CN115451809A - Detection system and method based on vortex phase circular polarization vector superposition - Google Patents

Detection system and method based on vortex phase circular polarization vector superposition Download PDF

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CN115451809A
CN115451809A CN202211197385.6A CN202211197385A CN115451809A CN 115451809 A CN115451809 A CN 115451809A CN 202211197385 A CN202211197385 A CN 202211197385A CN 115451809 A CN115451809 A CN 115451809A
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phase
detected object
coordinate point
polarization
vortex
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付佳昆
代林茂
李晓春
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Changsha Lubang Photoelectric Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
    • G01B9/02011—Interferometers characterised by controlling or generating intrinsic radiation properties using temporal polarization variation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02015—Interferometers characterised by the beam path configuration
    • G01B9/02024—Measuring in transmission, i.e. light traverses the object
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The invention relates to the technical field of optical detection, and discloses a detection system and a detection method based on vortex phase circular polarization vector superposition so as to accurately measure the thickness uniformity of a light-transmitting measured object. The method comprises the following steps: the processor obtains a first vector polarization field collected by the phase detector when no detected object exists, after the detected object is placed between the polarization grating and the first vortex wave plate or the second vortex wave plate, a second vector polarization field collected by the phase detector is obtained, the polarization state difference value between the vector polarization field superposed when the detected object exists and the vector polarization field superposed when the detected object does not exist is compared, the phase distribution of each coordinate point on the cross section perpendicular to the optical axis in the light transmitting part of the detected object is obtained according to the circular polarization vector superposition principle, then the phase distribution of each coordinate point is unwrapped to obtain the phase retardation of each coordinate point on the cross section caused by the thickness, and then the thickness uniformity of the light transmitting part of the detected object is obtained according to the phase retardation of each coordinate point on the cross section.

Description

Detection system and method based on vortex phase circular polarization vector superposition
Technical Field
The invention relates to the technical field of optical detection, in particular to a detection system and a detection method based on vortex phase circular polarization vector superposition.
Background
With the development of modern industrial technologies, the requirement on high-precision detection technology is higher and higher.
In conventional optical detection, parameter information of an object to be detected is often inferred by changes in phase information or the like in interference fringes caused by reflection of the object to be detected. And the method needs four-step phase shift interference to obtain more accurate surface information, has complex operation and has high requirement on the accuracy of phase shift. Meanwhile, the reflection-based detection mechanism is not suitable for measuring the thickness uniformity of the transparent object to be measured.
Disclosure of Invention
The invention aims to disclose a detection system and a detection method based on vortex phase circular polarization vector superposition so as to accurately measure the thickness uniformity of a light-transmitting measured object.
In order to achieve the above object, the present invention discloses a detection system based on vortex phase circular polarization vector superposition, comprising:
the left-handed circularly polarized light generating assembly is used for generating left-handed circularly polarized light;
the right-handed circularly polarized light generating component is used for generating right-handed circularly polarized light;
the wavelength of a laser light source in the left-handed circularly polarized light generation assembly is equal to that of a laser light source in the right-handed circularly polarized light generation assembly;
the first vortex wave plate is positioned between the left-handed circularly polarized light generating assembly and the polarization grating;
the second vortex wave plate is positioned between the right-handed circularly polarized light generating assembly and the polarization grating;
the first vortex wave plate and the second vortex wave plate are vortex wave plates with the same order and are rounded;
the incident optical axis of the first vortex wave plate and the incident optical axis of the second vortex wave plate are respectively positioned on the positive and negative first-order diffraction angles of the polarization grating so as to deflect two beams of incident vortex light into combined light which has the same propagation direction and is subjected to vector superposition;
the phase detector is positioned in the emergent direction of the polarization grating and used for collecting the vector polarization field of the superposed beam combination light;
the transparent detected object is positioned between the polarization grating and the first vortex wave plate or the second vortex wave plate, and the phase delay amount of the light beam of the detected object is changed due to the thickness of the light transmission part;
and the processor is connected with the phase detector and used for comparing the polarization state difference value between the vector polarization field superposed when the detected object exists and the vector polarization field superposed when the detected object does not exist, obtaining the phase distribution of each coordinate point on the section vertical to the optical axis in the light transmission part of the detected object according to the circular polarization vector superposition principle, then unwrapping the phase distribution of each coordinate point to obtain the phase retardation caused by the thickness of each coordinate point on the section, and then solving according to the phase retardation of each coordinate point on the section to obtain the thickness uniformity of the light transmission part of the detected object.
Preferably, the order of the first vortex wave plate and the second vortex wave plate is equal to 1.
Preferably, in the process of obtaining the thickness uniformity of the light-transmitting portion of the detected object by solving according to the phase delay amount of each coordinate point on the cross section, the processor is specifically configured to: firstly, combining the phase delay of each coordinate point with the wavelength of a laser light source and the refractive index of an object to be detected to calculate the thickness information of each coordinate point on the cross section extending along the direction parallel to the optical axis; and then obtaining the thickness uniformity of the light transmission part of the detected object according to the thickness information of each coordinate point of the cross section extending along the direction parallel to the optical axis.
In order to achieve the above object, the present invention further discloses a detection method based on vortex phase circular polarization vector superposition, which includes:
deploying a detection system based on vortex phase circular polarization vector superposition as described above;
the processor acquires a first vector polarization field acquired by the phase detector when no detected object exists;
after the detected object is placed between the polarization grating and the first vortex wave plate or the second vortex wave plate, the processor obtains a second vector polarization field collected by the phase detector, compares a polarization state difference value between the vector polarization field superposed when the detected object exists and the vector polarization field superposed when the detected object does not exist, obtains phase distribution of each coordinate point on a cross section perpendicular to an optical axis in the light transmitting part of the detected object according to a circular polarization vector superposition principle, then obtains phase retardation caused by thickness of each coordinate point on the cross section after unwrapping the phase distribution of each coordinate point, and then solves and obtains thickness uniformity of the light transmitting part of the detected object according to the phase retardation of each coordinate point on the cross section.
The invention has the following beneficial effects:
the system is simple, practical and convenient to deploy, the polarization state difference value between the superimposed vector polarization field when the detected object exists and the superimposed vector polarization field when the detected object does not exist is compared, the phase distribution of each coordinate point on the section perpendicular to the optical axis in the light transmission part of the detected object is obtained according to the circular polarization vector superposition principle, then the phase distribution of each coordinate point is obtained after being unwrapped, the phase retardation amount of each coordinate point on the section caused by the thickness is obtained, the thickness uniformity of the light transmission part of the detected object is obtained by solving the phase retardation amount of each coordinate point on the section, the system error can be effectively eliminated, and the nanoscale high precision is ensured.
The present invention will be described in further detail below with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. In the drawings:
fig. 1 is a block diagram of a detection system based on vortex phase circular polarization vector superposition, which is disclosed by the embodiment of the invention.
Fig. 2 is a schematic diagram of a principle of superposition of circular polarization vectors based on vortex phase according to an embodiment of the present invention.
Fig. 3 is a schematic flow chart of a detection method based on vortex phase circular polarization vector superposition, which is disclosed by the embodiment of the invention.
Detailed Description
The embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.
Example 1
The embodiment discloses a detection system based on vortex phase circular polarization vector superposition, as shown in fig. 1, including:
the left-handed circular polarized light generation assembly 1 is used for generating left-handed circular polarized light.
And the right-handed circularly polarized light generating component 2 is used for generating right-handed circularly polarized light.
The wavelength of the laser light source in the left-handed circularly polarized light generating assembly is equal to that of the laser light source in the right-handed circularly polarized light generating assembly.
And the first vortex wave plate 3 is positioned between the left-handed circularly polarized light generation assembly and the polarization grating 5.
And the second vortex wave plate 4 is positioned between the right-handed circularly polarized light generation assembly and the polarization grating.
The first vortex wave plate and the second vortex wave plate are vortex wave plates with the same order and are rounded. Preferably, the order of the first vortex wave plate and the second vortex wave plate is 1. The smaller the order, the simpler the subsequent complexity of calculating the phase distribution, and as an alternative, the order of the first vortex wave plate and the second vortex wave plate may be the same as 2 or 3 or other positive integers.
The incident optical axis of the first vortex wave plate and the incident optical axis of the second vortex wave plate are respectively positioned on the positive and negative first-order diffraction angles of the polarization grating so as to deflect the two beams of incident vortex light into a beam combining light which has the same propagation direction and is superposed in vector.
And the phase detector 6 is positioned in the emergent direction of the polarization grating and is used for collecting the vector polarization field of the superposed beam combining light.
And the transparent detected object is positioned between the polarization grating and the first vortex wave plate or the second vortex wave plate, and the phase delay amount of the light beam of the detected object is changed due to the thickness of the light transmission part.
And the processor 7 is connected with the phase detector and used for comparing the polarization state difference value between the vector polarization field superposed when the detected object exists and the vector polarization field superposed when the detected object does not exist, obtaining the phase distribution of each coordinate point on the section perpendicular to the optical axis in the light transmitting part of the detected object according to the circular polarization vector superposition principle, then obtaining the phase retardation of each coordinate point on the section due to the thickness after unwrapping the phase distribution of each coordinate point, and then obtaining the thickness uniformity of the light transmitting part of the detected object according to the solution of the phase retardation of each coordinate point on the section.
Preferably, in the process of obtaining the thickness uniformity of the light transmission portion of the detected object by solving according to the phase delay amount of each coordinate point on the cross section, the processor is specifically configured to: firstly, combining the phase delay of each coordinate point with the wavelength of a laser light source and the refractive index of a detected object to calculate the thickness information of each coordinate point on the cross section extending along the direction parallel to the optical axis; and then obtaining the thickness uniformity of the light transmission part of the detected object according to the thickness information of each coordinate point of the cross section extending along the direction parallel to the optical axis.
In this embodiment, the principle of detection based on superposition of circularly polarized light vectors in this embodiment is specifically as follows:
any left-hand circular polarized light and any right-hand circular polarized light with the same frequency and amplitude can be subjected to vector superposition to obtain linear polarized light. Therefore, the overall polarization state distribution of the superposed light field can be obtained only by knowing the rule of vector superposition. The following is a specific derivation procedure.
As shown in fig. 2, according to the representation method of jones matrix, an arbitrary polarized light field distribution can be represented by a vector E:
Figure BDA0003871051610000041
wherein C is the intensity amplitude (since the corresponding point light intensity is consistent, the subsequent light intensity amplitude is represented by C);
Figure BDA0003871051610000042
indicating an initial phase of
Figure BDA0003871051610000043
The matrix represents the direction of a unit polarization state
Figure BDA0003871051610000044
The first element of the matrix represents the x-polarization component
Figure BDA0003871051610000045
The second element represents the y-polarization component
Figure BDA0003871051610000046
For example, in
Figure BDA0003871051610000047
I.e., representing a left-handed circular deviation).
Consider the superposition of any left-handed circular polarized light and any right-handed circular polarized light of the same frequency and amplitude at some point.
Arbitrary left circular polarized field vector E LCP Can be expressed as
Figure BDA0003871051610000048
Wherein
Figure BDA0003871051610000049
To this end, the initial phase of the left circularly polarized light; and the light field vector E in the arbitrary right circular polarizing field RCP Can be expressed as
Figure BDA00038710516100000410
Wherein
Figure BDA00038710516100000411
The initial phase of the right circular polarization; defining a phase difference mode
Figure BDA00038710516100000412
And phase common mode
Figure BDA00038710516100000413
Satisfies the following conditions:
Figure BDA00038710516100000414
then there are:
Figure BDA00038710516100000415
thus the light field vector E of any one of the superimposed points P Can be calculated as:
Figure BDA00038710516100000416
the result shows that any left-hand circular polarized light and any right-hand circular polarized light with the same frequency and amplitude can be subjected to vector superposition to obtain linear polarized light, and the polarization direction is determined by
Figure BDA00038710516100000417
(i.e., half the phase difference between the left-handed circularly polarized light and the right-handed circularly polarized light at that point). Therefore, the left-right rotation phase difference is different on different position coordinates of the superposed light field, so that the corresponding linear polarization states are different.
The linear polarization direction is represented by an included angle theta between the polarization direction and the positive direction of x, so that the polarization angle theta satisfies the following conditions:
Figure BDA00038710516100000418
superposing any left-handed circular polarized light and any right-handed circular polarized light with the same frequency and amplitude to obtain a linear polarized light polarization direction angle theta and a left-handed circular polarized light phase
Figure BDA00038710516100000419
And the right-hand circular polarization phase
Figure BDA00038710516100000420
The relationship of (c) is:
Figure BDA0003871051610000051
at the moment, when the phase of the right-handed circularly polarized light changes by delta phi, the linear polarization direction degree theta' obtained by superposition meets the following requirements:
Figure BDA0003871051610000052
the relationship between the phase change delta phi of the dextrorotation circular polarized light and the difference value of the polarization direction angles of the two superimposed linear polarizations can be obtained:
Δφ＝2(θ′-θ)
therefore, the polarization state direction theta of each point measured when no object to be detected exists 0 (x, y) and the direction of polarization θ of each point measured when an object is to be detected 1 The phase distribution of each point of the object to be detected can be obtained by substituting (x, y) into the formula
Figure BDA0003871051610000053
Figure BDA0003871051610000054
Since the polarization direction during the detection process has a value in the range of [0,2 π ], for example, the polarization direction should actually be π + 2N π (N is any integer), and the polarization direction detected is π. Thus directly calculating the obtained phase
Figure BDA0003871051610000055
Only within 0,2 pi) of the phase, a true continuous phase cannot be obtained.
At this time, the calculated phase is required to be matched
Figure BDA0003871051610000056
And unwrapping, namely connecting the truncated phases into continuous phases, wherein common two-dimensional unwrapping algorithms are divided into two types, namely a path tracking phase unwrapping algorithm for seeking an integral result and a path-independent condition, and a path-independent phase unwrapping algorithm for seeking a minimum norm solution. In this embodiment, the unwrapping calculation may be performed by using a least square algorithm in the second class to obtain the unwrapped continuous phase Δ Φ (x, y), and the core idea is that the gradient difference of the phase before and after unwrapping should be the minimum.
After the actual continuous phase Δ Φ (x, y) of each point is obtained, the thickness d (x, y) of each point of the object can be estimated:
Figure BDA0003871051610000057
wherein lambda is the wavelength of the laser source, and n is the refractive index corresponding to the material of the object to be detected.
Example 2
Corresponding to the above embodiments, the present embodiment discloses a detection method based on vortex phase circular polarization vector superposition, as shown in fig. 3, including the following steps:
s1, deploying a detection system based on vortex phase circular polarization vector superposition. The system, that is, the system of the above embodiment, may specifically refer to fig. 1, and is not described in detail.
And S2, the processor acquires a first vector polarization field collected by the phase detector when no detected object exists.
And S3, after the detected object is placed between the polarization grating and the first vortex wave plate or the second vortex wave plate, the processor acquires a second vector polarization field acquired by the phase detector, compares the polarization state difference between the vector polarization field superposed when the detected object exists and the vector polarization field superposed when the detected object does not exist, obtains the phase distribution of each coordinate point on the section perpendicular to the optical axis in the light transmission part of the detected object according to the circular polarization vector superposition principle, then decouples the phase distribution of each coordinate point to obtain the phase retardation caused by the thickness of each coordinate point on the section, and solves the thickness uniformity of the light transmission part of the detected object according to the phase retardation of each coordinate point on the section.
Preferably, the processor, in the process of obtaining the thickness uniformity of the light transmission portion of the detected object by solving according to the phase delay amount of each coordinate point on the cross section, specifically includes:
step S31, first, the phase retardation of each coordinate point is combined with the wavelength of the laser light source and the refractive index of the object to be detected to calculate the thickness information of each coordinate point on the cross section extending in the direction parallel to the optical axis.
And step S32, obtaining the thickness uniformity of the light transmission part of the detected object according to the thickness information of each coordinate point of the cross section extending along the direction parallel to the optical axis.
Therefore, in the embodiment, the second vector polarization field is compared with the first vector polarization field, so that the interference caused by the noise of the system when the detection object is not placed is effectively avoided.
In summary, the detection system and method based on vortex phase circular polarization vector superposition respectively disclosed by the embodiments of the present invention at least have the following beneficial effects:
the system is simple, practical and convenient to deploy, the polarization state difference value between the superimposed vector polarization field when the detected object exists and the superimposed vector polarization field when the detected object does not exist is compared, the phase distribution of each coordinate point on the cross section perpendicular to the optical axis in the light transmission part of the detected object is obtained according to the circular polarization vector superposition principle, then the phase distribution of each coordinate point is unwrapped to obtain the phase delay amount caused by the thickness of each coordinate point on the cross section, the thickness uniformity of the light transmission part of the detected object is obtained by solving according to the phase delay amount of each coordinate point on the cross section, and the nanoscale high precision is ensured.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. A detection system based on vortex phase circular polarization vector superposition is characterized by comprising:
the left-handed circularly polarized light generating assembly is used for generating left-handed circularly polarized light;
the right-handed circularly polarized light generating component is used for generating right-handed circularly polarized light;
the wavelength of a laser light source in the left-handed circularly polarized light generating assembly is equal to that of a laser light source in the right-handed circularly polarized light generating assembly;
the first vortex wave plate is positioned between the left-handed circularly polarized light generation assembly and the polarization grating;
the second vortex wave plate is positioned between the right-handed circularly polarized light generating assembly and the polarization grating;
the first vortex wave plate and the second vortex wave plate are vortex wave plates with the same order and are rounded;
the incident optical axis of the first vortex wave plate and the incident optical axis of the second vortex wave plate are respectively positioned on the positive and negative first-order diffraction angles of the polarization grating so as to deflect two beams of incident vortex light into combined light which has the same propagation direction and is subjected to vector superposition;
the phase detector is positioned in the emergent direction of the polarization grating and used for collecting the vector polarization field of the superposed beam combining light;
the transparent detected object is positioned between the polarization grating and the first vortex wave plate or the second vortex wave plate, and the phase delay amount of the light beam of the detected object is changed due to the thickness of the light transmission part;
and the processor is connected with the phase detector and used for comparing the polarization state difference value between the vector polarization field superposed when the detected object exists and the vector polarization field superposed when the detected object does not exist, obtaining the phase distribution of each coordinate point on the section perpendicular to the optical axis in the light transmitting part of the detected object according to the circular polarization vector superposition principle, then obtaining the phase delay amount caused by the thickness of each coordinate point on the section after unwrapping the phase distribution of each coordinate point, and then obtaining the thickness uniformity of the light transmitting part of the detected object according to the phase delay amount of each coordinate point on the section.
2. The vortex phase circular polarization vector superposition-based detection system according to claim 1, wherein the first vortex wave plate and the second vortex wave plate have the same order of 1.
3. The vortex phase circular polarization vector superposition-based detection system according to claim 1 or 2, wherein in the process of solving the thickness uniformity of the light-transmitting part of the detected object according to the phase delay amount of each coordinate point on the cross section, the processor is specifically configured to: firstly, combining the phase delay of each coordinate point with the wavelength of a laser light source and the refractive index of a detected object to calculate the thickness information of each coordinate point on the cross section extending along the direction parallel to the optical axis; and then obtaining the thickness uniformity of the light transmission part of the detected object according to the thickness information of each coordinate point of the cross section extending along the direction parallel to the optical axis.
4. A detection method based on vortex phase circular polarization vector superposition is characterized by comprising the following steps:
deploying a vortex phase circular polarization vector superposition-based detection system according to any one of claims 1 to 3;
the processor acquires a first vector polarization field collected by the phase detector when no detected object exists;
after the detected object is placed between the polarization grating and the first vortex wave plate or the second vortex wave plate, the processor obtains a second vector polarization field collected by the phase detector, compares polarization state difference values between the vector polarization field superposed when the detected object exists and the vector polarization field superposed when the detected object does not exist, obtains phase distribution of each coordinate point on a section perpendicular to an optical axis in the light transmission part of the detected object according to a circular polarization vector superposition principle, then obtains phase retardation caused by thickness of each coordinate point on the section after unwrapping the phase distribution of each coordinate point, and then obtains thickness uniformity of the light transmission part of the detected object according to the phase retardation of each coordinate point on the section.
5. The vortex phase circular polarization vector superposition-based detection method according to claim 4, wherein the first vortex wave plate and the second vortex wave plate have the same order of 1.
6. The detection method based on vortex phase circular polarization vector superposition according to claim 4 or 5, wherein the processor, in the process of solving the thickness uniformity of the light-transmitting part of the detected object according to the phase delay amount of each coordinate point on the cross section, specifically comprises:
firstly, combining the phase delay of each coordinate point with the wavelength of a laser light source and the refractive index of a detected object to calculate the thickness information of each coordinate point on the cross section extending along the direction parallel to the optical axis;
and then obtaining the thickness uniformity of the light transmission part of the detected object according to the thickness information of each coordinate point of the cross section extending along the direction parallel to the optical axis.
CN202211197385.6A 2022-09-29 2022-09-29 Detection system and method based on vortex phase circular polarization vector superposition Pending CN115451809A (en)

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