confirm the first landing point A1 of the measurement light beam L1 on the movable part 24 and the second landing point A2 of the reference light beam L2 on the fixed part 22.

[0106] In some examples, referring to Figure 4A or Figure 4B , the second generation module 17 can be disposed between the coupling module 13 and the light splitting module 11. In some examples, the second generation module 17 can be coupled between the coupling module 13 and the light splitting module 11 by a wavelength division multiplexer.

[0107] In some examples, referring to Figure 3B and Figure 4B , the differential fiber laser ruler 1 can include a feedback module 18, which can be configured to obtain frequency information of the frequency-modulated continuous wave laser L emitted by the first generation module 10.

[0108] In some examples, the feedback module 18 can feed back the frequency information of the frequency-modulated continuous wave laser L to a processor in the detection module 12, which can be configured to correct the frequency of the frequency-modulated continuous wave laser L emitted by the first generation module 10 based on the frequency information so as to make the frequency of the frequency-modulated continuous wave laser L change stably (e.g., linearly).

[0109] In some examples, referring to Figure 3B and Figure 4BThe differential fiber laser ruler 1 can include an isolator 19, which can be disposed between the first generation module 10 and the coupling module 13.

[0110] In some examples, the isolator 19 can be used to couple isolate the first generation module 10 and the fiber 15 (e.g., polarization maintaining fiber). In this case, the situation that the spectral purity of the first generation module 10 is reduced due to the backward propagation of the first light signal L10 and the second light signal L20, or the frequency modulation continuous wave laser L modulation is unstable or the output power is unstable, etc. can be reduced by the isolator 19. In some examples, the isolator 19 can be a polarization maintaining fiber isolator.

[0111] Figure 7 FIG. 4 is a schematic diagram illustrating an example of the differential fiber laser ruler 1 according to the present disclosure.

[0112] In addition, the present disclosure also relates to a measurement method, which is a method for measuring the position of the movable part 24 relative to the fixed part 22 in the motion system 2 having the fixed part 22 and the movable part 24 using the differential fiber laser ruler 1 described above.

[0113] 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 direction, the Y-axis direction, and the Z-axis direction). In some examples, at least one differential fiber laser ruler 1 can be disposed 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 the at least one differential fiber laser ruler 1 disposed in each direction. In this way, the accuracy of measuring the position of the movable part 24 relative to the fixed part 22 in each direction can be improved.

[0114] In some examples, the differential fiber laser ruler 1 disposed in the direction in which the movable part 24 moves relative to the fixed part 22 can mean 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.

[0115] As described above, the movable part 24 can move relative to the fixed part 22 in a three-dimensional space. In some examples, referring to FIG. 4, the differential fiber laser ruler 1 can be disposed in the X-axis direction and the Y-axis direction. Figure 7In response to the movable part 24 moving relative to the fixed part 22 in the X-axis direction, a plurality of differential fiber laser scales 1 can be arranged in the X-axis direction and along the Z-axis direction, so that the pairs of measurement light beams L1 and reference light 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 in the Z-axis direction and the X-axis direction simultaneously or sequentially, the position of the movable part 24 relative to the fixed part 22 can be continuously and accurately measured by the plurality of differential fiber laser scales 1.

[0116] In addition, in some examples, referring to Figure 7 In response to the movable part 24 moving relative to the fixed part 22 in the Y-axis direction, a plurality of differential fiber laser scales 1 can be arranged in the Y-axis direction and along the Z-axis direction, so that the pairs of measurement light beams L1 and reference light beams L2 are distributed along the Z-axis direction and parallel to the Y-axis direction.

[0117] In some examples, before performing the measurement method of the present disclosure, the differential fiber laser scale 1 can be installed and debugged.

[0118] In some examples, installing the differential fiber laser scale 1 can include making the measurement light beam L1 and the reference light beam L2 parallel to the measurement direction based on the direction in which the movable part 24 moves 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 measurement light beam L1 and the reference light beam L2 can be made parallel to the X-axis direction by adjusting the orientation of the light splitting module 11 (or the sensing probe).

[0119] In some examples, making the measurement light beam L1 parallel to the measurement direction can include aligning the measurement light beam L1 with the movable part 24. For example, by adjusting the orientation of the light splitting module 11 (or the sensing probe) so that the measurement light 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 light beam L1. In addition, making the reference light beam L2 parallel to the measurement direction can include aligning the reference light 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.

[0120] In some examples, debugging the differential fiber laser scale 1 can include checking whether the installation of the differential fiber laser scale 1 is appropriate, i.e., checking whether the orientation (or attitude) of the differential fiber laser scale 1 meets the measurement requirements.

[0121] For example, if two differential fiber laser scales 1 (i.e., a first differential fiber laser scale and a second differential fiber laser scale) are used for measurement, and the first differential fiber laser scale 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 scale is used to measure the position of the movable part 24 relative to the fixed part 22 in the Y-axis direction, then the measurement beam L1 and the reference beam L2 of the first differential fiber laser scale need to be parallel to the X-axis direction, and the measurement beam L1 and the reference beam L2 of the second differential fiber laser scale 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 scale should remain unchanged. If not, the orientation (or attitude) of the second differential fiber laser scale needs to be adjusted until the above requirements are met. Similarly, the orientation (or attitude) of the first differential fiber laser scale can be adjusted to meet the measurement requirements.

[0122] Although the present disclosure has been specifically described in connection with the accompanying drawings and examples, it will be understood that the above description is not in any way limiting to the present disclosure. Those skilled in the art can make modifications and changes to the present disclosure as needed without departing from the spirit and scope of the present disclosure, and such modifications and changes are all within the scope of the present disclosure.

Claims

1. A differential fiber laser ruler based on frequency-modulated continuous wave, used for measuring the position of the movable part relative to the fixed part in a motion system having a fixed part and a movable part, characterized in that, The differential fiber laser ruler comprises a first generating module, a light splitting module, a beam splitting module and a detection module, the first generating module is configured to emit a frequency-modulated continuous wave (FMCW), the light splitting module is configured to split the FMCW into a measurement beam and a reference beam which are parallel to each other, wherein the measurement beam is guided to the movable part and forms a first optical signal by reflecting off the movable part, the reference beam is guided to the fixed part and forms a second optical signal by reflecting off the fixed part, the beam splitting module is configured to split the first optical signal and the second optical signal combined in the light splitting module into two beams of light and transmit the two beams of light to the detection module, and the detection module is configured to differentially process signals of the two beams of light and obtain a position of the movable part relative to the fixed part based on the differentially processed signals.

2. The differential fiber laser ruler of claim 1, wherein, The detection module comprises a balanced detector configured to differentially process signals of the two beams of light and a processor configured to obtain the position of the movable part relative to the fixed part based on the differentially processed signals.

3. The differential fiber laser ruler of claim 1, wherein, The FMCW is transmitted to the light splitting module via an optical fiber.

4. The differential fiber laser ruler of claim 3, wherein, The FMCW is transmitted to the light splitting module via an optical fiber and a collimation module in sequence, and the collimation module is configured to collimate the light beam.

5. The differential fiber laser ruler of claim 1, wherein, The light splitting module comprises a light splitting element and a reflecting element, the light splitting element is configured to receive the FMCW and split the FMCW into the measurement beam and the reference beam, the measurement beam is guided to the movable part by reflecting off the light splitting element, and the reference beam is transmitted to the reflecting element after being transmitted through the light splitting element and is guided to the fixed part by reflecting off the reflecting element.

6. The differential fiber laser ruler of claim 1, wherein, The fixed part is provided with a reference object corresponding to the reference beam, and the reference object is configured to reflect the reference beam.

7. The differential fiber laser ruler of claim 6, wherein, The differential fiber laser ruler has a cooperative target measurement function and / or a non-cooperative target measurement function, in response to the differential fiber laser ruler having the cooperative target measurement function, the reference object is a reflector, and in response to the differential fiber laser ruler having the non-cooperative target measurement function, the reference object is the fixed part itself.

8. The differential fiber laser ruler of claim 1, wherein, Paths in which the measurement beam and the reference beam propagate are parallel to a direction in which the movable part moves relative to the fixed part.

9. A method of measuring, characterized by, A method for measuring a position of a movable part relative to a fixed part in a motion system having the movable part and the fixed part using the differential fiber laser ruler of any one of claims 1 to 8.

10. The measurement method according to claim 9, characterized by, The movable part can move relative to the fixed part in multiple directions, and at least one differential fiber laser ruler is arranged in each of the multiple directions to obtain a position of the movable part relative to the fixed part in each direction.

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