Interference measurement system

Abstract

The present disclosure relates to an interferometry system comprising: a light source emitting coherent light; the coupler is provided with a first port, a second port and a third port, and the coupler is configured to receive the coherent light emitted by the light source through the first port, divide the coherent light into a plurality of beams of coherent light through the second port and receive a plurality of beams of modulated light modulated by physical quantity to be measured through the second port; a plurality of sensor devices configured to receive one of the plurality of beams of coherent light via the second port, and to form and output the modulated light modulated by the physical quantity to be measured; and the interference demodulation device comprises a birefringent element, and is configured to receive the plurality of beams of modulated light modulated by the physical quantity to be measured through the third port, and demodulate the plurality of beams of modulated light modulated by the physical quantity to be measured through different sections of the birefringent element to obtain a plurality of interference spectra of the physical quantity to be measured.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an interferometric measurement system. BACKGROUND

[0002] "Interferometric measurement" is a method of measurement using the interference phenomenon of waves. A beam of light is usually divided into two beams, i.e. a reference light and a detection light modulated by a physical quantity to be measured, and the two beams of light form an interference pattern when superimposed. The relevant information of the physical quantity to be measured is obtained by analyzing and processing the interference pattern. Since the wavelength of light is very short, the light paths of the two beams of light can be slightly different and can be detected. Therefore, optical interferometric measurement has always been a very valuable and very accurate measurement technology.

[0003] In most application cases, two or more sensors are required to measure multiple physical quantities such as pressure, temperature, strain, flow rate, force, etc. at the same time, so the modulated light modulated by the physical quantity to be measured can carry path length difference information corresponding to multiple physical quantities to be measured respectively, and therefore a demodulation device capable of demodulating multiple path length differences is required. Although multiple demodulation devices can be used to realize the simultaneous operation of multiple channels, the corresponding system complexity, cost and volume will be increased. SUMMARY

[0004] Therefore, the purpose of the present disclosure is to provide an interferometric measurement system which reduces the system complexity, cost and volume.

[0005] The above purpose is achieved by the interferometric measurement system according to the following description.

[0006] An interferometric measurement system comprises: a light source emitting coherent light; a coupler having a first port, a second port and a third port, the coupler being configured to receive the coherent light emitted from the light source via the first port, and to divide the coherent light into multiple beams of coherent light via the second port, and to receive multiple beams of modulated light modulated by a physical quantity to be measured via the second port; multiple sensor devices configured to receive one of the multiple beams of coherent light via the second port, and to form and output the modulated light modulated by the physical quantity to be measured; an interference demodulation device comprising a birefringent element, and being configured to receive the multiple beams of modulated light modulated by the physical quantity to be measured via the third port, and to demodulate the multiple beams of modulated light modulated by the physical quantity to be measured by different sections of the birefringent element to obtain multiple interference spectra of the physical quantity to be measured.

[0007] In one embodiment, the birefringent element is a birefringent wedge, and the wedge angle of the birefringent wedge is greater than 7°.

[0008] In one embodiment, the cavity length difference of the multiple sensor devices is not less than 1 micrometer.

[0009] In one embodiment, a sensor body is also included, the sensor body configured to hold the sensor device, and a dimension of a cavity length of the force sensing cavity of at least one of the sensor devices is varied in response to a force applied to the sensor body.

[0010] In one embodiment, the sensor body includes a first segment, a second segment, the first segment and the second segment defining a gap therebetween, the gap bridged by a connecting segment, the connecting segment causing a difference in sensitivity of the sensor body to lateral forces in various directions to be within a factor of 2; the force sensing cavity located in the gap.

[0011] In one embodiment, at least a portion of an outer surface of the connecting segment is recessed inwardly relative to an outer surface of the first segment and an outer surface of the second segment to form the gap between the first segment and the second segment; at least one end of the connecting segment is connected to the first segment or the second segment by an annular portion, the annular portion defining at least a portion of an axial boundary of the gap, the annular portion having a thickness that is less than a width of an annular face thereof.

[0012] In one embodiment, the annular portion includes a first annular portion and a second annular portion, the first annular portion defining a portion of the axial boundary of the gap and connecting a first end of the connecting segment to the first segment, the second annular portion defining a portion of the axial boundary of the gap and connecting a second end of the connecting segment to the second segment.

[0013] In one embodiment, the annular portion extends in a lateral direction perpendicular to the axial direction, or at an angle between 0 and 15° relative to the lateral direction.

[0014] In one embodiment, the sensor body defines a longitudinal axis; the first segment and the second segment are bridged by a plurality of elastic connecting segments, the plurality of elastic connecting segments rotationally spaced about the longitudinal axis, a difference in rotational spacing angle between the plurality of elastic connecting segments being less than 20°.

[0015] In one embodiment, the interferometric demodulation device includes a condenser configured to receive modulated light; a first polarizer disposed downstream of the condenser and having a first polarization direction; a second polarizer disposed downstream of the first polarizer and having a second polarization direction perpendicular or parallel to the first polarization direction; and a birefringent element located between the first polarizer and the second polarizer and having an optical axis at 45° or -45° to the first polarization direction. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments of the present disclosure will be briefly introduced below. Among them, the drawings only serve to show some embodiments of the present disclosure, and not to limit all embodiments of the present disclosure to this. In the drawings:

[0017] Figure 1 A schematic diagram of an interferometric measurement system according to one embodiment of the present disclosure is shown;

[0018] Figure 2 A schematic diagram of an interferometric measurement system according to another embodiment of the present disclosure is shown;

[0019] Figure 3 A structural schematic diagram of a sensor body according to a first embodiment of the present disclosure is shown;

[0020] Figure 4 A structural schematic diagram of a sensor body according to a second embodiment of the present disclosure is shown;

[0021] Figure 5 A structural schematic diagram of a sensor body according to a third embodiment of the present disclosure is shown;

[0022] Figure 6 A structural schematic diagram of a sensor body according to a fourth embodiment of the present disclosure is shown;

[0023] Figure 7 A structural schematic diagram of a sensor body according to a fifth embodiment of the present disclosure is shown;

[0024] Figure 8 A structural schematic diagram of a sensor body according to a sixth embodiment of the present disclosure is shown.

[0025] Light source 2 - coherent light 3 - coupler 31 - first port 32 - second port 33 - third port 4 - modulated light 5 - sensor device 51 - reflecting member 52 - incident optical fiber 53 - force sensing cavity 6 - interference demodulation device 61 - condenser 62 - first polarizer 63 - birefringent element 64 - second polarizer 65 - image sensor 66 - signal processing unit

[0026] 100 - sensor body 10 - first section 20 - second section 30 - intermediate section 31 - first end of intermediate section 32 - second end of intermediate section 40 - gap 41 - first annular portion 42 - second annular portion DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0028] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not necessarily indicate a quantity limitation. The terms “comprising,” “including,” or “having,” and similar terms mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. The terms “connected” or “connected,” and similar terms are not limited to the physical or mechanical connection or connection shown in the drawings, but may include equivalent connections or connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right,” etc., are used only to indicate relative positional relationships, which may change accordingly when the absolute position of the described object changes.

[0029] like Figure 1 As shown, the interferometric measurement system according to this disclosure includes a light source 1, a coupler 3, multiple sensor devices 5, and an interferometric demodulation device 6. The light source 1 emits coherent light 2, such as low-coherence light, for example, a halogen tungsten lamp, an LED, an SLED, etc.

[0030] Coupler 3 has a first port 31, a second port 32, and a third port 33. Coupler 3 is configured to receive coherent light 2 emitted from light source 1 via the first port 31, split the coherent light into multiple coherent beams via the second port 32, receive multiple beams of modulated light 4 modulated by the physical quantity to be measured via the second port, and transmit the modulated light 4 to the interferometric demodulation device 6 via the third port. Coupler can be a two-to-many coupler, such as a two-to-two coupler or a two-to-three coupler. The second port 32 includes multiple interfaces, each of which is connected to the sensor device 5 via an optical fiber. The number of sensor devices 5 determines the number of couplers.

[0031] The interferometric measurement system comprises a plurality of sensor devices 5, each of which is configured to receive at least one of the plurality of beams of coherent light from the second port 32 and to form and output modulated light modulated by the physical quantity to be measured. The modulated light can carry optical path difference information corresponding to the physical quantity to be measured. The plurality of beams of coherent light can be incident into the interference optical paths of the plurality of sensor devices 5 respectively, and then converted by the sensor devices 5 into a plurality of beams of modulated light modulated by the physical quantity to be measured. The plurality of beams of modulated light 4 returns to the coupler 3 and is transmitted to the interference demodulation device 6 through the third port 33 of the coupler 3. The cavity length difference of the plurality of sensor devices is not less than 1 micrometer, which can prevent mutual interference between the sensor devices, and the interference peaks of the plurality of sensor devices do not coincide, thereby improving the demodulation accuracy of each sensor device.

[0032] As shown in Figure 1 The interferometric measurement system comprises a plurality of sensor devices 5 connected in parallel downstream of the light source 1. The number of sensor devices 5 can depend on the application environment and requirements. The sensor devices 5 are based on double-beam or multi-beam interference, such as Michelson interferometer, Fizeau interferometer, Fabry-Perot interferometer, etc. These interferometers can be prepared into micro-optical sensor chips using MEMS technology, Optics-on-chip technology, etc. and connected to the system through optical fibers. In most application environments, the corresponding physical quantity is detected by a probe-type sensor. For example, the plurality of sensor devices 5 in the interferometric measurement system can be configured to operate simultaneously to achieve simultaneous measurement of multiple physical quantities. The modulated light output by the plurality of sensor devices 5 can be guided through different sections of the birefringent element of the interference demodulation device 6, so that the same interference demodulation device simultaneously demodulates the cavity lengths of the plurality of sensor devices 5.

[0033] The interference demodulation device 6 is configured to receive the modulated light 4 formed by the plurality of sensor devices 5 and demodulate the modulated light 4 to obtain the measurement result of the physical quantity to be measured. The interference demodulation device 6 comprises a condenser 61 configured to receive the modulated light, a first polarizer 62 disposed downstream of the condenser and having a first polarization direction, a second polarizer 64 disposed downstream of the first polarizer and having a second polarization direction perpendicular or parallel to the first polarization direction, and a birefringent element 63 located between the first polarizer and the second polarizer and having an optical axis at 45° or -45° to the first polarization direction.

[0034] The interference demodulation device can comprise a birefringent element 63 as shown in Figure 1The diagram shows an image sensor 65 and a signal processing unit 66. The image sensor 65 acquires the complete interference spectrum and can be a CCD, CMOS, or similar sensor. The signal processing unit 66 receives the signal from the image sensor 65 and processes it. Specifically, the signal processing unit 66 demodulates the changes in physical quantities such as the intensity and phase of the interference spectrum to obtain the change in optical path difference. Alternatively, a photodetector that acquires sampling points of the interference spectrum can be used instead of the image sensor. The photodetector can be, for example, a photodiode. The signal processing unit obtains the change in the demodulated optical signal by measuring the changes in the sampling points in the time domain, frequency domain, or spatial domain.

[0035] Using the interferometric measurement system disclosed herein, multiple modulated beams output by multiple sensor devices 5 are demodulated through different sections of the birefringent element of the interferometric demodulation device 6, enabling the same interferometric demodulation device to demodulate the cavity lengths of multiple sensor devices 5 simultaneously. This not only reduces the complexity of the system but also reduces the cost and size of the interferometric measurement system.

[0036] In one embodiment, the birefringent element 63 is a birefringent optical wedge. The larger the wedge angle of the birefringent optical wedge, the larger the measurement range, thereby reducing the limitation on the cavity length difference of the sensor device. Preferably, the wedge angle of the birefringent optical wedge is greater than 7°.

[0037] like Figure 2 As shown, the interferometric measurement system includes a light source 1, a coupler 3, an interferometric demodulation device 6, multiple sensor devices 5, and a sensor body 100 for holding the sensor devices 5. The number of sensor devices 5 can be multiple, and the cavity length difference between the multiple sensor devices is not less than 1 micrometer. Preferably, the multiple sensor devices are evenly distributed on the sensor body 100. Each sensor device 5 includes a reflective member 51 and an incident optical fiber 52. A plurality of reflective members 51 pass through a first section 10 along the axial direction, and a plurality of incident optical fibers 52 pass through a second section 20 along the axial direction, with the number of reflective members 51 being the same as the number of incident optical fibers 52, thus establishing a one-to-one correspondence between the reflective members 51 and the incident optical fibers 52. One end of each reflective member 51 extends into the gap 40 and is opposite to the end of each incident optical fiber 52 extending into the gap 40. A force-sensing cavity 53 is defined between the end of the reflective member 51 and the end of the incident optical fiber 52. The second port 32 of the coupler 3 has multiple interfaces, which are respectively connected to the multiple incident optical fibers 52, i.e., the multiple sensor devices 5 are connected in parallel. This interferometric measurement system achieves simultaneous demodulation of multiple force sensing cavities of the force sensor through the same interferometric demodulation device, saving costs and reducing system complexity.

[0038] The sensor body 100 comprises a first section 10, a second section 20, and an intermediate section 30 connecting the first section 10 and the second section 20. In the present disclosure, the first section 10 can also be referred to as the distal end of the force sensor, and the second section 20 can also be referred to as the proximal end of the force sensor. Each of the first section 10, the second section 20, and the intermediate section 30 is preferably a hollow cylindrical structure enclosed by a side wall, in particular a circular cylindrical structure with a circular cross-section.

[0039] The outer surface of the intermediate section 30 is inwardly recessed relative to the outer surface of the first section 10 and the outer surface of the second section 20 to form a gap 40 between the first section 10 and the second section 20. When the distal end of the force sensor, i.e. the first section 10, is subjected to a force, the first section 10 deforms relative to the second section 20, so that the size of the gap 40 in the axial direction also changes, so that the size of the force sensing cavity of at least one sensor device located in the gap 40 changes.

[0040] The sensor body 100 comprises at least one annular portion. As shown in Figure 3 The sensor body comprises a first annular portion 41 and a second annular portion 42, which define two axial boundaries of the gap 40. The first annular portion 41 connects the first end 31 of the intermediate section 30 and the first section 10, and the second annular portion 42 connects the second end 32 of the intermediate section 30 and the second section 20. In the present disclosure, the first annular portion 41 and the second annular portion 42 can be collectively referred to as an annular portion. In the present disclosure, the annular portion is a thin-walled structure, i.e. its thickness is less than the width of its annular surface. Since the annular portion is a symmetrical annular structure with the central axis of the sensor body 100 as the central axis, the cross-sectional moment of inertia of the sensor body 100 in all directions can be made equal, thereby minimizing the sensitivity difference of the sensor in each direction and improving the overall accuracy of the sensor.

[0041] The annular portion extends in a transverse direction perpendicular to the axial direction, or at an angle of 0-15° relative to the transverse direction. The width-to-thickness ratio of the annular portion is greater than 1, and the thickness of the annular portion is less than the width of its annular surface. Preferably, the width-to-thickness ratio of the annular portion is greater than or equal to 2, or greater than or equal to 2.5, or greater than or equal to 3. Preferably, the width-to-thickness ratio of the annular portion is between 2-4, and particularly preferably, the width-to-thickness ratio of the annular portion is between 2-3.

[0042] In the following, embodiments of the sensor body according to the present disclosure will be described with reference to Figures 4-7 The sensor body according to the present disclosure can also be implemented in other embodiments, in which the first section 10, the second section 20, and the intermediate section 30 are arranged similarly to the embodiments shown in Figure 3 and the embodiments described in Figure 3The difference between the embodiments shown mainly lies in the specific shape of the annular portion. As shown in Figure 4 The annular portion has a trapezoidal shape in a cross-sectional view along the central plane of the sensor body 100. The wall thickness is thinner closer to the central axis of the sensor body and thicker farther away from the central axis of the sensor body. The outer diameter of the sensor body 100 is in the range of 1.5mm-3mm, the length of the sensor body 100 is in the range of 1mm-8mm, and the thickness of the annular portion is in the range of 0.05mm-0.1mm.

[0043] As shown in Figure 5 The annular portion has a parallelogram shape. The first annular portion 41 and the second annular portion 42 are at an acute angle with respect to the transverse direction of the sensor body 100. The acute angle is preferably less than 30°, more preferably less than 15°. By allowing the annular portion to have a controlled inclination angle within a certain range, it can be ensured that the deformation of the first section 10 with respect to the second section 20 mainly occurs in the annular portion. As shown in Figure 6 In a cross-sectional view along the central plane of the sensor body 100, the first annular portion 41 and the second annular portion 42 have an irregular shape, and the first annular portion 41 and the second annular portion 42 are not flat and thin-walled, but have an annular surface composed of curved surfaces. In this embodiment, the size of the gap 40 increases in the direction away from the central axis, and the two axial sides of the gap 40 are defined by curved lines. As shown in Figure 7 This embodiment only has one annular portion, i.e. the first annular portion 41. The second section 20 is directly connected to the intermediate section 30, and the first section 10 is connected to the intermediate section 30 through the annular portion. It can be understood that in an embodiment not shown, the first section 10 can be directly connected to the intermediate section 30, and the second section 20 is connected to the intermediate section 30 through the annular portion. In addition, in an embodiment not shown, the second section can be provided with an outer diameter smaller than that of the first section, or even equal to that of the intermediate section 30.

[0044] As shown in Figure 8As shown, the sensor body 100 comprises a first section, a second section, and a plurality of elastic connecting sections bridging the first section and the second section at a gap, the connecting sections being compressible along the longitudinal axis direction such that the size of the gap 40 changes in response to a change in force applied to the sensor body; the plurality of elastic connecting sections are rotationally spaced apart around the longitudinal axis, and the difference between the rotationally spaced apart angles of the plurality of elastic connecting sections is less than 20°. The elastic connecting sections can be springs, arc-shaped connecting sections, zigzag connecting sections, etc. Due to the difference between the rotationally spaced apart angles of the plurality of elastic connecting sections being less than 20°, the difference in sensitivity to lateral forces in different directions when the sensor body is subjected to a force can be reduced, and the accuracy of the sensor and the interferometric measurement system can be improved.

[0045] In addition, the technical features disclosed above are not limited to the combinations disclosed with other features, and other combinations between the technical features can be made by those skilled in the art according to the purpose of the disclosure, and the purpose of the disclosure shall prevail.

Claims

1. An interferometry system, characterized by, comprising: a light source emitting coherent light; a coupler having a first port, a second port and a third port, the coupler configured to receive the coherent light emitted from the light source via the first port, and split the coherent light into a plurality of beams of coherent light via the second port, and receive a plurality of beams of modulated light modulated by a physical quantity to be measured via the second port; a plurality of sensor devices configured to receive one of the plurality of beams of coherent light via the second port, and form and output the modulated light modulated by the physical quantity to be measured; an interference demodulation device comprising a birefringent element, and configured to receive the plurality of beams of modulated light modulated by the physical quantity to be measured via the third port, and demodulate the plurality of beams of modulated light modulated by the physical quantity to be measured through different segments of the birefringent element to obtain a plurality of interference spectra of the physical quantity to be measured.

2. The interferometry system of claim 1, wherein: the birefringent element is a birefringent wedge having a wedge angle greater than 7°.

3. The interferometry system of claim 1, wherein, a cavity length difference of the plurality of sensor devices is not less than 1 micrometer.

4. The interferometry system of claim 1, wherein, further comprising a sensor body configured to hold the sensor devices, and a dimension of a cavity length of a force sensing cavity of at least one of the sensor devices is varied in response to a force applied to the sensor body.

5. The interferometry system of claim 4, wherein, the sensor body comprises a first section and a second section defining a gap therebetween, the gap being bridged by a connecting section, the connecting section causing a difference in sensitivity of the sensor body to lateral forces in various directions to be within a factor of 2; the force sensing cavity being located in the gap.

6. The interferometry system of claim 5, wherein, at least a portion of an outer surface of the connecting section is recessed inwardly relative to an outer surface of the first section and an outer surface of the second section to form the gap between the first section and the second section; at least one end of the connecting section is connected to the first section or the second section by a ring portion, the ring portion defining at least a portion of an axial boundary of the gap, a thickness of the ring portion being less than a width of a ring face of the ring portion.

7. The interferometry system of claim 6, wherein, the ring portion comprises a first ring portion and a second ring portion, the first ring portion defining a portion of the axial boundary of the gap and connecting a first end of the connecting section to the first section, the second ring portion defining a portion of the axial boundary of the gap and connecting a second end of the connecting section to the second section.

8. The interferometry system of claim 6, wherein, the ring portion extends in a lateral direction perpendicular to the axial direction, or at an angle relative to the lateral direction of between 0 and 15°.

9. The interferometry system of claim 5, wherein, the sensor body defines a longitudinal axis; the first section and the second section are bridged by a plurality of elastic connecting sections, the plurality of elastic connecting sections being rotationally spaced apart about the longitudinal axis, a difference in rotational spacing angle between the plurality of elastic connecting sections being less than 20°.

10. The interferometry system of claim 1, wherein, the interference demodulation device comprises: a condenser configured to receive modulated light; a first polarizer disposed downstream of the condenser and having a first polarization direction; a second polarizer disposed downstream of the first polarizer and having a second polarization direction perpendicular or parallel to the first polarization direction; and a birefringent element located between the first polarizer and the second polarizer and having an optical axis at 45° or -45° to the first polarization direction.

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