CN109684690A - A kind of emulated computation method obtaining laser shade, schlieren and shear interference image - Google Patents
A kind of emulated computation method obtaining laser shade, schlieren and shear interference image Download PDFInfo
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Abstract
This application provides the emulated computation methods of a kind of acquisition laser shade, schlieren and shear interference image, the primary condition of the axisymmetric index distribution in target area and light need to only be given, it can get accurate light propagation trajectories, according to the principle of this track and optical imagery, shade, schlieren and the shear interference image of simple lens imaging can be further obtained.Shade, schlieren and the shear interference image being calculated can be with experiment verifyings mutually, the index distribution of the given target area of verifying, the index distribution for examining the instruments such as shadow graph, schlieren, shearing interferometer or calculation method to obtain, analyzes the reliability and error of these instruments or calculation method.The index distribution of given target area can be further corrected on this basis, until obtaining and testing consistent calculated result, the distribution of the quantity of states such as corresponding density, concentration and temperature can be derived according further to accurate test zone index distribution at this time.
Description
Technical field
This application involves field of image processing more particularly to a kind of obtain laser shade, schlieren and shear interference image
Emulated computation method.
Background technique
In Engineering Thermophysics and fluid ambit, the measurement in temperature field and concentration field for fluid is particularly significant
's.The optical property for usually utilizing fluid, the spatial distribution of thermodynamic fluid state parameter is measured by optics display technology.
The state parameters such as temperature, pressure, concentration and the Mach number of fluid and density have a determining functional relation, and fluid
Light refractive index is the function of its density.The non-uniform refractive index field of fluid can generate disturbance to by the light of fluid, and one
As two kinds of variation can occur: (1) light, which is propagated, deviates original direction；(2) disturbance light is relative to being undisturbed light
Phase difference has occurred, the basic principle of optics display technology is exactly that stream is determined according to the deviation of the light direction of propagation or phase difference
The variations in refractive index of body, to further determine some state parameters of fluid.
Common diagnostic method has three categories:
The schlieren method and Method of Speckle Photography of refractive index first derivative are determined according to the deflection angle of light.
The shadowing method of refractive index second dervative is determined according to the deviation of light on the projection surface.
The shearing interference method of refractive index is determined according to light phase change, that is, optical path length difference.
These diagnostic methods are compared with other measuring techniques and are had many good qualities, they do not disturb the test probe in flow field,
Light is to the temperature field of fluid to be measured, concentration field and the noiseless effect of velocity field, along with light propagates very rapid, Ke Yiyong
More quick dynamic process is studied, can be got off with the graphic recording of test object with certain optics display technology, from
And determine the spatial distribution of each measurement parameter in a certain instantaneous, certain areal extent.
But above-mentioned three kinds of optical diagnostics display methods are inherently integrated forms, along the light direction of propagation by determinand
Reason amount is integrated, and is often suitable only for measuring one-dimensional field and two dimensional field, and in these, the change of not refractive index is propagated along light
Change, just has unexpected discontinuous variation when only light passes in and out test section, for three dimensional field, can only generally measure along light distance
Average value can be converted by certain, to acquire refractive index in the distribution in space unless under certain test condition.
Test shade, schlieren, shear interference technology are widely used in the qualitative and quantitative display in flow field, these three figures
As being all that light passes through smooth as a result, the Strength Changes of lucky Shandong are phase change and the cheap function of angle.Shadowing method record
Be deviation alternate position spike, the variation (i.e. the second dervative of refractive index n) of the thing refractive index gradient of reflection, shadowing systems are frequently used for
The place of density gradient variation very greatly, is also applied for big scale, and relatively material requirements is lower, and cost is minimum, but usually only
Refractive index/Density Distribution in energy qualitative analysis test zone, is usually used in shock wave position in the display of flow field structure, especially flow field
The detection set.Schlieren method record is deviation differential seat angle, and reflection is that (i.e. the first derivative of refractive index becomes for the gradient of refractive index
Change), but common imaging plane can not quantitative measurement illumination size, it is general to be only used to judging test zone first derivative just
Negative situation of change.Shearing interference method record is that phase of light wave is poor, and reflection is refractive index itself, and shear interference system is usually right
Environmental vibration is more sensitive, and installation is complicated, can provide quantitative information, but higher cost, and can only generally measure smaller
Object.
In short, the requirement of shadowing method and schlieren method for instrument is lower, in shade and schlieren system, Strength Changes are (bright
And dark areas) be usually used in being embodied with the flow field characteristic of larger refractive index gradient, such as shock wave, shear layer and expanding layer, it is applicable
Range is wider, but can only generally make qualitative analysis (changing rule of observation density field), cannot provide quantitative data.And it shears
Though interferometry can provide the quantitative result of refractive index and density according to the difference of light phase change or optical path length, calculated
The influence of method error and experimental error usually can not also determine whether the spatial refractive index distribution of the test zone of acquisition is sufficient
It is enough accurate.
Summary of the invention
To solve the above-mentioned problems, this application provides the imitative of a kind of acquisition laser shade, schlieren and shear interference image
True calculation method.
This application provides the emulated computation method of a kind of acquisition laser shade, schlieren and shear interference image, the sides
Method includes:
Obtain the axisymmetric index distribution of tested region；
According to the axisymmetric index distribution index distribution of the tested region, changed using Fourth order Runge-Kutta
The light propagation trajectories of laser are calculated in generation；
Laser shade, schlieren and shear interference is calculated according to preset algorithm according to the propagation trajectories of the laser
Image.
From the above technical scheme, this application provides a kind of acquisition laser shade, schlieren and shear interference images
Emulated computation method, it need to only give primary condition (number, incidence of the axisymmetric index distribution in target area and light
Angle, initial coordinate) it can be obtained accurate light propagation trajectories, it, can be further according to the principle of this track and optical imagery
Ground obtains shade, schlieren and the shear interference image of simple lens imaging.Shade, schlieren and the shear interference image being calculated can
To be verified mutually with experiment, the index distribution of given target area is verified, shadow graph, schlieren, shearing interferometer are examined
The index distribution that equal instruments or calculation method obtain, analyzes the reliability and error of these instruments or calculation method.Into
The index distribution that can correct to one step given target area on this basis, until obtaining and testing consistent calculating
As a result, can be derived at this time according further to accurate test zone index distribution corresponding density, concentration and
The distribution of the quantity of states such as temperature.It is also possible to which shade, schlieren imaging technology is cooperated to obtain more reasonable axial symmetry
Index distribution.The requirement of shadowing method and schlieren method for instrument is lower, and the scope of application is also wider, in unreliable instrument analysis
Occasion, can use the method and simple instrument obtain the index distribution of accurate target area.
Detailed description of the invention
In order to illustrate more clearly of the technical solution of the application, letter will be made to attached drawing needed in the embodiment below
Singly introduce, it should be apparent that, for those of ordinary skills, without any creative labor,
It is also possible to obtain other drawings based on these drawings.
Fig. 1 is a kind of emulated computation method for obtaining laser shade, schlieren and shear interference image provided by the present application
Flow chart；
Fig. 2 is the refraction track schematic diagram of exploring laser light beam；
Fig. 3 is the flow chart of an embodiment of step 13；
The schematic diagram of computational shadowgraph image when Fig. 4 (a) is no lens focus；
Fig. 4 (b) is the schematic diagram that schlieren image is calculated when simple lens is imaged；
Fig. 4 (c) is the schematic diagram of computational shadowgraph and shear interference image when simple lens is imaged；
Fig. 5 is the flow chart of another embodiment of step 13；
Fig. 6 is the flow chart of another embodiment of step 13；
Fig. 7 is the schematic diagram for the refraction that the law of refraction calculates light.
Specific embodiment
Referring to Fig. 1, this application provides the simulation calculation sides of a kind of acquisition laser shade, schlieren and shear interference image
Method includes the following steps:
Step 11: obtaining the axisymmetric index distribution of tested region.
If what is obtained is the axisymmetric Density Distribution of tested region, in accordance with the following steps by axisymmetric density point
Cloth is converted to axisymmetric index distribution:
(1) the axisymmetric Density Distribution of the tested region is obtained.
(2) according to the axisymmetric Density Distribution of the tested region, following Gladstone-Dell's formula, meter are utilized
Calculation obtains corresponding axisymmetric index distribution；
Wherein, ρ (r) is axisymmetric Density Distribution, and n (r) is corresponding index distribution, and K is lattice drawing
Moral stone-Dell's constant.
For the index distribution of aqueous medium, calculated using following formula,
N (r)=1.332+0.322 [ρ (r)-ρ0]；
Wherein, ρ0It is hydrostatic density, 1.332 be the refractive index of hydrostatic.
If what is obtained is the axisymmetric fluid temperature (F.T.) of tested region, in accordance with the following steps by axisymmetric density point
Cloth is converted to axisymmetric index distribution:
(1) the axisymmetric fluid temperature (F.T.) of the tested region is obtained.
(2) according to the axisymmetric fluid temperature (F.T.) of the tested region, corresponding axisymmetric Density Distribution is calculated.
For air-flow, if pressure in the gas flow may be considered constant, and The Ideal-Gas Equation is set up, then
Have
Wherein, P is pressure, and T is temperature, and M is molecular weight gas, and R is gas constant.For other fluids temperature with it is close
The relationship of degree can consult relevant experimental fit curve.
Likewise, it is known that the concentration distribution of test zone, can also obtain the folding of mixed gas with the G-D formula of mixed gas
Penetrate rate nc, i.e.,
Wherein, KiFor the G-D constant of each component, ρiFor the density of each component.
It is worth noting that, temperature, density, the concentration distribution of above-mentioned fluid need to be axis pair for the method for the present invention
Claim, if it is determined that it is correct when given index distribution, it can derive the fluid to corresponding state parameter in turn
Distribution.
(3) according to the axisymmetric Density Distribution, corresponding axisymmetric index distribution is calculated.
Step 12: according to the axisymmetric index distribution index distribution of the tested region, utilizing quadravalence Long Geku
The light propagation trajectories of laser are calculated in tower method iteration.
Specifically, referring to fig. 2, since laser beam incidence point, using following formula, radius step-length and angle is calculated
The absolute value of the ratio of step-length is spent,
Wherein, α0It is the initial of every incident ray
Deflection angle, n0For the initial index of refraction at plane of incidence, r0,For the initial position of every light.
In addition, theoreticallyMinimum value be 0, corresponding dr=0, when r value minimum, but numerical value
There are error, this minimum values to be negative for calculating.Light is along approximate angular direction and propagates at this time,Value reaches the negative value moment and thinks that the direction of propagation of light is constant, does not reflect, takes fixed x
Direction step-length dx calculates the direction y step-length dy, untilValue be greater than 0.
The numerical value perseverance of right side equation is positive, but r can first reduce and increase afterwards in the communication process of light, and there are positive and negative by dr
Transformation, but θ is reducing always, and d θ perseverance is negative, therefore a decision content sl=[r (i)-r (i-1)]/[θ (i)-θ can be set
(i-1)], wherein sl is decision content, and r is radius, and θ is angle；If it is determined that value is greater than or equal to zero, then radius step-length dr takes
Negative value；If it is determined that value is less than zero, then radius step-length dr takes positive value.
If the absolute value is greater than preset upper limit threshold, dr is taken into preset radius step-length, using above-mentioned formula,
Angle step d θ is calculated, and determines next point.
If the absolute value is less than preset lower threshold, d θ takes preset angle step, utilizes above-mentioned formula, meter
Calculation obtains radius step-length dr, and determines next point.
If the absolute value is less than or equal to the preset upper limit threshold, it is greater than or equal to the preset lower limit threshold
Value, then d θ takes any angle step-length or dr to take any radius step-length.
Step 13: according to the propagation trajectories of the laser, according to preset algorithm, be calculated laser shade, schlieren and
Shear interference image.
From the above technical scheme, this application provides a kind of acquisition laser shade, schlieren and shear interference images
Emulated computation method, it need to only give primary condition (number, incidence of the axisymmetric index distribution in target area and light
Angle, initial coordinate) it can be obtained accurate light propagation trajectories, it, can be further according to the principle of this track and optical imagery
Ground obtains shade, schlieren and the shear interference image of simple lens imaging.Shade, schlieren and the shear interference image being calculated can
To be verified mutually with experiment, the index distribution of given target area is verified, shadow graph, schlieren, shearing interferometer are examined
The index distribution that equal instruments or calculation method obtain, analyzes the reliability and error of these instruments or calculation method.Into
The index distribution that can correct to one step given target area on this basis, until obtaining and testing consistent calculating
As a result, can be derived at this time according further to accurate test zone index distribution corresponding density, concentration and
The distribution of the quantity of states such as temperature.It is also possible to which shade, schlieren imaging technology is cooperated to obtain more reasonable axial symmetry
Index distribution.The requirement of shadowing method and schlieren method for instrument is lower, and the scope of application is also wider, in unreliable instrument analysis
Occasion, can use the method and simple instrument obtain the index distribution of accurate target area.
Referring to Fig. 3, in another embodiment of the application, above-mentioned steps 13 include the following steps:
Step 31: preset section is marked off on as plane.
Step 32: according to the light propagation trajectories of the laser, calculating the light reverse extending outside refractive index change regions
The intersection point of line and object plane.
Step 33: according to the intersection point, being calculated as corresponding light coordinate in plane.
Step 34: if the corresponding light of the light coordinate is not received by convex lens, in the pre-set interval as plane
The light is not counted inside；If the corresponding light of the light coordinate is received by convex lens, in the pre-set interval as plane
The interior statistics light.
Step 35: according to the light in the pre-set interval as plane of statistics, obtaining laser shadow image.
It is axisymmetric according to the schematic diagram of laser refraction propagation trajectories computational shadowgraph image when Fig. 4 (a) is no lens focus
Index distribution zone radius is Rn, coordinate system is established with a certain sagittal plane.At this point, the refraction in refractive index change regions
Rate is unevenly distributed, and deflects parallel rays, and the even image of brightness unevenness can be presented on the screen, and what it reflected is disturbed light
The displacement of the lines of line.From figure it can be found that since index distribution is, refractive index inhomogeneity related with radial distance r
It is all existing for the direction x, the direction y.But refractive index change regions are practical smaller, spread out of the light of refractive index change regions
For line in the direction y there is no being significantly displaced, the angle of light and x-axis at this time is denoted as α, and light is along straightline propagation later, it
Reverse extending line and y-axis (x=0 plane) the actually corresponding parallel rays of intersection point P in no refraction with y-axis
Intersection point it is very close, therefore can be assumed that a certain extent incident ray along straightline propagation reach y-axis when due to refractive index
Suddenly change deflect α angle suddenly, continue later along straightline propagation.The even image of the brightness unevenness that can be presented on screen be by
Caused by the angle of deflection of incident ray is different, but if being the feelings for having lens by focus incident light to object distance x=0 plane
Condition, then as the variation for not having light and shade in plane usually can not travel to unless the deflection angle of light is excessive as in plane.
In general, the light by refractive index change regions is not directional light, angle of deflection is the function of y,It can also be found out according to the arc tangent of slope after light propagation trajectories outflow refractive index change regions.From light
From the point of view of strong, the light at x=0 plane be approximately it is equally distributed, due to having deflected different angles, far from refractive index point
On the viewing screen in cloth region, the light intensity in x=0 plane in the region Δ y is mapped to Δ yDThe light intensity in region is changed.If
Original light intensity is IT, then light intensity on the screen be
ZCDIt is distance of the x=0 plane to screen, then the contrast R on screenDFor
As can be seen from the above formula that shadowing method is only able to display the non-uniform refractive index field of second dervative of refractive index, such as
The refractive index first derivative of fruit index distribution region in the y-direction is constant, then the angle of deflection of all light is all identical
, display screen is evenly illuminated；If the second dervative of refractive index is equally distributed in refractive index change regions,
Viewing screen is also evenly illuminated, and only intensity increases or decreases.
Referring to Fig. 5, in another embodiment of the application, above-mentioned steps 13 further include following steps:
Step 51: preset section is marked off on as plane.
Step 52: according to the light propagation trajectories of the laser, calculating the light reverse extending outside refractive index change regions
The intersection point of line and object plane.
Step 53: according to the intersection point, being calculated as corresponding light coordinate in plane.
Step 54: if the corresponding light of the light coordinate is received by convex lens, and the light is inclined upwards through the edge of a knife
Turn, then counts the light in the pre-set interval as plane.
Step 55: according to the light in the pre-set interval as plane of statistics, obtaining laser schlieren image.
Fig. 4 (b) is the schematic diagram for calculating schlieren image when simple lens imaging according to laser refraction propagation trajectories.Schlieren method
Basic principle is to cut light source picture with the edge of a knife, light is disturbed by flow field the distribution for being changed into light intensity in record plane.Due to
The light issued from light source deflects by the uneven Qu Shihui of fluid density, and the degree of edge of a knife cutting light source picture will depend on
The size of refractive index first derivative in fluid.The edge of a knife is placed on the right side point of intersection of lens L, if propagating out variations in refractive index area
The light in domain up deflects, then light can cross the edge of a knife and reach as in plane, showing bright region；If propagating out refractive index
The light of region of variation deflects down, then light can be blocked by the edge of a knife, and corresponding region can show dark area on as plane
Domain.In addition, obtained schlieren image be it is asymmetric, for axisymmetric index distribution, when the deflection of light is about x-axis pair
Claim, then two symmetrical light there must be one to be blocked up and down, and the variation that schlieren method can relatively accurately distinguish refractive index becomes
Gesture.
Referring to Fig. 6, in the another embodiment of the application, above-mentioned steps 13 further include following steps:
Step 61: obtaining every light using ray tracing according to the light of the initial uniform distribution on source plane and exist
As the respective coordinates y in planeiWith light path li。
Step 62: according to the coordinate yiWith light path li, using difference functions, obtain function of the light path about picpointed coordinate y
l1(y)=interp1 ([yi],[li], y) and translation after iconal l2(y)=l (y-yshear)=interp1 ([yi],
[li],y-yshear), yshear is the relative displacement of the direction y.
Step 63: according to the light path about the iconal after the function of picpointed coordinate y and translation, obtaining light intensity amplitude
Vector function A (y).
Step 64: according to coordinate yi, using following formula, calculate as the shear interference image in plane；
Wherein, l (y-ysheay) be translation after iconal, l (y) be function of the light path about picpointed coordinate y, A is light
Strong amplitude, yshear are the relative displacement of the direction y.
According to the principle of laser refraction propagation trajectories computational shadowgraph and shear interference image when Fig. 4 (c) is simple lens imaging
Figure.Object distance, image distance meet convex lens real image imaging formula:
F is focal length of convex lens, and u, v are image distance and object distance.As previously described, light after light outflow refractive index change regions
Along straightline propagation, its reverse extending line parallel rays corresponding with the intersection point P of y-axis (x=0 plane) is without refraction situation
Lower very close with the intersection point of y-axis, light is being equivalent to P point on object plane as the point in plane, that is to say, that as plane receives
To light be a light that equivalent P point issues, only this light has certain deflection relative to incident parallel rays,
It is only being propagated out outside lens by the light of deviation, Shi Caihui is not assembled by convex lens and goes out that dark area is presented on as plane
Domain.Therefore, what the shadow image of simple lens imaging can reflect is the biggish region of refractive index in test zone.
The light path of convex lens, the optical path of each that object distance a little issues to picture point is all equal (undisturbed), then x=
The equivalent optical path that the light that P1 point issues in 0 plane (object plane) passes through on P1C1D1E1 and two optical paths of P1FE1, P1, P2
The coordinate of point is respectively (0, y1), (0, y2).In addition, object point P1 on object plane is to the light path and object as the picture point E1 in plane
The light path of point P2 to picture point E2 are also equal, are denoted as Limage, then have
Wherein, ntFor convex lens refractive index.By taking light 1 as an example, the total optical path of A1-E1 are as follows:
Wherein Limage is constant, remaining item is the function of picture point E ordinate y, therefore L1 can be write as:
L1=l (y)+C；
Light reaches the phase as E1 point in plane are as follows:
If adjustment shear interference optical path makes two beam object lights have relative displacement yshear in the direction y on as plane, with it
In a branch of object light be with reference to establishing coordinate plane, expression formula of another beam light phase distribution on this coordinate plane is
Electromagnetic wave electric field component is indicated with the real part of the complex exponential of e the following on source plane:
As electric field component is expressed as in plane
Wherein, A1 is electric field component amplitude of the light 1 on as plane at E1 point, and A2 is that shearing light beam gets to E1 point light
Electric field component amplitude.Electric field component after the superimposed real part of electric field component is interfered, enables k=2 π/λ, then has
Light intensity or electric field component amplitude square are
When reaching equal as the electromagnetic wave electric field component amplitude in plane,
Light intensity or electric field component amplitude square are
Amplitude not etc. there are the case where are as follows: the different region of refractive index is different to the absorbability of light or deflection of light goes out
It is not reached when lens as plane (A=0 at this time).
As can be seen from the above technical solutions, it is to obtain axisymmetric index distribution first, can be obtained from experiment
A kind of distribution is assumed in shade, schlieren and shear interference analysis, is also possible to according to shadow graph, schlieren, interferometer or one
The index distribution that a little calculation methods obtain, is updated in formula as variable.
Followed by need to give the initial value (coordinate, incidence angle) of uniform laser light incident light, give specific calculate
Step-length, the regional scope of setup algorithm are iterated using quadravalence Long Gekutafa, can be obtained the propagation of every incident ray
Track.It obtains the deflection direction of the intercept y0, light that spread out of the light of test zone in y-axis, reach the ordinate at convex lens
Y1, corresponding light path l, light are as the respective coordinates y2 and corresponding light intensity amplitude A in plane.
It is finally the imaging section divided as in plane, the optical imagery according to laser shade, schlieren and shear interference is former
Reason calculates corresponding optical imagery.Calculating for shade and schlieren image, first judges whether light can be received by lens mirror,
The light not being received, as the section in plane does not count this light corresponding to point of the reverse extending line on object plane
Line, the light being received are included in as corresponding to section in plane for shadow image, also to judge for schlieren image
The deflection direction of light, judges whether light can be blocked by the edge of a knife, and other processing methods are identical as schlieren.For shear interference
The calculating of image, by interpolating function obtain as in plane about the iconal l (y) of coordinate y and light intensity amplitude vector function A
(y), corresponding coordinate vector [yj] is then taken, according to the light intensity calculation formula of shear interference, can be obtained as cutting in plane
Cut interference image.
Illustrate the accuracy of the bright method of we in conjunction with the schematic diagram that Fig. 7 law of refraction calculates anaclasis.It is assumed that one
Radius is the axisymmetric Density Distribution region of 2cm, and refractive index perseverance is 1.5 in this region, the area where Rn in corresponding diagram 4
Domain, the refractive index outside this region is 1.An incident horizontal light is put in coordinate A (- 4,1), in the regional edge for being Rn with radius
Raw refraction occurs for B point in boundary, according to the law of refraction for being suitable for uniform isotropic medium
The coordinate of light and the intersection point C of y-axis use quadravalence dragon lattice using above-mentioned calculation method for (0,0.6780839)
Ku Tafa iteration, when angle step takes 0.0001, the intersection point of the light and y-axis that are calculated is (0,0.6780938), numerical value
Error is calculated less than 0.01%, as long as accordingly, it is believed that given index distribution region is accurately, to be calculated
Shade and schlieren image be exactly it is accurate, thinking laser beam reach as the identical feelings of the amplitude of the electric field component in plane
Under condition, the image of the shear interference of calculating is also accurate.
It is of the present invention this based on the emulation of spatial refractive index distributed acquisition laser shade, schlieren and interference image
Calculation method use is very convenient, need to only give the axisymmetric index distribution in target area and light primary condition (number,
Incidence angle, initial coordinate) it can be obtained accurate light propagation trajectories, according to the principle of this track and optical imagery, Ke Yijin
Shade, schlieren and the shear interference image of simple lens imaging are obtained to one step, is obtained certainly according to other optical imaging concepts
Diagnostic image, the method are also that can calculate.
From the above technical scheme, this application provides a kind of acquisition laser shade, schlieren and shear interference images
Emulated computation method, it need to only give primary condition (number, incidence of the axisymmetric index distribution in target area and light
Angle, initial coordinate) it can be obtained accurate light propagation trajectories, it, can be further according to the principle of this track and optical imagery
Ground obtains shade, schlieren and the shear interference image of simple lens imaging.Shade, schlieren and the shear interference image being calculated can
To be verified mutually with experiment, the index distribution of given target area is verified, shadow graph, schlieren, shearing interferometer are examined
The index distribution that equal instruments or calculation method obtain, analyzes the reliability and error of these instruments or calculation method.Into
The index distribution that can correct to one step given target area on this basis, until obtaining and testing consistent calculating
As a result, can be derived at this time according further to accurate test zone index distribution corresponding density, concentration and
The distribution of the quantity of states such as temperature.It is also possible to which shade, schlieren imaging technology is cooperated to obtain more reasonable axial symmetry
Index distribution.The requirement of shadowing method and schlieren method for instrument is lower, and the scope of application is also wider, in unreliable instrument analysis
Occasion, can use the method and simple instrument obtain the index distribution of accurate target area.
Claims (8)
1. a kind of emulated computation method for obtaining laser shade, schlieren and shear interference image, which is characterized in that the method packet
It includes:
Obtain the axisymmetric index distribution of tested region；
According to the axisymmetric index distribution index distribution of the tested region, Fourth order Runge-Kutta iteration, meter are utilized
Calculation obtains the light propagation trajectories of laser；
Laser shade, schlieren and lateral shear interferograms are calculated according to preset algorithm according to the propagation trajectories of the laser
Picture.
2. the method as described in claim 1, which is characterized in that the axisymmetric index distribution packet for obtaining tested region
It includes:
Obtain the axisymmetric Density Distribution of the tested region；
According to the axisymmetric Density Distribution of the tested region, using following Gladstone-Dell's formula, it is calculated pair
The axisymmetric index distribution answered；
Wherein, ρ (r) is axisymmetric Density Distribution, and n (r) is corresponding index distribution, and K is Gladders
Logical-Dell's constant.
3. the method as described in claim 1, which is characterized in that the axisymmetric index distribution packet for obtaining tested region
It includes:
Obtain the axisymmetric fluid temperature (F.T.) of the tested region；
According to the axisymmetric fluid temperature (F.T.) of the tested region, corresponding axisymmetric Density Distribution is calculated；
According to the axisymmetric Density Distribution, corresponding axisymmetric index distribution is calculated.
4. the method as described in claim 1, which is characterized in that the axisymmetric refractive index according to the tested region point
Cloth index distribution, using Fourth order Runge-Kutta iteration, the light propagation trajectories that laser is calculated include:
Since laser beam incidence point, using following formula, the absolute of the ratio of radius step-length and angle step is calculated
Value,
Wherein, α0It is the initial deflection of every incident ray
Angle, n0For the initial index of refraction at plane of incidence, r0,For the initial position of every light；
If the absolute value is greater than preset upper limit threshold, dr is taken into preset radius step-length, using above-mentioned formula, is calculated
Angle step d θ is obtained, and determines next point；
If the absolute value is less than preset lower threshold, d θ takes preset angle step, using above-mentioned formula, calculates
To radius step-length dr, and determine next point；
If the absolute value is less than or equal to the preset upper limit threshold, it is greater than or equal to the preset lower threshold,
Then d θ takes any angle step-length or dr to take any radius step-length.
5. the method as described in claim 1, which is characterized in that the axisymmetric refractive index according to the tested region point
The light propagation trajectories of laser are calculated using Fourth order Runge-Kutta iteration in cloth index distribution further include:
Sl=[r (i)-r (i-1)]/[θ (i)-θ (i-1)], wherein sl is decision content, and r is radius, and θ is angle；
If it is determined that value is greater than or equal to zero, then radius step-length dr takes negative value；
If it is determined that value is less than zero, then radius step-length dr takes positive value.
6. the method as described in claim 1, which is characterized in that the propagation trajectories according to the laser, according to preset
Algorithm, laser shadow image, which is calculated, includes:
Preset section is marked off on as plane；
According to the light propagation trajectories of the laser, light reverse extending line outside refractive index change regions and object plane are calculated
Intersection point；
According to the intersection point, it is calculated as corresponding light coordinate in plane；
If the corresponding light of the light coordinate is not received by convex lens, do not count described in the pre-set interval as plane
Light；If the corresponding light of the light coordinate is received by convex lens, the light is counted in the pre-set interval as plane
Line；
According to the light in the pre-set interval as plane of statistics, laser shadow image is obtained.
7. the method as described in claim 1, which is characterized in that the propagation trajectories according to the laser, according to preset
Algorithm, laser schlieren image, which is calculated, includes:
Preset section is marked off on as plane；
According to the light propagation trajectories of the laser, light reverse extending line outside refractive index change regions and object plane are calculated
Intersection point；
According to the intersection point, it is calculated as corresponding light coordinate in plane；
If the corresponding light of the light coordinate is received by convex lens, and the light is upward deflected through the edge of a knife, then as flat
The statistics light in the pre-set interval in face；According to the light in the pre-set interval as plane of statistics, laser schlieren is obtained
Image.
8. the method as described in claim 1, which is characterized in that the propagation trajectories according to the laser, according to preset
Algorithm, shear interference image, which is calculated, includes:
Every light is obtained on as plane using ray tracing according to the light of the initial uniform distribution on source plane
Respective coordinates yiWith light path li；
According to the coordinate yiWith light path li, using difference functions, obtain function l of the light path about picpointed coordinate y1(y)=
interp1([yi],[li], y) and translation after iconal l2(y)=l (y-yshear)=interp1 ([yi],[li],y-
yshear), yshear is the relative displacement of the direction y；
According to the light path about the iconal after the function of picpointed coordinate y and translation, light intensity amplitude vector function A is obtained
(y)；
According to coordinate yi, using following formula, calculate as the shear interference image in plane；
Wherein, l (y-ysheay) be translation after iconal, l (y) be function of the light path about picpointed coordinate y, A be light intensity width
Value, yshear are the relative displacement of the direction y.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111238486A (en) * | 2020-03-12 | 2020-06-05 | 北京三快在线科技有限公司 | Navigation method and device for unmanned equipment, storage medium and unmanned equipment |
| CN113324727A (en) * | 2019-07-16 | 2021-08-31 | 中国人民解放军空军工程大学 | Schlieren image processing method for compressed corner supersonic flow field structure |
| CN114186330A (en) * | 2021-11-04 | 2022-03-15 | 北京机电工程研究所 | Shaft structure temperature estimation method under high-speed flow field environment |
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2018
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113324727A (en) * | 2019-07-16 | 2021-08-31 | 中国人民解放军空军工程大学 | Schlieren image processing method for compressed corner supersonic flow field structure |
| CN113324727B (en) * | 2019-07-16 | 2023-05-05 | 中国人民解放军空军工程大学 | Schlieren image processing method for compressed corner supersonic flow field structure |
| CN111238486A (en) * | 2020-03-12 | 2020-06-05 | 北京三快在线科技有限公司 | Navigation method and device for unmanned equipment, storage medium and unmanned equipment |
| CN111238486B (en) * | 2020-03-12 | 2021-11-19 | 北京三快在线科技有限公司 | Navigation method and device for unmanned equipment, storage medium and unmanned equipment |
| CN114186330A (en) * | 2021-11-04 | 2022-03-15 | 北京机电工程研究所 | Shaft structure temperature estimation method under high-speed flow field environment |
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