CN114935310A - Device and method for measuring micro displacement of liquid jet surface - Google Patents
Device and method for measuring micro displacement of liquid jet surface Download PDFInfo
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- CN114935310A CN114935310A CN202210488770.XA CN202210488770A CN114935310A CN 114935310 A CN114935310 A CN 114935310A CN 202210488770 A CN202210488770 A CN 202210488770A CN 114935310 A CN114935310 A CN 114935310A
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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
- G01B11/028—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring lateral position of a boundary of the object
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
- G06T7/85—Stereo camera calibration
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30244—Camera pose
Abstract
The invention discloses a device and a method for measuring micro displacement on the surface of liquid jet, wherein the device comprises: the device comprises a laser, a precision displacement table, a blade, a liquid jet generation assembly, a standard slit, a polarization dimmer and an imaging assembly; the laser, the precision displacement table, the blade, the liquid jet generation assembly, the polarization dimmer and the imaging assembly are sequentially arranged and are all fixed at the top of the optical platform; the blade and the standard slit are positioned on the same plane, and the standard slit is fixed at the top of the optical platform; the blade is fixed at the moving end of the precision displacement table, and the precision displacement table drives the blade to move in three dimensions; the bottom of the liquid jet generating component forms liquid jet, and the slit between the blade and the liquid jet is equal to the slit width of a standard slit. The device has simple structure and convenient adjustment, and can improve the resolution ratio of liquid jet boundary displacement measurement.
Description
Technical Field
The invention relates to the technical field of optical experimental instruments, in particular to a device and a method for measuring micro displacement on the surface of liquid jet.
Background
The liquid jet breaking is a long-history fluid mechanics research content, and the research results are widely applied to the fields of ink-jet printing, pharmaceutical liquid, rocket engine propellant atomization and the like. A great deal of current research on free jet break-up of liquids suggests that there is a small initial disturbance of the jet surface, the amplitude of which increases exponentially along the jet, and when the amplitude is comparable to the jet diameter, the jet break-up is considered to form droplets. Although the exponential growth phenomenon of surface perturbations has been verified by a number of experiments, the theoretical and experimental aspects are not yet conclusive as to the origin of this initial perturbation.
The research on the initial disturbance of the liquid jet can be realized by measuring the displacement of a liquid jet interface near a nozzle, and the research means is mainly realized by a microscopic-high-speed photography technology, namely the combination of a microscope lens and a high-speed camera. According to imaging theory, an ideal infinitesimal light source forms a finite-sized airy disk by diffraction through a microscope, and the diameter of the airy disk limits the highest resolution of microscopic imaging, called optical resolution. Based on previous microscopic observations of the liquid jet interface near the nozzle orifice, it has been found that the amplitude is not sufficiently resolved by means of a microscope, and thus conventional microscopic imaging systems have limitations in studying the initial perturbation of the liquid jet.
Therefore, it is an urgent need to solve the problems of the art to develop a device and a method for measuring micro displacement on the surface of a liquid jet, which has a simple structure and is convenient to adjust and can improve the resolution of liquid jet boundary displacement measurement.
Disclosure of Invention
In view of this, the invention provides a device and a method for measuring micro displacement on the surface of a liquid jet, which have the advantages of simple structure, convenient adjustment and capability of improving the resolution of liquid jet boundary displacement measurement.
In order to achieve the purpose, the invention adopts the following technical scheme:
an apparatus for measuring micro-displacements of a surface of a liquid jet, comprising: the device comprises a laser, a precision displacement table, a blade, a liquid jet generation assembly, a standard slit, a polarization dimmer and an imaging assembly;
the laser, the precise displacement table, the blade, the liquid jet generation assembly, the polarization dimmer and the imaging assembly are sequentially arranged and are all fixed at the top of the optical platform; the blade and the standard slit are positioned on the same plane, and the standard slit is fixed at the top of the optical platform;
the blade is fixed at the moving end of the precision displacement table, and the precision displacement table drives the blade to move in three dimensions;
the bottom of the liquid jet generation component forms a liquid jet, and the slit between the blade and the liquid jet is equal to the slit width of the standard slit.
The technical scheme has the advantages that the slit is formed by using the liquid jet boundary and the knife edge reference edge on the basis of slit Fraunhofer diffraction, tiny displacement of the liquid jet boundary is amplified through diffraction, diffraction stripes are shot through the imaging assembly, and the surface displacement of the liquid jet is calculated by measuring the variation of the position of a certain level of dark stripes, so that the measurement of the optical resolution higher than that of the traditional microscope is realized.
Preferably, the axis of the laser beam of the laser is collinear with the axis of the lens of the imaging assembly.
Preferably, the width of a slit between the blade and the liquid jet is 0.05-0.1 mm, and the width of the slit of the standard slit is 0.1 mm.
Preferably, the liquid jet generating assembly comprises: the injection pump comprises an injection pump and a fine nozzle, wherein the fine nozzle is fixed at the bottom outlet of the injection pump, and liquid flows out of the outlet of the fine nozzle to form liquid jet.
Preferably, the imaging assembly comprises: the microscope is fixed on one side, close to the polarizing dimmer, of the high-speed camera.
Preferably, the polarization dimmer comprises two polarizers, and the polarization direction of the polarizers can be adjusted by rotating the polarizers. The two polarizers are axially fixed together through a shell and can rotate relatively, and the polarization direction of the polarizers can be adjusted by rotating the polarizers; the polarizer can absorb light waves with the same polarization direction, so that the light waves cannot pass through; the incident laser has two polarization components which are vertical to each other, and if two polarizers are used and the polarization directions of the two polarizers are vertical to each other, the laser can be completely blocked; if the polarization directions of the two are not perpendicular to form a certain included angle, the laser can be partially blocked. In the using process, the light intensity of the laser passing through the polarizer group can be changed by fixing the angle of one polarizer and rotating the other polarizer. The arrangement of the polarization dimmer can protect a CMOS sensor in the high-speed camera; before the laser is started, the polarization directions of the two polarizers are adjusted to be vertical, laser cannot pass through the two polarizers at the moment, and after the laser is started, one of the polarizers is rotated, so that the laser imaging brightness in the picture of the high-speed camera is proper.
A measuring method of a device for measuring micro displacement of the surface of a liquid jet flow comprises the following steps:
1) firstly, adjusting a laser light column of the laser to be coaxial with a microscope in the imaging assembly, and adjusting the imaging of the laser light column to be at the center of a high-speed camera in the imaging assembly so that the laser light column of the laser is coaxial with the microscope in the imaging assembly;
2) adjusting the standard slit to be coplanar with the liquid jet generating assembly;
3) calibrating the standard slit, starting the laser, and adjusting the distance between the imaging component and the standard slit to enable fourth-level dark fringe stripes on the left side and the right side of the high-speed camera to be close to the picture boundary;
4) the relationship between parameters of Fraunhofer slit diffraction is as follows:
wherein b is the slit width; k is the dark fringe level; l is the distance from the slit to the imaging surface; λ is the wavelength of light; x is the number of k The distance between the center of the kth-level dark fringe and the center of the central zero-level fringe is shown;
acquiring horizontal gray level distribution of stripes in the photo acquired in the step 3) through image processing software, wherein the position with zero gray level is a dark stripe position; center light acquisition by image processing softwareThe fourth gray scale on both sides of the texture is the pixel abscissa of the zero point, and the difference between the two pixel abscissas is 2y 4,s (ii) a And according to the size of a single pixel of the high-speed camera as sigma, obtaining the position x of the four-level dark fringe 4,s ＝y 4,s σ, four-level dark fringe position x formed by standard slit (5) 4,s Replacing x in the above formula k Width b of standard slit (5) s Replacing b in the formula, and setting k to 4, the equivalent distance between the plane of the standard slit (5) and the imaging plane of the imaging assembly (7) can be calculated:
5) after the calibration link is completed, the laser is closed, the imaging component and the laser are horizontally moved to enable the liquid jet boundary to be positioned in the center of the picture, and the relative positions of the laser and the imaging component are kept fixed in the process; adjusting the position of the blade by using the precision displacement table to enable the blade edge and the liquid jet boundary to form a slit, wherein the width of the slit is determined by amplifying and measuring an imaging component;
6) after the adjustment of the slit between the edge of the blade and the liquid jet boundary is completed, starting the laser and shooting a diffraction stripe picture;
7) measuring the position x of the four-level dark stripe in the photo of the step 6) 4 The change of (2): firstly, acquiring the horizontal gray level distribution of the stripes in the photo in the step 6) through image processing software, wherein the position with zero gray level is the position of the dark stripe, acquiring pixel horizontal coordinates with fourth gray levels at two sides of the central bright stripe as zero points through the image processing software, and the difference between the two pixel horizontal coordinates is 2y 4 (ii) a And according to the size of a single pixel of the high-speed camera as sigma, obtaining the position x of the four-level dark fringe 4 ＝y 4 σ, and then the four-level dark fringe position x of each photo 4 Substituting the following equation to obtain the slit width b, wherein b and x in the equation 4 Both vary with respect to time as a function of time:
8) the magnification a of the slit between the edge of the blade and the liquid jet boundary is obtained according to the following formula,
wherein d is a differential operator,
refers to x k And b is differentiated, and the resolution of the device is determined by the magnification factor A.
The technical scheme has the advantages that when the standard slit is calibrated, the distance between the imaging component and the standard slit is adjusted, so that fourth-level dark stripe stripes on the left side and the right side of the high-speed camera are close to the boundary of a picture, the ratio of a measurement area in the picture can be improved, and the measurement precision is improved; and the width of the slit is amplified through diffraction, so that the imaging component is improved on the basis of the original resolution, and the limitation of the resolution of the original imaging component is overcome.
According to the technical scheme, compared with the prior art, the invention discloses a device and a method for measuring the micro displacement of the surface of the liquid jet, and the device and the method have the beneficial effects that:
(1) according to the invention, slit Fraunhofer diffraction is used as a basis, a slit is formed by using a liquid jet boundary and a knife edge reference edge, tiny displacement of the liquid jet boundary is amplified through diffraction, diffraction stripes are shot through an imaging component, and the surface displacement of the liquid jet is calculated by measuring the variation of the position of a certain level of dark stripes, so that the measurement of the optical resolution higher than that of a traditional microscope is realized;
(2) the device of the invention has simple structure and convenient adjustment, and can be widely applied to various liquid jet experiments.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic view of the structure of the apparatus provided by the present invention;
FIG. 2 is a light path diagram of the device provided by the present invention during measurement;
FIG. 3 is an enlarged view of the invention at A in FIG. 2;
FIG. 4 is a schematic diagram of diffraction fringes formed during measurement by the device provided by the present invention;
fig. 5 is a measurement flow chart of the apparatus provided by the present invention.
Wherein, in the figure,
1-a laser; 2-a precision displacement table; 3-a blade; 4-a liquid jet generating assembly; 5-standard slit; 6-a polarization dimmer; 7-an imaging assembly; 8-an optical bench; 9-laser light beam; 10-position of the fourth order dark fringe of the diffraction fringe.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
the embodiment of the invention discloses a device for measuring the micro displacement of the surface of liquid jet, which comprises: the device comprises a laser 1, a precision displacement table 2, a blade 3, a liquid jet generation assembly 4, a standard slit 5, a polarization dimmer 6 and an imaging assembly 7;
the laser 1, the precision displacement table 2, the blade 3, the liquid jet flow generation assembly 4, the polarization dimmer 6 and the imaging assembly 7 are sequentially arranged and fixed at the top of the optical platform 8; the blade 3 and the standard slit 5 are positioned on the same plane, and the standard slit 5 is fixed at the top of the optical platform 8;
the blade 3 is fixed at the moving end of the precision displacement table 2, and the precision displacement table 2 drives the blade 3 to move in three dimensions;
the bottom of the liquid jet generating assembly 4 forms a liquid jet, and the slit between the blade 3 and the liquid jet is equal to the slit width of a standard slit 5. According to the slit Fraunhofer diffraction theory, the slit width and the distance between the slit and the imaging surface are adjusted, so that the slit width is in certain relation with the diffraction fringes on the imaging surface, and the change of the diffraction fringes has an amplification effect on the change of the slit width. The laser 1 generates green parallel line laser light with a wavelength of 532mm, and since the laser light is parallel light, the distance between the plane where the slit is located and the laser 1 has no influence on the measurement, and the distance is set to be 100mm in the present embodiment.
In order to further optimize the above solution, the axis of the laser beam 9 of the laser 1 is collinear with the axis of the lens of the imaging assembly 7.
In order to further optimize the technical scheme, the width of the slit between the blade 3 and the liquid jet is 0.05-0.1 mm, and the width of the slit of the standard slit 5 is 0.1 mm.
In order to further optimize the above solution, the liquid jet generating assembly 4 comprises: the injection pump comprises an injection pump and a fine nozzle, wherein the fine nozzle is fixed at an outlet at the bottom of the injection pump, and liquid flows out of an outlet of the fine nozzle to form liquid jet.
In order to further optimize the above solution, the imaging assembly 7, the imaging assembly comprises: the microscope is fixed on one side of the high-speed camera close to the polarizing dimmer.
In order to further optimize the above solution, the polarization dimmer 6 comprises two polarizers, and the polarization direction of the polarizers can be adjusted by rotating the polarizers.
A measuring method of a device for measuring micro displacement of the surface of a liquid jet flow comprises the following steps:
1) firstly, adjusting a laser light column 9 of the laser 1 to be coaxial with a microscope in the imaging assembly 7, and adjusting the imaging of the laser light column 9 to be at the center of a high-speed camera in the imaging assembly 7 so that the laser light column 9 of the laser 1 is coaxial with the microscope in the imaging assembly 7;
2) the standard slit 5 is adjusted to be coplanar with the liquid jet generating assembly 4;
3) calibrating the standard slit 5, starting the laser 1, and adjusting the distance between the imaging component 7 and the standard slit 5 to enable fourth-level dark stripe on the left side and the right side of the high-speed camera to be close to the picture boundary;
4) measuring the distance 2x between the four-level dark stripes on the left side and the right side in the step 3 according to the following formula 4,s ：
Wherein b is the width of the slit; k is the dark fringe level; l is the distance from the slit to the imaging surface; λ is the wavelength of the light wave; x is the number of k The distance between the center of the kth-level dark fringe and the center of the central zero-level fringe is shown;
acquiring horizontal gray level distribution of stripes in the photo acquired in the step 3) through image processing software, wherein the position with zero gray level is a dark stripe position; acquiring pixel abscissas with the fourth gray scale as a zero point on two sides of the central bright line through image processing software, wherein the difference between the pixel abscissas is 2y 4,s (ii) a And according to the size of a single pixel of the high-speed camera as sigma, obtaining the position x of the four-level dark fringe 4,s ＝y 4,s σ, four-level dark fringe position x formed by standard slit (5) 4,s Replacing x in the above formula k Width b of standard slit (5) s Replacing b in the formula and making k equal to 4, the equivalent distance between the plane of the standard slit (5) and the imaging plane of the imaging assembly (7) can be calculated:
in the formula b s Is a standard slit width, can be considered error-free;
5) after the calibration link is completed, the laser 1 is closed, the imaging component 7 and the laser 1 are horizontally moved to enable the liquid jet boundary to be positioned in the center of the picture, and the relative positions of the laser 1 and the imaging component 7 are kept fixed in the process; the position of the blade 3 is adjusted by using the precision displacement table 2 to enable the blade edge and the liquid jet boundary to form a slit, and the width of the slit is determined by the amplification measurement of the imaging component 7;
6) after the adjustment of the slit between the edge of the blade 3 and the liquid jet boundary is completed, the laser 1 is started, and a diffraction fringe picture is shot;
7) measuring the position x of the four-level dark stripe in the photo of step 6 4 The change of (2): firstly, acquiring the horizontal gray level distribution of the stripes in the photo in the step 6) through image processing software, wherein the position with zero gray level is the position of the dark stripe, acquiring pixel horizontal coordinates with fourth gray levels at two sides of the central bright stripe as zero points through the image processing software, and the difference between the two pixel horizontal coordinates is 2y 4 (ii) a And according to the size of a single pixel of the high-speed camera as sigma, obtaining the position x of the four-level dark fringe 4 ＝y 4 σ, and then the four-level dark fringe position x of each photo 4 Substituting the following equation to obtain the slit width b, wherein b and x in the equation 4 Both vary with respect to time as a function of time:
8) the magnification a of the slit between the edge of the blade 3 and the liquid jet boundary is obtained according to the following formula,
wherein d is a differential operator,
refers to x k And b is differentiated, and the resolution of the device is determined by the magnification factor A.
Get x 4,s 10mm, λ 532nm, calculated according to the above formula to give L469.9 mm; the numerical value is brought into the formula to obtain a value A of about 100, which indicates that the variation of the slit width between the blade and the liquid jet is amplified by about 100 times through diffraction, and further indicates that the resolution capability is improved by 100 times on the basis of the original resolution of the imaging assembly.
Since the diffracted light needs to be magnified and imaged by the imaging component 7, the slit-to-imaging plane distance L cannot be simply considered as the distance between the slit and the high-speed camera CMOS sensor. Therefore, before formal measurement, the standard slit 5 with known slit width is moved to the same plane position of the liquid jet, so that laser passes through the standard slit 5 to be diffracted, and diffraction fringes obtained by the imaging component 7 are calibrated. After calibration is completed, the precision displacement table 2 for clamping the blade 3 is adjusted to enable the knife edge and the jet boundary to form a narrow slit with small width, so that the laser light column 9 penetrates through the slit, and diffraction stripes are shot by the imaging component 7. The change of the position of a certain level of dark stripe in the diffraction stripe picture obtained by shooting is measured, and the change of the width of the slit formed by the jet flow and the knife edge can be calculated by combining the calibration information of the standard slit 5. Because the knife edge is fixed as a reference value, the variation of the slit width is the displacement of the liquid jet boundary. According to fraunhofer diffraction theory, by adjusting the distance between the knife edge and the liquid jet (i.e. the width of the slit) and the distance between the slit and the imaging plane, the displacement variation of the jet boundary can be amplified, so that the information originally higher than the optical resolution of the microscope can be measured.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. An apparatus for measuring micro-displacements of a surface of a liquid jet, comprising: the device comprises a laser (1), a precise displacement table (2), a blade (3), a liquid jet generation assembly (4), a standard slit (5), a polarization dimmer (6) and an imaging assembly (7);
the laser (1), the precise displacement table (2), the blade (3), the liquid jet generation assembly (4), the polarization dimmer (6) and the imaging assembly (7) are sequentially arranged and fixed at the top of the optical platform (8); the blade (3) and the standard slit (5) are positioned on the same plane, and the standard slit (5) is fixed at the top of the optical platform (8);
the blade (3) is fixed at the moving end of the precision displacement table (2), and the precision displacement table (2) drives the blade (3) to move in three dimensions;
the bottom of the liquid jet generating component (4) forms a liquid jet, and the slit between the blade (3) and the liquid jet is equal to the slit width of the standard slit (5).
2. A device for measuring micro-displacements of the surface of a liquid jet according to claim 1, characterized in that the axis of the laser beam (9) of said laser (1) is collinear with the axis of the imaging assembly (7).
3. The device for measuring the micro-displacement of the surface of the liquid jet is characterized in that the slit width between the blade (3) and the liquid jet is 0.05-0.1 mm, and the slit width of the standard slit (5) is 0.1 mm.
4. A device for measuring micro-displacements of a surface of a liquid jet according to claim 1, characterized in that said liquid jet generating assembly (4) comprises: the device comprises an injection pump and a fine nozzle, wherein the fine nozzle is fixed at an outlet at the bottom of the injection pump, and liquid flows out of an outlet of the fine nozzle to form liquid jet.
5. A device for measuring micro-displacements of the surface of a liquid jet according to claim 1, characterized in that said imaging assembly (7) comprises: the microscope is fixed on one side of the high-speed camera close to the polarization dimmer.
6. A device for measuring micro-displacements of the surface of a liquid jet according to claim 5, characterized in that said polarization dimmer (6) comprises two polarizers, the polarization direction of which can be adjusted by rotating said polarizers.
7. A measuring method of a device for measuring micro displacement of a liquid jet surface is characterized by comprising the following steps:
1) firstly adjusting the laser light column (9) of the laser (1) to be coaxial with the microscope in the imaging assembly (7), and adjusting the imaging of the laser light column (9) to be at the center of a high-speed camera in the imaging assembly (7) so that the laser light column (9) of the laser (1) is coaxial with the microscope in the imaging assembly (7);
2) -adjusting the standard slit (5) coplanar with the liquid jet generating assembly (4);
3) calibrating the standard slit (5), starting the laser (1), and adjusting the distance between the imaging component (7) and the standard slit (5) to enable fourth-level dark stripe on the left side and the right side of the high-speed camera to be close to the picture boundary;
4) the relationship between parameters of Fraunhofer slit diffraction is as follows:
wherein b is the slit width; k is the dark fringe level; l is the distance from the slit to the imaging surface; λ is the wavelength of light; x is a radical of a fluorine atom k The distance between the center of the kth-level dark fringe and the center of the central zero-level fringe is shown;
acquiring horizontal gray level distribution of stripes in the photo acquired in the step 3) through image processing software, wherein the position with zero gray level is a dark stripe position; acquiring pixel abscissas with the fourth gray scale as a zero point on two sides of the central bright line through image processing software, wherein the difference between the pixel abscissas is 2y 4,s (ii) a And according to the size of a single pixel of the high-speed camera as sigma, obtaining the position x of the four-level dark fringe 4,s ＝y 4,s σ, four-level dark fringe position x formed by standard slit (5) 4,s Replacing x in the above formula k Width b of standard slit (5) s Replacing b in the formula and making k equal to 4, the equivalent distance between the plane of the standard slit (5) and the imaging plane of the imaging assembly (7) can be calculated:
5) after the calibration link is completed, the laser (1) is closed, the imaging component (7) and the laser (1) are horizontally moved to enable the liquid jet boundary to be positioned in the center of a picture, and the relative positions of the laser (1) and the imaging component (7) are kept fixed in the process; the position of the blade (3) is adjusted by using the precision displacement table (2) to enable the knife edge and the liquid jet boundary to form a slit, and the width of the slit is determined by the amplification measurement of the imaging component (7);
6) after the adjustment of the slit between the edge of the blade (3) and the liquid jet boundary is completed, starting the laser (1) and shooting a diffraction fringe photo;
7) measuring the position x of the four-level dark stripes in the photo of the step 6) 4 The change of (c): firstly, acquiring the horizontal gray level distribution of the stripes in the photo in the step 6) through image processing software, wherein the position with zero gray level is the position of the dark stripe, acquiring the pixel abscissa with the fourth gray level at two sides of the central bright stripe as the zero point through the image processing software, and the difference between the two pixel abscissas is 2y 4 (ii) a And according to the size of a single pixel of the high-speed camera as sigma, obtaining the position x of the four-level dark fringe 4 ＝y 4 σ, and then put the four-level dark fringe positions of each photoX is arranged 4 Substituting the following equation to obtain the slit width b, wherein b and x in the equation 4 Both vary with respect to time as a function of time:
8) the magnification A of the slit between the edge of the blade (3) and the liquid jet boundary is obtained according to the following formula,
wherein d is a differential operator, d is a linear operator,
refers to x k And b is differentiated, and the resolution of the device is determined by the magnification factor A.
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