A polar azimuth absolute zero calibration standard, device and method of use

Abstract

The application provides a standard device for polar azimuth absolute zero position calibration, a device and a use method. The standard device comprises a standard prism and a polar grid plating layer. The polar grid plating layer is arranged on one surface of the standard prism. The polar grid plating layer comprises a polar grid and an alignment mark. The polar grid is arranged in a central region of the polar grid plating layer. The alignment mark is arranged on both sides of the polar grid. The standard device for polar azimuth absolute zero position calibration greatly simplifies the calibration process of the polar azimuth absolute zero position, reduces the equipment conditions of the calibration, and improves the repeated precision of the polar azimuth absolute zero position calibration.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement and metrology, and in particular relates to a standard, device and method for calibrating the absolute zero position of polarization azimuth angle. Background Technology

[0002] Polarization is one of the fundamental properties of light. The polarization characteristics of a light beam are typically expressed by its degree of polarization, polarization azimuth angle, and ellipticity angle. Among these, the polarization azimuth angle characterizes the orientation of two polarization eigenvalues ​​and is a key parameter describing the polarization state of the light beam.

[0003] Suppose that at any given moment, the projection of the electric field vector at any point in space along the propagation direction onto the xy plane is an ellipse, which is called elliptically polarized light (e.g., ...). Figure 1 (As shown).

[0004] Figure 1 In this equation, a and b represent the major and minor axes of the elliptically polarized light, respectively, and ψ represents the angle between the direction of the major axis of the elliptically polarized light and the x-reference direction, i.e., the azimuth angle (AOP). The relationship between the azimuth angle ψ and the amplitude and phase (E0x, E0y, φ) of the light wave is expressed as follows:

[0005]

[0006] The polarization state of a target is typically measured using an analyzer. An analyzer mainly consists of a polarizer and a polarizing prism. When elliptically polarized light emitted by the target passes through the analyzer, the incident light perpendicular to the analyzer's polarization direction is absorbed, while the parallel light is transmitted as linearly polarized light. By combining the results from three analyzers with different polarization directions, the target's polarization state (under the assumption of linear polarization) can be obtained.

[0007] However, the coordinates of the analyzer itself must coincide with the xy coordinates in the diagram above. If they do not coincide, the polarization azimuth angle of the target beam will inevitably have an offset angle. That is, it will introduce a deviation from the absolute zero position of the polarization azimuth angle. For the same target beam, only the angle of the analyzer is different, and the measured polarization azimuth angle results will be different. This poses a significant obstacle to the final application of the polarization azimuth angle data.

[0008] In practical applications, the reference coordinate system can be a geodetic coordinate system, obtained using equipment such as a level or theodolite. The horizontal plane is used as the y-axis, and the intersection of the horizontal plane and the incident wavefront is used as the x-axis. However, common coordinate system transfer methods, such as theodolite alignment, three-plane reference prisms, and autocollimation, cannot link the coordinate system to the polarization axis of the analyzer. Transferring the coordinate system from the geometric dimension to the polarization dimension requires using the analyzer's own grating to characterize the direction and using alignment marks for transfer. This process is relatively complex, requiring a high-precision, high-magnification scanning microscope, high-precision guide rails, and multiple steps such as characterization and alignment. This results in high laboratory requirements, long processing time, and a high risk of error for polarization absolute zero azimuth calibration, hindering its widespread application. Summary of the Invention

[0009] The purpose of this invention is to provide a standard, device, and method for calibrating the absolute zero position of polarization azimuth angle. By adding a polarization grating coating to one surface of the standard prism, the technical problems of the existing calibration process for the absolute zero position of polarization azimuth angle being relatively complex, time-consuming, and prone to errors are solved.

[0010] To solve the above-mentioned technical problems, the present invention is implemented through the following technical solution:

[0011] This invention provides a standard for calibrating the absolute zero position of polarization azimuth angle, comprising: a standard prism and a polarization grid coating;

[0012] The polarization grid coating is disposed on one of the surfaces of the standard prism;

[0013] The polarization grating coating includes a polarization grating and alignment marks. The polarization grating is disposed in the central region of the polarization grating coating, and the alignment marks are disposed on both sides of the polarization grating.

[0014] In one embodiment of the present invention, the standard prism includes a standard cubic prism or a standard triangular prism.

[0015] In one embodiment of the present invention, the polarization grid coating further includes a substrate, and the polarization grid and the alignment mark are deposited on the substrate by photolithography or scribing techniques.

[0016] In one embodiment of the invention, the substrate is bonded to one of the surfaces of the standard prism by optical bonding.

[0017] In one embodiment of the present invention, the angle between the polarization grating marking direction and the bottom surface of the standard prism is used as one of the parameters in the calibration process of the standard.

[0018] In one embodiment of the invention, the polarization grid and the alignment mark are directly plated onto one of the surfaces of the standard prism.

[0019] In one embodiment of the present invention, a protective layer is formed on the surface of the polarization grid.

[0020] In one embodiment of the invention, the alignment marks include at least two and are symmetrically distributed on both sides of the polarization grid.

[0021] Based on the same inventive concept, another embodiment of the present invention provides a device for calibrating the absolute zero position of polarization azimuth angle, comprising:

[0022] Standard platform;

[0023] A parallel light source is placed on the standard platform;

[0024] The standard for calibrating the absolute zero polarization azimuth angle as described above is placed on the standard platform and located on one side of the parallel light source, with the polarization grating coating of the standard perpendicular to the optical path of the parallel light source.

[0025] Based on the same inventive concept, another embodiment of the present invention provides a method for using a standard for calibrating the absolute zero position of polarization azimuth angle, comprising:

[0026] The parallel light source, standard, and polarization measuring instrument to be calibrated are placed sequentially on the standard platform and the level is determined by a level.

[0027] The polarization grating coating of the standard is made perpendicular to the optical path of the parallel light source by means of a self-collimation method.

[0028] The position of the polarization measuring instrument to be calibrated is adjusted so that the optical axis of the polarization measuring instrument to be calibrated is consistent with the coordinate system formed by the standard.

[0029] The angle between the polarized light emitted from the standard instrument and the horizontal plane is obtained based on the orientation of the polarized light emitted from the standard instrument and the angle between the polarization grating and the bottom surface of the standard prism, thereby determining the absolute polarization zero point of the polarized light emitted from the standard instrument.

[0030] The polarization measuring instrument to be calibrated is calibrated using the polarized light emitted from the ray, and the absolute value of the azimuth angle in the polarization measurement result of the polarization measuring instrument to be calibrated is obtained.

[0031] This invention provides a standard for calibrating the absolute zero position of polarization azimuth angle, comprising a standard prism and a polarization grating coating. The polarization grating coating is disposed on one surface of the standard prism. The polarization grating coating includes a polarization grating and alignment marks. The polarization grating is disposed in the central region of the polarization grating coating, and the alignment marks are disposed on both sides of the polarization grating. The standard for calibrating the absolute zero position of polarization azimuth angle provided by this invention can easily transfer coordinates from the geometric dimension to the polarization dimension, realizing the transfer of the zero position of the analyzer's polarization axis to the geodetic coordinate system, thereby obtaining the absolute zero position of the target light's polarization azimuth angle. The standard for calibrating the absolute zero position of polarization azimuth angle provided by this invention greatly simplifies the calibration process, reduces the equipment requirements for calibration, and improves the repeatability accuracy of the polarization azimuth angle calibration.

[0032] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a projection of elliptically polarized light onto the xy plane.

[0035] Figure 2 This is a schematic diagram of the system composition of a standard for calibrating the absolute zero position of polarization azimuth angle, provided as an exemplary embodiment of this application.

[0036] Figure 3 Three views of a standard for calibrating the absolute zero position of polarization azimuth angle provided for an exemplary embodiment of this application.

[0037] Figure 4 This is a schematic diagram of a polarization azimuth absolute zero calibration device provided as an exemplary embodiment of this application.

[0038] Figure 5 This is a flowchart illustrating a method for using a standard for calibrating the absolute zero position of polarization azimuth angle, provided as an exemplary embodiment of this application.

[0039] 1 parallel light source

[0040] 2. Standard

[0041] 3. Polarization measuring instrument to be calibrated

[0042] 4 Standard Platform

[0043] 20 Polarizing grid coating

[0044] 21 Standard Prism

[0045] 201 Polarization Grid

[0046] 202 Alignment Marks

[0047] 203 substrate Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] To address the problems of complex, time-consuming, and error-prone calibration processes for absolute zero polarization azimuth angle, this invention provides a standard for calibrating absolute zero polarization azimuth angle. The standard includes a standard prism and a polarization grating coating. The polarization grating coating is disposed on one surface of the standard prism. The polarization grating coating includes a polarization grating and alignment marks. The polarization grating is located in the central region of the polarization grating coating, and the alignment marks are located on both sides of the polarization grating. These embodiments will be discussed in detail below.

[0050] In an exemplary embodiment of this application, the standard for calibrating the absolute zero position of the polarization azimuth angle includes a standard prism and a polarization grating coating, wherein the polarization grating coating includes a polarization grating and alignment marks. Specifically, please refer to... Figure 2 As shown, Figure 2This is a system composition diagram of the standard used for absolute zero-position calibration of polarization azimuth angle. The polarization grating coating 20 is disposed on one surface of the standard prism 21. The polarization grating coating 20 is a thin layer of metal with a thickness ranging from tens of nanometers to tens of micrometers. The polarization grating 201 is disposed in the central region of the polarization grating coating 20, and the alignment marks 202 are disposed on both sides of the polarization grating 201. In this embodiment, the standard prism 21 is used for geometric coordinate standard, typically a standard cubic prism or a standard triangular prism. Of course, in other embodiments, the standard prism 21 can also adopt other styles of standard prism 21. In addition, the standard prism 21 is made of optical glass, and the included angle between adjacent working surfaces of the standard prism 21 is determined and has high precision. In this embodiment, the standard prism 21 is a standard cubic prism, and each of its faces is a working surface; in other words, all faces of the standard cubic prism are optical surfaces. Furthermore, the included angle between any three working surfaces adjacent to any corner of the standard cubic prism is 90°±15". It should be noted that different standard cubic prisms have different accuracies, and can be flexibly selected according to the actual application requirements.

[0051] In an exemplary embodiment of this application, the polarization grating coating further includes a substrate, and the polarization grating and the alignment mark are deposited on the substrate using photolithography or scribing techniques. Specifically, please refer to... Figure 3 As shown, Figure 3The three-view diagram shows the standard used for absolute zero-position calibration of polarization azimuth angle. The substrate 203 is a square thin sheet with a side length consistent with the side length of the standard cubic prism 21 and a negative tolerance. The side length d of the standard cubic prism 21 is typically between 15mm and 50mm. In this embodiment, the side length d of the standard cubic prism 21 is 30mm. The thickness of the substrate 203 is 4mm, and the material of the substrate 203 is fused silica. In this embodiment, a polarization grating 201 is deposited in the central region of one side surface of the substrate 203 using photolithography. Simultaneously, alignment marks 202 are deposited on both sides of the polarization grating 201. It should be noted that the alignment marks 202 are photolithographically formed simultaneously with the polarization grating 201, and the alignment marks 202 are wider than the grating spacing of the polarization grating 201. The alignment marks 202 should be present on both sides of the polarization grating region. It should be noted that the alignment mark 202 typically has a width between 3 μm and 10 μm and a length between 20 μm and 1000 μm. The alignment mark 202 comprises at least two and is symmetrically distributed on both sides of the polarization grid 201. Notably, the alignment mark 202 comprises at least one pair; that is, the alignment mark 202 can be one pair or several pairs. Furthermore, the alignment mark 202 includes different shapes. In this embodiment, the alignment mark 202 is a rectangular groove with a certain length and width.

[0052] In one exemplary embodiment of this application, the substrate 203 is bonded to one surface of the standard prism 21 by optical bonding. For details, please refer to... Figure 3 As shown, the bottom surface of the substrate 203 is tightly bonded to one surface of the standard cubic prism using optical bonding. It should be noted that by using optical bonding, the angle between the marking direction of the polarization grating 201 and the coordinate system defined by the standard cubic prism can be accurately measured and used as one of the parameters in the calibration process of the standard instrument, which is then subtracted in subsequent calibration operations. Furthermore, the combination of the polarization grating coating 20 and the standard prism 21 can also directly use one surface of the standard prism 21 as the base surface for coating. In practical applications, the angular difference between the bottom surface of the standard prism 21 and the marking direction of the polarization grating can be obtained by measuring the alignment mark 202 using a reading microscope.

[0053] In an exemplary embodiment of this application, the marking direction of the polarization grating 201 is parallel to one of the axes of the coordinate system defined by the standard prism 21. The polarization grating 201 is formed on the substrate surface with periodic parallel lines similar to a grating using photolithography or scribing techniques.

[0054] In an exemplary embodiment of this application, a protective layer is further formed on the surface of the polarization grid 201. In this embodiment, please refer to... Figure 3 As shown, on one side surface of the substrate 203, an aluminum grid is deposited by photolithography, and three pairs of alignment marks 202 are added on both sides simultaneously. At the same time, a thin layer of silicon dioxide is deposited on the surface of the aluminum grid to prevent oxidation of the aluminum grid.

[0055] Based on the same inventive concept, this invention also provides a device for calibrating the absolute zero position of polarization azimuth angle. Please refer to [link to device]. Figure 4 As shown, Figure 4 This diagram illustrates the polarization azimuth standard positioning of the standard used for absolute zero-position calibration of polarization azimuth. The device includes a standard platform 4, a parallel light source 1, and a standard 2. The parallel light source 1 and the standard 2 are placed on the standard platform 4, with the standard 2 located to one side of the parallel light source 1, and the polarization grating coating 20 of the standard 2 perpendicular to the optical path of the parallel light source 1. The polarization measuring instrument 3 to be calibrated is located to one side of the direction of the emitted light from the standard 2. It should be noted that the standard 2 is the aforementioned standard used for absolute zero-position calibration of polarization azimuth. In this embodiment, the standard platform is a 00-level standard platform.

[0056] Based on the same inventive concept, please refer to Figure 5 As shown, the present invention also provides a method for using a standard for calibrating the absolute zero position of the polarization azimuth angle, comprising the following steps:

[0057] S100: Place the parallel light source, standard, and polarization measuring instrument to be calibrated on the standard platform in sequence and determine the level using a level.

[0058] S200: The polarization grating coating of the standard is made perpendicular to the optical path of the parallel light source by means of a self-collimation method;

[0059] S300: Adjust the position of the polarization measuring instrument to be calibrated so that the optical axis of the polarization measuring instrument to be calibrated is consistent with the coordinate system formed by the standard instrument;

[0060] S400: Based on the orientation of the polarized light emitted from the standard instrument and the angle between the polarization grating and the bottom surface of the standard prism, the angle between the polarized light emitted from the standard instrument and the horizontal plane is obtained, thereby determining the absolute polarization zero point of the polarized light emitted from the standard instrument.

[0061] S500: The polarization measuring instrument to be calibrated is calibrated using the polarized light emitted from the ray, and the absolute value of the azimuth angle in the polarization measurement result of the polarization measuring instrument to be calibrated is obtained.

[0062] In summary, this invention provides a standard for calibrating the absolute zero polarization azimuth angle, comprising a standard prism and a polarization grating coating. The polarization grating coating is disposed on one surface of the standard prism, and includes a polarization grating and alignment marks. The polarization grating is located in the central region of the polarization grating coating, and the alignment marks are located on both sides of the polarization grating. By firmly combining the polarization grating with the standard prism, the support for the polarization dimension coordinate system (i.e., the polarization grating) and the support for the geometric dimension coordinate system (i.e., the standard prism) are integrated. Furthermore, due to the excellent alignment capability of photolithography, by using a metal layer and photolithography, extremely high surface consistency between the polarization grating and the standard prism can be achieved. It should be noted that the above combination utilizes both transmission and reflection of the standard prism, rather than only utilizing reflected light as in ordinary standard prisms. The combined standard can be used to calibrate the polarization axis of an analyzer, thereby calibrating the absolute zero polarization angle of the target light. The standard for calibrating the absolute zero position of polarization azimuth provided by the present invention greatly simplifies the calibration process of the absolute zero position of polarization azimuth, reduces the equipment requirements for calibration, and improves the repeatability accuracy of the calibration of the absolute zero position of polarization azimuth.

[0063] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0064] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A standard for calibrating the absolute zero position of polarization azimuth angle, characterized in that, Includes standard prisms and polarizing grid coatings; The polarization grid coating is disposed on one of the surfaces of the standard prism; The polarization grid coating includes a polarization grid and alignment marks. The polarization grid is disposed in the central region of the polarization grid coating, and the alignment marks are disposed on both sides of the polarization grid. In use, the polarization grating coating of the standard is made perpendicular to the optical path of the parallel light source by means of self-collimation. The angle between the polarization of the emitted light and the horizontal plane is obtained according to the orientation of the polarization of the emitted light and the angle between the polarization grating and the bottom surface of the standard prism, thereby determining the absolute polarization zero position of the emitted light.

2. The standard for calibrating the absolute zero position of the polarization azimuth angle according to claim 1, characterized in that, The standard prism includes a standard cubic prism or a standard triangular prism.

3. The standard for calibrating the absolute zero position of the polarization azimuth angle according to claim 1, characterized in that, The polarization grid coating also includes a substrate, and the polarization grid and the alignment mark are deposited on the substrate by photolithography or scribing techniques.

4. The standard for calibrating the absolute zero position of the polarization azimuth angle according to claim 3, characterized in that, The substrate is bonded to one of the surfaces of the standard prism by optical bonding.

5. The standard for calibrating the absolute zero position of the polarization azimuth angle according to claim 4, characterized in that, The angle between the polarization grating marking direction and the bottom surface of the standard prism is used as one of the parameters in the calibration process of the standard.

6. The standard for calibrating the absolute zero position of the polarization azimuth angle according to claim 1, characterized in that, The polarization grating and the alignment mark are directly plated onto one of the surfaces of the standard prism.

7. The standard for calibrating the absolute zero position of the polarization azimuth angle according to claim 1, characterized in that, A protective layer is formed on the surface of the polarization grating.

8. The standard for calibrating the absolute zero position of polarization azimuth angle according to claim 1, characterized in that, The alignment marks include at least two and are symmetrically distributed on both sides of the polarization grid.

9. A device for calibrating the absolute zero position of polarization azimuth angle, characterized in that, include: Standard platform; A parallel light source is placed on the standard platform; The standard for calibrating the absolute zero position of the polarization azimuth angle as described in any one of claims 1-8 is placed on the standard platform and located on one side of the parallel light source, wherein the polarization grating coating of the standard is perpendicular to the optical path of the parallel light source.

10. A method of using the standard instrument according to claim 1, characterized in that, include: The parallel light source, standard, and polarization measuring instrument to be calibrated are placed sequentially on the standard platform and the level is determined by a level. The polarization grating coating of the standard is made perpendicular to the optical path of the parallel light source by means of a self-collimation method. The position of the polarization measuring instrument to be calibrated is adjusted so that the optical axis of the polarization measuring instrument to be calibrated is consistent with the coordinate system formed by the standard. The angle between the polarized light emitted from the standard instrument and the horizontal plane is obtained based on the orientation of the polarized light emitted from the standard instrument and the angle between the polarization grating and the bottom surface of the standard prism, thereby determining the absolute polarization zero point of the polarized light emitted from the standard instrument. The polarization measuring instrument to be calibrated is calibrated using the polarized light emitted from the ray, and the absolute value of the azimuth angle in the polarization measurement result of the polarization measuring instrument to be calibrated is obtained.

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