Patent Description:
To detect and to determine different substances is highly desired in a large variety of applications ranging from chemical analysis to in-field determination of potentially hazardous and toxic substances. In many situations correct determination of a substance is of utmost importance.

For instance, to be able to determine if a substance is hazardous, e.g. explosive, or not is critical since a wrongful determination may result in severe consequences potentially with personnel injuries and material losses. Similarly, it may also be critical to determine if a substance is toxic or not since a wrongful determination may result in serious consequences involving personnel and environmental risks. Further, it is highly important to verify that a drug is correctly synthesized since a wrongfully synthesized drug may become harmful instead of curative for a subject.

When detecting and determining different substances different approaches may be used.

A common way used to investigate properties of a substance is to let the substance undergo a chemical analysis. A chemical analysis of a substance is often accurate but is typically suffering from complexity and the time required for the analysis. Moreover, chemical analysis often require that various further substances or analytes are used or involved in the analysis. Such analysis therefore tends to become costly and time consuming. Another drawback resides in that such analysis are generally too complicated and time consuming to be conducted under field conditions.

Another commonly used approach for detecting and determining different substances is to use some form of spectroscopic analysis. A common type of spectroscopy used in this case is optical spectroscopy where light having interacted with the substance in question is analyzed using a spectrometer. The light interacting with the substance is scattered by the substance resulting in that the scattered light is affected by the substance. Such scattering from a substance can either be elastic or in-elastic. In elastic scattering the photons of scattered light exhibit the same energy as the photons impinging on the substance at hand. In in-elastic scattering the photons of scattered light exhibit a different energy as compared to the photons impinging on the substance at hand. In-elastically scattered photons therefore either gain or lose energy.

Both elastically and in-elastically scattered photons may be used in spectroscopic analyses of substances. When looking at elastically scattered photons certain properties, such as color, of the substance may be determined. However, when it comes to determining a certain substance more sophisticated spectroscopic techniques also relying on in-elastically scattered photons are generally required.

Raman spectroscopy is a spectroscopic technique relying on inelastic scattering of photons, known as Raman scattering. In Raman spectroscopy a source of monochromatic light, usually from a laser, is used. The light source may emit light in the visible, near infrared, IR, or near ultraviolet, UV, range, although X-rays can also be used. The laser light interacts with molecular vibrations, phonons or other excitations in the molecular system, resulting in that the energy of the laser photons being shifted up or down in the in-elastically scattered light thereof. The shift in energy gives information about the vibrational modes in the molecular system at hand. In other words, in-elastically light scattered from the molecules of the substance at hand gives rise to a vibrational spectrum that includes of a series of lines or peaks constituting a molecular "fingerprint" for the substance. Hence a substance or material will give rise to a unique Raman spectrum, i.e. its "fingerprint". The unique Raman spectrum makes Raman spectroscopy suitable for identifying or determining substances or materials. In many fields of technology Raman spectroscopy is a well-established spectroscopic technique for rapid identifications of substances and chemicals with high degree of accuracy.

A typical Raman spectrum of a substance shows the shift of Raman wavelengths relative to elastically scattered light, typically referred to as Rayleigh-scattered light. The Rayleigh-scattered light has the same wavelength as the incident light of the light source whereas the Raman wavelengths are shifted up or down relative to the Rayleigh-scattered light. The vertical axis of a Raman spectrum typically represents the intensity of the Raman wavelengths and yields the concentration of the chemical components of the sample or substance, whereas the horizontal axis of a Raman spectrum typically represents the wavelength shift in relation to the Rayleigh light.

The light from Raman scattering is typically associated with weak intensities and may be difficult to observe without intense monochromatic excitation and a sensitive detector. Typically, <NUM> out of <NUM><NUM> - <NUM><NUM> photons scattered by a sample is a photon relating to a Raman wavelength. However, modern technical development of lasers, detectors, and optical components as well as continued miniaturization of electronic components have made it possible to produce fast and reliable portable Raman instruments which are suitable to use under field conditions.

Typically, a recorded Raman spectrum exhibits a plurality of intensity peaks characterizing a sample to be identified, i.e. the "fingerprint" of the sample. While this is true for most organic and some inorganic samples, there are exceptions for, e.g. molecules having certain symmetries. Such exceptional substances/molecules may yield a peak having an intensity dominating the intensity over remaining peaks in the corresponding Raman spectrum of the substance. This may thereby obscure identification of the substance, as the signal to noise ratio for smaller peaks is relatively small and sometimes difficult to distinguish. Hence, there is a need for an approach being capable of identifying samples having a large variation between characterizing Raman peaks. In other words, there is a need for an approach being capable of identifying samples having a large dynamic range between characterizing Raman peaks.

<CIT> discloses a method for identifying minerals and other materials. The method illuminates a mineral with monochromatic light for an illumination duration and collects scattered light using a Raman spectrometer detector. An aggregated or average Raman spectrum data is determined. True Raman spectrum data is determined by subtracting a blank spectrum. The true Raman spectrum data is compared to reference spectrums to identify the mineral or material.

<NPL> discloses a method for detection and classification of explosive substances in multi-spectral image sequences from imaging Raman spectroscopy using linear subspace matching. The disclosed approach uses limited spectral information and is computationally efficient. Thus, the approach enables fast screening of interesting spectra areas.

It is an object to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and at least partly solve the above-mentioned problem.

In view of the above, it is an object of the present invention to provide an improved method for identifying a set of candidate substances of a sample and an improved Raman spectroscopy device.

Another object is to provide such a method and Raman spectroscopy device which improves identification of samples having a large dynamic range between intensities of characterizing Raman peaks.

Another object is to provide such a method and Raman spectroscopy device which improves identification of different samples having similar Raman spectra.

To achieve at least one of the above objects and also other objects that will be evident from the following description, according to a first aspect of the invention, a method for identifying a set of candidate substances of a sample having the features defined in independent claim <NUM> is provided.

According to a second aspect of the invention, a Raman spectroscopy device is provided as defined with independent claim <NUM>. Furthermore, a computer program according to claim <NUM> is included, comprising instructions to cause the Raman spectroscopy device of claim <NUM> to execute the steps of the method of claim <NUM>. In addition, a non-transitory computer-readable storage medium according to claim <NUM>, having stored thereon the computer program of claim <NUM>, is included. Preferred variations to the inventive concept will be evident from the dependent claims.

According to the first aspect there is provided a method for identifying a set of candidate substances of a sample using a Raman spectroscopy device comprising a spectrometer, the method comprising setting an exposure time of the spectrometer, recording a Raman spectrum of the sample using the spectrometer being set to the exposure time, identifying a Raman peak having a largest intensity of at least one Raman peak of the Raman spectrum, determining a Raman shift of the identified Raman peak in the Raman spectrum, comparing the Raman shift against a database comprising entries correlating substances with information associated with Raman shifts of the substances, thereby identifying a set of candidate substances, wherein each candidate substance in the set of candidate substances has a Raman shift corresponding to the Raman shift, and reducing the set of candidate substances by setting a further exposure time of the spectrometer, the further exposure time being longer than the exposure time, recording a further Raman spectrum of the sample using the spectrometer being set to the further exposure time, identifying, while excluding wavelengths associated with all previously identified Raman peaks, a further Raman peak in the further Raman spectrum, the further Raman peak having a largest intensity of at least one Raman peak in the further Raman spectrum, determining a further Raman shift of the further Raman peak in the further Raman spectrum, comparing the further Raman shift against entries of the database corresponding to the candidate set of substances, thereby identifying a subset of candidate substances, wherein each candidate substance in the subset of candidate substances has a Raman shift corresponding to the further Raman shift, and excluding, from the set of candidate substances, candidate substances not forming part of the subset of candidate substances, thereby reducing the set of candidate substances.

Hereby an improved method for identifying a set of candidate substances of a sample is provided. Within the context of this disclosure, a "Raman shift of a Raman peak" should be construed as a wavelength difference between an excitation wavelength, i.e. the wavelength of Rayleigh-scattered light, and a wavelength of the Raman peak.

The words "substance" and "sample" are frequently used throughout this text. "Substance" is commonly known as a pure form of matter containing only one type of atoms or molecules. When referring to a "sample", an amount of matter, possibly comprising a compound of substances, is considered. A sample may consist of a single substance, thereby equating the words "sample" and "substance". Generally, a sample may comprise a plurality of different substances. The words sample and substance may however occasionally be used interchangeably, which should not confuse the skilled person.

The method may be a computer implemented method.

The "exposure time", "Raman spectrum", etc. may throughout this disclosure occasionally be denoted the "first exposure time"/"initial exposure time", "first Raman spectrum"/"initial Raman spectrum" in order to emphasize that these quantities refer to a first/initial recording. This since this disclosure refers to two or more exposure times, Raman spectra, etc..

Many types of light may be present upon detection of Raman signals. Herein, light of interest is preferably light scattered from the sample originating from a light source of the Raman spectroscopy device. Hence, any background light, noise, fluorescence contribution, or the like, may obscure detection of Raman signals. These types of light may, to a certain extent, be filtered out from scattered light of the sample before reaching a sensor of the Raman spectroscopy device. Remaining light reaching the sensor may be light corresponding to the Stokes band. Absolute wavelengths/wavenumbers of the so-called Stokes band depends on the wavelength of the light source of the Raman spectroscopy device, mentioned above in connection with the "Raman shift of a Raman peak".

The "exposure time" within this disclosure refers to a time period during which light, scattered from the sample, hits a sensor of the Raman spectroscopy device, i.e. corresponding to an exposure time of a normal digital camera.

The method may facilitate identifying a substance having a Raman peak having an intensity being significantly larger than remaining Raman peaks in the Raman spectrum of the sample.

By way of example, exposure times in question may lie in the range <NUM>-<NUM>. Recordings of a Raman spectra for samples comprising symmetric molecules resulting in relatively strong Raman signals may typically use exposure times in the range <NUM>-<NUM>. "Symmetric molecules" generally, and also herein, typically refers to the geometric space configuration of atoms of the molecule. Excitation of certain vibrational modes (by, e.g. a laser) of a molecule may affect the electron cloud of the molecule such that the molecules' interaction with light, e.g. reflectance or absorbance of photon energy, is affected. For a molecule having a certain symmetry, the symmetry property of the molecule may imply that specific vibrational modes of the molecule render a corresponding Raman spectrum having characterizing Raman peaks reflecting these specific vibrational modes. Another example is recording of substances comprising less symmetric molecules resulting in weaker Raman signals. Here exposure times may lie in the range <NUM>-<NUM>. The skilled person appreciates that any adequate exposure time may be used without departing from the scope of the claims. Hence, a sample may be adequately identified despite being a sample comprising symmetric molecules. Further, this may be done in a relatively speaking short time.

In practice, the wavelengths used in the Raman spectrum belong to the Stokes band of the Raman spectrum. In practice, however, there are always corresponding anti-Stokes peaks of a sample. At room temperature the anti-Stokes peaks are relatively small relative to the corresponding Stokes peaks, and are thereby usually not considered when analyzing a sample. However, it is appreciated that, within the scope of the claims, anti-Stokes peaks of a sample may be used.

The act of reducing the set of candidate substances may be repeated until the set of candidate substances is a single candidate substance, which is advantageous in that the sample may be identified. In other words, a substance or material of the sample may be identified.

The exposure time may be set such that the first Raman spectrum is within a dynamical range of an optical sensor of the spectrometer.

Should a Raman spectrum be recorded with an exposure time corresponding to pixels being overexposed (that is, portions of the Raman spectrum being outside the dynamical range of the optical sensor), "blooming" or other unbeneficial effects associated with overexposed pixels may be present. This may result in a less precise Raman shift of a Raman peak in the Raman spectrum. Hence, saturation of pixels of the sensor is preferably prevented in connection with the first Raman spectrum. The Raman shift of a Raman peak having the largest intensity in the Raman spectrum of a sample may thereby be determined with a relatively high accuracy.

The further exposure time may be set such that the intensity of at least one Raman peak of the further Raman spectrum exceeds a dynamical range of an optical sensor of the spectrometer.

Hence, less intense Raman peaks may be pronounced or appear which Raman peaks having a larger signal-to-noise ratio, SNR, compared to the same Raman peaks when using shorter exposure times. In other words, less intense Raman peaks may become detectable when using longer exposure times.

The Raman spectroscopy device may be a handheld Raman spectroscopy device.

Hence, flexibility is facilitated such that identification or matching of substances under field conditions may be possible.

The method may further comprise forming a compound Raman spectrum based on identified Raman peaks.

The compound Raman spectrum may be a spectrum comprising a first and a second Raman spectrum, captured using a first exposure time and a second exposure time, respectively, the first exposure time being shorter than the second exposure time. For instance, the compound Raman spectrum may comprise unsaturated Raman peaks of the second Raman spectrum while saturated Raman peaks may be replaced with a corresponding unsaturated Raman peak of the first Raman spectrum. Using the compound Raman spectrum may facilitate a direct identification of the substance against a database. This may be advantageous since all identified Raman peaks are clearly visible in the compound spectrum, and, to a certain extent, mutually comparable for a user. This may facilitate recognition of a sample for the user.

According to the second aspect there is provided a Raman spectroscopy device comprising a spectrometer, circuitry configured to execute an exposure time setting function configured to set an exposure time of the spectrometer, a recording function configured to record a Raman spectrum of the sample using the spectrometer being set to the exposure time, a Raman peak identifying function configured to identify a Raman peak having a largest intensity of at least one Raman peak of the Raman spectrum, a Raman shift determining function configured to identify a Raman shift of the identified Raman peak in the Raman spectrum, a Raman shift comparing function configured to compare the Raman shift against a database comprising entries correlating substances with information associated with Raman shifts of the substances, thereby identifying a set of candidate substances, wherein each candidate substance in the set of candidate substances has a Raman shift corresponding to the Raman shift, wherein the circuitry is further configured to reduce the set of candidate substances by executing a further exposure time setting function configured to set a further exposure time of the Raman spectroscopy device, the further exposure time being longer than the exposure time, a further Raman spectrum recording function configured to record a further Raman spectrum of the sample using the Raman spectroscopy device being set to the further exposure time, an identifying function configured to identify, while excluding wavelengths associated with identified Raman peaks, a further Raman peak in the further Raman spectrum, the further Raman peak having a largest intensity of Raman peaks in the further Raman spectrum, a further Raman shift determining function configured to determine a further Raman shift of the further Raman peak in the further Raman spectrum, a comparing function configured to compare the further Raman shift against entries of the database corresponding to the candidate set of substances, thereby identifying a subset of candidate substances, wherein each candidate substance in the subset of candidate substances has a Raman shift corresponding to the further Raman shift, an excluding function configured to exclude, from the set of candidate substances, candidate substances not forming part of the subset of candidate substances, thereby reducing the set of candidate substances.

The above-mentioned features and advantages of the first aspect, when applicable, apply to this third aspect as well. In order to avoid undue repetition, reference is made to the above.

The circuitry may be configured to repeatedly reduce the set of candidate substances until the set of candidate substances is a single candidate substance.

The exposure time setting function may be configured to set the exposure time such that the first Raman spectrum is within a dynamical range of an optical sensor of the spectrometer.

The further exposure time setting function may be configured to set the further exposure time such that the intensity of at least one Raman peak of the further Raman spectrum exceeds a dynamical range of an optical sensor of the spectrometer.

The circuitry may further be configured to execute:
a compound Raman spectrum forming function configured to form a compound Raman spectrum based on identified Raman peaks.

According to a third aspect there is provided a computer program as defined with claim <NUM>. The computer program comprising instructions to cause the Raman spectroscopy device of the second aspect to execute the steps of the method of the first aspect.

According to a fourth aspect there is provided a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium having stored thereon the computer program of the third aspect. In other words, the non-transitory computer-readable storage medium having stored thereon program code portions or instructions for implementing the method according to the first aspect, when executed in the circuitry of the Raman spectroscopy device according to the second aspect.

The above-mentioned features and advantages of the first aspect, when applicable, apply to this fourth aspect as well. In order to avoid undue repetition, reference is made to the above.

However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention as defined and limited only by the appended claims will become apparent to those skilled in the art from this detailed description.

Hence, it is to be understood that this invention is limited only by the appended claims and not limited to the particular component parts of the device described or acts of the methods described as such device and method may vary.

The figures should not be considered limiting; instead, they are used for explaining and understanding.

The present inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred variants of the inventive concept are shown. This inventive concept may, however, be implemented in many different forms and should not be construed as limited to the variants set forth herein; rather, these variants are provided for thoroughness and completeness, and to fully convey the scope of the present inventive concept to the skilled person. The invention is limited only by the scope of the appended claims.

In connection with <FIG> there is shown a flowchart for a method <NUM> for identifying a set of candidate substances of a sample using a Raman spectroscopy device. The "sample" will henceforth refer to a substance or material to be identified, if not stated otherwise. Before continuing with the description of the method <NUM>, a general overview of the Raman spectroscopy device <NUM> is briefly discussed with reference to <FIG>.

In connection with <FIG> there is shown a block diagram of the Raman spectroscopy device <NUM>.

The Raman spectroscopy device may be a handheld Raman spectroscopy device <NUM>. The Raman spectroscopy device <NUM> may thereby be suitable for use under field conditions. The Raman spectroscopy device may thus be designed such that it is suitable to be hand carried and hand operated by an operator. Hence the Raman spectroscopy device <NUM> typically includes its own power source and may consequently be used without any external power. Further, the Raman spectroscopy device <NUM> is typically self-sufficient in the sense that the Raman spectroscopy device <NUM> may operate on its own without requiring a connection to any external entity or data source. Hence, the Raman spectroscopy device <NUM> may function in absence of wireless communication means, i.e. without exploiting a cellular network, cloud-based services, or the like. However, the present disclosure may advantageously be used in non-handheld Raman spectroscopy systems, such as Raman spectroscopy systems used in laboratories. Moreover, the Raman spectroscopy device <NUM> may be connected to, e.g. the internet to exchange data such as measurement data or data related to firmware updates with external entities.

The Raman spectroscopy device <NUM> comprises an optical arrangement <NUM> including a spectrometer <NUM>. The depicted spectroscopy device <NUM> is designed to analyze inelastically scattered light <NUM> from a sample <NUM>. In other words, the depicted Raman spectroscopy device <NUM> is designed to analyze a Raman contribution in light <NUM> scattered from the sample <NUM>. Hence, the depicted Raman spectroscopy device <NUM> includes a spectrometer <NUM> which may analyze the Raman contribution in light <NUM> scattered form the sample <NUM>. The sample <NUM> may for instance be a solid object, a powder, or a liquid to give a few non-limiting examples.

Generally speaking, the spectroscopy device <NUM> includes an optical arrangement <NUM> and circuitry <NUM>. The circuitry <NUM> of <FIG> will be further described in connection with <FIG> below. The optical arrangement <NUM> and the circuitry <NUM> are connected to each other such that the respective components may communicate and cooperate in order to analyze light <NUM> scattered from the sample <NUM>.

The depicted Raman spectroscopy device <NUM> is configured to emit light <NUM> towards the sample <NUM>. The emitted light <NUM> thus interacts with the sample <NUM> which scatters the light <NUM>. The light <NUM> thus interacts with the sample <NUM> which scatters the light <NUM> elastically and in-elastically, hence resulting in scattered light <NUM>. The scattered light <NUM> is receivable by the optical arrangement <NUM> of the depicted spectroscopy device <NUM>. The optical arrangement <NUM> of the depicted spectroscopy device <NUM> is consequently configured to emit light <NUM> and receive and analyze scattered light <NUM>.

A light source of the optical arrangement <NUM> of the Raman spectroscopy device <NUM> is thereby configured to illuminate the sample <NUM> via a lens of the optical arrangement <NUM>. The light source may be a laser that may generate a laser beam <NUM> having any adequate wavelength. Adequate wavelengths in connection to Raman spectroscopy are wavelengths capable of generating relatively large inelastic scattering events upon interaction between the laser beam <NUM> and the sample <NUM> such that a useful Raman signal may be detected by the optical arrangement <NUM>. A wavelength of a laser light source may have a nominal wavelength of <NUM>.

With respect to the brief and general above description of the Raman spectroscopy device <NUM>, the method <NUM> in connection with <FIG> and <FIG> will now be described.

The method <NUM> comprises setting <NUM> an exposure time of the spectrometer <NUM>. The exposure time may be automatically set. For such an automatically setting of exposure time a plurality of relatively short light pulses may be emitted by the laser for interaction with the sample <NUM>. From recorded Raman intensities in connection thereto calculation of an exposure time may be done for usage of, e.g. <NUM>% of the dynamical range of the sensor. A range of exposure times are possible. In the present context, a short exposure time may be of the order of <NUM> milliseconds, ms. Conversely, a long exposure time may be of the order of <NUM> seconds, s. As already set out above, applied to the present Raman spectroscopy device, exposure times in question may lie in the range <NUM>-<NUM>. Recording of samples comprising highly symmetric molecules resulting in relatively strong Raman signals may typically use exposure times in the range <NUM>-<NUM>. Recording of samples comprising less symmetric molecules resulting in weaker Raman signals may use exposure times in the range <NUM>-<NUM>. The skilled person appreciates that any adequate exposure time may be used without departing from the scope of the claims.

The method <NUM> further comprises recording <NUM> a Raman spectrum of the sample using the spectrometer <NUM> being set to the exposure time.

The method <NUM> further comprises identifying <NUM> a Raman peak having a largest intensity of at least one Raman peak of the Raman spectrum. For certain samples comprising molecules having certain symmetry properties, the Raman peak having the largest intensity may, by way of example, be at least one order of magnitude larger than any other peak in the wavelength band under consideration. An example of such a molecule may be a Benzene molecule, having a large Raman peak at approximately <NUM>-<NUM>, whereas remaining Raman peaks are significantly smaller. Herein, and generally within the field of spectroscopy, the unit cm-<NUM>, i.e. the unit for the quantity wavenumber, refers to the inverse wavelength of light. Hence the previous Raman peak, <NUM>-<NUM>, corresponds to the wavelength <NUM>/<NUM> = <NUM>. Typical wavelengths considered in Raman spectroscopy may lie in the range <NUM>-<NUM>, i.e. in the mid-IR spectrum. Hence, these typical wavelengths may be relatively large compared to the (<NUM>) laser typically used. For practical reasons, a Raman spectrum may be represented in an intensity versus wavelength graph by transforming the wavelength axis according to the equation <MAT>.

In the present example, considering the <NUM>-<NUM> peak (Raman shift = <NUM> in the equation) and the <NUM> laser wavelength (λex = <NUM> in the equation), the <NUM>-<NUM> peak is located approximately at the wavelength <NUM> in the corresponding Raman spectrum. Again, the wavelengths are typically converted to cm-<NUM>. It is appreciated that a Raman spectrum may be represented in many ways in an intensity versus wavelength graph. Hence, below, the words wavenumber and wavelength may be used interchangeably, which should not confuse the skilled person within the present context.

The method <NUM> further comprises determining <NUM> a Raman shift of the identified Raman peak in the Raman spectrum. Per the above, a "Raman shift of a Raman peak" refers to a wavelength difference between an excitation wavelength and a wavelength of the laser. Most of the light, scattered from the sample towards the sensor, includes elastically scattered light, i.e. having the wavelength of the laser. Should this light hit the sensor a large peak would be present at the laser wavelength in a spectrum that also includes a wavelength interval extending above and below the wavelength of the laser. This light is preferably filtered out from the scattered light by a lowpass filter before reaching the sensor. However, in practice, a small fraction originating from Rayleigh scattering will still typically reach the sensor. The laser wavelength in such a spectrum is typically referred to as the Rayleigh line. Herein, Stokes scattering, i.e. wavelengths corresponding to a photon energy being lower (i.e., longer wavelengths) than the photon energy of the laser, is considered. Wavelengths of scattered light <NUM> corresponding to the anti-Stokes band may, as described above, be filtered out before reaching the sensor. It is however appreciated that the method applies equally well to anti-Stokes scattering, i. e wavelengths corresponding to a photon energy being higher than the photon energy of the laser. However, anti-Stokes scattering is in general associated with intensities being relatively small compared to corresponding Stokes scattering events, hence being more difficult to detect and draw conclusions from.

The method <NUM> further comprises comparing <NUM> the Raman shift against a database comprising entries correlating substances with information associated with Raman shifts of the substances, thereby identifying a set of candidate substances, wherein each candidate substance in the set of candidate substances has a Raman shift corresponding to the Raman shift. The database preferably comprises a relatively large number of substances, each substance being associated with certain properties, such as wavelengths of characterizing Raman peaks of the substance, relative intensities between Raman peaks, etc. A substance in the database is thereby associated with a "fingerprint" for possible matching with a substance for which the Raman spectroscopy device has recorded a Raman spectrum. Should only a single peak be present in the recorded Raman spectrum, the candidate list of substances may be relatively extensive, which may obscure a proper identification of the substance. The comparison <NUM> per the above, and, subsequently, identifying the set of candidate substances may be done by an ordinary procedure within the art. As a fictious example, a sample <NUM> to be identified, exhibits two detected Raman peaks at <NUM>-<NUM> and <NUM>-<NUM>. The <NUM>-<NUM> is five times as high as the <NUM>-<NUM> peak. A specific substance of the set of substances in the database has two peaks; one at <NUM>-<NUM> and one at <NUM>-<NUM>, where the <NUM>-<NUM> is four times as high as the <NUM>-<NUM> peak. In this example, the sample may be deemed to be the specific substance, since the above data matches "close enough". Hence, the identification may include threshold probabilities and error margins upon identification of a substance of a sample, as is normally the case within the art.

The method further comprises reducing <NUM> the set of candidate substances. The act of reducing <NUM> the set of candidate substances is done by the method steps <NUM>-<NUM> shown in <FIG> as described below.

The act of reducing <NUM> the set of candidate substances comprises setting <NUM> a further exposure time of the spectrometer, the further exposure time being longer than the exposure time.

The act of reducing <NUM> the set of candidate substances further comprises recording <NUM> a further Raman spectrum of the sample using the spectrometer being set to the further exposure time.

Using a longer exposure time may thereby reveal additional Raman peaks. The further exposure time may render the already identified (by step <NUM> above) Raman peak having the largest intensity overexposed. Hence, saturation of the sensor, i.e. "blooming", may be present when recording the same peak using the further exposure time. However, in this step <NUM>, remaining Raman peaks are the Raman peaks taken in consideration, further appreciated below.

The act of reducing <NUM> the set of candidate substances further comprises identifying <NUM>, while excluding wavelengths associated with all previously identified <NUM> Raman peaks, a further Raman peak in the further Raman spectrum, the further Raman peak having a largest intensity of at least one Raman peak in the further Raman spectrum. Hence, this is analogous to the identification <NUM> above.

The act of reducing <NUM> the set of candidate substances further comprises determining <NUM> a further Raman shift of the further Raman peak in the further Raman spectrum.

The act of reducing <NUM> the set of candidate substances further comprises comparing <NUM> the further Raman shift against entries of the database corresponding to the candidate set of substances, thereby identifying a subset of candidate substances, wherein each candidate substance in the subset of candidate substances has a Raman shift corresponding to the further Raman shift.

The act of reducing <NUM> the set of candidate substances further comprises excluding <NUM>, from the set of candidate substances, candidate substances not forming part of the subset of candidate substances, thereby reducing the set of candidate substances. Hence, an updated set of candidate substances takes the place of a previous set of candidate substances, determined by the steps <NUM>-<NUM> above. In the event of the updated set of candidate substances comprises entries identical to the previous set of candidate substances, the act of reducing <NUM> the set of substances may be repeated using a longer exposure time.

The act of reducing <NUM> the set of candidate substances may be repeated until the set of candidate substances is a single candidate substance.

The exposure time may be set such that the first Raman spectrum is within a dynamical range of an optical sensor of the spectrometer. The optical sensor is a sensor for detecting electromagnetic waves, i.e. light. The light may have wavelengths within the visible spectrum, i.e. approximately in the range <NUM>-<NUM>. However, the optical sensor may further be configured to detect ultraviolet, UV, or infrared, IR, light, as is normal for optical sensors within Raman spectroscopy. For instance, the previously mentioned pronounced Raman peak of benzene at <NUM>-<NUM> corresponds to light in the IR spectrum. The Raman shift of the Raman peak thereby refers to a wavelength/wavenumber difference between an excitation wavelength/wavenumber and a wavelength of a light source of the Raman spectroscopy device. By way of example, the light source of the Raman spectroscopy device <NUM> may be a laser emitting a (coherent) laser beam having a wavelength of <NUM>. The optical sensor may be a linear charge-coupled device, CCD. A linear CCD may be a light-sensitive sensor having few pixels, or even a single pixel, in a first dimension, while having a large number of pixels in a dimension perpendicular to the first dimension. For instance, the linear CCD may have <NUM> pixel in the first dimension and <NUM> pixels in the dimension perpendicular to the first dimension. In other words, the CCD may be a liner CCD. Alternatively, the optical sensor may be a complementary metal-oxide-semiconductor, CMOS, sensor. Alternatively, the optical sensor may be a matrix-type CCD or CMOS sensor. The Raman spectrum being within the dynamical range of the optical sensor refers to sensor detection of photons by the optical sensor such that no pixel of the optical sensor becomes saturated. As appreciated by the skilled person, "pixel" is herein to be interpreted widely. For a line CCD, a pixel may refer to a wavelength/wavenumber interval for which detected photons are counted. More generally, a pixel has its normal meaning in that being a discrete light sensitive element of the sensor, similar to ordinary digital imaging/photography.

The further exposure time may be set such that the intensity of at least one Raman peak of the further Raman spectrum exceeds a dynamical range of an optical sensor of the spectrometer. As described above, the further exposure time is longer than the exposure time used to record the first Raman spectrum. Hence, for the further exposure time, at least one pixel of the optical sensor may become saturated when recording the further Raman spectrum. This is conceptually equivalent to overexposure in normal digital photography. Hence, fainter signals, i.e. less intense Raman peaks, in the Raman spectrum may be more pronounced or may be revealed when using the further exposure time.

The method <NUM> may further comprise forming a compound Raman spectrum based on identified Raman peaks. Hence, the compound Raman spectrum may comprise at least two Raman spectra, where each Raman spectrum is recorded using different exposure times. Overexposed portions of respective spectrum may be subtracted or replaced by corresponding not overexposed portions in another spectrum. Hence, a high dynamical range, HDR, spectrum may be formed.

The method <NUM> may be implemented in computer program comprising program code portions to cause the circuitry <NUM> of the Raman spectroscopy device <NUM> to execute the method <NUM>.

The computer program may be stored on a non-transitory computer-readable storage medium.

The method <NUM> may be implemented on a non-transitory computer-readable storage medium having stored thereon program code portions when executed on a device having processing capabilities.

In connection with <FIG>, there is shown, highly schematically, a Raman spectroscopy device <NUM>. The method <NUM> may be implemented on the Raman spectroscopy device <NUM>. Hence, the description in connection with the method <NUM> above, when applicable, also applies to the description of the Raman spectroscopy device <NUM> below. The Raman spectroscopy device comprises a spectrometer <NUM>. The Raman spectroscopy device <NUM> further comprises circuitry <NUM>.

The circuitry <NUM> is configured to carry out overall control of functions and operations of the Raman spectroscopy device <NUM>. The circuitry <NUM> may include a processor, such as a central processing unit (CPU), microcontroller, or microprocessor. The processor is configured to execute program code stored in the circuitry <NUM> to carry out functions and operations of the Raman spectroscopy device <NUM>.

Executable functions, further described below, may be stored on a memory. The memory may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable devices. In a typical arrangement, the memory may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for the circuitry <NUM>. The memory may exchange data with the circuitry over a data bus. Accompanying control lines and an address bus between the memory and the circuitry may be present.

Functions and operations of the circuitry <NUM> may be embodied in the form of executable logic routines, e.g., computer-code portions, software programs, etc., that are stored on a non-transitory computer readable medium, e.g., the memory, of the Raman spectroscopy device <NUM> and are executed by the circuitry <NUM> by, e.g., using the processor. The functions and operations of the Raman spectroscopy device <NUM> may be a stand-alone software application or form a part of a software application that carries out additional tasks related to the electronic device. The described functions and operations may be considering a method that the corresponding device is configured to carry out. Also, while the described functions and operations may be implemented in a software, such functionality may as well be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

The circuitry <NUM> is configured to execute an exposure time setting function <NUM> configured to set an exposure time of the spectrometer.

The circuitry <NUM> is further configured to execute a recording function <NUM> configured to record a Raman spectrum of the sample using the spectrometer being set to the exposure time.

The circuitry <NUM> is further configured to execute a Raman peak identifying function <NUM> configured to identify a Raman peak having a largest intensity of at least one Raman peak of the Raman spectrum.

The circuitry <NUM> is further configured to execute a Raman shift determining function <NUM> configured to identify a Raman shift of the identified Raman peak in the Raman spectrum.

The circuitry <NUM> is further configured to execute a Raman shift comparing function <NUM> configured to compare the Raman shift against a database comprising entries correlating substances with information associated with Raman shifts of the substances, thereby identifying a set of candidate substances, wherein each candidate substance in the set of candidate substances has a Raman shift corresponding to the Raman shift.

The circuitry <NUM> is further configured to reduce the set of candidate substances. In <FIG> this is associated with a reducing function <NUM>.

The reducing function <NUM> is configured to execute a further exposure time setting function <NUM> configured to set a further exposure time of the Raman spectroscopy device, the further exposure time being longer than the exposure time.

The reducing function <NUM> is further configured to execute a further Raman spectrum recording function <NUM> configured to record a further Raman spectrum of the sample using the Raman spectroscopy device being set to the further exposure time.

The reducing function <NUM> is further configured to execute an identifying function <NUM> configured to identify, while excluding wavelengths associated with identified Raman peaks, a further Raman peak in the further Raman spectrum, the further Raman peak having a largest intensity of Raman peaks in the further Raman spectrum.

The reducing function <NUM> is further configured to execute a further Raman shift determining function <NUM> configured to determine a further Raman shift of the further Raman peak in the further Raman spectrum.

The reducing function <NUM> is further configured to execute a comparing function <NUM> configured to compare the further Raman shift against entries of the database corresponding to the candidate set of substances, thereby identifying a subset of candidate substances, wherein each candidate substance in the subset of candidate substances has a Raman shift corresponding to the further Raman shift.

The reducing function <NUM> is further configured to execute an excluding function <NUM> configured to exclude, from the set of candidate substances, candidate substances not forming part of the subset of candidate substances, thereby reducing the set of candidate substances.

The circuitry <NUM> may further be configured to repeatedly reduce the set of candidate substances until the set of candidate substances is a single candidate substance.

The exposure time setting function <NUM> may further be configured to set the exposure time such that the first Raman spectrum is within a dynamical range of an optical sensor of the spectrometer.

The further exposure time setting function may further be configured to set the further exposure time such that the intensity of at least one Raman peak of the further Raman spectrum exceeds a dynamical range of an optical sensor of the spectrometer <NUM>.

The circuitry <NUM> may further be configured to execute a compound Raman spectrum forming function configured to form a compound Raman spectrum based on identified Raman peaks.

In connection with <FIG>, there is shown an example Raman spectrum of benzene. This by using an excitation wavelength of <NUM>. In <FIG> there is shown a Raman spectrum being recorded using the first exposure time. The first exposure time in this specific example is set to <NUM>. The first exposure time is such that the pronounced <NUM>-<NUM> peak lies within the dynamical range of the optical sensor. Two smaller Raman peaks, at <NUM> and <NUM>-<NUM>, are visible but small relative to the larger <NUM>-<NUM> peak at this scale. The measurement of this spectrum may generate a set of candidate substances having a plurality of entries, i.e. including substances other than benzene, benzene isotopes, or the like. This set of candidate substances may be reduced by performing a measurement using a second exposure time being longer than the first exposure time, described above. The second exposure time in this specific example is set to <NUM>, i.e. approximately five times longer than the first exposure time. A Raman spectrum of benzene recorded using such a longer exposure time is shown in <FIG>. Here, the <NUM>-<NUM> peak is saturated due to the longer exposure time. On the other hand, the smaller Raman peaks at <NUM> and <NUM>-<NUM> appear more pronounced compared to the corresponding peaks in Fig. 3A. Further, the smaller peaks do normally have a larger SNR compared to the corresponding peaks for shorter exposure times. Hence, the wavelengths for the smaller peaks can be specified with a larger certainty than for shorter exposure times. This alone may reduce the number of substances in the set of candidate substances. A fourth Raman peak, at <NUM>-<NUM>, appears in <FIG>. A Raman peak corresponding to the fourth Raman peak is absent in <FIG>. Hence, four Raman peaks may be deemed to be detected in <FIG>. The wavelengths and possibly relative intensities of the Raman peaks may be sufficient to reduce the number of substances in the set of candidate substances to a single substance. Should there still be a plurality of substances in the set of candidate substances, an additional recording may be done, using an exposure time longer than the exposure time used to generate the Raman spectrum in <FIG>. More Raman peaks may thereby be distinguished, which may reduce the set of candidate substances to a single substance deemed to be a correctly identified substance, i.e. benzene.

Accordingly, and in summary, an approach for identifying a set of candidate substances of a sample has been exemplified above in a non-limited way, with emphasis of samples comprising molecules having at least one Raman peak being significantly larger than remaining Raman peaks in the spectrum. The approach records at least two Raman spectra using different exposure times for gradually decreasing the number of candidate substances that matches a Raman fingerprint against a database of the Raman spectroscopy device. More Raman spectra may be recorded using other exposure times such that a single candidate substance remains in the list of candidate substances, the single candidate substance being concluded to be a substance of the sample.

Claim 1:
A method (<NUM>) for identifying a set of candidate substances of a sample (<NUM>) using a Raman spectroscopy device (<NUM>) comprising a spectrometer (<NUM>), the method (<NUM>) comprising:
setting (<NUM>) an exposure time of the spectrometer (<NUM>),
recording (<NUM>) a Raman spectrum of the sample (<NUM>) using the spectrometer (<NUM>) being set to the exposure time,
identifying (<NUM>) a Raman peak having a largest intensity of at least one Raman peak of the Raman spectrum,
determining (<NUM>) a Raman shift of the identified Raman peak in the Raman spectrum,
comparing (<NUM>) the Raman shift against a database comprising entries correlating substances with information associated with Raman shifts of the substances, thereby identifying a set of candidate substances, wherein each candidate substance in the set of candidate substances has a Raman shift corresponding to the Raman shift, and
reducing (<NUM>) the set of candidate substances by:
setting (<NUM>) a further exposure time of the spectrometer (<NUM>), the further exposure time being longer than the exposure time,
recording (<NUM>) a further Raman spectrum of the sample using the spectrometer (<NUM>) being set to the further exposure time,
identifying (<NUM>), while excluding wavelengths associated with all previously identified Raman peaks, a further Raman peak in the further Raman spectrum, the further Raman peak having a largest intensity of at least one Raman peak in the further Raman spectrum,
determining (<NUM>) a further Raman shift of the further Raman peak in the further Raman spectrum,
comparing (<NUM>) the further Raman shift against entries of the database corresponding to the candidate set of substances, thereby identifying a subset of candidate substances, wherein each candidate substance in the subset of candidate substances has a Raman shift corresponding to the further Raman shift, and
excluding (<NUM>), from the set of candidate substances, candidate substances not forming part of the subset of candidate substances, thereby reducing the set of candidate substances.