Quantum weak measurement technology-based flat glass refractive index gradient measuring device

Abstract

The application discloses a kind of flat glass refractive index gradient measuring device based on quantum weak measurement technology, including front selection polaroid, first polarization beam splitter, second polarization beam splitter, material to be measured, third polarization beam splitter, fourth polarization beam splitter, half-wave plate, 1 / 4 wave plate, rear selection state polaroid and photoelectric detector.The flat glass refractive index gradient measurement based on quantum weak measurement technology of the application realizes new high sensitivity, high precision measurement in ability;In the measurement structure, shear interference in two orthogonal directions is realized simultaneously, and self-reference interference can be realized, and the refractive index gradient measurement without reference that traditional interference measurement technology cannot be realized can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of refractive index measurement and quantum weak measurement, and particularly relates to a flat glass refractive index gradient measuring device based on quantum weak measurement technology. BACKGROUND

[0002] The refractive index of optical glass material directly affects the transmitted wave front. Under the condition of high precision requirement, the change of the wave front will cause imaging blur, quality deterioration, large light focusing focal point, reduced precision of the light wave front, and thus the overall quality is also reduced. Therefore, in the aspect of improving the performance of the optical system, it is indispensable to use the refractive index data of the glass material with lower error. Therefore, higher detection means needs to be used. According to the measurement result, the error introduction can be reduced by using the targeted solution, so as to continuously improve the processing quality.

[0003] The main methods of traditional glass material refractive index measurement are interference measurement, triangulation, point diffraction interference measurement and wave front sensing measurement. The detection precision of the wave front measurement method is limited by the micro-lens array manufacturing, the number of sub-apertures is limited, the number of sampling points is relatively small, and the spatial resolution is not high. There is a sampling error, and the reconstructed wave front phase can only reflect the general distribution, and cannot accurately reflect the details. The interference measurement method has obtained rich research results, and a part of it has developed into a stable commercial product, and its principle uses a reference mirror to generate a reference wave front as a measurement benchmark for interference measurement. The triangulation method is limited by the existing optical processing and assembly process, and it is difficult to further improve the materials and equipment. Therefore, it is temporarily impossible to continue to improve the measurement precision on the basis of the existing technology.

[0004] Quantum weak measurement technology was first proposed by Aharonov, Albert and L.Vaidman (AAV) in 1998 when analyzing quantum spin problems. It is a measurement method for determining the statistical properties of a quantum system through pre-and-post-selection measurement, which can suppress technical noise and thus amplify the measured signal, improve the sensitivity and stability of the system. In the theoretical system of quantum weak measurement, the coupling strength between the system itself and the measuring instrument is very weak, but under the condition that the pre-and-post-selection states are close to orthogonal, the weak value corresponding to the weak coupling can far exceed the maximum eigenvalue of the observable, and the weak value itself can be constructed in the form of a complex number. This phenomenon of significantly amplifying the observable of the system is called weak value amplification effect, which has very important practical value in the field of precision measurement SUMMARY

[0005] The purpose of the present application is to provide a flat glass refractive index gradient measuring device based on quantum weak measurement technology.

[0006] The technical scheme for achieving the object of the present application is as follows: a flat glass refractive index gradient measuring device based on quantum weak measurement technology, comprising a front selection polarizer, a first polarization beam splitter, a second polarization beam splitter, a material to be measured, a third polarization beam splitter, a fourth polarization beam splitter, a fifth polarization beam splitter, a half-wave plate, a 1 / 4 wave plate, a rear selection state polarizer and a photoelectric detector; wherein:

[0007] The incident light passes through the front selection polarizer to form front selection polarized light, and the front selection polarized light is incident on the first polarization beam splitter to obtain horizontal polarized light and vertical polarized light; the horizontal polarized light passes through the second polarization beam splitter to form a pair of parallel light with the horizontal direction and the polarization directions of the parallel light being perpendicular to each other; the vertical polarized light passes through the third polarization beam splitter to form a pair of parallel light with the vertical direction and the polarization directions of the parallel light being perpendicular to each other; the two pairs of generated parallel light are incident on the material to be measured, respectively pass through the fourth polarization beam splitter and the fifth polarization beam splitter, are combined and interfered to form two beams of rear light, and then pass through the half-wave plate, the 1 / 4 wave plate and the rear selection state polarizer in sequence and are then incident on the photoelectric detector.

[0008] Further, the front selection polarizer has a 45° angle between the polarization direction and the horizontal direction to obtain linearly polarized light, and the rear selection state polarizer has a -45° angle between the polarization direction and the horizontal direction, and the polarization direction of the rear selection state polarizer is perpendicular to the polarization direction of the front selection state.

[0009] Further, the first polarization beam splitter has an optical axis along the horizontal direction, and the horizontal polarized light obtained after polarization splitting is denoted as |H>, and the vertical polarized light is denoted as |V>. The two beams of polarized light with perpendicular polarization directions are respectively incident on the second polarization beam splitter and the third polarization beam splitter.

[0010] Further, the second polarization beam splitter has an optical axis with a 45° angle with the horizontal direction, and two beams of light parallel to each other are generated in the horizontal direction after passing through the second polarization beam splitter, and the polarization directions of the two beams of light are perpendicular to each other. The third polarization beam splitter has an optical axis with a 45° angle with the surface inward, and two beams of light parallel to each other are generated inwardly perpendicular to the surface after passing through the third polarization beam splitter, and the polarization directions of the two beams of light are perpendicular to each other.

[0011] Further, the fourth polarization beam splitter has an optical axis with a -45° angle with the horizontal direction, and the two beams of light parallel to each other in the horizontal direction are combined into one beam after passing through the fourth polarization beam splitter. The fifth polarization beam splitter has an optical axis with a -45° angle with the surface inward, and the two beams of light parallel to each other inwardly perpendicular to the surface are combined into one beam after passing through the fifth polarization beam splitter.

[0012] Further, the photoelectric detector is a CCD camera, a CMOS camera or an ICCD camera.

[0013] Further, the light spot brightness data of the image collected by the photoelectric detector is changed in gray value, and then the centroid position of the image is calculated; the centroid position of the image is the centroid position of the light beam at the moment.

[0014] Further, the expression of the pre-selected polarization state is |ψ i >=cosα|H>+sinα|V>,herein α is the angle between the pre-selected polarizer and the horizontal direction, |H> and |V> represent the eigenstates of the horizontal polarized light and the vertical polarized light respectively. The expression of the post-selected polarization state is Wherein β is the angle between the post-selected polarizer and the orthogonal direction of the pre-selected polarization state, is the phase difference between the two polarization components; combined with the definition of the weak value, the expression of the weak value is Wherein A w is the amplification factor of the measured refractive index, is the observable operator used in the present example. In the present system, the expression of the centroid movement amount of the outgoing light spot can be calculated as: <x>= 4ka 2 / Δnd; in which, <x>The displacement of the light spot center of the measuring beam obtained by reasoning the measuring principle of the plate glass refractive index gradient based on the quantum weak measurement technology is represented by Δx, Δn represents the fluctuation of the refractive index gradient of the material to be measured in a certain direction, a is the initial size of the light beam, k is the wave number of the light, and d is the thickness of the material to be measured.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] (1) The plate glass refractive index gradient measuring method based on the quantum weak measurement technology realizes new high-sensitivity and high-precision detection.

[0017] (2) The absolute measurement without a reference surface can be realized by differential measurement, and two measurements are not required for each measured device, thereby reducing the system error and eliminating the problem that the manufacturing precision of the reference surface itself limits the measurable precision.

[0018] (3) The refractive index distribution in the orthogonal directions can be simultaneously measured by arranging two polarization beam splitters with the shearing directions perpendicular to each other, and the gradient measurement is realized.

[0019] The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The present application provides a plate glass refractive index gradient measuring device based on the quantum weak measurement technology.

[0021] Figure 2 The present application provides a light intensity detected by a photodetector when there is no measured member.

[0022] Figure 3 The present application provides a light intensity detected by a photodetector when there is a measured member.

[0023] Figure 4 The present application provides a plate glass refractive index gradient measuring method based on the quantum weak measurement technology.

[0024] In the figure: 1 - front selection polarizer, 2 - first polarization beam splitter, 3 - second polarization beam splitter, 4 - third polarization beam splitter, 5 - material to be measured, 6 - fourth polarization beam splitter, 7 - fifth polarization beam splitter, 8 - half-wave plate, 9 - quarter-wave plate, 10 - rear selection state polarizer, 11 - photodetector. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] like Figure 1 As shown, a method for measuring the refractive index gradient of a flat glass based on quantum weak measurement includes a pre-selection detection module comprising a pre-selection polarizer 1, a first polarization beam splitter 2, a second polarization beam splitter 3, a third polarization beam splitter 4, a test material 5, a fourth polarization beam splitter 6, a fifth polarization beam splitter 7, a half-wave plate 8, a quarter-wave plate 9, a post-selection polarizer 10, and a photodetector 11. The optical path structure can be described as follows: the incident light is prepared into the initial state of the system by the pre-selection polarizer 1, and after being split by the first polarization beam splitter 2, horizontally polarized light and vertically polarized light are obtained; the horizontally polarized light, after passing through the second polarization beam splitter 3, generates two beams of light with orthogonal polarization directions and parallel to each other in the horizontal direction. The vertically polarized light, after passing through the third polarization beam splitter 4, generates two beams of light with orthogonal polarization directions and parallel to each other in the vertical direction. Two pairs of parallel beams are incident on the device under test, and then on the fourth polarizing beam splitter 6 and the fifth polarizing beam splitter 7, respectively. The two orthogonally split pairs of parallel beams are combined into two beams, which are then sequentially incident on the half-wave plate 8, the quarter-wave plate 9, and the post-selective polarizer 10, and finally on the photodetector 11. Figure 4 As shown.

[0027] The present invention directly obtains the centroid displacement of the measurement beam based on the modulated beam and the measurement beam, and combines the refractive index gradient measurement method of flat glass based on quantum weak measurement to obtain the characterization relationship between the centroid displacement of the beam and the refractive index uniformity, and calculates the refractive index gradient change.

[0028] In the above optical path structure, the first polarization beam splitter 2 is mainly responsible for splitting the probe light into two beams for detection in the horizontal and vertical directions respectively, thus generating a gradient measurement result in a single measurement. The second and fourth polarization beam splitters split and combine the horizontally polarized light beams, which then pass through the device under test for measurement in the first direction. The third and fifth polarization beam splitters split and combine the vertically polarized light beams, which then pass through the device under test for measurement in the second direction orthogonal to the first direction.

[0029] The polarization direction of the pre-selective polarizer is 45° with the horizontal direction, and the polarization direction of the post-selective polarizer is -45° with the horizontal direction. They are perpendicular to each other and satisfy the pre-selection and post-selection requirements of quantum weak measurement technology.

[0030] In this embodiment of the invention, after the first polarizing beam splitter splits the optical beam horizontally, the resulting horizontally polarized light is denoted as |H>, and the vertically polarized light is denoted as |V>. The second and third polarizing beam splitters split the incident light into two beams, with the split directions perpendicular to each other, thus satisfying the requirements for gradient measurement. The fourth and fifth polarizing beam splitters combine the split parallel light beams after passing through the device under test. Therefore, the optical axes of the fourth and fifth polarizing beam splitters, which perform the beam combining function, should be axially symmetrical with the optical axes of the second and third polarizing beam splitters.

[0031] Furthermore, the expression for the pre-selected polarization state is |ψ i >=cosα|H>+sinα|V>, where α is described as the angle between the pre-selected polarizer (2) and the horizontal direction, and |H> and |V> represent the eigenstates of horizontally polarized light and vertically polarized light, respectively. The post-selected polarization state is represented as Where β is the angle between the post-selected polarizer (10) and the orthogonal direction of the pre-selected polarization state. Let be the phase difference between the two polarization components; combining the definition of a weak value, the expression for the weak value is: Where A w To measure the magnification factor of the refractivity, This is the observable operator used in this example. The expression for the centroid shift of the emitted light spot can be derived in this system as follows: <x>= 4ka 2 / Δnd.

[0032] In the formula, <x>The displacement of the spot center of the measuring beam is obtained based on the inference of the measurement principle of the gradient of the refractive index of the flat glass based on the quantum weak measurement technology. Δn represents the fluctuation of the refractive index gradient of the material to be measured in a certain direction, a is the initial size of the light beam, k is the wave number of the light, and d is the thickness of the material to be measured.

[0033] Figure 2 The initial positions of the spots of the modulated light beam in the horizontal direction and the vertical direction when there is no measured object are shown. After the measured object is added, the intensity distribution of the spot is changed, and the spot center is moved, as shown in Figure 3 According to the processing method, the relationship between the displacement of the spot center of the light beam and the uniformity of the refractive index is obtained based on the modulated light beam and the measuring light beam, the displacement of the spot center of the measuring light beam is obtained, and the relationship between the displacement of the spot center of the light beam and the uniformity of the refractive index based on the quantum weak measurement is obtained. Therefore, the change of the refractive index gradient can be obtained.

[0034] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.< / x> < / x> < / x> < / x>

Claims

1. A device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology, characterized in that, It includes a pre-selective polarizer, a first polarizing beam splitter, a second polarizing beam splitter, the material under test, a third polarizing beam splitter, a fourth polarizing beam splitter, a fifth polarizing beam splitter, a half-wave plate, a quarter-wave plate, a post-selective polarizer, and a photodetector; wherein: The incident light passes through a pre-selective polarizer to form pre-selective polarized light, which is then incident on the first polarizing beam splitter to obtain horizontally polarized light and vertically polarized light. The horizontally polarized light passes through a second polarizing beam splitter to form a pair of parallel lights that are parallel to the horizontal direction and perpendicular to each other in polarization direction. The vertically polarized light passes through a third polarizing beam splitter to form a pair of parallel lights that are parallel to the vertical direction and perpendicular to each other in polarization direction. The two pairs of parallel lights are incident on the material under test, pass through the fourth polarizing beam splitter and the fifth polarizing beam splitter respectively, and after beam combining and interference, they form two beams that pass sequentially through the half-wave plate, the quarter-wave plate, and the post-selective polarizer before entering the photodetector.

2. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 1, characterized in that, The pre-selective polarizer has a polarization direction with a horizontal angle of 45° to obtain linearly polarized light; the post-selective polarizer has a polarization direction with a horizontal angle of -45°, which is perpendicular to the polarization direction of the pre-selective polarizer.

3. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 1, characterized in that, The first polarizing beam splitter has its optical axis in the horizontal direction. After polarization beam splitting, the resulting horizontally polarized light is denoted as... Vertically polarized light is denoted as The two beams with mutually perpendicular polarization directions are respectively injected into the second polarization beam splitter and the third polarization beam splitter.

4. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 1, characterized in that, The optical axis of the second polarizing beam splitter is at an angle of 45° to the horizontal direction. After passing through the second polarizing beam splitter, two beams of light are generated that are parallel to each other in the horizontal direction and their polarization directions are perpendicular to each other.

5. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 4, characterized in that, The optical axis of the third polarizing beam splitter is perpendicular to the surface and inward at an angle of 45°. After passing through the third polarizing beam splitter, two parallel beams of light are generated perpendicular to the surface and inward, with their polarization directions being perpendicular to each other.

6. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 1, characterized in that, The optical axis of the fourth polarizing beam splitter is at an angle of -45° to the horizontal direction. After passing through the fourth polarizing beam splitter, two beams of light that are parallel to each other in the horizontal direction are combined into one beam.

7. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 6, characterized in that, The optical axis of the fifth polarization beam splitter is perpendicular to the surface and has an inward angle of -45°. After passing through the fifth polarization beam splitter, two beams of light that are perpendicular to the surface and parallel to each other are combined into one beam.

8. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 1, characterized in that, The photodetector is a CCD camera, a CMOS camera, or an ICCD camera.

9. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 1, characterized in that, The grayscale value of the light spot brightness data in the image acquired by the photodetector is changed, and then the centroid position of the image is calculated; the centroid position of the image is the centroid position of the light beam at that moment.

10. The device for measuring the refractive index gradient of flat glass based on quantum weak measurement technology according to claim 1, characterized in that, The expression for the preselected polarization state is: , where is the angle between the preselected polarization state and the horizontal direction. and These represent the eigenstates of horizontally polarized light and vertically polarized light, respectively; the latter polarization state is then chosen as... Where φ is the angle between the orthogonal directions of the post-selected polarization state and the pre-selected polarization state, and φ is the phase difference between the two polarization components; combining the definition of a weak value, the expression for the weak value is: ,in The magnification factor for measuring refractive index, The operator is observable; the expression for the centroid shift of the emitted light spot is: In the formula, This indicates the displacement of the centroid of the measured beam spot. This represents the fluctuation of the refractive index gradient of the material under test in a certain direction, where a is the initial size of the beam, k is the wave number of the light, and d is the thickness of the material under test.

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