Method and system for measuring raman scattered light from sample

Abstract

Disclosed is a method for measuring Raman scattered light from a sample (102). The method comprises emitting an excitation laser light pulse train, splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains (122), directing the plurality of excitation laser light pulse trains towards a plurality of measurement points (212, 214, 216), receiving a plurality of Raman scattered light pulse trains (124) for being directed towards a plurality of pulse emitting points (232, 234, 236), and capturing the plurality of Raman scattered light pulse trains from the plurality of pulse emitting points at an interval of a predetermined time-period (T1, T2). The method comprises delaying one of: the plurality of excitation laser light pulse trains directed towards the plurality of measurement points, or the plurality of Raman scattered light pulse trains emitted by at the plurality of pulse emitting points, by the predetermined time-period.

Description

[0001] METHOD AND SYSTEM FOR. MEASURING RAMAN SCATTERED LIGHT

[0002] FROM SAMPLE

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a method for measuring Raman scattered light from a sample. The present disclosure also relates to a system for measuring Raman scattered light from a sample.

[0005] BACKGROUND

[0006] Raman spectroscopy is used in many different contexts, for example identification of molecules, investigation of chemical and intramolecular bonds, characterization of materials, determination of a substance's crystallographic orientation, observation of low-frequency excitations of a solid, identification of active pharmaceutical ingredients and their polymorphic forms, and so on. Moreover, multipoint Raman spectroscopic technique enables rapid acquisition of a number of spectra over a large area of a sample. The multipoint Raman spectroscopy is important for example in industrial applications where Raman spectrum is required to be measured from several locations, for example 2-10 locations.

[0007] Typically, charged coupled devices (CCD) or Complementary Metal Oxide Semiconductor (CMOS) imaging sensors are used to collect Raman spectrum from multiple measurement points. Conventionally, the multipoint Raman spectroscopy is done by said imaging sensors at individual measurement points through a spectrograph with the help of a large CCD or CMOS sensors. The multipoint Raman spectroscopy is possible using said imaging sensors in continuous wave Raman spectroscopy. However, use of said imaging sensors may be difficult or even impossible for time-gated Raman spectroscopy due to limitations of integrated circuit (IC) design layout required for operation of CMOS Single-Photon Avalanche Diode (SPAD) photodetector. Specifically, said imaging sensors are required to be operated in an ON state for an amount of time which ranges in picoseconds, due to which it becomes difficult to detect the time-gated Raman spectroscopy for said imaging sensors.

[0008] Furthermore, optomechanical fibre multiplexers are used with time-gated Raman spectroscopy. However, the optomechanical fibre multiplexers comprise moving parts, lenses and / or mirrors, optical benches, holders and mounts, optical rails and carriers, bases, diffraction gratings, prism, and so forth. The components of the optomechanical multiplexers may suffer change in transmission characteristics when used for a period of time (for example, more than couple of years) due to wear and tear. Furthermore, the optomechanical fibre multiplexers are delicate and accordingly calibration of a measuring scale of such optomechanical fibre multiplexers may be easily affected by rough and / or excessive use. Accordingly, the change in transmission characteristics of such optomechanical multiplexers can cause more errors while capturing measurement data associated with samples.

[0009] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with a multipoint time-gated Raman spectroscopy.

[0010] SUMMARY

[0011] The present disclosure seeks to provide a method for measuring Raman scattered light from a sample. The present disclosure also seeks to provide a system for measuring Raman scattered light from a sample. An aim of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in prior art.

[0012] In one aspect, an embodiment of the present disclosure provides a method for measuring Raman scattered light from a sample, the method comprising: - emitting an excitation laser light pulse train from a pulsed laser source;

[0013] - splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains by an optical splitter;

[0014] - receiving the plurality of excitation laser light pulse trains by an excitation optical component for being directed towards a plurality of measurement points in the sample, wherein each of the plurality of measurement points receives a respective excitation laser light pulse train from the plurality of the excitation laser light pulse trains;

[0015] - receiving a plurality of Raman scattered light pulse trains by a collection optical component from the sample;

[0016] - receiving the plurality of Raman scattered light pulse trains by a fibre array block from the collection optical component, the fibre array block comprises a plurality of pulse emitting points;

[0017] - emitting the plurality of Raman scattered light pulse trains by the plurality of pulse emitting points towards a spectrograph in a spatially offset manner; and

[0018] - capturing the plurality of Raman scattered light pulse trains from the spectrograph by a detector during an interval of a predetermined timeperiod;

[0019] - wherein the method further comprises delaying one of:

[0020] - the plurality of excitation laser light pulse trains to be received at the plurality of measurement points of the sample via the excitation optical component, wherein each of the plurality of excitation laser light pulse trains is delayed by a predetermined time-period for each of the plurality of excitation laser light pulse trains, for being incident on the sample at the interval of the predetermined timeperiod, or

[0021] - the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points of the fibre array block via the collection optical component, wherein each of the plurality of Raman scattered light pulse trains is delayed by a predetermined time-period for each of the plurality of the Raman scattered light pulse trains, for being captured by the detector at the interval of the predetermined time-period.

[0022] In another aspect, an embodiment of the present disclosure provides a system of measuring a Raman scattered light from a sample, the system comprising:

[0023] - a pulsed laser source for emitting an excitation laser light pulse train;

[0024] - an optical splitter for splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains;

[0025] - an excitation optical component for receiving and directing the plurality of excitation laser light pulse trains towards a plurality of measurement points in the sample, wherein each of the plurality of measurement points receives a respective excitation laser light pulse train from the plurality of the excitation laser light pulse trains;

[0026] - a collection optical component for receiving a plurality of Raman scattered light pulse trains from the sample;

[0027] - a fibre array block for receiving the plurality of Raman scattered light pulse trains from the collection optical component, wherein the fibre array block comprises a plurality of the pulse emitting points;

[0028] - a spectrograph for receiving the plurality of Raman scattered light pulse trains emitted by the plurality of pulse emitting points in a spatially offset manner; and

[0029] - a detector for capturing the plurality of Raman scattered light pulse trains from the spectrograph during an interval of a predetermined timeperiod;

[0030] - wherein one of the excitation optical component and the collection optical component is configured to delay:

[0031] - the plurality of excitation laser light pulse trains to be received at the plurality of measurement points by a predetermined timeperiod for each of the plurality of excitation laser light pulse trains, for being incident on the sample at the interval of the predetermined time-period, or

[0032] - the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points by a predetermined timeperiod for each of the plurality of the Raman scattered light pulse trains, for being captured by the detector at the interval of the predetermined time-period, respectively.

[0033] Embodiments of the present disclosure substantially eliminate or at least partially address the aforementioned problems in the prior art and enable multipoint time-gated Raman spectroscopy without using conventional optomechanical multiplexers. The aspect of multipoint time-gated Raman spectroscopy is achieved with the use of excitation and collection optical components, configured to delay the plurality of excitation laser light pulse trains to be incident on the plurality of measurement points of the sample or plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points of the fibre array block, respectively. Further, the plurality of pulse emitting points of the fibre array block emit the plurality of Raman scattered light pulse trains towards the spectrograph in a spatially offset manner, and the spectrograph directs the plurality of Raman scattered light pulse trains to be captured by the detector at the intervals of the predetermined time-period. Additional aspects, advantages, features, and samples of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments construed in conjunction with the appended claims that follow.

[0034] It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those skilled in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.

[0036] Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:

[0037] FIG. 1 is a block diagram of a system for measuring Raman scattered light from a sample, in accordance with an embodiment of the present disclosure;

[0038] FIG. 2 is a schematic diagram of the system of FIG. 1 having an excitation optical component configured to delay a plurality of excitation laser light pulse trains by a predetermined time-period, in accordance with an embodiment of the present disclosure;

[0039] FIG. 3 is a schematic diagram of the system of FIG. 1 having a collection optical component configured to delay a plurality of Raman scattered light pulse trains by a predetermined time-period, in accordance with another embodiment of the present disclosure;

[0040] FIG. 4 is a schematic diagram of system-elements of the system of FIGs.

[0041] 2 and 3 for depicting capturing of a plurality of Raman scattered light pulse trains, in accordance with an embodiment of the present disclosure;

[0042] FIG. 5 is a schematic diagram of system-elements of the system of FIGs.

[0043] 2 and 3 for depicting synchronized activation of a detector for capturing the plurality of Raman scattered light pulse trains, in accordance with an embodiment of the present disclosure; FIG. 6 is an exemplary perspective view of a fibre array block of the system of FIGs. 2 and 3, in accordance with an embodiment of the present disclosure; and

[0044] FIG. 7 is a flowchart listing steps involved in a method for measuring Raman scattered light from a sample, in accordance with an embodiment of the present disclosure.

[0045] In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

[0046] DETAILED DESCRIPTION OF EMBODIMENTS

[0047] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practising the present disclosure are also possible.

[0048] In one aspect, an embodiment of the present disclosure provides a method for measuring Raman scattered light from a sample, the method comprising:

[0049] - emitting an excitation laser light pulse train from a pulsed laser source;

[0050] - splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains by an optical splitter;

[0051] - receiving the plurality of excitation laser light pulse trains by an excitation optical component for being directed towards a plurality of measurement points in the sample, wherein each of the plurality of measurement points receives a respective excitation laser light pulse train from the plurality of the excitation laser light pulse trains;

[0052] - receiving a plurality of Raman scattered light pulse trains by a collection optical component from the sample;

[0053] - receiving the plurality of Raman scattered light pulse trains by a fibre array block from the collection optical component, the fibre array block comprises a plurality of pulse emitting points;

[0054] - emitting the plurality of Raman scattered light pulse trains by the plurality of pulse emitting points towards a spectrograph in a spatially offset manner; and

[0055] - capturing the plurality of Raman scattered light pulse trains from the spectrograph by a detector during an interval of a predetermined timeperiod;

[0056] - wherein the method further comprises delaying one of:

[0057] - the plurality of excitation laser light pulse trains to be received at the plurality of measurement points of the sample via the excitation optical component, wherein each of the plurality of excitation laser light pulse trains is delayed by the predetermined time-period for each of the plurality of excitation laser light pulse trains, for being incident on the sample at the interval of the predetermined timeperiod, or

[0058] - the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points of the fibre array block via the collection optical component, wherein each of the plurality of Raman scattered light pulse trains is delayed by a predetermined time-period for each of the plurality of the Raman scattered light pulse trains, for being captured by the detector at the interval of the predetermined time-period. In another aspect, an embodiment of the present disclosure provides a system of measuring a Raman scattered light from a sample, the system comprising:

[0059] - a pulsed laser source for emitting an excitation laser light pulse train;

[0060] - an optical splitter for splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains;

[0061] - an excitation optical component for receiving and directing the plurality of excitation laser light pulse trains towards a plurality of measurement points in the sample, wherein each of the plurality of measurement points receives a respective excitation laser light pulse train from the plurality of the excitation laser light pulse trains;

[0062] - a collection optical component for receiving a plurality of Raman scattered light pulse trains from the sample;

[0063] - a fibre array block for receiving the plurality of Raman scattered light pulse trains from the collection optical component, wherein the fibre array block comprises a plurality of the pulse emitting points;

[0064] - a spectrograph for receiving the plurality of Raman scattered light pulse trains emitted by the plurality of pulse emitting points in a spatially offset manner; and

[0065] - a detector for capturing the plurality of Raman scattered light pulse trains from the spectrograph during an interval of a predetermined timeperiod;

[0066] - wherein one of the excitation optical component and the collection optical component is configured to delay:

[0067] - the plurality of excitation laser light pulse trains to be received at the plurality of measurement points by the predetermined timeperiod for each of the plurality of excitation laser light pulse trains, for being incident on the sample at the interval of the predetermined time-period, or

[0068] - the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points by a predetermined time- period for each of the plurality of the Raman scattered light pulse trains, for being captured by the detector at the interval of the predetermined time-period, respectively.

[0069] The present disclosure provides a method and a system for measuring Raman scattered light from a sample. Specifically, the method and the system of the present disclosure enables in multipoint time-gated Raman spectroscopy. Typically, the method and the system of the present disclosure precludes a need for conventional optomechanical multiplexers for the multipoint time-gated Raman spectroscopy. The aspect of multipoint time-gated Raman spectroscopy is achieved with the use of the excitation and collection optical components, configured to delay one of incidence of the excitation laser light pulse trains on the sample and capture of the Raman scattered light pulse trains by the detector, respectively, by the predetermined time-period. The lack of optomechanical multiplexers avoids possible loss of transmission characteristics which may be caused due to wear and tear of such optomechanical multiplexers. The method and the system of the present disclosure allows imaging sensors, such as conventional CMOS SPAD, to be used conveniently for the multipoint time-gated Raman spectroscopy, i.e., sensing Raman scattered light pulses typically generated in picoseconds. Also, a size of such imaging sensors may be narrowed (or made smaller) as compared to a size of a standard conventional imaging sensor for performing the multipoint time-gated Raman spectroscopy.

[0070] Throughout the present disclosure, the term "sample” refers to materials that may emit optical radiation, including but not limited to Raman- scattered light, when illuminated with light, such as a laser light. Practically all samples may emit Raman scattered light when illuminated with light, e.g., when the sample comprises molecules and / or a crystal structure that has vibrational energy levels. The sample may comprise for example, an organic material and / or biological material. Further, the sample may comprise for example, a gas, a solid and / or a liquid. The sample may be contained for example, in a sample cell. For example, organic molecules containing conjugated aromatic rings may emit light by fluorescence and by Raman scattering.

[0071] Raman scattering typically comprises two types of radiations, Stokes Raman scattering and Anti-Stokes Raman scattering. The Stokes Raman scattering is an inelastic scattering process where a photon of illuminating light, such as the laser light may lose energy into a change of vibrational and / or rotational state of the sample, i.e., a difference between the energy of the incident photon and the energy of the corresponding scattered photon is positive. The photon of the illuminating light may lose energy into a change of the vibrational state and into a change of the rotational state of the sample. The Anti-Stokes Raman scattering is an inelastic scattering process where a scattered photon may gain energy from a change of the vibrational state of the sample, i.e., a difference between the energy of the incident photon and the energy of the corresponding scattered photon is negative. The photon of the scattered light may gain energy from a change of the vibrational state and from a change of the rotational state of the sample. The Raman spectrum of the sample may be used for example, for providing information about a molecular composition of the sample. The information may be used for example, for qualitative chemical analysis of the sample, for quantitative chemical analysis of the sample, and / or for analysing a crystal structure of the sample. Moreover, an industrial process may be controlled based on the information.

[0072] The method comprises emitting an excitation laser light pulse train from a pulsed laser source. The term "excitation laser light pulse train" refers to a series of laser light pulses generated by the pulsed laser source. The method utilises an intense monochromatic source of light, such as the laser source to generate the excitation laser light pulse train. The pulsed laser source is employed to emit the pulse of light preferably in an ultraviolet range, visible or near-infrared region of electromagnetic spectrum of light. Furthermore, the example of the pulsed laser source may be a diode laser, a solid-state laser, and the like. Additionally, the pulsed laser source may be a Q-switched laser that enables emission of short pulses of light.

[0073] The method further comprises splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains by an optical splitter. In an example, the optical splitter may be 1x3 optical splitter, 1x4 optical splitter, 1x8 splitter, 1x24 splitter or 1x64 splitter and the like, based as requirements. The 1x3 or 1x4 optical splitters configuration may be structures for separating an excitation laser light pulse train into three or four excitation laser light pulse trains, respectively.

[0074] The method further comprises receiving the plurality of excitation laser light pulse trains by an excitation optical component. According to an embodiment, the excitation optical component may be a fibre splitter (PLC splitter or fused fibre splitter). In another embodiment, the excitation optical component may be substituted with a free-space. Essentially, the excitation optical component may be configured to act as an optical delay element, to delay the plurality of excitation laser light pulse trains in their optical paths for being directed towards the sample. For each optical path, there can be a predefined time delay that differs from the time delays of other optical paths.

[0075] In an embodiment, the excitation optical component comprises a plurality of optical fibres. The optical fibres are a thin, flexible strands of transparent material that are capable of transmitting the plurality of laser light pulse trains therethrough. The optical fibres may include a core, which is surrounded by a cladding layer with a lower refractive index. Further, the optical fibres are configured to efficiently transmit the plurality of excitation laser light pulse trains therethrough, with low attenuation and dispersion.

[0076] In one embodiment, each of the plurality of optical fibres is configured to have a length difference, for example relative to other optical fibres, to cause time delay of the predetermined time-period. For example, there may be predetermined length differences between the optical fibres of the excitation optical component and / or the optical fibres of the collection optical component. In an example, the length difference is in a range of 1 to 100 meters. Optionally, the length difference lies in the range of 1, 10, 20, 30, 40, 50, 60, 70, 80 or 90 up to 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 meters. In an example, the length difference may cause time delay of the predetermined time-period in a range of 5 to 500 nanoseconds. Optionally, the intervals of the predetermined time-period may lie in the range of 5, 10, 50, 100, 200, 300, or 400 up to 10, 50, 100, 200, 300, 400 or 500.

[0077] The method further comprises directing the plurality of excitation laser light pulse trains toward the plurality of measurement points in the sample by the excitation optical component. Each of the plurality of measurement points receives an excitation laser light pulse train from the plurality of the excitation laser light pulse trains. The term "plurality of measurement points" is referred to physical points for referencing measurement of the plurality of excitation laser light pulse trains. In simple words, the plurality of measurement points is the number of physical points present in the sample for receiving the plurality of excitation laser light pulse trains thereon. Further, each of the plurality of measurement points receives one excitation laser light pulse train from the plurality of excitation laser light pulse trains. It is to be understood that the number of the plurality of measurement points would be based on a number of the plurality of excitation laser light pulse trains, generated by the optical splitter from the emitted laser light pulse train. For example, if the optical splitter splits the excitation laser light pulse train into 3, 4, 16, 32 or 64 excitation laser light pulse trains, then correspondingly 3, 4, 16, 32 or 64 measurement points are formed at the sample, respectively. Therefore, it will be evident to a person skilled in the art that the number of measurement points of the sample is associated with "multipoint" aspect of the multipoint time-gated Raman spectroscopy.

[0078] According to an embodiment, when the plurality of excitation laser light pulse trains is directed towards the sample, the plurality of Raman scattered light pulse trains would scatter from the sample. For example, the sample is illuminated with a series of excitation laser light pulse trains, each pulse train will cause some of the light to be absorbed and scattered by the sample. This will cause the generation of the plurality of Raman scattered light pulse trains from the sample. As explained herein above, the plurality of excitation laser light pulse trains would be reaching or incident on the plurality of measurement points in the sample with the delay of the predetermined time-period, and accordingly the plurality of Raman scattered light pulse trains would be generated with the delay of the predetermined time-period.

[0079] The method also comprises receiving the plurality of Raman scattered light pulse trains by a collection optical component from the sample. According to an embodiment, the excitation optical component comprises a plurality of optical fibres. Each of the plurality of optical fibres of the collection optical component may be configured to have a length difference relative to the optical fibres in the collection optical component to cause time delay of the predetermined time-period. In an example, the length difference is in a range of 1 to 100 meters. Optionally, the length difference lies in the range of 1, 10, 20, 30, 40, 50, 60, 70, 80 or 90 up to 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 meters. In an example, the length difference may cause time delay of the predetermined time- period in a range of 5 to 500 nanoseconds. Optionally, the predetermined time-period lies in the range of 5, 10, 50, 100, 200, 300, or 400 up to 10, 50, 100, 200, 300, 400 or 500.

[0080] The method further comprises receiving the plurality of Raman scattered light pulse trains by the fibre array block from the collection optical component, and the fibre array block comprises a plurality of pulse emitting points. Each of the plurality of the pulse emitting points is configured to emit one Raman scattered light pulse train towards the spectrograph. The method also comprises emitting the plurality of Raman scattered light pulse trains by the plurality of pulse emitting points towards the spectrograph in the spatially offset manner.

[0081] According to embodiment, the term "plurality of pulse emitting points" is referred to physical points for referencing measurement of the plurality of Raman scattered light pulse trains. In other words, the plurality of pulse emitting points may be associated input slits or fibres present in the fibre array block configured to emit the plurality of Raman scattered light pulse trains therethrough. For example, each of the plurality of pulse emitting points may be ends, of the input slits or the fibres of the fibre array block, that emit the plurality of the Raman scattered light pulse trains therethrough. It is to be understood that the number of the plurality of pulse emitting points may be based on a number of the plurality of optical fibres present in the collection optical component. The plurality of optical fibres of the collection optical component acts as optical channels for allowing the plurality of the Raman scattered light pulse trains to pass therethrough and received by the fibre array block. Further, the number of the plurality of optical fibres present in the collection optical component may be based on the number of the number of the measurement points, associated with the sample, which in turn based on number of the plurality of optical fibres present in the excitation optical component. In an embodiment, the method comprises arranging the plurality of pulse emitting points of the fibre array block in a spatially offset manner by a predetermined distance. Basically, each of the plurality of pulse emitting points is spaced apart from each other, such that a pulse emitting point and an adjacent pulse emitting point are spaced apart by the predetermined distance. In other words, the fibre array block may be a block having the plurality of optical fibres, each fibre having a uniform length. For example, the optical fibres may be arranged side by side, stacked on top of each other, to from of matrix (two-dimensional grid of points). As explained herein above, the plurality of optical fibres is arranged in the spatially offset manner to form the matrix, and each of the plurality of optical fibres is spaced apart from an adjacent optical fibre by the predetermined distance.

[0082] According to an embodiment, the predetermined distance is in a range of 10 to 1000 micrometres. Optionally, the predetermined distance lies in the range of 10, 100, 200, 300, 400, 500, 600, 700, 800 or 900 up to 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 micrometres. In an example, the precise enough placement of the optical fibres can be achieved by using a 2D matrix fibre array based on a precision machined glass substrate. Also, V-groove based fibre arrays may be used for stacking the optical fibres. It is to be understood that an output end portion of the optical fibres of the fibre array block emitting the plurality of Raman scattered light pulse trains therethrough, may define the plurality of pulse emitting points for the fibre array block. Accordingly, the plurality of pulse emitting points depends on the number of optical fibres present in the fibre array block.

[0083] In an embodiment, a row or a column, of the matrix, of the plurality of optical fibres may define a single pulse emitting point. For example, if the fibre array block includes 12 optical fibres, which may constitute a 3*4 matrix, and then each row or column (having 4 optical fibres each) may define a single pulse emitting point. Accordingly, the fibre array block may include a total of 3 distinct pulse emitting points. The collection or group optical fibres in such a manner may cause collection of more light, while emitting the of Raman scattered light pulse trains therethrough. Alternatively, the fibre array block having 12 optical fibres may be considered to have 12 distinct pulse emitting points (which may correspond to 12 distinct measurement points in the sample). Further, all the optical fibres of the fibre array block may have same length, or different length.

[0084] Based on above description, it is to be understood that the excitation optical component and / or the collection optical component may have a plurality of optical fibres, of which each may be configured to have a length difference relative to other optical fibres, to cause time delay of a predetermined time-period for each of the plurality of light pulse trains. With time delays, it is achieved that the capturing of Raman-scattered light pulse trains by the detector is delayed in a predetermined manner. In other words, delaying the plurality of Raman scattered light pulse trains in their optical paths by a plurality of predetermined time delays causes capturing of the collection signal pulses at the detector at different times.

[0085] The method further comprises capturing the plurality of Raman scattered light pulse trains from the spectrograph by a detector at an interval of a predetermined time-period.

[0086] According to an embodiment, the detector may be a Complementary Metal Oxide Semiconductor (CMOS). Specifically, the detector may include a CMOS single-photon avalanche diode (SPAD), which will be explained in greater detail herein later.

[0087] The method further comprises delaying one of: - the plurality of excitation laser light pulse trains to be received at the plurality of measurement points of the sample via the excitation optical component, wherein each of the plurality of excitation laser light pulse trains is delayed by the predetermined time-period for being incident on the sample at the interval of the predetermined time-period, or

[0088] - the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points of the fibre array block via the collection optical component, wherein each of the plurality of Raman scattered light pulse trains is delayed by the predetermined time-period for being captured by the detector at the interval of the predetermined timeperiod.

[0089] In an embodiment, the method further comprises capturing the plurality of Raman scattered light pulse trains from the spectrograph by a predefined area of the detector. According to an embodiment, the "predefined area" of the detector is an area of the detector defined by a physical measurement points of the detector. It will be evident that based on a number of the physical measurement points of the detector a size of the predefined area of the detector may increase or decrease. In the present disclosure, a smaller number of the physical measurement points would define the predefined area for the detector, which can be efficiently used for performing the multipoint time-gated Raman spectroscopy. Typically, the plurality of Raman scattered light pulse trains exiting the plurality of pulse emitting points of the fibre array block are received by the spectrograph, which focuses the plurality of Raman scattered light pulse trains towards the detector. Further, the delay caused by the plurality of pulse emitting points while directing the plurality of Raman scattered light pulse trains towards the spectrograph allows a same portion of detector (or the predefined area for the detector) to receive or capture the plurality of Raman scattered light pulse trains directed towards the detector. This allows the detector to be efficiently used for performing the multipoint time-gated Raman spectroscopy. In simple words, according to the present disclosure the detector may be made of a smaller number of photo sensors, such as CMOS SPAD, which can be used conveniently for the multipoint time-gated Raman spectroscopy.

[0090] According to an embodiment, the method further comprises directing the plurality of Raman scattered light pulse trains towards the spectrograph prior to capturing the plurality of Raman scattered light pulse trains by the detector. The spectrograph is configured to:

[0091] - collimate the plurality of Raman scattered light pulse trains received from the plurality of the pulse emitting points,

[0092] - disperse the plurality of collimated Raman scattered light pulse trains, and

[0093] - focus the plurality of dispersed Raman light pulse trains for being directed towards the detector.

[0094] It may be evident that the aspects of collimating, dispersing and focusing the plurality of Raman light pulse train is associated with a typical spectrograph. For example, the spectrograph may include a collimating lens for collimating the plurality of Raman scattered light pulse trains exiting the plurality of pulse emitting points, a diffraction grating for dispersing the plurality of collimated Raman scattered light pulse train, and a focusing lens for focusing the plurality of dispersed Raman light pulse train for being captured by the detector. In an example, the spectrograph may be based on a volumetric holographic grating. Further, it may be evident that the spectrograph is arranged in front of the detector for inputting the Raman scattered light pulse trains into the detector. Moreover, the fibre array block may be arranged prior to the spectrograph, which is arranged prior to the detector.

[0095] In an embodiment, the method further comprises synchronizing activation of the detector based on the interval of the predetermined time-period. The term "synchronizing" used herein refers to deciding a time period to turn ON and OFF the detector for measuring the plurality of Raman scattered light pulse trains. Typically, the multipoint time-gated Raman spectroscopy related to the present disclosure employs a timeresolving detector (such as the CMOS SPAD sensor element) that is configured to remain in an "ON-state" for a short duration of time for the measurement of the Raman scattered light falling thereupon, whereas they are configured to remain in an "OFF-state" for a duration of time during which mostly fluorescence or other non-Raman optical emission is observed. Notably, the emission of light by fluorescence is typically a long-lifetime process when compared with emission of the Raman radiation. Therefore, the "ON-state" associated with the sensor elements is ideally equal to the temporal width of the laser pulse, e.g., 1 to 5 nano seconds (ns) which is further divided in 32 time slots, during which the Raman radiation is observed. Such an apparatus employing the timegated Raman spectroscopy eliminates part of the effect of fluorescence (particularly the tail part of the fluorescence). In simple words, the detector is turned ON at a point in time, after intervals of the predetermined time-period, i.e., delays caused by the excitation or collection optical components for the Raman scattered light pulse trains to reach the detector. In an embodiment, a controller enables in synchronizing activation of the detector.

[0096] According to an embodiment, the method further comprises calibrating signals measured, by the predefined area of the detector, corresponding to the plurality of Raman scattered light pulse trains captured from the spectrograph. The term "calibrating" the signals measured by the detector used herein refers to correcting or adjusting peaks of measured signals (spectral intensity of Raman spectrum) which are offset by a small distance on a spectral direction on the detector. The small distance (or the offset) between the measured signals on the spectral direction of the detector is caused due to the pre-determined distance between the optical fibres of the fibre array block. Therefore, calibrating the signals allow adjusting or correcting the measured signals to ensure they are accurate and in a correct position (or the predefined area of the detector) on the detector's spectral direction. In an example, this may be done by comparing the measured signals to a known reference signal and adjusting the measured signals to correct any offset in peaks of measured signal intensities (for example, by adjusting a wavelength axis of the Raman spectrum). This is done to improve the precision and accuracy of the measurements taken by the pre-determined are of the detector.

[0097] Optionally, in the present disclosure, the activation of the detector is synchronized based on a control signal, i.e., the detector would be turned ON between spectral intensity distribution cycles. Further, the spectral intensity distribution cycles are based on delays of the predetermined time-period (for incidence of the plurality of excitation laser light pulse trains on the sample or capturing of the plurality of Raman scattered light pulse trains from the sample). Importantly, the predetermined timeperiod is in the range of 5 to 500 nanoseconds, which allows imaging sensors such as CMOS SPAD imaging matrix to efficiently perform timegated Raman spectroscopy.

[0098] Additionally, the method further comprises synchronizing activation of the pulsed laser source based on the predetermined time-period. In simple words, the pulsed laser source would be turned ON subsequently only when an excitation laser light pulse train emitted by the pulsed laser source is measured by the detector, and the detector is ready for measuring a subsequent excitation laser light pulse train to be emitted by the pulsed laser source. It will be evident that activation of the pulsed laser source accordingly corelated with the delay of the predetermined time-period to be caused on the excitation or collection optical components.

[0099] The present disclosure also relates to the system as described above. Various embodiments and variants disclosed above, with respect to the aforementioned method, apply mutatis mutandis to the system. Optionally, the system further comprises a controller operatively coupled to the pulsed laser source and the detector, wherein the controller is operable to synchronize activation of the detector based on the interval of the predetermined time-period.

[0100] Optionally, the system also comprises a spectrograph, i.e., a combination of at least a collimating lens, a diffraction grating and a focusing lens.

[0101] Optionally, the system may comprise a data processing unit for processing the measured values obtained from the sensor element. The apparatus may comprise a memory for storing output values determined from the measured values. The output values may specify a measured time-resolved optical spectrum of the sample. The data processing unit may be configured to determine time delays and operated the pulsed laser source and the detector based on the same.

[0102] Optionally, the system may comprise a memory for storing operating parameters. For example, the operating parameters may include time delays and data associated the time delays, spectral data and so forth.

[0103] Optionally, the system may comprise a user interface for providing information to a user and / or for receiving user input from the user. The user interface may comprise for example, a display, touch screen and / or a keypad. For example, the user interface may be configured to graphically display a measured time-resolved optical spectrum. For example, the user interface may be configured to display a graph, such as a histogram, which represents a measured time-resolved optical spectrum.

[0104] Optionally, the system may comprise communication unit for sending and / or receiving data. The communication unit may be arranged to communicate with a local area network, with the Internet, and / or with mobile communications network. The system may also be arranged perform data processing in a distributed manner, such as by using an Internet server.

[0105] DETAILED DESCRIPTION OF THE DRAWINGS

[0106] Referring to FIG. 1, illustrated is a block diagram of a system 100 for measuring Raman scattered light from a sample 102, in accordance with an embodiment of the present disclosure. The system 100 comprises a pulsed laser source 104, an optical splitter 106, an excitation optical component 108, a collection optical component 110, a fibre array block 112, a spectrograph 114 and a detector 116. The system 100 also comprises a controller 120 operatively coupled to the pulsed laser source 104 and the detector 116. FIG. 1 also depicts, a plurality of excitation laser light pulse trains 122 directed towards the sample 102 by the excitation optical component 108, and a plurality of Raman scattered light pulse trains 124 to be received the collection optical component 110 from the sample 102.

[0107] In operation, a laser light pulse trains from the pulsed laser source 104 are outputted to the optical splitter 106 which splits the excitation laser light pulse trains into a plurality of excitation laser light pulse trains. After the optical splitter, the plurality of excitation laser light pulse trains is directed by the excitation optical component 108 towards the sample 102, for being directed towards a plurality of measurement points in the sample 102, wherein each of the plurality of measurement points receives a respective excitation laser light pulse train from the plurality of the excitation laser light pulse trains. Laser light pulse trains which are reflected from the surface of the sample, including the Raman-scattered light, are directed into the collection optical component 110, where the plurality of Raman scattered light pulse trains travels back toward the fibre array block 112 and is then transmitted via it to the detector 116 coupled to the spectrograph 114. FIG. 2 is a schematic diagram of the system of FIG. 1. In FIG. 2, the excitation optical component 108 comprises a plurality of optical fibres 202, 204, 206 of which each is configured to be associated with the sample 102. More specifically, a first end of the optical fibre 202 is connected to the optical splitter 106 and a second end is connected to the measurement point 212. In addition, a first end of the optical fibre 204 is connected to the optical splitter 106 and a second end is connected to the measurement point 214. In addition, a first end of the optical fibre 206 is connected to the optical splitter 106 and a second end is connected to the measurement point 216.

[0108] Referring to FIG. 2, each of the optical fibres 202, 204, 206 is configured to have length difference relative to other optical fibres 202, 204, 206 in the excitation optical component to cause time delay of the predetermined time-period while directing the plurality of excitation laser light pulse trains towards the measurement points 212, 214, 216. In FIG. 2, the length differences are illustrated by the loops arranged in the optical fibres. For example, as shown, the optical fibre 204 has two loops and the optical fibre 202 has no loops. The number of loops, herein, indicates that the optical fibre 204 is longer than the optical fibre 202. The optical fibre 206 has four loops, so the optical fibre 206 is longer than the optical fibre 204.

[0109] The effect of length differences in optical fibres is further illustrated by graphs. There are three graphs on the right side of FIG. 2 illustrating amplitude of the pulses as a function of time. The uppermost graph (denoted as Excitation 1) depicts excitation laser pulse trains directed to measurement point 212, and the graph in the middle (denoted as Excitation 2), depicts excitation laser pulse trains directed to measurement point 214. The lowermost graph (denoted as Excitation 3) depicts excitation laser pulse trains directed to measurement point 216. Due to length differences in the optical fibres 202, 204, 206, the Raman scattering occurs at different time at the measurement points 212, 214, and 216. In the uppermost graph, the excitation laser pulse is on the left side of the graph. In the middle, the excitation laser pulse has delayed from the above and shifted to the right in the direction of the time axis, and, in the lowermost graph, the excitation laser pulse has further delayed from the above and further shifted to the right. The collection laser light pulses, when reflected from the measurement points of the sample, are detected with the same relative time delays as the excitation laser light pulses.

[0110] FIG. 2 further depicts the collection optical component 110 having a plurality of optical fibres 222, 224, 226 each having a uniform length. Herein, the lengths of the optical fibres 222, 224, 226 may for example be equal. However, the optical fibres 222, 224, 226 do not have to be the same length. Also, FIG. 2 depicts the fibre array block 112 having a plurality of pulse emitting points 232, 234, 236 associated with the plurality of optical fibres 222, 224, 226. More specifically, the optical fibre 222 has a first end which is arranged in connection with the pulse emitting point 232 and a second end which is connected to the measurement point 212. In addition, the optical fibre 224 has a first end arranged in connection with the pulse emitting point 234 and a second end which is connected to the measurement point 214. In addition, the optical fibre 226 has a first end arranged in connection with the pulse emitting point 236 and a second end which is connected to the measurement point 216.

[0111] FIG. 2 also depicts the spectrograph 114 associated with the detector 116, the controller 120, the pulsed laser source 104 and the optical splitter 106. The controller can be used to synchronize the time-gated detector, for example SPAD matrix, to activate the detector between each measurement pulse and capture the collected signal from each measurement points separately. FIG. 3 is a schematic diagram of the system of FIG. 1 in accordance with another embodiment of the present disclosure. In FIG. 3, the excitation optical component 108 comprises a plurality of optical fibres 302, 304, 306 of which each is associated with the sample 102. More specifically, the optical fibre 302 has a first end which is connected to the optical splitter 106 and a second end which is connected to the measurement point 212 of the sample 102. The optical fibre 304 has a first end connected to the optical splitter 106 and a second end is connected to the measurement point 214. In addition, the optical fibre 306 has a first end connected the optical splitter 106 and a second end is connected to the measurement point 216.

[0112] FIG. 3 also depicts the collection optical component 110 having a plurality of optical fibres 322, 324, 326. In the collection optical component 110, the optical fibre 322 has a first end which is connected to the pulse emitting point 232 and a second end which is connected to the measurement point 212. The optical fibre 324 has a first end connected to the pulse emitting point 234 and a second end connected to the measurement point 214. In addition, the optical fibre 326 has a first end connected to the pulse emitting point 236 and a second end connected to the measurement point 216. Each of the plurality of optical fibres 322, 324, 326 is configured to have a length difference relative to other fibres 322, 324, 326 in the collection optical component to cause time delay of the predetermined time-period, while receiving the plurality of Raman scattered laser light pulse trains from the sample 102. The length differences are illustrated by the loops arranged in the fibres. The more loops the optical fibre has the longer the optical fibre is. Herein, the optical fibre 324 has three loops and the optical fibre 326 has four loops, and the optical fibre 322 has no loops. Accordingly, the optical fibre 324 is longer than the optical fibre 322 and the optical fibre 326 is longer than the optical fibre 324. The longer the optical fibre 322, 324, 326, the longer may be the time delay for the light pulses to travel from one end of the optical fibre to another end of the optical fibre. The time delay caused by the optical fibres 322, 324, 326 also causes the same time delay while emitting the Raman scattered laser light pulse trains by the plurality of pulse emitting points 232, 234, 236 of the fibre array block 112 towards the spectrograph 114.

[0113] FIG. 3 also depicts the detector 116, the controller 120, the pulsed laser source 104 and the optical splitter 106.

[0114] Referring to FIG. 4, illustrated is a schematic diagram of system-elements of the system 100 of FIGs. 2 and 3 for depicting capturing of a plurality of Raman scattered light pulsed trains, in accordance with embodiments of the present disclosure. Typically, the system-elements relate to the spectrograph 114 having a collimating lens 402, a diffraction grating 404 and a focusing lens 406. As shown, the collimating lens 402 is configured to collimate a plurality of Raman scattered light pulse trains 410 exiting the plurality of the pulse emitting points 232, 234, 236 of the fibre array block 112. Thereafter, the diffraction grating 404 is configured to disperse a plurality of collimated Raman scattered light pulse trains 412 and finally the focusing lens 406 is configured to focus a plurality of dispersed Raman light pulse trains 414 for being captured by the detector 116. As shown, the fibre array block 112 comprises 12 optical fibres in a form of a matrix 3*4, where each column (having 4 optical fibres) defines the pulse emitting points 232, 234, 236. As explained herein above, either the optical fibres 202, 204, 206 of the excitation optical component 108 (shown in FIG. 2) or the optical fibres 322, 324, 326 of the collection optical component 110 (shown in FIG. 3) are configured cause time delay of the predetermined time-period. Accordingly, the plurality of Raman scattered light pulse trains 410 exiting the pulse emitting points 232, 234, 236 are delayed when captured by the detector 116. It is to be understood that FIG. 4 depicts only light exiting from one optical fibre corresponding to the pulse emitting points 232, 234, 236. Further, the set of 4 optical fibres (belonging to a column of the fibre array block 112), each set defines the pulse emitting points 232, 234, 236, respectively, may cause collection of more light. FIG. 4 further shows a graph 450 depicting spectral intensity distribution of Raman scattered light based on the plurality of dispersed Raman light pulse trains 414 (corresponding to the plurality of Raman scattered light pulse trains 124 or measured signals) captured by the detector 116. The graph 450 depicts Time and Amplitude of the spectral intensity distributed along X and Y axis, respectively. The graph 450 also depicts an interval of a predetermined time-period, such as a time-period T1 (i.e., a delay of 40 ns) and a time-period T2 (i.e., a delay of 50 ns), to delay the plurality of Raman scattered light pulse trains for being captured by the detector 116. The spectral intensity distribution corresponding to the measured signals of the plurality of dispersed Raman light pulse trains 414 are shown with different line types (i.e., dotted, dash and centre lines). The graph 450 also depicts the spectral intensity distribution corresponding to the plurality of Raman scattered light pulse trains emitted by the pulse emitting points 232, 234, 236 and correspondingly measured by the detector 116 at different points in time (i.e., with delay of the predetermined time-period caused by either the excitation or collection optical component 108, 110). It will be evident that, the spatial offset between the pulse emitting points 232, 234, 236 would cause offsetting of the plurality of Raman scattered light pulse trains 410 exiting the fibre array block 112, which in turn cause offsetting of the plurality of dispersed Raman light pulse trains 414 exiting the focusing lens 406 and fall into different places on the detector 116. The detector 116 may be designed in such a way that different wavelength components are incident on specific regions of the detector 116. Therefore, channels within the detector 116 are calibrated to capture the spatial distribution of the different wavelengths. Calibration would involve mapping the spatial positions of the channels to the corresponding wavelengths of interest, ensuring accurate wavelength assignment for each detected signal. Accordingly, by acquiring spectra at different positions of the detector 116, it becomes possible to examine how the spectral features vary across the sample. For example, acquiring spectra at different spatial coordinates, it becomes possible to analyse the molecular composition at different locations of the sample.

[0115] Referring to FIG. 5, shown is a schematic diagram of system-elements of the system 100 of FIGs. 2 and 3 for depicting synchronized activation of a detector (such as the detector 116 of FIG. 1) for capturing the plurality of Raman scattered light pulse trains, in accordance with an embodiment of the present disclosure. Typically, FIG. 5 shows the controller 120, which is operable to synchronize the operation of the detector 116 with respect to the Raman scattered light pulse trains. Specifically, the controller 120 is operable to synchronize the operation of the detector 116, i.e., when the detector 116 should be turned ON and for what duration of time the detector 116 is turned ON, based on arrival of the Raman scattered light pulse trains to the detector 116. As shown, the plurality of Raman scattered light pulse trains corresponding to the pulse measuring points 232, 234, 236 are about to reach the detector 116 at 10ns, 50ns and 100ns, accordingly, the controller 120 is operable to synchronize the operation of the detector 116 based on a control signal shown in graph 502. The graph 502 depicts a synchronized control signal based on which the detector 116 would be operated (turned ON and OFF). Specifically, the synchronized control signal of the graph 502 indicates points in time, i.e., 10 ns, 50 ns and 100 ns along a time-axis, at which the detector 116 would be turned ON based on synched arrival of the Raman scattered light pulse trains at 10ns, 50ns and 100ns on the detector 116. The graph 502 also depicts durations of times for which the detector 116 would be turned ON, for example for 5 ns, at different points in times i.e., 10ns, 50ns and 100ns when the Raman scattered light pulse trains arrives the detector 116. Referring now to FIG. 6, illustrated is an exemplary perspective view of a fibre array block (such as the fibre array block 112) of the system of FIGs. 2 and 3, in accordance with an embodiment of the present disclosure. As shown, the fibre array block 112 includes a plurality of optical fibres 602 configured to receive and transmit the plurality of Raman scattered light pulse trains therethrough. It is to be understood that the plurality of optical fibres 602 constitute the pulse emitting points 232, 234, 236, shown in FIGs. 2 and 3, for the fibre array block 112. The plurality of optical fibres 602 are shown to be arranged in a matrix form of 9*9. Also, the plurality of optical fibres 602 are shown arranged between a pair of slabs 604. Furthermore, each of the plurality of optical fibres 602 (constituting the pulse emitting points 232, 234, 236) is shown spaced apart from an adjacent optical fibre by a predetermined distance D.

[0116] Referring to FIG. 7, illustrated is a flowchart listing steps involved in a method 700 for measuring Raman scattered light from a sample, in accordance with an embodiment of the present disclosure. At step 702, emitting an excitation laser light pulse train from a pulsed laser source. At step 704, splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains by an optical splitter. At step 706, receiving the plurality of excitation laser light pulse trains by an excitation optical component for being directed towards a plurality of measurement points in the sample, wherein each of the plurality of measurement points receives an excitation laser light pulse train from the plurality of the excitation laser light pulse trains. At step 708, receiving a plurality of Raman scattered light pulse trains by a collection optical component from the sample. At step 710, receiving the plurality of Raman scattered light pulse trains by a fibre array block from the collection optical component, the fibre array block comprises a plurality of pulse emitting points. At step 712, emitting the plurality of Raman scattered light pulse trains by the plurality of pulse emitting points towards a spectrograph in a spatially offset manner. At step 714, capturing the plurality of Raman scattered light pulse trains from the spectrograph by a detector at an interval of a predetermined time-period. The method further comprises delaying one of: the plurality of excitation laser light pulse trains to be received at the plurality of measurement points of the sample via the excitation optical component, wherein each of the plurality of excitation laser light pulse trains is delayed by the predetermined time-period for being incident on the sample at the interval of the predetermined time-period, or the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points of the fibre array block via the collection optical component, wherein each of the plurality of Raman scattered light pulse trains is delayed by the predetermined time-period for being captured by the detector at the interval of the predetermined timeperiod.

[0117] Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a nonexclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

Claims

CLAIMS1. A method for measuring Raman scattered light from a sample (102), the method comprising:- emitting an excitation laser light pulse train from a pulsed laser source (104);- splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains (122) by an optical splitter (106);- receiving the plurality of excitation laser light pulse trains by an excitation optical component (108) for being directed towards a plurality of measurement points (212, 214, 216) in the sample, wherein each of the plurality of measurement points receives a respective excitation laser light pulse train from the plurality of the excitation laser light pulse trains;- receiving a plurality of Raman scattered light pulse trains (124) by a collection optical component (110) from the sample;- receiving the plurality of Raman scattered light pulse trains by a fibre array block (112) from the collection optical component, the fibre array block comprising a plurality of pulse emitting points (232, 234, 236);- emitting the plurality of Raman scattered light pulse trains by the plurality of pulse emitting points towards a spectrograph (114) in a spatially offset manner; and- capturing the plurality of Raman scattered light pulse trains from the spectrograph by a detector (116) during an interval of a predetermined time-period (Tl, T2);- wherein the method further comprises delaying one of:- the plurality of excitation laser light pulse trains to be received at the plurality of measurement points of the sample via the excitation optical component, wherein each of the plurality of excitation laser light pulse trains is delayed by a predetermined time-period for each of the plurality of excitation laser light pulse trains, for being incident on the sample at the interval of the predetermined timeperiod, or- the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points of the fibre array block via the collection optical component, wherein each of the plurality of Raman scattered light pulse trains is delayed by a predetermined time-period for each of the plurality of the Raman scattered light pulse trains, for being captured by the detector at the interval of the predetermined time-period.

2. A method according to claim 1, further comprising arranging the plurality of pulse emitting points (232, 234, 236) of the fibre array block (112) in the spatially offset manner by a predetermined distance (D).

3. A method according to claim 2, further comprising capturing the plurality of Raman scattered light pulse trains from the spectrograph (114) by a predefined area of the detector (116).

4. A method according to claim 3, further comprising calibrating signals measured, by the predefined area of the detector (116), corresponding to the plurality of Raman scattered light pulse trains captured from the spectrograph (114).

5. A method according to any of the preceding claims, wherein the intervals of the predetermined time-period (Tl, T2) are in a range of 5 to 500 nanoseconds.

6. A method according to any of the preceding claims, wherein the spectrograph (114) is configured to:- collimate the plurality of Raman scattered light pulse trains (410) received from the plurality of the pulse emitting points (232, 234, 236),- disperse the plurality of collimated Raman scattered light pulse trains (412), and- focus the plurality of dispersed Raman light pulse trains (414) for being directed towards the detector (116).

7. A method according to any of the preceding claims, further comprising synchronizing activation of the detector (116) based on the interval of the predetermined time-period (Tl, T2).

8. A system (100) for measuring Raman scattered light from a sample (102), the system comprising:- a pulsed laser source (104) for emitting an excitation laser light pulse train;- an optical splitter (106) for splitting the excitation laser light pulse train into a plurality of excitation laser light pulse trains (122);- an excitation optical component (108) for receiving and directing the plurality of excitation laser light pulse trains towards a plurality of measurement points (212, 214, 216) in the sample, wherein each of the plurality of measurement points receives a respective excitation laser light pulse train from the plurality of the excitation laser light pulse trains;- a collection optical component (110) for receiving a plurality of Raman scattered light pulse trains (124) from the sample;- a fibre array block (112) for receiving the plurality of Raman scattered light pulse trains from the collection optical component, wherein the fibre array block comprises a plurality of the pulse emitting points (232, 234, 236);- a spectrograph (114) for receiving the plurality of Raman scattered light pulse trains emitted by the plurality of pulse emitting points in a spatially offset manner; and- a detector (116) for capturing the plurality of Raman scattered light pulse trains from the spectrograph during an interval of a predetermined time-period (Tl, T2);- wherein one of the excitation optical component and the collection optical component is configured to delay:- the plurality of excitation laser light pulse trains to be received at the plurality of measurement points by the predetermined timeperiod for each of the plurality of excitation laser light pulse trains, for being incident on the sample at the interval of the predetermined time-period, or- the plurality of Raman scattered light pulse trains to be emitted by the plurality of pulse emitting points by a predetermined timeperiod for each of the plurality of the Raman scattered light pulse trains, for being captured by the detector at the interval of the predetermined time-period, respectively.

9. A system according to claim 8, wherein each of the excitation optical component (108) and the collection optical component (110) comprises a plurality of optical fibres (202-206, 222-226 or 302-306, 322-326), and wherein each of the plurality of optical fibres of one of the excitation optical component and the collection optical component is configured to have a length difference to cause time delay of the predetermined timeperiod.

10. A system according to claim 9, wherein the length difference is in a range of 1 to 100 meters.

11. A system according to claim 8, wherein the plurality of pulse emitting points (232, 234, 236) of the fibre array block (112) is arranged in the spatially offset manner to form an array, and each of the plurality of pulse emitting points is spaced apart from an adjacent pulse emitting point by a predetermined distance (D).

12. A system according to claim 11, wherein the predetermined distance (D) is in a range of 10 to 1000 micrometres.

13. A system according to any of the claims 8 to 12, further comprising a controller (120) operatively coupled to the pulsed laser source (104) and the detector (116), wherein the controller is operable to synchronize activation of the detector based on the interval of the predetermined time-period.

Images