System and method for measuring consistent optical spectrum

Abstract

Disclosed is a system (100) for measuring consistent optical spectrum. The system comprising laser source (102) configured to emit laser light (104) towards sample (106), wherein sample interacts with laser light to emit light (108, 204); collection optical component (110) configured to receive light emitted from sample; optical mixing assembly (112, 200) configured to receive light having spatially and angularly non-uniform distribution from collection optical component, to convert light having spatially and angularly non-uniform distribution to beam of light (114, 218) having spatially and angularly uniform distribution; spectrograph (116) configured to receive and disperse beam of light; and detector unit (118) configured to receive dispersed beam of light (120) to measure consistent optical spectrum corresponding to spatially and angularly uniform distribution of dispersed beam of light.

Description

[0001] SYSTEM AND METHOD FOR. MEASURING CONSISTENT OPTICAL

[0002] SPECTRUM

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to systems for measuring consistent optical spectrums. Moreover, the present disclosure relates to methods for measuring consistent optical spectrums.

[0005] BACKGROUND

[0006] Conventionally, in spectroscopy if light signals received by a detector remains uniformly distributed with respect to its angular and spatial distributions, the spectrograph relies on a relatively simple calibration of the detector response. However, in practice an optical sampling of signals, for example, Raman and fluorescence signals from a sample often entails variation in the spatial and angular distributions of the light signals that are collected from the sample. Such variation can be caused by mechanical changes of a focus distance, or changes in an absorption or elastic scattering coefficient of the sample itself. For example, if a measurement probe is immersed in a liquid, the effective depth from where the light signals originate may decrease with an increase in turbidity (elastic scattering and absorption) of the liquid.

[0007] The variations in the spatial and angular distributions of the light signals collected from the sample causes an inconsistency in spectral and temporal responses of the spectrograph that are measured at the detector. Subsequently, the inconsistency in the spectral and temporal responses of the spectrograph causes a major challenge in a response calibration of the spectrograph since, a conventional reference calibration would cause systematic error and inconsistency in the measured optical spectrum. In some present solutions, simple remedy to the angular sensitivity is to minimize the size of the spectrograph aperture to reduce the variations in the angular distribution. However, this also minimizes an optical signal, which is contrary to a requirement in the spectrograph that an optical throughput of the spectrograph should be maximized.

[0008] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks.

[0009] SUMMARY

[0010] The aim of the present disclosure is to provide a system and a method to remove inconsistency in measurement of an optical spectrum. The aim of the present disclosure is achieved by a system or a method for measuring consistent optical spectrum as defined in the appended independent claims to which reference is made to. Advantageous features are set out in the appended dependent claims.

[0011] Throughout the description and claims of this specification, the words "comprise" , "include", "have", and "contain" and variations of these words, for example "comprising" and "comprises", mean "including but not limited to", and do not exclude other components, items, integers or steps not explicitly disclosed also to be present. Moreover, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic illustration of a system for measuring consistent optical spectrum, in accordance with an embodiment of the present disclosure; FIG. 2 is a schematic illustration of an optical mixing assembly, in accordance with an embodiment of the present disclosure; and

[0014] FIG. 3 is an illustration of a flowchart depicting steps of a method for measuring consistent optical spectrum, in accordance with an embodiment of the present disclosure.

[0015] DETAILED DESCRIPTION OF EMBODIMENTS

[0016] 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.

[0017] In a first aspect, the present disclosure provides a system for measuring consistent optical spectrum, the system comprising: a laser source configured to emit a laser light towards a sample, wherein the sample interacts with the laser light to emit a light; a collection optical component configured to receive the light emitted from the sample; an optical mixing assembly configured to receive the light having a spatially and angularly non-uniform distribution from the collection optical component, to convert the light having the spatially and angularly non-uniform distribution to a beam of light having a spatially and angularly uniform distribution; a spectrograph configured to receive and disperse the beam of light; and a detector unit configured to receive the dispersed beam of light to measure the consistent optical spectrum corresponding to the spatially and angularly uniform distribution of the dispersed beam of light. The present disclosure provides an aforementioned system. The system is able to effectively make spatial and angular distribution in the beam of light to be uniform. Thus, spectral and temporal responses of the spectrograph become consistent which reduces an unreliability of the instrument response calibration. Therefore, the system is able to significantly improve a consistency in the optical spectrum that is measured by the detector unit, despite of the light collected from the sample having the spatially and angularly non-uniform distribution. Moreover, the system improves a stability of an imaging point-spread function in the spectrograph, due to the dispersed beam of light having spatially uniform distribution.

[0018] In a second aspect, the present disclosure provides a method for measuring consistent optical spectrum, the method comprising: emitting a laser light towards a sample, wherein the sample interacts with the laser light and emits a light; receiving, via a collection optical component, the light emitted from the sample; receiving the light having a spatially and angularly non-uniform distribution from the collection optical component at an optical mixing assembly for converting the light having the spatially and angularly non- uniform distribution to a beam of light having a spatially and angularly uniform distribution; receiving and dispersing the beam of light, via a spectrograph; and receiving the dispersed beam of light, at a detector unit for measuring the consistent optical spectrum corresponding to the spatially and angularly uniform distribution of the dispersed beam of light.

[0019] The present disclosure provides an aforementioned method. The method is able to effectively make spatial and angular distribution in the beam of light to be uniform. Thus, spectral and temporal responses of the spectrograph become consistent which reduces an unreliability of the instrument response calibration. Therefore, the method is able to significantly improve a consistency in the optical spectrum that is measured by the detector unit, despite of the light collected from the sample having the spatially and angularly non-uniform distribution. Moreover, the method improves a stability of an imaging point-spread function in the spectrograph, due to the dispersed beam of light having spatially uniform distribution.

[0020] Throughout the present disclosure, the term "consistent optical spectrum" refers to a same wavelength distribution being measured at the detector unit for dispersed beam of light that is received by the detector unit, irrespective of the dispersed beam of light being associated with the light collected from the sample having the spatially and angular non-uniform distribution. Notably, measuring consistent optical spectrum relates to non-uniformity in the spatial and angular distribution of the light collected from the sample having no significant impact on the optical spectrum that is measured by the detector unit.

[0021] The method comprises the laser source configured to emit the laser light towards the sample, wherein the sample interacts with the laser light to emit the light. Throughout the present disclosure, the term "laser light" refers to a coherent and monochromatic form of light that interacts with the sample. The laser light can be emitted at specific wavelengths which enables to target particular vibrational modes in molecules of the sample which allows precise analysis of the sample's chemical composition and structure. Notably, the laser light is emitted by the laser source towards the sample. Optionally, the laser source is implemented as a monochromatic source of light to generate the laser light. The laser source is employed to emit the laser light preferably in one of: an ultraviolet range, a visible range or a near-infrared range of an electromagnetic spectrum of light. Furthermore, examples of the laser source may be a diode laser, a solid-state laser, and the like. Optionally, the laser source is one of: a pulsed laser source, a continuous-wave laser source. Throughout the present disclosure, the term "pulsed laser source" refers to that laser source that emits a series of short pulses of laser light. Optionally, in the pulsed laser source, the laser light is generated in brief bursts, typically lasting from a few picoseconds to a few nanoseconds. Throughout the present disclosure, the term "continuous-wave laser source" refers to that laser source that emits a continuous and uninterrupted beam of laser light. Notably, the continuous emission of the laser light from the continuous-wave laser source enables to maintain a constant intensity and wavelength of the laser light over a period of time.

[0022] Notably, the interaction of the sample with the laser light relates to a phenomenon of the laser light interacting with the molecules of the sample. Optionally, the interaction of the sample with the laser light is including but not limited to Raman scattering and fluorescence emission. Subsequently, the interaction of the sample with the laser light causes the molecules of the sample to undergo vibrational, rotational, or electronic changes and as a result, the light is emitted from the sample. Notably, the light consists of photons that are emitted from the sample due to the vibrational, rotational, or electronic changes in the molecules of the sample, where the emitted photons carry information about the vibrational, rotational, or electronic changes.

[0023] Moreover, the method comprises the collection optical component configured to receive the light from the sample. Throughout the present disclosure, the term "collection optical component" refers to a component that comprises at least one optical fiber that receives the light emitted from the sample. The term collection optical component may also refer to a free-space collection optics, i.e., a component without fiber optics (at least one optical fiber), configured to provide a free-space optical path for the light, e.g., in a microscope setup. Optionally, the collection optical component is including but not limited to lenses, mirrors, optical fibers, and the like. Herein, mechanical changes in a focus distance of the collection optical component or changes in optical properties (for example, absorption and scattering coefficients) of the sample cause variations in spatial and angular distribution of the light collected by the collection optical component. Thus, the light that is collected by the collection optical component is having the spatially and angularly non- uniform distribution. Notably, the at least one optical fiber present in the collection optical component, or a free space-optical path, acts as optical channels to allow the light to pass therethrough and to be received by the optical mixing assembly.

[0024] Furthermore, the method comprises an optical mixing assembly configured to receive the light having the spatially and angularly non- uniform distribution from the collection optical component, to convert the light having the spatially and angularly non-uniform distribution to a beam of light having a spatially and angularly uniform distribution. Throughout the present disclosure, the term "spatially and angularly non- uniform distribution" refers to both a spatial distribution and an angular distribution of the light being non-uniform. Notably, for the spatially non- uniform distribution, the light is not uniformly distributed across a space that is occupied by the light (i.e., a particular area of the light is more illuminated in comparison to another area). Notably, for the angularly non-uniform distribution, the light is not uniformly distributed at all different directions within its spread (i.e., the light is more intense in a particular direction in comparison to another direction). It will be appreciated that for the light having the spatially and angularly non- uniform distribution which is collected from the sample is not uniformly distributed across the space occupied by the light and not uniformly distributed at all the different directions within its spread. Throughout the present disclosure, the term "optical mixing assembly" refers to an assembly of optical components arranged in a specific manner which causes the light having the spatially and angularly non-uniform distribution to convert into the beam of light having the spatially and angularly uniform distribution. Throughout the present disclosure, the term "spatially and angularly uniform distribution" refers to both a spatial distribution and an angular distribution of the beam of light being uniform. Notably, for the spatially uniform distribution, the beam of light is uniformly distributed across a space that is occupied by the beam of light. Notably, for the angularly uniform distribution, the beam of light is uniformly distributed at all different directions within its spread. It will be appreciated that for the beam of light having the spatially and angularly uniform distribution that is transmitted from the optical mixing assembly, the beam of light is uniformly distributed across the space occupied by the light the beam spread outs and uniformly distributed at all the different directions within the spread.

[0025] Optionally, the optical mixing assembly comprises: a first optical fiber, wherein the first optical fiber is configured to convert the light to a first intermediate beam of light having a spatially uniform and angularly non-uniform distribution; at least one optical angular converter configured to receive the first intermediate beam of light to convert the first intermediate beam of light to a second intermediate beam of light having a spatially non-uniform and angularly uniform distribution; and a second optical fiber, configured to receive the second intermediate beam of light to convert the second intermediate beam of light to the beam of light having the spatially and angularly uniform distribution.

[0026] In this regard, the term "first optical fiber" refers to that optical fiber which receives the light having the spatially and angularly non-uniform distribution and subsequently, mixes the spatially non-uniform distribution to spatially uniform distribution as the light passes through the first optical fiber. Therefore, the first intermediate beam of light at the exit pupil of the first optical fiber has the spatially uniform and angularly non-uniform distribution. Throughout the present disclosure, the term "first intermediate beam of light" refers to that beam of light that is transmitted from the first optical fiber. Notably, as the light enters the first optical fiber, the light undergoes multiple internal reflections along the length of the first optical fiber which causes a mixing of the spatially non-uniform distribution of the light. Subsequently, the mixing of the spatially non-uniform distribution of the light changes the spatially non-uniform distribution to the spatially uniform distribution, while the angularly non-uniform distribution of the light remains same. Thus, the first intermediate beam of light that is transmitted from the first optical fiber has a spatially uniform and angularly non-uniform distribution. Throughout the present disclosure, the term "spatially uniform and angularly non-uniform distribution" refers to a spatial distribution of the first intermediate beam of light being uniform and an angular distribution of the first intermediate beam of light being non-uniform. It will be appreciated that for the first intermediate beam of light having the spatially uniform and angularly non-uniform distribution that is transmitted from the first optical fiber, the first intermediate beam of light is uniformly distributed across the space occupied by the light and non- uniformly distributed at all the different directions within its spread.

[0027] Throughout the present disclosure, the term "optical angular converter" refers to that optical component which transforms the spatially uniform distribution of the first intermediate beam of light that is received by the optical angular converter, to angularly uniform distribution of the second intermediate beam of light. Moreover, the spatially uniform distribution of the first intermediate beam of light gets converted to the spatially non- uniform distribution, while passing through the at least one optical angular converter. Subsequently, the second intermediate beam of light that is transmitted from the at least one optical angular converter has the spatially non-uniform and angularly uniform distribution. It will be appreciated that the term "at least one optical angular converter" refers to "one optical angular converter" in some implementations, and "a plurality of optical angular converters" in other implementations. Throughout the present disclosure, the term "spatially non-uniform and angularly uniform distribution" refers to a spatial distribution of the second intermediate beam of light being non-uniform and an angular distribution of the second intermediate beam of light being uniform. It will be appreciated that for the second intermediate beam of light having the spatially non-uniform and angularly uniform distribution that is transmitted from the at least one optical angular converter, the second intermediate beam of light is non-uniformly distributed across the space occupied by the light and uniformly distributed at all the different directions within its spread.

[0028] Throughout the present disclosure, the term "second optical fiber" refers to that optical fiber which receives the second intermediate beam of light having the spatially non-uniform and angularly uniform distribution and subsequently, mixes the spatially non-uniform distribution to spatially uniform distribution as the second intermediate beam of light passes through the second optical fiber. Therefore, the beam of light at the exit pupil of the second optical fiber has the spatially and angularly uniform distribution. Throughout the present disclosure, the term "second intermediate beam of light" refers to that beam of light that is transmitted from the second optical fiber. Notably, as the second intermediate beam of light enters the second optical fiber, the second intermediate beam of light undergoes multiple internal reflections along a length of the second optical fiber which causes a mixing of the spatially non-uniform distribution of the second intermediate beam of light. Subsequently, the mixing of the spatially non-uniform distribution of the second intermediate beam of light changes the spatially non-uniform distribution to the spatially uniform distribution, while the angularly uniform distribution of the light remains the same. Thus, the beam of light that is transmitted from the second optical fiber has a spatially and angularly uniform distribution. A technical effect of the optical mixing assembly comprising: the first optical fiber, the optical angular converter, and the second optical fiber is that the spatial and angular distribution of the beam of light is effectively made uniform via the optical mixing assembly.

[0029] Optionally, the first optical fiber and the second optical fiber are configured to have one of: a helical structure having one or more loops, a linear structure, a non-linear structure. Throughout the present disclosure, the term "helical structure" refers to a spiral like structure in which the one or more loops are present. Notably, in the helical structure the first optical fiber and the second optical fiber are respectively, designed in form of a continuous curve that winds around their corresponding central axis, which causes the first optical fiber and the second optical fiber to have one or more loops. Optionally, a number of the one or more loops in first optical fiber may be equal to or different from the number of one or more loops in the second optical fiber. Throughout the present disclosure, the term "linear structure" refers to that structure in which the first optical fiber and the second optical fiber, respectively, resembles a straight line without curving or bending. Throughout the present disclosure, the term "non-linear structure" refers to that structure in which one or more curves or bends are present along a length of the first optical fiber and the second optical fiber, respectively. A technical effect of the first optical fiber and the second optical fiber being configured to have the helical structure having the one or more loops is that the length of the first optical fiber and the second optical fiber, respectively, increases and the optical paths curve which enables to increase an efficiency of the spatial mixing of the light in the first optical fiber and the second intermediate beam of light in the second optical fiber by having more total internal reflections in the first optical fiber and the second optical fiber over increased lengths and curved optical paths of the first optical fiber and the second optical fiber.

[0030] Optionally, a core of the first optical fiber and the second optical fiber is selected to have one of: a circular core, a polygonal core, wherein the polygonal core is preferably an octagonal core. Throughout the present disclosure, the term "core" refers to a central or cross-sectional region of any optical fiber through which any light passes therethrough. Optionally, the core of the first optical fiber may be either different or same as the core of the second optical fiber. Throughout the present disclosure, the term "circular core" refers to the core being designed to have a circular shaped cross-sectional region. Throughout the present disclosure, the term "polygonal core" refers to the core being designed to have a polygon (for example a pentagon, a hexagon, an octagon, and the like) shaped cross-sectional region. Optionally, the polygonal core may preferably be the octagonal core, i.e., the core is designed to have an octagonal shaped cross-sectional region. A technical effect of the first optical fiber and the second optical fiber being selected to have the octagonal core is that the octagonal core optimizes the total internal reflections inside the first optical fiber and the second optical fiber.

[0031] Optionally, the at least one optical angular converter comprises a lens arrangement comprising at least one lens that converts the first intermediate beam of light having the angularly non-uniform distribution to the second intermediate beam of light having the angularly uniform distribution, wherein the lens is arranged between the first optical fiber and the second optical fiber. Optionally, the at least one lens comprises at least one of: a plano-convex lens, a bi-convex lens, a molded aspheric lens. Throughout the present disclosure, the term "lens arrangement" refers to an arrangement of the at least one lens that transforms the spatially uniform distribution of the first intermediate beam of light into the angular uniform distribution of the second intermediate beam of light as the first intermediate beam of light passes through the at least one lens in the lens arrangement, and thus, the first intermediate beam of light gets uniformly distributed in all directions within its spread. Subsequently, the second intermediate beam of light that is transmitted from the lens arrangement is having the angularly uniform distribution. It will be appreciated that the term "at least one lens" refers to "one lens" in some implementations, "a pair of lenses" in other implementations, and "a plurality of lenses" in yet other implementations. A technical effect of the at least one optical angular converter comprising the lens arrangement is that the first intermediate beam of light having the angularly non-uniform distribution are effectively converted to the second intermediate beam of light having the angularly uniform distribution using the at least one lens that are easily available.

[0032] Furthermore, the method comprises the spectrograph configured to receive and disperse the beam of light. Throughout the present disclosure, the term "spectrograph" refers to a device that is configured to analyse the spectral properties of any light. Notably, the spectrograph works by dispersing any light into wavelength components and then measuring intensity of that light at each of the wavelength component by the detector unit. Herein the spectrograph is used to disperse the beam of light towards the detector unit. Optionally, the spectrograph may include a collimating lens for collimating the received beam of light, a diffraction grating for dispersing the collimated beam of light and a focusing lens for focusing the dispersed light on the detector unit. Notably, dispersion of the beam of light refers to a process where the beam of light is separated or spread out into various wavelengths by using a dispersive element. The dispersive element may include but not limited to a prism or a diffraction grating. It will be appreciated that since the beam of light that is received by the spectrograph is having spatially and angularly uniform distribution, then the dispersed beam of light also has the spatially and angularly uniform distribution. Notably, in a grating spectrograph with a time-resolved measurement, a temporal distribution of the received beam of light is broadened by an effect of pulse front tilt which is well-known in the art, in which the temporal broadening of the received beam of light depends on the angular distribution of the received beam of light. Thus, it is crucial that the beam of light that is received by the spectrograph is having angularly uniform distribution for temporal instrument response calibrations to be reliable in order to measure the consistent optical spectrum.

[0033] Furthermore, the method comprises the detector unit configured to receive the dispersed beam of light for measuring the consistent optical spectrum corresponding to the spatially and angularly uniform distribution of the dispersed beam of light. Throughout the present disclosure, the term "detector unit" refers to a device that is configured for measuring the consistent optical spectrum associated with the dispersed beam of light to gather information related to vibrational, rotational, or electronic changes in the sample. It will be appreciated that since the dispersed beam of light is having the spatially and angularly uniform distribution, a response calibration of the detector unit becomes reliable which causes the optical spectrum that is measured at the detector unit to be consistent, despite the light that is collected from the sample having the spatially and angularly non-uniform distribution.

[0034] Optionally, the detector unit comprises Single Photon Avalanche Diodes (SPADs) comprising at least one pixel. Throughout the present disclosure, the term "Single Photon Avalanche Diodes (SPADs)" refers to a type of semiconductors that can detect even very low level of light signals. It will be appreciated that the SPADs are well-known in the art. Notably, in some implementations, the detector unit comprises one SPAD pixel and in other implementations, the detector unit comprises a plurality of SPAD pixels. Notably, a single SPAD pixel in the detector unit may comprise a single or a plurality of individual SPAD elements. It is known that the photon detection probability of a single SPAD element in a SPAD pixel varies and thus, it is crucial that the dispersed beam of light is having spatially uniform distribution for the detector response calibration to be reliable in order to measure the consistent optical spectrum. A technical effect of using the SPADs is that the SPADs can digitally detect even single photons, which inherently gets rid of the read-out noise of analog pixels.

[0035] Optionally, the detector unit comprises the SPADs and timing electronics for time-resolved operation of the detector unit. Throughout the present disclosure, the term "timing electronics" refers to those electronic components that measure a time-of-arrival of photons in the dispersed beam of light received by the detector unit according to the time-resolved operation of the detector unit. Throughout the present disclosure, the term "time-resolved operation" refers to a measurement in which a light source, such as a pulsed laser, is used to illuminate the sample, and the detector unit is synchronized with the light source to measure the time- of-arrival of the photons in the dispersed beam of light received by the detector unit. A technical effect of the time-resolved operation is that the time-resolved operation enables to capture time-gated Raman spectrum or time-resolved fluorescence spectrum of the sample. It will be appreciated that the SPADs and the timing electronics needed for the time-resolved measurement can be fabricated as an integrated circuit. Optionally, the timing electronics and the SPADs are fabricated in a CMOS technology. Throughout the present disclosure, the term "Complementary Metal-Oxide Semiconductor (CMOS)" refers to a process technology used for the fabrication and manufacturing of integrated circuits. It will be appreciated that the CMOS technology is well-known in the art. Optionally, fabricating the SPADs in the CMOS technology, may form an optical stack on top of a photon-sensitive area of a given SPAD element. The optical stack acts as an optical filter, whose transmission depends on both a wavelength and an angle of incidence of the dispersed beam of light received by the given SPAD element in the detector unit. Thus, the dispersed beam of light received by the detector unit having the angularly uniform distribution makes the response calibration of the detector unit reliable, which enables to measure the consistent optical spectrum. A technical effect of the SPADs and the timing electronics being fabricated as an integrated circuit is that the SPADs and the timing electronics fabricated as an integrated circuit have a lower design complexity and a smaller size in comparison to, for example, time-gated Charge Coupled Device (CCD).

[0036] The present disclosure comprises aforementioned system for measuring consistent optical spectrum with an optical configuration that is to be placed, or is arranged, in the optical path between the collection optical component (e.g. a measurement probe) and the spectrograph. The optical configuration comprises an optical mixing assembly, for example, a mode scrambler (also known as mode mixer). The optical configuration has the following properties. It approximately retains the optical etendue, so that the full aperture of the spectrograph can be used. It also retains the spectral and temporal characteristics of the collected signal to a high degree. What it does is that it scrambles both the spatial and angular distributions of the collected signal so that they uniformly fill the etendue of the spectrograph. This uniformization does not incur losses dependent on the input angular or spatial distributions. Crucially, the detector always receives the same, uniform angular and spatial distribution independent of the spatial and angular distribution collected from the sample. This stabilizes the total time-integrated signal, namely the detector photon detection efficiency (PDE), and the shape of the temporal instrument response function at each pixel enabling reliable instrument calibrations to measure the consistent optical spectrum, as explained in the previous paragraphs. The present disclosure also relates to the method as described above. Various embodiments and variants disclosed above, with respect to the aforementioned system, apply mutatis mutandis to the method.

[0037] Optionally, the step of converting the light having the spatially and angularly non-uniform distribution to the beam of light having the spatially and angularly uniform distribution comprises: converting the light to a first intermediate beam of light having a spatially uniform and angularly non-uniform distribution, via a first optical fiber; receiving the first intermediate beam of light for converting the first intermediate beam of light to a second intermediate beam of light having a spatially non-uniform and angularly uniform distribution, via at least one optical angular converter; and receiving the second intermediate beam of light for converting the second intermediate beam of light to the beam of light having the spatially and angularly uniform distribution, via a second optical fiber.

[0038] Optionally, the first optical fiber and the second optical fiber are configured to have one of: a helical structure having one or more loops, a linear structure, a non-linear structure.

[0039] Optionally, a core of the first optical fiber and the second optical fiber is selected to have one of: a circular core, a polygonal core, wherein the polygonal core is preferably an octagonal core.

[0040] Optionally, the at least one optical angular converter comprises a lens arrangement comprising at least one lens that converts the first intermediate beam of light having the angularly non-uniform distribution to the second intermediate beam of light having the angularly uniform distribution, wherein the lens is arranged between the first optical fiber and the second optical fiber. Optionally, the detector unit comprises Single Photon Avalanche Diode (SPADs) comprising at least one pixel.

[0041] Optionally, the detector unit comprises the SPADs and timing electronics for time-resolved operation of the detector unit, fabricated as an integrated circuit.

[0042] DETAILED DESCRIPTION OF THE DRAWINGS

[0043] Referring to FIG. 1, illustrated is a schematic illustration of a system 100 for measuring consistent optical spectrum, in accordance with an embodiment of the present disclosure. As shown, the system 100 comprises a laser source 102 configured to emit a laser light 104 towards a sample 106, wherein the sample 106 interacts with the laser light 104 to emit a light 108. Moreover, the system 100 comprises a collection optical component 110 configured to receive the light 108 emitted from the sample 106. Furthermore, the system 100 comprises an optical mixing assembly 112 configured to receive the light 109 having a spatially and angularly non-uniform distribution from the collection optical component 110, to convert the light 109 having the spatially and angularly non-uniform distribution to a beam of light 114 having a spatially and angularly uniform distribution. Furthermore, the system 100 comprises a spectrograph 116 configured to receive and disperse the beam of light 114. Furthermore, the system 100 comprises a detector unit 118 configured to receive the dispersed beam of light 120 to measure the consistent optical spectrum corresponding to the spatially and angularly uniform distribution of the dispersed beam of light 120.

[0044] Referring to FIG. 2, illustrated is a schematic illustration of an optical mixing assembly 200, in accordance with an embodiment of the present disclosure. The optical mixing assembly shown in FIG. 2 is a more detailed illustration of the optical mixing assembly 112 of the system 100 illustrated in FIG. 1. As shown, the optical mixing assembly 200 comprises a first optical fiber 202, wherein the first optical fiber 202 is configured to convert the light 204 to a first intermediate beam of light 206 having a spatially uniform and angularly non-uniform distribution. Moreover, the optical mixing assembly 200 comprises at least one optical angular converter (depicted as an optical angular converter 208) configured to receive the first intermediate beam of light 206 to convert the first intermediate beam of light 206 to a second intermediate beam of light 210 having a spatially non-uniform and angularly uniform distribution. Optionally, the at least one optical angular converter 208 comprises a lens arrangement 212, wherein the lens arrangement 212 comprises at least one lens (depicted as the pair of lenses 214A and 214B). Furthermore, the optical mixing assembly 200 comprises a second optical fiber 216, configured to receive the second intermediate beam 210 of light to convert the second intermediate beam of light 210 to a beam of light 218 having the spatially and angularly uniform distribution.

[0045] Referring to FIG. 3, illustrated is a flowchart depicting steps of a method for measuring consistent optical spectrum. At step 302, a laser light is emitted towards a sample, wherein the sample interacts with the laser light and emits a light. At step 304, the emitted light is collected, via a collection optical component, from the sample. At step 306, the light having a spatially and angularly non-uniform distribution is received from the collection optical component at an optical mixing assembly for converting the light having the spatially and angularly non-uniform distribution to a beam of light having a spatially and angularly uniform distribution. At step 308, the beam of light is received and dispersed by a spectrograph. At step 310, the dispersed beam of light is received at a detector unit for measuring the consistent optical spectrum corresponding to the spatially and angularly uniform distribution of the dispersed beam of light. The steps 302, 304, 306, 308 and 310 are only illustrative and other alternatives can also be provided where one or more steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein. 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 non- exclusive 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 system (100) for measuring consistent optical spectrum, the system comprising: a laser source (102) configured to emit a laser light (104) towards a sample (106), wherein the sample interacts with the laser light to emit a light (108); a collection optical component (110) configured to receive the light (108) emitted from the sample; an optical mixing assembly (112, 200) configured to receive the light (109, 204) having a spatially and angularly non-uniform distribution from the collection optical component, and to convert the light to a beam of light (114, 218) having a spatially and angularly uniform distribution; a spectrograph (116) configured to receive and disperse the beam of light; and a detector unit (118) configured to receive the dispersed beam of light (120) to measure the consistent optical spectrum corresponding to the spatially and angularly uniform distribution of the dispersed beam of light.

2. The system (100) according to claim 1, wherein the optical mixing assembly (112, 200) comprises: a first optical fiber (202), wherein the first optical fiber is configured to convert the light (109, 204) to a first intermediate beam of light (206) having a spatially uniform and angularly non-uniform distribution; at least one optical angular converter (208) configured to receive the first intermediate beam of light (206) to convert the first intermediate beam of light to a second intermediate beam of light (210) having a spatially non-uniform and angularly uniform distribution; and a second optical fiber (216), configured to receive the second intermediate beam of light to convert the second intermediate beam oflight to the beam of light (114, 218) having the spatially and angularly uniform distribution.

3. The system (100) according to claim 2, wherein the first optical fiber (202) and the second optical fiber (216) are configured to have one of: a helical structure having one or more loops, a linear structure, a non-linear structure.

4. The system (100) according to claim 2 or 3, wherein a core of the first optical fiber (202) and the second optical fiber (216) is selected to have one of: a circular core, a polygonal core, wherein the polygonal core is preferably an octagonal core.

5. The system (100) according to any of the claims 2-4, wherein the at least one optical angular converter (208) comprises a lens arrangement (212) comprising at least one lens (214A-B) that converts the first intermediate beam of light (206) having the angularly non-uniform distribution to the second intermediate beam of light (210) having the angularly uniform distribution, wherein the lens is arranged between the first optical fiber (202) and the second optical fiber (216).

6. The system (100) according to any of the preceding claims, wherein the laser source is one of: a pulsed laser source, a continuous-wave laser source.

7. The system (100) according to any of the preceding claims, wherein the detector unit (118) comprises Single Photon Avalanche Diodes (SPADs) comprising at least one pixel.

8. The system (100) according to claim 7, wherein the detector unit comprises the SPADs and timing electronics for time-resolved operation of the detector unit, fabricated as an integrated circuit.

9. A method for measuring consistent optical spectrum, the method comprising: emitting a laser light (104) towards a sample (106), wherein the sample interacts with the laser light and emits a light (108); receiving, via a collection optical component (110), the light emitted from the sample; receiving the light (109) having a spatially and angularly non- uniform distribution from the collection optical component at an optical mixing assembly (112, 200) for converting the light to a beam of light (114, 218) having a spatially and angularly uniform distribution; receiving and dispersing the beam of light, via a spectrograph (116); and receiving the dispersed beam of light (120), at a detector unit (118) for measuring the consistent optical spectrum corresponding to the spatially and angularly uniform distribution of the dispersed beam of light.

10. The method according to claim 9, wherein the step of converting the light (109, 204) having the spatially and angularly non-uniform distribution to the beam of light (114, 218) having the spatially and angularly uniform distribution comprises: converting the light to a first intermediate beam of light (206) having a spatially uniform and angularly non-uniform distribution, via a first optical fiber (202); receiving the first intermediate beam of light for converting the first intermediate beam of light to a second intermediate beam of light (210) having a spatially non-uniform and angularly uniform distribution, via at least one optical angular converter (208); and receiving the second intermediate beam of light for converting the second intermediate beam of light to the beam of light having the spatially and angularly uniform distribution, via a second optical fiber (216).

11. The method according to claim 10, wherein the first optical fiber (202) and the second optical fiber (216) are configured to have one of: a helical structure having one or more loops, a linear structure, a non-linear structure.

12. The method according to claim 10 or 11, wherein a core of the first optical fiber (202) and the second optical fiber (216) is selected to have one of: a circular core, a polygonal core, wherein the polygonal core is preferably an octagonal core.

13. The method according to any of the claims 10-12, wherein the at least one optical angular converter (208) comprises a lens arrangement (212) comprising at least one lens (214A-B) that converts the first intermediate beam of light (206) having the angularly non-uniform distribution to the second intermediate beam of light (210) having the angularly uniform distribution, wherein the lens is arranged between the first optical fiber (202) and the second optical fiber (216).

14. The method according to any of the claims 9-13, wherein the detector unit (118) comprises Single Photon Avalanche Diodes (SPADs) comprising at least one pixel.

15. The method according to any of the claims 9-14, wherein the detector unit comprises the SPADs and timing electronics for time-resolved operation of the detector unit, fabricated as an integrated circuit.

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