Differential fiber laser ruler based on frequency modulation continuous waves

Abstract

The invention discloses a frequency-modulated continuous wave-based differential fiber laser ruler, which is used for measuring the position of a movable part relative to a fixed part in a motion system, and comprises a first generation module, a light splitting module, a beam splitting module and a detection module, and is characterized in that the first generation module is configured to emit frequency-modulated continuous laser; the light splitting module is configured to split the frequency-modulated continuous laser into a measuring light beam and a reference light beam, the measuring light beam is guided to the movable part and is reflected by the movable part to form a first light signal, and the reference light beam is guided to the fixed part and is reflected by the fixed part to form a second light 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, and the detection module is configured to perform differential processing on the signals of the two beams of light and obtain the position of the movable part relative to the fixed part based on the differentiated signals. As a result, the accuracy of measuring the position of the movable part with respect to the fixed part can be improved.

Description

Technical Field

[0001] The present disclosure generally relates to the intelligent manufacturing equipment industry, and more particularly to a differential fiber laser ruler based on frequency modulated continuous waves. Background Art

[0002] Production equipment and measuring equipment in the industrial field usually have a motion platform, which generally includes a base, a stage and a driving mechanism. The driving mechanism can drive the stage to move relative to the base in the XY plane. In order to ensure processing accuracy or measurement accuracy, it is necessary to improve the motion accuracy of the stage. Therefore, during the control process of the motion platform, it is necessary to detect the position of the stage (that is, the position of the stage relative to the base) in real time to ensure that the motion accuracy of the stage meets the processing requirements or measurement requirements.

[0003] The traditional method of detecting the position of the stage is usually to install an encoder on the drive mechanism (such as a servo motor) and detect the position of the stage in real time through the pulses output by the encoder. However, due to the limited accuracy of the transmission components in the drive mechanism (such as screw drive, synchronous belt drive or belt drive, etc.), it is often 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 precision. 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 during the movement of the stage (that is, the entire motion platform will vibrate), 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 phase method for measurement, without setting a reference optical path or directly setting the reference optical path in the host. The measured distance is actually the relative distance between the stage and the laser ruler, which causes the error caused by the vibration of the stage to be included, and cannot accurately reflect the position of the stage relative to the base. Therefore, the accuracy of measuring the position of the stage using a laser ruler based on frequency modulated continuous waves needs to be improved. Summary of the invention

[0005] The present disclosure is proposed in view of the above-mentioned situation, and an object of the present disclosure 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.

[0006] To this end, the first aspect of the present disclosure provides a differential fiber optic laser ruler based on frequency modulated continuous waves, which is a differential fiber optic laser ruler 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, the differential fiber optic laser ruler comprising: a first generating module, a splitting module, a beam splitting module and a detection module, the first generating module being configured to emit frequency modulated continuous laser light, the splitting module being configured to split the frequency modulated continuous laser light into a measuring beam and a reference beam parallel to each other, wherein the measuring beam is guided to the movable part and is reflected by the movable part to form a first light signal, the reference beam is guided to the fixed part and is reflected by the fixed part to form a second light signal, the beam splitting module being configured to split the first light signal and the second light signal combined in the splitting module into two light beams, and transmit the two light beams to the detection module, the detection module being configured to perform differential processing on the signals of the two light beams and obtain the position of the movable part relative to the fixed part based on the differential signals.

[0007] In the first aspect of the present disclosure, since both the measuring light beam and the reference light beam are guided to the motion system, when the motion system vibrates, the movable part and the fixed part will vibrate synchronously, so that the first light signal and the second light signal simultaneously carry the same vibration signal (that is, a common-mode vibration signal), so that the vibration error caused by the motion system becomes a common-mode error, and 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 differential signal.

[0008] In addition, in the differential fiber optic laser ruler involved in the first aspect of the present disclosure, optionally, 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.

[0009] In addition, in the differential fiber laser ruler involved in the first aspect of the present disclosure, an optical fiber is optionally included, and the frequency modulated continuous laser is transmitted to the light splitting module via the optical fiber. In this case, the frequency modulated continuous laser is guided to the light splitting module through the optical fiber, so that the light splitting module can be independent of the host device and away from the heat source (such as 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 involved in the first aspect of the present disclosure, a collimation module is optionally included, and the frequency modulated continuous laser is transmitted to the light splitting module via the optical fiber and the collimation module in sequence, and the collimation module is configured as a collimated light beam. In this case, when the first light signal and the second light signal are transmitted to the detection module via the collimation module and the optical fiber in sequence, the intensity and energy density of the first light signal and the second light signal can be increased by the collimation module, thereby enhancing the interference effect of the first light signal and the second light signal, thereby enhancing the intensity of the interference signal.

[0011] In addition, in the differential fiber laser ruler involved in the first aspect of the present disclosure, optionally, the spectroscopic module includes a spectroscopic element and a reflective element, the spectroscopic element is configured to receive the frequency modulated continuous laser and split the frequency modulated continuous laser into the reference beam and the measurement beam, the measurement beam is reflected by the spectroscopic element and guided to the movable part, and the reference beam is transmitted through the spectroscopic element and then transmitted to the reflective element and reflected by the reflective element and guided to the fixed part. In this case, it is easy to split the frequency modulated continuous laser into two uniform and mutually parallel reference beams and measurement beams, and the internal structure of the spectroscopic module can be simplified.

[0012] In addition, in the differential fiber laser ruler involved in the first aspect of the present disclosure, optionally, the fixing portion 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, the reflection of the reference beam by the reference object can increase the intensity of the second optical signal, which is conducive to increasing the intensity of the interference signal obtained by the detection module.

[0013] In addition, in the differential fiber laser ruler involved in the first aspect of the present disclosure, optionally, the differential fiber laser ruler has a cooperative target measurement function and / or a non-cooperative target measurement function, and in response to the differential fiber laser ruler having a cooperative target measurement function, the reference object is a reflective device, and in response to the differential fiber laser ruler having a non-cooperative target measurement function, the reference object is the fixed part itself. In this case, by utilizing the cooperative target measurement function of the differential fiber laser ruler, the information of the measured reflective device can be used as the information of the fixed part, and the intensity of the second optical signal can be increased by the reflective device. In addition, by utilizing 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 involved in the first aspect of the present disclosure, optionally, the propagation paths of the measuring beam and the reference beam are parallel to the direction in which the movable part moves 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 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] A second aspect of the present disclosure provides a measurement method, which is a method of using the differential fiber optic laser ruler described in the first aspect of the present disclosure to measure the position of the movable part relative to the fixed part in a motion system having a fixed part and a movable part.

[0016] In addition, in the measurement method involved in 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 provided 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, it is possible to provide a differential fiber laser ruler based on frequency modulated continuous laser light that can improve the accuracy of measuring the position of a stage. BRIEF DESCRIPTION OF THE 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 It is a schematic diagram showing the application scenario of the differential fiber laser ruler involved in the example of the present disclosure.

[0020] Figure 2 is a schematic diagram showing a motion system involved in an example of the present disclosure.

[0021] Figure 3A It is a block diagram showing the composition of the first embodiment of the differential fiber laser encoder involved in the example of the present disclosure.

[0022] Figure 3B It is a block diagram showing the composition of the second embodiment of the differential fiber laser encoder involved in the example of the present disclosure.

[0023] Figure 4A It is a schematic diagram showing the working principle of the differential fiber laser ruler of the first embodiment involved in the example of the present disclosure.

[0024] Figure 4B It is a schematic diagram showing the working principle of the differential fiber laser ruler of the second embodiment involved in the example of the present disclosure.

[0025] Figure 5 Schematic diagram showing the positional relationship between the spectroscopic module and the motion system involved in the example of the present disclosure.

[0026] Figure 6 It is a schematic diagram showing the structure of the optical splitting module involved in the example of the present disclosure.

[0027] Figure 7 2 is a schematic diagram showing a plurality of differential fiber laser rulers arranged in the X-axis direction and the Y-axis direction respectively according to an example of the present disclosure.

[0028] Description of reference numerals:

[0029] 1…differential fiber laser encoder, 10…first generation module, 11…spectrometer module, 112…spectrometer element, 114…reflector element, 12…detection module, 13…coupling module, 14…beam splitting module, 15…optical fiber, 16…collimation 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…column, 28…reference object,

[0030] L…frequency modulated continuous laser, L1…measuring beam, L10…first light signal, L2…reference beam, L20…second light signal, A1…first landing point, A2…second landing point, d…distance of the movable part relative to the fixed part. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

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

[0033] The differential fiber optic laser ruler based on frequency modulated continuous wave involved in the present disclosure can guide the measuring light beam to the movable part of the motion system and guide the reference light beam to the fixed part of the motion system. When the motion system vibrates, the reflected light of the measuring light beam (that is, the first light signal) and the reflected light of the reference light beam (that is, the second light signal) carry the same vibration signal at the same time. Therefore, the vibration error caused by the motion system is a common mode error. By differentially processing the signals of the two beams of light 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 differential signal.

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

[0035] The differential fiber laser encoder involved in the present disclosure is described below with reference to the accompanying drawings.

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

[0037] For some examples, see Figure 1 The differential fiber laser ruler 1 of the present disclosure 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).

[0038] In some examples, the movable portion 24 may be driven by the driving portion to move relative to the fixed portion 22 , and the movable portion 24 may vibrate synchronously with the fixed portion 22 when moving.

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

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

[0041] In some examples, for the motion system 2, the classification 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., the first structure) in the motion system 2 moves with the movable part 24 when the movable part 24 moves along the X-axis direction, the first structure should not be classified as the fixed part 22. For another example, if a certain structure (e.g., the second structure) in the motion system 2 does not move with the movable part 24 when the movable part 24 moves along the Y-axis direction, the second structure can be classified as the fixed part 22.

[0042] For some examples, see Figure 1 or Figure 2 The motion system 2 may include a column 26 extending along the Z-axis direction. In addition, the movable portion 24 may have a through hole 240 penetrating the front and back sides of the movable portion 24 , and the column 26 may be arranged in a manner of passing through the through hole 240 .

[0043] In some examples, the column 26 can serve as the fixing portion 22. In some examples, see Figure 2 , the column 26 can belong to the fixing part 22 relative to both the X-axis direction and the Y-axis direction.

[0044] In some examples, the motion system 2 may be a motion platform, the fixed portion 22 may be a fixed portion of the motion platform, and the movable portion 24 may be a stage that can move relative to the fixed portion of the motion platform. In some examples, the fixed portion 22 may not be limited to the motion platform, for example, the fixed portion 22 may be a base that is firmly mounted on the motion system 2.

[0045] In some examples, the differential fiber laser encoder 1 can remain relatively still with respect to the fixed portion 22. In some examples, the differential fiber laser encoder 1 can be set independently of the motion system 2 and remain relatively still with respect to the fixed portion 22 (see Figure 1 ).

[0046] It should be noted that the relative stillness of the differential fiber laser ruler 1 and the fixed part 22 may mean that the two remain relatively still at a macroscopic level, and vibrations at a microscopic level (such as the synchronous vibration of the movable part 24 and the fixed part 22) will not destroy the relative stillness between the differential fiber laser ruler 1 and the fixed part 22.

[0047] Figure 3A It is a block diagram showing the composition of the first embodiment of the differential fiber laser ruler 1 involved in the example of the present disclosure. Figure 3B It is a block diagram showing the composition of the second embodiment of the differential fiber laser ruler 1 involved in the example of the present disclosure. Figure 4A It is a schematic diagram showing the working principle of the differential fiber laser ruler 1 of the first embodiment involved in the example of the present disclosure. Figure 4B It is a schematic diagram showing the working principle of the differential fiber laser ruler 1 of the second embodiment involved in the example of the present disclosure. Figure 5 Schematic diagram showing the positional relationship between the spectroscopic module 11 and the motion system 2 involved in the example of the present disclosure.

[0048] For some examples, see Figure 3A and Figure 4A , the differential fiber laser encoder 1 may include a first generating module 10 and a detecting 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 measuring beam L1 and a reference beam L2 to a target (e.g., a motion system 2) in a frequency modulated continuous wave manner, and the measuring beam L1 and the reference beam L2 may be reflected back to the differential fiber laser encoder 1 by the target after being emitted to the target.

[0049] In some examples, the frequency modulated continuous laser light 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 triangle linear frequency modulated continuous wave.

[0050] In some examples, the frequency and time of the linear frequency modulated continuous wave may be linearly related. In some examples, the frequency function of the linear frequency modulated continuous wave may include a frequency modulation bandwidth and a frequency modulation period. The frequency modulation bandwidth may represent the linear variation range of the frequency over time, and the frequency modulation period may represent the time required for the frequency to change from a starting value to a final value.

[0051] Different from the existing interferometric distance measuring laser ruler, the laser ruler involved in the present disclosure uses frequency modulated continuous laser L for distance measurement, and the measured distance is an absolute distance. Even if the light is interrupted during the measurement process, it will not affect the subsequent measurements.

[0052] In some examples, the detection module 12 may be configured to measure the target (eg, 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] For some examples, see Figure 3A and Figure 4A The differential fiber laser ruler 1 may include a light splitting module 11. The light splitting module 11 may be configured to receive the frequency modulated continuous laser light L emitted by the first generating module 10 and split the frequency modulated continuous laser light L into two frequency modulated continuous laser light L beams.

[0054] For some examples, see Figure 4AThe light splitting module 11 can be configured to split the frequency modulated continuous wave laser L into a measuring beam L1 and a reference beam L2, and the measuring beam L1 and the reference beam L2 can be parallel to each other. In some examples, the measuring beam L1 and the reference beam L2 can be frequency modulated continuous waves.

[0055] In some examples, the paths along which the measuring beam L1 and the reference beam L2 propagate may be parallel to the direction in which the movable portion 24 moves relative to the fixed portion 22. In other words, the movable portion 24 may move relative to the fixed portion 22 in the direction in which the measuring beam L1 and the reference beam L2 propagate. Figure 1 In the example shown, the movable portion 24 moves relative to the fixed portion 22 in the X-axis or Y-axis direction, and the corresponding propagation paths of the measuring beam L1 and the reference beam L2 may be parallel to the X-axis or Y-axis direction.

[0056] For some examples, see Figure 5 , the measuring light beam L1 can be guided to the movable part 24, and the measuring light beam L1 reaching the movable part 24 can be reflected by the movable part 24 to form the first light signal L10. In addition, the reference light beam L2 can be guided to the fixed part 22, and the reference light beam L2 reaching the fixed part 22 can be reflected by the fixed part 22 to form the second light signal L20. In this case, when the motion system 2 vibrates, the movable part 24 and the fixed part 22 will vibrate synchronously, so that the first light signal L10 and the second light signal L20 carry the same vibration signal (that is, a common-mode vibration signal) at the same time, so that the vibration error caused by the motion system 2 becomes a common-mode error, thereby facilitating the elimination of the vibration signal by 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 along which the measuring beam L1 propagates may be perpendicular to the side of the movable portion 24. For example, when the movable portion 24 is a stage in a motion platform, the path along which the measuring beam L1 propagates may be perpendicular to the side wall of the stage.

[0058] For some examples, see 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 may receive the reference beam L2 and reflect the reference beam L2 to form a second optical signal L20. In this case, the reflection of the reference beam L2 by the reference object 28 can increase the intensity of the second optical signal L20, which is conducive to increasing the intensity of the interference signal obtained by the detection module 12.

[0059] For some examples, see Figure 2 or Figure 5, the reference object 28 of the fixed part 22 may be parallel to the side of the movable part 24. For example, the plane where the reference object 28 is located may be parallel to the side wall of the stage. However, the present disclosure is not limited thereto, and in other examples, the reference object 28 of the fixed part 22 may not be parallel to the side of the movable part 24.

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

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

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

[0063] In some examples, in response to the differential fiber laser encoder 1 having a cooperative target measurement function, the reference object 28 may be a reflective device, and a reflective device may also be provided on the side of the movable part 24. In this case, by using the cooperative target measurement function of the differential fiber laser encoder 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 may be a retroreflector or a reflector.

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

[0065] In some examples, the first optical signal L10 and the second optical signal L20 may be combined in the optical splitting module 11 and then transmitted to the detection module 12. Figure 4A The first optical signal L10 and the second optical signal L20 can be respectively returned to the spectroscopic module 11 along the paths of the measuring beam L1 and the reference beam L2, and can be combined in the spectroscopic module 11 and then transmitted to the detection module 12.

[0066] For some examples, see Figure 3B and Figure 4BThe differential fiber laser ruler 1 may include a coupling module 13, which may be configured to guide the frequency modulated continuous laser L to be transmitted to the light splitting module 11, and simultaneously guide the first light signal L10 and the second light signal L20 to be transmitted to the detection module 12. In some examples, the coupling module 13 may be disposed between the first generating module 10 and the light splitting module 11 (see Figure 4B ). In some examples, the coupling module 13 may 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, so as to obtain the position of the movable part 24 relative to the fixed part 22.

[0068] For example, by making the propagation paths (i.e., directions) of the measuring 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 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 may refer to: the distance from the first landing point A1 of the measuring beam L1 on the movable part 24 to the second landing point A2 of the reference beam L2 on the fixed part 22 in the propagation direction of the measuring beam L1 and the reference beam L2. 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.

[0070] In some examples, the position of the movable portion 24 relative to the fixed portion 22 may refer to: the position of the first landing point A1 relative to the second landing point A2 in the propagation direction of the measuring beam L1 and the reference beam L2 .

[0071] In some examples, the detection module 12 can be configured to obtain an interference signal 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 form interference light after being combined in the light 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 may carry distance information of the movable part 24 relative to the fixed part 22. Specifically, since the first optical signal L10 and the second optical signal L20 are both frequency modulated continuous waves, the interference signal is a sine-cosine time-varying signal that changes at a fixed frequency (also called an intermediate frequency), and the distance d of the movable part 24 relative to the fixed part 22 can be obtained by measuring the intermediate frequency of the interference signal, and the distance d is positively correlated with the intermediate frequency.

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

[0074]

[0075] Wherein, 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. The specific calculation content can be found in Chinese patent CN202311564905.7, which will not be repeated here.

[0076] In some examples, the detection module 12 may be configured to obtain the position of the movable portion 24 relative to the fixed portion 22 based on the interference signal. Specifically, the detection module 12 may obtain the distance d of the movable portion 24 relative to the fixed portion 22 based on the intermediate frequency of the interference signal and formula (1), thereby obtaining the position of the movable portion 24 relative to the fixed portion 22.

[0077] In the present 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 resolution of ranging by increasing the laser bandwidth, so that the slight distance change between the movable part 24 and the fixed part 22 can be accurately measured, and then the accuracy of measuring the position of the movable part 24 relative to the fixed part 22 can be improved.

[0078] In some examples, the detection module 12 may be configured to obtain an optical path difference between the reference beam L2 and the measuring beam L1 based on the interference signal. Further, based on the optical path difference, the distance d of the movable part 24 relative to the fixed part 22 in the propagation direction of the measuring beam L1 and the reference beam L2 may be obtained, thereby obtaining the position of the movable part 24 relative to the fixed part 22 in the propagation direction of the measuring beam L1 and the reference beam L2. In this case, by making the propagation direction of the measuring 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 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 encoder 1 may include a beam splitter module 14, which may be configured to split a beam of light into two beams of light. In some examples, the beam splitter module 14 may be configured to split the first optical signal L10 and the second optical signal L20 combined in the optical splitter module 11 into two beams of light.

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

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

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

[0083] In some examples, the beam splitting module 14 may be disposed between the detection module 12 and the coupling module 13. In this case, in the process of the coupling module 13 guiding the first optical signal L10 and the second optical signal L20 (i.e., interference light) to be transmitted to the detection module 12, the interference light may 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 may perform differential processing.

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

[0085] In some examples, the detection module 12 may have two channels, and the two channels of the detection module 12 may receive the first interference light and the second interference light, respectively. In other words, the first interference light and the second interference light may 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 both the first light signal L10 and the second light signal L20 carry a common-mode vibration signal, the vibration signal can be reduced or eliminated by differential processing of the two beams of light 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 operations on the two electrical signals to obtain an interference signal with a higher signal-to-noise ratio.

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

[0088] In some examples, the detection module 12 may pre-process the first electrical signal and the second electrical signal (eg, amplify, filter, etc.) and then perform differential processing.

[0089] In some examples, the detection module 12 may include a balanced detector, and the balanced detector may be configured to perform differential processing on the signals of the two light beams. In addition, the balanced detector may also be configured to obtain an interference signal based on the two light beams. For example, the balanced detector may convert the first interference light and the second interference light into corresponding first electrical signals 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.

[0090] In some examples, the detection module 12 may include a processor. The processor may 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 may be an interference signal.

[0091] In some examples, the processor may be configured to obtain a position of the movable portion 24 relative to the fixed portion 22 based on the interference signal.

[0092] In some examples, the first generating module 10, the detecting module 12 and the beam splitting module 14 can be integrated into a host device 3 (see Figure 1 ).

[0093] For some examples, see Figure 3B The differential fiber laser ruler 1 may include an optical fiber 15, which may be used to transmit the frequency modulated continuous laser light L. In some examples, the frequency modulated continuous laser light L emitted by the first generating module 10 may be transmitted to the light splitting module 11 via the optical fiber 15 (see Figure 1 In this case, the frequency modulated continuous laser light L is guided to the spectroscopic module 11 through the optical fiber 15, so that the spectroscopic module 11 is independent of the host device 3 and away from the heat source in the host device 3 (such as the first generating module 10), thereby minimizing the influence of the heat source on the optical fiber 15 and the spectroscopic module 11.

[0094] In some examples, the frequency modulated continuous laser L can be transmitted to the light 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 detection 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 optical path and the first optical signal L10 and the second optical signal L20 also share the same optical fiber optical path, the error caused by the temperature of the optical fiber 15 is a common mode error. By performing 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 fiber.

[0095] Figure 6Schematic diagram showing the structure of the optical splitting module 11 involved in the example of the present disclosure.

[0096] For some examples, see Figure 6 , the light splitting module 11 may include a light splitting element 112 and a reflective element 114. In some examples, the light splitting element 112 may be configured to receive the frequency modulated continuous laser light L and split the frequency modulated continuous laser light L into a reference beam L2 and a measuring beam L1.

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

[0098] However, the present disclosure is not limited thereto, and in other examples, the reference beam L2 may be reflected by the beam splitter 112 and guided to the fixed portion 22. In addition, the measuring beam L1 may be transmitted to the reflective element 114 after being transmitted through the beam splitter 112, and the measuring beam L1 may be reflected by the reflective element 114 and guided to the movable portion 24.

[0099] In some examples, the beam splitter element 112 may be a beam splitter. In addition, the reflective element 114 may be a reflector.

[0100] For some examples, see Figure 3B and Figure 4B The differential fiber laser encoder 1 may include a collimator module 16, and the collimator module 16 may be configured to collimate the light beam. For example, the collimator module 16 may adjust the shape of the light beam to a collimated shape.

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

[0102] In some examples, the frequency modulated continuous laser light L emitted by the first generating module 10 can be sequentially transmitted to the light splitting module 11 via the optical fiber 15 and the collimating module 16. In some examples, the first optical signal L10 and the second optical signal L20 can be sequentially transmitted to the detection module 12 via the collimating module 16 and the optical fiber 15 (see Figure 4BIn this case, the intensity and energy density of the first optical signal L10 and the second optical signal L20 can be increased by the collimation module 16, thereby enhancing the interference effect of the first optical signal L10 and the second optical 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 collimating module 16 may constitute a sensing probe. In other words, the sensing probe may include the light splitting module 11 and the collimating module 16. In some examples, the sensing probe may be connected to the first generating module 10 via an optical fiber 15.

[0104] For some examples, see 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 indication beam. In some examples, the indication beam may coincide with the frequency modulated continuous laser light L emitted by the first generating module 10. In some examples, the indication beam may be red visible light.

[0105] In some examples, the second generating module 17 can be configured to emit an indication beam to indicate the fixed part 22 and the movable part 24 respectively. Specifically, before using the differential fiber laser ruler 1, the indication 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.

[0106] For some examples, see Figure 4A or Figure 4B , the second generating module 17 may be disposed between the coupling module 13 and the light splitting module 11. In some examples, the second generating module 17 may be coupled between the coupling module 13 and the light splitting module 11 via a wavelength division multiplexer.

[0107] For some examples, see Figure 3B and Figure 4B The differential fiber laser ruler 1 may include a feedback module 18 , and the feedback module 18 may be configured to obtain frequency information of the frequency modulated continuous laser L emitted by the first generating module 10 .

[0108] In some examples, the feedback module 18 can feedback the frequency information of the frequency modulated continuous laser L to the processor in the detection module 12, and 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., changes linearly).

[0109] For some examples, see Figure 3B and Figure 4BThe differential fiber laser encoder 1 may include an isolator 19 , and the isolator 19 may be disposed between the first generating module 10 and the coupling module 13 .

[0110] In some examples, the isolator 19 can be used to couple and isolate the first generating module 10 and the optical fiber 15 (e.g., polarization-maintaining optical fiber). In this case, the isolator 19 can reduce the situation where the spectral purity of the first generating module 10 is reduced due to the reverse propagation of the first optical signal L10 and the second optical signal L20, or the situation where the modulation of the frequency modulated continuous laser L is unstable or the output power is unstable. In some examples, the isolator 19 can be a polarization-maintaining optical fiber isolator.

[0111] Figure 7 1 is a schematic diagram showing a plurality of differential fiber laser rulers 1 arranged in the X-axis direction and the Y-axis direction respectively according to an example of the present disclosure.

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

[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 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 through the at least one differential fiber laser ruler 1 provided 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, arranging the differential fiber laser encoder 1 in the direction in which the movable part 24 moves relative to the fixed part 22 can mean that the measuring 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 in which the differential fiber laser encoder 1 is arranged needs to satisfy the measurement beam L1 and the reference beam L2 are parallel to the X-axis direction.

[0115] As described above, the movable portion 24 can move relative to the fixed portion 22 in three-dimensional space. 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 rulers 1 may be provided in the X-axis direction and the plurality of differential fiber laser rulers 1 may be arranged along the Z-axis direction, so that a plurality of pairs of measuring 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 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 rulers 1.

[0116] In addition, 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, a plurality of differential fiber laser rulers 1 can be set in the Y-axis direction and the plurality of differential fiber laser rulers 1 are arranged along the Z-axis direction, so that a plurality of pairs of measuring beams L1 and reference beams L2 are distributed along the Z-axis direction and parallel to the Y-axis direction.

[0117] In some examples, before executing the measurement method of the present disclosure, the differential fiber laser encoder 1 may be installed and debugged first.

[0118] In some examples, installing the differential fiber laser encoder 1 may include: making the measuring beam L1 and the reference beam L2 parallel to the measuring direction based on the direction (i.e., the measuring direction) in which the movable portion 24 moves relative to the fixed portion 22. For example, if it is necessary to measure the position of the movable portion 24 relative to the fixed portion 22 in the X-axis direction, the orientation of the spectroscopic module 11 (or the sensor probe) may be adjusted so that the measuring beam L1 and the reference beam L2 are parallel to the X-axis direction.

[0119] In some examples, making the measuring beam L1 parallel to the measuring direction may include: making the measuring beam L1 align with the movable part 24. For example, by adjusting the orientation of the spectroscopic module 11 (or the sensing probe) so that the measuring beam L1 is aligned with the side of the movable part 24 and the side of the movable part 24 is perpendicular to the measuring beam L1. In addition, making the reference beam L2 parallel to the measuring direction may include: making the reference beam L2 align 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 may be parallel.

[0120] In some examples, debugging the differential fiber laser encoder 1 may include: checking whether the installation of the differential fiber laser encoder 1 is appropriate, that is, checking whether the orientation (or posture) of the differential fiber laser encoder 1 meets the measurement requirements.

[0121] For example, two differential fiber laser rulers 1 (i.e., the first differential fiber laser ruler and the second differential fiber laser ruler) are used 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 measurement beam L1 and the reference beam L2 of the first differential fiber laser ruler 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 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 not, 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.

[0122] Although the present disclosure is specifically described above in conjunction with the accompanying drawings and examples, it is to be understood that the above description does not limit the present disclosure in any form. Those skilled in the art may modify and change the present disclosure as needed without departing from the essential spirit and scope of the present disclosure, and these modifications and changes all fall within the scope of the present disclosure.

Claims

1. A differential fiber laser encoder based on frequency modulated continuous wave, which is used to measure 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 includes: a first generating module, a spectroscopic module, a beam splitting module and a detection module, wherein the first generating module is configured to emit frequency-modulated continuous laser light, the spectroscopic module is configured to split the frequency-modulated continuous laser light into a measuring beam and a reference beam parallel to each other, wherein the measuring beam is guided to the movable part and is reflected by the movable part to form a first light signal, and the reference beam is guided to the fixed part and is reflected by the fixed part to form a second light signal, the beam splitting module is configured to split the first light signal and the second light signal combined in the spectroscopic module into two light beams, and transmit the two light beams to the detection module, and the detection module is configured to perform differential processing on the signals of the two light beams and obtain the position of the movable part relative to the fixed part based on the differential signals.

2. The differential fiber laser encoder according to claim 1, 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 light beams. The processor is configured to obtain the position of the movable part relative to the fixed part based on the differential signal.

3. The differential fiber laser encoder according to claim 1, characterized in that: It comprises an optical fiber, and the frequency modulated continuous laser is transmitted to the light splitting module via the optical fiber.

4. The differential fiber laser encoder according to claim 3, characterized in that: It comprises a collimation module, the frequency modulated continuous laser is transmitted to the light splitting module via the optical fiber and the collimation module in sequence, and the collimation module is configured as a collimated light beam.

5. The differential fiber laser encoder according to claim 1, characterized in that: The spectroscopic module includes a spectroscopic element and a reflective element. The spectroscopic element is configured to receive the frequency-modulated continuous laser and split the frequency-modulated continuous laser into the reference beam and the measuring beam. The measuring beam is reflected by the spectroscopic element and guided to the movable part. The reference beam is transmitted through the spectroscopic element and then transmitted to the reflective element and reflected by the reflective element and guided to the fixed part.

6. The differential fiber laser encoder according to claim 1, characterized in that: The fixing portion 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 encoder according to claim 6, characterized in that: 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 reflective device. 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 encoder according to claim 1, characterized in that: The paths along which the measuring beam and the reference beam propagate are parallel to a direction in which the movable portion moves relative to the fixed portion.

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

10. The measuring method according to claim 9, characterized in that: 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 direction of the multiple directions to obtain the position of the movable part relative to the fixed part in each direction.

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