LU86742A1 - DEVICE FOR INTERFEROMETRIC ANALYSIS OF BODY DEFORMATION - Google Patents

Abstract

The invention relates to a device comprising the cooperation of two analysis systems operating at different wavelengths. The first system carries out a superposition of a graticule (2) engraved on the surface of a body (1) analysed with an optical graticule (8) and enables the in-plane deformations of the body (1) to be obtained by Moiré fringes. The second system carries out the superposition of an image of an optical graticule (10) projected onto the surface of the body (1) with an optical graticule (8) and enables information on the out-of-plane deformations of the body (1) to be derived by Moiré fringes. <IMAGE>

Description

21/2206 LU

GRAND DUCHY OF LUXEMBOURG

Patent N ° ~ ~ '* * "nn? Minister of 1 JAK.1987! Economy and the Middle Classes,,: ¾¾¾ Intellectual Property Service

itre e vre _ 1¾¾ LUXEMBOURG

• Application for an Invention Patent fa. / lotMAr.

I ------------------------------------------------- -, --------------- (1) I. Request ....... EUROPEAN COMMUNITY RE ATOMIC ENERGY (EURATOM) _________ (2) ..... Boot Postale 1907________________________ L-2920 LUXEMBOURG _____________'__; _____ 5 ___ ~ _____ --------— · .------------------: -------- ----: -.-- (3) deposit (s) this .. .......- 2JJAHJ3S ?: _____ I_1 -__ (4Ï à __________ hours, at the Ministry of Economy and Middle Classes, in Luxembourg : 1. the present request for obtaining a patent for an invention concerning: ----------.-------------------- ----------— (5) "Interferometric analysis device for the deformation of a body" _ 2. the description in language ............. ..... francais se________________de the invention in triplicate; 3 ........... a _______________________________ drawing board, in triplicate; 4. receipt of the fees paid to the Registration Office in Luxembourg, le __: __; 5.) la: d0lKg0ti "") d * y »KWXK) dat" KÄ: --------------------------- ------------------- ------------- Ä <x --- 1 —.— declares (assuming responsibility for this declaration), that the inventor (s) êfeK (are): (6) ....... Luciano PIRODDA, viale Morello 26, 1-09100 CAGLIARI, Italy__________

Mario MONTAGNANI. via G. Rosai 5, BOLOGNA, Italy _ ^ ______ ....... Carlo ...... ALBERTINI, via dei ..... Pini 17. ISPRA. Italy ___; ____________ sy "; eHd] qHet" t)) p "MKk) 6H9dft" xfeK] "Kd9 <d3 (toexatDte: pKBMté) dtoDB <(xlK9) x3) eKieBdo (x>" ie (7) _______________________________________________________________________________________________ x ) <eo {^ _: _, __________ ---------------------------------------- ---------------------------------------------------------- ------------------------------------------; ____ ________________________________________________: _______________________________ 1_________________ "M" »HiXdexOil <) .............................................. .................................................. ....................................._..... 1________________________________ elect (élKB) t) domicile for him (her) and, if designated, for his representative, in Luxembourg - Commission ..... of ___ ........ Communities ..... Europée.nn.es_-DG ... XIII / CJd ./. J_-Z92Q.LUXEMB.0.URG ........................ (12) is requesting the grant of a patent d invention for the object described and represented in the abovementioned appendices s, with postponement of this issue to ___________________ twelve .______________ months. (13)

Le Dépcfeapt / KttKgKXlKttX ........... C OMUNAUTE „EUR.0P E.ENN E ..... D £ .J _! _ ENERG LE_AIDMIQUE_LEURAIjOM) (14) H. KR (lz ^ i) ondé of power Π. Deposit Minutes

The above mentioned invention patent was filed with the Ministry of Economy and the Middle Classes,

Service of Prt priété Intej ^ cteeti ^^ Luxembourg, dated: 2 0 JAK. 198?

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/ / V-5> Pr. The Minister of the Economy and the Middle Gasses, to .............................. .hours 5 'Jfd /' '

The head of the intellectual property department, / A 68007_ \ ÿ / »rrc, Aâëj / _! _ · ,; \ FYPI ΐΓΑπηνς rfi attvfs ai; Fnw ^ WL / TpVpajil ^ QT · (11 if applicable "Request for certificate of addition to main pretzel, to main patent application No ............ of ..... ...... Λ- (2) enter the last name, first name, profession.

addressed to the applicant, when the latter is a private individual with corporate name, legal form, address of head office, when the applicant is a legal person - (3) enter the surname, first name, address of the professional representative, industrial property attorney, with special powers, if any: "represented by ............ acting as agent" '- 1 - W 274

The invention relates to a device for interferometric analysis of deformations of a body, comprising a reticle engraved on the surface of this body, a first light source illuminating said surface, and a first photosensitive film disposed parallel to said surface and receiving the light reflected from this surface through a first optical reference reticle of such dimensions that Moiré fringes are obtained on the photosensitive film by the superposition of the etched reticle and said reticle optical.

Such a device is known, for example from the book "Mecanics of solids", edited by A. Lagarde 1981, Proceedings of the IVTAM Symposium (1979).

Such systems have made it possible to measure the deformation with good accuracy based on the interference of two reticles. We distinguish on this subject between two principles, the first consisting in projecting optically 'a crosshair of lines on the object to analyze and to observe the image of this crosshair through a reference crosshair, thus creating interference fringes of the Moiré type. If the illumination and / or a recording film are placed at adequate angles with respect to the surface analyzed, any deformation of this surface out of its plane results in a modification of the Moiré fringes.

Another known system establishes the interference between a reticle etched in the surface to be analyzed and an optical reticle and makes it possible to observe deformations of the surface in its own plane.

i ί r - 2 -

Both systems provide black / white information and can use black / white film for recording.

For the analysis of rapid phenomena, for example rupture phenomena, one can only use one of the systems mentioned at a time so far, which is a drawback especially when the phenomena to be analyzed are not strictly reproducible.

The object of the invention is to propose an analysis device according to the preamble of claim 1 making it possible to simultaneously extract information concerning the deformation in plane than the deformations out of the plane of the surface to be analyzed.

This object is achieved according to the invention by the fact that a second light source of a second wavelength, different from that of the first source, projects onto the surface to be analyzed along an oblique axis. image of a second optical reticle, that the light reflected from said surface is recorded by a photosensitive film for the second wavelength after passing through a third optical reticle of dimensions such as to obtain Moiré fringes by the superposition of the second and third reticles.

Preferably, the fringes obtained in the two wavelengths are recorded on a single color photosensitive film, which must therefore be sensitive to the two wavelengths in question.

As regards preferred examples of implementation of the invention, reference is made to the subclaims.

The invention will be described below in more detail using i - 3 - an embodiment and the single figure, which schematically shows an analysis device according to the invention.

The device as shown in the figure constitutes a combination of two systems per se known. One of the systems makes it possible to analyze the deformations of a surface of a body 1 in plan, while the other is sensitive to deformations out of the plane, an exaggerated deformation of this type being represented by broken lines 2 .

According to the first system, the surface of the body 1 carries a reticle 3 such as an orthogonal network of lines in a color of a first given wavelength. This reticle is illuminated by a light source 4 at any angle, the wavelength of this light source being chosen so that the reticle 3 can be recorded on a photosensitive film 5 of a camera 6. On the optical path between the body 1 and the film 5 there is a slide 7, which carries another reticle 8 of the same type as the reticle 3, the lines of this reticle 8 being opaque at said wavelength. The film 5 is arranged parallel to the surface of the body 1 and facing it.

In operation, the film 5 receives a superimposed image of the reticles 3 and 8, which is in the form of Moiré fringes, the color of these fringes being that of the source 4.

When there are deformations of the surface of the body, one can distinguish between two types of deformation, namely that in plan and that out of the plane. Deformations of the first type result in a modification of the Moiré image on film 5.

For the analysis of deformations of the second type, a second system working at another wavelength is used.

i i - 4 -

It comprises another light source 9 and a slide 10 with a second reticle similar to the reticle 8 of the device 6, but affecting another wavelength, namely that of the source 9. The axis of incidence light from this source on the surface 3 is oblique. The reticle 3 which is engraved on the surface of the body is not "visible" by the light emitted from the source 9, but there is interference between the image of the slide 10 projected on the surface of the body 1 and another reticle etched on slide 7 of the camera 6. This other reticle may be the same as that used for the first system, if the color used for this reticle is likely to block the light of the two lengths of wave.

In consideration of the fact that the second system does not "see" the reticle 3 etched on the body 1, a deformation of the body in plan does not affect the interference fringes created by the second system. On the other hand, any deformation of the sample 1 out of its plane, for example a convex shape 2, modifies the interference fringes of the second system. The device according to the invention therefore makes it possible to simultaneously record, but in a dissociable manner, information relating to the deformations in the plane and those of the deformations outside the surface plane of the body 1.

The invention is not limited to the embodiment described above. One can in particular provide several light sources 9 and several slides 10, which are distinguished on the one hand by their angle of incidence of the light on the body 1, and on the other hand by the wavelength of the light issued.

Furthermore, the reticle projected onto the sample by the second system or the second systems can be generated not by a slide such as 10, but by a holographic technique by using a laser source as the light source 9, and by creating a holographic interference between two, V '- 5 - beams coming from this same source. Even the source 4 can be constituted by a laser source.

In addition, the invention can also be implemented by completely dissociating the two systems, that is to say by providing two cameras such as 6 for the two systems, each provided with a film such as 5 and a slide such as 7 with a crosshair.

Finally, the first system can also be duplicated by using two different wavelengths. In this case, ..il. two crosshairs such as 3 must be engraved on the sample and two optical crosshairs such as 8 must be provided in the camera. If the pitches of the reticles which are used for the two wavelengths are very different, there is the possibility of a coarse analysis simultaneously with a fine analysis of the deformations of the body 1.

It should be noted that the device according to the invention allows a very fine analysis of the deformations which is limited only by technological problems of the production of a reticle of small pitch. On the other hand, the sensitivity is practically not limited by that of the photosensitive film, because one records fringes there and not the lines. However, the fringes are few and wide, while the lines are very numerous and thin.

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Claims (5)

1. Device for interferometric analysis of the deformations of a body, comprising a reticle (3) engraved on the surface of this body, a first light source (4) illuminating said surface, and a first photosensitive film (5) disposed parallel to said surface and receiving the light reflected from this surface through a first optical reticle (8) of reference of such dimensions that Moiré fringes are obtained on the photosensitive film by the superposition of the etched reticle (3) and said optical reticle (8), characterized in that a second light source (9) of a second wavelength different from that of the first source projects on said surface along an oblique axis the image of a second optical reticle (10), that the light reflected from said surface is recorded by a photosensitive film for the second wavelength after passage through a third optical reticle (8) of dimensions such that fran ges de Moiré by the superposition of the second and third optical reticles. 2. Device according to claim 1, characterized in that the two fringe systems are recorded on a single color photosensitive film (5) which is sensitive to the two wavelengths. 3. Device according to claim 1 or 2, characterized in that the first (8) and / or the second optical reticle (10) is obtained according to the holographic technique using a laser source as a light source (4, 9). 4. Device according to one of the preceding claims, characterized in that there are at least two reticles (such as 3) engraved on said surface of pitch and of different color i „* * - 7 - rents, and correspondingly at least two first optical reticles (such as 8) making it possible to create at least two systems of Moiré fringes of the same type but of no different. 5. Device according to one of the preceding claims, characterized in that there are at least two second optical reticles (such as · 10) of different color and pitch, and correspondingly at least two third optical reticles (8) allowing to create at least two systems of Moiré fringes of the same type but not different. Luxembourg, January 19, 1987 For lia? Commission;! "HL ^ ONZ / i dd - I '· - Λ. Îj 'Jjf I 1 A a * J "Il TOy v