SU999808A1 - Method of measuring spatial distribution of object internal heterogeneity - Google Patents

Method of measuring spatial distribution of object internal heterogeneity Download PDF

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Publication number
SU999808A1
SU999808A1 SU813243633A SU3243633A SU999808A1 SU 999808 A1 SU999808 A1 SU 999808A1 SU 813243633 A SU813243633 A SU 813243633A SU 3243633 A SU3243633 A SU 3243633A SU 999808 A1 SU999808 A1 SU 999808A1
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SU
USSR - Soviet Union
Prior art keywords
object
radiation
dimensional
direction
axis
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SU813243633A
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Russian (ru)
Inventor
Г.Н. Вишняков
Г.Г. Левин
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Предприятие П/Я В-8584
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Priority to SU813243633A priority Critical patent/SU999808A1/en
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Publication of SU999808A1 publication Critical patent/SU999808A1/en

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Abstract

THE METHOD OF MEASURING THE VENTAL DISTRIBUTION SPACE OF INTERNAL INHOMOGENITIES the radiation is uniformly transformed in the direction of the axis perpendicular to the axis of the one-dimensional beam into a two-dimensional one, the radiation is rotated along the direction of sounding, and all the converted flows are spatially combined, differing This is because, in order to measure in real time, the spatially combined streams are multiplied by the recorder with a contrast ratio, where N is the number of angles of sounding. f (pcos (f} f -i-f-fln fj) .l

Description

This invention relates to holographic interferometry. A known method for measuring the spatial distribution of the internal inhomogeneities of the phase object 1 is that, producing a multi-angle sensing of the object by laser radiation, the interferograms of the object are recorded for each direction of sounding and the measured value is determined by the deviation of the interference fringes. The disadvantage of this method is that it is impossible to obtain the desired spatial distribution of inhomogeneities in real time, because it takes time to enter into the computer the measured by the deflection of interference fringes, data on the change in the optical path length inside the object, calculate on the computer, output and display the resulting response . The closest to the described invention in terms of technical importance is a method for measuring the spatial distribution of internal inhomogeneities of an object 2, which consists in producing a multi-view sounding of a measured object with a flat one-dimensional beam and passing through it, for each direction of sounding the transmitted radiation is uniformly transformed in the direction of the axis, perpendicular to the axis of a single beam, into a two-dimensional one, the radiation is rotated along the direction of the probing. fluxes spatially combined. This method is used in X-ray technology to measure the distribution of the X-ray attenuation coefficient in cross sections of medical and biological objects (transverse tomography). The disadvantage of this method is that it cannot measure the spatial distribution of the refractive index of an object, since In the study of objects with a variable refractive index, the amplitude of the probe radiation does not change, but the phase front of the transmitted radiation modulates. The aim of the invention is to measure the spatial distribution of the refractive index of objects in real time. 8 This is achieved by implementing the method for measuring the spatial distribution of internal inhomogeneities of an object, which consists in producing a multi-angle sounding of an object to be measured with a flat one-dimensional penetrating radiation beam, for each direction of sounding the transmitted radiation is uniformly transformed in the axis perpendicular to the axis of the one-dimensional beam into a two-dimensional one, the radiation is rotated along the direction of sounding, and all transformed streams spatially combine, rostranstvenno combined streams are multiplied with a contrast ratio registrar where N - number of angles probe. Figure 1 shows the curvature of the phase front depending on the direction of the refluxed light flux; in Fig.2,3-diagram of the device that implements the described method, top view and side. In the described method, the measured object is illuminated with flat one-dimensional light beams (light blades) simultaneously from many directions, i.e. perform multi-angle (N-angle) sensing of the object. All light knives should spread in the same plane / for example in the plane (X, y), where the coordinate system (x, y, z) is attached to the object (see Fig. 1a). The intersection of the propagation planes of one-dimensional light beams highlights the cross section of the object under study, in which using this method it is possible to measure the distribution of the refractive index in real time. A pro-A lighted object from the side under different angles can be obtained in real time, for example, an interferogram of the cross section of the object, which will simultaneously be a map of lines of equal values of the refractive index in this section. By moving the plane of propagation of the light blades along the Z axis, one can measure the three-dimensional spatial distribution of object inhomogeneities. Consider the sequence of operations performed in a single illumination channel, directed, for example, at an angle Vj, to the axis X, (see Fig. 1a). A flat one-dimensional laser beam of amplitude AO, passing through the object, will look like A e This is schematically reflected in Fig. 1a by a curvature of the phase front. The p-axis is perpendicular to the direction of propagation. The integral phase shift f (P) is associated with the refractive index i (x, -j) in this final section (x, y) by the Radon transform which in the linear approximation can be written as) -X-Poll «M (P-cos4) 53xd where L is the probe wavelength; PQ is the radius of the circle, outside of which (x, the radiation passing through the object g gnlP is uniformly stretched (spread) in the direction of the axis parallel to the Z axis (see Fig. 16), i.e. it is transformed into a two-dimensional flow described by the expression vriC | ,) where Ф (, 1Р, Фг, (Р. That is, along the P axis this field is described by the function (Р) а along the CJ axis, it is constant. This operation can be performed, for example, using two cylindrical lenses, forming which are parallel to the P axis. The two-dimensional luminous flux thus transformed, turning the U-th axis, illuminates around this angle by l 1,2, ... N (cm, fig, IB), i.e., transition 1F {{P, r1 d t from FIELD e n 1 to the light field, which is described in coordinates (P, Yag) by the following expression gi JPcosV, n5inVn) operation can be performed using a Dove prism or a system of several mirrors.All the described operations are carried out simultaneously in each of the N channels (angles), after which all the converted light streams.) Spatially combine in the plane of the recorder, t, e. a sum of light fields is formed. ) HC1 "e - -a P 1-where (; -" 1 p - UG-ol between the direction of radiation of the given n-th channel on the recorder and the normal to the plane of the recorder R4 L - probing radiation wavelength, complex values, t ..,., 2, ... N. If the recorder has a contrast ratio of -2N, then the amplitude transmission of the recorder after exposure to the light field (2) and photo processing will be 2N / NN Е1а .laj / NN К-1 2ll "| 2.Z5I "(%. G1 NJ N:" fe | .. (, where the expression in the round brackets is already valid. In detail (3) can be rewritten in the form: -i I - nd "-sh-oh ,,. D ".....";). A (cp .. ";)" ( 4) Thus, when the recorder is illuminated, several light fields propagating at different angles to the recorder normal are restored. We are interested in a field of the form: oi "2 --- N-1" "-NK) () and propagates at an angle y jjf -cL to the registrar normal.This term is formed as follows: when elevating to the Nth power, i.e. multiplying N equal expressions written in square brackets in (4), the 1st term is taken from the 1st factor, equal to N, from the 2nd item i of the 3rd c2, etc. from the N-ro factor, the term in (4) the members involved in the formation of the term (5), underline. If the N-Y channel is chosen as the reference one, i.e. with a flat wavefront, a cad lam at the recorder at an angle of 6 -O, then (5) can be rewritten as: i Nfl “Nn% P ° V sinVJ., - oi, ci gh H-1 - .. a {P4) + about where 0 (P, L-11f (Pc0Un - I ,. (t) a ti. Determines the propagation angle I, the travel of the wave field (6). It can be seen that with an appropriate selection of dn one can achieve so that the field (6) does not overlap with the rest of the recovered fields. The function Q (PI with (,) is the desired function f (P,) |. describes the spatial distribution of the optical inhomogeneities of the phase object, somewhat distorted (blurred) by the convolution with function () i.e. Q ( P. (P. I) ® | L --- IP + cj, x) is a two-dimensional convolution icon. However, for low-frequency functions, f (Xii), which are usually examined with interferometry with a small number of transmission angles, this smoothes can be neglected. Then (6) can be written in the form i | f (P. To visualize the obtained phase wave front, already containing the desired distribution f (P | Q,), you can, for example, make a 2nd exposure the recorder, but without the object (as in the method of 2 exposures of holographic interferometry). Then, in the direction towards the normal of the recorder, the field will be restored, whose intensity is 2 G 27GR N 1 D (P, c h2Nl co5-f (. (10) From expression (10), it follows that the information on the spatial distribution of the refractive index in the cross section of the object, it is enclosed in the form of a system of interference fringes, which is simultaneously a map of lines of equal values of the refractive index, and when moving from one line to another, the value of the refractive index changes by the amount of The 86 wavefront fronts obtained from different angles, necessary for summing the phase incursions Φ, can also be accomplished by repeatedly passing the same wavefront through the object successively at different angles of transmission for coaxial phase objects (i.e. along the Z axis the refractive index of the type of fiberglass) it is possible to eliminate the operation of uniformly stretching a one-dimensional flow into a two-dimensional one in the direction of the axis 2 and to carry out the probing of the object by a two-dimensional flat light beam. Currently, there are recorders with a sufficiently large contrast ratio, as well as various types of manufacturers that increase. Note that recorders with large -v are required for multi-view schemes with a large number of light channels. It is technically difficult to implement such schemes. Therefore, in practice, it is usually limited to three -., Four - view schemes, for which more common recorders with T / 6-10 can be used. Diagram of the device that implements the described method is presented in figure 2. For definiteness, consider the three-view scheme. The device contains a laser 1, a beam splitter 2, a system of two cylindrical lenses 3, a beam splitter-multiplier 4, creating the desired number of directions for sounding mirrors 5,6,7 and 8 object 9, a system of cylindrical lenses 10, Dove prism 11, recorder 12, mirror 13 extender 14 bundles. The light radiation from laser 1, falling on the beam-splitting plate 2, is divided into two parts, one of which passes through the system of forming the reference channel (mirror 13, beam expander 14) and enters the recorder 12. The other part passes through the system of 2i (3 Forming a flat one-dimensional light beam enters the beam splitter-multiplier, creating the desired number of directions of sounding and with the help of mirrors 5, 6 is directed to the phase object under study 9 so that the direction of the translucency intersects It was at the same point where the origin of the coordinate system (x, y, z) is located. Passed through the object at an angle

Claims (1)

  1. METHOD FOR MEASURING SPATIAL ALLOCATION OF INTERNAL; HETEROGENEITY OF THE OBJECT, consisting in the fact that they produce multi-angle probing of the measured object with a flat one-dimensional beam of penetrating radiation, for each sounding direction the transmitted radiation is uniformly converted in the direction of the axis perpendicular to the axis of the one-dimensional beam, into two-dimensional, the radiation is rotated along the sounding direction and all the transformed streams are spatially combined, characterized in that, for the purpose of measuring in real time, the spatially combined streams are alternately ayut registrar with contrast ratio y = -2N, where N - number of angles sensing.
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SU813243633A 1981-01-30 1981-01-30 Method of measuring spatial distribution of object internal heterogeneity SU999808A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2586448C2 (en) * 2011-03-04 2016-06-10 Конинклейке Филипс Н.В. Combination of two-dimensional/three-dimensional images

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
1. Пресн ков Ю.П. Вычисление двумерных функций показател прелом лени . Оптика и спектроскопи . 1976 т.40, вып.1,с.124. 2.A.F. Gmitro et al. Optical computears for reconstartinp, object from their X-Ray projections. Opti cal Engineering v.19 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2586448C2 (en) * 2011-03-04 2016-06-10 Конинклейке Филипс Н.В. Combination of two-dimensional/three-dimensional images

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