WO2004085978A2 - Procede et installation d'imagerie acousto-optique - Google Patents
Procede et installation d'imagerie acousto-optique Download PDFInfo
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- WO2004085978A2 WO2004085978A2 PCT/FR2004/000640 FR2004000640W WO2004085978A2 WO 2004085978 A2 WO2004085978 A2 WO 2004085978A2 FR 2004000640 W FR2004000640 W FR 2004000640W WO 2004085978 A2 WO2004085978 A2 WO 2004085978A2
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/021—Interferometers using holographic techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
- G01B9/02002—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies
- G01B9/02003—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies using beat frequencies
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
- G03H1/04—Processes or apparatus for producing holograms
- G03H1/08—Synthesising holograms, i.e. holograms synthesized from objects or objects from holograms
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
- G03H1/04—Processes or apparatus for producing holograms
- G03H1/0443—Digital holography, i.e. recording holograms with digital recording means
- G03H2001/0445—Off-axis recording arrangement
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
- G03H1/04—Processes or apparatus for producing holograms
- G03H1/0443—Digital holography, i.e. recording holograms with digital recording means
- G03H2001/0463—Frequency heterodyne, i.e. one beam is frequency shifted
Definitions
- the present invention relates to a method and an installation for acousto-optical imaging.
- acousto-optical imaging the beat of a local oscillator is detected with an acoustic component of a signal wave scattered by an object to be imaged, shifted in frequency by vibration to an acoustic frequency. From a point of said object to image from which we seek to obtain information of an optical nature.
- a multi-pixel detection device can be used, by summing on the pixels of the detection device, rather than over time, as described in "Ultrasonic tagging of photon paths in scattering media: parallel speckle modulation processing ”, Optics Letters, Vol. 24, No. 3, February 1, 1999, page 181.
- the local oscillator is of sufficiently low frequency to be detected by a multi detection device pixels, which generally has a low acquisition frequency. Nevertheless, a major problem remains, in that the weight of the local oscillator is generally too low. The heterodyne gain is then too low to be able to perform heterodyne detection with optimal noise.
- the present invention aims in particular to overcome these drawbacks.
- an acousto-optical imaging method of an object to be imaged comprising the steps consisting in:
- (g) obtain the coordinates of a measurement point of the object to be imaged, to which the digital information is relative. This prevents the reference wave, which serves as a local oscillator, from passing through the object to be imaged. This makes it possible to have a sufficient level of local oscillator, and to extract, with a better signal / noise ratio, information relating to the measurement point for example for imaging purposes, in particular medical imaging. In addition, this imaging method makes it possible to obtain an exploitable signal even with low acoustic or optical powers, for example compatible with the security standards for imaged tissues associated with medical imaging.
- step (f) an acoustic component of the part of the scattered signal wave applied to the detection device, this acoustic component being at a frequency corresponding to the sum of the frequency f of the incident wave and of a harmonic of the acoustic frequency f A (fi ⁇ Hf A , H non-zero integer); during step (a), said reference wave is generated at a frequency f R equal to or substantially equal to the sum of the frequency f ⁇ of the incident wave and said harmonic of the acoustic frequency f A (f R ⁇ f x ⁇ Hf A , H non-zero integer); during step (b), a focused acoustic wave is generated at a focal point located in the object to be imaged and during step (g), the coordinates of the measurement point are obtained, as being the coordinates of said focal point; repeating steps (a) to (g)
- step (f ') at least one digital item of information is obtained by decoding said digital information obtained during steps (f) of each iteration as a function of the frequencies used, and, during step (g), the coordinates d are obtained '' at least one measurement point of the object to be imaged to which the digital information obtained during step (f ') is relative, by decoding said digital information obtained during steps (f) of each iteration as a function frequencies used; the following sequence of operations is carried out: the frequency of the acoustic wave is scanned, which is focused on an interval of coordinate points ([U-Dx, U + Dx], V, W) extended around the coordinate point (U, V, W) along the first direction of the object, a scan of the frequency f R of the reference wave is carried out jointly so as to maintain f R substantially equal to or equal to f ⁇ ⁇ Hf A , H being a non-zero integer, we record for each pixel r and for each frequency f A an interferogram I (f A ,
- the complex amplitude E s (r) of the acoustic component is estimated from the interferogram I (r, t);
- the detection device used is a mono-pixel detector and, during step (f), the digital information is obtained as being the intensity of the field of complex amplitude E s (r) scattered by the object ;
- the detection device used is a multi-pixel detector, and during step (f), the digital information is extracted as being the sum over at least part of the pixels r of the intensity detection device the complex amplitude field E s (r) scattered by the object;
- a spatial filtering device is used, so as to limit, in at least one direction, the angular extent of the part of the scattered signal wave which is seen by each pixel of the detection device (an average angular direction can thus be defined for the part of the scattered signal wave which is seen by each pixel of the detection device);
- a spatial filtering device is used comprising a diaphragm, of dimensions X in a first diaphrag
- step (f4) the digital information is extracted as being a linear combination of the sums thus obtained in each zone (this linear combination possibly comprising only one term);
- the detection device comprises pixels arranged in a matrix comprising lines in a first detector direction and columns in a third detector direction, and step (f) comprises the following steps: (fl) a two-dimensional Fourier transform of the complex amplitude E s (r) is made, from the plane of the detection device to the space of the wave vectors, and a TF 2 E s field is thus obtained (k), 5 (f2) several summation zones are defined in the space of wave vectors,
- a first summation zone called the central zone
- a second summation zone called the left zone
- a third summation zone called the right zone
- a laser source of wavelength ⁇ emits '25 an emission wave, of frequency f L , means of amplitude modulation of the emission wave, generate a carrier wave of incident frequency fi, and at least one side band of amplitude modulation, which corresponds to a wave of frequency f R , 30.
- a semi-reflecting mirror transmits part of the side band wave and part of the carrier wave forming the incident wave, and reflects part of the carrier wave and part of the side band wave forming the wave reference ;
- a laser source of wavelength ⁇ emits an emission wave, of frequency f L
- a first acousto-optical modulator transmits part of the emission wave to form the incident wave on the object to be imaged, and moreover generates a first frequency-offset wave, the frequency of which is offset by a value ⁇ fi, possibly negative, with respect to the emission wave, and.
- a laser source of wavelength ⁇ emits an emission wave, of frequency f L
- a semi-reflecting mirror transmits part of the emission wave to form l wave incident on the object to be imaged, and transmits a second part of the emission wave
- a first acousto-optical modulator intercepts the second part of the emission wave and generates a first wave shifted in frequency, frequency offset by a value ⁇ fi, possibly negative, with respect to the emission wave
- the object to be imaged is biological tissue; the vibration generating device is used to obtain acoustic information of the area of the object to be imaged, and the digital information extracted in step (f) is used in conjunction with said acoustic information.
- the invention relates to an installation for acousto-optical imaging of an object to be imaged (OBJ) comprising:
- a vibration generating means for vibrating in a first direction and an object at an acoustic frequency f a a zone of the object to be imaged, - means for applying said incident wave to the object to be imaged, thereby generating a wave broadcast signal, a detection device, means for applying at least part of this signal wave diffused on the detection device, means for applying the reference wave to the detection device without passing it through the object to be imaged, which generates at the point r of the detection device an interferogram I (r, t) varying over time t, and means for extracting from the interferogram digital information and the coordinates of a measurement point of the object to be imaged, at which l digital information is relative.
- the installation also comprises the following elements: means for viewing said digital information relating to said measurement point of the object to be imaged, and means for moving the object to be imaged; the installation also includes a spatial filtering device, located downstream of the object to be imaged.
- FIG. 1 describes a first example of implementation of the method according to the present invention
- Figure 2 is a detailed diagram of an example of the device generation of two coherent waves according to the present invention
- FIGS. 3 and 4 are graphs representing the phase difference between two coherent waves as a function of time, generally and in a particular case
- FIG. 5 describes the first example of implementation of the method according to the present invention with the generation device of FIG. 2
- FIG. 6 represents a map of the signal obtained
- FIG. 7 represents a second example of implementation of the method according to the present invention
- FIG. 8 is a detailed diagram of another example of the device for generating two coherent waves according to the present invention
- - Figure 9 shows a detail of a third embodiment of the invention
- Figure 10 shows the rear face of the diaphragm used in the third embodiment .
- FIG. 1 shows a device for generating GEN waves, which generates: an incident optical wave INC, of wavelength ⁇ , of frequency fj, applied to an object to be imaged OBJ, and an optical reference wave REF of frequency f R.
- the incident INC and REF reference waves are consistent with each other and have a known phase difference ⁇ (t). These optical waves can be emitted in the visible range, or possibly in the infrared or the ultraviolet.
- the generation device GEN is adjusted so that the reference wave REF is offset in frequency with respect to the incident wave by a value equal to ⁇ f.
- a generation device as shown in FIG. 2.
- acousto-optical modulators MAOl and MA02 are for example made up of an acousto-optical cell of Tellurium dioxide (Te0 2 ), oriented at a given angle with the wave applied to it, namely the emission wave EMI and the shifted wave DEC respectively, and vibrating under the action of a high frequency generator, of frequency ⁇ fi and ⁇ f 2 respectively, and transmit at the same time a non-diffracted beam and a diffracted beam shifted in frequency.
- Te0 2 acousto-optical cell of Tellurium dioxide
- FIG. 5 represents the first embodiment of the invention with the generation device GEN of FIG. 2.
- the object to be imaged OBJ on which the incident wave INC is applied is a scattering object for waves optical, for example a sample of biological tissue.
- this sample can for example have a thickness of approximately 20 mm in the direction of propagation of the incident wave INC.
- This sample can in particular be compressed between a front plate and a downstream plate, perpendicular to the direction of propagation of the incident wave INC, these two plates being part of a sample holder (not shown).
- the upstream plate is for example entirely transparent and produced in particular from PMMA (Plexiglas®), while the downstream plate can for example be opaque and produced in particular from black bakelite.
- the object to be imaged OBJ and its sample holder can be installed in the center of a tank 1, for example 180 mm in diameter and 150 mm in height.
- This tank can be fitted with flat glass windows 50 mm in diameter, distant from
- This vibration generating device is oriented along a first direction of the object x 0 , and emits an acoustic wave of frequency f A along this first direction of the object x 0 .
- the vibration generator device TRANS then vibrates at the frequency f A a zone (Dx, Dy, Dz) of the object to be imaged, centered on a point of coordinates ( ⁇ , V, W) from which one seeks to obtain information.
- the extent (Dy, Dz) of the vibrating object zone corresponds approximately to the dimension of the focal zone of the acoustic wave, in the transverse directions y and z, that is to say in the plane normal to the propagation direction x 0 of the acoustic wave emitted by the transducer.
- the focal area is centered in (V, W).
- U corresponds to the distance between the acoustic transducer and the focal point thereof along the direction of propagation of the acoustic wave.
- the position and orientation of the transducer and the position of its focal point determine a measurement point of the object to be imaged OBJ, with coordinates (U, V, W).
- the incident wave INC is applied to the object to be imaged OBJ, in a second direction of object z 0 , possibly identical to the first direction of object x 0 , to form a scattered signal wave DIF which is scattered by object in all directions.
- part of the wave passes through the area (Dx, Dy, Dz) of the object to be imaged OBJ vibrating at the acoustic frequency f A.
- the movement of the points of the object liable to scatter generates a modulation at the acoustic frequency f A of the phase of the scattered wave.
- the vibration also produces a modulation of the optical index of the medium (also at the frequency f A ).
- the principle of acousto-optical imaging then consists in detecting on a DET detection device this acoustic component of the signal wave scattered by the object, by making this acoustic component of the signal wave scattered interfere with a local oscillator of neighboring frequency. This is carried out according to the invention, using the reference wave REF not passing through the object to be imaged OBJ, as a local oscillator for the detection device.
- the detection device has at least one detection cell in a plane x D , y D almost normal to the direction of observation z D (in the illustrative examples given in the figures, x D , y D , z D correspond to x 0 , ⁇ o, z 0 ).
- the CCD camera is chosen to have a quantum yield sufficient for a wave at 850 nm, for example 5% or more.
- a device is used to cause the diffused signal wave DIF coming from the object to be imaged OBJ and the reference wave REF to interfere on the detection device DET.
- these two waves must be almost collinear (forming an angle of 5 ° at most). It is possible, for example, to use a semi-reflecting plate or a beam-splitting prism to guide the reference wave REF to the detection device DET.
- the scattered signal wave DIF and the reference wave REF are made to interfere with the detection device, and an interferogram I (U, V, W, r, t) is recorded using this device, taken at time t, at point r of the detection device, and which corresponds to the measurement point of coordinates (U, V, W) of the object to be imaged, vibrating at the acoustic frequency f A.
- a CALC processing device can be coupled to this installation, capable of extracting from the recorded temporal interferogram digital information relating to the measurement point, with coordinates (U, V, W), this information being able to be subsequently displayed in an image of the object.
- This processing involves the calculation of the complex amplitude E s ( ⁇ , V, W, r) of the acoustic component of the scattered field, shifted in frequency by the acoustic vibration, on the detector.
- the CALC processing unit processes the time-varying interferogram I (U, V, W, r, t) by a four-phase demodulation as follows:
- N interferograms are then measured, each for a time T int , each interferogram corresponding to a distinct phase difference cpi known between the incident wave INC and the reference wave REF.
- the total duration of the measurement is for example of the order of a second.
- the 4-phase demodulation calculation can be carried out separately for each of the pixels r of the detection device.
- N N average interferograms I ⁇ ( ⁇ , V, W, r ), a N-phase demodulation of the N interferograms measured in order to obtain information on the complex amplitude E s ( ⁇ , V, W, r) of the acoustic component of the DIF signal wave scattered by the object.
- a second method for determining the complex amplitude E S (U, V, W, r) of the acoustic component consists, for example, in using the method known as "frequency chirping".
- the complex interferogram I (U, V, W, r) thus decoded is directly proportional to the complex amplitude E s (U, V, W, r) of the acoustic component of the DIF scattered signal wave that one seeks to determine.
- the size of the speckle grains is adapted to the size of the pixels of the camera.
- This first condition corresponds to the so-called “anti-aliasing” condition.
- this spatial filtering device will make it possible to isolate, according to the invention, the useful signal from the various noise components.
- This filtering device is for example constituted by a rectangular diaphragm 2, positioned for example directly downstream of the object to be imaged OBJ, perpendicular to the direction of observation (and therefore almost parallel to the detection device), for example between the object to be imaged OBJ and the downstream plate of the sample holder, and elongated in a direction.
- the observable zone upstream is thus of quasi-rectangular shape of approximately X mm and Y mm follow two directions perpendicular to the direction of observation. We can for example take z as the direction of observation, and x and y as axes for the diaphragm.
- this device COL further comprises a lens 3 placed between the tank 1 and the detection device DET.
- the focal point of lens 3 is located in the plane of the diaphragm
- DIF passes through this liquid.
- a focal lens L 250 mm is used, but other focal lengths may be suitable.
- This spatial filtering device reduces the angular extent of the GIS part of the DIF scattered signal wave which reaches the DET detection device, which can be useful for adapting the size of the speckle grains to the dimension of the pixels of the camera.
- the signal wave DIF scattered by the object to be imaged OBJ can occupy a wide solid angle, of the order of Tr steradants, and can be broken down into a superposition of plane waves very different K s wave vector elements.
- Each Kg wave vector has, in the plane of the detector (x D , y D ) ⁇ two coordinates K x and K y .
- SINC SINC (d x . ( X - K x0 )). SINC (d ⁇ . (K y - K y0 )) ⁇ 1 - Ea
- Ea is a extinction factor quantifying the loss of contrast of the fringes linked to the spatial integration of the detector
- d x and d ⁇ respectively represent the characteristic dimensions of the elementary detectors of the detection device in the directions x D and y D.
- the measurement must be limited to an elementary angular field of the signal wave SIG, corresponding to a cone of angle (+ ⁇ x ; ⁇ ⁇ y ) around the direction of the wave vector Ko of the wave of REF reference, the dimensions ⁇ x and ⁇ y of this elementary angular field having to be appreciably less than or equal to ⁇ / 2d x and ⁇ / 2d ⁇ respectively to respect said condition of “anti-aliasing”, where ⁇ is the length d 'reference wave REF.
- a judicious choice of the geometry of the COL spatial filtering device, and of the detection device allows furthermore to isolate the useful signal from the different terms which appear in the signal resulting inter alia from the analysis of the interferograms I (U, V, W, r, t).
- the discussion is carried out in the case of 4-phase demodulation but a similar discussion could be made in the case of detection by “frequency chirping”, or other similar technique.
- the interferogram I (U, V, W, r, t) corresponds to the total intensity I ⁇ seen by the detection device, ie the square of the module of the complex amplitude E (
- E ⁇ + E R + E s ) * corresponds to the interference between the part of the signal wave diffused at the frequency f ⁇ and itself, that is to say the interference between the ordinary speckle and the ordinary speckle
- E R .E R * corresponds to the interference between the reference wave and itself
- E R .E ⁇ * corresponds to the interference between the reference wave and the ordinary speckle
- E s * corresponds to the interference between the ordinary speckle and the acousto-optic speckle
- E R .E S * corresponds to the interference between the reference wave and the acousto-optic speckle, which constitutes the term carrying relevant information.
- the spatial filtering device COL makes it possible to reduce the angular extent of the wave coming from the object which can behave at the level of the detection device like a quasi-plane wave. This is in particular the case of the parts of the scattered signal wave having a complex amplitude Ei and E s .
- the reference wave REF is, in the present embodiment, a plane wave.
- Ei. E s * vary slowly in space along the x and y directions of the detection device. Furthermore, the term E R .E r * varies rapidly over time (at a frequency close to f) and is average at zero due to the low acquisition frequency of the detector. It is therefore easy to isolate by a suitable digital processing the relevant term E R .E S *, (which makes it possible to determine E s ) - If we choose an angular offset ⁇ ⁇ sufficient between the reference wave and the wave signal broadcast, this term is the only one to vary slowly in time, and rapidly in space along the y direction. This direction y corresponds to the direction of the width of the diaphragm, and to the direction y D of the plane of the detector.
- One way of extracting the relevant information consists in carrying out a Fourier transformation of the complex amplitude E S (U, V, W, r) calculated above, along the directions x and y of the plane of the detector (or possibly the only direction y).
- a signal TF E S (U, V, W, k) is then obtained, k being the space coordinate of the wave vectors.
- a map of the signal TF E s (U, V, W, k) obtained after the Fourier transform is shown in FIG. 6, which is an angular representation in the space of the wave vectors.
- N-phase demodulation should in theory make it possible to completely eliminate the interference term between the reference wave and the reference wave (E R .E R *), if the experience was perfectly stable over time. This is never perfectly the case, and there therefore remains a fairly large parasitic component. However, this term varies slowly along the x and y directions of the detector plane, which leads, in the space of wave vectors, due to the two-dimensional Fourier transform, to a narrow peak centered on the origin of the coordinates (zone 4 of figure 6).
- the demodulation with N phases should make it possible to eliminate the term of interference between the ordinary speckle and the speckle - ordinary (E ⁇ .E ⁇ *)> if the experiment was perfectly stable over time, and if the speckle remained static without decorrelating. This is never perfectly the case, and there therefore remains a fairly large parasitic component (zone 2 of FIG. 6). This term is even the dominant noise term for certain objects to be imaged in which the speckle does not remain static (for example for certain biological tissues).
- This interference term between the ordinary speckle and the ordinary speckle is, like the interference term between the reference wave and the reference wave, centered on the origin of the vector space. wave.
- the amplitude of the ordinary speckle field has a finite angular extent, which corresponds to the interval [-Y / 2L; Y / 2L].
- This noise thus presents an envelope of delimited pyramidal shape which is centered on the origin of the coordinates of the space of the wave vectors.
- the interference between the acousto-optic speckle and the acousto-optic speckle (E S .E S *) is a diagonal second order term. Apart from its lower intensity, this term does not differ from the interference term between the ordinary speckle and the ordinary speckle described above.
- the interference term between the reference wave and ' the ordinary speckle (E R .E ⁇ *) is at a frequency approximately f R - f ⁇ approximately equal to f A or approximately 2.2 MHz. This interference term is thus averaged at zero during the duration of acquisition of each image due to the low acquisition frequency of the detection device and can therefore be neglected.
- the interference term between the ordinary speckle and the acousto-optic speckle (E T _.E S *), in addition to being a second order term, also has a frequency approximately equal to the frequency of l acoustic wave f A and can therefore average zero at the time of acquisition of each image. It can therefore be overlooked.
- the relevant term to extract from the interference between the signal wave SIG and the reference wave REF is therefore the term of interference between the reference wave and the acousto-optic speckle (E R .E S *).
- This term corresponds to zone 3 and to the interval [Y3-; Y3 + ] of Figure 6.
- zone 3 being directly proportional to Y, we will be tempted to increase the width of the diaphragm so much. that we respect the condition of "aliasing" Y 3+ ⁇ / 2d ⁇ .
- Y 3 we will be tempted to increase the width of the diaphragm so much. that we respect the condition of "aliasing" Y 3+ ⁇ / 2d ⁇ .
- This efficiency corresponds to the loss of contrast of the interferograms due to the integration of the interferograms on pixels of finite size. For contiguous pixels, there is an efficiency factor following a sine law similar to that introduced previously for "aliasing".
- Y 3+ being equal to 2Y / L, this makes it possible to adapt, according to the laser used and the detector used, the characteristics of the spatial filtering device.
- FIG. 6 thus represents the cartography of the zones obtained in the space of the wave vectors by the present invention after the two-dimensional Fourier transform.
- This map can be broken down into a central column or zone 2, of extent [-Y / L, Y / L], a left column or zone 1, and a right column or zone 3.
- zone 4 represents the interference term between the reference wave and itself (E R .E R *).
- zone 3 represents the region of the space of wave vectors where the useful signal according to the invention is detected.
- zone 3 could of course be located on the left of FIG. 6.
- the relevant information which makes it possible to calculate the complex amplitude E s of the acoustic component, corresponds to the interference between the reference wave and the acousto-optic speckle (E R .E S *).
- Numerical information relating to the measurement point (U, V, W) of the object to be imaged is for example obtained by summing the intensities calculated on the pixels of the area 3 (.
- the choice of the angle ⁇ ⁇ makes it possible to properly separate the signals obtained, but the adequate positioning of the device making it possible to use a given angle ⁇ ⁇ , may require a control step.
- this control step an image is obtained, for example by suppressing the acoustic wave and by adjusting the frequency f R of the reference wave, so as to detect the component of the field scattered at the frequency f ⁇ .
- the lens is positioned precisely so that a clear image of the area seen through the diaphragm 4 is obtained by Fourier transform of the signal detected in the plane of the detection device.
- the edge of the calculation matrix corresponds to the “aliasing” condition.
- the control step ensures, for example, that the outer edge of the area containing the useful signal is not too near the edge of the calculation matrix, and / or that the noise-containing area and the area containing the useful signal are in contact at the internal edge of this area, but do not overlap.
- FIG. 7 represents a second example of implementation of the method according to the invention in which the spatial filtering device is not used. Indeed, for low laser intensities, and if the speckle decorrelation term is not too large, the “shot noise” becomes the dominant noise. This is the case when, with the first example of implementation (FIG. 5), the values of the sums, measured in zones 1 and 2, are close. This configuration is also useful for other applications where the acoustic wave is of sufficient power to achieve a sufficient acousto-optical conversion efficiency. The signal associated with the acoustic component can then be greater than the speckle decorrelation noise.
- FIG. 8 represents another generation device used to implement the method according to the invention in the particular case of the second example of FIG. 7.
- the EMI emission wave of wavelength ⁇ , emitted by the LAS laser, is intercepted by an AM amplitude modulation device.
- This device generates a carrier wave POR, of frequency f ⁇ , and two lateral bands modulated in amplitude LATMOD and LATMOD ', of frequency f R.
- These three waves are applied to a semi-transparent slide, which transmits part of each of these waves, applied to the object to be imaged OBJ.
- the transmitted part of the carrier wave constitutes the incident wave INC.
- the semi-transparent plate reflects a part of each of these waves towards the detection device, the reflected part of LATMOD constituting the reference wave REF.
- This device is only suitable for the second embodiment, where no spatial filtering device is used, because in the case of a lateral intensity modulation band, spatial filtering does not allow the different terms d 'interference.
- FIG. 9 describes a detail of a third embodiment of the present invention and of the spatial filtering device.
- the reference wave REF is no longer a plane wave, but a spherical wave of frequency f R.
- a spherical reference wave can for example be obtained from the reference wave plane generated by a GEN generation device previously described, by focusing the plane reference wave, using a lens 5, on a small mirror 4 situated for example in the plane of the diaphragm 2.
- the reference wave REF can also arrive at the mirror 4 at an angle ⁇ ⁇ so that it is reflected and arrives at the detection device DET by forming an angle ⁇ ⁇ with the signal wave SIG.
- a converging lens 3 is not necessarily used to collimate the signal wave in the direction of the DET detector, in fact, the divergent nature of the reference wave fulfills an analogous role.
- the diaphragm 2 can be removed from the sample holder of the object to be imaged OBJ, and placed between the tank and the DET detection device, or possibly fix it on the downstream face of the tank 1.
- This arrangement can be advantageous if the acoustic coupling between the transducer TRANS, of acoustic frequency f A , and the object to be imaged OBJ is produced by a tank filled with water 1, and this latter is located on the light path traveled by the REF reference wave before reaching the mirror 4. (This arrangement is also valid for the other embodiments where a diaphragm is used.)
- FIG. 10 represents the diaphragm 2 provided with the mirror 4, viewed from the DET detection device.
- the diaphragm 2 has a slot, for example central, of width Y and height X.
- a mirror 4 for example circular, is placed at mid-height of the slot.
- the mirror 4 is moreover laterally offset with respect to the slot of the diaphragm 2. This lateral offset is linked to the offset of zones 2 and 3 of FIG. 6 that one seeks to achieve, once the calculations have been made by the processing device CALC.
- zones 2 are obtained. and 3 of Figure 6 juxtaposed, but not overlapping.
- a mirror 4 of dimensions such that the mirror does not encroach on the slot of the diaphragm 2.
- This embodiment also makes it easy to find an optimal position of the DET detector making it possible to obtain good quality information for the point studied (U, V, W) of the object to be imaged OBJ. Indeed, by increasing L, that is to say by moving the detection device DET away from the diaphragm 2, the angle between the signal wave SIG and the reference wave REF decreases, so that the condition of "Aliasing" is better respected.
- the optimal positioning of the detector is achieved independently of the relative positioning of the zones 2 and 3 of FIG. 6, which is itself achieved by the adequate placement of the focal point of the reference wave (center of the mirror 4 on the diaphragm 2).
- digital information has been obtained relating to the measurement point, of coordinates (U, V, W) of the object (in the case of demodulation with N phases) or relating to each point of the interval ([U-Dx, U + Dx], V, W) of the points of the object (in the case of "frequency chirping" or other analogous method), that is to say a point information or 1D.
- the displacement of the position of the focal point can be obtained, either by moving the transducer (in the x, y or z direction considered) while maintaining the acoustic coupling between the transducer and the object to be imaged, or by using several transducers of different focal points, for example.
- the spatial filtering device COL if one is used
- the DET detector or even the device used to make the reference wave interfere with the detector, and all or part of the GEN generation device jointly to the displacement of the position of the focal point ie of the coordinate measuring point (U, V, W).
- any device according to the invention can also be coupled to a conventional acoustic imaging device.
- the coupling of these two devices thus makes it possible to obtain the object to imaging OBJ purely acoustic information supplied by the acoustic transducer by a conventional ultrasound imaging technique, and optical information supplied by the device according to the invention.
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Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04720896A EP1604248A2 (fr) | 2003-03-19 | 2004-03-16 | Procede et installation d imagerie acousto-optique |
JP2006505731A JP4679507B2 (ja) | 2003-03-19 | 2004-03-16 | 音響光学撮像方法および音響光学撮像装置 |
US10/549,511 US7623285B2 (en) | 2003-03-19 | 2004-03-16 | Method and device for opto-acoustical imagery |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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FR0303341A FR2852700B1 (fr) | 2003-03-19 | 2003-03-19 | Procede et installation d'imagerie acousto-optique. |
FR03/03341 | 2003-03-19 |
Publications (2)
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WO2004085978A2 true WO2004085978A2 (fr) | 2004-10-07 |
WO2004085978A3 WO2004085978A3 (fr) | 2004-11-04 |
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PCT/FR2004/000640 WO2004085978A2 (fr) | 2003-03-19 | 2004-03-16 | Procede et installation d'imagerie acousto-optique |
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US (1) | US7623285B2 (fr) |
EP (1) | EP1604248A2 (fr) |
JP (1) | JP4679507B2 (fr) |
FR (1) | FR2852700B1 (fr) |
WO (1) | WO2004085978A2 (fr) |
Families Citing this family (16)
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JP5132228B2 (ja) * | 2007-09-12 | 2013-01-30 | キヤノン株式会社 | 測定方法及び測定装置 |
JP5171564B2 (ja) * | 2008-11-14 | 2013-03-27 | キヤノン株式会社 | 音響光学トモグラフィー測定装置および測定方法 |
WO2010143572A1 (fr) * | 2009-06-12 | 2010-12-16 | オリンパス株式会社 | Dispositif et méthode d'analyse d'informations sur un sujet |
US8391943B2 (en) | 2010-03-31 | 2013-03-05 | Covidien Lp | Multi-wavelength photon density wave system using an optical switch |
US9232896B2 (en) | 2012-09-20 | 2016-01-12 | Elwha Llc | Focusing electromagnetic radiation within a turbid medium using ultrasonic modulation |
US8917442B2 (en) | 2012-09-20 | 2014-12-23 | Elwha Llc | Focusing electromagnetic radiation within a turbid medium using ultrasonic modulation |
EP4194801A1 (fr) | 2015-02-24 | 2023-06-14 | The University of Tokyo | Dispositif d'imagerie dynamique à haute sensibilité et procédé d'imagerie |
CN108351289B (zh) | 2015-10-28 | 2021-11-26 | 国立大学法人东京大学 | 分析装置 |
WO2018034241A1 (fr) | 2016-08-15 | 2018-02-22 | 国立大学法人大阪大学 | Dispositif de génération de phase/d'amplitude d'onde électromagnétique, procédé de génération de phase/d'amplitude d'onde électromagnétique, et programme de génération de phase/d'amplitude d'onde électromagnétique |
RU170388U1 (ru) * | 2016-09-14 | 2017-04-24 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Сибирский государственный университет геосистем и технологий" (СГУГиТ) | Оптико-акустический приемник |
CN109931229B (zh) * | 2017-12-18 | 2020-10-30 | 北京金风科创风电设备有限公司 | 用于风力发电机组的涡激振动的监测方法和设备 |
WO2019241443A1 (fr) | 2018-06-13 | 2019-12-19 | Thinkcyte Inc. | Méthodes et systèmes de cytométrie |
CN111435528A (zh) * | 2019-01-15 | 2020-07-21 | 中国科学院金属研究所 | 激光超声可视化图像质量提升处理方法 |
CN109927401A (zh) * | 2019-01-31 | 2019-06-25 | 中国科学院西安光学精密机械研究所 | 一种高精度印刷机双光路机器视觉装置 |
CN110133879B (zh) * | 2019-04-25 | 2022-12-09 | 福建师范大学 | 一种提高超声调制光成像深度的装置和方法 |
CN114978367B (zh) * | 2022-05-09 | 2023-02-03 | 中国农业大学 | 一种实现射频功率和能量分布可视化的检测装置及方法 |
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US5313315A (en) * | 1992-05-06 | 1994-05-17 | University Of Southern California | Method of imaging through a scattering medium using coherent light |
FR2774887A1 (fr) * | 1998-02-13 | 1999-08-20 | Centre Nat Rech Scient | Capteur optique sur substrat de silicium et application a la mesure in situ d'un marqueur fluorescent dans les petites bronches |
US6401540B1 (en) * | 2000-02-29 | 2002-06-11 | Bechtel Bwxt Idaho, Llc | Method and apparatus for detecting internal structures of bulk objects using acoustic imaging |
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FR2395534A1 (fr) * | 1977-06-24 | 1979-01-19 | Thomson Csf | Dispositif d'imagerie acousto-optique a detection holographique coherente en temps reel |
US4696061A (en) * | 1983-12-28 | 1987-09-22 | Sperry Corporation | Acousto-optic R-F receiver which is tunable and has adjustable bandwidth |
FR2617602B1 (fr) | 1987-07-03 | 1989-10-20 | Thomson Csf | Procede et systeme d'imagerie par transillumination a marquage en frequence des photons |
FR2664048B1 (fr) | 1990-06-29 | 1993-08-20 | Centre Nat Rech Scient | Procede et dispositif de detection analogique multicanal. |
US5684588A (en) * | 1996-10-04 | 1997-11-04 | United States Of America As Represented By The Secretary Of The Air Force | Homodyne and hetrodyne imaging in a light scattering medium |
JP2000088743A (ja) * | 1998-09-17 | 2000-03-31 | Aloka Co Ltd | 光計測装置 |
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-
2004
- 2004-03-16 WO PCT/FR2004/000640 patent/WO2004085978A2/fr active Application Filing
- 2004-03-16 EP EP04720896A patent/EP1604248A2/fr not_active Withdrawn
- 2004-03-16 US US10/549,511 patent/US7623285B2/en not_active Expired - Fee Related
- 2004-03-16 JP JP2006505731A patent/JP4679507B2/ja not_active Expired - Fee Related
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US3772457A (en) * | 1971-03-29 | 1973-11-13 | American Express Invest | Sonic image transducer using a storage camera |
US5313315A (en) * | 1992-05-06 | 1994-05-17 | University Of Southern California | Method of imaging through a scattering medium using coherent light |
FR2774887A1 (fr) * | 1998-02-13 | 1999-08-20 | Centre Nat Rech Scient | Capteur optique sur substrat de silicium et application a la mesure in situ d'un marqueur fluorescent dans les petites bronches |
US6401540B1 (en) * | 2000-02-29 | 2002-06-11 | Bechtel Bwxt Idaho, Llc | Method and apparatus for detecting internal structures of bulk objects using acoustic imaging |
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Also Published As
Publication number | Publication date |
---|---|
US20070151343A1 (en) | 2007-07-05 |
WO2004085978A3 (fr) | 2004-11-04 |
US7623285B2 (en) | 2009-11-24 |
JP4679507B2 (ja) | 2011-04-27 |
FR2852700A1 (fr) | 2004-09-24 |
FR2852700B1 (fr) | 2005-09-23 |
JP2006520893A (ja) | 2006-09-14 |
EP1604248A2 (fr) | 2005-12-14 |
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