WO2005032360A1 - Interferometre a trajets de reference multiples et procede de spectroscopie - Google Patents

Interferometre a trajets de reference multiples et procede de spectroscopie Download PDF

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Publication number
WO2005032360A1
WO2005032360A1 PCT/IB2004/003342 IB2004003342W WO2005032360A1 WO 2005032360 A1 WO2005032360 A1 WO 2005032360A1 IB 2004003342 W IB2004003342 W IB 2004003342W WO 2005032360 A1 WO2005032360 A1 WO 2005032360A1
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Prior art keywords
electromagnetic radiation
different
interferometer
optical paths
target medium
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PCT/IB2004/003342
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English (en)
Inventor
Maurice Christian Gerard Aalders
Dirk Johannes Faber
Antonius Gerardus Johannes Maria Van Leewen
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Academisch Medisch Centrum
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Publication of WO2005032360A1 publication Critical patent/WO2005032360A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/41—Detecting, measuring or recording for evaluating the immune or lymphatic systems
    • A61B5/413—Monitoring transplanted tissue or organ, e.g. for possible rejection reactions after a transplant
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0073—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by tomography, i.e. reconstruction of 3D images from 2D projections
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/45—Interferometric spectrometry
    • G01J3/453—Interferometric spectrometry by correlation of the amplitudes
    • 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
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3563—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
    • 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
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
    • A61B2562/0233—Special features of optical sensors or probes classified in A61B5/00
    • A61B2562/0242—Special features of optical sensors or probes classified in A61B5/00 for varying or adjusting the optical path length in the tissue
    • 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
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
    • G01N2021/3144—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths for oxymetry
    • 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
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
    • G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
    • G01N2021/451—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods for determining the optical absorption
    • 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
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/359—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using near infrared light

Definitions

  • the present invention relates to an interferometer and to a spectral measurement apparatus utilising the interferometer, particularly, though not exclusively, for performing spectral analysis of a medium under investigation, for example, a body part, an organ, tissue or a fluid, such as measuring a chromophore level in vivo.
  • the present invention also relates0 to a method of spectral analysis for an interferometric measurement apparatus and to a selectable optical path length provision apparatus for use in the above.
  • concentrations of chromophores in a medium can be determined by measuring spectral attenuation of light after propagation over a known distance through the medium and then applying Beer's law of extinction.
  • a quantitative interpretation of chromophore extinction depends upon a knowledge of the propagation distance or path length of the light in the tissue.
  • three techniques are commonly used to estimate the path length.
  • a first technique employs a theoretical model, such as a diffusion approximation to solve a so-called "radiative transport equation" used to predict fluence rates.
  • a condition of the transport equation to be valid is that the light being used has to be totally diffuse, the condition being violated close to a source of the light. Consequently, due to such a limitation, this technique is only used where a relatively large distance can be attained between the tissue and the source of the light.
  • a second technique involves measuring a time taken for the light to propagate over the path length.
  • a third technique involves making phase resolved measurements of the light. Due to practical limitations, both the second and third techniques also require a large distance between the source of the light and the detector. Additionally, inhomogeneities and multiple layers of a volume to be probed result in measurement errors, because most techniques for determining the path length are based upon an assumption that the volume to be probed is a semi-infinite, homogenous medium.
  • an interferometer comprising a source of multiwavelength electromagnetic radiation, a beam splitter, a sensor arm comprising a probe for collecting multiwavelength electromagnetic radiation back-scattered from a target medium, a reference arm comprising an array including a plurality of elements providing at least two different optical paths having different optical lengths, the reference arm further comprising a discriminating device for imparting a discriminating characteristic to the multiwavelength electromagnetic radiation passing along the at least two different optical paths that can discriminate between them, and a detector for receiving multiwavelength electromagnetic radiation reflected from the array and having the discriminating characteristic and for receiving the multiwavelength electromagnetic radiation back-scattered from the target medium; wherein the source, the array, the detector, the probe and the beam splitter are arranged as an interferometer.
  • the array preferably comprises a plurality of reflective elements providing a plurality of optical paths of different optical lengths.
  • the array includes a substrate tilted at an angle to an incident optical path of the reference arm.
  • the reflective elements may comprise mirrors or may comprise lines of a diffraction grating.
  • the discriminating characteristic imparted to the multiwavelength electromagnetic radiation comprises amplitude modulation.
  • the discriminating device comprises a pixelated device arranged to permit selective transmission of electromagnetic radiation therethrough, wherein different pixels can be arranged to permit and prevent transmission at different frequencies, whereby the electromagnetic radiation passing along the at least two different optical paths is amplitude modulated at different frequencies.
  • the discriminating device comprises a micromechanical electronic system for independently rotating each of the mirrors of the array wherein different mirrors can be arranged to reflect the electromagnetic radiation back into the reference arm or away from the reference arm at different frequencies, whereby the electromagnetic radiation passing along the at least two different optical paths is amplitude modulated at different frequencies.
  • the discriminating characteristic imparted to the multiwavelength electromagnetic radiation may comprise phase modulation.
  • the discriminating device comprises a pixelated device arranged to provide selective phase shift of electromagnetic radiation passing therethrough, wherein different pixels can be arranged to provide different phase shifts, whereby the electromagnetic radiation passing along the at least two different optical paths is phase modulated with different frequencies.
  • the discriminating device may comprise a mechanism for independently vibrating each of the mirrors of the array thereby providing slight variations in optical path length generating phase shift in reflected electromagnetic radiation, wherein different mirrors can be arranged to be vibrated at different frequencies, whereby the electromagnetic radiation passing along the at least two different optical paths is phase modulated at different frequencies.
  • the pixelated device comprises a Spatial Light Modulator (SLM).
  • SLM Spatial Light Modulator
  • the source of multiwavelength electromagnetic radiation may be a low coherence source of electromagnetic radiation. More preferably, the source of multiwavelength electromagnetic radiation may be any one of the following: a Titanium-Sapphire laser; a superluminescent diode; a Light Emitting Diode (LED); or a lightbulb.
  • the interferometer may be a Michelson Interferometer or a Mach-Zehnder Interferometer.
  • the sensor arm includes an optical path provided by an optical fibre.
  • the probe further comprises a focussing element located adjacent an end of the optical path of the sensor arm for launching electromagnetic radiation into and receiving electromagnetic radiation from the target medium.
  • the reference arm includes an optical path provided by an optical fibre.
  • the invention provides an interferometric spectral measurement apparatus comprising the interferometer as described above and a spectral analyser coupled to the detector.
  • the spectrum analyser comprises an input for receiving a signal from the detector and a processing unit arranged to calculate a spectrum for the signal from the detector.
  • each of the at least two different optical paths corresponds to a different depth in the target medium and the processing unit is arranged to discriminate between data in the signal relating to the at least two different optical paths and to calculate a spectrum in respect of each.
  • the processing unit may preferably be further arranged to calculate a concentration of a constituent of the target medium based on the calculated spectra.
  • the invention provides a method of spectral analysis of a target medium, the method comprising the steps of receiving a detector signal including spectral data relating to at least two different depths in the target medium, discriminating between the spectral data relating to the at least two different depths in the target medium, the discrimination being based on differences in a discrimination characteristic imparted to electromagnetic radiation travelling along at least two different optical paths having different lengths in a reference arm of a interferometer; and calculating a spectrum for each of the at least two depths from the spectral data.
  • the method preferably further comprises the step of calculating a concentration of a constituent of the target medium based on the calculated spectra.
  • the constituent is preferably a chromophore.
  • the concentration is preferably calculated using knowledge of a predetermined wavelength of the electromagnetic radiation, a spectral molar extinction coefficient at the wavelength, and a difference between the two different depths.
  • the method of spectral analysis of a target medium described above preferably utilises the interferometric spectral measurement apparatus of described above.
  • the invention provides a selectable optical path length provision apparatus comprising an array including a plurality of reflective elements arranged at different distances from a common optical path thereby providing a plurality of optical paths of different lengths and a controller for controlling selection of the plurality of optical paths to permit or prevent retro-reflection ofelectromagnetic radiation from a corresponding reflective element along the selected path.
  • the apparatus comprises a pixelated device arranged to permit selective transmission of electromagnetic radiation therethrough and the controller controls the pixelated device to permit and prevent transmission of electromagnetic radiation through selected pixels.
  • the controller controls the pixelated device to permit and prevent transmission of electromagnetic radiation through selected pixels at different frequencies, whereby the electromagnetic radiation passing along different optical paths is amplitude modulated at different frequencies.
  • the pixelated device comprises a Spatial Light Modulator (SLM).
  • SLM Spatial Light Modulator
  • the apparatus comprises a micromechanical electronic system for independently rotating each of the reflective elements of the array wherein different reflective elements can be arranged to reflect the electromagnetic radiation back into the common optical path.
  • the controller controls the micromechanical electronic system for independently rotating each of the reflective elements of the array wherein different reflective elements can be arranged to reflect the electromagnetic radiation back into the common optical path or away from the common optical path at different frequencies, whereby the electromagnetic radiation passing along the at least two different optical paths is amplitude modulated at different frequencies.
  • the array may be formed by a diffraction grating, which is, preferably, blazed.
  • the apparatus is portable and convenient to use as well as being able to provide short response times for measurements. Additionally, use of the apparatus is painless and non-invasive. Over a period of time the overall cost of making measurements is less than conventional invasive techniques. Furthermore, in this arrangement, data from different depths can be acquired simultaneously and discriminated at the processing stage.
  • Figure 1 is a schematic diagram of an apparatus constituting an embodiment of the invention
  • Figure 2 is a graph of absorption windows for wavelengths of electromagnetic radiation in respect of media making-up the human body;
  • Figure 3 is a schematic diagram of a probe for use with the apparatus of
  • Figure 4 is a schematic diagram of a first alternative reflective surface arrangement for use with the apparatus of Figure 1 ;
  • Figure 5 is a schematic diagram of a second alternative reflective arrangement for use with the apparatus of Figure 1 ;
  • Figure 6 is a schematic diagram of a third alternative reflective arrangement for use with the apparatus of Figure 1 ;
  • Figure 7 is a flow diagram of a method of spectral analysis and chromophore measurement for the apparatus of Figure 1 ;
  • Figure 8 is a schematic diagram of tissue and associated spectra at predetermined depths;
  • Figure 9 is a graph of an absorption spectrum and associated absorption spectra components.
  • an interferometric spectral analysis apparatus 100 comprises a source of low-coherence light 102, for example a superluminescent diode, a Titanium:Sapphire laser, an LED or a lightbulb. Due to the high absorption of some compounds found in the human body, such as blood and water (see Figure 2), the bandwidth of electromagnetic radiation emitted by the source of light 102 has to be sufficiently broad to distinguish between different chromophores, as well as reduce coherence length in order to increase axial resolution of the apparatus.
  • a source of low-coherence light 102 for example a superluminescent diode, a Titanium:Sapphire laser, an LED or a lightbulb. Due to the high absorption of some compounds found in the human body, such as blood and water (see Figure 2), the bandwidth of electromagnetic radiation emitted by the source of light 102 has to be sufficiently broad to distinguish between different chromophores, as well as reduce coherence length in order to increase axial resolution of the apparatus.
  • the source of light 102 is optically coupled to a beam splitter 104, for example a 50:50 splitter, by a first optical fibre 106.
  • the beam splitter 104 is also optically coupled to a reference arrangement 108 by a second optical fibre 110, a detector, for example a photodiode 112, by a third optical fibre 114, and a probe 116 by a fourth optical fibre 118.
  • the photodiode 112 is electrically coupled to a suitable interface card (not shown) fitted within a Personal Computer (PC) 120 capable of executing spectral analysis software, the operation of which will be described in greater detail later herein.
  • PC Personal Computer
  • the source of light 102, the beam splitter 104, the photodiode 112 and the probe 116 are arranged to form a Michelson Interferometer.
  • suitable interferometer arrangements can be employed, for example, a Mach- Zehnder Interferometer arrangement.
  • the probe 116 is, in use, disposed adjacent a medium 122 to be analysed, for example, a human body part, such as an arm.
  • the probe 116 comprises a housing 300 including a reflective surface, for example a prism 302 at a first distal end thereof.
  • a port 304 permits disposal of an end of the fourth optical fibre 118 into the housing 300 at a second proximal end thereof, where the end of the fourth optical fibre 118 is fixed in a predetermined position.
  • a first, collimating, lens 306 is disposed adjacent the end of the fourth optical fibre 1 8 and a second, focussing, lens 308 is disposed between the first lens 306 and the prism 302.
  • the reference arrangement 108 is capable of selectively providing at least two optical paths having different optical path lengths between the beam splitter 104 and the reference arrangement 108.
  • the reference arrangement includes a reflective arrangement 124 tilted at an angle to the optical path so that light incident and reflected off different parts of the reflective arrangement has different optical path lengths to travel.
  • the reference arrangement 108 also includes a mechanism 126, which, as will be more fully described below, provides a mechanism for selecting light incident and reflected off different parts of the reflective arrangement and for imparting a discriminating characteristic to the light.
  • the reference arrangement 108 comprises a third, collimating, lens 400 disposed adjacent the second optical fibre 110, a Spatial Light Modulator (SLM) 402 being disposed adjacent the third lens 400.
  • SLM Spatial Light Modulator
  • a blazed diffraction grating 404 is located a predetermined distance from the SLM 402, the grating 404 being disposed in angular relation to the SLM 402 so that each groove of the grating 404 has a different optical path length with respect to the SLM 402.
  • the position of the grating 404 is such that light incident upon the grating 404 is reflected back along a line substantially perpendicular to the plane of the SLM 402.
  • the SLM 402 and diffraction grating 404 are replaced by a Microelectromechanical System (MEMS) mirror array 500 disposed a predetermined distance from the third lens 400 and in a like angular relation to the lens 400 as the grating 404 is to the SLM 402 of the previous arrangement ( Figure 4).
  • MEMS Microelectromechanical System
  • the position of the mirror array 500 is such that light incident upon a mirror element of the mirror array 500 can be reflected back along a line substantially perpendicular to a central plane of the third lens 400.
  • the MEMS mirror array 500 is replaced by another mirror array 502 in which a plurality of mirrors are provided mounted on piezoelectric devices 506 of different lengths.
  • a controller 504 is used to control the piezoelectric devices, as will be explained more fully below.
  • the apparatus 100 is powered-up and the reference arrangement 108 set (step 600) to provide at least two interferometer path lengths, i x and £ 2 , corresponding to first and second depths of interest, di and d 2 , within the medium 122 to be analysed.
  • the arrangement of Figure 4 two or more strips of pixels of the SLM 402 are chosen to permit light to propagate through the strips (the remaining pixels remaining opaque), be retro-reflected by an aligned groove of the grating 404 through the SLM 402 for launch into the second optical fibre 110 by the third lens 400.
  • two or more strips of mirror elements of the mirror array 500 are chosen to retero-reflect light incident upon the strips of mirror elements through the third lens 400 for launch into the second optical fibre 110.
  • remaining mirror elements of the mirror array 500 are controlled to reflect incident light away from the third lens 400.
  • the light in the two (or more) path lengths, l x and l 2 is amplitude modulated at different frequencies by either modulating the chosen strips of pixel(s) of the SLM so that the pixels change from transparent to opaque modes at a respective frequency, or modulating the movement of the chosen sets of mirror element(s) so that the incident light is retero-reflected through the third lens 400 for launch into the second optical fibre 110, or not, at the respective frequency.
  • light in the reference arm of the interferometer corresponding to at least two depths, is amplitude modulated prior to incidence upon the photodetector 112. Therefore, the incident light is modulation "encoded" so that light corresponding to a desired depth of interest can be selected by the PC 120 by demodulation using a frequency corresponding to the desired depth of interest.
  • the photodetector 112 In response to the incidence of light thereupon, the photodetector 112 generates electrical signals that are received by the PC 120.
  • the electrical signals received by the PC 120 are pre-processed by the interface card, for example, sampled and the software executed by the PC 120 analyses the pre-processed electrical signal and isolates (step 602) a first interference envelope and phase corresponding to the interference of light reflected by the reference arrangement 108 and light back-scattered from the medium 122 at the first depth of interest, d-
  • the PC 120 then performs (step 604) a Fast Fourier Transform (FFT) on the first isolated interference envelope in order to obtain a first spectrum 700 ( Figure 8) for the first interference envelope.
  • FFT Fast Fourier Transform
  • the first spectrum is then stored for subsequent use (step 606).
  • the PC 120 isolates (step 610) a second interference envelope and phase in the electrical signals corresponding to the interference of light reflected by the reference arrangement 108 and light back-scattered from the medium 122 at the second depth of interest, d 2 .
  • the PC 120 then performs (step 612) a further FFT on the second isolated interference envelope in order to obtain a second spectrum 702 ( Figure 8) for the second interference envelope.
  • signals corresponding to the first and second depths of interest di, d 2 are encoded, sampled simultaneously and subsequently decoded prior to performance of the FFTs to obtain the corresponding first and second spectra 700, 702.
  • the second spectrum is then stored (step 614) and an in-medium path length, p, travelled by the light in the medium 122 between the first and second depths of interest d ⁇ d 2 is calculated (step 616) by selecting depths based upon the first and second path lengths £ x , £ 2 and making respective corrections to account of the difference in refractive indices between the medium (122) and air.
  • the data obtained in relation to the first and second spectra 700, 702 is used to calculate a property of the medium 122 by employing the following version of the Lambert-Beer law of spectral extinction:
  • lo is the intensity of the optical signal at wavelength, ⁇ for the first depth of interest, d ⁇ ; I is the intensity of the optical signal at the wavelength, ⁇ for the second depth of interest, d 2 ; Cj is a concentration of a chromophore i; s is a spectral extinction coefficient for the chromophore i at the wavelength, ⁇ ; and p is the in-medium path length travelled by the light in the medium 122.
  • the given spectrum comprises a number of extinction components, each having a peak at a certain wavelength. Consequently, the calculation is only carried out in relation to the peak wavelength corresponding to the chromophore of interest. Therefore, in relation to bilirubin, the concentration of the chromophore i is thus calculated (step 618) by the PC 120 for the known wavelength using knowledge of the spectral extinction coefficient, ⁇ ⁇ ( ⁇ ), the path length, p, and the intensities of the optical signals lo, I, in order to calculate.
  • phase modulation at different frequencies of modulation could be used. This could be carried out using the apparatus described above with reference to Figure 4.
  • the SLM 402 is used to shift the phase of light passing through particular pixels. Again, particular strips of pixels are chosen so as to provide particular chosen path lengths to and from the diffraction grating 404, so as to correspond to particular desired depths in the medium 122. The remaining pixels are controlled to be opaque. In this embodiment, the chosen strips of pixels are controlled so as to phase shift the light transmitted therethrough by varying amounts at a predetermined frequency.
  • the PC can discriminate between the different depths by discriminating between light whose phase is modulated at the particular frequency. It will, of course, be appreciated, that such phase modulation could be carried out in addition to amplitude modulation, for example, by utilising the SLM 402 as described above in conjunction with the mirror array 500 of Figure 5.
  • the controller 504 is used to control the mirror array 502.
  • Each piezoelectric device 506 is of a different length, so that the mirrors mounted on the ends provide different optical path lengths for the light incident thereon.
  • the controller 504 controls the different chosen mirrors to vibrate (by controlling the piezo electric devices 506) at different particular frequencies. The vibration of the mirrors along the optical path axis causes the optical path length to change slightly and, consequently, to provide a phase shift in the reflected light.
  • the PC can thus discriminate between different depths by choosing particular frequencies of phase modulation.
  • the particular mirrors could be chosen (instead of using an SLM), by the technique of Figure 5, by having the mirrors capable of partial rotation, or tilting, so that some mirrors are orientated to reflect light back to the lens 400, and other mirrors are orientated to reflect the light away from the lens 400.
  • the apparatus and method described above can be employed in the field of obstetrics to make brain oxygenation measurements of a newborn during delivery.
  • perfusion measurements can be made to monitor viability of tissue before and after organ transplantation and, in relation to oncology, the apparatus can be used for tissue characterization to discriminate healthy from pathologic tissue based on differences in optical properties.
  • optical properties of all tissue types can be measured to obtain knowledge of optical properties of tissues as a prerequisite for the development of optical diagnostic and therapeutic techniques, and in the field of pharmacology the apparatus and method can be used to monitor the distribution and accumulation of drugs at a target site within the body if the drugs have a specific extinction spectrum or can be marked with an absorber.
  • retinal vessel oxymetry can be performed as well as glucose measurements.
  • the apparatus and method permits quality assessment of fruits and vegetables.
  • the internal quality, change in quality and composition of fruits can be measured in real time and non-destructively by using visible and NIR (Near-Infrared) spectra, for example, to estimate the water content, sugar level, Brix values (which indicates sweetness of fruit), amount of soluble solids, such as apples, pineapples, peaches, vegetables and tomatoes.
  • visible and NIR Near-Infrared
  • non-destructive testing and microanalysis for the diagnostics and conservation of cultural and environmental heritage artefacts can be performed.
  • the apparatus and method can be used to assess the composition of layers of paint and ink, the different pigments, and a protective layer for authentication and/or restoration purposes.
  • the interferometric device can be used to discriminate between different light paths of different optical lengths without specifically carrying out spectrum analysis.
  • Alternative embodiments of the invention can be implemented as a computer program product for use with a computer system, the computer program product being, for example, a series of computer instructions stored on a tangible data recording medium, such as a diskette, CD-ROM, ROM, or fixed disk, or embodied in a computer data signal, the signal being transmitted over a tangible medium or a wireless medium, for example microwave or infrared.
  • the series of computer instructions can constitute all or part of the functionality described above, and can also be stored in any memory device, volatile or non-volatile, such as semiconductor, magnetic, optical or other memory device.
  • references to "light” herein refer to electromagnetic radiation of wavelengths between about 300nm and about 10 ⁇ m, preferably between about 400nm and about 2 ⁇ m, and very preferably between about 800nm and about 1700nm.

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Abstract

Un interféromètre (100) permet l'acquisition simultanée de données spectrales à partir de différentes profondeurs d'un objet. Dans cet interféromètre, un bras de référence (108) comporte un réseau d'éléments réfléchissants ménageant au moins deux trajets optiques différents de longueurs optiques différentes. Le bras de référence comporte en outre un dispositif de discrimination permettant d'appliquer une caractéristique de discrimination au rayonnement passant par les différents trajets optiques. Le dispositif de discrimination est de préférence un modulateur spatial de lumière (SLM) qui autorise des modulations d'amplitude ou de phase différentes pour les différents trajets optiques. Un interféromètre est couplé à un analyseur de spectre (120), et les données obtenues par cet appareil sont utilisées pour calculer une concentration d'un chromophore à étudier.
PCT/IB2004/003342 2003-10-01 2004-10-01 Interferometre a trajets de reference multiples et procede de spectroscopie WO2005032360A1 (fr)

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DE102007023293B3 (de) * 2007-05-16 2008-09-25 Universität Zu Lübeck Verfahren zur Optischen Kohärenztomographie
DE102009053006A1 (de) * 2009-11-16 2011-05-19 Bundesrepublik Deutschland, vertr.d.d. Bundesministerium für Wirtschaft und Technologie, d.vertr.d.d. Präsidenten der Physikalisch-Technischen Bundesanstalt Längenmessgerät
WO2019198991A1 (fr) * 2018-04-12 2019-10-17 삼성전자 주식회사 Procédé de détection d'informations biométriques utilisant un modulateur spatial de lumière, dispositif électronique et support de stockage

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DE102005039021A1 (de) * 2005-06-14 2006-12-21 Klews, Peter-Michael, Dr. Nicht-invasives quantitatives Blutinhaltsstoffanalysegerät
DE102007023293B3 (de) * 2007-05-16 2008-09-25 Universität Zu Lübeck Verfahren zur Optischen Kohärenztomographie
DE102009053006A1 (de) * 2009-11-16 2011-05-19 Bundesrepublik Deutschland, vertr.d.d. Bundesministerium für Wirtschaft und Technologie, d.vertr.d.d. Präsidenten der Physikalisch-Technischen Bundesanstalt Längenmessgerät
DE102009053006B4 (de) * 2009-11-16 2014-04-24 Bundesrepublik Deutschland, vertr.d.d. Bundesministerium für Wirtschaft und Technologie, d.vertr.d.d. Präsidenten der Physikalisch-Technischen Bundesanstalt Längenmessgerät
WO2019198991A1 (fr) * 2018-04-12 2019-10-17 삼성전자 주식회사 Procédé de détection d'informations biométriques utilisant un modulateur spatial de lumière, dispositif électronique et support de stockage
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