Interferometer mirror group and displacement measurement system

Abstract

The present application relates to the technical field of optical system, and provides an interferometer lens and a displacement measurement system, the interferometer lens comprises a first polarization beam splitting element, a second polarization beam splitting element, a first polarization state conversion reflection assembly, a second polarization state conversion reflection assembly and a target polarization state conversion element, the first signal light can be incident to the target reflection element twice and output after reflection by means of the first polarization beam splitting element and the second polarization beam splitting element, the second signal light can be output after reflection twice by means of the first polarization state conversion reflection assembly and the second polarization state conversion reflection assembly, the interferometer with 4 optical subdivision numbers is realized, and the resolution of the interferometer is improved. The vertical direction of the target reflection element is the vertical direction of the interferometer lens, the interferometer lens can also increase the vertical travel of the first signal light between the interferometer lens and the target reflection element, which is helpful to realize the vertical displacement measurement range and meet the displacement measurement range requirement of the worktable of the lithography machine.

Description

Technical Field

[0001] This invention relates to the field of optical system technology, and in particular to an interferometer lens assembly and a displacement measurement system. Background Technology

[0002] Currently, the requirements for positioning accuracy and measurement range of grating precision measurement systems are constantly increasing, especially in the high-end ultra-precision instrument industry such as lithography machines, where the requirements for measurement accuracy and range are even higher. With technological development, various principles and forms of displacement measurement technology have emerged, such as grating rulers, capacitance measurement, grating interferometry, and laser interferometry. However, because grating interferometers achieve displacement measurement through the diffraction of gratings and the interference of light, they have a greater advantage in sub-nanometer level measurement compared to other displacement measurement technologies.

[0003] The resolution of a grating interferometer is a key indicator in displacement measurement systems, directly affecting the measurement accuracy of the system and the manufacturing precision of the lithography machine using it. Therefore, further improving the resolution of grating interferometers remains a critical task. However, existing grating interferometers have a small optical subdivision number, resulting in low resolution and thus hindering their future applications.

[0004] Therefore, there is an urgent need to provide an interferometer mirror assembly that can be applied to displacement measurement systems. Summary of the Invention

[0005] This invention provides an interferometer mirror assembly and a displacement measurement system to address the deficiencies in the prior art.

[0006] This invention provides an interferometer mirror assembly, comprising: a first polarization beam splitter, a second polarization beam splitter, a first polarization state conversion and reflection assembly, a second polarization state conversion and reflection assembly, and a target polarization state conversion element; wherein,

[0007] The first signal light passes sequentially through the first polarization beam splitter and the target polarization state conversion element before being incident on the target reflection element. It then passes through the target reflection element and the target polarization state conversion element before being incident on the first polarization beam splitter. Finally, it passes sequentially through the first polarization beam splitter, the second polarization beam splitter, the target polarization state conversion element, the target reflection element, the target polarization state conversion element, and the second polarization beam splitter before being output.

[0008] The second signal light is output after passing through the first polarization beam splitter, the first polarization state conversion and reflection component, the first polarization beam splitter, the second polarization beam splitter, the second polarization state conversion and reflection component, and the second polarization beam splitter in sequence;

[0009] The first signal light and the second signal light are linearly polarized lights with orthogonal polarization states, and they have the same incident point on the first polarization beam splitter.

[0010] An interferometer mirror assembly according to the present invention further includes: an optical path extension component, wherein the optical path extension component includes an extension reflection element, a third polarization beam splitter element and a fourth polarization beam splitter element;

[0011] The first signal light, after being output from the second polarization beam splitter, is incident on the extended reflector to obtain the first reflected light. The first reflected light is then incident on the target reflector after passing through the third polarization beam splitter and the target polarization state conversion element in sequence. After being reflected by the target reflector, it is then output after passing through the target polarization state conversion element, the third polarization beam splitter, the fourth polarization beam splitter, the target polarization state conversion element, the target reflector, the target polarization state conversion element, and the fourth polarization beam splitter in sequence.

[0012] The second signal light is output after passing through the first polarization beam splitter, the first polarization state conversion and reflection component, the first polarization beam splitter, the second polarization beam splitter, the third polarization beam splitter, the fourth polarization beam splitter, the second polarization state conversion and reflection component, and the fourth polarization beam splitter in sequence.

[0013] According to an interferometer mirror assembly provided by the present invention, the optical path extension component includes multiple components;

[0014] For any optical path extension component other than the first optical path extension component, the first signal light, after passing through the beam output from the preceding optical path extension component, is incident on the optical path extension component, and sequentially passes through the extended reflection element, the third polarization beam splitter, and the target polarization state conversion element in the optical path extension component before being incident on the target reflection element. After being reflected by the target reflection element, it sequentially passes through the target polarization state conversion element, the third polarization beam splitter, the fourth polarization beam splitter, the target polarization state conversion element, the target reflection element, the target polarization state conversion element, and the fourth polarization beam splitter before being output.

[0015] The second signal light, after passing through the beam output from the previous optical path extension component, is incident on any of the optical path extension components, and then, after passing through the third and fourth polarization beam splitters in the optical path extension components, is incident on the second polarization state conversion reflection component, and is output after passing through the fourth polarization beam splitter in the optical path extension component.

[0016] According to an interferometer mirror assembly provided by the present invention, the extended reflective element is a cornerstone prism.

[0017] According to an interferometer lens assembly provided by the present invention, the first polarization beam splitter, the second polarization beam splitter, the first polarization state conversion reflection component, the second polarization state conversion reflection component, and the target polarization state conversion component are attached in the optical path transmission direction.

[0018] According to an interferometer mirror assembly provided by the present invention, both the first polarization state conversion and reflection assembly and the second polarization state conversion and reflection assembly include a polarization state conversion element and a reflection element, and the polarization state conversion element is located in front of the reflection element.

[0019] According to an interferometer mirror assembly provided by the present invention, the target reflective element is a diffraction grating; the incident angle of the first signal light on the diffraction grating is the Littoral angle.

[0020] According to an interferometer lens assembly provided by the present invention, the first signal light and the second signal light are orthogonally linearly polarized light signals with the same frequency, or orthogonally linearly polarized light signals with different frequencies.

[0021] An interferometer mirror assembly provided by the present invention further includes a fifth polarization beam splitter element;

[0022] The first signal light obtained after the first beam passes through the fifth polarization beam splitter is incident on the first polarization beam splitter.

[0023] The second signal light obtained after the second beam passes through the fifth polarization beam splitter is incident on the first polarization beam splitter.

[0024] Both the first beam and the second beam are generated based on a laser light source.

[0025] The present invention also provides a displacement measurement system, including a laser source, a processing component, a target reflective element, and the interferometer mirror assembly described above;

[0026] The laser source is used to generate the first beam and the second beam, and inputs the first beam and the second beam into the interferometer mirror group;

[0027] The processing component is used to receive the output signal of the interferometer mirror group and determine the displacement information of the target reflective element based on the output signal.

[0028] According to the displacement measurement system provided by the present invention, the interferometer mirror group includes a first interferometer mirror group and a second interferometer mirror group;

[0029] The first signal light obtained after the first beam passes through the fifth polarization beam splitter is incident on the first interferometer mirror group, and the second signal light obtained is incident on the second interferometer mirror group;

[0030] The first signal light obtained after the second beam passes through the fifth polarization beam splitter is incident on the second interferometer mirror group, and the second signal light obtained is incident on the first interferometer mirror group.

[0031] The interferometer lens assembly and displacement measurement system provided by this invention include a first polarization beam splitter, a second polarization beam splitter, a first polarization state conversion and reflection assembly, a second polarization state conversion and reflection assembly, and a target polarization state conversion element. The first signal light, aided by the first and second polarization beam splitters, can be incident on the target reflection element twice and reflected before being output. The second signal light, aided by the first and second polarization state conversion and reflection assemblies, can be reflected twice before being output. This enables an interferometer with 4 optical subdivisions, thereby improving the interferometer's resolution. With the vertical direction of the target reflection element as the vertical direction of the interferometer lens assembly, the interferometer lens assembly can also increase the vertical travel of the first signal light between the interferometer lens assembly and the target reflection element, thus facilitating the vertical displacement measurement range and meeting the displacement measurement range requirements of a lithography machine workpiece stage. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on the drawings described below without creative effort.

[0033] Figure 1 This is one of the structural schematic diagrams of the interferometer mirror assembly provided by the present invention;

[0034] Figure 2 This is the second schematic diagram of the interferometer mirror assembly provided by the present invention;

[0035] Figure 3 This is the third schematic diagram of the interferometer mirror assembly provided by the present invention;

[0036] Figure 4 This is the fourth schematic diagram of the interferometer mirror assembly provided by the present invention;

[0037] Figure 5 This is one of the structural schematic diagrams of the displacement measurement system provided by the present invention;

[0038] Figure 6 This is the second schematic diagram of the displacement measurement system provided by the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] The terms "first" and "second" in the specification and claims of this invention may explicitly or implicitly include one or more of those features. In the description of the invention, unless otherwise stated, "a plurality of" means two or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0041] Existing grating interferometers suffer from drawbacks such as small vertical travel, limited angular deflection tolerance, low optical subdivision number, and low resolution, hindering their subsequent applications. Therefore, this invention provides an interferometer mirror assembly applicable to displacement measurement systems. This assembly boasts advantages such as large vertical travel, large angular deflection tolerance, high optical subdivision number, and high resolution. It can be either a grating interferometer mirror assembly or other types of interferometer mirror assemblies, making the displacement measurement system structure more flexible.

[0042] Figure 1 This is a schematic diagram of the process of an interferometer mirror assembly provided in an embodiment of the present invention, such as... Figure 1 As shown, the interferometer mirror assembly includes: a first polarization beam splitter 1, a second polarization beam splitter 2, a first polarization state conversion and reflection assembly 3, a second polarization state conversion and reflection assembly 4, and a target polarization state conversion element 5; wherein,

[0043] The first signal light passes sequentially through the first polarization beam splitter 1 and the target polarization state conversion element 5 before being incident on the target reflection element 6. It then passes through the target reflection element 6 and the target polarization state conversion element 5 before being incident on the first polarization beam splitter 1. Finally, it passes sequentially through the first polarization beam splitter 1, the second polarization beam splitter 2, the target polarization state conversion element 5, the target reflection element 6, the target polarization state conversion element 5, and the second polarization beam splitter 2 before being output.

[0044] The second signal light is output after passing through the first polarization beam splitter 1, the first polarization state conversion and reflection component 3, the first polarization beam splitter 1, the second polarization beam splitter 2, the second polarization state conversion and reflection component 4, and the second polarization beam splitter 2 in sequence.

[0045] The first signal light and the second signal light are linearly polarized lights with orthogonal polarization states, and they have the same incident point on the first polarization beam splitter 1.

[0046] Specifically, the interferometer mirror assembly provided in this embodiment of the invention may include a first polarization beam splitter 1, a second polarization beam splitter 2, a first polarization state conversion reflection component 3, a second polarization state conversion reflection component 4, and a target polarization state conversion element 5. Both the first polarization beam splitter 1 and the second polarization beam splitter 2 can be optical elements with polarization beam splitting function, such as polarization beam splitters, beam splitters, etc. The beam splitting surfaces of the first polarization beam splitter 1 and the second polarization beam splitter 2 can be perpendicular.

[0047] Both the first polarization state conversion reflective component 3 and the second polarization state conversion reflective component 4 can be combinations of optical elements with polarization state conversion and reflection functions, used to receive light of one polarization state and output light of another polarization state, for example, receiving p-light and outputting s-light. The target polarization state conversion element 5 can be an optical element with polarization conversion function, such as a quarter-wave plate, which converts linearly polarized light into circularly polarized or elliptically polarized light, and can also convert circularly polarized or elliptically polarized light into linearly polarized light. The target reflection element 6 can be an optical element with reflection function, such as a mirror.

[0048] On one hand, the first signal light f1 is incident on the first polarization beam splitter 1, and sequentially passes through the first polarization beam splitter 1, the target polarization state conversion element 5, the target reflection element 6, the target polarization state conversion element 5, the first polarization beam splitter 1, the second polarization beam splitter 2, the target polarization state conversion element 5, the target reflection element 6, the target polarization state conversion element 5, and the second polarization beam splitter 2 before being output. Here, the first signal light can be linearly polarized light, for example, p-light. Both the first polarization beam splitter 1 and the second polarization beam splitter 2 can transmit p-light and reflect s-light. The target polarization state conversion element 5 can convert the first signal light from one polarization state to another after passing through it twice, and the target reflection element 6 can deflect the transmission direction of the first signal light by 180 degrees, so that the first signal light can pass through the target polarization state conversion element 5 twice to achieve different polarization state conversions.

[0049] Using the target reflective element 6 as a movable object, the output corresponding to the first signal light can be marked as the measurement light signal, based on whether the light beam is incident on the target reflective element 6. In this case, the transmission path of the first signal light can constitute the measuring arm of the interferometer mirror assembly.

[0050] Due to the presence of the first polarization beam splitter 1 and the second polarization beam splitter 2, the measurement optical signal can be obtained by the first signal light passing through the target reflective element 6 twice and being reflected. The interferometer mirror group can have 4 optical subdivisions and a resolution of λ / 4.

[0051] On the other hand, the second signal light f2 is incident on the first polarization beam splitter 1, and sequentially passes through the first polarization beam splitter 1, the first polarization state conversion and reflection component 3, the first polarization beam splitter 1, the second polarization beam splitter 2, the second polarization state conversion and reflection component 4, and the second polarization beam splitter 2 before being output. To separate the first signal light from the second signal light, the polarization state of the second signal light can be orthogonal to that of the first signal light; here, the second signal light is an s-ray.

[0052] Due to the presence of the first polarization state conversion reflection component 3 and the second polarization state conversion reflection component 4, the second signal light can be output after two reflections. The second signal light can be marked as the reference light signal. At this time, the transmission path of the second signal light constitutes the reference arm of the interferometer mirror group.

[0053] Figure 1 In the diagram, solid arrows indicate the transmission direction and path of the first signal light f1, while dashed arrows indicate the transmission direction and path of the second signal light f2.

[0054] Since the first signal light and the second signal light have the same incident point on the first polarization beam splitter 1, the output corresponding to the first signal light and the output corresponding to the second signal light also have the same exit point on the second polarization beam splitter 2.

[0055] Subsequently, the reference light signal and the measurement light signal can be mixed to generate an interference signal. This interference signal can be incident on a phase detector to determine the phase information of the interference signal, and then the displacement of the target reflective element 6 can be determined through this phase information, thereby realizing the displacement measurement of the target reflective element 6.

[0056] The interferometer mirror assembly provided in this embodiment of the invention includes a first polarization beam splitter, a second polarization beam splitter, a first polarization state conversion and reflection assembly, a second polarization state conversion and reflection assembly, and a target polarization state conversion element. The first signal light, with the aid of the first and second polarization beam splitters, can be incident on the target reflection element twice and reflected before being output. The second signal light, with the aid of the first and second polarization state conversion and reflection assemblies, can be reflected twice before being output. This enables an interferometer with 4 optical subdivisions, thereby improving the interferometer's resolution. Taking the vertical direction of the target reflection element as the vertical direction of the interferometer mirror assembly, the interferometer mirror assembly can also increase the vertical travel of the first signal light between the interferometer mirror assembly and the target reflection element, thus helping to achieve a wider vertical displacement measurement range, which can meet the displacement measurement range requirements of the lithography machine workpiece stage.

[0057] Based on the above embodiments, both the first polarization state conversion reflection component and the second polarization state conversion reflection component include a polarization state conversion element and a reflection element, and the polarization state conversion element is located in front of the reflection element.

[0058] Specifically, such as Figure 2 As shown, in Figure 1 Based on this, the first polarization state conversion and reflection assembly 3 may include a first polarization state conversion element 31 and a first reflection element 32, and the second polarization state conversion and reflection assembly 4 may include a second polarization state conversion element 41 and a second reflection element 42. Both the first polarization state conversion element 31 and the second polarization state conversion element 41 may be quarter-wave plates, and both the first reflection element 32 and the second reflection element 42 may be mirrors.

[0059] After the first signal light enters the first polarization beam splitter 1, it passes directly through the first polarization beam splitter 1 and exits. After passing through the target polarization state conversion element 5, it is formed into right-handed or left-handed circularly polarized light and is incident on the target reflector 6. After being reflected by the target reflector 6, it is converted into s-light again by the target polarization state conversion element 5. This s-light enters the first polarization beam splitter 1 and is reflected to the second polarization beam splitter 2. During this process, beam subdivision occurs. In the second polarization beam splitter 2, the s-light continues to be reflected, passes through the target polarization state conversion element 5, and is incident on the target reflector 6. After being reflected by the target reflector 6, it is converted into p-light by the target polarization state conversion element 5. The p-light is then directly transmitted and output from the second polarization beam splitter 2.

[0060] After the second signal light enters the first polarization beam splitter 1, it is reflected to the right. After passing through the first polarization state conversion element 31, it becomes left-handed or right-handed circularly polarized light. Then, after being reflected by the first reflection element 32, it is converted into p-light again by the first polarization state conversion element 31. It then directly transmits through the first polarization beam splitter 1 and the second polarization beam splitter 2 and is incident on the second polarization state conversion element 41. There, it is converted from p-light to left-handed or right-handed circularly polarized light and is incident on the second reflection element 42. After being reflected by the second reflection element 42, it is converted into s-light again by the second polarization state conversion element 41 and is reflected and output in the second polarization beam splitter 2.

[0061] In this embodiment of the invention, the polarization state conversion function of p-light and s-light can be realized by combining a quarter-wave plate with a reflecting element. The structure is simple and easy to implement.

[0062] like Figure 3 As shown, based on the above embodiments, the interferometer mirror assembly provided in this embodiment of the invention further includes: an optical path extension component, which includes an extension reflection element 7, a third polarization beam splitter element 8, and a fourth polarization beam splitter element 9;

[0063] The first signal light, after being output by the second polarization beam splitter 2, is incident on the extended reflector 7 to obtain the first reflected light. The first reflected light is then incident on the target reflector 6 after passing through the third polarization beam splitter 8 and the target polarization state conversion element 5 in sequence. After being reflected by the target reflector 6, it is then output after passing through the target polarization state conversion element 5, the third polarization beam splitter 8, the fourth polarization beam splitter 9, the target polarization state conversion element 5, the target reflector 6, the target polarization state conversion element 5, and the fourth polarization beam splitter 9 in sequence.

[0064] The second signal light is output after passing through the first polarization beam splitter 1, the first polarization state conversion and reflection component 3, the first polarization beam splitter 1, the second polarization beam splitter 2, the third polarization beam splitter 8, the fourth polarization beam splitter 9, the second polarization state conversion and reflection component 4, and the fourth polarization beam splitter 9 in sequence.

[0065] Specifically, the interferometer mirror assembly provided in this embodiment of the invention may further include an optical path extension component, which may include an extended reflection element 7, a third polarization beam splitter 8, and a fourth polarization beam splitter 9. The extended reflection element 7 may be an optical element with a reflection function, such as a retroreflector. The third polarization beam splitter 8 and the fourth polarization beam splitter 9 may be the same as the first polarization beam splitter 1 and the second polarization beam splitter 2, both of which can transmit p-light and reflect s-light.

[0066] The first signal light is transmitted through the first polarization beam splitter 1 to the target polarization state conversion element 5. The target polarization state conversion element 5 converts the p-light into right-handed or left-handed circularly polarized light and incident on the target reflection element 6. The target reflection element 6 reflects the light back to the target polarization state conversion element 5, which converts the right-handed or left-handed circularly polarized light into s-light and incident on the first polarization beam splitter 1. The light is then reflected by the first polarization beam splitter 1 to the second polarization beam splitter 2 and further reflected back to the target polarization state conversion element 5. The target polarization state conversion element 5 converts the s-light into right-handed or left-handed circularly polarized light and incident on the target reflection element 6 for reflection. The reflected light reaches the target polarization state conversion element 5, which converts the right-handed or left-handed circularly polarized light into p-light and incident on the second polarization beam splitter 2. The light is then transmitted and output through the second polarization beam splitter 2.

[0067] The beam output from the second polarization beam splitter 2 is incident on the extended reflector 7 to obtain the first reflected light, which is p-beam. The first reflected light is transmitted through the third polarization beam splitter 8 to the target polarization state conversion element 5. The target polarization state conversion element 5 converts the p-beam into right-handed or left-handed circularly polarized light and it is incident on the target reflector 6. The target reflector 6 reflects the light back to the target polarization state conversion element 5. The target polarization state conversion element 5 converts the right-handed or left-handed circularly polarized light into s-beam and it is incident on the third polarization beam splitter 8. The third polarization beam splitter 8 reflects the light back to the fourth polarization beam splitter 9 and it is reflected back to the target polarization state conversion element 5. The target polarization state conversion element 5 converts the s-beam into right-handed or left-handed circularly polarized light and it is incident on the target reflector 6 for reflection. The reflected light reaches the target polarization state conversion element 5. The target polarization state conversion element 5 converts the right-handed or left-handed circularly polarized light back into p-beam and it is incident on the fourth polarization beam splitter 9. The light is then transmitted and output through the fourth polarization beam splitter 9.

[0068] The second signal light is sequentially passed through the first polarization beam splitter 1, the first polarization state conversion element 31, the first reflection element 32, the first polarization state conversion element 31, the first polarization beam splitter 1, the second polarization beam splitter 2, the third polarization beam splitter 8, the fourth polarization beam splitter 9, the second polarization state conversion element 41, the second reflection element 42, the second polarization state conversion element 41, and the fourth polarization beam splitter 9 in the second polarization state conversion reflection assembly 4 before being output.

[0069] Due to the introduction of the optical path extension component, the measurement optical signal can be obtained by the first signal light passing through four incident points to the target reflective element 6 and being reflected before being output. The interferometer mirror group can have 8 optical subdivisions and a resolution of λ / 8.

[0070] In this embodiment of the invention, the introduction of the extended reflective element can increase the vertical travel of the first signal light, further increasing the optical subdivision number of the interferometer mirror group and improving the resolution of the interferometer mirror group. Moreover, since the target reflective element does not cause the angle between the measuring arm and the reference arm when it is displaced, a larger angular deflection can be allowed, thus increasing the allowable amount of angular deflection.

[0071] Based on the above embodiments, the interferometer mirror assembly provided in this embodiment of the invention includes multiple optical path extension components;

[0072] For any optical path extension component other than the first optical path extension component, the first signal light, after passing through the beam output from the preceding optical path extension component, is incident on the optical path extension component, and sequentially passes through the extended reflection element, the third polarization beam splitter, and the target polarization state conversion element in the optical path extension component before being incident on the target reflection element. After being reflected by the target reflection element, it sequentially passes through the target polarization state conversion element, the third polarization beam splitter, the fourth polarization beam splitter, the target polarization state conversion element, the target reflection element, the target polarization state conversion element, and the fourth polarization beam splitter before being output.

[0073] The second signal light, after passing through the beam output from the previous optical path extension component, is incident on any of the optical path extension components, and then, after passing through the third and fourth polarization beam splitters in the optical path extension components, is incident on the second polarization state conversion reflection component, and is output after passing through the fourth polarization beam splitter in the optical path extension component.

[0074] Specifically, the interferometer mirror assembly may also include multiple optical path extension components. In this case, the beam output from the second polarization beam splitter 2 after the first signal light is incident on the target reflective element four times in succession is not directly used as the measurement light signal, but continues to be input to the next optical path extension component. The preceding optical path extension component refers to the one closest to the first polarization beam splitter, and the current optical path extension component refers to the one adjacent to the preceding optical path extension component and far from the first polarization beam splitter.

[0075] Each additional optical path extension component increases the number of times the first signal light is incident on and reflected from the target reflector by 2. If there are 2 optical path extension components, the first signal light can be incident on and reflected from the target reflector 6 times. Thus, the interferometer mirror group can have 12 optical subdivisions and a resolution of λ / 12. Therefore, the number N of optical path extension components in the interferometer mirror group determines the optical subdivision a of the interferometer mirror group, specifically a = 4(N+1).

[0076] The second signal light, after passing through the beam output from the preceding optical path extension component of any optical path extension component, is incident on any optical path extension component, and then sequentially passes through the third and fourth polarization beam splitting elements in any optical path extension component before being incident on the second polarization state conversion and reflection component, and is output after passing through the fourth polarization beam splitting element in any optical path extension component.

[0077] In this embodiment of the invention, the interferometer mirror group has good longitudinal (i.e., the straight line direction in which the first polarization beam splitter 1 and the second polarization beam splitter 2 are located) scalability. By configuring multiple optical path extension components, the optical path of the first optical signal can be further extended, thereby increasing the optical subdivision number of the interferometer mirror group by a factor of two and further improving the resolution of the interferometer mirror group. By making reasonable use of the optical path extension components, space is saved while improving the resolution, thus improving the utilization rate of the interferometer mirror group.

[0078] Based on the above embodiments, the interferometer mirror group provided in this embodiment of the invention has an extended reflective element that is a corner cube prism.

[0079] Specifically, such as Figure 3 As shown in the embodiment of the present invention, the extended reflective elements 7 used in the interferometer mirror group are all corner pyramid prisms, which can achieve good retroreflection performance.

[0080] Based on the above embodiments, in the interferometer mirror assembly provided in this embodiment of the invention, the first polarization beam splitter 1, the second polarization beam splitter 2, the first polarization state conversion reflection component 3, the second polarization state conversion reflection component 4, and the target polarization state conversion component 5 are attached in the optical path transmission direction.

[0081] by Figure 2 For example, the right side of the first polarization beam splitter 1 is attached to the left side of the first polarization state conversion element 31, and the right side of the first polarization state conversion element 31 is attached to the left side of the first reflective element 32. The left side of the first polarization beam splitter 1 is attached to the right side of the second polarization beam splitter 2, the left side of the second polarization beam splitter 2 is attached to the right side of the second polarization state conversion element 41, and the left side of the second polarization state conversion element 41 is attached to the right side of the second reflective element 42. Here, the left side of the first reflective element 32 is the reflecting surface, and the right side of the second reflective element 42 is the reflecting surface.

[0082] The upper surface of the target polarization state conversion element 5 is attached to the lower surfaces of the first polarization beam splitter 1 and the second polarization beam splitter 2, respectively.

[0083] by Figure 3 For example, the right side of the first polarization beam splitter 1 is attached to the left side of the first polarization state conversion element 31, and the right side of the first polarization state conversion element 31 is attached to the left side of the first reflection element 32. The left side of the first polarization beam splitter 1 is attached to the right side of the second polarization beam splitter 2, the left side of the second polarization beam splitter 2 is attached to the right side of the third polarization beam splitter 8, the left side of the third polarization beam splitter 8 is attached to the right side of the fourth polarization beam splitter 9, the right side of the fourth polarization beam splitter 9 is attached to the right side of the second polarization state conversion element 41, and the left side of the second polarization state conversion element 41 and the right side of the second reflection element 42 are attached to each other.

[0084] In this embodiment of the invention, by attaching the components together, the structure of the interferometer assembly can be made more compact, which facilitates the miniaturization and integration design of the interferometer mirror group.

[0085] Based on the above embodiments, the target reflective element is a diffraction grating;

[0086] The incident angle of the first signal light on the diffraction grating is the Littoral angle.

[0087] Specifically, the target reflective element 6 can be a diffraction grating, which can be configured with parameters such as duty cycle and grating period according to actual conditions.

[0088] Since the target reflecting element 6 is a diffraction grating, the interferometer mirror group becomes a grating interferometer mirror group, realizing the function of a grating interferometer. Furthermore, since the incident angle of the first signal light on the diffraction grating is the Littoral angle, the first signal light diffracts on the target reflecting element 6, and the outgoing direction of the diffracted light is opposite to the incident direction of the first signal light. In this case, the target reflecting element 6 functions as a reflector. This facilitates improving the energy utilization rate of the first signal light through the structural design of the diffraction grating, and also enables simultaneous measurement of the displacement of the diffraction grating in both the X and Z directions. Here, the X direction is the vector direction of the diffraction grating, and the Z direction is the direction perpendicular to the plane of the diffraction grating.

[0089] It is understandable that the incident angle of the first signal light on the diffraction grating is the Littorau angle, which means that regardless of whether the first signal light is a p-light or an s-light, as long as it is incident on the diffraction grating, it will be incident at the Littorau angle.

[0090] When there is an angular error in the diffraction grating, the measured optical signal and the reference optical signal can always interfere in parallel without the generation of interference fringes. Compared with the traditional grating interferometer, the grating interferometer has a larger tolerance for angular deflection.

[0091] Based on the above embodiments, in the interferometer lens group provided in the embodiments of the present invention, the first signal light and the second signal light are orthogonally linearly polarized light signals with the same frequency, or orthogonally linearly polarized light signals with different frequencies.

[0092] Specifically, if the first signal light and the second signal light are orthogonally linearly polarized light signals with the same frequency, it means that they have the same frequency and orthogonal polarization states. In this case, the interferometer mirror group is a zero-difference interferometer mirror group, realizing the function of a zero-difference interferometer. Furthermore, this zero-difference interferometer has a large optical subdivision number and a high resolution.

[0093] like Figure 4 As shown, with Figure 2 The only difference is that, Figure 2The first and second signal lights are orthogonally polarized light signals of different frequencies, which are respectively incident on the first polarization beam splitter 1. Figure 4 The first and second signal lights are orthogonally linearly polarized light signals with the same frequency, incident on the first polarization beam splitter 1. The first polarization beam splitter 1 separates the first and second signal lights, allowing the first signal light to be transmitted and the second signal light to be reflected. Therefore, it can be concluded that... Figure 4 The solid line before the beam splitting surface of the first polarization beam splitting element 1 represents a single orthogonally linearly polarized light signal with the same frequency. The solid arrow after the beam splitting surface represents the transmission path and direction of the first signal light, and the dashed arrow represents the transmission path and direction of the second signal light.

[0094] also, Figure 4 The output optical path of the second polarization beam splitter 2 also includes a third polarization state conversion element 10, so that the output corresponding to the first signal light and the output corresponding to the second signal light can interfere to generate an interference signal. After passing through the third polarization state conversion element 10, the signal enters a four-channel or three-channel phase detection module to determine the phase information of the interference signal, and then determine the displacement information of the target reflective element.

[0095] Based on the above embodiments, the interferometer mirror assembly provided in the embodiments of the present invention further includes a fifth polarization beam splitter;

[0096] The first signal light obtained after the first beam passes through the fifth polarization beam splitter is incident on the first polarization beam splitter.

[0097] The second signal light obtained after the second beam passes through the fifth polarization beam splitter is incident on the first polarization beam splitter.

[0098] Both the first beam and the second beam are generated based on a laser light source.

[0099] Specifically, both the first beam and the second beam can be generated by a laser source, and the fifth polarization beam splitter can be a polarization beam splitter prism.

[0100] The first beam and the second beam can be incident perpendicularly from two mutually perpendicular surfaces of the fifth polarization beam splitter. Both beams can produce a first signal light and a second signal light after passing through the fifth polarization beam splitter. Here, only the first signal light obtained after the first beam passes through the fifth polarization beam splitter can be used and incident on the first polarization beam splitter. Similarly, only the second signal light obtained after the second beam passes through the fifth polarization beam splitter can be used and incident on the first polarization beam splitter.

[0101] In this embodiment of the invention, a fifth polarization beam splitter is introduced, which ensures that the first signal light and the second signal light are incident at the same position of the first polarization beam splitter.

[0102] like Figure 5 As shown, based on the above embodiments, this embodiment of the invention provides a displacement measurement system, including: a laser source 11, a processing component 12, a target reflective element 6, and an interferometer mirror group 13 provided in the above embodiments;

[0103] The laser source 11 is used to generate a first beam and a second beam, and inputs the first beam and the second beam into the interferometer mirror group 13;

[0104] The processing component 12 is used to receive the output signal of the interferometer mirror group 13 and determine the displacement information of the target reflective element based on the output signal.

[0105] Specifically, the laser source 11 can be a laser, used to emit a first beam and a second beam. The first beam and the second beam can both be mixed linearly polarized light, and their frequencies can be the same or different. They can be one beam or two beams, and no specific limitation is made here. Figure 5 In the image, the target reflective element 6 is a diffraction grating.

[0106] By incident the first beam and the second beam onto the interferometer mirror group 13, the fifth polarization beam splitter in the interferometer mirror group 13 receives and generates the first signal light and the second signal light. The first signal light and the second signal light are incident onto the first polarization beam splitter and transmitted within the interferometer mirror group 13, an interference signal of the measurement light signal and the reference light signal can be obtained, that is, the output signal of the interferometer mirror group 13. The interference signal is received by the processing component 12 to determine the displacement information of the target reflecting element.

[0107] Here, the processing component 12 may include a phase detector, a displacement calculation module, etc. The phase detector may be a four-channel or a three-channel device.

[0108] The displacement measurement system provided in this embodiment of the invention can achieve higher resolution and higher measurement accuracy due to the presence of the interferometer mirror group.

[0109] Based on the above embodiments, the displacement measurement system provided in this embodiment of the invention includes a first interferometer mirror group and a second interferometer mirror group.

[0110] The first signal light and the second signal light obtained after the first beam passes through the fifth polarization beam splitter are respectively incident on the first interferometer mirror group and the second interferometer mirror group;

[0111] The first signal light and the second signal light obtained after the second beam passes through the fifth polarization beam splitter are respectively incident on the second interferometer mirror group and the first interferometer mirror group.

[0112] Specifically, such as Figure 6 As shown, the displacement measurement system may include two interferometer mirror groups, namely the first interferometer mirror group 131 and the second interferometer mirror group 132. The first interferometer mirror group 131 and the second interferometer mirror group 132 are distributed in an axisymmetric manner. In this case, the first interferometer mirror group 131 and the second interferometer mirror group 132 can share the fifth polarization beam splitter 14, and the first signal light and the second signal light generated by the first beam and the second beam respectively after passing through the fifth polarization beam splitter 14 will both be utilized.

[0113] Taking a diffraction grating as an example, the first beam and the second beam are incident perpendicularly on two mutually perpendicular surfaces of the fifth polarization beam splitter 14. The first beam is transmitted through the fifth polarization beam splitter 14 to obtain p-beams and reflected to obtain s-beams. The second beam is transmitted through the fifth polarization beam splitter 14 to obtain p-beams and reflected to obtain s-beams. The p-beam obtained from the first beam through the fifth polarization beam splitter 14 serves as a first signal beam, and the s-beam obtained from the second beam through the fifth polarization beam splitter 14 serves as a second signal beam; both enter the first interferometer mirror group 131.

[0114] The first signal light is incident on the target reflective element 6 multiple times through the first interferometer mirror group 131 and reflected back into the first interferometer mirror group 131, and then output as a measurement light signal. The second signal light is output as a reference light signal after passing through the first interferometer mirror group 131.

[0115] The s-light obtained by the first beam through the fifth polarization beam splitter 14 serves as another second signal light, and the p-light obtained by the second beam through the fifth polarization beam splitter 14 serves as another first signal light. Both of them enter the second interferometer mirror group 132.

[0116] Furthermore, the first signal light is incident on the target reflective element 6 multiple times through the second interferometer mirror group 132 and reflected into the second interferometer mirror group 132, where it is output as another measurement light signal. The second signal light is output as another reference light signal after passing through the second interferometer mirror group 132.

[0117] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0118] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An interferometer mirror assembly, characterized in that, include: The system comprises a first polarization beam splitter, a second polarization beam splitter, a first polarization state conversion and reflection assembly, a second polarization state conversion and reflection assembly, and a target polarization state conversion element; wherein... The first signal light passes sequentially through the first polarization beam splitter and the target polarization state conversion element before being incident on the target reflection element. It then passes through the target reflection element and the target polarization state conversion element before being incident on the first polarization beam splitter. Finally, it passes sequentially through the first polarization beam splitter, the second polarization beam splitter, the target polarization state conversion element, the target reflection element, the target polarization state conversion element, and the second polarization beam splitter before being output. The second signal light is output after passing through the first polarization beam splitter, the first polarization state conversion and reflection component, the first polarization beam splitter, the second polarization beam splitter, the second polarization state conversion and reflection component, and the second polarization beam splitter in sequence; The first signal light and the second signal light are linearly polarized lights with orthogonal polarization states, and they have the same incident point on the first polarization beam splitter. It also includes: an optical path extension component, which comprises an extended reflection element, a third polarization beam splitter element, and a fourth polarization beam splitter element; The first signal light, after being output from the second polarization beam splitter, is incident on the extended reflector to obtain the first reflected light. The first reflected light is then incident on the target reflector after passing through the third polarization beam splitter and the target polarization state conversion element in sequence. After being reflected by the target reflector, it is then output after passing through the target polarization state conversion element, the third polarization beam splitter, the fourth polarization beam splitter, the target polarization state conversion element, the target reflector, the target polarization state conversion element, and the fourth polarization beam splitter in sequence. The second signal light is output after passing through the first polarization beam splitter, the first polarization state conversion and reflection component, the first polarization beam splitter, the second polarization beam splitter, the third polarization beam splitter, the fourth polarization beam splitter, the second polarization state conversion and reflection component, and the fourth polarization beam splitter in sequence.

2. The interferometer mirror assembly according to claim 1, characterized in that, The optical path extension component includes multiple components; For any optical path extension component other than the first optical path extension component, the first signal light, after passing through the beam output from the preceding optical path extension component, is incident on the optical path extension component, and sequentially passes through the extended reflection element, the third polarization beam splitter, and the target polarization state conversion element in the optical path extension component before being incident on the target reflection element. After being reflected by the target reflection element, it sequentially passes through the target polarization state conversion element, the third polarization beam splitter, the fourth polarization beam splitter, the target polarization state conversion element, the target reflection element, the target polarization state conversion element, and the fourth polarization beam splitter before being output. The second signal light, after passing through the beam output from the previous optical path extension component, is incident on any of the optical path extension components, and then, after passing through the third and fourth polarization beam splitters in the optical path extension components, is incident on the second polarization state conversion reflection component, and is output after passing through the fourth polarization beam splitter in the optical path extension component.

3. The interferometer mirror assembly according to claim 1, characterized in that, The extended reflective element is a cornerstone prism.

4. The interferometer mirror assembly according to claim 1, characterized in that, The first polarization beam splitter, the second polarization beam splitter, the first polarization state conversion and reflection component, the second polarization state conversion and reflection component, and the target polarization state conversion component are attached to each other in the optical path transmission direction.

5. The interferometer mirror assembly according to claim 1, characterized in that, Both the first polarization state conversion reflection component and the second polarization state conversion reflection component include a polarization state conversion element and a reflection element, and the polarization state conversion element is located in front of the reflection element.

6. The interferometer mirror assembly according to claim 1, characterized in that, The target reflective element is a diffraction grating; The incident angle of the first signal light on the diffraction grating is the Littoral angle.

7. The interferometer mirror assembly according to claim 1, characterized in that, The first signal light and the second signal light are orthogonally linearly polarized light signals with the same frequency, or orthogonally linearly polarized light signals with different frequencies.

8. The interferometer mirror assembly according to any one of claims 1-7, characterized in that, It also includes a fifth polarization beam splitter; The first signal light obtained after the first beam passes through the fifth polarization beam splitter is incident on the first polarization beam splitter. The second signal light obtained after the second beam passes through the fifth polarization beam splitter is incident on the first polarization beam splitter. Both the first beam and the second beam are generated based on a laser light source.

9. A displacement measurement system, comprising a laser source, a processing component, a target reflective element, and an interferometer mirror assembly as described in claim 8; The laser source is used to generate the first beam and the second beam, and inputs the first beam and the second beam into the interferometer mirror group; The processing component is used to receive the output signal of the interferometer mirror group and determine the displacement information of the target reflective element based on the output signal.

10. The displacement measurement system according to claim 9, characterized in that, The interferometer mirror group includes a first interferometer mirror group and a second interferometer mirror group; The first signal light obtained after the first beam passes through the fifth polarization beam splitter is incident on the first interferometer mirror group, and the second signal light obtained is incident on the second interferometer mirror group; The first signal light obtained after the second beam passes through the fifth polarization beam splitter is incident on the second interferometer mirror group, and the second signal light obtained is incident on the first interferometer mirror group.

Images