CN111289469A - Device and method for measuring ice layer refractive index distribution in ICF target pellet - Google Patents
Device and method for measuring ice layer refractive index distribution in ICF target pellet Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N2021/4173—Phase distribution
- G01N2021/418—Frequency/phase diagrams
Abstract
The invention discloses a device and a method for measuring the refractive index distribution of an ice layer in an ICF target pellet. The measuring method comprises the following steps: after the target pills are well positioned by using the backlight projection light path, acquiring a four-step phase-shift interference image of the target pills through an interference light path; performing operations such as phase solution, unwrapping, Zernike fitting and the like on the phase-shifting interferogram, and selecting two similar annular bands on the obtained wave surface; sequentially calculating the refractive index of the ring band and the reference refractive index by using an OPD-based inversion method, thereby obtaining the refractive index distribution; and (5) performing coordinate conversion again to obtain the refractive index distribution of the target pellet coordinate system. By using the invention, rapid and non-contact measurement can be realized.
Description
Technical Field
The invention belongs to the technical field of optical precision measurement, and particularly relates to a device and a method for measuring the refractive index distribution of an ice layer in an ICF target pellet.
Background
Inertial Confinement Fusion (ICF) requires a plurality of high-energy pulsed lasers to be simultaneously and uniformly irradiated on a target pellet to generate uniform implosion, thereby inducing nuclear fusion. The target pellet is a multilayer sphere composed of a spherical shell, an ice layer, fuel gas and the like, and in the process of condensing the ice layer, the inner surface of the ice layer is too rough, and air chambers exist in the layers. These inhomogeneities can be characterized as inhomogeneities in the thickness and refractive index profile, respectively, of the ice layer of the target pellet. This non-uniformity can lead to non-uniform implosion and thus nuclear fusion will not be induced. Therefore, the uniformity of the target pellet is an important parameter in inertial confinement fusion engineering.
The existing characterization of the uniformity of the target pellet focuses more on thickness uniformity, while there is less interest in the characterization of the refractive index uniformity. The laser fusion research center of China institute of engineering and physics utilizes an X-ray phase contrast imaging method (Optics Communications, 2014, VOL.332: P9-13.) to obtain the inner surface topography of the ice layer. The method can decouple the influence of the refractive indexes of the shell and the ice layer of the target pellet from the measurement result, and directly obtain the thickness of each layer of the target pellet. However, this approach is not practical for refractive index characterization of the layers. The NIF project in the United states uses a white light interferometer (Weinstein B W. white-light interferometric of the wall thickness of hollow glass microspheres [ J ] (Journal of applied Physics, 1975, VOL.46, No. 12: P5305-5306)), which can solve the thickness or refractive index when the refractive index or thickness of the target pellet shell is known. However, the refractive index solved by the method is only the average refractive index, and the refractive index distribution cannot be characterized. Beijing university of physical and chemical engineering combines low coherence interference and differential confocal optical path (Wang L, Qiu L, ZHao W, et al. laser differential coherent inner-surface profile measurement method for an ICFcapsule [ J ] (Optics Express, 2017, VOL.25, No. 23: P28510-28523)), scans the target pill at all angles through confocal, and obtains the inner surface distribution and the refractive index by using low coherence interference. However, the method does not give the final refractive index distribution, and needs to use confocal scanning to perform region-by-region scanning, which is time-consuming and difficult to realize online detection; in addition, the rotating mechanism of the target pill is complex, the requirement on hardware is high, and an adjustment error is introduced, so that the final detection result of the refractive index distribution is influenced. The characterization of the refractive index distribution of the ice layer in the target pellet by the detection method has no final result.
It is therefore desirable to design an apparatus and method for accurately measuring the refractive index profile of the ice layer within an ICF target pellet.
Disclosure of Invention
In order to overcome the defects in the prior art, the application provides a device and a method for measuring the ice layer refractive index distribution in an ICF target pellet, so that the rapid and non-contact measurement is realized, and the ice layer refractive index distribution in the target pellet is obtained.
A device for measuring the refractive index distribution of an ice layer in an ICF target pellet comprises an optical fiber laser, an optical fiber collimating mirror, a first polarization beam splitter, PZT (piezoelectric ceramics) carrying a plane reflector, a non-polarization beam splitter, a second polarization beam splitter, a target pellet to be measured, a lens, a linear polarizer, a CCD (charge coupled device) image sensor, a high-power LED, a diaphragm and a computer;
the optical fiber laser, the optical fiber collimator, the first polarization beam splitter and the plane reflector carried by the PZT are sequentially arranged along the same horizontal line, the optical fiber head of the optical fiber laser is inserted into the light inlet port of the optical fiber collimator, the light outlet port of the optical fiber collimator is aligned with the light inlet port of the first polarization beam splitter, and the light outlet port of the light transmitted by the first beam splitter and the plane reflector carried by the PZT are arranged at an angle of 45 degrees;
the high-power LED, the diaphragm, the second polarization beam splitter, the target pill to be detected, the non-polarization beam splitter, the lens, the linear polarizer and the CCD image sensor are sequentially arranged along a horizontal line in the direction parallel to the optical fiber laser; the second polarization beam splitter is arranged at the diaphragm light outlet and keeps longitudinally aligned with the first polarization beam splitter; the non-polarizing beam splitter and the plane mirror carried on the PZT keep longitudinal alignment; the CCD image sensor is connected with a computer and used for acquiring a phase-shifting interference pattern and a backlight projection pattern.
In the invention, the fiber laser and the high-power LED are respectively used as light sources of an interference detection light path and a backlight projection detection light path, and only one light source can be opened at the same time for respectively obtaining a phase-shifting interference pattern and a backlight projection pattern.
When a phase-shifting interference pattern is obtained, the setting distances of the rear surface of the target pill to be detected, the lens and the CCD image sensor meet the imaging conjugate relation; and when the backlight projection drawing is obtained, the setting distances of the longitudinal section of the target pill to be measured, the lens and the CCD image sensor meet the imaging conjugate relation.
The invention also provides a method for measuring the ice layer refractive index distribution in the ICF target pellets, which comprises the following steps of:
(1) installing an interference detection light path and a backlight projection detection light path; in the interference detection light path, laser emitted from a fiber laser is expanded by a fiber collimator and then becomes a collimated laser beam, and the collimated laser beam is divided into two beams by a first polarization beam splitter: one beam passes through the first polarization beam splitter and is reflected by a reflector carried on the PZT table to reach the second polarization beam splitter; the other beam is reflected by the non-polarization beam splitter after being reflected by the first polarization beam splitter, passes through the target pill to be detected, reaches the second polarization beam splitter to be combined with the first beam, passes through the lens and the linear polarizer, and is finally imaged on the CCD image sensor by the lens to obtain an interference pattern; wherein, the distances among the rear surface of the target pill to be measured, the lens and the CCD image sensor satisfy the imaging conjugate relation;
in the backlight projection detection light path, the light source of the fiber laser is closed, the high-power LED light source is opened, the aperture of a collimated light beam emitted from the high-power LED is reduced after passing through a diaphragm, and the collimated light beam is divided into two beams after passing through a polarization beam splitter: one beam is emitted out of the device; one beam passes through the target pill to be detected, then passes through a second polarization beam splitter, passes through a lens and a linear polarizer, and is finally imaged on a CCD image sensor by the lens to obtain a backlight projection drawing; processing the backlight projection image and the interference image acquired from the CCD image sensor in a computer; moving the target pill to enable the longitudinal section of the target pill to be detected, the lens and the distance of the CCD image sensor to meet the imaging conjugate relation;
(2) opening a PZT driver for the interference pattern which is acquired by the CCD image sensor and is stable and not jittered, carrying out four-step phase shifting operation on the interference pattern, and storing the obtained four-step phase shifting interference pattern;
(3) performing phase solution, unwrapping and Zernike fitting processing on the stored four-step phase-shift interferogram to obtain a wavefront map;
(4) corresponding to the interference detection light path, setting the light incidence height passing through the axis of the target pellet to be detected as 0, setting the vertical distance between the light incidence point and the axis of the target pellet to be detected as the incidence height as x, wherein x is a positive real number smaller than the inner radius of the target pellet; respectively tracing the incident light rays from the height of 0 and the height of x; the light with the incident height of 0 linearly passes through the target pellet to be measured and is received by the image surface center of the CCD image sensor; after the light with the incident height of x deflects for multiple times on each interface of the target pill to be measured, the distance between a point received by the CCD image sensor and the center of the image surface of the CCD image sensor is r;
let OPD be the corresponding optical path difference between the two rays when they are incident on and received by the CCD image sensor, resulting in equation (1):
OPL(x，n2(i，j))-OPL(0，n2c)＝OPD， (6)
wherein OPD is a constant, measured directly from the wavefront map, OPL (x, n)2) Is the optical path corresponding to the ray incident from height x, OPL (0, n)2) Is the optical path corresponding to the light incident from height 0; x is the incident height of light, n2(i，j)As the refractive index of the ice layer at the (i, j) th pixel point of the coordinate, n2cThe refractive index of the ice layer at the spherical center of the target pellet;
due to the deflection effect of the target pellet, the height of the light ray which is incident from the height x and is emitted from the rear surface of the target pellet and then imaged on the CCD image sensor is as follows:
x+Δx＝r， (7)
wherein x is the height of the light entering the target pellet, and Δ x is the deflection height of the light passing through the target pellet;
let two light rays with similar incident heights, and the corresponding incident light ray height and emergent light ray height are x1，x2And r1，r2(ii) a Based on these parameters and the above formulas (1) and (2), the method can be obtained simultaneously
In the formula (I), the compound is shown in the specification,
is from height x1The optical path corresponding to the incident light ray,
is from height x2The optical path corresponding to the incident light; Δ x1And Δ x2The heights of the two incident light beams after deflection of the target pellet can be derived through the heights of the incident light beams and the parameters of the target pellet; r is1And r2The emergent heights of the two rays passing through the target pellet can be directly measured on a wavefront chart;
the average refractive indexes of the two light rays at the corresponding positions of the target pellet are approximately considered to be equal;
solving the height x of the incident ray1，x2And the refractive indexes of the corresponding positions of the two light rays
(5) For an incident height x1The corresponding emergent ray height and the corresponding refractive index of the target pellet position are respectively r1，
Substituting the refractive index into formula (1) to obtain the following formula (4), and solving to obtain the refractive index n of the target pellet centercAs a reference fold(ii) a refractive index;
(6) for the light ray with incident light ray height x corresponding to each pixel, there are
In the formula, OPL (x, n)2(i，j)) Is the optical path corresponding to the ray incident from height x, OPL (0, n)2) Is the optical path corresponding to the light incident from height 0; x is the incident height of light, n2(i，j)As the refractive index of the ice layer at the (i, j) th pixel point of the coordinate, n2cThe refractive index of the ice layer at the spherical center of the target pellet; obtaining the refractive index distribution on the CCD image surface through the obtained ice layer refractive index on each pixel point;
(7) for the refractive index distribution on the CCD image surface, converting the refractive index distribution into the refractive index distribution under a target pellet coordinate system, specifically: by applying equation (5) to each pixel to synchronously solve for the incident ray height x for each pixel, a series of (x) s is obtained(i，j)，r(i，j)) Mapping relation, so that the refractive index distribution on the CCD image surface can be converted into a target pill coordinate system to obtain (x, n)2) And (4) relationship. Thereby obtaining the refractive index distribution of the ice layer of the target pellet.
According to the method, after the target pill is well positioned by using the backlight projection detection light path, a four-step phase interference pattern of the target pill is collected through the interference light path; performing operations such as phase solution, unwrapping, Zernike fitting and the like on the phase-shifting interferogram, and selecting two similar annular bands on the obtained wave surface; and (3) sequentially solving the refractive index of the ring band and the reference refractive index by using an inversion method based on the OPD, thereby obtaining the refractive index distribution. And (5) performing coordinate conversion again to obtain the refractive index distribution of the target pellet coordinate system.
In the step (1), in the backlight projection detection optical path, the target pill is positioned according to the sharpness judgment of the bright ring of the backlight projection image, and the interference detection optical path is positioned on the basis.
The specific steps of determining and positioning the target pill according to the sharpness of the bright ring of the backlight projection image are as follows:
the target pill is moved by a tiny step (generally 3-5 mu m), and the backlight projection images collected at all positions are filtered and the aperture is extracted. For these processed images, the sharpness of the annular region near the bright ring is calculated according to a gradient function. And finding out a backlight picture with the maximum sharpness, and moving the target pill to a corresponding position, so that the longitudinal section of the target pill to be detected, the distance between the lens and the CCD image sensor meet the imaging conjugate relation.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a refractive index distribution measuring method and device based on optical path difference for the first time, and the refractive index distribution of an ice layer of an ICF target pellet is measured; the target pellet is accurately positioned through one path of light path corresponding to the backlight projection, and the refractive indexes of all parts of the light path corresponding to the interference are solved based on the optical path difference, so that the refractive index distribution of the ice layer of the target pellet can be obtained.
2. Compared with the existing method combining low coherence interference and confocal, the method can realize rapid measurement and online detection because confocal scanning and target pill rotation are not required.
3. The interference detection light path and the backlight projection detection light path used in the device are both optical measurement methods, both have the advantages of rapid and non-contact measurement, and can realize the nondestructive detection of the target pill.
4. Compared with the traditional indirect measurement method for measuring the single parameter of the ice layer of the target pellet by the interferometry, the method does not use the standard target pellet and the parameters such as the standard refractive index and the like, belongs to direct measurement, and is more convenient compared with indirect measurement.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a device for measuring the refractive index distribution of an ice layer in an ICF target pellet according to the present invention;
FIG. 2 is a schematic diagram of the detection of the refractive index of an ice layer based on optical path difference;
FIG. 3 is a schematic diagram of the transformation from CCD image sensor coordinates to a world coordinate system;
FIG. 4 is a graph of the simulation result of the refractive index of the ice layer of the target pellet in the embodiment of the present invention.
Detailed Description
The invention will be described in further detail below with reference to the drawings and examples, which are intended to facilitate the understanding of the invention without limiting it in any way.
As shown in figure 1, the device for measuring the refractive index distribution of the ice layer in the ICF target pellet comprises an optical fiber laser 1, an optical fiber collimating mirror 2, a first polarization beam splitter 3, PZT (piezoelectric transducer) loaded with a plane reflector 4, a non-polarization beam splitter 5, a second polarization beam splitter 6, a target pellet 7 to be measured, a lens 8, a linear polarizer 9, a CCD (charge coupled device) image sensor 10, a high-power LED11, a diaphragm 12 and a computer 13.
The optical fiber laser device 1, the optical fiber collimating mirror 2, the first polarization beam splitter 3, the plane mirror 4 that the PZT uploaded puts along same water flat line in proper order, and the optical fiber head of optical fiber laser device 1 inserts the income light port of optical fiber collimating mirror 2, and the light-emitting window of optical fiber collimating mirror 2 aligns with the income light port of first polarization beam splitter 3, and the light-emitting window of the first polarization beam splitter 3 transmitted light is 45 settings with the plane mirror 4 that the PZT uploaded. And a high-power LED11, a diaphragm 12, a second polarization beam splitter 6, a target pill 7 to be detected, a non-polarization beam splitter 5, a lens 8, a linear polarizer 9 and a CCD image sensor 10 are sequentially arranged along a horizontal line in the direction parallel to the optical fiber laser 1. Wherein, the light outlet of the diaphragm 12 is positioned at the center of the high-power LED11 (secondary light emitting), and the second polarization beam splitter 6 is arranged at the light outlet of the diaphragm 12 and kept in longitudinal alignment with the first polarization beam splitter 3. The non-polarizing beam splitter 5 is held in longitudinal alignment with the plane mirror 4 carried on the PZT. The arrangement of the rear surface of the target pellet 7 to be measured, the lens 8 and the CCD image sensor 10 meets the object-image conjugate relation. The CCD image sensor 10 is connected with a computer 13 to acquire a phase-shift interference pattern 14 and a backlight projection pattern 15.
Based on the device, the method for measuring the ice layer refractive index distribution in the ICF target pellet comprises the following steps:
step 1: device light path
1-1. interference detection light path:
laser emitted from the optical fiber laser is expanded into a collimated laser beam through an optical fiber collimating lens, and the collimated laser beam is divided into two beams through a first polarization beam splitter: one beam passes through the first polarization beam splitter and is reflected by a plane mirror carried on the PZT table to reach the second polarization beam splitter; the other beam is reflected by the non-polarization beam splitter after being reflected by the first polarization beam splitter, passes through the target pill to be detected, reaches the second polarization beam splitter to be combined with the first beam, passes through the lens and the linear polarizer, and is finally imaged on the CCD image sensor by the lens to obtain an interference pattern; wherein the distances among the rear surface of the target pill, the lens and the CCD image sensor satisfy the imaging conjugate relation.
1-2. backlight projection detection light path
Closing the light source of the fiber laser, and opening the high-power LED light source; collimated light beams emitted from the high-power LED are reduced in aperture after passing through the diaphragm and divided into two beams after passing through the polarization beam splitter: one beam is emitted out of the device; one beam passes through the target pill to be detected, then passes through a second polarization beam splitter, passes through a lens and a linear polarizer, and is finally imaged on a CCD image sensor by the lens to obtain a backlight projection drawing; and processing the backlight projection image and the interference image acquired from the CCD image sensor in a computer. And moving the target pill to enable the longitudinal section of the target pill, the lens and the distance of the CCD image sensor to meet the imaging conjugate relation. The backlight projection path positions the target pill according to the sharpness judgment of the bright ring of the backlight projection image, and the interference path positions on the basis.
Step 2: and (3) turning on a PZT driver for the interference pattern which is collected by the CCD image sensor and is stable and not jittered, and carrying out four-step phase shifting operation on the interference pattern. The resulting four-step phase-shifted interferogram is saved.
And step 3: and performing phase solution, unwrapping and Zemike fitting processing on the stored four-step phase-shift interferogram to obtain a wavefront map.
And 4, step 4: corresponding to the interference detection optical path; referring to fig. 2, the incident height of the light beam passing through the axis of the target pellet is set to 0, the vertical distance between the incident point of the light beam and the axis of the target pellet is set to x, and x is a positive real number smaller than the inner radius of the target pellet. Tracing the light incident from height 0 and height x, respectively. The light with the incident height of 0 linearly penetrates through the target pill to be detected and is received by the CCD image sensor, and the point received by the CCD image sensor is positioned at the center of the image surface of the CCD image sensor; and the light with the incident height of x has multiple deflections on each interface of the target pill to be measured, and the distance from the point, which is received by the CCD image sensor, corresponding to the light to the image surface center of the CCD image sensor is r. Let the corresponding optical path difference of the two light rays from the incidence to the CCD image sensor as OPD, where OPD is a constant, and can be directly measured from the wavefront map, the equation (6) is obtained:
OPL(x，n2(i，j))-OPL(0，n2c)＝OPD， (11)
wherein, OPL (x, n)2) Is the optical path corresponding to the ray incident from height x, OPL (0, n)2) Is the optical path corresponding to the light incident from height 0; x is the incident height of light, n2(i，j)As the refractive index of the ice layer at the (i, j) th pixel point of the coordinate, n2cIs the refractive index of the ice layer at the center of the target pellet.
Due to the deflection of the target pellet, the height of the light ray incident from the height x exiting the rear surface of the target pellet and imaged on the CCD image sensor is no longer x. Equation (7) is set according to geometric relations:
x+Δx＝r， (12)
wherein x is the height of the light incident on the target pellet, and Δ x is the height of the light deflected by the target pellet.
Let two light rays with similar incident heights, and the corresponding incident light ray height and emergent light ray height are x1，x2And r1，r2. These parameters and the expressions (6) and (7) can be used in combination
In the formula (I), the compound is shown in the specification,
is from height x1The optical path corresponding to the incident light ray,
is from height x2The optical path corresponding to the incident light; Δ x1And Δ x2The heights of the two incident light beams after deflection of the target pellet can be derived through the heights of the incident light beams and the parameters of the target pellet; r is1And r2The emergent heights of the two rays passing through the target pellet can be directly measured on a wavefront chart;
the average refractive index of the two rays at the corresponding locations where they passed through the target pellet can be approximated as equal because the two rays are very close. Where the unknown is the incident ray height x1，x2And the refractive indexes of the corresponding positions of the two light rays
The solution can be accomplished by the simultaneous connection of three equations.
And 5: for an incident height x1The corresponding emergent ray height and the corresponding refractive index of the target pellet position are respectively r1，
The light passing through the center of the target pellet (i.e., the incident height is 0) is applied to the formula (6) having,
wherein the unknown number is the refractive index n of the sphere center of the target pillc. Solving the equation can solve the unknowns. The refractive index of the sphere center of the target pellet is taken as a reference refractive index, and is the basis for solving the refractive index distribution.
Step 6: for light rays with an incident height x, there are
Wherein OPL (A) isx，n2(i，j)) Is the optical path corresponding to the ray incident from height x, OPL (0, n)2) Is the optical path corresponding to the light incident from height 0; x is the incident height of light, n2(i，j)As the refractive index of the ice layer at the (i, j) th pixel point of the coordinate, n2cIs the refractive index of the ice layer at the center of the target pellet. Unknown numbers x and n2(i，j)It can be solved by two equations. The refractive index at each pixel location can be solved by applying equation (10) to each pixel.
And 7: the incident light height x corresponding to each pixel synchronously solved according to the formula (10) can convert the uneven coordinates after the target pill into even coordinates to obtain (x, n)2) The relationship is as shown in FIG. 3. Namely the refractive index distribution of the target pellet ice layer.
A total of 4 real ICF target pellets of varying size and parameters were subjected to simulation experiments as shown in table 1.
TABLE 1
The refractive index distribution of the ice layer in the target pellet is solved by using the device and the method of the invention. Taking the target pellet # 1 as an example, the phase-shift interferogram is first dephased and unwrapped to obtain a phase distribution diagram as shown in fig. 4 (a). And (4) applying steps 4, 5, 6 and 7 to obtain the reference position refractive index, the reference refractive index, the pixel surface refractive index distribution and the ice layer refractive index distribution in sequence according to the phase distribution diagram. Fig. 4 (b) shows the results of the ice layer refractive index distribution of the No.1 target pellet. The refractive index profile obtained by the final inversion is very small for all 4 target shots, with a relative error of almost 0.
The embodiments described above are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions and equivalents made within the scope of the principles of the present invention should be included in the scope of the present invention.
Claims (6)
1. A device for measuring the refractive index distribution of an ice layer in an ICF target pellet is characterized by comprising an optical fiber laser (1), an optical fiber collimating mirror (2), a first polarization beam splitter (3), PZT (piezoelectric transducer) loaded with a plane reflector (4), a non-polarization beam splitter (5), a second polarization beam splitter (6), a target pellet to be measured (7), a lens (8), a linear polarizer (9), a CCD (charge coupled device) image sensor (10), a high-power LED (11), a diaphragm (12) and a computer (13);
the optical fiber laser (1), the optical fiber collimator (2), the first polarization beam splitter (3) and the plane reflector (4) carried by the PZT are sequentially arranged along the same horizontal line, the optical fiber head of the optical fiber laser (1) is inserted into the light inlet of the optical fiber collimator (2), the light outlet of the optical fiber collimator (2) is aligned with the light inlet of the first polarization beam splitter (3), and the light outlet of the transmission light of the first beam splitter (3) and the plane reflector (4) carried by the PZT are arranged at an angle of 45 degrees;
a high-power LED (11), a diaphragm (12), a second polarization beam splitter (6), a target pill to be detected (7), a non-polarization beam splitter (5), a lens (8), a linear polarizer (9) and a CCD image sensor (10) are sequentially arranged along a horizontal line in the direction parallel to the optical fiber laser (1); the light outlet of the diaphragm (12) is positioned at the right center of the high-power LED (11), and the second polarization beam splitter (6) is arranged at the light outlet of the diaphragm (12) and is kept in longitudinal alignment with the first polarization beam splitter (3); the non-polarizing beam splitter (5) and the plane mirror (4) carried on the PZT keep longitudinal alignment; the CCD image sensor (10) is connected with a computer (13) and is used for acquiring a phase-shifting interference pattern and a backlight projection pattern.
2. The apparatus for measuring the refractive index distribution of the ice layer within the ICF target pellet as defined in claim 1, wherein the fiber laser (1) and the high power LED (11) are used as the light source of the interference detection path and the backlight projection detection path, respectively, and only one of the two light sources is turned on at the same time for obtaining the phase-shifted interference pattern and the backlight projection pattern, respectively.
3. The device for measuring the refractive index distribution of the ice layer in the ICF target pellets according to claim 2, wherein the arrangement distances of the rear surface of the target pellet (7) to be measured, the lens (8) and the CCD image sensor (10) satisfy the imaging conjugation relationship when the phase-shifting interferogram is obtained; when a backlight projection drawing is obtained, the arrangement distance of the longitudinal section of the target pill (7) to be measured, the lens (8) and the CCD image sensor (10) meets the imaging conjugate relation.
4. A method for measuring the refractive index distribution of an ice layer in an ICF target pellet, which comprises the steps of using the measuring device according to any one of claims 1 to 3:
(1) installing an interference detection light path and a backlight projection detection light path; in the interference detection light path, laser emitted from a fiber laser is expanded by a fiber collimator and then becomes a collimated laser beam, and the collimated laser beam is divided into two beams by a first polarization beam splitter: one beam passes through the first polarization beam splitter and is reflected by a reflector carried on the PZT table to reach the second polarization beam splitter; the other beam is reflected by the non-polarization beam splitter after being reflected by the first polarization beam splitter, passes through the target pill to be detected, reaches the second polarization beam splitter to be combined with the first beam, passes through the lens and the linear polarizer, and is finally imaged on the CCD image sensor by the lens to obtain an interference pattern; wherein, the distances among the rear surface of the target pill to be measured, the lens and the CCD image sensor satisfy the imaging conjugate relation;
in the backlight projection detection light path, the light source of the fiber laser is closed, the high-power LED light source is opened, the aperture of a collimated light beam emitted from the high-power LED is reduced after passing through a diaphragm, and the collimated light beam is divided into two beams after passing through a polarization beam splitter: one beam is emitted out of the device; one beam passes through the target pill to be detected, then passes through a second polarization beam splitter, passes through a lens and a linear polarizer, and is finally imaged on a CCD image sensor by the lens to obtain a backlight projection drawing; processing the backlight projection image and the interference image acquired from the CCD image sensor in a computer; moving the target pill to enable the longitudinal section of the target pill to be detected, the lens and the distance of the CCD image sensor to meet the imaging conjugate relation;
(2) opening a PZT driver for the interference pattern which is acquired by the CCD image sensor and is stable and not jittered, carrying out four-step phase shifting operation on the interference pattern, and storing the obtained four-step phase shifting interference pattern;
(3) performing phase solution, unwrapping and Zernike fitting processing on the stored four-step phase-shift interferogram to obtain a wavefront map;
(4) corresponding to the interference detection light path, setting the light incidence height passing through the axis of the target pellet to be detected as 0, setting the vertical distance between the light incidence point and the axis of the target pellet to be detected as the incidence height as x, wherein x is a positive real number smaller than the inner radius of the target pellet; respectively tracing the incident light rays from the height of 0 and the height of x; the light with the incident height of 0 linearly passes through the target pellet to be measured and is received by the image surface center of the CCD image sensor; after the light with the incident height of x deflects for multiple times on each interface of the target pill to be measured, the distance between a point received by the CCD image sensor and the center of the image surface of the CCD image sensor is r;
let OPD be the corresponding optical path difference between the two rays when they are incident on and received by the CCD image sensor, resulting in equation (1):
OPL(x，n2(i，j))-OPL(0，n2c)＝OPD， (1)
wherein OPD is a constant, measured directly from the wavefront map, OPL (x, n)2) Is the optical path corresponding to the ray incident from height x, OPL (0, n)2) Is the optical path corresponding to the light incident from height 0; x is the incident height of light, n2(i，j)As the refractive index of the ice layer at the (i, j) th pixel point of the coordinate, n2cThe refractive index of the ice layer at the spherical center of the target pellet;
due to the deflection effect of the target pellet, the height of the light ray which is incident from the height x and is emitted from the rear surface of the target pellet and then imaged on the CCD image sensor is as follows:
x+Δx＝r， (2)
wherein x is the height of the light entering the target pellet, and Δ x is the deflection height of the light passing through the target pellet;
let two light rays with similar incident heights, and the corresponding incident light ray height and emergent light ray height are x1，x2And r1，r2(ii) a Based on these parameters and the above formulas (1) and (2), the method can be obtained simultaneously
In the formula (I), the compound is shown in the specification,
is from height x1The optical path corresponding to the incident light ray,
is from height x2The optical path corresponding to the incident light; Δ x1And Δ x2The heights of the two incident light beams after deflection of the target pellet can be derived through the heights of the incident light beams and the parameters of the target pellet; r is1And r2The emergent heights of the two rays passing through the target pellet can be directly measured on a wavefront chart;
the average refractive indexes of the two light rays at the corresponding positions of the target pellet are approximately considered to be equal;
solving the height x of the incident ray1，x2And the refractive indexes of the corresponding positions of the two light rays
(5) For an incident height x1The corresponding emergent ray height and the corresponding refractive index of the target pellet position are respectively r1，
Substituting the refractive index into formula (1) to obtain the following formula (4), and solving to obtain the refractive index n of the target pellet centercAs a reference refractive index;
(6) for the light ray with incident light ray height x corresponding to each pixel, there are
In the formula, 0PL (x, n)2(i，j)) Is the optical path corresponding to the ray incident from height x, OPL (0, n)2) Is the optical path corresponding to the light incident from height 0; x is the incident height of light, n2(i，j)As the refractive index of the ice layer at the (i, j) th pixel point of the coordinate, n2cThe refractive index of the ice layer at the spherical center of the target pellet; obtaining the refractive index distribution on the CCD image surface through the obtained ice layer refractive index on each pixel point;
(7) for the refractive index distribution on the CCD image surface, converting the refractive index distribution into the refractive index distribution under a target pellet coordinate system, specifically: by applying equation (5) to each pixel to synchronously solve for the incident ray height x for each pixel, a series of (x) s is obtained(i，j)，r(i，j)) Mapping relation, so that the refractive index distribution on the CCD image surface can be converted into a target pill coordinate system to obtain (x, n)2) Thereby obtaining the refractive index distribution of the ice layer of the target pellet.
5. The method of claim 4, wherein in step (1), the step of positioning the target pellet is performed based on a sharpness determination of a bright ring of the back-projected image in the back-projected detection optical path, and the step of positioning is performed based on the interference detection optical path.
6. The method of claim 5, wherein the step of determining the sharpness of the bright ring of the back-lit projection pattern is further characterized by the steps of:
moving the target pills in a micro step length of 3-5 mu m, and carrying out operations such as filtering, aperture extraction and the like on the backlight projection images collected at all positions; calculating the sharpness of an annular area near the bright ring according to a gradient function aiming at the processed images; and finding out a backlight picture with the maximum sharpness, and moving the target pill to a corresponding position, so that the longitudinal section of the target pill to be detected, the distance between the lens and the CCD image sensor meet the imaging conjugate relation.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113552094A (en) * | 2021-07-21 | 2021-10-26 | 浙江大学 | Measuring device and measuring method for ICF target pellet ice layer refractive index three-dimensional reconstruction |
| CN114111565A (en) * | 2021-11-25 | 2022-03-01 | 中国工程物理研究院激光聚变研究中心 | Multi-azimuth joint diagnosis speed interferometer |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61100640A (en) * | 1984-10-24 | 1986-05-19 | Canon Inc | Measurement of optical characteristic of glass material |
| CN101952683A (en) * | 2007-10-30 | 2011-01-19 | 苏州信达光电科技有限公司 | Methods and systems for white light interferometry and characterization of films |
| CN102147240A (en) * | 2010-12-24 | 2011-08-10 | 北京理工大学 | Method and device for measuring multiple element parameters in differential con-focus interference manner |
| US20160139296A1 (en) * | 2013-07-09 | 2016-05-19 | Halliburton Energy Services, Inc. | Integrated computational elements with laterally-distributed spectral filters |
| CN107449756A (en) * | 2017-06-22 | 2017-12-08 | 浙江大学 | Ice sheet refractive index and the measuring method and device of thickness in a kind of ICF pellets |
| EP3290921A1 (en) * | 2002-05-09 | 2018-03-07 | The University of Chicago | Device and method for pressure-driven plug transport and reaction |
| CN108333145A (en) * | 2018-01-02 | 2018-07-27 | 浙江大学 | A kind of the detection new equipment and localization method of ICF pellets |
| CN109580182A (en) * | 2018-12-18 | 2019-04-05 | 北京理工大学 | Curved optical device refractive index measurement method and device based on Brewster's law |
-
2020
- 2020-02-28 CN CN202010133607.2A patent/CN111289469B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61100640A (en) * | 1984-10-24 | 1986-05-19 | Canon Inc | Measurement of optical characteristic of glass material |
| EP3290921A1 (en) * | 2002-05-09 | 2018-03-07 | The University of Chicago | Device and method for pressure-driven plug transport and reaction |
| CN101952683A (en) * | 2007-10-30 | 2011-01-19 | 苏州信达光电科技有限公司 | Methods and systems for white light interferometry and characterization of films |
| CN102147240A (en) * | 2010-12-24 | 2011-08-10 | 北京理工大学 | Method and device for measuring multiple element parameters in differential con-focus interference manner |
| US20160139296A1 (en) * | 2013-07-09 | 2016-05-19 | Halliburton Energy Services, Inc. | Integrated computational elements with laterally-distributed spectral filters |
| CN107449756A (en) * | 2017-06-22 | 2017-12-08 | 浙江大学 | Ice sheet refractive index and the measuring method and device of thickness in a kind of ICF pellets |
| CN108333145A (en) * | 2018-01-02 | 2018-07-27 | 浙江大学 | A kind of the detection new equipment and localization method of ICF pellets |
| CN109580182A (en) * | 2018-12-18 | 2019-04-05 | 北京理工大学 | Curved optical device refractive index measurement method and device based on Brewster's law |
Non-Patent Citations (1)
| Title |
|---|
| TIANLIANG YAN 等: "ICF target DT-layer refractive index and thickness from iterative analysis", 《OPTICS EXPRESS》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113552094A (en) * | 2021-07-21 | 2021-10-26 | 浙江大学 | Measuring device and measuring method for ICF target pellet ice layer refractive index three-dimensional reconstruction |
| CN114111565A (en) * | 2021-11-25 | 2022-03-01 | 中国工程物理研究院激光聚变研究中心 | Multi-azimuth joint diagnosis speed interferometer |
| CN114111565B (en) * | 2021-11-25 | 2023-09-22 | 中国工程物理研究院激光聚变研究中心 | Multidirectional combined diagnosis speed interferometer |
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