Fiber-coupled dynamic interferometer based on arrayed waveguide grating spectrometry

Abstract

This invention relates to a fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting, wherein the light source and the arrayed waveguide grating are arranged in a motion module. The light source is connected to the input port of the arrayed waveguide grating via an optical fiber. The motion module allows any one of the multiple output ports of the arrayed waveguide grating to be connected to an optical fiber at the incident end of a collimating structure. A half-wave plate and a beam splitter prism of the imaging element group are sequentially arranged on the output optical path at the output end of the collimating structure. The beam splitter prism splits the beam passing through the half-wave plate into a reference beam propagating along a first optical path and a measurement beam propagating along a second optical path. A mirror of the imaging element group reflects the reference beam back to the beam splitter prism. The surface under test reflects the measurement beam back to the beam splitter prism. The reference beam and the measurement beam reflected back to the beam splitter prism interfere with each other and are imaged onto the target surface of the camera. This achieves accurate measurement of the wavefront image of the surface under test.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement technology, and in particular relates to a fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting. Background Technology

[0002] With the increasing demands for optical system quality in national economy, scientific research, and national defense, the importance of surface processing and testing of optical components is becoming increasingly prominent. Currently, the wavefront shape testing of planar, spherical, and aspherical optical components can be accomplished using interferometers. Interferometers enable interferometric testing techniques that utilize interference phenomena for detection. Interferometric testing techniques are widely used in various related testing fields due to their advantages such as high precision, high sensitivity, and non-destructive testing. However, the interference optical path of traditional interferometers cannot achieve multi-wavelength, high-precision optical measurement functions. Summary of the Invention

[0003] In view of this, the present invention aims to provide a fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting, which can achieve frequency stabilization and filtering of the wavelength of the light beam emitted by the light source through the arrayed waveguide grating, thereby realizing accurate measurement of the wavefront image of the surface to be measured.

[0004] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0005] A fiber-coupled dynamic interferometer based on beam splitting using an arrayed waveguide grating includes a light source, an arrayed waveguide grating, a motion module, a collimation structure, an imaging element group, and a camera;

[0006] The light source and the arrayed waveguide grating are set in the motion module; the light source is connected to the input port of the arrayed waveguide grating through an optical fiber, and the motion module is used to make any one of the multiple output ports of the arrayed waveguide grating dock with the optical fiber connected to the incident end of the collimation structure.

[0007] The imaging element assembly includes a half-wave plate, a beam splitter, and a reflector. The half-wave plate and the beam splitter are arranged sequentially on the output optical path of the collimating structure. The beam splitter is used to split the beam passing through the half-wave plate into a reference beam that travels along a first optical path and a measurement beam that travels along a second optical path. The reflector is arranged in the first optical path to reflect the reference beam back to the beam splitter. The surface to be measured is arranged in the second optical path to reflect the measurement beam back to the beam splitter. The reference beam and the measurement beam reflected back to the beam splitter interfere with each other and are imaged on the target surface of the camera.

[0008] Furthermore, the motion module includes a drive component and a transmission component. The drive component is used to drive the transmission component to move, so as to move the light source and the arrayed waveguide grating. The transmission component adopts any of the following components: chain drive component, gear and rack component, and lead screw component.

[0009] Furthermore, the imaging element group also includes a first quarter-wave plate, which is arranged in the first optical path and located between the beam splitter and the mirror;

[0010] The reference beam is transmitted through the first quarter-wave plate, then incident on the surface of the mirror, reflected by the mirror, and then passes through the first quarter-wave plate again to return to the beam splitter.

[0011] Furthermore, the imaging element group also includes a second quarter-wave plate, which is arranged in the second optical path and located between the beam splitter and the surface to be measured;

[0012] The measurement beam is transmitted through the second quarter-wave plate and then incident on the surface to be measured. After being reflected by the surface to be measured, it passes through the second quarter-wave plate again and returns to the beam splitter.

[0013] Furthermore, the imaging element group also includes a converging lens, which is arranged in the second optical path and located between the second quarter-wave plate and the surface to be measured;

[0014] The measurement beam is transmitted through the second quarter-wave plate, then through the converging lens to the surface to be measured. After being reflected by the surface to be measured, it passes through the converging lens and the second quarter-wave plate again and returns to the beam splitter.

[0015] Furthermore, the imaging element assembly also includes a third quarter-wave plate, which is located between the beam splitter and the camera;

[0016] The reference beam and the measurement beam reflected back to the beam splitter are combined by the beam splitter and then pass through the third quarter-wave plate, causing the reference beam and the measurement beam to interfere with each other and be imaged on the target surface of the camera.

[0017] Furthermore, the wavelength spacing of the arrayed waveguide grating ranges from 0.01 nm to 0.1 nm.

[0018] Furthermore, the camera is a polarizing mask camera.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0020] This invention presents a fiber-coupled dynamic interferometer based on arrayed waveguide grating (ARG) beam splitting. The ARG enables frequency stabilization and selection of the wavelength of the light beam emitted from a light source, thereby achieving precise measurement of the wavefront image of the surface under test. Specifically, the light beam emitted from the light source is diffracted and split by the ARG, allowing beams of different wavelengths to be output through different output channels of the ARG. Thus, each output port of the ARG can output a narrow-linewidth, wavelength-stable beam. Furthermore, the light source and ARG are mounted in a motion module. This module moves the light source and ARG, switching the output port of the ARG connected to the fiber optic cable at the incident end of the collimation structure. Different output ports of the ARG can output beams of different wavelengths, enabling rapid multi-wavelength measurements using the motion module, resulting in higher accuracy in obtaining the wavefront image of the surface under test. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0022] Figure 1 This is an optical structure diagram of the fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting described in an embodiment of the present invention.

[0023] Explanation of reference numerals in the attached figures:

[0024] 10 Fiber-coupled dynamic interferometer; 11 Light source; 12 Arrayed waveguide grating; 13 Collimation structure; 14 Imaging element group; 15 Camera; 16 Surface to be measured; 17 Half-wave plate; 18 Beam splitter; 19 First quarter-wave plate; 20 Reflector; 21 Second quarter-wave plate; 22 Converging lens; 23 Third quarter-wave plate. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0027] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] See Figure 1 As shown in the figure, this invention provides a fiber-coupled dynamic interferometer 10 based on arrayed waveguide grating beam splitting, which can perform wavefront shape detection of optical elements. The fiber-coupled dynamic interferometer 10 includes a light source 11, an arrayed waveguide grating 12, a motion module (not shown in the figure), a collimation structure 13, an imaging element group 14, and a camera 15.

[0031] A light source 11 and an arrayed waveguide grating 12 are disposed in a motion module. The light source 11 can refer to a component that emits a light beam, such as an LED light source or a laser. The light source 11 is connected to the input port of the arrayed waveguide grating 12 via an optical fiber. The light beam from the light source 11 enters the input port of the arrayed waveguide grating 12, and after diffraction and splitting by the arrayed waveguide grating 12, beams of different wavelengths are output through different output channels of the arrayed waveguide grating 12, each output channel corresponding to an output port. That is, the arrayed waveguide grating 12 has multiple output ports, and different output ports can output beams of different wavelengths. In one embodiment, the wavelength spacing of the arrayed waveguide grating 12 ranges from 0.01 nm to 0.1 nm. In this embodiment, the wavelength spacing of the arrayed waveguide grating 12 is 0.01 nm, that is, the wavelength difference between adjacent output channels is 0.01 nm. The motion module allows any one of the multiple output ports of the arrayed waveguide grating 12 to be connected to the optical fiber connected to the incident end of the collimation structure 13. The motion module can move the light source 11 and the arrayed waveguide grating 12, and can also move the light source 11 and the arrayed waveguide grating 12 laterally to switch different output channels of the arrayed waveguide grating 12, so that different output ports are connected to the optical fiber connected to the incident end of the collimation structure 13. The light beam output from the output port of the arrayed waveguide grating 12 can be coupled into the optical fiber connected to the incident end of the collimation structure 13, and pass through the collimation structure 13 to output a collimated light beam. The collimation structure 13 can be an optical fiber collimator.

[0032] The imaging element assembly 14 includes a waveplate 17, a beam splitter 18, and a reflector 20. The waveplate 17 and the beam splitter 18 are sequentially arranged on the output optical path of the collimating structure 13. The beam splitter 18 is used to split the light beam passing through the waveplate 17 into a reference beam that travels along a first optical path and a measurement beam that travels along a second optical path. In this embodiment, the collimated beam output from the collimating structure 13 passes through the waveplate 17 and is incident on the beam splitter 18, where it is split into two beams with mutually perpendicular polarization directions: a P-beam that travels along the first optical path as the reference beam and an S-beam that travels along the second optical path as the measurement beam. The reflector 20 is arranged in the first optical path to reflect the reference beam back to the beam splitter 18. The surface to be measured 16 is arranged in the second optical path to reflect the measurement beam back to the beam splitter 18. The reference beam and the measurement beam reflected back to the beam splitter 18 interfere with each other and are imaged onto the target surface of the camera 15.

[0033] The fiber-coupled dynamic interferometer 10 based on arrayed waveguide grating diffraction created in this invention can achieve frequency stabilization and filtering of the wavelength of the light beam emitted by the light source 11 through the arrayed waveguide grating 12, thereby realizing accurate measurement of the wavefront image of the surface 16 under test. Precise control of the wavelength of the light beam emitted by the light source 11 provides a basis for surface shape detection of the optical element's surface 16. Specifically, the light beam emitted by the light source 11 is diffracted and split by the arrayed waveguide grating 12, allowing beams of different wavelengths to be output through different output channels of the arrayed waveguide grating 12. Therefore, each output port of the arrayed waveguide grating 12 can output a narrow-linewidth, wavelength-stable beam. Furthermore, the light source 11 and the arrayed waveguide grating 12 are set in the motion module. Through the motion module, the light source 11 and the arrayed waveguide grating 12 can be moved to switch the output port of the arrayed waveguide grating 12 connected to the optical fiber at the incident end of the collimation structure 13. Different output ports of the arrayed waveguide grating 12 can output beams of different wavelengths. Thus, the motion module can be used to realize multi-wavelength rapid measurement, thereby obtaining a higher accuracy wavefront image of the surface 16 under test.

[0034] This invention creates a rapid vibration-resistant measurement capability based on the dynamic interferometer itself and the high-resolution wavelength separation characteristics of the arrayed waveguide grating 12, which can solve the problems of single wavelength limitation and insufficient adaptability of multi-wavelength dynamic measurement in the prior art, and fill the technical gap in high dynamic multi-wavelength measurement systems.

[0035] In one embodiment, the imaging element assembly 14 further includes a first quarter-wave plate 19, which is arranged in the first optical path and located between the beam splitter prism 18 and the reflector 20. The reference beam, after passing through the first quarter-wave plate 19, is incident on the surface of the reflector 20, reflected by the reflector 20, and then returns to the beam splitter 18 via the first quarter-wave plate 19. In this embodiment, the P-light propagating along the first optical path serves as the reference beam. After passing through the first quarter-wave plate 19, it is converted into right-handed polarized light, incident on the surface of the reflector 20, reflected by the reflector 20, and then modulated into S-light via the first quarter-wave plate 19.

[0036] In one embodiment, the imaging element group 14 further includes a second quarter-wave plate 21, which is arranged in the second optical path and located between the beam splitter 18 and the surface under test 16. The measurement beam is transmitted through the second quarter-wave plate 21, incident on the surface under test 16, reflected by the surface under test 16, and then returns to the beam splitter 18 through the second quarter-wave plate 21.

[0037] In one embodiment, the imaging element group 14 further includes a converging lens 22. The converging lens 22 can be a quartz glass lens or a lens made of other materials; this application is not limited to any particular material. The converging lens 22 is arranged in the second optical path and located between the second quarter-wave plate 21 and the surface to be measured 16. The measurement beam, after passing through the second quarter-wave plate 21, passes through the converging lens 22 and is incident on the surface to be measured 16. After being reflected by the surface to be measured 16, it passes through the converging lens 22 and the second quarter-wave plate 21 again before returning to the beam splitter 18. In this embodiment, the S-beam transmitted along the second optical path serves as the measurement beam. After passing through the second quarter-wave plate 21, it is converted into left-handed polarized light, passes through the converging lens 22 and is incident on the surface to be measured 16. After being reflected by the surface to be measured 16, it passes through the converging lens 22 and the second quarter-wave plate 21 again, and is modulated into P-beam by the second quarter-wave plate 21.

[0038] In one embodiment, the imaging element assembly 14 further includes a third quarter-wave plate 23, located between the beam splitter 18 and the camera 15. The reference beam and the measurement beam reflected back to the beam splitter 18 are combined by the beam splitter 18 and then pass through the third quarter-wave plate 23, causing the reference beam and the measurement beam to interfere with each other and be imaged onto the target surface of the camera 15. In this embodiment, the modulated S-beam (reference beam) and the P-beam (measurement beam) return to the beam splitter 18 and are combined, then pass through the third quarter-wave plate 23. This converts the S-beam (reference beam) into right-handed polarized light and the P-beam (measurement beam) into left-handed polarized light, causing the reference beam and the measurement beam to interfere with each other, capturing the interference image, and imaged onto the target surface of the camera 15.

[0039] In this embodiment, the half-wave plate 17 and the second quarter-wave plate 21 are located on opposite sides of the beam splitter 18 along the first direction, and the first quarter-wave plate 19 and the third quarter-wave plate 23 are located on opposite sides of the beam splitter 18 along the second direction; wherein, the first direction is the direction along the second optical path, and the first direction is perpendicular to the second direction.

[0040] In one embodiment, camera 15 is a polarization mask camera. The polarization mask camera can acquire four interference images with different phases in real time and send them to a computer for processing. The computer can obtain the wavefront image of the surface under test 16 at the current wavelength through a four-step phase-shifting solution. By using a motion module to connect different output ports of the arrayed waveguide grating 12 to the optical fiber connected to the incident end of the collimation structure 13, multiple wavefront images of the surface under test 16 at different wavelengths can be obtained. The computer can process these multiple wavefront images to obtain the wavefront image of the surface under test 16, thereby achieving accurate measurement of the wavefront image of the surface under test 16.

[0041] In one embodiment, the motion module includes a drive component and a transmission component. The drive component drives the transmission component to move, thereby moving the light source 11 and the arrayed waveguide grating 12. The drive component can be a motor or similar structure. The transmission component can be any of the following: a chain drive, a rack and pinion assembly, a lead screw and nut assembly, etc. The specific structure of the transmission component is not limited in this invention; it can be implemented by connecting any one of the multiple output ports of the arrayed waveguide grating 12 to the optical fiber connected to the incident end of the collimation structure 13.

[0042] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0043] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting, characterized in that, It includes a light source, an arrayed waveguide grating, a motion module, a collimation structure, an imaging element group, and a camera; The light source and the arrayed waveguide grating are disposed in the motion module; the light source is connected to the input port of the arrayed waveguide grating via an optical fiber, and the motion module is used to connect any one of the multiple output ports of the arrayed waveguide grating to the optical fiber connected to the incident end of the collimation structure. The imaging element assembly includes a half-wave plate, a beam splitter, and a reflector. The half-wave plate and the beam splitter are sequentially arranged on the output optical path of the collimating structure. The beam splitter is used to split the light beam passing through the half-wave plate into a reference beam that propagates along a first optical path and a measurement beam that propagates along a second optical path. The reflector is arranged in the first optical path to reflect the reference beam back to the beam splitter. The surface to be measured is arranged in the second optical path to reflect the measurement beam back to the beam splitter. The reference beam and the measurement beam reflected back to the beam splitter interfere with each other and are imaged on the target surface of the camera.

2. The fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting according to claim 1, characterized in that, The motion module includes a drive component and a transmission component. The drive component is used to drive the transmission component to move, so as to move the light source and the arrayed waveguide grating. The transmission component adopts any of the following components: chain drive component, gear and rack component, and lead screw and nut component.

3. The fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting according to claim 1, characterized in that, The imaging element group further includes a first quarter-wave plate, which is arranged in the first optical path and located between the beam splitter and the reflector; The reference beam is transmitted through the first quarter-wave plate, then incident on the surface of the reflector, and after being reflected by the reflector, it passes through the first quarter-wave plate again and returns to the beam splitter.

4. The fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting according to claim 1, characterized in that, The imaging element group further includes a second quarter-wave plate, which is arranged in the second optical path and located between the beam splitter and the surface to be measured. The measurement beam is transmitted through the second quarter-wave plate and then incident on the surface to be measured. After being reflected by the surface to be measured, it passes through the second quarter-wave plate again and returns to the beam splitter.

5. The fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting according to claim 4, characterized in that, The imaging element group further includes a converging lens, which is arranged in the second optical path and located between the second quarter-wave plate and the surface to be measured; The measurement beam is transmitted through the second quarter-wave plate, then through the converging lens and incident on the surface to be measured. After being reflected by the surface to be measured, it passes through the converging lens and the second quarter-wave plate again and returns to the beam splitter.

6. The fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting according to claim 1, characterized in that, The imaging element group further includes a third quarter-wave plate, which is located between the beam splitter and the camera; The reference beam and the measurement beam reflected back to the beam splitter are combined by the beam splitter and then pass through the third quarter-wave plate, causing the reference beam and the measurement beam to interfere with each other and be imaged on the target surface of the camera.

7. The fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting according to claim 1, characterized in that, The wavelength spacing of the arrayed waveguide grating ranges from 0.01 nm to 0.1 nm.

8. The fiber-coupled dynamic interferometer based on arrayed waveguide grating beam splitting according to claim 1, characterized in that, The camera is a polarization mask camera.

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