WO1998019133A1 - Dispositif de controle dimensionnel sans contact ultrasonore - Google Patents
Dispositif de controle dimensionnel sans contact ultrasonore Download PDFInfo
- Publication number
- WO1998019133A1 WO1998019133A1 PCT/FR1997/001934 FR9701934W WO9819133A1 WO 1998019133 A1 WO1998019133 A1 WO 1998019133A1 FR 9701934 W FR9701934 W FR 9701934W WO 9819133 A1 WO9819133 A1 WO 9819133A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- tip
- distance
- sample
- waves
- receiving member
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B3/00—Methods or apparatus specially adapted for transmitting mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B3/02—Methods or apparatus specially adapted for transmitting mechanical vibrations of infrasonic, sonic, or ultrasonic frequency involving a change of amplitude
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/004—Mounting transducers, e.g. provided with mechanical moving or orienting device
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K13/00—Cones, diaphragms, or the like, for emitting or receiving sound in general
Definitions
- the present invention provides a means of accessing, without contact, the dimensional control or even the roughness of surfaces of optical quality as well as very variable mechanical impedance.
- the invention relates to a device for non-contact measurement of the distance separating an elementary surface from a read head consisting of one or more transmitters as well as one or more receivers consisting of electromechanical transducers X coupled to amplifiers mechanical C (figure 1).
- the probe object ECH (FIG. 3) has a mechanical impedance different from that of the medium in which the ultrasound generated at the level of the read head is propagated.
- the propagation medium between the object to be probed and the read head is ambient air, but any other gaseous medium could be suitable.
- Mechanical amplifiers are solid spikes with a generally conical profile and bandwidth suitable for amplifying an ultrasonic movement of impulse or harmonic type, according to a guided asymmetric mode such as for example a bending mode, to say a mode whose component of displacement orthogonal to the axis of cylindrical symmetry of the cone is antisymmetric compared to this axis.
- a guided asymmetric mode such as for example a bending mode, to say a mode whose component of displacement orthogonal to the axis of cylindrical symmetry of the cone is antisymmetric compared to this axis.
- the use of an antisymmetric mode coupled to a focusing tip has the unique advantage of being able to generate with sufficient intensity, locally and in a directive manner, an CHP ultrasonic field (FIG. 2) which is oriented in the direction of the object to probe. Measurement of flight time in steady state impulse or the amplitude and phase of the echo in harmonic regime returned by the probed surface makes it possible to measure the distance separating a surface element SS (figure 8) of
- FIG. 1 illustrates by a diagram in axial section a case where a tip C is coupled to a piezoelectric element X placed in a cylindrical compartment Cpt, the compartment and the tip being machined in the same metal rod in order to optimize the transfer of the mechanical stress between the piezoelectric element X and the tip C
- FIG. 2 is a qualitative representation of the directivity diagram in emission as in reception of the CHP ultrasonic field generated in the air by the system of FIG. 1, when the end of the tip vibrates in a direction SV.
- FIG. 3 schematically illustrates a means making it possible to locally modify the direction of the emission maximum of a system identical to that of FIG. 1 by machining the end of the bevel cone, FIG.
- FIG. 4 schematically represents an example making it possible to increase the directivity of a transmitter-receiver system by polishing the end of a tip
- FIG. 5 is a schematic view in axial section illustrating a case of maximum direct coupling between two systems identical to that of FIG. 1, one playing the role of transmitter E, the other that of receiver R
- FIG. 6 is a schematic view in axial section illustrating the case of a direct localized coupling between two systems identical to that of FIG. 1
- FIG. 7 illustrates schematically according to an axial section view the case where the internal generatrices of the conical points form an acute angle ⁇ on which the position of the direct coupling zone between the corresponding points depends ndant to the shortest acoustic path connecting the bases of the points
- FIG. 5 is a schematic view in axial section illustrating a case of maximum direct coupling between two systems identical to that of FIG. 1, one playing the role of transmitter E, the other that of receiver R
- FIG. 6 is a schematic view in axial section illustrating the
- FIG. 8 illustrates a configuration with two opposing tips making it possible to detect the presence of a surface of small dimensions by indirect coupling between the two tips
- FIG. 9 schematically illustrates the principle of measuring the distance separating a read head from the surface of a sample, independently of the nature and the temperature of the surrounding gas
- FIG. 10 illustrates schematically and in perspective a simple means for obtaining a reference curved surface whose end of the associated radius of curvature is located on the cylindrical axis of symmetry of the tapered tip
- FIG. 9 schematically illustrates the principle of measuring the distance separating a read head from the surface of a sample, independently of the nature and the temperature of the surrounding gas
- FIG. 10 illustrates schematically and in perspective a simple means for obtaining a reference curved surface whose end of the associated radius of curvature is located on the cylindrical axis of symmetry of the tapered tip
- FIG. 11 schematically illustrates a profilometer operating in sinusoidal regime and using a method of disturbing the coupling field between the tips and the probed surface using a vertical screen interposed between the two points and whose distance from the probed surface is modulated
- Figure 12 shows a diagram matically a system with two read heads making it possible to measure the thickness of an object without contact
- FIG. 13 represents a wiring diagram of the electrical excitation generator of the transmitter transducer
- FIG. 14 is a block diagram of a contactless position detection device according to the invention. It will be noted at the outset that, from one figure to another, similar identical elements or parts are designated as far as possible by the same reference signs.
- a bundle of tapered solid tip C for example a solid cone, generates a packet of ultrasonic waves propagating in an asymmetric propagation mode with respect to the cylindrical axis of symmetry of the tip (typically a bending mode). This is obtained for example using a ferroelectric ceramic with alternating polarization bonded to the flat base of the cone ⁇
- the material displacement vector has a rectilinear polarization SV oriented perpendicularly to the segment delimiting the alternating polarization of the ceramic bonded to the flat base of the cone.
- the inventive aspect of this system lies, on the one hand, in the focusing effect produced by the slightly dispersive tapered profile of the tip, on the other hand, in the use of a transverse wave which makes it possible to generate a direct and intense radiation pattern in the air in the vicinity of the tip as illustrated in FIG. 2, finally in the mounting of the piezoelectric element X and of the focusing tip which ensures both good mounting strength at level of the base of the tip and an optimal transfer of the stress generated by the piezoelectric element X in the focusing tip.
- FIG. 1 illustrates how an optimal transfer of the stress in the conical tip C is ensured when the tip and the compartment C pt housing the piezoelectric element X are machined or cast in a single block.
- the absorbent is confined in the compartment Cpt to the using plug S, insulating ring AI and threaded cap CAP.
- the mode of flexion which propagates in the tip is generated either by the piezoelectric element which resonates naturally in shear of thickness such as a cut X or Y + 163 0 of a crystal of lithium niobate, or by a conversion of a longitudinal wave into a transverse wave.
- the echo returned by the material is recovered, either with the same probe, or with another probe R identical to the first.
- the use of a second probe has a number of advantages. For example, the advantage of not being disturbed by the echoes in the transmitting tip, on the other hand of being able to detect in a preferred direction determined by the directivity diagram of the receiving piezoelectric element.
- the coupling between the two probes is indirect.
- there is also a direct coupling between the two probes which depends on the orientation of one probe relative to the other. Direct coupling is obtained when the direction of the mechanical vibration SV at the end of a tip is parallel to the direction of the maximum sensitivity of the transducer of the receiving tip.
- the direct coupling depends on the angle ⁇ made by the tips between them (figure 6) as well as on the length ê of coupling and the distance d separating the tips.
- Optimal contactless coupling is obtained when the axes are parallel, the distance d separating the tips is minimal without the tips touching each other and that the coupling length l is approximately one wavelength ( Figure 5) .
- a pulse transmitted in the receiving cone splits into two pulses due to the reflection at the end of the receiving cone.
- the generatrices of the points form an acute angle ⁇ (FIG. 7)
- ⁇ there is a particular value of ⁇ such that the shortest flight time allowing a packet of waves to travel from the base of the emitter cone to the base of the receiving cone corresponds to an acoustic path necessarily passing through the ends of the tips.
- direct coupling can be used to efficiently and contactlessly generate ultrasound in another solid medium which may possibly be in motion relative to the emitter.
- Direct coupling can also be used to detect the presence of an object interposed between the tips.
- An important application of optimal direct coupling concerns acoustic thermometry. With a transceiver system similar to that of FIG. 5 combined with a polishing of the tips so as to obtain a planar end according to the diagram in FIG. 4 increasing the facing surface between the two tips, an acoustic interferometer of small dimensions applicable in thermometry. Indeed, the facing surfaces at the end of the tips constitute a small resonant cavity whose resonant frequency depends on the temperature of the gas included between the facing surfaces.
- c 0 the speed of longitudinal waves at temperature T extrapolated at zero pressure to stay within ideal gas conditions
- the coupling zone is located at the end of the emitting tip in the case of FIG. 6.
- a minimal coupling is obtained when, starting from the maximum direct coupling, one makes undergo one or better of the two points a rotation of ⁇ / 2 around their axis.
- the wavelength of waves in air at 1 MHz is 331 ⁇ m at 273 K.
- electronic wave packet detection based either on the detection of the energy of the wave packet, it ie based on the detection of the quadratic value of the amplified signal, that is, when the waveform is fixed as is the case here for direct coupling, based on the simple triggering of a comparator, it is possible reach a resolution on the arrival time of the wave packet equal to a fraction of the pseudo-period of the wave packet.
- the vertical resolution of a position detector constituted by a system of two points can be of the order of a micrometer.
- the lateral resolution depends on the inclination of the axes of symmetry of the points relative to the probed surface as well as on the size and the radius of curvature of the points at their ends. It is of the order of a few tens to a few hundred micrometers.
- the directivity of the tips, in transmission as in reception, can be greatly increased by polishing the end of a tip so as to have a locally planar surface EP (FIG 4).
- One of the preferred aspects of this invention is to operate the system in pulsed mode. It goes without saying that it is also possible to operate the system in sinusoidal mode. This operating mode provides a signal gain, in particular when the operating frequency is a fundamental or harmonic mechanical resonance frequency of the transmitter E and / or of the receiver R.
- the transmitter as well as the receiver being constituted by a tip focus
- a profilometric measurement There are several ways to do a profilometric measurement. One of them consists in mechanically slaving the read head at a constant distance from the profile and recording the electrical servo signal as a function of the position, the other moving the two points in a plane and observing variations in the time of flight of the wave packet. In the latter case, the measurement accuracy is more random when the surface profile varies rapidly spatially because the lateral resolution of the system depends on the tip-sample distance. For example, for a tip-sample distance equal to h (FIG. 3), the radius r of the coupling zone with the probed surface is determined by the interval dt separating the reference instant of arrival of the wave packet determined by the electronics for detecting the arrival time of the head of the packet, as well as the speed c, of the waves
- V cg2.dt 2 + 2.dt.Cg.h V cg2.dt 2 + 2.dt.Cg.h.
- the radius of the coupling zone with the probed surface does not allow the lateral resolution of the pulse regime to be preserved.
- Synchronous detection of the disturbed field at the frequency fi then makes it possible to retain only the information on the profile of the object in the immediate vicinity of the screen.
- the resolution obtained on the profile depends on the fineness of the screen in the vicinity of the surface of the object probed.
- the screen can consist for example of a PSC plate at the end of which is fixed a razor blade.
- the vertical displacement of the razor blade is obtained by exciting the first symmetrical Lamb So mode in the glass plate using a PZT ceramic strip glued to the edge of the plate and excited at the frequency fi of resonance longitudinal of the glass plate.
- the curved reference surface is a portion of tube covering an angular sector strictly less than 180 ° so as not to prevent the points from approaching.
- the tube portion is cut from a tube with an internal diameter D equal to the external diameter of the cylindrical compartment Cpt housing the piezoelectric element X of FIG. 1.
- the tube portion is then fixed by one of its sides on the cylindrical base of the receiving probe such as that of FIG. 1. This greatly facilitates the agreement between the axis of the tube portion and the axis of the tip.
- the drawback of this arrangement lies in the fact that the reference distance h ref equal to D / 2 at the end of the tip decreases when one goes up the axis of the receiving tip. This drawback is eliminated by creating an oblong hole on the portion of tube in the angular sector corresponding to the maximum sensitivity of the receiver.
- a total flight time of a packet of waves from the base of a transmitting probe is broken down into a flight time ti associated with the flight time in the first peak, accumulated by a flight time t 2 in the second peak, accumulated by a time of flight tg m in the gas towards the sample (and tg r in the gas towards the reference plane).
- the flight times t m and t re f are expressed by the relationships:
- the position measurement hm can thus be an absolute measurement and be carried out independently of the speed c, therefore independently of the temperature, by carrying out the ratio ⁇ t m / ⁇ t r ef.
- the measurement then only depends on the precise knowledge of h rt ; f, ⁇ t r éf and ⁇ t m .
- the time intervals ⁇ t m and ⁇ t rc f are quantified using a high frequency clock.
- N m and N re f are the results of the integer division of ⁇ t m and ⁇ t ref by the period Tek of the clock.
- FIG. 13 represents the wiring diagram of a step generator making it possible to periodically charge the transmitting transducer X with current.
- the generator consists of 2 oscillators, one OSC1 having the aim of charging a reservoir capacitor C23 the other OSC2 to open a transistor by which the piezoelectric element X is excited.
- the presence of the inductance L1 and of the diode Dl makes it possible to reduce the rise time of the step and to increase the amplitude thereof to a value close to twice the value obtained with the voltage step-up stage ETN.
- the voltage step-up stage is composed of diodes (D2 to D21) and capacitors (C3 to C22). It is supplied by the output ST1 of the oscillator OSC1.
- the oscillators are supplied with symmetrical voltages + Vcc and -Vcc.
- the frequency of the OSC1 oscillator is of the order of megaHertz while that of OSC2 is of the order of kiloHertz.
- the capacitors C23, C24 and the transistor Tl must support the high voltage generated by the stage ETN.
- h 0 e + h ml + h m2 .
- h ⁇ separating the faces of the sample from the read heads are then measured.
- e h 0 - h mI - h m2
- the distance ho separating two read heads must be slightly greater than the reference distances h re n and h re f 2 to prevent a mutual coupling between the heads from disturbing their measurement window (defined for each head by the coupling signal direct and echo from the associated reference surface).
- One technique for carrying out a differential measurement consists in sampling the analog signals for example on eight bits in amplitude and in saving them in memory to then be able to carry out a digital processing.
- the sampling of analog signals can be limited to the measurement window, that is to say about a maximum of 80 ⁇ s for a reference tip-surface distance of 10 mm in the air.
- the memory depth for each head is 7.6 kbytes maximum corresponding to a temperature range of -100 ° C to +250 ° C.
- the temperature resolution of the device in pulse mode is 0.1 ° C.
- the resolution of the device on a position measurement is 1.7 ⁇ m at 0 ° C.
- FIG. 14 gives the block diagram of a device according to the invention making it possible to produce a position detector of micrometric resolution without temperature correction, using a reading head with two tips.
- the measurement of the distance h m separating the read head from the surface of the sample consists in exciting with the aid of the step generator 1 the emitter transducer of the emitter tip 2 which generates a packet of waves which will reflect on the sample 16 to be detected by the transducer of the receiving tip 3.
- the two tips are oriented so that
- SUBSTITUTE SHEET (RULE 26 have minimal direct coupling.
- the detected signal is then amplified by an amplifier 4 then optionally shaped by being squared by a quadrator 5 and integrated twice using the active integrators 61 and 62.
- the signal returned by the transducer of the receiving tip contains a first packet of D waves due to a residual direct coupling between the tips as well as another packet of I waves due to the indirect coupling between the two tips and the probed surface, delayed by a time ⁇ t m proportional to h m .
- the D and I wave packets are isolated using the monostables 71 and 72 triggered on the rising edge and the monostable 73 triggered on the falling edge, as well as the logic gate ET 81
- the SI signals are thus obtained, the rising edge of which corresponds to the arrival of the D and S2 wave packet, the rising edge of which corresponds to the arrival of the I wave packet.
- the flight time ⁇ t m is obtained at l using the logic function ET 83 between the signal SI and the signal from the monostable 74 triggered on rising by the signal S2.
- a clock 9 of frequency 80 MHz makes it possible to quantify the duration ⁇ t m by an integer Nbcd equal to the integer division of ⁇ t m by the period of the clock.
- the number N bcd is counted using the BCD counters 101, 102, 103, 104.
- a monostable 75 is triggered to, on the one hand, allow to reset (Reset) the counters after an additional delay imposed by the monostable 76 and, on the other hand, to create a bit
- a parallel interface 1 1 using a programmable peripheral interface adapter of the Intel 8255 type makes it possible to transmit to a microcomputer the binary word consisting of
- a direct display of the data is also possible using a 4-digit multiplex LCD display 13.
- Each of the four digits is addressed via the address bits al and a2 controlling a decoder 15 which itself controls the three-state drivers 121, 122, 123, 124.
- the address bits a1 and a2 are incremented via an oscillator counter CD4060 actuated using the AND gate 82 by a high level of the bit of presence of AffEn data.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP97912274A EP0934505A1 (fr) | 1996-10-28 | 1997-10-28 | Dispositif de controle dimensionnel sans contact ultrasonore |
US09/297,429 US6269700B1 (en) | 1996-10-28 | 1997-10-28 | Contactless ultrasonic device for dimensional inspection |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR96/13107 | 1996-10-28 | ||
FR9613107A FR2755225B1 (fr) | 1996-10-28 | 1996-10-28 | Dispositif de controle dimensionnel sans contact ultrasonore |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1998019133A1 true WO1998019133A1 (fr) | 1998-05-07 |
Family
ID=9497084
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR1997/001934 WO1998019133A1 (fr) | 1996-10-28 | 1997-10-28 | Dispositif de controle dimensionnel sans contact ultrasonore |
Country Status (4)
Country | Link |
---|---|
US (1) | US6269700B1 (fr) |
EP (1) | EP0934505A1 (fr) |
FR (1) | FR2755225B1 (fr) |
WO (1) | WO1998019133A1 (fr) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7355819B2 (en) * | 2000-03-31 | 2008-04-08 | Seagate Technology Llc | Machining actuator periphery to reduce resonance variation |
TWI222912B (en) * | 2002-08-01 | 2004-11-01 | Nanya Technology Corp | Method of detecting pore depth on surface of polishing pad |
FR2901612B1 (fr) * | 2006-04-13 | 2009-02-13 | Jean Pierre Nikolovski | Dispositif de mesure d'un parametre d'un fluide en ecoulement utilisant un transducteur a pointes |
WO2011088393A2 (fr) * | 2010-01-15 | 2011-07-21 | University Of Utah Research Foundation | Dispositif à ultrasons pour la mesure de température |
WO2016087719A1 (fr) | 2014-12-04 | 2016-06-09 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Procédé et système de caractérisation de propriétés mécaniques et thermiques |
CN110487894A (zh) * | 2019-08-15 | 2019-11-22 | 湖北三江航天江北机械工程有限公司 | 碳纤维缠绕壳体封头超声波检测探头及检测方法 |
CN111632285B (zh) * | 2020-05-28 | 2022-05-03 | 杜颖 | 一种关节痛风治疗装置 |
CN113899816B (zh) * | 2021-09-10 | 2022-06-17 | 国营芜湖机械厂 | 一种t型复合结构的超声无损检测装置及方法和r区检测方法及装置 |
CN114371217A (zh) * | 2021-11-27 | 2022-04-19 | 北京工业大学 | 一种基于密集阵列的智能兰姆波缺陷定位方法 |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0045456A2 (fr) * | 1980-08-02 | 1982-02-10 | Heribert Ballhaus | Appareil d'exploration de surfaces |
JPS60131437A (ja) * | 1983-12-20 | 1985-07-13 | Mitsubishi Electric Corp | 超音波式室温測定装置 |
WO1996011378A1 (fr) * | 1994-10-06 | 1996-04-18 | Universite Pierre Et Marie Curie (Paris Vi) | Dispositif d'acquisition de coordonnees d'une source acoustique appliquee a une plaque |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4281407A (en) * | 1979-12-14 | 1981-07-28 | Rca Corporation | Surface acoustic wave pickup and recording device |
US4594897A (en) * | 1984-01-27 | 1986-06-17 | Bethlehem Steel Corporation | Inspection of the internal portion of objects using ultrasonics |
-
1996
- 1996-10-28 FR FR9613107A patent/FR2755225B1/fr not_active Expired - Fee Related
-
1997
- 1997-10-28 EP EP97912274A patent/EP0934505A1/fr not_active Withdrawn
- 1997-10-28 US US09/297,429 patent/US6269700B1/en not_active Expired - Fee Related
- 1997-10-28 WO PCT/FR1997/001934 patent/WO1998019133A1/fr not_active Application Discontinuation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0045456A2 (fr) * | 1980-08-02 | 1982-02-10 | Heribert Ballhaus | Appareil d'exploration de surfaces |
JPS60131437A (ja) * | 1983-12-20 | 1985-07-13 | Mitsubishi Electric Corp | 超音波式室温測定装置 |
WO1996011378A1 (fr) * | 1994-10-06 | 1996-04-18 | Universite Pierre Et Marie Curie (Paris Vi) | Dispositif d'acquisition de coordonnees d'une source acoustique appliquee a une plaque |
Non-Patent Citations (3)
Title |
---|
IMANO K ET AL: "A NONCONTACT THICKNESS MEASUREMENT OF THIN SAMPLES USING 40 KHZ ULTRASONIC WAVE", IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS, COMMUNICATIONS AND COMPUTER SCIENCES, vol. 76A, no. 10, 1 October 1993 (1993-10-01), pages 1861/1862, XP000422034 * |
PATENT ABSTRACTS OF JAPAN vol. 009, no. 292 (P - 406) 19 November 1985 (1985-11-19) * |
S. TOSIMA ET AL: "Surface acoustic wave stylus:Part I-Pickup and recording devices", RCA REVIEW, vol. 44, no. 3, September 1983 (1983-09-01), PRINCETON,NJ,USA, pages 430 - 464, XP002033033 * |
Also Published As
Publication number | Publication date |
---|---|
FR2755225B1 (fr) | 1999-04-02 |
US6269700B1 (en) | 2001-08-07 |
FR2755225A1 (fr) | 1998-04-30 |
EP0934505A1 (fr) | 1999-08-11 |
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